Provided by: sudo_1.9.9-1ubuntu2.4_amd64 bug

NAME

     sudo_plugin — Sudo Plugin API

DESCRIPTION

     Starting with version 1.8, sudo supports a plugin API for policy and session logging.
     Plugins may be compiled as dynamic shared objects (the default on systems that support them)
     or compiled statically into the sudo binary itself.  By default, the sudoers plugin provides
     audit, security policy and I/O logging capabilities.  Via the plugin API, sudo can be
     configured to use alternate plugins provided by third parties.  The plugins to be used are
     specified in the sudo.conf(5) file.

     The API is versioned with a major and minor number.  The minor version number is incremented
     when additions are made.  The major number is incremented when incompatible changes are
     made.  A plugin should be check the version passed to it and make sure that the major
     version matches.

     The plugin API is defined by the sudo_plugin.h header file.

   Policy plugin API
     A policy plugin must declare and populate a policy_plugin struct in the global scope.  This
     structure contains pointers to the functions that implement the sudo policy checks.  The
     name of the symbol should be specified in sudo.conf(5) along with a path to the plugin so
     that sudo can load it.

     struct policy_plugin {
     #define SUDO_POLICY_PLUGIN     1
         unsigned int type; /* always SUDO_POLICY_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t plugin_printf, char * const settings[],
             char * const user_info[], char * const user_env[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int exit_status, int error);
         int (*show_version)(int verbose);
         int (*check_policy)(int argc, char * const argv[],
             char *env_add[], char **command_info[],
             char **argv_out[], char **user_env_out[], const char **errstr);
         int (*list)(int argc, char * const argv[], int verbose,
             const char *list_user, const char **errstr);
         int (*validate)(const char **errstr);
         void (*invalidate)(int remove);
         int (*init_session)(struct passwd *pwd, char **user_env[],
             const char **errstr);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
         struct sudo_plugin_event * (*event_alloc)(void);
     };

     The policy_plugin struct has the following fields:

     type  The type field should always be set to SUDO_POLICY_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t plugin_printf, char * const settings[],
               char * const user_info[], char * const user_env[],
               char * const plugin_options[], const char **errstr);

           Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was
           a usage error.  In the latter case, sudo will print a usage message before it exits.
           If an error occurs, the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to determine the major and minor
                 version number of the plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that can be used by the plugin to
                 interact with the user (see Conversation API for details).  Returns 0 on success
                 and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used to display informational
                 or error messages (see Conversation API for details).  Returns the number of
                 characters printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.  These settings correspond to
                 options the user specified when running sudo.  As such, they will only be
                 present when the corresponding option has been specified on the command line.

                 When parsing settings, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 The following values may be set by sudo:

                 bsdauth_type=string
                       Authentication type, if specified by the -a option, to use on systems
                       where BSD authentication is supported.

                 closefrom=number
                       If specified, the user has requested via the -C option that sudo close all
                       files descriptors with a value of number or higher.  The plugin may
                       optionally pass this, or another value, back in the command_info list.

                 cmnd_chroot=string
                       The root directory (see chroot(2)) to run the command in, as specified by
                       the user via the -R option.  The plugin may ignore or restrict the user's
                       ability to specify a new root directory.  Only available starting with API
                       version 1.16.

                 cmnd_cwd=string
                       The working directory to run the command in, as specified by the user via
                       the -D option.  The plugin may ignore or restrict the user's ability to
                       specify a new working directory.  Only available starting with API version
                       1.16.

                 debug_flags=string
                       A debug file path name followed by a space and a comma-separated list of
                       debug flags that correspond to the plugin's Debug entry in sudo.conf(5),
                       if there is one.  The flags are passed to the plugin exactly as they
                       appear in sudo.conf(5).  The syntax used by sudo and the sudoers plugin is
                       subsystem@priority but a plugin is free to use a different format so long
                       as it does not include a comma (‘,’).  Prior to sudo 1.8.12, there was no
                       way to specify plugin-specific debug_flags so the value was always the
                       same as that used by the sudo front-end and did not include a path name,
                       only the flags themselves.  As of version 1.7 of the plugin interface,
                       sudo will only pass debug_flags if sudo.conf(5) contains a plugin-specific
                       Debug entry.

                 ignore_ticket=bool
                       Set to true if the user specified the -k option along with a command,
                       indicating that the user wishes to ignore any cached authentication
                       credentials.  implied_shell to true.  This allows sudo with no arguments
                       to be used similarly to su(1).  If the plugin does not to support this
                       usage, it may return a value of -2 from the check_policy() function, which
                       will cause sudo to print a usage message and exit.

                 implied_shell=bool
                       If the user does not specify a program on the command line, sudo will pass
                       the plugin the path to the user's shell and set

                 login_class=string
                       BSD login class to use when setting resource limits and nice value, if
                       specified by the -c option.

                 login_shell=bool
                       Set to true if the user specified the -i option, indicating that the user
                       wishes to run a login shell.

                 max_groups=int
                       The maximum number of groups a user may belong to.  This will only be
                       present if there is a corresponding setting in sudo.conf(5).

                 network_addrs=list
                       A space-separated list of IP network addresses and netmasks in the form
                       “addr/netmask”, e.g., “192.168.1.2/255.255.255.0”.  The address and
                       netmask pairs may be either IPv4 or IPv6, depending on what the operating
                       system supports.  If the address contains a colon (‘:’), it is an IPv6
                       address, else it is IPv4.

                 noninteractive=bool
                       Set to true if the user specified the -n option, indicating that sudo
                       should operate in non-interactive mode.  The plugin may reject a command
                       run in non-interactive mode if user interaction is required.

                 plugin_dir=string
                       The default plugin directory used by the sudo front-end.  This is the
                       default directory set at compile time and may not correspond to the
                       directory the running plugin was loaded from.  It may be used by a plugin
                       to locate support files.

                 plugin_path=string
                       The path name of plugin loaded by the sudo front-end.  The path name will
                       be a fully-qualified unless the plugin was statically compiled into sudo.

                 preserve_environment=bool
                       Set to true if the user specified the -E option, indicating that the user
                       wishes to preserve the environment.

                 preserve_groups=bool
                       Set to true if the user specified the -P option, indicating that the user
                       wishes to preserve the group vector instead of setting it based on the
                       runas user.

                 progname=string
                       The command name that sudo was run as, typically “sudo” or “sudoedit”.

                 prompt=string
                       The prompt to use when requesting a password, if specified via the -p
                       option.

                 remote_host=string
                       The name of the remote host to run the command on, if specified via the -h
                       option.  Support for running the command on a remote host is meant to be
                       implemented via a helper program that is executed in place of the user-
                       specified command.  The sudo front-end is only capable of executing
                       commands on the local host.  Only available starting with API version 1.4.

                 run_shell=bool
                       Set to true if the user specified the -s option, indicating that the user
                       wishes to run a shell.

                 runas_group=string
                       The group name or group-ID to run the command as, if specified via the -g
                       option.

                 runas_user=string
                       The user name or user-ID to run the command as, if specified via the -u
                       option.

                 selinux_role=string
                       SELinux role to use when executing the command, if specified by the -r
                       option.

                 selinux_type=string
                       SELinux type to use when executing the command, if specified by the -t
                       option.

                 set_home=bool
                       Set to true if the user specified the -H option.  If true, set the HOME
                       environment variable to the target user's home directory.

                 sudoedit=bool
                       Set to true when the -e option is specified or if invoked as sudoedit.
                       The plugin shall substitute an editor into argv in the check_policy()
                       function or return -2 with a usage error if the plugin does not support
                       sudoedit.  For more information, see the check_policy section.

                 timeout=string
                       Command timeout specified by the user via the -T option.  Not all plugins
                       support command timeouts and the ability of the user to set a timeout may
                       be restricted by policy.  The format of the timeout string is plugin-
                       specific.

                 Additional settings may be added in the future so the plugin should silently
                 ignore settings that it does not recognize.

           user_info
                 A vector of information about the user running the command in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 The following values may be set by sudo:

                 cols=int
                       The number of columns the user's terminal supports.  If there is no
                       terminal device available, a default value of 80 is used.

                 cwd=string
                       The user's current working directory.

                 egid=gid_t
                       The effective group-ID of the user invoking sudo.

                 euid=uid_t
                       The effective user-ID of the user invoking sudo.

                 gid=gid_t
                       The real group-ID of the user invoking sudo.

                 groups=list
                       The user's supplementary group list formatted as a string of comma-
                       separated group-IDs.

                 host=string
                       The local machine's hostname as returned by the gethostname(2) system
                       call.

                 lines=int
                       The number of lines the user's terminal supports.  If there is no terminal
                       device available, a default value of 24 is used.

                 pgid=int
                       The ID of the process group that the running sudo process is a member of.
                       Only available starting with API version 1.2.

                 pid=int
                       The process ID of the running sudo process.  Only available starting with
                       API version 1.2.

                 ppid=int
                       The parent process ID of the running sudo process.  Only available
                       starting with API version 1.2.

                 rlimit_as=soft,hard
                       The maximum size to which the process's address space may grow (in bytes),
                       if supported by the operating system.  The soft and hard limits are
                       separated by a comma.  A value of “infinity” indicates that there is no
                       limit.  Only available starting with API version 1.16.

                 rlimit_core=soft,hard
                       The largest size core dump file that may be created (in bytes).  The soft
                       and hard limits are separated by a comma.  A value of “infinity” indicates
                       that there is no limit.  Only available starting with API version 1.16.

                 rlimit_cpu=soft,hard
                       The maximum amount of CPU time that the process may use (in seconds).  The
                       soft and hard limits are separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available starting with API
                       version 1.16.

                 rlimit_data=soft,hard
                       The maximum size of the data segment for the process (in bytes).  The soft
                       and hard limits are separated by a comma.  A value of “infinity” indicates
                       that there is no limit.  Only available starting with API version 1.16.

                 rlimit_fsize=soft,hard
                       The largest size file that the process may create (in bytes).  The soft
                       and hard limits are separated by a comma.  A value of “infinity” indicates
                       that there is no limit.  Only available starting with API version 1.16.

                 rlimit_locks=soft,hard
                       The maximum number of locks that the process may establish, if supported
                       by the operating system.  The soft and hard limits are separated by a
                       comma.  A value of “infinity” indicates that there is no limit.  Only
                       available starting with API version 1.16.

                 rlimit_memlock=soft,hard
                       The maximum size that the process may lock in memory (in bytes), if
                       supported by the operating system.  The soft and hard limits are separated
                       by a comma.  A value of “infinity” indicates that there is no limit.  Only
                       available starting with API version 1.16.

                 rlimit_nofile=soft,hard
                       The maximum number of files that the process may have open.  The soft and
                       hard limits are separated by a comma.  A value of “infinity” indicates
                       that there is no limit.  Only available starting with API version 1.16.

                 rlimit_nproc=soft,hard
                       The maximum number of processes that the user may run simultaneously.  The
                       soft and hard limits are separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available starting with API
                       version 1.16.

                 rlimit_rss=soft,hard
                       The maximum size to which the process's resident set size may grow (in
                       bytes).  The soft and hard limits are separated by a comma.  A value of
                       “infinity” indicates that there is no limit.  Only available starting with
                       API version 1.16.

                 rlimit_stack=soft,hard
                       The maximum size to which the process's stack may grow (in bytes).  The
                       soft and hard limits are separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available starting with API
                       version 1.16.

                 sid=int
                       The session ID of the running sudo process or 0 if sudo is not part of a
                       POSIX job control session.  Only available starting with API version 1.2.

                 tcpgid=int
                       The ID of the foreground process group associated with the terminal device
                       associated with the sudo process or 0 if there is no terminal present.
                       Only available starting with API version 1.2.

                 tty=string
                       The path to the user's terminal device.  If the user has no terminal
                       device associated with the session, the value will be empty, as in “tty=”.

                 uid=uid_t
                       The real user-ID of the user invoking sudo.

                 umask=octal
                       The invoking user's file creation mask.  Only available starting with API
                       version 1.10.

                 user=string
                       The name of the user invoking sudo.

           user_env
                 The user's environment in the form of a NULL-terminated vector of “name=value”
                 strings.

                 When parsing user_env, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin path are passed as
                 arguments to the plugin.  These arguments are split on a white space boundary
                 and are passed to the plugin in the form of a NULL-terminated array of strings.
                 If no arguments were specified, plugin_options will be the NULL pointer.

                 NOTE: the plugin_options parameter is only available starting with API version
                 1.2.  A plugin must check the API version specified by the sudo front-end before
                 using plugin_options.  Failure to do so may result in a crash.

           errstr
                 If the open() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     close
           void (*close)(int exit_status, int error);

           The close() function is called when sudo is finished, shortly before it exits.
           Starting with API version 1.15, close() is called regardless of whether or not a
           command was actually executed.  This makes it possible for plugins to perform cleanup
           even when a command was not run.  It is not possible to tell whether a command was run
           based solely on the arguments passed to the close() function.  To determine if a
           command was actually run, the plugin must keep track of whether or not the
           check_policy() function returned successfully.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2) system call, or zero if no
                 command was run.  The value of exit_status is undefined if error is non-zero.

           error
                 If the command could not be executed, this is set to the value of errno set by
                 the execve(2) system call.  The plugin is responsible for displaying error
                 information via the conversation() or plugin_printf() function.  If the command
                 was successfully executed, the value of error is zero.

           If no close() function is defined, no I/O logging plugins are loaded, and neither the
           timeout not use_pty options are set in the command_info list, the sudo front-end may
           execute the command directly instead of running it as a child process.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user specifies the -V option.
           The plugin may display its version information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the user requests detailed
           version information, the verbose flag will be set.

           Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was
           a usage error, although the return value is currently ignored.

     check_policy
           int (*check_policy)(int argc, char * const argv[], char *env_add[],
               char **command_info[], char **argv_out[], char **user_env_out[],
               const char **errstr);

           The check_policy() function is called by sudo to determine whether the user is allowed
           to run the specified commands.

           If the sudoedit option was enabled in the settings array passed to the open()
           function, the user has requested sudoedit mode.  sudoedit is a mechanism for editing
           one or more files where an editor is run with the user's credentials instead of with
           elevated privileges.  sudo achieves this by creating user-writable temporary copies of
           the files to be edited and then overwriting the originals with the temporary copies
           after editing is complete.  If the plugin supports sudoedit, it should choose the
           editor to be used, potentially from a variable in the user's environment, such as
           EDITOR, and include it in argv_out (note that environment variables may include
           command line options).  The files to be edited should be copied from argv into
           argv_out, separated from the editor and its arguments by a “--” element.  The “--”
           will be removed by sudo before the editor is executed.  The plugin should also set
           sudoedit=true in the command_info list.

           The check_policy() function returns 1 if the command is allowed, 0 if not allowed, -1
           for a general error, or -2 for a usage error or if sudoedit was specified but is
           unsupported by the plugin.  In the latter case, sudo will print a usage message before
           it exits.  If an error occurs, the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           argc  The number of elements in argv, not counting the final NULL pointer.

           argv  The argument vector describing the command the user wishes to run, in the same
                 form as what would be passed to the execve(2) system call.  The vector is
                 terminated by a NULL pointer.

           env_add
                 Additional environment variables specified by the user on the command line in
                 the form of a NULL-terminated vector of “name=value” strings.  The plugin may
                 reject the command if one or more variables are not allowed to be set, or it may
                 silently ignore such variables.

                 When parsing env_add, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           command_info
                 Information about the command being run in the form of “name=value” strings.
                 These values are used by sudo to set the execution environment when running a
                 command.  The plugin is responsible for creating and populating the vector,
                 which must be terminated with a NULL pointer.  The following values are
                 recognized by sudo:

                 chroot=string
                       The root directory to use when running the command.

                 closefrom=number
                       If specified, sudo will close all files descriptors with a value of number
                       or higher.

                 command=string
                       Fully qualified path to the command to be executed.

                 cwd=string
                       The current working directory to change to when executing the command.  If
                       sudo is unable to change to the new working directory, the command will
                       not be run unless cwd_optional is also set (see below).

                 cwd_optional=bool
                       If enabled, sudo will treat an inability to change to the new working
                       directory as a non-fatal error.  This setting has no effect unless cwd is
                       also set.

                 exec_background=bool
                       By default, sudo runs a command as the foreground process as long as sudo
                       itself is running in the foreground.  When exec_background is enabled and
                       the command is being run in a pseudo-terminal (due to I/O logging or the
                       use_pty setting), the command will be run as a background process.
                       Attempts to read from the controlling terminal (or to change terminal
                       settings) will result in the command being suspended with the SIGTTIN
                       signal (or SIGTTOU in the case of terminal settings).  If this happens
                       when sudo is a foreground process, the command will be granted the
                       controlling terminal and resumed in the foreground with no user
                       intervention required.  The advantage of initially running the command in
                       the background is that sudo need not read from the terminal unless the
                       command explicitly requests it.  Otherwise, any terminal input must be
                       passed to the command, whether it has required it or not (the kernel
                       buffers terminals so it is not possible to tell whether the command really
                       wants the input).  This is different from historic sudo behavior or when
                       the command is not being run in a pseudo-terminal.

                       For this to work seamlessly, the operating system must support the
                       automatic restarting of system calls.  Unfortunately, not all operating
                       systems do this by default, and even those that do may have bugs.  For
                       example, macOS fails to restart the tcgetattr() and tcsetattr() system
                       calls (this is a bug in macOS).  Furthermore, because this behavior
                       depends on the command stopping with the SIGTTIN or SIGTTOU signals,
                       programs that catch these signals and suspend themselves with a different
                       signal (usually SIGTOP) will not be automatically foregrounded.  Some
                       versions of the linux su(1) command behave this way.  Because of this, a
                       plugin should not set exec_background unless it is explicitly enabled by
                       the administrator and there should be a way to enabled or disable it on a
                       per-command basis.

                       This setting has no effect unless I/O logging is enabled or use_pty is
                       enabled.

                 execfd=number
                       If specified, sudo will use the fexecve(2) system call to execute the
                       command instead of execve(2).  The specified number must refer to an open
                       file descriptor.

                 iolog_compress=bool
                       Set to true if the I/O logging plugins, if any, should compress the log
                       data.  This is a hint to the I/O logging plugin which may choose to ignore
                       it.

                 iolog_group=string
                       The group that will own newly created I/O log files and directories.  This
                       is a hint to the I/O logging plugin which may choose to ignore it.

                 iolog_mode=octal
                       The file permission mode to use when creating I/O log files and
                       directories.  This is a hint to the I/O logging plugin which may choose to
                       ignore it.

                 iolog_user=string
                       The user that will own newly created I/O log files and directories.  This
                       is a hint to the I/O logging plugin which may choose to ignore it.

                 iolog_path=string
                       Fully qualified path to the file or directory in which I/O log is to be
                       stored.  This is a hint to the I/O logging plugin which may choose to
                       ignore it.  If no I/O logging plugin is loaded, this setting has no
                       effect.

                 iolog_stdin=bool
                       Set to true if the I/O logging plugins, if any, should log the standard
                       input if it is not connected to a terminal device.  This is a hint to the
                       I/O logging plugin which may choose to ignore it.

                 iolog_stdout=bool
                       Set to true if the I/O logging plugins, if any, should log the standard
                       output if it is not connected to a terminal device.  This is a hint to the
                       I/O logging plugin which may choose to ignore it.

                 iolog_stderr=bool
                       Set to true if the I/O logging plugins, if any, should log the standard
                       error if it is not connected to a terminal device.  This is a hint to the
                       I/O logging plugin which may choose to ignore it.

                 iolog_ttyin=bool
                       Set to true if the I/O logging plugins, if any, should log all terminal
                       input.  This only includes input typed by the user and not from a pipe or
                       redirected from a file.  This is a hint to the I/O logging plugin which
                       may choose to ignore it.

                 iolog_ttyout=bool
                       Set to true if the I/O logging plugins, if any, should log all terminal
                       output.  This only includes output to the screen, not output to a pipe or
                       file.  This is a hint to the I/O logging plugin which may choose to ignore
                       it.

                 login_class=string
                       BSD login class to use when setting resource limits and nice value
                       (optional).  This option is only set on systems that support login
                       classes.

                 nice=int
                       Nice value (priority) to use when executing the command.  The nice value,
                       if specified, overrides the priority associated with the login_class on
                       BSD systems.

                 noexec=bool
                       If set, prevent the command from executing other programs.

                 preserve_fds=list
                       A comma-separated list of file descriptors that should be preserved,
                       regardless of the value of the closefrom setting.  Only available starting
                       with API version 1.5.

                 preserve_groups=bool
                       If set, sudo will preserve the user's group vector instead of initializing
                       the group vector based on runas_user.

                 rlimit_as=soft,hard
                       The maximum size to which the process's address space may grow (in bytes),
                       if supported by the operating system.  The soft and hard limits are
                       separated by a comma.  If only a single value is specified, both the hard
                       and soft limits are set.  A value of “infinity” indicates that there is no
                       limit.  A value of “user” will cause the invoking user's resource limit to
                       be preserved.  A value of “default” will cause the target user's default
                       resource limit to be used on systems that allow per-user resource limits
                       to be configured.  Only available starting with API version 1.17.

                 rlimit_core=soft,hard
                       The largest size core dump file that may be created (in bytes).  The soft
                       and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_cpu=soft,hard
                       The maximum amount of CPU time that the process may use (in seconds).  The
                       soft and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_data=soft,hard
                       The maximum size of the data segment for the process (in bytes).  The soft
                       and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_fsize=soft,hard
                       The largest size file that the process may create (in bytes).  The soft
                       and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_locks=soft,hard
                       The maximum number of locks that the process may establish, if supported
                       by the operating system.  The soft and hard limits are separated by a
                       comma.  If only a single value is specified, both the hard and soft limits
                       are set.  A value of “infinity” indicates that there is no limit.  A value
                       of “user” will cause the invoking user's resource limit to be preserved.
                       A value of “default” will cause the target user's default resource limit
                       to be used on systems that allow per-user resource limits to be
                       configured.  Only available starting with API version 1.17.

                 rlimit_memlock=soft,hard
                       The maximum size that the process may lock in memory (in bytes), if
                       supported by the operating system.  The soft and hard limits are separated
                       by a comma.  If only a single value is specified, both the hard and soft
                       limits are set.  A value of “infinity” indicates that there is no limit.
                       A value of “user” will cause the invoking user's resource limit to be
                       preserved.  A value of “default” will cause the target user's default
                       resource limit to be used on systems that allow per-user resource limits
                       to be configured.  Only available starting with API version 1.17.

                 rlimit_nofile=soft,hard
                       The maximum number of files that the process may have open.  The soft and
                       hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_nproc=soft,hard
                       The maximum number of processes that the user may run simultaneously.  The
                       soft and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 rlimit_rss=soft,hard
                       The maximum size to which the process's resident set size may grow (in
                       bytes).  The soft and hard limits are separated by a comma.  If only a
                       single value is specified, both the hard and soft limits are set.  A value
                       of “infinity” indicates that there is no limit.  A value of “user” will
                       cause the invoking user's resource limit to be preserved.  A value of
                       “default” will cause the target user's default resource limit to be used
                       on systems that allow per-user resource limits to be configured.  Only
                       available starting with API version 1.17.

                 rlimit_stack=soft,hard
                       The maximum size to which the process's stack may grow (in bytes).  The
                       soft and hard limits are separated by a comma.  If only a single value is
                       specified, both the hard and soft limits are set.  A value of “infinity”
                       indicates that there is no limit.  A value of “user” will cause the
                       invoking user's resource limit to be preserved.  A value of “default” will
                       cause the target user's default resource limit to be used on systems that
                       allow per-user resource limits to be configured.  Only available starting
                       with API version 1.17.

                 runas_egid=gid
                       Effective group-ID to run the command as.  If not specified, the value of
                       runas_gid is used.

                 runas_euid=uid
                       Effective user-ID to run the command as.  If not specified, the value of
                       runas_uid is used.

                 runas_gid=gid
                       Group-ID to run the command as.

                 runas_group=string
                       The name of the group the command will run as, if it is different from the
                       runas_user's default group.  This value is provided for auditing purposes
                       only, the sudo front-end uses runas_egid and runas_gid when executing the
                       command.

                 runas_groups=list
                       The supplementary group vector to use for the command in the form of a
                       comma-separated list of group-IDs.  If preserve_groups is set, this option
                       is ignored.

                 runas_uid=uid
                       User-ID to run the command as.

                 runas_user=string
                       The name of the user the command will run as, which should correspond to
                       runas_euid (or runas_uid if runas_euid is not set).  This value is
                       provided for auditing purposes only, the sudo front-end uses runas_euid
                       and runas_uid when executing the command.

                 selinux_role=string
                       SELinux role to use when executing the command.

                 selinux_type=string
                       SELinux type to use when executing the command.

                 set_utmp=bool
                       Create a utmp (or utmpx) entry when a pseudo-terminal is allocated.  By
                       default, the new entry will be a copy of the user's existing utmp entry
                       (if any), with the tty, time, type, and pid fields updated.

                 sudoedit=bool
                       Set to true when in sudoedit mode.  The plugin may enable sudoedit mode
                       even if sudo was not invoked as sudoedit.  This allows the plugin to
                       perform command substitution and transparently enable sudoedit when the
                       user attempts to run an editor.

                 sudoedit_checkdir=bool
                       Set to false to disable directory writability checks in sudoedit.  By
                       default, sudoedit 1.8.16 and higher will check all directory components of
                       the path to be edited for writability by the invoking user.  Symbolic
                       links will not be followed in writable directories and sudoedit will
                       refuse to edit a file located in a writable directory.  These restrictions
                       are not enforced when sudoedit is run by root.  The sudoedit_follow option
                       can be set to false to disable this check.  Only available starting with
                       API version 1.8.

                 sudoedit_follow=bool
                       Set to true to allow sudoedit to edit files that are symbolic links.  By
                       default, sudoedit 1.8.15 and higher will refuse to open a symbolic link.
                       The sudoedit_follow option can be used to restore the older behavior and
                       allow sudoedit to open symbolic links.  Only available starting with API
                       version 1.8.

                 timeout=int
                       Command timeout.  If non-zero then when the timeout expires the command
                       will be killed.

                 umask=octal
                       The file creation mask to use when executing the command.  This value may
                       be overridden by PAM or login.conf on some systems unless the
                       umask_override option is also set.

                 umask_override=bool
                       Force the value specified by the umask option to override any umask set by
                       PAM or login.conf.

                 use_pty=bool
                       Allocate a pseudo-terminal to run the command in, regardless of whether or
                       not I/O logging is in use.  By default, sudo will only run the command in
                       a pseudo-terminal when an I/O log plugin is loaded.

                 utmp_user=string
                       User name to use when constructing a new utmp (or utmpx) entry when
                       set_utmp is enabled.  This option can be used to set the user field in the
                       utmp entry to the user the command runs as rather than the invoking user.
                       If not set, sudo will base the new entry on the invoking user's existing
                       entry.

                 Unsupported values will be ignored.

           argv_out
                 The NULL-terminated argument vector to pass to the execve(2) system call when
                 executing the command.  The plugin is responsible for allocating and populating
                 the vector.

           user_env_out
                 The NULL-terminated environment vector to use when executing the command.  The
                 plugin is responsible for allocating and populating the vector.

           errstr
                 If the check_policy() function returns a value other than 1, the plugin may
                 store a message describing the failure or error in errstr.  The sudo front-end
                 will then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     list
           int (*list)(int argc, char * const argv[], int verbose,
               const char *list_user, const char **errstr);

           List available privileges for the invoking user.  Returns 1 on success, 0 on failure,
           and -1 on error.  On error, the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           Privileges should be output via the conversation() or plugin_printf() function using
           SUDO_CONV_INFO_MSG.

           The function arguments are as follows:

           argc  The number of elements in argv, not counting the final NULL pointer.

           argv  If non-NULL, an argument vector describing a command the user wishes to check
                 against the policy in the same form as what would be passed to the execve(2)
                 system call.  If the command is permitted by the policy, the fully-qualified
                 path to the command should be displayed along with any command line arguments.

           verbose
                 Flag indicating whether to list in verbose mode or not.

           list_user
                 The name of a different user to list privileges for if the policy allows it.  If
                 NULL, the plugin should list the privileges of the invoking user.

           errstr
                 If the list() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     validate
           int (*validate)(const char **errstr);

           The validate() function is called when sudo is run with the -v option.  For policy
           plugins such as sudoers that cache authentication credentials, this function will
           validate and cache the credentials.

           The validate() function should be NULL if the plugin does not support credential
           caching.

           Returns 1 on success, 0 on failure, and -1 on error.  On error, the plugin may
           optionally call the conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information to the user.

           The function arguments are as follows:

           errstr
                 If the validate() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     invalidate
           void (*invalidate)(int remove);

           The invalidate() function is called when sudo is run with the -k or -K option.  For
           policy plugins such as sudoers that cache authentication credentials, this function
           will invalidate the credentials.  If the remove flag is set, the plugin may remove the
           credentials instead of simply invalidating them.

           The invalidate() function should be NULL if the plugin does not support credential
           caching.

     init_session
           int (*init_session)(struct passwd *pwd, char **user_env_out[]);

           The init_session() function is called before sudo sets up the execution environment
           for the command.  It is run in the parent sudo process and before any user-ID or
           group-ID changes.  This can be used to perform session setup that is not supported by
           command_info, such as opening the PAM session.  The close() function can be used to
           tear down the session that was opened by init_session.

           The pwd argument points to a passwd struct for the user the command will be run as if
           the user-ID the command will run as was found in the password database, otherwise it
           will be NULL.

           The user_env_out argument points to the environment the command will run in, in the
           form of a NULL-terminated vector of “name=value” strings.  This is the same string
           passed back to the front-end via the Policy Plugin's user_env_out parameter.  If the
           init_session() function needs to modify the user environment, it should update the
           pointer stored in user_env_out.  The expected use case is to merge the contents of the
           PAM environment (if any) with the contents of user_env_out.  NOTE: the user_env_out
           parameter is only available starting with API version 1.2.  A plugin must check the
           API version specified by the sudo front-end before using user_env_out.  Failure to do
           so may result in a crash.

           Returns 1 on success, 0 on failure, and -1 on error.  On error, the plugin may
           optionally call the conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information to the user.

     register_hooks
           void (*register_hooks)(int version,
              int (*register_hook)(struct sudo_hook *hook));

           The register_hooks() function is called by the sudo front-end to register any hooks
           the plugin needs.  If the plugin does not support hooks, register_hooks should be set
           to the NULL pointer.

           The version argument describes the version of the hooks API supported by the sudo
           front-end.

           The register_hook() function should be used to register any supported hooks the plugin
           needs.  It returns 0 on success, 1 if the hook type is not supported, and -1 if the
           major version in struct hook does not match the front-end's major hook API version.

           See the Hook function API section below for more information about hooks.

           NOTE: the register_hooks() function is only available starting with API version 1.2.
           If the sudo front-end doesn't support API version 1.2 or higher, register_hooks will
           not be called.

     deregister_hooks
           void (*deregister_hooks)(int version,
              int (*deregister_hook)(struct sudo_hook *hook));

           The deregister_hooks() function is called by the sudo front-end to deregister any
           hooks the plugin has registered.  If the plugin does not support hooks,
           deregister_hooks should be set to the NULL pointer.

           The version argument describes the version of the hooks API supported by the sudo
           front-end.

           The deregister_hook() function should be used to deregister any hooks that were put in
           place by the register_hook() function.  If the plugin tries to deregister a hook that
           the front-end does not support, deregister_hook will return an error.

           See the Hook function API section below for more information about hooks.

           NOTE: the deregister_hooks() function is only available starting with API version 1.2.
           If the sudo front-end doesn't support API version 1.2 or higher, deregister_hooks will
           not be called.

     event_alloc
           struct sudo_plugin_event * (*event_alloc)(void);

           The event_alloc() function is used to allocate a struct sudo_plugin_event which
           provides access to the main sudo event loop.  Unlike the other fields, the
           event_alloc() pointer is filled in by the sudo front-end, not by the plugin.

           See the Event API section below for more information about events.

           NOTE: the event_alloc() function is only available starting with API version 1.15.  If
           the sudo front-end doesn't support API version 1.15 or higher, event_alloc() will not
           be set.

     errstr
           If the init_session() function returns a value other than 1, the plugin may store a
           message describing the failure or error in errstr.  The sudo front-end will then pass
           this value to any registered audit plugins.  The string stored in errstr must remain
           valid until the plugin's close() function is called.

           NOTE: the errstr parameter is only available starting with API version 1.15.  A plugin
           must check the API version specified by the sudo front-end before using errstr.
           Failure to do so may result in a crash.

     Policy Plugin Version Macros

     /* Plugin API version major/minor. */
     #define SUDO_API_VERSION_MAJOR 1
     #define SUDO_API_VERSION_MINOR 13
     #define SUDO_API_MKVERSION(x, y) ((x << 16) | y)
     #define SUDO_API_VERSION SUDO_API_MKVERSION(SUDO_API_VERSION_MAJOR,\
                                                 SUDO_API_VERSION_MINOR)

     /* Getters and setters for API version */
     #define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
     #define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
     #define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \
         *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
     } while(0)
     #define SUDO_API_VERSION_SET_MINOR(vp, n) do { \
         *(vp) = (*(vp) & 0xffff0000) | (n); \
     } while(0)

   I/O plugin API
     struct io_plugin {
     #define SUDO_IO_PLUGIN 2
         unsigned int type; /* always SUDO_IO_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t plugin_printf, char * const settings[],
             char * const user_info[], char * const command_info[],
             int argc, char * const argv[], char * const user_env[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int exit_status, int error); /* wait status or error */
         int (*show_version)(int verbose);
         int (*log_ttyin)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_ttyout)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stdin)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stdout)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stderr)(const char *buf, unsigned int len,
             const char **errstr);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
         int (*change_winsize)(unsigned int lines, unsigned int cols,
             const char **errstr);
         int (*log_suspend)(int signo, const char **errstr);
         struct sudo_plugin_event * (*event_alloc)(void);
     };

     When an I/O plugin is loaded, sudo runs the command in a pseudo-terminal.  This makes it
     possible to log the input and output from the user's session.  If any of the standard input,
     standard output, or standard error do not correspond to a tty, sudo will open a pipe to
     capture the I/O for logging before passing it on.

     The log_ttyin function receives the raw user input from the terminal device (note that this
     will include input even when echo is disabled, such as when a password is read).  The
     log_ttyout function receives output from the pseudo-terminal that is suitable for replaying
     the user's session at a later time.  The log_stdin(), log_stdout(), and log_stderr()
     functions are only called if the standard input, standard output, or standard error
     respectively correspond to something other than a tty.

     Any of the logging functions may be set to the NULL pointer if no logging is to be
     performed.  If the open function returns 0, no I/O will be sent to the plugin.

     If a logging function returns an error (-1), the running command will be terminated and all
     of the plugin's logging functions will be disabled.  Other I/O logging plugins will still
     receive any remaining input or output that has not yet been processed.

     If an input logging function rejects the data by returning 0, the command will be terminated
     and the data will not be passed to the command, though it will still be sent to any other
     I/O logging plugins.  If an output logging function rejects the data by returning 0, the
     command will be terminated and the data will not be written to the terminal, though it will
     still be sent to any other I/O logging plugins.

     The audit_plugin struct has the following fields:

     type  The type field should always be set to SUDO_IO_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t plugin_printf, char * const settings[],
               char * const user_info[], char * const command_info[],
               int argc, char * const argv[], char * const user_env[],
               char * const plugin_options[]);

           The open() function is run before the log_ttyin(), log_ttyout(), log_stdin(),
           log_stdout(), log_stderr(), log_suspend(), change_winsize(), or show_version()
           functions are called.  It is only called if the version is being requested or if the
           policy plugin's check_policy() function has returned successfully.  It returns 1 on
           success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage
           error.  In the latter case, sudo will print a usage message before it exits.  If an
           error occurs, the plugin may optionally call the conversation() or plugin_printf()
           function with SUDO_CONF_ERROR_MSG to present additional error information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to determine the major and minor
                 version number of the plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that may be used by the show_version()
                 function to display version information (see show_version() below).  The
                 conversation() function may also be used to display additional error message to
                 the user.  The conversation() function returns 0 on success and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used by the show_version()
                 function to display version information (see show_version below).  The
                 plugin_printf() function may also be used to display additional error message to
                 the user.  The plugin_printf() function returns number of characters printed on
                 success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.  These settings correspond to
                 options the user specified when running sudo.  As such, they will only be
                 present when the corresponding option has been specified on the command line.

                 When parsing settings, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible settings.

           user_info
                 A vector of information about the user running the command in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           command_info
                 A vector of information describing the command being run in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           argc  The number of elements in argv, not counting the final NULL pointer.  It can be
                 zero, when sudo is called with -V.

           argv  If non-NULL, an argument vector describing a command the user wishes to run in
                 the same form as what would be passed to the execve(2) system call.

           user_env
                 The user's environment in the form of a NULL-terminated vector of “name=value”
                 strings.

                 When parsing user_env, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin path are treated as
                 arguments to the plugin.  These arguments are split on a white space boundary
                 and are passed to the plugin in the form of a NULL-terminated array of strings.
                 If no arguments were specified, plugin_options will be the NULL pointer.

                 NOTE: the plugin_options parameter is only available starting with API version
                 1.2.  A plugin must check the API version specified by the sudo front-end before
                 using plugin_options.  Failure to do so may result in a crash.

           errstr
                 If the open() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     close
           void (*close)(int exit_status, int error);

           The close() function is called when sudo is finished, shortly before it exits.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2) system call, or zero if no
                 command was run.  The value of exit_status is undefined if error is non-zero.

           error
                 If the command could not be executed, this is set to the value of errno set by
                 the execve(2) system call.  If the command was successfully executed, the value
                 of error is zero.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user specifies the -V option.
           The plugin may display its version information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.

           Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was
           a usage error, although the return value is currently ignored.

     log_ttyin
           int (*log_ttyin)(const char *buf, unsigned int len,
               const char **errstr);

           The log_ttyin() function is called whenever data can be read from the user but before
           it is passed to the running command.  This allows the plugin to reject data if it
           chooses to (for instance if the input contains banned content).  Returns 1 if the data
           should be passed to the command, 0 if the data is rejected (which will terminate the
           running command), or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing user input.

           len   The length of buf in bytes.

           errstr
                 If the log_ttyin() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     log_ttyout
           int (*log_ttyout)(const char *buf, unsigned int len,
               const char **errstr);

           The log_ttyout() function is called whenever data can be read from the command but
           before it is written to the user's terminal.  This allows the plugin to reject data if
           it chooses to (for instance if the output contains banned content).  Returns 1 if the
           data should be passed to the user, 0 if the data is rejected (which will terminate the
           running command), or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_ttyout() function returns a value other than 1, the plugin may store
                 a message describing the failure or error in errstr.  The sudo front-end will
                 then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     log_stdin
           int (*log_stdin)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stdin() function is only used if the standard input does not correspond to a
           tty device.  It is called whenever data can be read from the standard input but before
           it is passed to the running command.  This allows the plugin to reject data if it
           chooses to (for instance if the input contains banned content).  Returns 1 if the data
           should be passed to the command, 0 if the data is rejected (which will terminate the
           running command), or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing user input.

           len   The length of buf in bytes.

           errstr
                 If the log_stdin() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     log_stdout
           int (*log_stdout)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stdout() function is only used if the standard output does not correspond to a
           tty device.  It is called whenever data can be read from the command but before it is
           written to the standard output.  This allows the plugin to reject data if it chooses
           to (for instance if the output contains banned content).  Returns 1 if the data should
           be passed to the user, 0 if the data is rejected (which will terminate the running
           command), or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_stdout() function returns a value other than 1, the plugin may store
                 a message describing the failure or error in errstr.  The sudo front-end will
                 then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     log_stderr
           int (*log_stderr)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stderr() function is only used if the standard error does not correspond to a
           tty device.  It is called whenever data can be read from the command but before it is
           written to the standard error.  This allows the plugin to reject data if it chooses to
           (for instance if the output contains banned content).  Returns 1 if the data should be
           passed to the user, 0 if the data is rejected (which will terminate the running
           command), or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_stderr() function returns a value other than 1, the plugin may store
                 a message describing the failure or error in errstr.  The sudo front-end will
                 then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     register_hooks
           See the Policy plugin API section for a description of register_hooks.

     deregister_hooks
           See the Policy plugin API section for a description of deregister_hooks.

     change_winsize
           int (*change_winsize)(unsigned int lines, unsigned int cols,
               const char **errstr);

           The change_winsize() function is called whenever the window size of the terminal
           changes from the initial values specified in the user_info list.  Returns -1 if an
           error occurred, in which case no further calls to change_winsize() will be made,

           The function arguments are as follows:

           lines
                 The number of lines (rows) in the re-sized terminal.

           cols  The number of columns in the re-sized terminal.

           errstr
                 If the change_winsize() function returns a value other than 1, the plugin may
                 store a message describing the failure or error in errstr.  The sudo front-end
                 will then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

     log_suspend
           int (*log_suspend)(int signo, const char **errstr);

           The log_suspend() function is called whenever a command is suspended or resumed.
           Logging this information makes it possible to skip the period of time when the command
           was suspended during playback of a session.  Returns -1 if an error occurred, in which
           case no further calls to log_suspend() will be made,

           The function arguments are as follows:

           signo
                 The signal that caused the command to be suspended, or SIGCONT if the command
                 was resumed.

           errstr
                 If the log_suspend() function returns a value other than 1, the plugin may store
                 a message describing the failure or error in errstr.  The sudo front-end will
                 then pass this value to any registered audit plugins.  The string stored in
                 errstr must remain valid until the plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting with API version 1.15.  A
                 plugin must check the API version specified by the sudo front-end before using
                 errstr.  Failure to do so may result in a crash.

           event_alloc
                 struct sudo_plugin_event * (*event_alloc)(void);

                 The event_alloc() function is used to allocate a struct sudo_plugin_event which
                 provides access to the main sudo event loop.  Unlike the other fields, the
                 event_alloc() pointer is filled in by the sudo front-end, not by the plugin.

                 See the Event API section below for more information about events.

                 NOTE: the event_alloc() function is only available starting with API version
                 1.15.  If the sudo front-end doesn't support API version 1.15 or higher,
                 event_alloc() will not be set.

           I/O Plugin Version Macros

           Same as for the Policy plugin API.

   Audit plugin API
     /* Audit plugin close function status types. */
     #define SUDO_PLUGIN_NO_STATUS           0
     #define SUDO_PLUGIN_WAIT_STATUS         1
     #define SUDO_PLUGIN_EXEC_ERROR          2
     #define SUDO_PLUGIN_SUDO_ERROR          3

     #define SUDO_AUDIT_PLUGIN 3
     struct audit_plugin {
         unsigned int type; /* always SUDO_AUDIT_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t sudo_printf, char * const settings[],
             char * const user_info[], int submit_optind,
             char * const submit_argv[], char * const submit_envp[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int status_type, int status);
         int (*accept)(const char *plugin_name,
             unsigned int plugin_type, char * const command_info[],
             char * const run_argv[], char * const run_envp[],
             const char **errstr);
         int (*reject)(const char *plugin_name, unsigned int plugin_type,
             const char *audit_msg, char * const command_info[],
             const char **errstr);
         int (*error)(const char *plugin_name, unsigned int plugin_type,
             const char *audit_msg, char * const command_info[],
             const char **errstr);
         int (*show_version)(int verbose);
         void (*register_hooks)(int version,
             int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
             int (*deregister_hook)(struct sudo_hook *hook));
         struct sudo_plugin_event * (*event_alloc)(void);
     }

     An audit plugin can be used to log successful and unsuccessful attempts to run sudo
     independent of the policy or any I/O plugins.  Multiple audit plugins may be specified in
     sudo.conf(5).

     The audit_plugin struct has the following fields:

     type  The type field should always be set to SUDO_AUDIT_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t sudo_printf, char * const settings[],
               char * const user_info[], int submit_optind,
               char * const submit_argv[], char * const submit_envp[],
               char * const plugin_options[], const char **errstr);

           The audit open() function is run before any other sudo plugin API functions.  This
           makes it possible to audit failures in the other plugins.  It returns 1 on success, 0
           on failure, -1 if a general error occurred, or -2 if there was a usage error.  In the
           latter case, sudo will print a usage message before it exits.  If an error occurs, the
           plugin may optionally call the conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to determine the major and minor
                 version number of the plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that may be used by the show_version()
                 function to display version information (see show_version() below).  The
                 conversation() function may also be used to display additional error message to
                 the user.  The conversation() function returns 0 on success, and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used by the show_version()
                 function to display version information (see show_version below).  The
                 plugin_printf() function may also be used to display additional error message to
                 the user.  The plugin_printf() function returns number of characters printed on
                 success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.  These settings correspond to
                 options the user specified when running sudo.  As such, they will only be
                 present when the corresponding option has been specified on the command line.

                 When parsing settings, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible settings.

           user_info
                 A vector of information about the user running the command in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           submit_optind
                 The index into submit_argv that corresponds to the first entry that is not a
                 command line option.  If submit_argv only consists of options, which may be the
                 case with the -l or -v options, submit_argv[submit_optind] will evaluate to the
                 NULL pointer.

           submit_argv
                 The argument vector sudo was invoked with, including all command line options.
                 The submit_optind argument can be used to determine the end of the command line
                 options.

           submit_envp
                 The invoking user's environment in the form of a NULL-terminated vector of
                 “name=value” strings.

                 When parsing submit_envp, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin path are treated as
                 arguments to the plugin.  These arguments are split on a white space boundary
                 and are passed to the plugin in the form of a NULL-terminated array of strings.
                 If no arguments were specified, plugin_options will be the NULL pointer.

           errstr
                 If the open() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     close
           void (*close)(int status_type, int status);

           The close() function is called when sudo is finished, shortly before it exits.

           The function arguments are as follows:

           status_type
                 The type of status being passed.  One of SUDO_PLUGIN_NO_STATUS,
                 SUDO_PLUGIN_WAIT_STATUS, SUDO_PLUGIN_EXEC_ERROR or SUDO_PLUGIN_SUDO_ERROR.

           status
                 Depending on the value of status_type, this value is either ignored, the
                 command's exit status as returned by the wait(2) system call, the value of errno
                 set by the execve(2) system call, or the value of errno resulting from an error
                 in the sudo front-end.

     accept
           int (*accept)(const char *plugin_name, unsigned int plugin_type,
               char * const command_info[], char * const run_argv[],
               char * const run_envp[], const char **errstr);

           The accept() function is called when a command or action is accepted by a policy or
           approval plugin.  The function arguments are as follows:

           plugin_name
                 The name of the plugin that accepted the command or “sudo” for the sudo front-
                 end.

           plugin_type
                 The type of plugin that accepted the command, currently either
                 SUDO_POLICY_PLUGIN, SUDO_POLICY_APPROVAL, or SUDO_FRONT_END.  The accept()
                 function is called multiple times--once for each policy or approval plugin that
                 succeeds and once for the sudo front-end.  When called on behalf of the sudo
                 front-end, command_info may include information from an I/O logging plugin as
                 well.

                 Typically, an audit plugin is interested in either the accept status from the
                 sudo front-end or from the various policy and approval plugins, but not both.
                 It is possible for the policy plugin to accept a command that is later rejected
                 by an approval plugin, in which case the audit plugin's accept() and reject()
                 functions will both be called.

           command_info
                 An optional vector of information describing the command being run in the form
                 of “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           run_argv
                 A NULL-terminated argument vector describing a command that will be run in the
                 same form as what would be passed to the execve(2) system call.

           run_envp
                 The environment the command will be run with in the form of a NULL-terminated
                 vector of “name=value” strings.

                 When parsing run_envp, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           errstr
                 If the accept() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     reject
           int (*reject)(const char *plugin_name, unsigned int plugin_type,
               const char *audit_msg, char * const command_info[],
               const char **errstr);

           The reject() function is called when a command or action is rejected by a plugin.  The
           function arguments are as follows:

           plugin_name
                 The name of the plugin that rejected the command.

           plugin_type
                 The type of plugin that rejected the command, currently either
                 SUDO_POLICY_PLUGIN, SUDO_APPROVAL_PLUGIN, or SUDO_IO_PLUGIN.

                 Unlike the accept() function, the reject() function is not called on behalf of
                 the sudo front-end.

           audit_msg
                 An optional string describing the reason the command was rejected by the plugin.
                 If the plugin did not provide a reason, audit_msg will be the NULL pointer.

           command_info
                 An optional vector of information describing the command being run in the form
                 of “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           errstr
                 If the reject() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     error
           int (*error)(const char *plugin_name, unsigned int plugin_type,
               const char *audit_msg, char * const command_info[],
               const char **errstr);

           The error() function is called when a plugin or the sudo front-end returns an error.
           The function arguments are as follows:

           plugin_name
                 The name of the plugin that generated the error or “sudo” for the sudo front-
                 end.

           plugin_type
                 The type of plugin that generated the error, or SUDO_FRONT_END for the sudo
                 front-end.

           audit_msg
                 An optional string describing the plugin error.  If the plugin did not provide a
                 description, audit_msg will be the NULL pointer.

           command_info
                 An optional vector of information describing the command being run in the form
                 of “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           errstr
                 If the error() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user specifies the -V option.
           The plugin may display its version information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the user requests detailed
           version information, the verbose flag will be set.

           Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was
           a usage error, although the return value is currently ignored.

     register_hooks
           See the Policy plugin API section for a description of register_hooks.

     deregister_hooks
           See the Policy plugin API section for a description of deregister_hooks.

     event_alloc
           struct sudo_plugin_event * (*event_alloc)(void);

           The event_alloc() function is used to allocate a struct sudo_plugin_event which
           provides access to the main sudo event loop.  Unlike the other fields, the
           event_alloc() pointer is filled in by the sudo front-end, not by the plugin.

           See the Event API section below for more information about events.

           NOTE: the event_alloc() function is only available starting with API version 1.17.  If
           the sudo front-end doesn't support API version 1.17 or higher, event_alloc() will not
           be set.

   Approval plugin API
     struct approval_plugin {
     #define SUDO_APPROVAL_PLUGIN 4
         unsigned int type; /* always SUDO_APPROVAL_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t sudo_printf, char * const settings[],
             char * const user_info[], int submit_optind,
             char * const submit_argv[], char * const submit_envp[],
             char * const plugin_options[], const char **errstr);
         void (*close)(void);
         int (*check)(char * const command_info[], char * const run_argv[],
             char * const run_envp[], const char **errstr);
         int (*show_version)(int verbose);
     };

     An approval plugin can be used to apply extra constraints after a command has been accepted
     by the policy plugin.  Unlike the other plugin types, it does not remain open until the
     command completes.  The plugin is opened before a call to check() or show_version() and
     closed shortly thereafter (audit plugin functions must be called before the plugin is
     closed).  Multiple approval plugins may be specified in sudo.conf(5).

     The approval_plugin struct has the following fields:

     type  The type field should always be set to SUDO_APPROVAL_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t sudo_printf, char * const settings[],
               char * const user_info[], int submit_optind,
               char * const submit_argv[], char * const submit_envp[],
               char * const plugin_options[], const char **errstr);

           The approval open() function is run immediately before a call to the plugin's check()
           or show_version() functions.  It is only called if the version is being requested or
           if the policy plugin's check_policy() function has returned successfully.  It returns
           1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage
           error.  In the latter case, sudo will print a usage message before it exits.  If an
           error occurs, the plugin may optionally call the conversation() or plugin_printf()
           function with SUDO_CONF_ERROR_MSG to present additional error information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to determine the major and minor
                 version number of the plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that can be used by the plugin to
                 interact with the user (see Conversation API for details).  Returns 0 on success
                 and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used to display informational
                 or error messages (see Conversation API for details).  Returns the number of
                 characters printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.  These settings correspond to
                 options the user specified when running sudo.  As such, they will only be
                 present when the corresponding option has been specified on the command line.

                 When parsing settings, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible settings.

           user_info
                 A vector of information about the user running the command in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           submit_optind
                 The index into submit_argv that corresponds to the first entry that is not a
                 command line option.  If submit_argv only consists of options, which may be the
                 case with the -l or -v options, submit_argv[submit_optind] will evaluate to the
                 NULL pointer.

           submit_argv
                 The argument vector sudo was invoked with, including all command line options.
                 The submit_optind argument can be used to determine the end of the command line
                 options.

           submit_envp
                 The invoking user's environment in the form of a NULL-terminated vector of
                 “name=value” strings.

                 When parsing submit_envp, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin path are treated as
                 arguments to the plugin.  These arguments are split on a white space boundary
                 and are passed to the plugin in the form of a NULL-terminated array of strings.
                 If no arguments were specified, plugin_options will be the NULL pointer.

           errstr
                 If the open() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     close
           void (*close)(void);

           The close() function is called after the approval plugin's check() or show_version()
           functions have been called.  It takes no arguments.  The close() function is typically
           used to perform plugin-specific cleanup, such as the freeing of memory objects
           allocated by the plugin.  If the plugin does not need to perform any cleanup, close()
           may be set to the NULL pointer.

     check
           int (*check)(char * const command_info[], char * const run_argv[],
               char * const run_envp[], const char **errstr);

           The approval check() function is run after the policy plugin check_policy() function
           and before any I/O logging plugins.  If multiple approval plugins are loaded, they
           must all succeed for the command to be allowed.  It returns 1 on success, 0 on
           failure, -1 if a general error occurred, or -2 if there was a usage error.  In the
           latter case, sudo will print a usage message before it exits.  If an error occurs, the
           plugin may optionally call the conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information to the user.

           The function arguments are as follows:

           command_info
                 A vector of information describing the command being run in the form of
                 “name=value” strings.  The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

                 See the Policy plugin API section for a list of all possible strings.

           run_argv
                 A NULL-terminated argument vector describing a command that will be run in the
                 same form as what would be passed to the execve(2) system call.

           run_envp
                 The environment the command will be run with in the form of a NULL-terminated
                 vector of “name=value” strings.

                 When parsing run_envp, the plugin should split on the first equal sign (‘=’)
                 since the name field will never include one itself but the value might.

           errstr
                 If the open() function returns a value other than 1, the plugin may store a
                 message describing the failure or error in errstr.  The sudo front-end will then
                 pass this value to any registered audit plugins.  The string stored in errstr
                 must remain valid until the plugin's close() function is called.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user specifies the -V option.
           The plugin may display its version information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the user requests detailed
           version information, the verbose flag will be set.

           Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was
           a usage error, although the return value is currently ignored.

   Signal handlers
     The sudo front-end installs default signal handlers to trap common signals while the plugin
     functions are run.  The following signals are trapped by default before the command is
     executed:

       SIGALRM
       SIGHUP
       SIGINT
       SIGPIPE
       SIGQUIT
       SIGTERM
       SIGTSTP
       SIGUSR1
       SIGUSR2

     If a fatal signal is received before the command is executed, sudo will call the plugin's
     close() function with an exit status of 128 plus the value of the signal that was received.
     This allows for consistent logging of commands killed by a signal for plugins that log such
     information in their close() function.  An exception to this is SIGPIPE, which is ignored
     until the command is executed.

     A plugin may temporarily install its own signal handlers but must restore the original
     handler before the plugin function returns.

   Hook function API
     Beginning with plugin API version 1.2, it is possible to install hooks for certain functions
     called by the sudo front-end.

     Currently, the only supported hooks relate to the handling of environment variables.  Hooks
     can be used to intercept attempts to get, set, or remove environment variables so that these
     changes can be reflected in the version of the environment that is used to execute a
     command.  A future version of the API will support hooking internal sudo front-end functions
     as well.

     Hook structure

     Hooks in sudo are described by the following structure:

     typedef int (*sudo_hook_fn_t)();

     struct sudo_hook {
         unsigned int hook_version;
         unsigned int hook_type;
         sudo_hook_fn_t hook_fn;
         void *closure;
     };

     The sudo_hook structure has the following fields:

     hook_version
           The hook_version field should be set to SUDO_HOOK_VERSION.

     hook_type
           The hook_type field may be one of the following supported hook types:

           SUDO_HOOK_SETENV
                 The C library setenv(3) function.  Any registered hooks will run before the C
                 library implementation.  The hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_setenv_t)(const char *name,
                    const char *value, int overwrite, void *closure);

                 If the registered hook does not match the typedef the results are unspecified.

           SUDO_HOOK_UNSETENV
                 The C library unsetenv(3) function.  Any registered hooks will run before the C
                 library implementation.  The hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_unsetenv_t)(const char *name,
                    void *closure);

           SUDO_HOOK_GETENV
                 The C library getenv(3) function.  Any registered hooks will run before the C
                 library implementation.  The hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_getenv_t)(const char *name,
                    char **value, void *closure);

                 If the registered hook does not match the typedef the results are unspecified.

           SUDO_HOOK_PUTENV
                 The C library putenv(3) function.  Any registered hooks will run before the C
                 library implementation.  The hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_putenv_t)(char *string,
                    void *closure);

                 If the registered hook does not match the typedef the results are unspecified.

     hook_fn
           sudo_hook_fn_t hook_fn;

           The hook_fn field should be set to the plugin's hook implementation.  The actual
           function arguments will vary depending on the hook_type (see hook_type above).  In all
           cases, the closure field of struct sudo_hook is passed as the last function parameter.
           This can be used to pass arbitrary data to the plugin's hook implementation.

           The function return value may be one of the following:

           SUDO_HOOK_RET_ERROR
                 The hook function encountered an error.

           SUDO_HOOK_RET_NEXT
                 The hook completed without error, go on to the next hook (including the system
                 implementation if applicable).  For example, a getenv(3) hook might return
                 SUDO_HOOK_RET_NEXT if the specified variable was not found in the private copy
                 of the environment.

           SUDO_HOOK_RET_STOP
                 The hook completed without error, stop processing hooks for this invocation.
                 This can be used to replace the system implementation.  For example, a setenv
                 hook that operates on a private copy of the environment but leaves environ
                 unchanged.

     Note that it is very easy to create an infinite loop when hooking C library functions.  For
     example, a getenv(3) hook that calls the snprintf(3) function may create a loop if the
     snprintf(3) implementation calls getenv(3) to check the locale.  To prevent this, you may
     wish to use a static variable in the hook function to guard against nested calls.  For
     example:

     static int in_progress = 0; /* avoid recursion */
     if (in_progress)
         return SUDO_HOOK_RET_NEXT;
     in_progress = 1;
     ...
     in_progress = 0;
     return SUDO_HOOK_RET_STOP;

     Hook API Version Macros

     /* Hook API version major/minor */
     #define SUDO_HOOK_VERSION_MAJOR 1
     #define SUDO_HOOK_VERSION_MINOR 0
     #define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
                                                   SUDO_HOOK_VERSION_MINOR)

     For getters and setters see the Policy plugin API.

   Event API
     When sudo runs a command, it uses an event loop to service signals and I/O.  Events may be
     triggered based on time, a file or socket descriptor becoming ready, or due to receipt of a
     signal.  Starting with API version 1.15, it is possible for a plugin to participate in this
     event loop by calling the event_alloc() function.

     Event structure

     Events are described by the following structure:

     typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure);

     struct sudo_plugin_event {
         int (*set)(struct sudo_plugin_event *pev, int fd, int events,
             sudo_plugin_ev_callback_t callback, void *closure);
         int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
         int (*del)(struct sudo_plugin_event *pev);
         int (*pending)(struct sudo_plugin_event *pev, int events,
             struct timespec *ts);
         int (*fd)(struct sudo_plugin_event *pev);
         void (*setbase)(struct sudo_plugin_event *pev, void *base);
         void (*loopbreak)(struct sudo_plugin_event *pev);
         void (*free)(struct sudo_plugin_event *pev);
     };

     The sudo_plugin_event struct contains the following function pointers:

     set()
           int (*set)(struct sudo_plugin_event *pev, int fd, int events,
               sudo_plugin_ev_callback_t callback, void *closure);

           The set() function takes the following arguments:

           struct sudo_plugin_event *pev
                 A pointer to the struct sudo_plugin_event itself.

           fd    The file or socket descriptor for I/O-based events or the signal number for
                 signal events.  For time-based events, fd must be -1.

           events
                 The following values determine what will trigger the event callback:

                 SUDO_PLUGIN_EV_TIMEOUT
                       callback is run after the specified timeout expires

                 SUDO_PLUGIN_EV_READ
                       callback is run when the file descriptor is readable

                 SUDO_PLUGIN_EV_WRITE
                       callback is run when the file descriptor is writable

                 SUDO_PLUGIN_EV_PERSIST
                       event is persistent and remains enabled until explicitly deleted

                 SUDO_PLUGIN_EV_SIGNAL
                       callback is run when the specified signal is received

                 The SUDO_PLUGIN_EV_PERSIST flag may be ORed with any of the event types.  It is
                 also possible to OR SUDO_PLUGIN_EV_READ and SUDO_PLUGIN_EV_WRITE together to run
                 the callback when a descriptor is ready to be either read from or written to.
                 All other event values are mutually exclusive.

           sudo_plugin_ev_callback_t callback
                 typedef void (*sudo_plugin_ev_callback_t)(int fd, int what,
                     void *closure);

                 The function to call when an event is triggered.  The callback() function is run
                 with the following arguments:

                 fd    The file or socket descriptor for I/O-based events or the signal number
                       for signal events.

                 what  The event type that triggered that callback.  For events that have
                       multiple event types (for example SUDO_PLUGIN_EV_READ and
                       SUDO_PLUGIN_EV_WRITE) or have an associated timeout, what can be used to
                       determine why the callback was run.

                 closure
                       The generic pointer that was specified in the set() function.

           closure
                 A generic pointer that will be passed to the callback function.

           The set() function returns 1 on success, and -1 if a error occurred.

     add()
           int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);

           The add() function adds the event pev to sudo's event loop.  The event must have
           previously been initialized via the set() function.  If the timeout argument is not
           NULL, it should specify a (relative) timeout after which the event will be triggered
           if the main event criteria has not been met.  This is often used to implement an I/O
           timeout where the event will fire if a descriptor is not ready within a certain time
           period.  If the event is already present in the event loop, its timeout will be
           adjusted to match the new value, if any.

           The add() function returns 1 on success, and -1 if a error occurred.

     del()
           int (*del)(struct sudo_plugin_event *pev);

           The del() function deletes the event pev from sudo's event loop.  Deleted events can
           be added back via the add() function.

           The del() function returns 1 on success, and -1 if a error occurred.

     pending()
           int (*pending)(struct sudo_plugin_event *pev, int events,
               struct timespec *ts);

           The pending() function can be used to determine whether one or more events is pending.
           The events argument specifies which events to check for.  See the set() function for a
           list of valid event types.  If SUDO_PLUGIN_EV_TIMEOUT is specified in events, the
           event has an associated timeout and the ts pointer is non-NULL, it will be filled in
           with the remaining time.

     fd()
           int (*fd)(struct sudo_plugin_event *pev);

           The fd() function returns the descriptor or signal number associated with the event
           pev.

     setbase()
           void (*setbase)(struct sudo_plugin_event *pev, void *base);

           The setbase() function sets the underlying event base for pev to the specified value.
           This can be used to move an event created via event_alloc() to a new event loop
           allocated by sudo's event subsystem.  If base is NULL, pev's event base is reset to
           the default value, which corresponds to sudo's main event loop.  Using this function
           requires linking the plugin with the sudo_util library.  It is unlikely to be used
           outside of the sudoers plugin.

     loopbreak()
           void (*loopbreak)(struct sudo_plugin_event *pev);

           The loopbreak() function causes sudo's event loop to exit immediately and the running
           command to be terminated.

     free()
           void (*free)(struct sudo_plugin_event *pev);

           The free() function deletes the event pev from the event loop and frees the memory
           associated with it.

   Remote command execution
     The sudo front-end does not support running remote commands.  However, starting with sudo
     1.8.8, the -h option may be used to specify a remote host that is passed to the policy
     plugin.  A plugin may also accept a runas_user in the form of “user@hostname” which will
     work with older versions of sudo.  It is anticipated that remote commands will be supported
     by executing a “helper” program.  The policy plugin should setup the execution environment
     such that the sudo front-end will run the helper which, in turn, will connect to the remote
     host and run the command.

     For example, the policy plugin could utilize ssh to perform remote command execution.  The
     helper program would be responsible for running ssh with the proper options to use a private
     key or certificate that the remote host will accept and run a program on the remote host
     that would setup the execution environment accordingly.

     Note that remote sudoedit functionality must be handled by the policy plugin, not sudo
     itself as the front-end has no knowledge that a remote command is being executed.  This may
     be addressed in a future revision of the plugin API.

   Conversation API
     If the plugin needs to interact with the user, it may do so via the conversation() function.
     A plugin should not attempt to read directly from the standard input or the user's tty
     (neither of which are guaranteed to exist).  The caller must include a trailing newline in
     msg if one is to be printed.

     A printf()-style function is also available that can be used to display informational or
     error messages to the user, which is usually more convenient for simple messages where no
     use input is required.

     Conversation function structures

     The conversation function takes as arguments pointers to the following structures:

     struct sudo_conv_message {
     #define SUDO_CONV_PROMPT_ECHO_OFF  0x0001 /* do not echo user input */
     #define SUDO_CONV_PROMPT_ECHO_ON   0x0002 /* echo user input */
     #define SUDO_CONV_ERROR_MSG        0x0003 /* error message */
     #define SUDO_CONV_INFO_MSG         0x0004 /* informational message */
     #define SUDO_CONV_PROMPT_MASK      0x0005 /* mask user input */
     #define SUDO_CONV_PROMPT_ECHO_OK   0x1000 /* flag: allow echo if no tty */
     #define SUDO_CONV_PREFER_TTY       0x2000 /* flag: use tty if possible */
         int msg_type;
         int timeout;
         const char *msg;
     };

     #define SUDO_CONV_REPL_MAX      1023

     struct sudo_conv_reply {
         char *reply;
     };

     typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure);
     struct sudo_conv_callback {
         unsigned int version;
         void *closure;
         sudo_conv_callback_fn_t on_suspend;
         sudo_conv_callback_fn_t on_resume;
     };

     Pointers to the conversation() and printf()-style functions are passed in to the plugin's
     open() function when the plugin is initialized.  The following type definitions can be used
     in the declaration of the open() function:

     typedef int (*sudo_conv_t)(int num_msgs,
         const struct sudo_conv_message msgs[],
         struct sudo_conv_reply replies[], struct sudo_conv_callback *callback);

     typedef int (*sudo_printf_t)(int msg_type, const char *fmt, ...);

     To use the conversation() function, the plugin must pass an array of sudo_conv_message and
     sudo_conv_reply structures.  There must be a struct sudo_conv_message and struct
     sudo_conv_reply for each message in the conversation, that is, both arrays must have the
     same number of elements.  Each struct sudo_conv_reply must have its reply member initialized
     to NULL.  The struct sudo_conv_callback pointer, if not NULL, should contain function
     pointers to be called when the sudo process is suspended and/or resumed during conversation
     input.  The on_suspend and on_resume functions are called with the signal that caused sudo
     to be suspended and the closure pointer from the struct sudo_conv_callback.  These functions
     should return 0 on success and -1 on error.  On error, the conversation will end and the
     conversation function will return a value of -1.  The intended use is to allow the plugin to
     release resources, such as locks, that should not be held indefinitely while suspended and
     then reacquire them when the process is resumed.  Note that the functions are not actually
     invoked from within a signal handler.

     The msg_type must be set to one of the following values:

     SUDO_CONV_PROMPT_ECHO_OFF
           Prompt the user for input with echo disabled; this is generally used for passwords.
           The reply will be stored in the replies array, and it will never be NULL.

     SUDO_CONV_PROMPT_ECHO_ON
           Prompt the user for input with echo enabled.  The reply will be stored in the replies
           array, and it will never be NULL.

     SUDO_CONV_ERROR_MSG
           Display an error message.  The message is written to the standard error unless the
           SUDO_CONV_PREFER_TTY flag is set, in which case it is written to the user's terminal
           if possible.

     SUDO_CONV_INFO_MSG
           Display a message.  The message is written to the standard output unless the
           SUDO_CONV_PREFER_TTY flag is set, in which case it is written to the user's terminal
           if possible.

     SUDO_CONV_PROMPT_MASK
           Prompt the user for input but echo an asterisk character for each character read.  The
           reply will be stored in the replies array, and it will never be NULL.  This can be
           used to provide visual feedback to the user while reading sensitive information that
           should not be displayed.

     In addition to the above values, the following flag bits may also be set:

     SUDO_CONV_PROMPT_ECHO_OK
           Allow input to be read when echo cannot be disabled when the message type is
           SUDO_CONV_PROMPT_ECHO_OFF or SUDO_CONV_PROMPT_MASK.  By default, sudo will refuse to
           read input if the echo cannot be disabled for those message types.

     SUDO_CONV_PREFER_TTY
           When displaying a message via SUDO_CONV_ERROR_MSG or SUDO_CONV_INFO_MSG, try to write
           the message to the user's terminal.  If the terminal is unavailable, the standard
           error or standard output will be used, depending upon whether SUDO_CONV_ERROR_MSG or
           SUDO_CONV_INFO_MSG was used.  The user's terminal is always used when possible for
           input, this flag is only used for output.

     The timeout in seconds until the prompt will wait for no more input.  A zero value implies
     an infinite timeout.

     The plugin is responsible for freeing the reply buffer located in each struct
     sudo_conv_reply, if it is not NULL.  SUDO_CONV_REPL_MAX represents the maximum length of the
     reply buffer (not including the trailing NUL character).  In practical terms, this is the
     longest password sudo will support.

     The printf()-style function uses the same underlying mechanism as the conversation()
     function but only supports SUDO_CONV_INFO_MSG and SUDO_CONV_ERROR_MSG for the msg_type
     parameter.  It can be more convenient than using the conversation() function if no user
     reply is needed and supports standard printf() escape sequences.

     See the sample plugin for an example of the conversation() function usage.

   Plugin invocation order
     As of sudo 1.9.0, the plugin open() and close() functions are called in the following order:

     1.   audit open

     2.   policy open

     3.   approval open

     4.   approval close

     5.   I/O log open

     6.   command runs

     7.   command exits

     8.   I/O log close

     9.   policy close

     10.  audit close

     11.  sudo exits

     Prior to sudo 1.9.0, the I/O log close() function was called after the policy close()
     function.

   Sudoers group plugin API
     The sudoers plugin supports its own plugin interface to allow non-Unix group lookups.  This
     can be used to query a group source other than the standard Unix group database.  Two sample
     group plugins are bundled with sudo, group_file, and system_group, are detailed in
     sudoers(5).  Third party group plugins include a QAS AD plugin available from Quest
     Software.

     A group plugin must declare and populate a sudoers_group_plugin struct in the global scope.
     This structure contains pointers to the functions that implement plugin initialization,
     cleanup, and group lookup.

     struct sudoers_group_plugin {
         unsigned int version;
         int (*init)(int version, sudo_printf_t sudo_printf,
             char *const argv[]);
         void (*cleanup)(void);
         int (*query)(const char *user, const char *group,
             const struct passwd *pwd);
     };

     The sudoers_group_plugin struct has the following fields:

     version
           The version field should be set to GROUP_API_VERSION.

           This allows sudoers to determine the API version the group plugin was built against.

     init
           int (*init)(int version, sudo_printf_t plugin_printf,
               char *const argv[]);

           The init() function is called after sudoers has been parsed but before any policy
           checks.  It returns 1 on success, 0 on failure (or if the plugin is not configured),
           and -1 if a error occurred.  If an error occurs, the plugin may call the
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudoers allows the plugin to determine the major and
                 minor version number of the group plugin API supported by sudoers.

           plugin_printf
                 A pointer to a printf()-style function that may be used to display informational
                 or error message to the user.  Returns the number of characters printed on
                 success and -1 on failure.

           argv  A NULL-terminated array of arguments generated from the group_plugin option in
                 sudoers.  If no arguments were given, argv will be NULL.

     cleanup
           void (*cleanup)();

           The cleanup() function is called when sudoers has finished its group checks.  The
           plugin should free any memory it has allocated and close open file handles.

     query
           int (*query)(const char *user, const char *group,
               const struct passwd *pwd);

           The query() function is used to ask the group plugin whether user is a member of
           group.

           The function arguments are as follows:

           user  The name of the user being looked up in the external group database.

           group
                 The name of the group being queried.

           pwd   The password database entry for user, if any.  If user is not present in the
                 password database, pwd will be NULL.

     Group API Version Macros

     /* Sudoers group plugin version major/minor */
     #define GROUP_API_VERSION_MAJOR 1
     #define GROUP_API_VERSION_MINOR 0
     #define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \
                                GROUP_API_VERSION_MINOR)
     For getters and setters see the Policy plugin API.

PLUGIN API CHANGELOG

     The following revisions have been made to the Sudo Plugin API.

     Version 1.0
           Initial API version.

     Version 1.1 (sudo 1.8.0)
           The I/O logging plugin's open() function was modified to take the command_info list as
           an argument.

     Version 1.2 (sudo 1.8.5)
           The Policy and I/O logging plugins' open() functions are now passed a list of plugin
           parameters if any are specified in sudo.conf(5).

           A simple hooks API has been introduced to allow plugins to hook in to the system's
           environment handling functions.

           The init_session Policy plugin function is now passed a pointer to the user
           environment which can be updated as needed.  This can be used to merge in environment
           variables stored in the PAM handle before a command is run.

     Version 1.3 (sudo 1.8.7)
           Support for the exec_background entry has been added to the command_info list.

           The max_groups and plugin_dir entries were added to the settings list.

           The version() and close() functions are now optional.  Previously, a missing version()
           or close() function would result in a crash.  If no policy plugin close() function is
           defined, a default close() function will be provided by the sudo front-end that
           displays a warning if the command could not be executed.

           The sudo front-end now installs default signal handlers to trap common signals while
           the plugin functions are run.

     Version 1.4 (sudo 1.8.8)
           The remote_host entry was added to the settings list.

     Version 1.5 (sudo 1.8.9)
           The preserve_fds entry was added to the command_info list.

     Version 1.6 (sudo 1.8.11)
           The behavior when an I/O logging plugin returns an error (-1) has changed.
           Previously, the sudo front-end took no action when the log_ttyin(), log_ttyout(),
           log_stdin(), log_stdout(), or log_stderr() function returned an error.

           The behavior when an I/O logging plugin returns 0 has changed.  Previously, output
           from the command would be displayed to the terminal even if an output logging function
           returned 0.

     Version 1.7 (sudo 1.8.12)
           The plugin_path entry was added to the settings list.

           The debug_flags entry now starts with a debug file path name and may occur multiple
           times if there are multiple plugin-specific Debug lines in the sudo.conf(5) file.

     Version 1.8 (sudo 1.8.15)
           The sudoedit_checkdir and sudoedit_follow entries were added to the command_info list.
           The default value of sudoedit_checkdir was changed to true in sudo 1.8.16.

           The sudo conversation function now takes a pointer to a struct sudo_conv_callback as
           its fourth argument.  The sudo_conv_t definition has been updated to match.  The
           plugin must specify that it supports plugin API version 1.8 or higher to receive a
           conversation function pointer that supports this argument.

     Version 1.9 (sudo 1.8.16)
           The execfd entry was added to the command_info list.

     Version 1.10 (sudo 1.8.19)
           The umask entry was added to the user_info list.  The iolog_group, iolog_mode, and
           iolog_user entries were added to the command_info list.

     Version 1.11 (sudo 1.8.20)
           The timeout entry was added to the settings list.

     Version 1.12 (sudo 1.8.21)
           The change_winsize field was added to the io_plugin struct.

     Version 1.13 (sudo 1.8.26)
           The log_suspend field was added to the io_plugin struct.

     Version 1.14 (sudo 1.8.29)
           The umask_override entry was added to the command_info list.

     Version 1.15 (sudo 1.9.0)
           The cwd_optional entry was added to the command_info list.

           The event_alloc field was added to the policy_plugin and io_plugin structs.

           The errstr argument was added to the policy and I/O plugin functions which the plugin
           function can use to return an error string.  This string may be used by the audit
           plugin to report failure or error conditions set by the other plugins.

           The close() function is now is called regardless of whether or not a command was
           actually executed.  This makes it possible for plugins to perform cleanup even when a
           command was not run.

           SUDO_CONV_REPL_MAX has increased from 255 to 1023 bytes.

           Support for audit and approval plugins was added.

     Version 1.16 (sudo 1.9.3)
           Initial resource limit values were added to the user_info list.

           The cmnd_chroot and cmnd_cwd enties were added to the settings list.

     Version 1.17 (sudo 1.9.4)
           The event_alloc field was added to the audit_plugin and approval_plugin structs.

     Version 1.18 (sudo 1.9.9)
           The policy may now set resource limit values in the command_info list.

SEE ALSO

     sudo.conf(5), sudoers(5), sudo(8)

AUTHORS

     Many people have worked on sudo over the years; this version consists of code written
     primarily by:

           Todd C. Miller

     See the CONTRIBUTORS file in the sudo distribution (https://www.sudo.ws/contributors.html)
     for an exhaustive list of people who have contributed to sudo.

BUGS

     If you feel you have found a bug in sudo, please submit a bug report at
     https://bugzilla.sudo.ws/

SUPPORT

     Limited free support is available via the sudo-users mailing list, see
     https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.

DISCLAIMER

     sudo is provided “AS IS” and any express or implied warranties, including, but not limited
     to, the implied warranties of merchantability and fitness for a particular purpose are
     disclaimed.  See the LICENSE file distributed with sudo or https://www.sudo.ws/license.html
     for complete details.