Provided by: sudo-ldap_1.8.9p5-1ubuntu1.4_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 policy plugin
     and an associated I/O logging plugin are used.  Via the plugin API, sudo can be configured
     to use alternate policy and/or I/O logging 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[]);
         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[]);
         int (*list)(int argc, char * const argv[], int verbose,
                     const char *list_user);
         int (*validate)(void);
         void (*invalidate)(int remove);
         int (*init_session)(struct passwd *pwd, char **user_env[]);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
     };

     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[]);

           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 below).  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 below).  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 flags
                 the user specified when running sudo.  As such, they will only be present when
                 the corresponding flag 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.

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

                 closefrom=number
                       If specified, the user has requested via the -C flag 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.

                 debug_flags=string
                       A comma-separated list of debug flags that correspond to sudo's Debug
                       entry in sudo.conf(5), if there is one.  The flags are passed to the
                       plugin as they appear in sudo.conf(5).  The syntax used by sudo and the
                       sudoers plugin is subsystem@priority but the plugin is free to use a
                       different format so long as it does not include a comma (‘,’).  There is
                       not currently a way to specify a set of debug flags specific to the
                       plugin--the flags are shared by sudo and the plugin.

                 debug_level=number
                       This setting has been deprecated in favor of debug_flags.

                 ignore_ticket=bool
                       Set to true if the user specified the -k flag 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 flag.

                 login_shell=bool
                       Set to true if the user specified the -i flag, 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 flag, 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.

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

                 preserve_groups=bool
                       Set to true if the user specified the -P flag, 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
                       flag.

                 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 flag, indicating that the user
                       wishes to run a shell.

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

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

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

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

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

                 sudoedit=bool
                       Set to true when the -e flag is 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.

                 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.

                 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.

                 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.

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

                 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 -1 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.

                 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.

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

           The close() function is called when the command being run by sudo finishes.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2) system call.  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 0.

           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.

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

           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 flags).  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.

                 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 pty (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 pty.

                       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, Mac OS X fails to restart the tcgetattr() and tcsetattr() system
                       calls (this is a bug in Mac OS X).  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.

                 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_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.

                 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_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.

                 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-tty 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.

                 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.

                 use_pty=bool
                       Allocate a pseudo-tty 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
                       pty 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.

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

           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,

           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.

           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.

     validate
           int (*validate)(void);

           The validate() function is called when sudo is run with the -v flag.  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.

     invalidate
           void (*invalidate)(int remove);

           The invalidate() function is called when sudo is called with the -k or -K flag.  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_envp[);

           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 uid or gid
           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 uid the command will run as was found in the password database, otherwise it will
           be NULL.

           The user_env 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.  The expected use case is to merge the contents of the PAM
           environment (if any) with the contents of user_env.  NOTE: the user_env 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.  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.

     Policy Plugin Version Macros

     /* Plugin API version major/minor. */
     #define SUDO_API_VERSION_MAJOR 1
     #define SUDO_API_VERSION_MINOR 2
     #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_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[]);
         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);
         int (*log_ttyout)(const char *buf, unsigned int len);
         int (*log_stdin)(const char *buf, unsigned int len);
         int (*log_stdout)(const char *buf, unsigned int len);
         int (*log_stderr)(const char *buf, unsigned int len);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
     };

     When an I/O plugin is loaded, sudo runs the command in a pseudo-tty.  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-tty 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.

     The io_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[], int argc, char * const argv[],
                       char * const user_env[], char * const plugin_options[]);

           The open() function is run before the log_input(), log_output() or show_version()
           functions are called.  It is only called if the version is being requested or the
           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 flags
                 the user specified when running sudo.  As such, they will only be present when
                 the corresponding flag 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.

           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 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.

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

           The close() function is called when the command being run by sudo finishes.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2) system call.  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 0.

     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.

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

           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
           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.

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

           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
           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.

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

           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
           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.

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

           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 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.

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

           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 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.

     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.

     I/O Plugin Version Macros

     Same as for the Policy plugin API.

   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
        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.

     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 {
         int hook_version;
         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 native
                 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 native 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_MKVERSION(x, y) ((x << 16) | y)
     #define SUDO_HOOK_VERSION SUDO_HOOK_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
                                                   SUDO_HOOK_VERSION_MINOR)

     /* Getters and setters for hook API version */
     #define SUDO_HOOK_VERSION_GET_MAJOR(v) ((v) >> 16)
     #define SUDO_HOOK_VERSION_GET_MINOR(v) ((v) & 0xffff)
     #define SUDO_HOOK_VERSION_SET_MAJOR(vp, n) do { \
         *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
     } while(0)
     #define SUDO_HOOK_VERSION_SET_MINOR(vp, n) do { \
         *(vp) = (*(vp) & 0xffff0000) | (n); \
     } while(0)

   Remote command execution
     The sudo front end does not have native support for 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.

     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_DEBUG_MSG        0x0006 /* debugging message */
     #define SUDO_CONV_PROMPT_ECHO_OK   0x1000 /* flag: allow echo if no tty */
         int msg_type;
         int timeout;
         const char *msg;
     };

     #define SUDO_CONV_REPL_MAX      255

     struct sudo_conv_reply {
         char *reply;
     };

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

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

     Pointers to the conversation() and printf()-style functions are passed in to the plugin's
     open() function when the plugin is initialized.

     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.  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.  It is also useful as a maximum value for the memset_s() function when clearing
     passwords filled in by the conversation function.

     The printf()-style function uses the same underlying mechanism as the conversation()
     function but only supports SUDO_CONV_INFO_MSG, SUDO_CONV_ERROR_MSG and SUDO_CONV_DEBUG_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.

     Unlike, SUDO_CONV_INFO_MSG and Dv SUDO_CONV_ERROR_MSG , messages sent with the
     SUDO_CONV_DEBUG_MSG msg_type are not directly user-visible.  Instead, they are logged to the
     file specified in the Debug statement (if any) in the sudo.conf(5).  file.  This allows a
     plugin to log debugging information and is intended to be used in conjunction with the
     debug_flags setting.

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

   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)

     /* Getters and setters for group version */
     #define GROUP_API_VERSION_GET_MAJOR(v) ((v) >> 16)
     #define GROUP_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
     #define GROUP_API_VERSION_SET_MAJOR(vp, n) do { \
         *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
     } while(0)
     #define GROUP_API_VERSION_SET_MINOR(vp, n) do { \
         *(vp) = (*(vp) & 0xffff0000) | (n); \
     } while(0)

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)