Provided by: sudo-ldap_1.8.3p1-1ubuntu3_amd64 bug

NAME

       sudo_plugin - Sudo Plugin API

DESCRIPTION

       Starting with version 1.8, sudo supports a plugin API for policy and session logging.  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 via the /etc/sudo.conf
       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.

   The sudo.conf File
       The /etc/sudo.conf file contains plugin configuration directives.  Currently, the only
       supported keyword is the Plugin directive, which causes a plugin plugin to be loaded.

       A Plugin line consists of the Plugin keyword, followed by the symbol_name and the path to
       the shared object containing the plugin.  The symbol_name is the name of the struct
       policy_plugin or struct io_plugin in the plugin shared object.  The path may be fully
       qualified or relative.  If not fully qualified it is relative to the /usr/libexec
       directory.  Any additional parameters after the path are ignored.  Lines that don't begin
       with Plugin or Path are silently ignored.

       The same shared object may contain multiple plugins, each with a different symbol name.
       The shared object file must be owned by uid 0 and only writable by its owner.  Because of
       ambiguities that arise from composite policies, only a single policy plugin may be
       specified.  This limitation does not apply to I/O plugins.

        #
        # Default /etc/sudo.conf file
        #
        # Format:
        #   Plugin plugin_name plugin_path
        #   Path askpass /path/to/askpass
        #
        # The plugin_path is relative to /usr/libexec unless
        #   fully qualified.
        # The plugin_name corresponds to a global symbol in the plugin
        #   that contains the plugin interface structure.
        #
        Plugin sudoers_policy sudoers.so
        Plugin sudoers_io sudoers.so

   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 /etc/sudo.conf 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[]);
            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);
        };

       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[]);

           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.

               debug_level=number
                   A numeric debug level, from 1-9, if specified via the -D flag.

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

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

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

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

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

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

               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 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.

               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.

               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.

               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.

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

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

               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.

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

               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.

               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.

               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.

               user=string
                   The name of the user invoking sudo.

               uid=uid_t
                   The real 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.

               cwd=string
                   The user's current working directory.

               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=.

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

               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.

           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.

       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() 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:

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

               runas_uid=uid
                   User ID to run the command as.

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

               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.

               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.

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

               cwd=string
                   The current working directory to change to when executing the command.

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

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

               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.

               umask=octal
                   The file creation mask to use 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.

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

               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.

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

               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.

               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.

               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.

               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() 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() 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);

           The init_session function is called when sudo sets up the execution environment for
           the command, immediately before the contents of the command_info list are applied
           (before the uid changes).  This can be used to do session setup that is not supported
           by command_info, such as opening the PAM 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.

           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.

       Version macros

        #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)

        #define SUDO_API_VERSION_MAJOR 1
        #define SUDO_API_VERSION_MINOR 0
        #define SUDO_API_VERSION ((SUDO_API_VERSION_MAJOR << 16) | \
                                  SUDO_API_VERSION_MINOR)

   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[], int argc, char * const argv[],
                        char * const user_env[]);
            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);
        };

       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[]);

           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() 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.

       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.

       Version macros

       Same as for the "Policy 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_PROMPT_ECHO_OK   0x1000 /* flag: allow echo if no tty */
            int msg_type;
            int timeout;
            const char *msg;
        };

        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 filled in to the struct sudo_conv_reply, if any.

       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.

   Sudoers Group Plugin API
       The sudoers module supports a plugin interface to allow non-Unix group lookups.  This can
       be used to query a group source other than the standard Unix group database.  A sample
       group plugin is bundled with sudo that implements file-based lookups.  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.

       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)

SEE ALSO

       sudoers(5), sudo(8)

BUGS

       If you feel you have found a bug in sudo, please submit a bug report at
       http://www.sudo.ws/sudo/bugs/

SUPPORT

       Limited free support is available via the sudo-workers mailing list, see
       http://www.sudo.ws/mailman/listinfo/sudo-workers 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
       http://www.sudo.ws/sudo/license.html for complete details.