SUDO_PLUGIN(4)                Programmer's Manual               SUDO_PLUGIN(4)

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.  The
     primary keyword is the Plugin directive, which causes a 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/local/libexec directory.  Any
     additional parameters after the path are passed as options to the
     plugin's open() function.  Lines that don't begin with Plugin, Path,
     Debug or Set 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 plugin_options ...
     #   Path askpass /path/to/askpass
     #   Path noexec /path/to/sudo_noexec.so
     #   Debug sudo /var/log/sudo_debug all@warn
     #   Set disable_coredump true
     #
     # The plugin_path is relative to /usr/local/libexec unless
     #   fully qualified.
     # The plugin_name corresponds to a global symbol in the plugin
     #   that contains the plugin interface structure.
     # The plugin_options are optional.
     #
     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[],
                     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.

                 debug_flags=string
                       A comma-separated list of debug flags that correspond
                       to sudo's Debug entry in /etc/sudo.conf, if there is
                       one.  The flags are passed to the plugin as they appear
                       in /etc/sudo.conf.  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 (`,').

                       For reference, the priorities supported by the sudo
                       front end and sudoers are: crit, err, warn, notice,
                       diag, info, trace and debug.

                       The following subsystems are defined: main, memory,
                       args, exec, pty, utmp, conv, pcomm, util, list, netif,
                       audit, edit, selinux, ldap, match, parser, alias,
                       defaults, auth, env, logging, nss, rbtree, perms,
                       plugin.  The subsystem all includes every subsystem.

                       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.

                 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.

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

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

                 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

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

                 tcpgid=int
                       The ID of the forground process group associated with
                       the terminal device associcated with the sudo process
                       or -1 if there is no terminal present.  Only available
                       starting with API version 1.2

                 user=string
                       The name of the user invoking sudo.

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

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

                 egid=gid_t
                       The effective group 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(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.

                 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.

           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.  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(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:

                 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(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[], 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.

   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)

   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;
     };

     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,
     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 /etc/sudo.conf

     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 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.

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

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

           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.

SEE ALSO
     sudoers(4), sudo(1m)

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-users mailing list, see
     http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the
     archives.

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

Sudo 1.8.6                       July 16, 2012                      Sudo 1.8.6
