sudo_plugin

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

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

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

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

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

     The policy_plugin struct has the following fields:

     type  The type field should always be set to SUDO_POLICY_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           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 sup-
                 ported 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 fail-
                 ure.

           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 speci-
                 fied when running sudo.  As such, they will only be present
                 when the corresponding flag has been specified on the command
                 line.

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

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

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

                 debug_flags=string
                       A comma-separated list of debug flags that correspond
                       to sudo's Debug entry in sudo.conf(5), if there is one.
                       The flags are passed to the plugin as they appear in
                       sudo.conf(5).  The syntax used by sudo and the sudoers
                       plugin is subsystem@priority but the plugin is free to
                       use a different format so long as it does not include a
                       comma (',').  There is not currently a way to specify a
                       set of debug flags specific to the plugin--the flags
                       are shared by sudo and the plugin.
                       of -2 from the check_policy() function, which will
                       cause sudo to print a usage message and exit.

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

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

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

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

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

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

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

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

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

                 progname=string
                       The command name that sudo was run as, typically
                       ``sudo'' or ``sudoedit''.
                       able starting with API version 1.4.

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

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

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

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

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

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

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

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

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

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

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

                 cwd=string
                       The user's current working directory.
                       string of comma-separated group IDs.

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

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

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

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

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

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

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

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

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

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

                 itself but the value might.

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

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

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2) system
                 call.  The value of exit_status is undefined if error is non-
                 zero.

           error
                 If the command could not be executed, this is set to the
                 value of errno set by the execve(2) system call.  The plugin
                 is responsible for displaying error information via the
                 conversation() or plugin_printf() function.  If the command
                 was successfully executed, the value of error is 0.

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

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user speci-
           fies 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 edi-
           tor 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, poten-
           tially from a variable in the user's environment, such as EDITOR,
           and include it in argv_out (note that environment variables may
           additional error information to the user.

           The function arguments are as follows:

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

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

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

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

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

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

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

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

                 cwd=string
                       The current working directory to change to when execut-
                       ing the command.

                 exec_background=bool
                       By default, sudo runs a command as the foreground
                       process as long as sudo itself is running in the fore-
                       ground.  When exec_background is enabled and the com-
                       mand is being run in a pty (due to I/O logging or the
                       use_pty setting), the command will be run as a back-
                       ground process.  Attempts to read from the controlling
                       terminal (or to change terminal settings) will result
                       in the command being suspended with the SIGTTIN signal
                       being run in a pty.

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

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

                 iolog_compress=bool
                       Set to true if the I/O logging plugins, if any, should
                       compress the log data.  This is a hint to the I/O log-
                       ging 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 ter-
                       minal 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 ter-
                       minal 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

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

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

                 noexec=bool
                       If set, prevent the command from executing other pro-
                       grams.

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

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

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

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

                 runas_gid=gid
                       Group ID to run the command as.

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

                 runas_uid=uid
                       User ID to run the command as.

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

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

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

                 umask=octal
                       The file creation mask to use when executing the com-
                       mand.

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

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

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

           credentials, this function will validate and cache the credentials.

           The validate() function should be NULL if the plugin does not sup-
           port 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 authen-
           tication credentials, this function will invalidate the creden-
           tials.  If the remove flag is set, the plugin may remove the cre-
           dentials 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 exe-
           cution 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 speci-
           fied 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
           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 sup-
           ported 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
         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 ses-
     sion.  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 out-
     put 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() func-
     tions 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 ver-
           sion is being requested or the check_policy() function has returned
           successfully.  It returns 1 on success, 0 on failure, -1 if a gen-
           eral error occurred, or -2 if there was a usage error.  In the lat-
           ter 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 addi-
           tional error information 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 speci-
                 fied 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 vec-
                 tor 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

     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 com-
                 mand 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 speci-
           fies 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 termi-
           nate the command) or -1 if an error occurred.

           The function arguments are as follows:
           (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 out-
           put.  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

     o   SIGTSTP
     o   SIGUSR1
     o   SIGUSR2

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

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

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

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

     Hook structure

     Hooks in sudo are described by the following structure:

     typedef int (*sudo_hook_fn_t)();

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

     The sudo_hook structure has the following fields:

     hook_version
           The hook_version field should be set to SUDO_HOOK_VERSION.

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

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

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

           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 implementa-
           tion.  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 implementa-
           tion.

           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
     Hook API Version Macros

     /* Hook API version major/minor */
     #define SUDO_HOOK_VERSION_MAJOR 1
     #define SUDO_HOOK_VERSION_MINOR 0
     #define SUDO_HOOK_MKVERSION(x, y) ((x << 16) | y)
     #define SUDO_HOOK_VERSION SUDO_HOOK_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
                                                   SUDO_HOOK_VERSION_MINOR)

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

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

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

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

   Conversation API
     If the plugin needs to interact with the user, it may do so via the
     conversation() function.  A plugin should not attempt to read directly
     from the standard input or the user's tty (neither of which are guaran-
     teed 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 conve-
     nient 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 */

     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 con-
     versation.  The plugin is responsible for freeing the reply buffer
     located in each struct sudo_conv_reply, if it is not NULL.
     SUDO_CONV_REPL_MAX represents the maximum length of the reply buffer (not
     including the trailing NUL character).  In practical terms, this is the
     longest password sudo will support.  It is also useful as a maximum value
     for the memset_s() function when clearing passwords filled in by the con-
     versation function.

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

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

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

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

     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 {

           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() func-
           tion with SUDO_CONF_ERROR_MSG to present additional error informa-
           tion to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudoers allows the plugin to deter-
                 mine 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 fail-
                 ure.

           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.

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

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

     Version 1.0
           Initial API version.

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

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

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

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

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

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

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

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

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

     Version 1.5 (sudo 1.8.9)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2018 Hurricane Electric. All Rights Reserved.