Sudo Plugin API

NAME

sudo_plugin - Sudo Plugin API

DESCRIPTION

Starting with version 1.8, sudo supports a plugin API for policy and session logging. By default, the sudoers policy plugin and an associated I/O logging plugin are used. Via the plugin API, sudo can be configured to use alternate policy and/or I/O logging plugins provided by third parties. The plugins to be used are specified via the /etc/sudo.conf file.

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

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

The sudo.conf File

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

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

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

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

Policy Plugin API

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

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

The policy_plugin struct has the following fields:

type

The type field should always be set to SUDO_POLICY_PLUGIN.

version

The version field should be set to SUDO_API_VERSION.

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

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

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

The function arguments are as follows:

version

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

conversation

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

plugin_printf

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

settings

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

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

debug_level=number

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

runas_user=string

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

runas_group=string

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

prompt=string

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

set_home=bool

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

preserve_environment=bool

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

run_shell=bool

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

login_shell=bool

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

implied_shell=bool

If the user does not specify a program on the command line, sudo will pass the plugin the path to the user's shell and set implied_shell to true. This allows sudo with no arguments to be used similarly to su(1). If the plugin does not to support this usage, it may return a value of -2 from the check_policy function, which will cause sudo to print a usage message and exit.

preserve_groups=bool

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

ignore_ticket=bool

Set to true if the user specified the -k flag along with a command, indicating that the user wishes to ignore any cached authentication credentials.

noninteractive=bool

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

login_class=string

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

selinux_role=string

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

selinux_type=string

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

bsdauth_type=string

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

network_addrs=list

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

progname=string

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

sudoedit=bool

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

closefrom=number

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

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

user_info

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

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

user=string

The name of the user invoking sudo.

uid=uid_t

The real user ID of the user invoking sudo.

gid=gid_t

The real group ID of the user invoking sudo.

groups=list

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

cwd=string

The user's current working directory.

tty=string

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

host=string

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

lines=int

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

cols=int

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

user_env

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

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

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

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

The function arguments are as follows:

exit_status

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

error

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

show_version
 int (*show_version)(int verbose);

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

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

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

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

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

The function arguments are as follows:

argc

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

argv

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

env_add

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

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

command_info

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

command=string

Fully qualified path to the command to be executed.

runas_uid=uid

User ID to run the command as.

runas_euid=uid

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

runas_gid=gid

Group ID to run the command as.

runas_egid=gid

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

runas_groups=list

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

login_class=string

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

preserve_groups=bool

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

cwd=string

The current working directory to change to when executing the command.

noexec=bool

If set, prevent the command from executing other programs.

chroot=string

The root directory to use when running the command.

nice=int

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

umask=octal

The file creation mask to use when executing the command.

selinux_role=string

SELinux role to use when executing the command.

selinux_type=string

SELinux type to use when executing the command.

timeout=int

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

sudoedit=bool

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

closefrom=number

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

iolog_compress=bool

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

iolog_path=string

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

iolog_stdin=bool

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

iolog_stdout=bool

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

iolog_stderr=bool

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

iolog_ttyin=bool

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

iolog_ttyout=bool

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

use_pty=bool

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

set_utmp=bool

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

utmp_user=string

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

Unsupported values will be ignored.

argv_out

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

user_env_out

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

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

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

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

verbose

Flag indicating whether to list in verbose mode or not.

list_user

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

argc

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

argv

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

validate
 int (*validate)(void);

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

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

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

invalidate
 void (*invalidate)(int remove);

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

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

init_session
 int (*init_session)(struct passwd *pwd);

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

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

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

Version macros

 \#define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
 #define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
 #define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \
     *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
 } while(0)
 #define SUDO_VERSION_SET_MINOR(vp, n) do { \
     *(vp) = (*(vp) & 0xffff0000) | (n); \
 } while(0)

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

I/O Plugin API

 struct io_plugin {
 #define SUDO_IO_PLUGIN                2
     unsigned int type; /* always SUDO_IO_PLUGIN */
     unsigned int version; /* always SUDO_API_VERSION */
     int (*open)(unsigned int version, sudo_conv_t conversation
                 sudo_printf_t plugin_printf, char * const settings[],
                 char * const user_info[], int argc, char * const argv[],
                 char * const user_env[]);
     void (*close)(int exit_status, int error); /* wait status or error */
     int (*show_version)(int verbose);
     int (*log_ttyin)(const char *buf, unsigned int len);
     int (*log_ttyout)(const char *buf, unsigned int len);
     int (*log_stdin)(const char *buf, unsigned int len);
     int (*log_stdout)(const char *buf, unsigned int len);
     int (*log_stderr)(const char *buf, unsigned int len);
 };

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

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

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

The io_plugin struct has the following fields:

type

The type field should always be set to SUDO_IO_PLUGIN

version

The version field should be set to SUDO_API_VERSION.

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

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

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

The function arguments are as follows:

version

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

conversation

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

plugin_printf

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

settings

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

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

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

user_info

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

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

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

argc

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

argv

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

user_env

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

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

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

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

The function arguments are as follows:

exit_status

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

error

If the command could not be executed, this is set to the value of errno set by the execve(2) system call. If the command was successfully executed, the value of error is 0.

show_version
 int (*show_version)(int verbose);

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

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

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

The function arguments are as follows:

buf

The buffer containing user input.

len

The length of buf in bytes.

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

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

The function arguments are as follows:

buf

The buffer containing command output.

len

The length of buf in bytes.

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

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

The function arguments are as follows:

buf

The buffer containing user input.

len

The length of buf in bytes.

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

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

The function arguments are as follows:

buf

The buffer containing command output.

len

The length of buf in bytes.

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

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

The function arguments are as follows:

buf

The buffer containing command output.

len

The length of buf in bytes.

Version macros

Same as for the Policy Plugin API.

Conversation API

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

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

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

 struct sudo_conv_reply {
     char *reply;
 };

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

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

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

To use the conversation function, the plugin must pass an array of sudo_conv_message and sudo_conv_reply structures. There must be a struct sudo_conv_message and struct sudo_conv_reply for each message in the conversation. The plugin is responsible for freeing the reply buffer filled in to the struct sudo_conv_reply, if any.

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

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

Sudoers Group Plugin API

The sudoers module supports a plugin interface to allow non-Unix group lookups. This can be used to query a group source other than the standard Unix group database. A sample group plugin is bundled with sudo that implements file-based lookups. Third party group plugins include a QAS AD plugin available from Quest Software.

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

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

The sudoers_group_plugin struct has the following fields:

version

The version field should be set to GROUP_API_VERSION.

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

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

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

The function arguments are as follows:

version

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

plugin_printf

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

argv

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

cleanup
 void (*cleanup)();

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

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

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

The function arguments are as follows:

user

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

group

The name of the group being queried.

pwd

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

Version Macros

 /* Sudoers group plugin version major/minor */
 #define GROUP_API_VERSION_MAJOR 1
 #define GROUP_API_VERSION_MINOR 0
 #define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \
                            GROUP_API_VERSION_MINOR)

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

SEE ALSO

sudoers(5), sudo(8)

BUGS

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

SUPPORT

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

DISCLAIMER

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