NAME¶
sudo_plugin - Sudo Plugin API
DESCRIPTION¶
Starting with version 1.8,
sudo supports a plugin API for policy and
session logging. By default, the
sudoers policy plugin and an
associated I/O logging plugin are used. Via the plugin API,
sudo can be
configured to use alternate policy and/or I/O logging plugins provided by
third parties. The plugins to be used are specified via the
/etc/sudo.conf file.
The API is versioned with a major and minor number. The minor version number is
incremented when additions are made. The major number is incremented when
incompatible changes are made. A plugin should be check the version passed to
it and make sure that the major version matches.
The plugin API is defined by the sudo_plugin.h header file.
The sudo.conf File¶
The
/etc/sudo.conf file contains plugin configuration directives.
Currently, the only supported keyword is the Plugin directive, which causes a
plugin plugin to be loaded.
A Plugin line consists of the Plugin keyword, followed by the
symbol_name
and the
path to the shared object containing the plugin. The
symbol_name is the name of the struct policy_plugin or struct io_plugin
in the plugin shared object. The
path may be fully qualified or
relative. If not fully qualified it is relative to the
/usr/libexec
directory. Any additional parameters after the
path are passed as
options to the plugin's
open function. Lines that don't begin with
Plugin, Path, Debug or Set are silently ignored.
The same shared object may contain multiple plugins, each with a different
symbol name. The shared object file must be owned by uid 0 and only writable
by its owner. Because of ambiguities that arise from composite policies, only
a single policy plugin may be specified. This limitation does not apply to I/O
plugins.
#
# Default /etc/sudo.conf file
#
# Format:
# Plugin plugin_name plugin_path plugin_options ...
# Path askpass /path/to/askpass
# Path noexec /path/to/sudo_noexec.so
# Debug sudo /var/log/sudo_debug all@warn
# Set disable_coredump true
#
# The plugin_path is relative to /usr/libexec unless
# fully qualified.
# The plugin_name corresponds to a global symbol in the plugin
# that contains the plugin interface structure.
# The plugin_options are optional.
#
Plugin sudoers_policy sudoers.so
Plugin sudoers_io sudoers.so
Policy Plugin API¶
A policy plugin must declare and populate a policy_plugin struct in the global
scope. This structure contains pointers to the functions that implement the
sudo policy checks. The name of the symbol should be specified in
/etc/sudo.conf along with a path to the plugin so that
sudo can
load it.
struct policy_plugin {
#define SUDO_POLICY_PLUGIN 1
unsigned int type; /* always SUDO_POLICY_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[]);
void (*close)(int exit_status, int error);
int (*show_version)(int verbose);
int (*check_policy)(int argc, char * const argv[],
char *env_add[], char **command_info[],
char **argv_out[], char **user_env_out[]);
int (*list)(int argc, char * const argv[], int verbose,
const char *list_user);
int (*validate)(void);
void (*invalidate)(int remove);
int (*init_session)(struct passwd *pwd, char **user_env[]);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
};
The policy_plugin struct has the following fields:
- type
- The type field should always be set to
SUDO_POLICY_PLUGIN.
- version
- The version field should be set to SUDO_API_VERSION.
This allows sudo to determine the API version the plugin was built
against.
- open
-
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[]);
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if
there was a usage error. In the latter case, sudo will print a
usage message before it exits. If an error occurs, the plugin may
optionally call the conversation or plugin_printf function with
SUDO_CONF_ERROR_MSG to present additional error information to the user.
The function arguments are as follows:
- version
- The version passed in by sudo allows the plugin to
determine the major and minor version number of the plugin API supported
by sudo.
- conversation
- A pointer to the conversation function that can be used by
the plugin to interact with the user (see below). Returns 0 on success and
-1 on failure.
- plugin_printf
- A pointer to a printf-style function that may be used to
display informational or error messages (see below). Returns the number of
characters printed on success and -1 on failure.
- settings
- A vector of user-supplied sudo settings in the form
of "name=value" strings. The vector is terminated by a NULL
pointer. These settings correspond to flags the user specified when
running sudo. As such, they will only be present when the
corresponding flag has been specified on the command line.
When parsing settings, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
- debug_flags=string
- A comma-separated list of debug flags that correspond to
sudo's Debug entry in /etc/sudo.conf, if there is one. The
flags are passed to the plugin as they appear in /etc/sudo.conf.
The syntax used by sudo and the sudoers plugin is
subsystem@ priority but the plugin is free to use a
different format so long as it does not include a command ,.
For reference, the priorities supported by the sudo front end and
sudoers are: crit, err, warn, notice,
diag, info, trace and debug.
The following subsystems are defined: main, memory,
args, exec, pty, utmp, conv,
pcomm, util, list, netif, audit,
edit, selinux, ldap, match, parser,
alias, defaults, auth, env, logging,
nss, rbtree, perms, plugin. The subsystem
all includes every subsystem.
There is not currently a way to specify a set of debug flags specific to the
plugin--the flags are shared by sudo and the plugin.
- debug_level=number
- This setting has been deprecated in favor of
debug_flags.
- runas_user=string
- The user name or uid to to run the command as, if specified
via the -u flag.
- runas_group=string
- The group name or gid to to run the command as, if
specified via the -g flag.
- prompt=string
- The prompt to use when requesting a password, if specified
via the -p flag.
- set_home=bool
- Set to true if the user specified the -H flag. If true, set
the HOME environment variable to the target user's home directory.
- preserve_environment=bool
- Set to true if the user specified the -E flag, indicating
that the user wishes to preserve the environment.
- run_shell=bool
- Set to true if the user specified the -s flag, indicating
that the user wishes to run a shell.
- login_shell=bool
- Set to true if the user specified the -i flag, indicating
that the user wishes to run a login shell.
- implied_shell=bool
- If the user does not specify a program on the command line,
sudo will pass the plugin the path to the user's shell and set
implied_shell to true. This allows sudo with no arguments to
be used similarly to su(1). If the plugin does not to support this
usage, it may return a value of -2 from the check_policy function, which
will cause sudo to print a usage message and exit.
- preserve_groups=bool
- Set to true if the user specified the -P flag, indicating
that the user wishes to preserve the group vector instead of setting it
based on the runas user.
- ignore_ticket=bool
- Set to true if the user specified the -k flag along with a
command, indicating that the user wishes to ignore any cached
authentication credentials.
- noninteractive=bool
- Set to true if the user specified the -n flag, indicating
that sudo should operate in non-interactive mode. The plugin may
reject a command run in non-interactive mode if user interaction is
required.
- login_class=string
- BSD login class to use when setting resource limits and
nice value, if specified by the -c flag.
- selinux_role=string
- SELinux role to use when executing the command, if
specified by the -r flag.
- selinux_type=string
- SELinux type to use when executing the command, if
specified by the -t flag.
- bsdauth_type=string
- Authentication type, if specified by the -a flag, to use on
systems where BSD authentication is supported.
- network_addrs=list
- A space-separated list of IP network addresses and netmasks
in the form "addr/netmask", e.g.
"192.168.1.2/255.255.255.0". The address and netmask pairs may
be either IPv4 or IPv6, depending on what the operating system supports.
If the address contains a colon (':'), it is an IPv6 address, else it is
IPv4.
- progname=string
- The command name that sudo was run as, typically
"sudo" or "sudoedit".
- sudoedit=bool
- Set to true when the -e flag is is specified or if invoked
as sudoedit. The plugin shall substitute an editor into argv
in the check_policy function or return -2 with a usage error if the
plugin does not support sudoedit. For more information, see the
check_policy section.
- closefrom=number
- If specified, the user has requested via the -C flag that
sudo close all files descriptors with a value of number or
higher. The plugin may optionally pass this, or another value, back in the
command_info list.
Additional settings may be added in the future so the plugin should silently
ignore settings that it does not recognize.
- user_info
- A vector of information about the user running the command
in the form of "name=value" strings. The vector is terminated by
a NULL pointer.
When parsing user_info, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
- pid=int
- The process ID of the running sudo process. Only
available starting with API version 1.2
- ppid=int
- The parent process ID of the running sudo process.
Only available starting with API version 1.2
- sid=int
- The session ID of the running sudo process or 0 if
sudo is not part of a POSIX job control session. Only available
starting with API version 1.2
- pgid=int
- The ID of the process group that the running sudo
process belongs to. Only available starting with API version 1.2
- tcpgid=int
- The ID of the forground process group associated with the
terminal device associcated with the sudo process or -1 if there is
no terminal present. Only available starting with API version 1.2
- user=string
- The name of the user invoking sudo.
- euid=uid_t
- The effective user ID of the user invoking
sudo.
- uid=uid_t
- The real user ID of the user invoking sudo.
- egid=gid_t
- The effective group ID of the user invoking
sudo.
- gid=gid_t
- The real group ID of the user invoking sudo.
- groups=list
- The user's supplementary group list formatted as a string
of comma-separated group IDs.
- cwd=string
- The user's current working directory.
- tty=string
- The path to the user's terminal device. If the user has no
terminal device associated with the session, the value will be empty, as
in tty=.
- host=string
- The local machine's hostname as returned by the
gethostname() system call.
- lines=int
- The number of lines the user's terminal supports. If there
is no terminal device available, a default value of 24 is used.
- cols=int
- The number of columns the user's terminal supports. If
there is no terminal device available, a default value of 80 is used.
- user_env
- The user's environment in the form of a NULL-terminated
vector of "name=value" strings.
When parsing user_env, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
- plugin_options
- Any (non-comment) strings immediately after the plugin path
are treated as arguments to the plugin. These arguments are split on a
white space boundary and are passed to the plugin in the form of a
NULL-terminated array of strings. If no arguments were specified,
plugin_options will be the NULL pointer.
NOTE: the plugin_options parameter is only available starting with
API version 1.2. A plugin must check the API version specified by
the sudo front end before using plugin_options. Failure to
do so may result in a crash.
- close
-
void (*close)(int exit_status, int error);
The close function is called when the command being run by sudo
finishes.
The function arguments are as follows:
- exit_status
- The command's exit status, as returned by the
wait(2) system call. The value of exit_status is undefined if error
is non-zero.
- error
- If the command could not be executed, this is set to the
value of errno set by the execve(2) system call. The plugin is
responsible for displaying error information via the conversation or
plugin_printf function. If the command was successfully executed, the
value of error is 0.
- show_version
-
int (*show_version)(int verbose);
The show_version function is called by sudo when the user specifies
the -V option. The plugin may display its version information to the user
via the conversation or plugin_printf function using SUDO_CONV_INFO_MSG.
If the user requests detailed version information, the verbose flag will
be set.
- check_policy
-
int (*check_policy)(int argc, char * const argv[]
char *env_add[], char **command_info[],
char **argv_out[], char **user_env_out[]);
The check_policy function is called by sudo to determine
whether the user is allowed to run the specified commands.
If the sudoedit option was enabled in the settings array
passed to the open function, the user has requested sudoedit
mode. sudoedit is a mechanism for editing one or more files where
an editor is run with the user's credentials instead of with elevated
privileges. sudo achieves this by creating user-writable temporary
copies of the files to be edited and then overwriting the originals with
the temporary copies after editing is complete. If the plugin supports
sudoedit, it should choose the editor to be used, potentially from
a variable in the user's environment, such as EDITOR, and include it in
argv_out (note that environment variables may include command line
flags). The files to be edited should be copied from argv into
argv_out, separated from the editor and its arguments by a
"--" element. The "--" will be removed by sudo
before the editor is executed. The plugin should also set
sudoedit=true in the command_info list.
The check_policy function returns 1 if the command is allowed, 0 if
not allowed, -1 for a general error, or -2 for a usage error or if
sudoedit was specified but is unsupported by the plugin. In the
latter case, sudo will print a usage message before it exits. If an
error occurs, the plugin may optionally call the conversation or
plugin_printf function with SUDO_CONF_ERROR_MSG to present additional
error information to the user.
The function arguments are as follows:
- argc
- The number of elements in argv, not counting the
final NULL pointer.
- argv
- The argument vector describing the command the user wishes
to run, in the same form as what would be passed to the execve()
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, char **user_envp[);
The init_session function is called before sudo sets up the execution
environment for the command. It is run in the parent sudo process
and before any uid or gid changes. This can be used to perform session
setup that is not supported by command_info, such as opening the
PAM session. The close function can be used to tear down the session that
was opened by init_session.
The pwd argument points to a passwd struct for the user the command
will be run as if the uid the command will run as was found in the
password database, otherwise it will be NULL.
The user_env argument points to the environment the command will run
in, in the form of a NULL-terminated vector of "name=value"
strings. This is the same string passed back to the front end via the
Policy Plugin's user_env_out parameter. If the init_session
function needs to modify the user environment, it should update the
pointer stored in user_env. The expected use case is to merge the
contents of the PAM environment (if any) with the contents of
user_env. NOTE: the user_env parameter is only available
starting with API version 1.2. A plugin must check the API version
specified by the sudo front end before using user_env.
Failure to do so may result in a crash.
Returns 1 on success, 0 on failure and -1 on error. On error, the plugin may
optionally call the conversation or plugin_printf function with
SUDO_CONF_ERROR_MSG to present additional error information to the
user.
- register_hooks
-
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
The register_hooks function is called by the sudo front end to register any
hooks the plugin needs. If the plugin does not support hooks,
register_hooks should be set to the NULL pointer.
The version argument describes the version of the hooks API supported
by the sudo front end.
The register_hook function should be used to register any supported hooks
the plugin needs. It returns 0 on success, 1 if the hook type is not
supported and -1 if the major version in struct hook does not match the
front end's major hook API version.
See the "Hook Function API" section below for more information
about hooks.
NOTE: the register_hooks function is only available starting with API
version 1.2. If the sudo front end doesn't support API version 1.2
or higher, register_hooks will not be called.
- deregister_hooks
-
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
The deregister_hooks function is called by the sudo front end to deregister
any hooks the plugin has registered. If the plugin does not support hooks,
deregister_hooks should be set to the NULL pointer.
The version argument describes the version of the hooks API supported
by the sudo front end.
The deregister_hook function should be used to deregister any hooks that
were put in place by the register_hook function. If the plugin tries to
deregister a hook that the front end does not support, deregister_hook
will return an error.
See the "Hook Function API" section below for more information
about hooks.
NOTE: the deregister_hooks function is only available starting with API
version 1.2. If the sudo front end doesn't support API version 1.2
or higher, deregister_hooks will not be called.
Policy Plugin Version Macros
/* Plugin API version major/minor. */
#define SUDO_API_VERSION_MAJOR 1
#define SUDO_API_VERSION_MINOR 2
#define SUDO_API_MKVERSION(x, y) ((x << 16) | y)
#define SUDO_API_VERSION SUDO_API_MKVERSION(SUDO_API_VERSION_MAJOR,\
SUDO_API_VERSION_MINOR)
/* Getters and setters for API version */
#define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
#define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
#define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \
*(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
} while(0)
#define SUDO_VERSION_SET_MINOR(vp, n) do { \
*(vp) = (*(vp) & 0xffff0000) | (n); \
} while(0)
I/O Plugin API¶
struct io_plugin {
#define SUDO_IO_PLUGIN 2
unsigned int type; /* always SUDO_IO_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation
sudo_printf_t plugin_printf, char * const settings[],
char * const user_info[], int argc, char * const argv[],
char * const user_env[], char * const plugin_options[]);
void (*close)(int exit_status, int error); /* wait status or error */
int (*show_version)(int verbose);
int (*log_ttyin)(const char *buf, unsigned int len);
int (*log_ttyout)(const char *buf, unsigned int len);
int (*log_stdin)(const char *buf, unsigned int len);
int (*log_stdout)(const char *buf, unsigned int len);
int (*log_stderr)(const char *buf, unsigned int len);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
};
When an I/O plugin is loaded,
sudo runs the command in a pseudo-tty. This
makes it possible to log the input and output from the user's session. If any
of the standard input, standard output or standard error do not correspond to
a tty,
sudo will open a pipe to capture the I/O for logging before
passing it on.
The log_ttyin function receives the raw user input from the terminal device
(note that this will include input even when echo is disabled, such as when a
password is read). The log_ttyout function receives output from the pseudo-tty
that is suitable for replaying the user's session at a later time. The
log_stdin, log_stdout and log_stderr functions are only called if the standard
input, standard output or standard error respectively correspond to something
other than a tty.
Any of the logging functions may be set to the NULL pointer if no logging is to
be performed. If the open function returns 0, no I/O will be sent to the
plugin.
The io_plugin struct has the following fields:
- type
- The type field should always be set to SUDO_IO_PLUGIN
- version
- The version field should be set to SUDO_API_VERSION.
This allows sudo to determine the API version the plugin was built
against.
- open
-
int (*open)(unsigned int version, sudo_conv_t conversation
sudo_printf_t plugin_printf, char * const settings[],
char * const user_info[], int argc, char * const argv[],
char * const user_env[], char * const plugin_options[]);
The open function is run before the log_input,
log_output or show_version functions are called. It is only
called if the version is being requested or the check_policy
function has returned successfully. It returns 1 on success, 0 on failure,
-1 if a general error occurred, or -2 if there was a usage error. In the
latter case, sudo will print a usage message before it exits. If an
error occurs, the plugin may optionally call the conversation or
plugin_printf function with SUDO_CONF_ERROR_MSG to present additional
error information to the user.
The function arguments are as follows:
- version
- The version passed in by sudo allows the plugin to
determine the major and minor version number of the plugin API supported
by sudo.
- conversation
- A pointer to the conversation function that may be used by
the show_version function to display version information (see
show_version below). The conversation function may also be used to display
additional error message to the user. The conversation function returns 0
on success and -1 on failure.
- plugin_printf
- A pointer to a printf-style function that may be used by
the show_version function to display version information (see
show_version below). The plugin_printf function may also be used to
display additional error message to the user. The plugin_printf function
returns number of characters printed on success and -1 on failure.
- settings
- A vector of user-supplied sudo settings in the form
of "name=value" strings. The vector is terminated by a NULL
pointer. These settings correspond to flags the user specified when
running sudo. As such, they will only be present when the
corresponding flag has been specified on the command line.
When parsing settings, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
See the "Policy Plugin API" section for a list of all possible
settings.
- user_info
- A vector of information about the user running the command
in the form of "name=value" strings. The vector is terminated by
a NULL pointer.
When parsing user_info, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
See the "Policy Plugin API" section for a list of all possible
strings.
- argc
- The number of elements in argv, not counting the
final NULL pointer.
- argv
- If non-NULL, an argument vector describing a command the
user wishes to run in the same form as what would be passed to the
execve() system call.
- user_env
- The user's environment in the form of a NULL-terminated
vector of "name=value" strings.
When parsing user_env, the plugin should split on the first
equal sign ('=') since the name field will never include one itself
but the value might.
- plugin_options
- Any (non-comment) strings immediately after the plugin path
are treated as arguments to the plugin. These arguments are split on a
white space boundary and are passed to the plugin in the form of a
NULL-terminated array of strings. If no arguments were specified,
plugin_options will be the NULL pointer.
NOTE: the plugin_options parameter is only available starting with
API version 1.2. A plugin must check the API version specified by
the sudo front end before using plugin_options. Failure to
do so may result in a crash.
- close
-
void (*close)(int exit_status, int error);
The close function is called when the command being run by sudo
finishes.
The function arguments are as follows:
- exit_status
- The command's exit status, as returned by the
wait(2) system call. The value of exit_status is undefined if error
is non-zero.
- error
- If the command could not be executed, this is set to the
value of errno set by the execve(2) system call. If the command was
successfully executed, the value of error is 0.
- show_version
-
int (*show_version)(int verbose);
The show_version function is called by sudo when the user specifies
the -V option. The plugin may display its version information to the user
via the conversation or plugin_printf function using SUDO_CONV_INFO_MSG.
If the user requests detailed version information, the verbose flag will
be set.
- log_ttyin
-
int (*log_ttyin)(const char *buf, unsigned int len);
The log_ttyin function is called whenever data can be read from the
user but before it is passed to the running command. This allows the
plugin to reject data if it chooses to (for instance if the input contains
banned content). Returns 1 if the data should be passed to the command, 0
if the data is rejected (which will terminate the command) or -1 if an
error occurred.
The function arguments are as follows:
- buf
- The buffer containing user input.
- len
- The length of buf in bytes.
- log_ttyout
-
int (*log_ttyout)(const char *buf, unsigned int len);
The log_ttyout function is called whenever data can be read from the
command but before it is written to the user's terminal. This allows the
plugin to reject data if it chooses to (for instance if the output
contains banned content). Returns 1 if the data should be passed to the
user, 0 if the data is rejected (which will terminate the command) or -1
if an error occurred.
The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- log_stdin
-
int (*log_stdin)(const char *buf, unsigned int len);
The log_stdin function is only used if the standard input does not
correspond to a tty device. It is called whenever data can be read from
the standard input but before it is passed to the running command. This
allows the plugin to reject data if it chooses to (for instance if the
input contains banned content). Returns 1 if the data should be passed to
the command, 0 if the data is rejected (which will terminate the command)
or -1 if an error occurred.
The function arguments are as follows:
- buf
- The buffer containing user input.
- len
- The length of buf in bytes.
- log_stdout
-
int (*log_stdout)(const char *buf, unsigned int len);
The log_stdout function is only used if the standard output does not
correspond to a tty device. It is called whenever data can be read from
the command but before it is written to the standard output. This allows
the plugin to reject data if it chooses to (for instance if the output
contains banned content). Returns 1 if the data should be passed to the
user, 0 if the data is rejected (which will terminate the command) or -1
if an error occurred.
The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- log_stderr
-
int (*log_stderr)(const char *buf, unsigned int len);
The log_stderr function is only used if the standard error does not
correspond to a tty device. It is called whenever data can be read from
the command but before it is written to the standard error. This allows
the plugin to reject data if it chooses to (for instance if the output
contains banned content). Returns 1 if the data should be passed to the
user, 0 if the data is rejected (which will terminate the command) or -1
if an error occurred.
The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- register_hooks
- See the "Policy Plugin API" section for a
description of register_hooks.
- deregister_hooks
- See the "Policy Plugin API" section for a
description of deregister_hooks.
I/O Plugin Version Macros
Same as for the "Policy Plugin API".
Hook Function API¶
Beginning with plugin API version 1.2, it is possible to install hooks for
certain functions called by the
sudo front end.
Currently, the only supported hooks relate to the handling of environment
variables. Hooks can be used to intercept attempts to get, set, or remove
environment variables so that these changes can be reflected in the version of
the environment that is used to execute a command. A future version of the API
will support hooking internal
sudo front end functions as well.
Hook structure
Hooks in
sudo are described by the following structure:
typedef int (*sudo_hook_fn_t)();
struct sudo_hook {
int hook_version;
int hook_type;
sudo_hook_fn_t hook_fn;
void *closure;
};
The sudo_hook structure has the following fields:
- hook_version
- The hook_version field should be set to
SUDO_HOOK_VERSION.
- hook_type
- The hook_type field may be one of the following supported
hook types:
- SUDO_HOOK_SETENV
- The C library setenv() function. Any registered hooks will
run before the C library implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_setenv_t)(const char *name,
const char *value, int overwrite, void *closure);
If the registered hook does not match the typedef the results are
unspecified.
- SUDO_HOOK_UNSETENV
- The C library unsetenv() function. Any registered hooks
will run before the C library implementation. The hook_fn field should be
a function that matches the following typedef:
typedef int (*sudo_hook_fn_unsetenv_t)(const char *name,
void *closure);
- SUDO_HOOK_GETENV
- The C library getenv() 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() function. Any registered hooks will
run before the C library implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_putenv_t)(char *string,
void *closure);
If the registered hook does not match the typedef the results are
unspecified.
- hook_fn
-
sudo_hook_fn_t hook_fn;
The hook_fn field should be set to the plugin's hook implementation. The
actual function arguments will vary depending on the hook_type (see
hook_type above). In all cases, the closure field of struct sudo_hook is
passed as the last function parameter. This can be used to pass arbitrary
data to the plugin's hook implementation.
The function return value may be one of the following:
- SUDO_HOOK_RET_ERROR
- The hook function encountered an error.
- SUDO_HOOK_RET_NEXT
- The hook completed without error, go on to the next hook
(including the native implementation if applicable). For example, a getenv
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 hook that calls the snprintf function may
create a loop if the snprintf implementation calls getenv to check the locale.
To prevent this, you may wish to use a static variable in the hook function to
guard against nested calls. E.g.
static int in_progress = 0; /* avoid recursion */
if (in_progress)
return SUDO_HOOK_RET_NEXT;
in_progress = 1;
...
in_progress = 0;
return SUDO_HOOK_RET_STOP;
Hook API Version Macros
/* Hook API version major/minor */
#define SUDO_HOOK_VERSION_MAJOR 1
#define SUDO_HOOK_VERSION_MINOR 0
#define SUDO_HOOK_MKVERSION(x, y) ((x << 16) | y)
#define SUDO_HOOK_VERSION SUDO_HOOK_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
SUDO_HOOK_VERSION_MINOR)
/* Getters and setters for hook API version */
#define SUDO_HOOK_VERSION_GET_MAJOR(v) ((v) >> 16)
#define SUDO_HOOK_VERSION_GET_MINOR(v) ((v) & 0xffff)
#define SUDO_HOOK_VERSION_SET_MAJOR(vp, n) do { \
*(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
} while(0)
#define SUDO_HOOK_VERSION_SET_MINOR(vp, n) do { \
*(vp) = (*(vp) & 0xffff0000) | (n); \
} while(0)
Conversation API¶
If the plugin needs to interact with the user, it may do so via the conversation
function. A plugin should not attempt to read directly from the standard input
or the user's tty (neither of which are guaranteed to exist). The caller must
include a trailing newline in msg if one is to be printed.
A printf-style function is also available that can be used to display
informational or error messages to the user, which is usually more convenient
for simple messages where no use input is required.
struct sudo_conv_message {
#define SUDO_CONV_PROMPT_ECHO_OFF 0x0001 /* do not echo user input */
#define SUDO_CONV_PROMPT_ECHO_ON 0x0002 /* echo user input */
#define SUDO_CONV_ERROR_MSG 0x0003 /* error message */
#define SUDO_CONV_INFO_MSG 0x0004 /* informational message */
#define SUDO_CONV_PROMPT_MASK 0x0005 /* mask user input */
#define SUDO_CONV_DEBUG_MSG 0x0006 /* debugging message */
#define SUDO_CONV_PROMPT_ECHO_OK 0x1000 /* flag: allow echo if no tty */
int msg_type;
int timeout;
const char *msg;
};
struct sudo_conv_reply {
char *reply;
};
typedef int (*sudo_conv_t)(int num_msgs,
const struct sudo_conv_message msgs[],
struct sudo_conv_reply replies[]);
typedef int (*sudo_printf_t)(int msg_type, const char *fmt, ...);
Pointers to the conversation and printf-style functions are passed in to the
plugin's open function when the plugin is initialized.
To use the conversation function, the plugin must pass an array of
sudo_conv_message and sudo_conv_reply structures. There must be a struct
sudo_conv_message and struct sudo_conv_reply for each message in the
conversation. The plugin is responsible for freeing the reply buffer filled in
to the struct sudo_conv_reply, if any.
The printf-style function uses the same underlying mechanism as the conversation
function but only supports SUDO_CONV_INFO_MSG, SUDO_CONV_ERROR_MSG and
SUDO_CONV_DEBUG_MSG for the
msg_type parameter. It can be more
convenient than using the conversation function if no user reply is needed and
supports standard
printf() escape sequences.
Unlike, SUDO_CONV_INFO_MSG and SUDO_CONV_ERROR_MSG, messages sent with the
<SUDO_CONV_DEBUG_MSG>
msg_type are not directly user-visible.
Instead, they are logged to the file specified in the Debug statement (if any)
in the
/etc/sudo.conf file. This allows a plugin to log debugging
information and is intended to be used in conjunction with the
debug_flags setting.
See the sample plugin for an example of the conversation function usage.
Sudoers Group Plugin API¶
The
sudoers module supports a plugin interface to allow non-Unix group
lookups. This can be used to query a group source other than the standard Unix
group database. A sample group plugin is bundled with
sudo that
implements file-based lookups. Third party group plugins include a QAS AD
plugin available from Quest Software.
A group plugin must declare and populate a sudoers_group_plugin struct in the
global scope. This structure contains pointers to the functions that implement
plugin initialization, cleanup and group lookup.
struct sudoers_group_plugin {
unsigned int version;
int (*init)(int version, sudo_printf_t sudo_printf,
char *const argv[]);
void (*cleanup)(void);
int (*query)(const char *user, const char *group,
const struct passwd *pwd);
};
The sudoers_group_plugin struct has the following fields:
- version
- The version field should be set to GROUP_API_VERSION.
This allows sudoers to determine the API version the group plugin was
built against.
- init
-
int (*init)(int version, sudo_printf_t plugin_printf,
char *const argv[]);
The init function is called after sudoers has been parsed but
before any policy checks. It returns 1 on success, 0 on failure (or if the
plugin is not configured), and -1 if a error occurred. If an error occurs,
the plugin may call the plugin_printf function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
The function arguments are as follows:
- version
- The version passed in by sudoers allows the plugin
to determine the major and minor version number of the group plugin API
supported by sudoers.
- plugin_printf
- A pointer to a printf-style function that may be used to
display informational or error message to the user. Returns the number of
characters printed on success and -1 on failure.
- argv
- A NULL-terminated array of arguments generated from the
group_plugin option in sudoers. If no arguments were given,
argv will be NULL.
- cleanup
-
void (*cleanup)();
The cleanup function is called when sudoers has finished its
group checks. The plugin should free any memory it has allocated and close
open file handles.
- query
-
int (*query)(const char *user, const char *group,
const struct passwd *pwd);
The query function is used to ask the group plugin whether
user is a member of group.
The function arguments are as follows:
- user
- The name of the user being looked up in the external group
database.
- group
- The name of the group being queried.
- pwd
- The password database entry for user, if any. If
user is not present in the password database, pwd will be
NULL.
Group API Version Macros
/* Sudoers group plugin version major/minor */
#define GROUP_API_VERSION_MAJOR 1
#define GROUP_API_VERSION_MINOR 0
#define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \
GROUP_API_VERSION_MINOR)
/* Getters and setters for group version */
#define GROUP_API_VERSION_GET_MAJOR(v) ((v) >> 16)
#define GROUP_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
#define GROUP_API_VERSION_SET_MAJOR(vp, n) do { \
*(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
} while(0)
#define GROUP_API_VERSION_SET_MINOR(vp, n) do { \
*(vp) = (*(vp) & 0xffff0000) | (n); \
} while(0)
PLUGIN API CHANGELOG¶
The following revisions have been made to the Sudo Plugin API.
- Version 1.0
- Initial API version.
- Version 1.1
- The I/O logging plugin's open function was modified to take
the command_info list as an argument.
- Version 1.2
- The Policy and I/O logging plugins' open functions are now
passed a list of plugin options if any are specified in
/etc/sudo.conf.
A simple hooks API has been introduced to allow plugins to hook in to the
system's environment handling functions.
The init_session Policy plugin function is now passed a pointer to the user
environment which can be updated as needed. This can be used to merge in
environment variables stored in the PAM handle before a command is
run.
SEE ALSO¶
sudoers(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.