| SUDO_PLUGIN(5) | File Formats Manual | SUDO_PLUGIN(5) |
sudo_plugin — Sudo
Plugin API
Starting with version 1.8, sudo supports a
plugin API for policy and session 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 plugin provides audit, security
policy and I/O logging capabilities. Via the plugin API,
sudo can be configured to use alternate 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.
A policy plugin must declare and populate a struct
policy_plugin 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 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 sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[], const char **errstr);
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[], const char **errstr);
int (*list)(int argc, char * const argv[], int verbose,
const char *user, const char **errstr);
int (*validate)(const char **errstr);
void (*invalidate)(int rmcred);
int (*init_session)(struct passwd *pwd, char **user_env[],
const char **errstr);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
struct sudo_plugin_event * (*event_alloc)(void);
};
A struct policy_plugin has the following fields:
SUDO_API_VERSION.
This allows sudo to determine the API
version the plugin was built against.
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[], const char **errstr);
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
sudo_plugin_printf()
function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
The function arguments are as follows:
sudo allows the
plugin to determine the major and minor version number of the plugin
API supported by sudo.conversation()
function that can be used by the plugin to interact with the user (see
Conversation API for
details). Returns 0 on success and -1 on failure.printf()-style function that
may be used to display informational or error messages (see
Conversation API for
details). Returns the number of characters printed on success and -1
on failure.sudo settings in the
form of “name=value” strings. The vector is terminated
by a NULL pointer. These settings correspond
to options the user specified when running
sudo. As such, they will only be present when
the corresponding option 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.
The following values may be set by
sudo:
-a option, to use on systems where
BSD authentication is supported.-C option 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.-R option. The plugin may ignore or
restrict the user's ability to specify a new root directory. Only
available starting with API version 1.16.-D option. The plugin may
ignore or restrict the user's ability to specify a new working
directory. Only available starting with API version 1.16.sudo and the
sudoers plugin is
subsystem@priority
but a plugin is free to use a different format so long as it does
not include a comma (‘,’).
Prior to sudo 1.8.12, there was no way to
specify plugin-specific debug_flags so the value
was always the same as that used by the
sudo front-end and did not include a path
name, only the flags themselves. As of version 1.7 of the plugin
interface, sudo will only pass
debug_flags if sudo.conf(5)
contains a plugin-specific Debug entry.-k
option along with a command, indicating that the user wishes to
ignore any cached authentication credentials.
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.sudo will pass the plugin the path to the
user's shell and set implied_shell.-c option.-i
option, indicating that the user wishes to run a login shell.:’), it is an IPv6
address, else it is IPv4.-n
option, 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.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.sudo
front-end. The path name will be a fully-qualified unless the
plugin was statically compiled into
sudo.-E
option, indicating that the user wishes to preserve the
environment.-P
option, indicating that the user wishes to preserve the group
vector instead of setting it based on the runas user.-p option.-h option. Support for running the
command on a remote host is meant to be implemented via a helper
program that is executed in place of the user-specified command.
The sudo front-end is only capable of
executing commands on the local host. Only available starting with
API version 1.4.-s
option, indicating that the user wishes to run a shell.-g option.-u option.-r option.-t option.-H
option. If true, set the HOME environment
variable to the target user's home directory.-e option 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.-T option. Not all plugins support command
timeouts and the ability of the user to set a timeout may be
restricted by policy. The format of the timeout string is
plugin-specific.-N
option, indicating that the user wishes to avoid updating any
cached authentication credentials. Only available starting with
API version 1.20.Additional settings may be added in the future so the plugin should silently ignore settings that it does not recognize.
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.
The following values may be set by
sudo:
sudo.sudo.sudo.sudo process is a member of. Only
available starting with API version 1.2.sudo
process. Only available starting with API version 1.2.sudo
process. Only available starting with API version 1.2.sudo process
or 0 if sudo is not part of a POSIX job
control session. Only available starting with API version
1.2.sudo
process or 0 if there is no terminal present. Only available
starting with API version 1.2.tty=’.sudo.sudo.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.
NULL-terminated array of strings. If no
arguments were specified, plugin_options will be
the NULL pointer.
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.
open()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
void (*close)(int exit_status, int error);
The
close()
function is called when sudo is finished,
shortly before it exits. Starting with API version 1.15,
close() is called regardless of whether or not a
command was actually executed. This makes it possible for plugins to
perform cleanup even when a command was not run. It is not possible to
tell whether a command was run based solely on the arguments passed to
the close() function. To determine if a command
was actually run, the plugin must keep track of whether or not the
check_policy() function returned
successfully.
The function arguments are as follows:
conversation()
or
sudo_plugin_printf()
function. If the command was successfully executed, the value of
error is zero.If no
close()
function is defined, no I/O logging plugins are loaded, and neither the
timeout nor 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.
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
sudo_plugin_printf() function using
SUDO_CONV_INFO_MSG. If the user requests
detailed version information, the verbose flag
will be non-zero.
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
int (*check_policy)(int argc, char * const argv[], char *env_add[],
char **command_info[], char **argv_out[], char **user_env_out[],
const char **errstr);
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 must
set
sudoedit=true
in the command_info list. The plugin is
responsible for choosing the editor to be used, potentially from a
variable in the user's environment, such as
EDITOR, and should be stored in
argv_out (environment variables may include
command line options). The files to be edited should be copied from
argv to 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
may also set sudoedit_nfiles to the number of files to
be edited in the command_info list; this will only
be used by the sudo front-end starting with API
version 1.21.
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
sudo_plugin_printf() function with
SUDO_CONF_ERROR_MSG to present additional error
information to the user.
The function arguments are as follows:
NULL pointer.NULL pointer.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.
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:
sudo will close all files
descriptors with a value of number or
higher.sudo is unable to change to
the new working directory, the command will not be run unless
cwd_optional is also set (see below).sudo will treat an inability to
change to the new working directory as a non-fatal error. This
setting has no effect unless
cwd is also
set.sudo runs a command as the
foreground process as long as sudo itself
is running in the foreground. When
exec_background is enabled and the command is
being run in a pseudo-terminal (due to I/O logging or the
use_pty setting), the command will be run as a
background process. Attempts to read from the controlling terminal
(or to change terminal settings) will result in the command being
suspended with the SIGTTIN signal (or
SIGTTOU in the case of terminal settings).
If this happens when sudo is a foreground
process, the command will be granted the controlling terminal and
resumed in the foreground with no user intervention required. The
advantage of initially running the command in the background is
that sudo need not read from the terminal
unless the command explicitly requests it. Otherwise, any terminal
input must be passed to the command, whether it has required it or
not (the kernel buffers terminals so it is not possible to tell
whether the command really wants the input). This is different
from historic sudo behavior or when the
command is not being run in a pseudo-terminal.
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,
macOS fails to restart the
tcgetattr()
and
tcsetattr()
system calls (this is a bug in macOS). Furthermore, because this
behavior depends on the command stopping with the
SIGTTIN or
SIGTTOU signals, programs 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-command
basis.
This setting has no effect unless I/O logging is enabled or use_pty is enabled.
sudo will use the
fexecve(2) system call to execute the command
instead of execve(2). The specified
number must refer to an open file
descriptor.sudo will intercept attempts to
execute a subsequent command and perform a policy check via the
policy plugin's
check_policy()
function to determine whether or not the command is permitted.
This can be used to prevent shell escapes on supported platforms
but it has a number of limitations. See Preventing
shell escapes in sudoers(5) for details.
Only available starting with API version 1.18.sudo will attempt to verify that a
command run in intercept mode has the expected path name, command
line arguments and environment. This setting has no effect unless
use_ptrace is also enabled. Only available
starting with API version 1.20.sudo will call the audit plugin's
accept() function to log when the command
runs a subsequent command, if supported by the system. If
intercept is also specified,
log_subcmds will be ignored. See
Preventing shell escapes in
sudoers(5) for more information. Only available
starting with API version 1.18.sudo will preserve the user's
group vector instead of initializing the group vector based on
runas_user.sudo front-end uses
runas_egid
and runas_gid when executing the command.sudo front-end uses
runas_euid and runas_uid when
executing the command.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.sudoedit. By default,
sudoedit 1.8.16 and higher will check all
directory components of the path to be edited for writability by
the invoking user. Symbolic links will not be followed in writable
directories and sudoedit will refuse to
edit a file located in a writable directory. These restrictions
are not enforced when sudoedit is run by
root. The sudoedit_checkdir option can be set to
false to disable this check. Only available starting with API
version 1.8.sudoedit to edit
files that are symbolic links. By default,
sudoedit 1.8.15 and higher will refuse to
open a symbolic link. The sudoedit_follow option
can be used to restore the older behavior and allow
sudoedit to open symbolic links. Only
available starting with API version 1.8.sudo front-end to
determine which elements of the argv_out
vector are files to be edited. The
‘--’ element must
immediately precede the first file to be editied. If
sudoedit_nfiles is not specified, the
sudo front-end will use the position of
the ‘--’ element to
determine where the file list begins. Only available starting with
API version 1.21.sudo will use
ptrace(2) to implement intercept mode if
supported by the system. This setting has no effect unless
intercept is also set. Only available starting
with API version 1.19.sudo will only run the command in a
pseudo-terminal when an I/O log plugin is loaded.sudo will base
the new entry on the invoking user's existing entry.Unsupported values will be ignored.
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.NULL-terminated environment vector to use
when executing the command. The plugin is responsible for allocating
and populating the vector.check_policy()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*list)(int argc, char * const argv[], int verbose,
const char *user, const char **errstr);
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
sudo_plugin_printf()
function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
Privileges should be output via the
conversation()
or
sudo_plugin_printf()
function using SUDO_CONV_INFO_MSG.
The function arguments are as follows:
NULL pointer.NULL, an
argument vector describing a command the user wishes to check against
the policy in the same form as what would be passed to the
execve(2) system call. If the command is permitted
by the policy, the fully-qualified path to the command should be
displayed along with any command line arguments.NULL, the plugin should list the
privileges of the invoking user.list()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*validate)(const char **errstr);
The
validate()
function is called when sudo is run with the
-v option. 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
sudo_plugin_printf()
function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
The function arguments are as follows:
validate()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
void (*invalidate)(int rmcred);
The
invalidate()
function is called when sudo is run with the
-k or -K option. For
policy plugins such as sudoers that cache
authentication credentials, this function will invalidate the
credentials. If the rmcred flag is non-zero, 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.
int (*init_session)(struct passwd *pwd, char **user_env[],
const char **errstr);
The
init_session()
function is called before sudo sets up the
execution environment for the command. It is run in the parent
sudo process before any user-ID or group-ID
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().
Returns 1 on success, 0 on failure, and -1
on error. On error, the plugin may optionally call the
conversation()
or
sudo_plugin_printf()
function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
The function arguments are as follows:
NULL.NULL-terminated environment vector to use
when executing the command. 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_out. The expected use
case is to merge the contents of the PAM environment (if any) with the
contents of user_env_out. The
user_env_out 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_out. Failure to
do so may result in a crash.init_session() function returns a value
other than 1, the plugin may store a message describing the failure or
error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
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 sudo_hook does
not match the front-end's major hook API version.
See the Hook function API section below for more information about hooks.
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.
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.
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.
struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc()
function is used to allocate a struct
sudo_plugin_event which provides access to the main
sudo event loop. Unlike the other fields, the
event_alloc pointer is filled in by the
sudo front-end, not by the plugin.
See the Event API section below for more information about events.
The
event_alloc()
function is only available starting with API version 1.15. If the
sudo front-end doesn't support API version 1.15
or higher, event_alloc will not be set.
/* Plugin API version major/minor. */
#define SUDO_API_VERSION_MAJOR 1
#define SUDO_API_VERSION_MINOR 13
#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_API_VERSION_SET_MINOR(vp, n) do { \
*(vp) = (*(vp) & 0xffff0000) | (n); \
} while(0)
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 sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const command_info[],
int argc, char * const argv[], char * const user_env[],
char * const plugin_options[], const char **errstr);
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,
const char **errstr);
int (*log_ttyout)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stdin)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stdout)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stderr)(const char *buf, unsigned int len,
const char **errstr);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
int (*change_winsize)(unsigned int lines, unsigned int cols,
const char **errstr);
int (*log_suspend)(int signo, const char **errstr);
struct sudo_plugin_event * (*event_alloc)(void);
};
When an I/O plugin is loaded, sudo runs
the command in a pseudo-terminal. 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 (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-terminal 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.
If a logging function returns an error (-1), the running command will be terminated and all of the plugin's logging functions will be disabled. Other I/O logging plugins will still receive any remaining input or output that has not yet been processed.
If an input logging function rejects the data by returning 0, the command will be terminated and the data will not be passed to the command, though it will still be sent to any other I/O logging plugins. If an output logging function rejects the data by returning 0, the command will be terminated and the data will not be written to the terminal, though it will still be sent to any other I/O logging plugins.
A struct audit_plugin has the following fields:
SUDO_IO_PLUGIN.SUDO_API_VERSION.
This allows sudo to determine the API
version the plugin was built against.
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const command_info[],
int argc, char * const argv[], char * const user_env[],
char * const plugin_options[]);
The
open()
function is run before the log_ttyin(),
log_ttyout(),
log_stdin(),
log_stdout(),
log_stderr(),
log_suspend(),
change_winsize(), or
show_version() functions are called. It is only
called if the version is being requested or if the policy plugin's
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
sudo_plugin_printf() function with
SUDO_CONF_ERROR_MSG to present additional error
information to the user.
The function arguments are as follows:
sudo allows the
plugin to determine the major and minor version number of the plugin
API supported by sudo.conversation()
function that may be used by the
Fa(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.printf()-style function that
may be used by the show_version() function to
display version information (see show_version below). The
sudo_plugin_printf() function may also be used
to display additional error message to the user. The
sudo_plugin_printf() function returns number
of characters printed on success and -1 on failure.sudo settings in the
form of “name=value” strings. The vector is terminated
by a NULL pointer. These settings correspond
to options the user specified when running
sudo. As such, they will only be present when
the corresponding option 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.
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.
NULL pointer.
When parsing command_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.
NULL pointer. It can be zero, such as
when sudo is called with the
-V option.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.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.
NULL-terminated array of strings. If no
arguments were specified, plugin_options will be
the NULL pointer.
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.
open()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
void (*close)(int exit_status, int error);
The
close()
function is called when sudo is finished,
shortly before it exits.
The function arguments are as follows:
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
sudo_plugin_printf() function using
SUDO_CONV_INFO_MSG. If the user requests
detailed version information, the verbose flag
will be non-zero.
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
int (*log_ttyin)(const char *buf, unsigned int len,
const char **errstr);
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 running command), or -1 if an error
occurred.
The function arguments are as follows:
log_ttyin()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*log_ttyout)(const char *buf, unsigned int len,
const char **errstr);
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 running command), or -1 if an
error occurred.
The function arguments are as follows:
log_ttyout()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*log_stdin)(const char *buf, unsigned int len,
const char **errstr);
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 running command), or
-1 if an error occurred.
The function arguments are as follows:
log_stdin()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*log_stdout)(const char *buf, unsigned int len,
const char **errstr);
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 running command), or -1 if an
error occurred.
The function arguments are as follows:
log_stdout()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*log_stderr)(const char *buf, unsigned int len,
const char **errstr);
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 running command), or -1 if an
error occurred.
The function arguments are as follows:
log_stderr()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
register_hooks().deregister_hooks().int (*change_winsize)(unsigned int lines, unsigned int cols,
const char **errstr);
The
change_winsize()
function is called whenever the window size of the terminal changes from
the initial values specified in the user_info
list. Returns -1 if an error occurred, in which case no further calls to
change_winsize() will be made,
The function arguments are as follows:
change_winsize()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
int (*log_suspend)(int signo, const char **errstr);
The
log_suspend()
function is called whenever a command is suspended or resumed. Logging
this information makes it possible to skip the period of time when the
command was suspended during playback of a session. Returns -1 if an
error occurred, in which case no further calls to
log_suspend() will be made,
The function arguments are as follows:
SIGCONT if the command was resumed.log_suspend()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.
The errstr parameter is only
available starting with API version 1.15. A plugin
must check the API version specified by the
sudo front-end before using
errstr. Failure to do so may result in a
crash.
struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc()
function is used to allocate a struct
sudo_plugin_event which provides access to the main
sudo event loop. Unlike the other fields,
the event_alloc() pointer is filled in by
the sudo front-end, not by the plugin.
See the Event API section below for more information about events.
The
event_alloc()
function is only available starting with API version 1.15. If the
sudo front-end doesn't support API version
1.15 or higher, event_alloc() will not be
set.
Same as for the Policy plugin API.
/* Audit plugin close function status types. */
#define SUDO_PLUGIN_NO_STATUS 0
#define SUDO_PLUGIN_WAIT_STATUS 1
#define SUDO_PLUGIN_EXEC_ERROR 2
#define SUDO_PLUGIN_SUDO_ERROR 3
#define SUDO_AUDIT_PLUGIN 3
struct audit_plugin {
unsigned int type; /* always SUDO_AUDIT_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
void (*close)(int status_type, int status);
int (*accept)(const char *plugin_name,
unsigned int plugin_type, char * const command_info[],
char * const run_argv[], char * const run_envp[],
const char **errstr);
int (*reject)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
int (*error)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
int (*show_version)(int verbose);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
struct sudo_plugin_event * (*event_alloc)(void);
}
An audit plugin can be used to log successful and unsuccessful
attempts to run sudo independent of the policy or
any I/O plugins. Multiple audit plugins may be specified in
sudo.conf(5).
A struct audit_plugin has the following fields:
SUDO_AUDIT_PLUGIN.SUDO_API_VERSION.
This allows sudo to determine the API
version the plugin was built against.
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
The audit
open()
function is run before any other sudo plugin API
functions. This makes it possible to audit failures in the other
plugins. 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:
sudo allows the
plugin to determine the major and minor version number of the plugin
API supported by sudo.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.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.sudo settings in the
form of “name=value” strings. The vector is terminated
by a NULL pointer. These settings correspond
to options the user specified when running
sudo. As such, they will only be present when
the corresponding option 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.
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.
-l or
-v options,
submit_argv[submit_optind]
will evaluate to the NULL pointer.sudo was invoked with,
including all command line options. The
submit_optind argument can be used to determine
the end of the command line options.NULL-terminated vector of
“name=value” strings.
When parsing submit_envp, the plugin
should split on the first equal sign
(‘=’) since the
name field will never include one itself but the
value might.
NULL-terminated array of strings. If no
arguments were specified, plugin_options will be
the NULL pointer.open()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.void (*close)(int status_type, int status);
The
close()
function is called when sudo is finished,
shortly before it exits.
The function arguments are as follows:
SUDO_PLUGIN_NO_STATUS,
SUDO_PLUGIN_WAIT_STATUS,
SUDO_PLUGIN_EXEC_ERROR or
SUDO_PLUGIN_SUDO_ERROR.sudo front-end.int (*accept)(const char *plugin_name, unsigned int plugin_type,
char * const command_info[], char * const run_argv[],
char * const run_envp[], const char **errstr);
The
accept()
function is called when a command or action is accepted by a policy or
approval plugin. The function arguments are as follows:
sudo
front-end.SUDO_POLICY_PLUGIN,
SUDO_POLICY_APPROVAL, or
SUDO_FRONT_END. The
accept() function is called multiple
times--once for each policy or approval plugin that succeeds and once
for the sudo front-end. When called on behalf of the sudo front-end,
command_info may include information from an I/O
logging plugin as well.
Typically, an audit plugin is interested in
either the accept status from the sudo
front-end or from the various policy and approval plugins, but not
both. It is possible for the policy plugin to accept a command that
is later rejected by an approval plugin, in which case the audit
plugin's
accept()
and reject() functions will
both
be called.
NULL pointer.
When parsing command_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.
NULL-terminated argument vector describing a
command that will be run in the same form as what would be passed to
the execve(2) system call.NULL-terminated vector of
“name=value” strings.
When parsing run_envp, the plugin
should split on the first equal sign
(‘=’) since the
name field will never include one itself but the
value might.
accept()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.int (*reject)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
The
reject()
function is called when a command or action is rejected by a plugin. The
function arguments are as follows:
SUDO_POLICY_PLUGIN,
SUDO_APPROVAL_PLUGIN, or
SUDO_IO_PLUGIN.
Unlike the
accept()
function, the reject() function is not
called on behalf of the sudo front-end.
NULL pointer.NULL pointer.
When parsing command_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.
reject()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.int (*error)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
The
error()
function is called when a plugin or the sudo
front-end returns an error. The function arguments are as follows:
sudo
front-end.SUDO_FRONT_END for the
sudo front-end.NULL pointer.NULL pointer.
When parsing command_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.
error()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.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.
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
register_hooks().deregister_hooks().struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc()
function is used to allocate a struct
sudo_plugin_event which provides access to the main
sudo event loop. Unlike the other fields, the
event_alloc pointer is filled in by the
sudo front-end, not by the plugin.
See the Event API section below for more information about events.
The
event_alloc()
function is only available starting with API version 1.17. If the
sudo front-end doesn't support API version 1.17
or higher, event_alloc() will not be set.
struct approval_plugin {
#define SUDO_APPROVAL_PLUGIN 4
unsigned int type; /* always SUDO_APPROVAL_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
void (*close)(void);
int (*check)(char * const command_info[], char * const run_argv[],
char * const run_envp[], const char **errstr);
int (*show_version)(int verbose);
};
An approval plugin can be used to apply extra
constraints after a command has been accepted by the policy plugin. Unlike
the other plugin types, it does not remain open until the command completes.
The plugin is opened before a call to
check() or
show_version() and closed shortly thereafter (audit
plugin functions must be called before the plugin is closed). Multiple
approval plugins may be specified in sudo.conf(5).
A struct approval_plugin has the following fields:
SUDO_APPROVAL_PLUGIN.SUDO_API_VERSION.
This allows sudo to determine the API
version the plugin was built against.
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
The approval
open()
function is run immediately before a call to the plugin's
check() or
show_version() functions. It is only called if
the version is being requested or if the policy plugin's
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:
sudo allows the
plugin to determine the major and minor version number of the plugin
API supported by sudo.conversation()
function that can be used by the plugin to interact with the user (see
Conversation API for
details). Returns 0 on success and -1 on failure.printf()-style function that
may be used to display informational or error messages (see
Conversation API for
details). Returns the number of characters printed on success and -1
on failure.sudo settings in the
form of “name=value” strings. The vector is terminated
by a NULL pointer. These settings correspond
to options the user specified when running
sudo. As such, they will only be present when
the corresponding option 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.
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.
-l or
-v options,
submit_argv[submit_optind]
will evaluate to the NULL pointer.sudo was invoked with,
including all command line options. The
submit_optind argument can be used to determine
the end of the command line options.NULL-terminated vector of
“name=value” strings.
When parsing submit_envp, the plugin
should split on the first equal sign
(‘=’) since the
name field will never include one itself but the
value might.
NULL-terminated array of strings. If no
arguments were specified, plugin_options will be
the NULL pointer.open()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.void (*close)(void);
The
close()
function is called after the approval plugin's
check() or
show_version() functions have been called. It
takes no arguments. The close() function is
typically used to perform plugin-specific cleanup, such as the freeing
of memory objects allocated by the plugin. If the plugin does not need
to perform any cleanup, close() may be set to
the NULL pointer.
int (*check)(char * const command_info[], char * const run_argv[],
char * const run_envp[], const char **errstr);
The approval
check()
function is run after the policy plugin
check_policy() function and before any I/O
logging plugins. If multiple approval plugins are loaded, they must all
succeed for the command to be allowed. 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:
NULL pointer.
When parsing command_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.
NULL-terminated argument vector describing a
command that will be run in the same form as what would be passed to
the execve(2) system call.NULL-terminated vector of
“name=value” strings.
When parsing run_envp, the plugin
should split on the first equal sign
(‘=’) since the
name field will never include one itself but the
value might.
open()
function returns a value other than 1, the plugin may store a message
describing the failure or error in errstr. The
sudo front-end will then pass this value to
any registered audit plugins. The string stored in
errstr must remain valid until the plugin's
close() function is called.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.
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
The sudo front-end installs default signal
handlers to trap common signals while the plugin functions are run. The
following signals are trapped by default before the command is executed:
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 logging of commands killed by a signal
for plugins that log such information in their
close() function. An exception to this is
SIGPIPE, which is ignored until the command is
executed.
A plugin may temporarily install its own signal handlers but must restore the original handler before the plugin function returns.
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 {
unsigned int hook_version;
unsigned int hook_type;
sudo_hook_fn_t hook_fn;
void *closure;
};
A struct sudo_hook has the following fields:
SUDO_HOOK_VERSION.SUDO_HOOK_SETENVtypedef 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_UNSETENVtypedef int (*sudo_hook_fn_unsetenv_t)(const char *name, void *closure);
SUDO_HOOK_GETENVtypedef 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_PUTENVtypedef int (*sudo_hook_fn_putenv_t)(char *string, void *closure);
If the registered hook does not match the typedef the results are unspecified.
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_ERRORSUDO_HOOK_RET_NEXTSUDO_HOOK_RET_NEXT if the specified variable
was not found in the private copy of the environment.SUDO_HOOK_RET_STOPCare must be taken when hooking C library functions, it is very easy to create an infinite loop. For example, a getenv(3) hook that calls the snprintf(3) function may create a loop if the snprintf(3) implementation calls getenv(3) to check the locale. To prevent this, you may wish to use a static variable in the hook function to guard against nested calls. For example:
static int in_progress = 0; /* avoid recursion */
if (in_progress)
return SUDO_HOOK_RET_NEXT;
in_progress = 1;
...
in_progress = 0;
return SUDO_HOOK_RET_STOP;
Hook API Version Macros
/* Hook API version major/minor */
#define SUDO_HOOK_VERSION_MAJOR 1
#define SUDO_HOOK_VERSION_MINOR 0
#define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
SUDO_HOOK_VERSION_MINOR)
For getters and setters see the Policy plugin API.
When sudo runs a command, it uses an event
loop to service signals and I/O. Events may be triggered based on time, a
file or socket descriptor becoming ready, or due to receipt of a signal.
Starting with API version 1.15, it is possible for a plugin to participate
in this event loop by calling the
event_alloc()
function.
Events are described by the following structure:
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure);
struct sudo_plugin_event {
int (*set)(struct sudo_plugin_event *pev, int fd, int events,
sudo_plugin_ev_callback_t callback, void *closure);
int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
int (*del)(struct sudo_plugin_event *pev);
int (*pending)(struct sudo_plugin_event *pev, int events,
struct timespec *ts);
int (*fd)(struct sudo_plugin_event *pev);
void (*setbase)(struct sudo_plugin_event *pev, void *base);
void (*loopbreak)(struct sudo_plugin_event *pev);
void (*free)(struct sudo_plugin_event *pev);
};
A struct sudo_plugin_event contains the following function pointers:
int (*set)(struct sudo_plugin_event *pev, int fd, int events,
sudo_plugin_ev_callback_t callback, void *closure);
The
set()
function takes the following arguments:
SUDO_PLUGIN_EV_TIMEOUTSUDO_PLUGIN_EV_READSUDO_PLUGIN_EV_WRITESUDO_PLUGIN_EV_PERSISTSUDO_PLUGIN_EV_SIGNALThe SUDO_PLUGIN_EV_PERSIST flag
may be ORed with any of the event types. It is also possible to OR
SUDO_PLUGIN_EV_READ and
SUDO_PLUGIN_EV_WRITE together to run the
callback when a descriptor is ready to be either read from or
written to. All other event values are mutually exclusive.
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what,
void *closure);
The function to call when an event is
triggered. The
callback()
function is run with the following arguments:
SUDO_PLUGIN_EV_READ and
SUDO_PLUGIN_EV_WRITE) or have an
associated timeout, what can be used to
determine why the callback was run.set() function.The
set()
function returns 1 on success, and -1 if a error occurred.
int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
The
add()
function adds the event pev to
sudo's event loop. The
event must have previously been initialized via the
set() function. If the
timeout argument is not NULL, it should specify a
(relative) timeout after which the event will be triggered if the main
event criteria has not been met. This is often used to implement an I/O
timeout where the event will fire if a descriptor is not ready within a
certain time period. If the event is already present in the event loop,
its timeout will be adjusted to match the new
value, if any.
The
add()
function returns 1 on success, and -1 if a error occurred.
int (*del)(struct sudo_plugin_event *pev);
The
del()
function deletes the event pev from
sudo's event loop.
Deleted events can be added back via the add()
function.
The
del()
function returns 1 on success, and -1 if a error occurred.
int (*pending)(struct sudo_plugin_event *pev, int events,
struct timespec *ts);
The
pending()
function can be used to determine whether one or more events is pending.
The events argument specifies which events to
check for. See the set() function for a list of
valid event types. If SUDO_PLUGIN_EV_TIMEOUT is
specified in events, the event has an associated
timeout and the ts pointer is non-NULL, it will be
filled in with the remaining time.
int (*fd)(struct sudo_plugin_event *pev);
The
fd()
function returns the descriptor or signal number associated with the
event pev.
void (*setbase)(struct sudo_plugin_event *pev, void *base);
The
setbase()
function sets the underlying event base for
pev to the specified value. This can be used to
move an event created via event_alloc() to a new
event loop allocated by sudo's event subsystem. If
base is NULL,
pev's event base is reset to the default value,
which corresponds to sudo's main event loop.
Using this function requires linking the plugin with the sudo_util
library. It is unlikely to be used outside of the
sudoers plugin.
void (*loopbreak)(struct sudo_plugin_event *pev);
The
loopbreak()
function causes sudo's
event loop to exit immediately and the running command to be
terminated.
void (*free)(struct sudo_plugin_event *pev);
The
free()
function deletes the event pev from the event loop
and frees the memory associated with it.
The sudo front-end does not support
running remote commands. 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
command.
For example, the policy plugin could utilize
ssh to perform remote command 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.
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.
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 terminal (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.
Conversation function structures
The conversation function takes as arguments pointers to the following structures:
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 */
#define SUDO_CONV_PREFER_TTY 0x2000 /* flag: use tty if possible */
int msg_type;
int timeout;
const char *msg;
};
#define SUDO_CONV_REPL_MAX 1023
struct sudo_conv_reply {
char *reply;
};
typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure);
struct sudo_conv_callback {
unsigned int version;
void *closure;
sudo_conv_callback_fn_t on_suspend;
sudo_conv_callback_fn_t on_resume;
};
Pointers to the
conversation()
and printf()-style functions are passed in to the
plugin's open() function when the plugin is
initialized. The following type definitions can be used in the declaration
of the open() function:
typedef int (*sudo_conv_t)(int num_msgs,
const struct sudo_conv_message msgs[],
struct sudo_conv_reply replies[], struct sudo_conv_callback *callback);
typedef int (*sudo_printf_t)(int msg_type, const char *fmt, ...);
To use the
conversation()
function, the plugin must pass an array of struct
sudo_conv_message and struct sudo_conv_reply.
There must be a struct sudo_conv_message and
struct sudo_conv_reply for each message in the
conversation, that is, both arrays must have the same number of elements.
Each struct sudo_conv_reply must have its
reply member initialized to
NULL. The struct
sudo_conv_callback pointer, if not NULL,
should contain function pointers to be called when the
sudo process is suspended and/or resumed during
conversation input. The on_suspend and
on_resume functions are called with the signal that
caused sudo to be suspended and the
closure pointer from the struct
sudo_conv_callback. These functions should return 0 on success and -1
on error. On error, the conversation will end and the conversation function
will return a value of -1. The intended use is to allow the plugin to
release resources, such as locks, that should not be held indefinitely while
suspended and then reacquire them when the process is resumed. The functions
are not actually invoked from within a signal handler.
The msg_type must be set to one of the following values:
SUDO_CONV_PROMPT_ECHO_OFFNULL.SUDO_CONV_PROMPT_ECHO_ONNULL.SUDO_CONV_ERROR_MSGSUDO_CONV_PREFER_TTY flag is set, in
which case it is written to the user's terminal if possible.SUDO_CONV_INFO_MSGSUDO_CONV_PREFER_TTY flag is set, in which
case it is written to the user's terminal if possible.SUDO_CONV_PROMPT_MASKNULL. This can be used to provide visual feedback
to the user while reading sensitive information that should not be
displayed.In addition to the above values, the following flag bits may also be set:
SUDO_CONV_PROMPT_ECHO_OKSUDO_CONV_PROMPT_ECHO_OFF or
SUDO_CONV_PROMPT_MASK. By default,
sudo will refuse to read input if the echo cannot
be disabled for those message types.SUDO_CONV_PREFER_TTYSUDO_CONV_ERROR_MSG
or SUDO_CONV_INFO_MSG, try to write the message to
the user's terminal. If the terminal is unavailable, the standard error or
standard output will be used, depending upon whether
SUDO_CONV_ERROR_MSG or
SUDO_CONV_INFO_MSG was used. The user's terminal
is always used when possible for input, this flag is only used for
output.The timeout in seconds until the prompt will wait for no more input. A zero value implies an infinite timeout.
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.
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.
As of sudo 1.9.0, the plugin
open() and close() functions
are called in the following order:
Prior to sudo 1.9.0, the I/O
log close()
function was called
after
the policy close() function.
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 Software.
A group plugin must declare and populate a struct sudoers_group_plugin 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_plugin_printf,
char *const argv[]);
void (*cleanup)(void);
int (*query)(const char *user, const char *group,
const struct passwd *pwd);
};
A struct sudoers_group_plugin has the following fields:
This allows sudoers to determine the
API version the group plugin was built against.
int (*init)(int version, sudo_printf_t sudo_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:
sudoers allows the
plugin to determine the major and minor version number of the group
plugin API supported by sudoers.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.NULL-terminated array of arguments generated
from the
group_plugin
option in sudoers. If no arguments were given,
argv will be NULL.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.
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:
NULL./* 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)
The following revisions have been made to the Sudo Plugin API.
open()
function was modified to take the command_info list
as an argument.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.
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.
sudo front-end took no action when
the
log_ttyin(),
log_ttyout(), log_stdin(),
log_stdout(), or
log_stderr() function returned an error.
The behavior when an I/O logging plugin returns 0 has changed. Previously, output from the command would be displayed to the terminal even if an output logging function returned 0.
The debug_flags entry now starts with a debug file path name and may occur multiple times if there are multiple plugin-specific Debug lines in the sudo.conf(5) file.
The sudo
conversation()
function now takes a pointer to a struct
sudo_conv_callback as its fourth argument. The
sudo_conv_t definition has been updated to match.
The plugin must specify that it supports plugin API version 1.8 or
higher to receive a conversation function pointer that supports this
argument.
change_winsize() function was added to
struct io_plugin.log_suspend() function was added to
struct io_plugin.The
event_alloc()
function was added to struct policy_plugin and
struct io_plugin.
The errstr argument was added to the policy and I/O plugin functions which the plugin function can use to return an error string. This string may be used by the audit plugin to report failure or error conditions set by the other plugins.
The
close()
function is now is called regardless of whether or not a command was
actually executed. This makes it possible for plugins to perform cleanup
even when a command was not run.
SUDO_CONV_REPL_MAX has increased from
255 to 1023 bytes.
Support for audit and approval plugins was added.
The cmnd_chroot and cmnd_cwd entries were added to the settings list.
event_alloc()
function was added to struct audit_plugin and
struct approval_plugin.Many people have worked on sudo over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS.md file in the sudo
distribution (https://www.sudo.ws/about/contributors/) for an exhaustive
list of people who have contributed to sudo.
If you believe you have found a bug in
sudo, you can submit a bug report at
https://bugzilla.sudo.ws/
Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.
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.md file distributed with
sudo or https://www.sudo.ws/about/license/ for
complete details.
| January 18, 2023 | Sudo 1.9.13p3 |