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
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 in the sudo.conf(5) file.
The API is versioned with a major and minor number. The minor
version number is incremented when additions are made. The major
number is incremented when incompatible changes are made. A plugin
should be check the version passed to it and make sure that the
major version matches.
The plugin API is defined by the sudo_plugin.h header file.
Policy plugin API
A policy plugin must declare and populate a policy_plugin struct in
the global scope. This structure contains pointers to the
functions that implement the sudo policy checks. The name of the
symbol should be 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 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 *list_user, const char **errstr);
int (*validate)(const char **errstr);
void (*invalidate)(int remove);
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);
};
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[], 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 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
Conversation API for details). 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
Conversation API for details). 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 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:
bsdauth_type=string
Authentication type, if specified by the -a
option, to use on systems where BSD
authentication is supported.
closefrom=number
If specified, the user has requested via the -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.
cmnd_chroot=string
The root directory (see chroot(2)) to run the
command in, as specified by the user via the -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.
cmnd_cwd=string
The working directory to run the command in, as
specified by the user via the -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.
debug_flags=string
A debug file path name followed by a space and a
comma-separated list of debug flags that
correspond to the plugin's Debug entry in
sudo.conf(5), if there is one. The flags are
passed to the plugin exactly as they appear in
sudo.conf(5). The syntax used by 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.
ignore_ticket=bool
Set to true if the user specified the -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.
implied_shell=bool
If the user does not specify a program on the
command line, sudo will pass the plugin the path
to the user's shell and set
login_class=string
BSD login class to use when setting resource
limits and nice value, if specified by the -c
option.
login_shell=bool
Set to true if the user specified the -i option,
indicating that the user wishes to run a login
shell.
max_groups=int
The maximum number of groups a user may belong
to. This will only be present if there is a
corresponding setting in sudo.conf(5).
network_addrs=list
A space-separated list of IP network addresses
and 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.
noninteractive=bool
Set to true if the user specified the -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.
plugin_dir=string
The default plugin directory used by the sudo
front end. This is the default directory set at
compile time and may not correspond to the
directory the running plugin was loaded from. It
may be used by a plugin to locate support files.
plugin_path=string
The path name of plugin loaded by the sudo front
end. The path name will be a fully-qualified
unless the plugin was statically compiled into
sudo.
preserve_environment=bool
Set to true if the user specified the -E option,
indicating that the user wishes to preserve the
environment.
preserve_groups=bool
Set to true if the user specified the -P option,
indicating that the user wishes to preserve the
group vector instead of setting it based on the
runas user.
progname=string
The command name that sudo was run as, typically
'sudo' or 'sudoedit'.
prompt=string
The prompt to use when requesting a password, if
specified via the -p option.
remote_host=string
The name of the remote host to run the command
on, if specified via the -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.
run_shell=bool
Set to true if the user specified the -s option,
indicating that the user wishes to run a shell.
runas_group=string
The group name or gid to run the command as, if
specified via the -g option.
runas_user=string
The user name or uid to run the command as, if
specified via the -u option.
selinux_role=string
SELinux role to use when executing the command,
if specified by the -r option.
selinux_type=string
SELinux type to use when executing the command,
if specified by the -t option.
set_home=bool
Set to true if the user specified the -H option.
If true, set the HOME environment variable to the
target user's home directory.
sudoedit=bool
Set to true when the -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.
timeout=string
Command timeout specified by the user via the -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.
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.
The following values may be set by sudo:
cols=int
The number of columns the user's terminal
supports. If there is no terminal device
available, a default value of 80 is used.
cwd=string
The user's current working directory.
egid=gid_t
The effective group-ID of the user invoking sudo.
euid=uid_t
The effective user-ID of the user invoking sudo.
gid=gid_t
The real group-ID of the user invoking sudo.
groups=list
The user's supplementary group list formatted as
a string of comma-separated group-IDs.
host=string
The local machine's hostname as returned by the
gethostname(2) system call.
lines=int
The number of lines the user's terminal supports.
If there is no terminal device available, a
default value of 24 is used.
pgid=int
The ID of the process group that the running sudo
process is a member of. Only available starting
with API version 1.2.
pid=int
The process ID of the running sudo process. Only
available starting with API version 1.2.
ppid=int
The parent process ID of the running sudo
process. Only available starting with API
version 1.2.
rlimit_as=soft,hard
The maximum size to which the process's address
space may grow (in bytes), if supported by the
operating system. The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_core=soft,hard
The largest size core dump file that may be
created (in bytes). The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_cpu=soft,hard
The maximum amount of CPU time that the process
may use (in seconds). The soft and hard limits
are separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_data=soft,hard
The maximum size of the data segment for the
process (in bytes). The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_fsize=soft,hard
The largest size file that the process may create
(in bytes). The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_locks=soft,hard
The maximum number of locks that the process may
establish, if supported by the operating system.
The soft and hard limits are separated by a
comma. A value of 'infinity' indicates that
there is no limit. Only available starting with
API version 1.16.
rlimit_memlock=soft,hard
The maximum size that the process may lock in
memory (in bytes), if supported by the operating
system. The soft and hard limits are separated
by a comma. A value of 'infinity' indicates that
there is no limit. Only available starting with
API version 1.16.
rlimit_nofile=soft,hard
The maximum number of files that the process may
have open. The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_nproc=soft,hard
The maximum number of processes that the user may
run simultaneously. The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
rlimit_rss=soft,hard
The maximum size to which the process's resident
set size may grow (in bytes). The soft and hard
limits are separated by a comma. A value of
'infinity' indicates that there is no limit.
Only available starting with API version 1.16.
rlimit_stack=soft,hard
The maximum size to which the process's stack may
grow (in bytes). The soft and hard limits are
separated by a comma. A value of 'infinity'
indicates that there is no limit. Only available
starting with API version 1.16.
sid=int
The session ID of the running sudo process or 0
if sudo is not part of a POSIX job control
session. Only available starting with API
version 1.2.
tcpgid=int
The ID of the foreground process group associated
with the terminal device associated with the sudo
process or 0 if there is no terminal present.
Only available starting with API version 1.2.
tty=string
The path to the user's terminal device. If the
user has no terminal device associated with the
session, the value will be empty, as in 'tty='.
uid=uid_t
The real user-ID of the user invoking sudo.
umask=octal
The invoking user's file creation mask. Only
available starting with API version 1.10.
user=string
The name of the user invoking sudo.
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 passed as arguments to the plugin. These
arguments are split on a white space boundary and are
passed to the plugin in the form of a NULL-terminated
array of strings. If no arguments were specified,
plugin_options will be the NULL pointer.
NOTE: the plugin_options parameter is only available
starting with API version 1.2. A plugin must check the
API version specified by the sudo front end before
using plugin_options. Failure to do so may result in a
crash.
errstr
If the 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.
NOTE: 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.
close
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:
exit_status
The command's exit status, as returned by the wait(2)
system call, or zero if no command was run. 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 zero.
If no close() function is defined, no I/O logging plugins are
loaded, and neither the timeout not use_pty options are set
in the command_info list, the sudo front end may execute the
command directly instead of running it as a child process.
show_version
int (*show_version)(int verbose);
The show_version() function is called by sudo when the user
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.
check_policy
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 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 options). The files to be edited
should be copied from argv into argv_out, separated from the
editor and its arguments by a '--' element. The '--' will be
removed by sudo before the editor is executed. The plugin
should also set sudoedit=true in the command_info list.
The check_policy() function returns 1 if the command is
allowed, 0 if not allowed, -1 for a general error, or -2 for
a usage error or if sudoedit was specified but is unsupported
by the plugin. In the latter case, sudo will print a usage
message before it exits. If an error occurs, the plugin may
optionally call the conversation() or plugin_printf()
function with SUDO_CONF_ERROR_MSG to present additional error
information to the user.
The function arguments are as follows:
argc The number of elements in argv, not counting the final
NULL pointer.
argv The argument vector describing the command the user
wishes to run, in the same form as what would be passed
to the execve(2) system call. The vector is terminated
by a NULL pointer.
env_add
Additional environment variables specified by the user
on the command line in the form of a NULL-terminated
vector of 'name=value' strings. The plugin may reject
the command if one or more variables are not allowed to
be set, or it may silently ignore such variables.
When parsing env_add, the plugin should split on the
first equal sign ('=') since the name field will never
include one itself but the value might.
command_info
Information about the command being run in the form of
'name=value' strings. These values are used by sudo to
set the execution environment when running a command.
The plugin is responsible for creating and populating
the vector, which must be terminated with a NULL
pointer. The following values are recognized by sudo:
chroot=string
The root directory to use when running the
command.
closefrom=number
If specified, sudo will close all files
descriptors with a value of number or higher.
command=string
Fully qualified path to the command to be
executed.
cwd=string
The current working directory to change to when
executing the command. If sudo is unable to
change to the new working directory, the command
will not be run unless cwd_optional is also set
(see below).
cwd_optional=bool
If enabled, 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.
exec_background=bool
By default, 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.
execfd=number
If specified, 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.
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_group=string
The group that will own newly created I/O log
files and directories. This is a hint to the I/O
logging plugin which may choose to ignore it.
iolog_mode=octal
The file permission mode to use when creating I/O
log files and directories. This is a hint to the
I/O logging plugin which may choose to ignore it.
iolog_user=string
The user that will own newly created I/O log
files and directories. 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.
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.
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.
noexec=bool
If set, prevent the command from executing other
programs.
preserve_fds=list
A comma-separated list of file descriptors that
should be preserved, regardless of the value of
the closefrom setting. Only available starting
with API version 1.5.
preserve_groups=bool
If set, sudo will preserve the user's group
vector instead of initializing the group vector
based on runas_user.
runas_egid=gid
Effective group-ID to run the command as. If not
specified, the value of runas_gid is used.
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_group=string
The name of the group the command will run as, if
it is different from the runas_user's default
group. This value is provided for auditing
purposes only, the sudo front-end uses runas_egid
and runas_gid when executing the command.
runas_groups=list
The supplementary group vector to use for the
command in the form of a comma-separated list of
group-IDs. If preserve_groups is set, this
option is ignored.
runas_uid=uid
User-ID to run the command as.
runas_user=string
The name of the user the command will run as,
which should correspond to runas_euid (or
runas_uid if runas_euid is not set). This value
is provided for auditing purposes only, the sudo
front-end uses runas_euid and runas_uid 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.
set_utmp=bool
Create a utmp (or utmpx) entry when a pseudo-
terminal 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.
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.
sudoedit_checkdir=bool
Set to false to disable directory writability
checks in 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_follow option can be set to false to
disable this check. Only available starting with
API version 1.8.
sudoedit_follow=bool
Set to true to allow 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.
timeout=int
Command timeout. If non-zero then when the
timeout expires the command will be killed.
umask=octal
The file creation mask to use when executing the
command. This value may be overridden by PAM or
login.conf on some systems unless the
umask_override option is also set.
umask_override=bool
Force the value specified by the umask option to
override any umask set by PAM or login.conf.
use_pty=bool
Allocate a pseudo-terminal 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 pseudo-terminal when an I/O log plugin is
loaded.
utmp_user=string
User name to use when constructing a new utmp (or
utmpx) entry when set_utmp is enabled. This
option can be used to set the user field in the
utmp entry to the user the command runs as rather
than the invoking user. If not set, sudo will
base the new entry on the invoking user's
existing entry.
Unsupported values will be ignored.
argv_out
The NULL-terminated argument vector to pass to the
execve(2) system call when executing the command. The
plugin is responsible for allocating and populating the
vector.
user_env_out
The NULL-terminated environment vector to use when
executing the command. The plugin is responsible for
allocating and populating the vector.
errstr
If the 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.
NOTE: 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.
list
int (*list)(int argc, char * const argv[], int verbose,
const char *list_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
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.
The function arguments are as follows:
argc The number of elements in argv, not counting the final
NULL pointer.
argv If non-NULL, an argument vector describing a command
the user wishes to check against the policy in the same
form as what would be passed to the execve(2) system
call. If the command is permitted by the policy, the
fully-qualified path to the command should be displayed
along with any command line arguments.
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.
errstr
If the 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.
NOTE: 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.
validate
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
plugin_printf() function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
The function arguments are as follows:
errstr
If the 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.
NOTE: 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.
invalidate
void (*invalidate)(int remove);
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 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_env_out[]);
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_out 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_out. The expected use case is to merge the contents
of the PAM environment (if any) with the contents of
user_env_out. NOTE: 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.
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.
event_alloc
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.
NOTE: 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.
errstr
If the 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.
NOTE: 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.
Policy Plugin Version Macros
/* 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)
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[], 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 (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-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.
The audit_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[], 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 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 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.
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.
command_info
A vector of information describing the command being
run in the form of 'name=value' strings. The vector is
terminated by a 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.
argc The number of elements in argv, not counting the final
NULL pointer. It can be zero, when sudo is called with
-V.
argv If non-NULL, an argument vector describing a command
the user wishes to run in the same form as what would
be passed to the execve(2) system call.
user_env
The user's environment in the form of a NULL-terminated
vector of 'name=value' strings.
When parsing user_env, the plugin should split on the
first equal sign ('=') since the name field will never
include one itself but the value might.
plugin_options
Any (non-comment) strings immediately after the plugin
path are treated as arguments to the plugin. These
arguments are split on a white space boundary and are
passed to the plugin in the form of a NULL-terminated
array of strings. If no arguments were specified,
plugin_options will be the NULL pointer.
NOTE: the plugin_options parameter is only available
starting with API version 1.2. A plugin must check the
API version specified by the sudo front end before
using plugin_options. Failure to do so may result in a
crash.
errstr
If the 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.
NOTE: 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.
close
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:
exit_status
The command's exit status, as returned by the wait(2)
system call, or zero if no command was run. 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 zero.
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.
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.
log_ttyin
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:
buf The buffer containing user input.
len The length of buf in bytes.
errstr
If the 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.
NOTE: 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.
log_ttyout
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:
buf The buffer containing command output.
len The length of buf in bytes.
errstr
If the 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.
NOTE: 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.
log_stdin
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:
buf The buffer containing user input.
len The length of buf in bytes.
errstr
If the 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.
NOTE: 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.
log_stdout
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:
buf The buffer containing command output.
len The length of buf in bytes.
errstr
If the 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.
NOTE: 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.
log_stderr
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:
buf The buffer containing command output.
len The length of buf in bytes.
errstr
If the 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.
NOTE: 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
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.
change_winsize
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:
lines
The number of lines (rows) in the re-sized terminal.
cols The number of columns in the re-sized terminal.
errstr
If the 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.
NOTE: 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.
log_suspend
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:
signo
The signal that caused the command to be suspended, or
SIGCONT if the command was resumed.
errstr
If the 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.
NOTE: 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.
event_alloc
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.
NOTE: 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.
I/O Plugin Version Macros
Same as for the Policy plugin API.
Audit 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_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).
The audit_plugin struct has the following fields:
type The type field should always be set to SUDO_AUDIT_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 sudo_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:
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 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.
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.
submit_optind
The index into submit_argv that corresponds to the
first entry that is not a command line option. If
submit_argv only consists of options, which may be the
case with the -l or -v options,
submit_argv[submit_optind] will evaluate to the NULL
pointer.
submit_argv
The argument vector 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.
submit_envp
The invoking user's environment in the form of a
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.
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.
errstr
If the 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.
close
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:
status_type
The type of status being passed. One of
SUDO_PLUGIN_NO_STATUS, SUDO_PLUGIN_WAIT_STATUS,
SUDO_PLUGIN_EXEC_ERROR or SUDO_PLUGIN_SUDO_ERROR.
status
Depending on the value of status_type, this value is
either ignored, the command's exit status as returned
by the wait(2) system call, the value of errno set by
the execve(2) system call, or the value of errno
resulting from an error in the sudo front end.
accept
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:
plugin_name
The name of the plugin that accepted the command or
'sudo' for the sudo front-end.
plugin_type
The type of plugin that accepted the command, currently
either 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.
command_info
An optional vector of information describing the
command being run in the form of 'name=value' strings.
The vector is terminated by a 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.
run_argv
A 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.
run_envp
The environment the command will be run with in the
form of a 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.
errstr
If the 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.
reject
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:
plugin_name
The name of the plugin that rejected the command.
plugin_type
The type of plugin that rejected the command, currently
either 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.
audit_msg
An optional string describing the reason the command
was rejected by the plugin. If the plugin did not
provide a reason, audit_msg will be the NULL pointer.
command_info
An optional vector of information describing the
command being run in the form of 'name=value' strings.
The vector is terminated by a 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.
errstr
If the 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.
error
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:
plugin_name
The name of the plugin that generated the error or
'sudo' for the sudo front-end.
plugin_type
The type of plugin that generated the error, or
SUDO_FRONT_END for the sudo front-end.
audit_msg
An optional string describing the plugin error. If the
plugin did not provide a description, audit_msg will be
the NULL pointer.
command_info
An optional vector of information describing the
command being run in the form of 'name=value' strings.
The vector is terminated by a 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.
errstr
If the 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.
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.
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
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.
event_alloc
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.
NOTE: 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.
Approval plugin API
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_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).
The approval_plugin struct has the following fields:
type The type field should always be set to SUDO_APPROVAL_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 sudo_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:
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
Conversation API for details). 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
Conversation API for details). 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 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.
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.
submit_optind
The index into submit_argv that corresponds to the
first entry that is not a command line option. If
submit_argv only consists of options, which may be the
case with the -l or -v options,
submit_argv[submit_optind] will evaluate to the NULL
pointer.
submit_argv
The argument vector 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.
submit_envp
The invoking user's environment in the form of a
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.
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.
errstr
If the 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.
close
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.
check
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:
command_info
A vector of information describing the command being
run in the form of 'name=value' strings. The vector is
terminated by a 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.
run_argv
A 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.
run_envp
The environment the command will be run with in the
form of a 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.
errstr
If the 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.
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.
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.
Signal handlers
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:
• SIGALRM
• SIGHUP
• SIGINT
• SIGPIPE
• SIGQUIT
• SIGTERM
• SIGTSTP
• SIGUSR1
• SIGUSR2
If a fatal signal is received before the command is executed, sudo
will call the plugin's close() function with an exit status of 128
plus the value of the signal that was received. This allows for
consistent 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.
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 {
unsigned int hook_version;
unsigned int hook_type;
sudo_hook_fn_t hook_fn;
void *closure;
};
The sudo_hook structure has the following fields:
hook_version
The hook_version field should be set to SUDO_HOOK_VERSION.
hook_type
The hook_type field may be one of the following supported
hook types:
SUDO_HOOK_SETENV
The C library setenv(3) function. Any registered hooks
will run before the C library implementation. The
hook_fn field should be a function that matches the
following typedef:
typedef int (*sudo_hook_fn_setenv_t)(const char *name,
const char *value, int overwrite, void *closure);
If the registered hook does not match the typedef the
results are unspecified.
SUDO_HOOK_UNSETENV
The C library unsetenv(3) function. Any registered
hooks will run before the C library implementation.
The hook_fn field should be a function that matches the
following typedef:
typedef int (*sudo_hook_fn_unsetenv_t)(const char *name,
void *closure);
SUDO_HOOK_GETENV
The C library getenv(3) function. Any registered hooks
will run before the C library implementation. The
hook_fn field should be a function that matches the
following typedef:
typedef int (*sudo_hook_fn_getenv_t)(const char *name,
char **value, void *closure);
If the registered hook does not match the typedef the
results are unspecified.
SUDO_HOOK_PUTENV
The C library putenv(3) function. Any registered hooks
will run before the C library implementation. The
hook_fn field should be a function that matches the
following typedef:
typedef int (*sudo_hook_fn_putenv_t)(char *string,
void *closure);
If the registered hook does not match the typedef the
results are unspecified.
hook_fn
sudo_hook_fn_t hook_fn;
The hook_fn field should be set to the plugin's hook
implementation. The actual function arguments will vary
depending on the hook_type (see hook_type above). In all
cases, the closure field of struct sudo_hook is passed as the
last function parameter. This can be used to pass arbitrary
data to the plugin's hook implementation.
The function return value may be one of the following:
SUDO_HOOK_RET_ERROR
The hook function encountered an error.
SUDO_HOOK_RET_NEXT
The hook completed without error, go on to the next
hook (including the system implementation if
applicable). For example, a getenv(3) hook might
return SUDO_HOOK_RET_NEXT if the specified variable was
not found in the private copy of the environment.
SUDO_HOOK_RET_STOP
The hook completed without error, stop processing hooks
for this invocation. This can be used to replace the
system implementation. For example, a setenv hook that
operates on a private copy of the environment but
leaves environ unchanged.
Note that it is very easy to create an infinite loop when hooking C
library functions. For example, a getenv(3) hook that calls the
snprintf(3) function may create a loop if the snprintf(3)
implementation calls getenv(3) to check the locale. To prevent
this, you may wish to use a static variable in the hook function to
guard against nested calls. For example:
static int in_progress = 0; /* avoid recursion */
if (in_progress)
return SUDO_HOOK_RET_NEXT;
in_progress = 1;
...
in_progress = 0;
return SUDO_HOOK_RET_STOP;
Hook API Version Macros
/* Hook API version major/minor */
#define SUDO_HOOK_VERSION_MAJOR 1
#define SUDO_HOOK_VERSION_MINOR 0
#define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
SUDO_HOOK_VERSION_MINOR)
For getters and setters see the Policy plugin API.
Event 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.
Event structure
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);
};
The sudo_plugin_event struct contains the following function
pointers:
set()
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:
struct sudo_plugin_event *pev
A pointer to the struct sudo_plugin_event itself.
fd The file or socket descriptor for I/O-based events or
the signal number for signal events. For time-based
events, fd must be -1.
events
The following values determine what will trigger the
event callback:
SUDO_PLUGIN_EV_TIMEOUT
callback is run after the specified timeout
expires
SUDO_PLUGIN_EV_READ
callback is run when the file descriptor is
readable
SUDO_PLUGIN_EV_WRITE
callback is run when the file descriptor is
writable
SUDO_PLUGIN_EV_PERSIST
event is persistent and remains enabled until
explicitly deleted
SUDO_PLUGIN_EV_SIGNAL
callback is run when the specified signal is
received
The 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.
sudo_plugin_ev_callback_t callback
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:
fd The file or socket descriptor for I/O-based
events or the signal number for signal events.
what The event type that triggered that callback. For
events that have multiple event types (for
example 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.
closure
The generic pointer that was specified in the
set() function.
closure
A generic pointer that will be passed to the callback
function.
The set() function returns 1 on success, and -1 if a error
occurred.
add()
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.
del()
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.
pending()
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.
fd()
int (*fd)(struct sudo_plugin_event *pev);
The fd() function returns the descriptor or signal number
associated with the event pev.
setbase()
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.
loopbreak()
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.
free()
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.
Remote command execution
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.
Note that remote sudoedit functionality must be handled by the
policy plugin, not sudo itself as the front end has no knowledge
that a remote command is being executed. This may be addressed in
a future revision of the plugin API.
Conversation API
If the plugin needs to interact with the user, it may do so via the
conversation() function. A plugin should not attempt to read
directly from the standard input or the user's tty (neither of
which are 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 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, 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. Note that 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_OFF
Prompt the user for input with echo disabled; this is
generally used for passwords. The reply will be stored in
the replies array, and it will never be NULL.
SUDO_CONV_PROMPT_ECHO_ON
Prompt the user for input with echo enabled. The reply will
be stored in the replies array, and it will never be NULL.
SUDO_CONV_ERROR_MSG
Display an error message. The message is written to the
standard error unless the SUDO_CONV_PREFER_TTY flag is set,
in which case it is written to the user's terminal if
possible.
SUDO_CONV_INFO_MSG
Display a message. The message is written to the standard
output unless the SUDO_CONV_PREFER_TTY flag is set, in which
case it is written to the user's terminal if possible.
SUDO_CONV_PROMPT_MASK
Prompt the user for input but echo an asterisk character for
each character read. The reply will be stored in the replies
array, and it will never be NULL. 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_OK
Allow input to be read when echo cannot be disabled when the
message type is SUDO_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_TTY
When displaying a message via SUDO_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 The
user's terminal is always used when possible for input, this
flag is only used for output. SUDO_CONV_ERROR_MSG or
SUDO_CONV_INFO_MSG was used.
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.
Plugin invocation order
As of sudo 1.9.0, the plugin open() and close() functions are
called in the following order:
1. audit open
2. policy open
3. approval open
4. approval close
5. I/O log open
6. command runs
7. command exits
8. I/O log close
9. policy close
10. audit close
11. sudo exits
Prior to sudo 1.9.0, the I/O log close() function was called after
the policy close() function.
Sudoers group plugin API
The sudoers plugin supports its own plugin interface to allow non-
Unix group lookups. This can be used to query a group source other
than the standard Unix group database. Two sample group plugins
are bundled with sudo, group_file and system_group, are detailed in
sudoers(5). Third party group plugins include a QAS AD plugin
available from Quest 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)
For getters and setters see the Policy plugin API.
