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NAME | DESCRIPTION | PLUGIN API CHANGELOG | SEE ALSO | AUTHORS | BUGS | SUPPORT | DISCLAIMER | COLOPHON |
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SUDO_PLUGIN(5) File Formats Manual SUDO_PLUGIN(5)
sudo_plugin — Sudo Plugin API
Starting with version 1.8, sudo supports a plugin API for policy
and session logging. Plugins may be compiled as dynamic shared
objects (the default on systems that support them) or compiled
statically into the sudo binary itself. By default, the sudoers
plugin provides audit, security policy and I/O logging
capabilities. Via the plugin API, sudo can be configured to use
alternate plugins provided by third parties. The plugins to be
used are specified in the sudo.conf(5) file.
The API is versioned with a major and minor number. The minor
version number is incremented when additions are made. The major
number is incremented when incompatible changes are made. A
plugin should be check the version passed to it and make sure
that the major version matches.
The plugin API is defined by the <sudo_plugin.h> header file.
Policy plugin API
A policy plugin must declare and populate a struct policy_plugin
in the global scope. This structure contains pointers to the
functions that implement the sudo policy checks. The name of the
symbol should be specified in sudo.conf(5) along with a path to
the plugin so that sudo can load it.
struct policy_plugin {
#define SUDO_POLICY_PLUGIN 1
unsigned int type; /* always SUDO_POLICY_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation,
sudo_printf_t sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[], const char **errstr);
void (*close)(int exit_status, int error);
int (*show_version)(int verbose);
int (*check_policy)(int argc, char * const argv[],
char *env_add[], char **command_info[],
char **argv_out[], char **user_env_out[], const char **errstr);
int (*list)(int argc, char * const argv[], int verbose,
const char *user, const char **errstr);
int (*validate)(const char **errstr);
void (*invalidate)(int rmcred);
int (*init_session)(struct passwd *pwd, char **user_env[],
const char **errstr);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
struct sudo_plugin_event * (*event_alloc)(void);
};
A struct policy_plugin has the following fields:
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 sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const user_env[],
char * const plugin_options[], const char **errstr);
Returns 1 on success, 0 on failure, -1 if a general error
occurred, or -2 if there was a usage error. In the latter
case, sudo will print a usage message before it exits. If
an error occurs, the plugin may optionally call the
conversation() or sudo_plugin_printf() function with
SUDO_CONF_ERROR_MSG to present additional error information
to the user.
The function arguments are as follows:
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.
sudo_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 implied_shell.
intercept_ptrace=bool
Indicates whether or not the system supports
intercept mode using ptrace(2). This is
currently only true for Linux systems that
support seccomp(2) filtering and the “trap”
action. Other systems will use a dynamic
shared object to implement intercept. Only
available starting with API version 1.19.
intercept_setid=bool
Indicates whether or not the system supports
running set-user-ID and set-group-ID binaries
in intercept mode. This is currently only true
for Linux systems that support seccomp(2)
filtering and the “trap” action. On systems
that use a dynamic shared object to implement
intercept, the dynamic linker (ld.so or the
equivalent) will disable preloading of shared
objects when executing a set-user-ID or set-
group-ID binary. This will disable intercept
mode for that program and any other programs
that it executes. The policy plugin may refuse
to execute a set-user-ID or set-group-ID binary
in intercept mode to avoid this. Only
available starting with API version 1.19.
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 group-ID to run the command
as, if specified via the -g option.
runas_user=string
The user name or user-ID 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.
update_ticket=bool
Set to false if the user specified the -N
option, indicating that the user wishes to
avoid updating any cached authentication
credentials. Only available starting with API
version 1.20.
Additional settings may be added in the future so the
plugin should silently ignore settings that it does
not recognize.
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 one
exists. This entry is only present if the user
has a terminal device associated with the
session.
ttydev=dev_t
The number of the user's terminal device, if
one exists, in the form of a dev_t. This entry
is only present if the user has a terminal
device associated with the session. Only
available starting with API version 1.22.
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.
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.
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
sudo_plugin_printf() function. If the command was
successfully executed, the value of error is zero.
If no close() function is defined, no I/O logging plugins
are loaded, and neither the timeout nor use_pty options are
set in the command_info list, the sudo front-end may
execute the command directly instead of running it as a
child process.
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
sudo_plugin_printf() function using SUDO_CONV_INFO_MSG. If
the user requests detailed version information, the verbose
flag will be non-zero.
Returns 1 on success, 0 on failure, -1 if a general error
occurred, or -2 if there was a usage error, although the
return value is currently ignored.
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 must set sudoedit=true in
the command_info list. The plugin is responsible for
choosing the editor to be used, potentially from a variable
in the user's environment, such as EDITOR, and should be
stored in argv_out (environment variables may include
command line options). The files to be edited should be
copied from argv to argv_out, separated from the editor and
its arguments by a ‘--’ element. The ‘--’ will be removed
by sudo before the editor is executed. The plugin may also
set sudoedit_nfiles to the number of files to be edited in
the command_info list; this will only be used by the sudo
front-end starting with API version 1.21.
The check_policy() function returns 1 if the command is
allowed, 0 if not allowed, -1 for a general error, or -2
for a usage error or if sudoedit was specified but is
unsupported by the plugin. In the latter case, sudo will
print a usage message before it exits. If an error occurs,
the plugin may optionally call the conversation() or
sudo_plugin_printf() function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
The function arguments are as follows:
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:
apparmor_profile=string
AppArmor profile to transition to when
executing the command. Only available starting
with API version 1.19.
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 set, 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.
intercept=bool
If set, sudo will intercept attempts to execute
a subsequent command and perform a policy check
via the policy plugin's check_policy() function
to determine whether or not the command is
permitted. This can be used to prevent shell
escapes on supported platforms but it has a
number of limitations. See Preventing shell
escapes in sudoers(5) for details. Only
available starting with API version 1.18.
intercept_verify=bool
If set, sudo will attempt to verify that a
command run in intercept mode has the expected
path name, command line arguments and
environment. This setting has no effect unless
use_ptrace is also enabled. Only available
starting with API version 1.20.
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.
log_subcmds=bool
If set, sudo will call the audit plugin's
accept() function to log when the command runs
a subsequent command, if supported by the
system. If intercept is also specified,
log_subcmds will be ignored. See Preventing
shell escapes in sudoers(5) for more
information. Only available starting with API
version 1.18.
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.
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. If only a single value
is specified, both the hard and soft limits are
set. A value of “infinity” indicates that
there is no limit. A value of “user” will
cause the invoking user's resource limit to be
preserved. A value of “default” will cause the
target user's default resource limit to be used
on systems that allow per-user resource limits
to be configured. Only available starting with
API version 1.18.
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. If only a single
value is specified, both the hard and soft
limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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. If only a single
value is specified, both the hard and soft
limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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. If only a single
value is specified, both the hard and soft
limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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. If only a single
value is specified, both the hard and soft
limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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. If only a single value is
specified, both the hard and soft limits are
set. A value of “infinity” indicates that
there is no limit. A value of “user” will
cause the invoking user's resource limit to be
preserved. A value of “default” will cause the
target user's default resource limit to be used
on systems that allow per-user resource limits
to be configured. Only available starting with
API version 1.18.
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. If only a single value
is specified, both the hard and soft limits are
set. A value of “infinity” indicates that
there is no limit. A value of “user” will
cause the invoking user's resource limit to be
preserved. A value of “default” will cause the
target user's default resource limit to be used
on systems that allow per-user resource limits
to be configured. Only available starting with
API version 1.18.
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. If only a single value
is specified, both the hard and soft limits are
set. A value of “infinity” indicates that
there is no limit. A value of “user” will
cause the invoking user's resource limit to be
preserved. A value of “default” will cause the
target user's default resource limit to be used
on systems that allow per-user resource limits
to be configured. Only available starting with
API version 1.18.
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. If only a
single value is specified, both the hard and
soft limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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.
If only a single value is specified, both the
hard and soft limits are set. A value of
“infinity” indicates that there is no limit. A
value of “user” will cause the invoking user's
resource limit to be preserved. A value of
“default” will cause the target user's default
resource limit to be used on systems that allow
per-user resource limits to be configured.
Only available starting with API version 1.18.
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. If only a single
value is specified, both the hard and soft
limits are set. A value of “infinity”
indicates that there is no limit. A value of
“user” will cause the invoking user's resource
limit to be preserved. A value of “default”
will cause the target user's default resource
limit to be used on systems that allow per-user
resource limits to be configured. Only
available starting with API version 1.18.
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_checkdir 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.
sudoedit_nfiles=number
The number of files to be edited by the user.
If present, this is will be used by the sudo
front-end to determine which elements of the
argv_out vector are files to be edited. The
‘--’ element must immediately precede the first
file to be edited. If sudoedit_nfiles is not
specified, the sudo front-end will use the
position of the ‘--’ element to determine where
the file list begins. Only available starting
with API version 1.21.
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_ptrace=bool
If set, sudo will use ptrace(2) to implement
intercept mode if supported by the system.
This setting has no effect unless intercept is
also set. Only available starting with API
version 1.19.
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.
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 *user, const char **errstr);
List available privileges for the invoking user. Returns 1
on success, 0 on failure, and -1 on error. On error, the
plugin may optionally call the conversation() or
sudo_plugin_printf() function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
Privileges should be output via the conversation() or
sudo_plugin_printf() function using SUDO_CONV_INFO_MSG.
The function arguments are as follows:
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.
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.
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
sudo_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.
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 rmcred);
The invalidate() function is called when sudo is run with
the -k or -K option. For policy plugins such as sudoers
that cache authentication credentials, this function will
invalidate the credentials. If the rmcred flag is non-
zero, the plugin may remove the credentials instead of
simply invalidating them.
The invalidate() function should be NULL if the plugin does
not support credential caching.
init_session
int (*init_session)(struct passwd *pwd, char **user_env[],
const char **errstr);
The init_session() function is called before sudo sets up
the execution environment for the command. It is run in
the parent sudo process before any user-ID or group-ID
changes. This can be used to perform session setup that is
not supported by command_info, such as opening the PAM
session. The close() function can be used to tear down the
session that was opened by init_session().
Returns 1 on success, 0 on failure, and -1 on error. On
error, the plugin may optionally call the conversation() or
sudo_plugin_printf() function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
The function arguments are as follows:
pwd If the user-ID the command will run as was found in
the password database, pwd will describe that user,
otherwise it will be NULL.
user_env_out
The NULL-terminated environment vector to use when
executing the command. This is the same string
passed back to the front-end via the Policy Plugin's
user_env_out parameter. If the init_session()
function needs to modify the user environment, it
should update the pointer stored in user_env_out.
The expected use case is to merge the contents of the
PAM environment (if any) with the contents of
user_env_out. The user_env_out parameter is only
available starting with API version 1.2. A plugin
must check the API version specified by the sudo
front-end before using user_env_out. Failure to do
so may result in a crash.
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.
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
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
The register_hooks() function is called by the sudo front-
end to register any hooks the plugin needs. If the plugin
does not support hooks, register_hooks should be set to the
NULL pointer.
The version argument describes the version of the hooks API
supported by the sudo front-end.
The register_hook() function should be used to register any
supported hooks the plugin needs. It returns 0 on success,
1 if the hook type is not supported, and -1 if the major
version in struct sudo_hook does not match the front-end's
major hook API version.
See the “Hook function API” section below for more
information about hooks.
The register_hooks() function is only available starting
with API version 1.2. If the sudo front-end doesn't
support API version 1.2 or higher, register_hooks() will
not be called.
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.
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.
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.
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 sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const command_info[],
int argc, char * const argv[], char * const user_env[],
char * const plugin_options[], const char **errstr);
void (*close)(int exit_status, int error); /* wait status or error */
int (*show_version)(int verbose);
int (*log_ttyin)(const char *buf, unsigned int len,
const char **errstr);
int (*log_ttyout)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stdin)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stdout)(const char *buf, unsigned int len,
const char **errstr);
int (*log_stderr)(const char *buf, unsigned int len,
const char **errstr);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
int (*change_winsize)(unsigned int lines, unsigned int cols,
const char **errstr);
int (*log_suspend)(int signo, const char **errstr);
struct sudo_plugin_event * (*event_alloc)(void);
};
When an I/O plugin is loaded, sudo runs the command in a pseudo-
terminal. This makes it possible to log the input and output
from the user's session. If any of the standard input, standard
output, or standard error do not correspond to a tty, sudo will
open a pipe to capture the I/O for logging before passing it on.
The log_ttyin() function receives the raw user input from the
terminal device (this will include input even when echo is
disabled, such as when a password is read). The log_ttyout()
function receives output from the pseudo-terminal that is
suitable for replaying the user's session at a later time. The
log_stdin(), log_stdout(), and log_stderr() functions are only
called if the standard input, standard output, or standard error
respectively correspond to something other than a tty.
Any of the logging functions may be set to the NULL pointer if no
logging is to be performed. If the open function returns 0, no
I/O will be sent to the plugin.
If a logging function returns an error (-1), the running command
will be terminated and all of the plugin's logging functions will
be disabled. Other I/O logging plugins will still receive any
remaining input or output that has not yet been processed.
If an input logging function rejects the data by returning 0, the
command will be terminated and the data will not be passed to the
command, though it will still be sent to any other I/O logging
plugins. If an output logging function rejects the data by
returning 0, the command will be terminated and the data will not
be written to the terminal, though it will still be sent to any
other I/O logging plugins.
A struct audit_plugin has the following fields:
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 sudo_plugin_printf, char * const settings[],
char * const user_info[], char * const command_info[],
int argc, char * const argv[], char * const user_env[],
char * const plugin_options[]);
The open() function is run before the log_ttyin(),
log_ttyout(), log_stdin(), log_stdout(), log_stderr(),
log_suspend(), change_winsize(), or show_version()
functions are called. It is only called if the version is
being requested or if the policy plugin's check_policy()
function has returned successfully. It returns 1 on
success, 0 on failure, -1 if a general error occurred, or
-2 if there was a usage error. In the latter case, sudo
will print a usage message before it exits. If an error
occurs, the plugin may optionally call the conversation()
or sudo_plugin_printf() function with SUDO_CONF_ERROR_MSG
to present additional error information to the user.
The function arguments are as follows:
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 Fa(show_version) function to display
version information (see show_version() below). The
conversation() function may also be used to display
additional error message to the user. The
conversation() function returns 0 on success and -1
on failure.
sudo_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
sudo_plugin_printf() function may also be used to
display additional error message to the user. The
sudo_plugin_printf() function returns number of
characters printed on success and -1 on failure.
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, such as when
sudo is called with the -V option.
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.
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.
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
sudo_plugin_printf() function using SUDO_CONV_INFO_MSG. If
the user requests detailed version information, the verbose
flag will be non-zero.
Returns 1 on success, 0 on failure, -1 if a general error
occurred, or -2 if there was a usage error, although the
return value is currently ignored.
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.
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.
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.
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.
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.
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.
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.
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.
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_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
void (*close)(int status_type, int status);
int (*accept)(const char *plugin_name,
unsigned int plugin_type, char * const command_info[],
char * const run_argv[], char * const run_envp[],
const char **errstr);
int (*reject)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
int (*error)(const char *plugin_name, unsigned int plugin_type,
const char *audit_msg, char * const command_info[],
const char **errstr);
int (*show_version)(int verbose);
void (*register_hooks)(int version,
int (*register_hook)(struct sudo_hook *hook));
void (*deregister_hooks)(int version,
int (*deregister_hook)(struct sudo_hook *hook));
struct sudo_plugin_event * (*event_alloc)(void);
}
An audit plugin can be used to log successful and unsuccessful
attempts to run sudo independent of the policy or any I/O
plugins. Multiple audit plugins may be specified in
sudo.conf(5).
A struct audit_plugin has the following fields:
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_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
The audit open() function is run before any other sudo
plugin API functions. This makes it possible to audit
failures in the other plugins. It returns 1 on success, 0
on failure, -1 if a general error occurred, or -2 if there
was a usage error. In the latter case, sudo will print a
usage message before it exits. If an error occurs, the
plugin may optionally call the conversation() or
plugin_printf() function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
The function arguments are as follows:
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.
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_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
void (*close)(void);
int (*check)(char * const command_info[], char * const run_argv[],
char * const run_envp[], const char **errstr);
int (*show_version)(int verbose);
};
An approval plugin can be used to apply extra constraints after a
command has been accepted by the policy plugin. Unlike the other
plugin types, it does not remain open until the command
completes. The plugin is opened before a call to check() or
show_version() and closed shortly thereafter (audit plugin
functions must be called before the plugin is closed). Multiple
approval plugins may be specified in sudo.conf(5).
A struct approval_plugin has the following fields:
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_plugin_printf, char * const settings[],
char * const user_info[], int submit_optind,
char * const submit_argv[], char * const submit_envp[],
char * const plugin_options[], const char **errstr);
The approval open() function is run immediately before a
call to the plugin's check() or show_version() functions.
It is only called if the version is being requested or if
the policy plugin's check_policy() function has returned
successfully. It returns 1 on success, 0 on failure, -1 if
a general error occurred, or -2 if there was a usage error.
In the latter case, sudo will print a usage message before
it exits. If an error occurs, the plugin may optionally
call the conversation() or plugin_printf() function with
SUDO_CONF_ERROR_MSG to present additional error information
to the user.
The function arguments are as follows:
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;
};
A struct sudo_hook 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.
Care must be taken when hooking C library functions, it is very
easy to create an infinite loop. For example, a getenv(3) hook
that calls the snprintf(3) function may create a loop if the
snprintf(3) implementation calls getenv(3) to check the locale.
To prevent this, you may wish to use a static variable in the
hook function to guard against nested calls. For example:
static int in_progress = 0; /* avoid recursion */
if (in_progress)
return SUDO_HOOK_RET_NEXT;
in_progress = 1;
...
in_progress = 0;
return SUDO_HOOK_RET_STOP;
Hook API Version Macros
/* Hook API version major/minor */
#define SUDO_HOOK_VERSION_MAJOR 1
#define SUDO_HOOK_VERSION_MINOR 0
#define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
SUDO_HOOK_VERSION_MINOR)
For getters and setters see the “Policy plugin API”.
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);
};
A struct sudo_plugin_event 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.
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 terminal (neither
of which are guaranteed to exist). The caller must include a
trailing newline in msg if one is to be printed.
A printf()-style function is also available that can be used to
display informational or error messages to the user, which is
usually more convenient for simple messages where no use input is
required.
Conversation function structures
The conversation function takes as arguments pointers to the
following structures:
struct sudo_conv_message {
#define SUDO_CONV_PROMPT_ECHO_OFF 0x0001 /* do not echo user input */
#define SUDO_CONV_PROMPT_ECHO_ON 0x0002 /* echo user input */
#define SUDO_CONV_ERROR_MSG 0x0003 /* error message */
#define SUDO_CONV_INFO_MSG 0x0004 /* informational message */
#define SUDO_CONV_PROMPT_MASK 0x0005 /* mask user input */
#define SUDO_CONV_PROMPT_ECHO_OK 0x1000 /* flag: allow echo if no tty */
#define SUDO_CONV_PREFER_TTY 0x2000 /* flag: use tty if possible */
int msg_type;
int timeout;
const char *msg;
};
#define SUDO_CONV_REPL_MAX 1023
struct sudo_conv_reply {
char *reply;
};
typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure);
struct sudo_conv_callback {
unsigned int version;
void *closure;
sudo_conv_callback_fn_t on_suspend;
sudo_conv_callback_fn_t on_resume;
};
Pointers to the conversation() and printf()-style functions are
passed in to the plugin's open() function when the plugin is
initialized. The following type definitions can be used in the
declaration of the open() function:
typedef int (*sudo_conv_t)(int num_msgs,
const struct sudo_conv_message msgs[],
struct sudo_conv_reply replies[], struct sudo_conv_callback *callback);
typedef int (*sudo_printf_t)(int msg_type, const char * restrict fmt, ...);
To use the conversation() function, the plugin must pass an array
of struct sudo_conv_message and struct sudo_conv_reply. There
must be a struct sudo_conv_message and struct sudo_conv_reply for
each message in the conversation, that is, both arrays must have
the same number of elements. Each struct sudo_conv_reply must
have its reply member initialized to NULL. The struct
sudo_conv_callback pointer, if not NULL, should contain function
pointers to be called when the sudo process is suspended and/or
resumed during conversation input. The on_suspend and on_resume
functions are called with the signal that caused sudo to be
suspended and the closure pointer from the struct
sudo_conv_callback. These functions should return 0 on success
and -1 on error. On error, the conversation will end and the
conversation function will return a value of -1. The intended
use is to allow the plugin to release resources, such as locks,
that should not be held indefinitely while suspended and then
reacquire them when the process is resumed. The functions are
not actually invoked from within a signal handler.
The msg_type must be set to one of the following values:
SUDO_CONV_PROMPT_ECHO_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 SUDO_CONV_ERROR_MSG or SUDO_CONV_INFO_MSG was used.
The user's terminal is always used when possible for input,
this flag is only used for output.
The timeout in seconds until the prompt will wait for no more
input. A zero value implies an infinite timeout.
The plugin is responsible for freeing the reply buffer located in
each struct sudo_conv_reply, if it is not NULL.
SUDO_CONV_REPL_MAX represents the maximum length of the reply
buffer (not including the trailing NUL character). In practical
terms, this is the longest password sudo will support.
The printf()-style function uses the same underlying mechanism as
the conversation() function but only supports SUDO_CONV_INFO_MSG
and SUDO_CONV_ERROR_MSG for the msg_type parameter. It can be
more convenient than using the conversation() function if no user
reply is needed and supports standard printf() escape sequences.
See the sample plugin for an example of the conversation()
function usage.
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 struct
sudoers_group_plugin in the global scope. This structure
contains pointers to the functions that implement plugin
initialization, cleanup, and group lookup.
struct sudoers_group_plugin {
unsigned int version;
int (*init)(int version, sudo_printf_t sudo_plugin_printf,
char *const argv[]);
void (*cleanup)(void);
int (*query)(const char *user, const char *group,
const struct passwd *pwd);
};
A struct sudoers_group_plugin has the following fields:
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 sudo_plugin_printf,
char *const argv[]);
The init() function is called after sudoers has been parsed
but before any policy checks. It returns 1 on success, 0
on failure (or if the plugin is not configured), and -1 if
a error occurred. If an error occurs, the plugin may call
the plugin_printf() function with SUDO_CONF_ERROR_MSG to
present additional error information to the user.
The function arguments are as follows:
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”.
The following revisions have been made to the Sudo Plugin API.
Version 1.0
Initial API version.
Version 1.1 (sudo 1.8.0)
The I/O logging plugin's open() function was modified to
take the command_info list as an argument.
Version 1.2 (sudo 1.8.5)
The Policy and I/O logging plugins' open() functions are
now passed a list of plugin parameters if any are specified
in sudo.conf(5).
A simple hooks API has been introduced to allow plugins to
hook in to the system's environment handling functions.
The init_session() Policy plugin function is now passed a
pointer to the user environment which can be updated as
needed. This can be used to merge in environment variables
stored in the PAM handle before a command is run.
Version 1.3 (sudo 1.8.7)
Support for the exec_background entry has been added to the
command_info list.
The max_groups and plugin_dir entries were added to the
settings list.
The version() and close() functions are now optional.
Previously, a missing version() or close() function would
result in a crash. If no policy plugin close() function is
defined, a default close() function will be provided by the
sudo front-end that displays a warning if the command could
not be executed.
The sudo front-end now installs default signal handlers to
trap common signals while the plugin functions are run.
Version 1.4 (sudo 1.8.8)
The remote_host entry was added to the settings list.
Version 1.5 (sudo 1.8.9)
The preserve_fds entry was added to the command_info list.
Version 1.6 (sudo 1.8.11)
The behavior when an I/O logging plugin returns an error
(-1) has changed. Previously, the sudo front-end took no
action when the log_ttyin(), log_ttyout(), log_stdin(),
log_stdout(), or log_stderr() function returned an error.
The behavior when an I/O logging plugin returns 0 has
changed. Previously, output from the command would be
displayed to the terminal even if an output logging
function returned 0.
Version 1.7 (sudo 1.8.12)
The plugin_path entry was added to the settings list.
The debug_flags entry now starts with a debug file path
name and may occur multiple times if there are multiple
plugin-specific Debug lines in the sudo.conf(5) file.
Version 1.8 (sudo 1.8.15)
The sudoedit_checkdir and sudoedit_follow entries were
added to the command_info list. The default value of
sudoedit_checkdir was changed to true in sudo 1.8.16.
The sudo conversation() function now takes a pointer to a
struct sudo_conv_callback as its fourth argument. The
sudo_conv_t definition has been updated to match. The
plugin must specify that it supports plugin API version 1.8
or higher to receive a conversation function pointer that
supports this argument.
Version 1.9 (sudo 1.8.16)
The execfd entry was added to the command_info list.
Version 1.10 (sudo 1.8.19)
The umask entry was added to the user_info list. The
iolog_group, iolog_mode, and iolog_user entries were added
to the command_info list.
Version 1.11 (sudo 1.8.20)
The timeout entry was added to the settings list.
Version 1.12 (sudo 1.8.21)
The change_winsize() function was added to struct
io_plugin.
Version 1.13 (sudo 1.8.26)
The log_suspend() function was added to struct io_plugin.
Version 1.14 (sudo 1.8.29)
The umask_override entry was added to the command_info
list.
Version 1.15 (sudo 1.9.0)
The cwd_optional entry was added to the command_info list.
The event_alloc() function was added to struct
policy_plugin and struct io_plugin.
The errstr argument was added to the policy and I/O plugin
functions which the plugin function can use to return an
error string. This string may be used by the audit plugin
to report failure or error conditions set by the other
plugins.
The close() function is now is called regardless of whether
or not a command was actually executed. This makes it
possible for plugins to perform cleanup even when a command
was not run.
SUDO_CONV_REPL_MAX has increased from 255 to 1023 bytes.
Support for audit and approval plugins was added.
Version 1.16 (sudo 1.9.3)
Initial resource limit values were added to the user_info
list.
The cmnd_chroot and cmnd_cwd entries were added to the
settings list.
Version 1.17 (sudo 1.9.4)
The event_alloc() function was added to struct audit_plugin
and struct approval_plugin.
Version 1.18 (sudo 1.9.9)
The policy may now set resource limit values in the
command_info list. The intercept and log_subcmds entries
were added to the command_info list.
Version 1.19 (sudo 1.9.11)
The intercept_ptrace and intercept_setid entries were added
to the settings list. The apparmor_profile and use_ptrace
entries were added to the command_info list.
Version 1.20 (sudo 1.9.12)
The update_ticket entry was added to the settings list.
The intercept_verify entry was added to the command_info
list.
Version 1.21 (sudo 1.9.13)
The sudoedit_nfiles entry was added to the command_info
list.
Version 1.22 (sudo 1.9.16)
The ttydev entry was added to the user_info list.
sudo.conf(5), sudoers(5), sudo(8)
Many people have worked on sudo over the years; this version
consists of code written primarily by:
Todd C. Miller
See the CONTRIBUTORS.md file in the sudo distribution
(https://www.sudo.ws/about/contributors/) for an exhaustive list
of people who have contributed to sudo.
If you believe you have found a bug in , you can either file a
bug report in the sudo bug database, https://bugzilla.sudo.ws/,
or open an issue at https://github.com/sudo-project/sudo/issues.
If you would prefer to use email, messages may be sent to the
sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public) or
<[email protected]> (private).
Please not report security vulnerabilities through public GitHub
issues, Bugzilla or mailing lists. Instead, report them via
email to <[email protected]>. You may encrypt your message
with PGP if you would like, using the key found at
https://www.sudo.ws/dist/PGPKEYS.
Limited free support is available via the sudo-users mailing
list, see https://www.sudo.ws/mailman/listinfo/sudo-users to
subscribe or search the archives.
sudo is provided “AS IS” and any express or implied warranties,
including, but not limited to, the implied warranties of
merchantability and fitness for a particular purpose are
disclaimed. See the LICENSE.md file distributed with sudo or
https://www.sudo.ws/about/license/ for complete details.
This page is part of the sudo (execute a command as another user)
project. Information about the project can be found at
https://www.sudo.ws/. If you have a bug report for this manual
page, see ⟨https://bugzilla.sudo.ws/⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/sudo-project/sudo⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-08.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Sudo 1.9.16 November 25, 2023 SUDO_PLUGIN(5)
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