table of contents
- bookworm 1.9.13p3-1+deb12u1
- bookworm 1.9.13p3-1+deb12u1
- testing 1.9.15p5-3+b1
- testing 1.9.15p5-3+b1
- unstable 1.9.15p5-3+b1
- unstable 1.9.15p5-3+b1
- experimental 1.9.16-1
- experimental 1.9.16-1
SUDO.CONF(5) | File Formats Manual | SUDO.CONF(5) |
NAME¶
sudo.conf
—
configuration for sudo front-end
DESCRIPTION¶
The sudo.conf
file is used to configure
the sudo
front-end. It is used to configure sudo
plugins, plugin-agnostic path names, debug flags, and other settings.
The sudo.conf
file supports the following
directives, described in detail below.
- Plugin
- an approval, audit, I/O logging, or security policy plugin
- Path
- a plugin-agnostic path
- Set
- a front-end setting, such as disable_coredump or group_source
- Debug
- debug flags to aid in debugging
sudo
,sudoreplay
,visudo
, and thesudoers
plugin.
The pound sign (‘#
’) is used
to indicate a comment. Both the comment character and any text after it, up
to the end of the line, are ignored.
Long lines can be continued with a backslash
(‘\
’) as the last character on the
line. Leading white space is removed from the beginning of lines even when a
continuation character is used.
Non-comment lines that don't begin with Plugin, Path, Debug, or Set are silently ignored.
The sudo.conf
file is always parsed in the
‘C
’ locale.
Plugin configuration¶
sudo
supports a plugin architecture for
security policies and input/output logging. Third parties can develop and
distribute their own policy and I/O logging plugins to work seamlessly with
the sudo
front-end. Plugins are dynamically loaded
based on the contents of sudo.conf
.
A Plugin line consists of the Plugin keyword, followed by the symbol_name and the path to the dynamic shared object that contains the plugin. The symbol_name is the name of the struct approval_plugin, struct audit_plugin, struct io_plugin, or struct policy_plugin defined by the plugin. If a plugin implements multiple plugin types, there must be a Plugin line for each unique symbol name. The path may be fully qualified or relative. If not fully qualified, it is relative to the directory specified by the plugin_dir Path setting, which defaults to /usr/libexec/sudo. In other words:
Plugin sudoers_policy sudoers.so
is equivalent to:
Plugin sudoers_policy /usr/libexec/sudo/sudoers.so
If the plugin was compiled statically into the
sudo
binary instead of being installed as a dynamic
shared object, the path should be specified without a
leading directory, as it does not actually exist in the file system. For
example:
Plugin sudoers_policy sudoers.so
On AIX systems, the plugin may be either a shared object ending in
‘.so
’ or an archive file containing a
shared object ending in ‘.a
’ with the
name of the shared object in parentheses at the end.
Starting with sudo
1.8.5, any
additional parameters after the path are passed as
arguments to the plugin's
open function. For
example, to override the compile-time default sudoers file mode:
Plugin sudoers_policy sudoers.so sudoers_mode=0440
See the sudoers(5) manual for a list of supported arguments.
The same dynamic shared object may contain multiple plugins, each with a different symbol name. The file must be owned by user-ID 0 and only writable by its owner. Because of ambiguities that arise from composite policies, only a single policy plugin may be specified. This limitation does not apply to I/O plugins.
If no sudo.conf
file is present, or if it
contains no Plugin lines, the
sudoers
plugin will be used as the default security
policy, for I/O logging (if enabled by the policy), and for auditing. This
is equivalent to the following:
Plugin sudoers_policy sudoers.so Plugin sudoers_io sudoers.so Plugin sudoers_audit sudoers.so
Starting with sudo
version 1.9.1, some of
the logging functionality of the sudoers
plugin has
been moved from the policy plugin to an audit plugin. To maintain
compatibility with sudo.conf
files from older
sudo
versions, if sudoers
is
configured as the security policy, it will be used as an audit plugin as
well. This guarantees that the logging behavior will be consistent with that
of sudo
versions 1.9.0 and below.
For more information on the sudo
plugin
architecture, see the sudo_plugin(5) manual.
Path settings¶
A Path line consists of the Path keyword, followed by the name of the path to set and its value. For example:
Path intercept /usr/libexec/sudo/sudo_intercept.so Path noexec /usr/libexec/sudo/sudo_noexec.so Path askpass /usr/X11R6/bin/ssh-askpass
If no path name is specified, features relying on the specified
setting will be disabled. Disabling Path settings is only
supported in sudo
version 1.8.16 and higher.
The following plugin-agnostic paths may be set in the /etc/sudo.conf file:
- askpass
- The fully qualified path to a helper program used to read the user's
password when no terminal is available. This may be the case when
sudo
is executed from a graphical (as opposed to text-based) application. The program specified by askpass should display the argument passed to it as the prompt and write the user's password to the standard output. The value of askpass may be overridden by theSUDO_ASKPASS
environment variable. - devsearch
- An ordered, colon-separated search path of directories to look in for
device nodes. This is used when mapping the process's tty device number to
a device name on systems that do not provide such a mechanism. Sudo will
not recurse into
sub-directories. If terminal devices may be located in a sub-directory of
/dev, that path must be explicitly listed in
devsearch.
The default value is
/dev/pts:/dev/vt:/dev/term:/dev/zcons:/dev/pty:/dev
This option is ignored on systems that support either the
devname
() or_ttyname_dev
() functions, for example BSD, macOS and Solaris. - intercept
- The path to a shared library containing a wrappers for the
execve(2), execl(3),
execle(3), execlp(3),
execv(3), execvp(3),
execvpe(3), and system(3) library
functions that intercepts attempts to run further commands and performs a
policy check before allowing them to be executed. This is used to
implement the intercept and
log_subcmds
functionality on systems that support
LD_PRELOAD
or the equivalent.The intercept path may be set to either a single fully-qualified path, or, for systems that support separate
LD_PRELOAD
environment variables for 32-bit and 64-bit executables, it may optionally be set to two fully-qualified paths separated by a colon (‘:
’). The first path should be the 32-bit version and the second the 64-bit version. This two-path form is currently only supported on AIX and Solaris systems. The default value is /usr/libexec/sudo/sudo_intercept.so. - noexec
- The path to a shared library containing wrappers for the
execve(2), execl(3),
execle(3), execlp(3),
exect(3), execv(3),
execveat(3), execvP(3),
execvp(3), execvpe(3),
fexecve(3), popen(3),
posix_spawn(3), posix_spawnp(3),
system(3), and wordexp(3) library
functions that prevent the execution of further commands. This is used to
implement the noexec functionality on systems that
support
LD_PRELOAD
or the equivalent.The noexec path may be set to either a single fully-qualified path, or, for systems that support separate
LD_PRELOAD
environment variables for 32-bit and 64-bit executables, it may optionally be set to two fully-qualified paths separated by a colon (‘:
’). The first path should be the 32-bit version and the second the 64-bit version. This two-path form is currently only supported on AIX and Solaris systems. The default value is /usr/libexec/sudo/sudo_noexec.so. - plugin_dir
- The default directory to use when searching for plugins that are specified without a fully qualified path name. The default value is /usr/libexec/sudo.
- sesh
- The fully-qualified path to the
sesh
binary. This setting is only used whensudo
is built with SELinux support. The default value is /usr/libexec/sudo/sesh.
Other settings¶
The sudo.conf
file also supports the
following front-end settings:
- disable_coredump
- Core dumps of
sudo
itself are disabled by default to prevent the disclosure of potentially sensitive information. To aid in debuggingsudo
crashes, you may wish to re-enable core dumps by setting “disable_coredump” to false insudo.conf
as follows:Set disable_coredump false
All modern operating systems place restrictions on core dumps from set-user-ID processes like
sudo
so this option can be enabled without compromising security. To actually get asudo
core file you will likely need to enable core dumps for set-user-ID processes. On BSD and Linux systems this is accomplished in the sysctl(8) command. On Solaris, the coreadm(1m) command is used to configure core dump behavior.This setting is only available in
sudo
version 1.8.4 and higher. - group_source
sudo
passes the invoking user's group list to the policy and I/O plugins. On most systems, there is an upper limit to the number of groups that a user may belong to simultaneously (typically 16 for compatibility with NFS). On systems with the getconf(1) utility, running:will return the maximum number of groups.getconf NGROUPS_MAX
However, it is still possible to be a member of a larger number of groups--they simply won't be included in the group list returned by the kernel for the user. Starting with
sudo
version 1.8.7, if the user's kernel group list has the maximum number of entries,sudo
will consult the group database directly to determine the group list. This makes it possible for the security policy to perform matching by group name even when the user is a member of more than the maximum number of groups.The group_source setting allows the administrator to change this default behavior. Supported values for group_source are:
- static
- Use the static group list that the kernel returns. Retrieving the
group list this way is very fast but it is subject to an upper limit
as described above. It is “static” in that it does not
reflect changes to the group database made after the user logs in.
This was the default behavior prior to
sudo
1.8.7. - dynamic
- Always query the group database directly. It is
“dynamic” in that changes made to the group database
after the user logs in will be reflected in the group list. On some
systems, querying the group database for all of a user's groups can be
time consuming when querying a network-based group database. Most
operating systems provide an efficient method of performing such
queries. Currently,
sudo
supports efficient group queries on AIX, BSD, Linux, macOS, and Solaris. This is the default behavior on macOS insudo
1.9.6 and higher. - adaptive
- Only query the group database if the static group list returned by the
kernel has the maximum number of entries. This is the default behavior
on systems other than macOS in
sudo
1.8.7 and higher.
For example, to cause
sudo
to only use the kernel's static list of groups for the user:Set group_source static
This setting is only available in
sudo
version 1.8.7 and higher.- max_groups
- The maximum number of user groups to retrieve from the group database.
Values less than one or larger than 1024 will be ignored. This setting is
only used when querying the group database directly. It is intended to be
used on systems where it is not possible to detect when the array to be
populated with group entries is not sufficiently large. By default,
sudo
will allocate four times the system's maximum number of groups (see above) and retry with double that number if the group database query fails.This setting is only available in
sudo
version 1.8.7 and higher. It should not be required insudo
versions 1.8.24 and higher and may be removed in a later release. - probe_interfaces
- By default,
sudo
will probe the system's network interfaces and pass the IP address of each enabled interface to the policy plugin. This makes it possible for the plugin to match rules based on the IP address without having to query DNS. On Linux systems with a large number of virtual interfaces, this may take a non-negligible amount of time. If IP-based matching is not required, network interface probing can be disabled as follows:Set probe_interfaces false
This setting is only available in
sudo
version 1.8.10 and higher.
Debug settings¶
sudo
versions 1.8.4 and higher support a
flexible debugging framework that can log what sudo
is doing internally if there is a problem.
A Debug line consists of the
Debug keyword, followed by the name of the program,
plugin, or shared object to debug, the debug file name, and a
comma-separated list of debug flags. The debug flag syntax used by
sudo
, the sudoers
plugin
along with its associated programs and shared objects is
subsystem@priority
but a third-party plugin is free to use a different format so long as it
does not include a comma (‘,
’).
On AIX systems, a Debug line will match a plugin
specified as either the name of an SVR4-style shared object file ending in
‘.so
’, an archive file ending in
‘.a
’, or an archive file ending in
‘.a
’ with the name of the shared
object in parentheses.
Examples:
Debug sudo /var/log/sudo_debug all@warn,plugin@info
would log all debugging statements at the warn level and higher in addition to those at the info level for the plugin subsystem.
Debug sudo_intercept.so /var/log/intercept_debug all@debug
would log all debugging statements, regardless of level, for the
sudo_intercept.so shared library that implements
sudo
's intercept functionality on some systems.
Debug sudoers.so /var/log/sudoers_debug all@debug
would log all debugging statements, regardless of level, for the
sudoers
plugin. See sudoers(5) for
the full list of subsystems supported by the sudoers
plugin.
As of sudo
1.8.12, multiple
Debug entries may be specified per program. Older versions
of sudo
only support a single
Debug entry per program. Plugin-specific
Debug entries are also supported starting with
sudo
1.8.12 and are matched by either the base name
of the plugin that was loaded (for example
sudoers.so) or by the plugin's fully-qualified path
name. Previously, the sudoers
plugin shared the same
Debug entry as the sudo
front-end
and could not be configured separately.
The following priorities are supported, in order of decreasing severity: crit, err, warn, notice, diag, info, trace, and debug. Each priority, when specified, also includes all priorities higher than it. For example, a priority of notice would include debug messages logged at notice and higher.
The priorities trace and
debug also include function call tracing which logs when a
function is entered and when it returns. For example, the following trace is
for the
get_user_groups
()
function located in src/sudo.c:
sudo[123] -> get_user_groups @ src/sudo.c:385 sudo[123] <- get_user_groups @ src/sudo.c:429 := groups=10,0,5
When the function is entered, indicated by a right arrow
‘->
’, the program, process ID,
function, source file, and line number are logged. When the function
returns, indicated by a left arrow
‘<-
’, the same information is
logged along with the return value. In this case, the return value is a
string.
The following subsystems are used by the
sudo
front-end:
- all
- matches every subsystem
- args
- command line argument processing
- conv
- user conversation
- edit
- sudoedit
- event
- event subsystem
- exec
- command execution
- main
sudo
main function- netif
- network interface handling
- pcomm
- communication with the plugin
- plugin
- plugin configuration
- pty
- pseudo-terminal related code
- selinux
- SELinux-specific handling
- util
- utility functions
- utmp
- utmp handling
The sudoers(5) plugin includes support for additional subsystems.
FILES¶
- /etc/sudo.conf
sudo
front-end configuration
EXAMPLES¶
# # Default /etc/sudo.conf file # # Sudo plugins: # Plugin plugin_name plugin_path plugin_options ... # # The plugin_path is relative to /usr/libexec/sudo unless # fully qualified. # The plugin_name corresponds to a global symbol in the plugin # that contains the plugin interface structure. # The plugin_options are optional. # # The sudoers plugin is used by default if no Plugin lines are present. #Plugin sudoers_policy sudoers.so #Plugin sudoers_io sudoers.so #Plugin sudoers_audit sudoers.so # # Sudo askpass: # Path askpass /path/to/askpass # # An askpass helper program may be specified to provide a graphical # password prompt for "sudo -A" support. Sudo does not ship with its # own askpass program but can use the OpenSSH askpass. # # Use the OpenSSH askpass #Path askpass /usr/X11R6/bin/ssh-askpass # # Use the Gnome OpenSSH askpass #Path askpass /usr/libexec/openssh/gnome-ssh-askpass # # Sudo device search path: # Path devsearch /dev/path1:/dev/path2:/dev # # A colon-separated list of paths to check when searching for a user's # terminal device. # #Path devsearch /dev/pts:/dev/vt:/dev/term:/dev/zcons:/dev/pty:/dev # # Sudo command interception: # Path intercept /path/to/sudo_intercept.so # # Path to a shared library containing replacements for the execv() # and execve() library functions that perform a policy check to verify # the command is allowed and simply return an error if not. This is # used to implement the "intercept" functionality on systems that # support LD_PRELOAD or its equivalent. # # The compiled-in value is usually sufficient and should only be changed # if you rename or move the sudo_intercept.so file. # #Path intercept /usr/libexec/sudo/sudo_intercept.so # # Sudo noexec: # Path noexec /path/to/sudo_noexec.so # # Path to a shared library containing replacements for the execv() # family of library functions that just return an error. This is # used to implement the "noexec" functionality on systems that support # LD_PRELOAD or its equivalent. # # The compiled-in value is usually sufficient and should only be changed # if you rename or move the sudo_noexec.so file. # #Path noexec /usr/libexec/sudo/sudo_noexec.so # # Sudo plugin directory: # Path plugin_dir /path/to/plugins # # The default directory to use when searching for plugins that are # specified without a fully qualified path name. # #Path plugin_dir /usr/libexec/sudo # # Core dumps: # Set disable_coredump true|false # # By default, sudo disables core dumps while it is executing (they # are re-enabled for the command that is run). # To aid in debugging sudo problems, you may wish to enable core # dumps by setting "disable_coredump" to false. # #Set disable_coredump false # # User groups: # Set group_source static|dynamic|adaptive # # Sudo passes the user's group list to the policy plugin. # If the user is a member of the maximum number of groups (usually 16), # sudo will query the group database directly to be sure to include # the full list of groups. # # On some systems, this can be expensive so the behavior is configurable. # The "group_source" setting has three possible values: # static - use the user's list of groups returned by the kernel. # dynamic - query the group database to find the list of groups. # adaptive - if user is in less than the maximum number of groups. # use the kernel list, else query the group database. # #Set group_source static # # Sudo interface probing: # Set probe_interfaces true|false # # By default, sudo will probe the system's network interfaces and # pass the IP address of each enabled interface to the policy plugin. # On systems with a large number of virtual interfaces this may take # a noticeable amount of time. # #Set probe_interfaces false # # Sudo debug files: # Debug program /path/to/debug_log subsystem@priority[,subsyste@priority] # # Sudo and related programs support logging debug information to a file. # The program is typically sudo, sudoers.so, sudoreplay, or visudo. # # Subsystems vary based on the program; "all" matches all subsystems. # Priority may be crit, err, warn, notice, diag, info, trace, or debug. # Multiple subsystem@priority may be specified, separated by a comma. # #Debug sudo /var/log/sudo_debug all@debug #Debug sudoers.so /var/log/sudoers_debug all@debug
SEE ALSO¶
AUTHORS¶
Many people have worked on sudo
over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS.md file in the sudo
distribution (https://www.sudo.ws/about/contributors/) for an exhaustive
list of people who have contributed to sudo
.
BUGS¶
If you believe you have found a bug in
sudo
, you can submit a bug report at
https://bugzilla.sudo.ws/
SUPPORT¶
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.
DISCLAIMER¶
sudo
is provided “AS IS” and
any express or implied warranties, including, but not limited to, the
implied warranties of merchantability and fitness for a particular purpose
are disclaimed. See the LICENSE.md file distributed with
sudo
or https://www.sudo.ws/about/license/ for
complete details.
November 6, 2023 | Sudo 1.9.15p5 |