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
the sudoers 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/local/libexec/sudo. In other words:
Plugin sudoers_policy sudoers.so
is equivalent to:
Plugin sudoers_policy /usr/local/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
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 consistnet 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/local/libexec/sudo/sudo_intercept.so
Path noexec disabled
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 /privat
e/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 the SUDO_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 fully-qualified 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 functionality on systems that support
LD_PRELOAD or its equivalent. The default value is
/usr/local/libexec/sudo/sudo_intercept.so.
noexec
The fully-qualified 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 its
equivalent. The default value is disabled.
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/local/libexec/sudo.
sesh The fully-qualified path to the sesh binary. This setting is
only used when sudo is built with SELinux support. The default
value is /usr/local/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
debugging sudo crashes, you may wish to re-enable core dumps by
setting “disable_coredump” to false in sudo.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 a sudo
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:
getconf NGROUPS_MAX
will return the maximum number of groups.
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, HP-UX,
Linux, macOS, and Solaris. This is the default behavior on
macOS in sudo 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 in sudo 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 (‘,’).
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.
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
/privat e/etc/sudo.conf sudo front-end configuration
EXAMPLES
#
# Default /privat
e/etc/sudo.conf file
#
# Sudo plugins:
# Plugin plugin_name plugin_path plugin_options ...
#
# The plugin_path is relative to /usr/local/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/local/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 disabled
#
# 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/local/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
sudo_plugin(5), sudoers(5), sudo(8)
AUTHORS
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.
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.
Sudo 1.9.13p2 January 16, 2023 SUDO.CONF(5)