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NAME | DESCRIPTION | FILES | EXAMPLES | SEE ALSO | AUTHORS | BUGS | SUPPORT | DISCLAIMER | COLOPHON |
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SUDO.CONF(5) File Formats Manual SUDO.CONF(5)
sudo.conf — configuration for sudo front-end
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
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/local/libexec/sudo/sudo_intercept.so
Path noexec /usr/local/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 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 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/local/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/local/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/local/libexec/sudo.
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, 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 (‘,’).
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.
/etc/sudo.conf sudo front-end configuration
#
# Default /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 /usr/local/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/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
sudo_plugin(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 sudo.conf, 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 6, 2023 SUDO.CONF(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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