| SUDO.CONF(5) | File Formats and Configurations | 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.
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.
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/lib/sudo/amd64/sudo. In other words:
Plugin sudoers_policy sudoers.so
is equivalent to:
Plugin sudoers_policy /usr/lib/sudo/amd64/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.
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/lib/sudo/amd64/sudo/sudo_intercept.so Path noexec /usr/lib/sudo/amd64/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:
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.This option is ignored on systems that support
either the
devname()
or
_ttyname_dev()
functions, for example BSD, macOS and
Solaris.
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/lib/sudo/amd64/sudo/sudo_intercept.so.
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/lib/sudo/amd64/sudo/sudo_noexec.so.
The sudo.conf file also supports the
following front-end settings:
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.
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_MAXHowever, 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:
sudo
1.8.7.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.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.
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.
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.
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:
sudo main functionThe sudoers(5) plugin includes support for additional subsystems.
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/lib/sudo/amd64/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(), # execve() and fexecve() library functions, which perform a policy # check to verify whether the command is allowed and simply return # an error if it is 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/lib/sudo/amd64/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/lib/sudo/amd64/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/lib/sudo/amd64/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
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.
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
<sudo@sudo.ws> (private).
Please do not report security vulnerabilities through public GitHub issues, Bugzilla or mailing lists. Instead, report them via email to <Todd.Miller@sudo.ws>. 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.
| November 6, 2023 | Sudo 1.9.17p2 |