Sudo Configuration Manual
configuration for sudo front end
sudo.conf file is used to configure
sudo front end. It specifies the security policy
and I/O logging plugins, debug flags as well as plugin-agnostic path names
sudo.conf file supports the following
directives, described in detail below.
- a security policy or I/O logging plugin
- a plugin-agnostic path
- a front end setting, such as disable_coredump or group_source
- debug flags to aid in debugging
visudo, and the
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. Note that leading white space is removed from the beginning of lines
even when the continuation character is used.
Non-comment lines that don't begin with
Set are silently
sudo.conf file is always parsed in the
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
sudo front end. Plugins are dynamically loaded
based on the contents of
Plugin line consists of
Plugin keyword, followed by the
symbol_name and the path to the shared
object containing the plugin. The symbol_name is the name
struct policy_plugin or
struct io_plugin in the plugin shared object. The
path may be fully qualified or relative. If not fully
qualified, it is relative to the directory specified by the
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
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
The same shared object may contain multiple plugins, each with a different symbol name. The shared object file must be owned by uid 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.
sudo.conf file is present, or if it
Plugin lines, the
sudoers plugin will be used as the default security
policy and for I/O logging (if enabled by the policy). This is equivalent to
Plugin sudoers_policy sudoers.so Plugin sudoers_io sudoers.so
For more information on the
architecture, see the sudo_plugin(8) manual.
Path line consists of the
Path keyword, followed by the name of the path to
set and its value. For example:
Path noexec /usr/local/libexec/sudo/sudo_noexec.so Path askpass /usr/X11R6/bin/ssh-askpass
The following plugin-agnostic paths may be set in the /etc/sudo.conf file:
- 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
sudois 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
- The fully-qualified path to a shared library containing dummy versions of
fexecve() library functions that just return an error. This is used to implement the noexec functionality on systems that support
LD_PRELOADor its equivalent. The default value is: /usr/local/libexec/sudo/sudo_noexec.so.
- 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.
- The fully-qualified path to the
seshbinary. This setting is only used when
sudois built with SELinux support. The default value is /usr/local/libexec/sudo/sesh.
sudo.conf file also supports the
following front end settings:
- Core dumps of
sudoitself are disabled by default. To aid in debugging
sudocrashes, you may wish to re-enable core dumps by setting “disable_coredump” to false in
Set disable_coredump false
Note that most operating systems disable core dumps from setuid programs, including
sudo. To actually get a
sudocore file you will likely need to enable core dumps for setuid processes. On BSD and Linux systems this is accomplished in the sysctl command. On Solaris, the coreadm command is used to configure core dump behavior.
This setting is only available in
sudoversion 1.8.4 and higher.
sudopasses 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.
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
sudoversion 1.8.7, if the user's kernel group list has the maximum number of entries,
sudowill 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:
- 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
- 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
sudosupports efficient group queries on AIX, BSD, HP-UX, Linux and Solaris.
- 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
sudo1.8.7 and higher.
For example, to cause
sudoto only use the kernel's static list of groups for the user:
Set group_source static
This setting is only available in
sudoversion 1.8.7 and higher.
- The maximum number of user groups to retrieve from the group database.
Values less than one 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,
sudowill allocate four times the system's maximum number of groups (see above) and retry with double that number if the group database query fails. However, some systems just return as many entries as will fit and do not indicate an error when there is a lack of space.
This setting is only available in
sudoversion 1.8.7 and higher.
sudo versions 1.8.4 and higher support a
flexible debugging framework that can help track down what
sudo is doing internally if there is a problem.
Debug line consists of
Debug keyword, followed by the name of the
program (or plugin) to debug (
sudoers), the debug file name and a comma-separated
list of debug flags. The debug flag syntax used by
sudo and the
but a plugin is free to use a different format so long as it does not
include a comma (‘
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.
Currently, only one
Debug entry per
program is supported. The
Debug entry is shared by the
sudo front end,
the plugins. A future release may add support for per-plugin
Debug lines and/or support for multiple debugging
files for a single program.
The priorities used by the
front end, in order of decreasing severity, are:
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 following subsystems are used by the
- matches every subsystem
- command line argument processing
- user conversation
- command execution
- network interface handling
- communication with the plugin
- plugin configuration
- pseudo-tty related code
- SELinux-specific handling
- utility functions
- utmp handling
The sudoers(5) plugin includes support for additional subsystems.
sudofront end configuration
# # Default /etc/sudo.conf file # # Format: # Plugin plugin_name plugin_path plugin_options ... # Path askpass /path/to/askpass # Path noexec /path/to/sudo_noexec.so # Debug sudo /var/log/sudo_debug all@warn # Set disable_coredump true # # 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
# # Sudo 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 noexec: # # Path to a shared library containing dummy versions of the execv(), # execve() and fexecve() library functions that just return an error. # This is used to implement the "noexec" functionality on systems that # support C<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
# # Core dumps: # # 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: # # 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
See the HISTORY file in the
distribution (https://www.sudo.ws/sudo/history.html) for a brief history of
Many people have worked on
sudo over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS file in the
distribution (https://www.sudo.ws/sudo/contributors.html) for an exhaustive
list of people who have contributed to
If you feel you have found a bug in
please submit a bug report at https://www.sudo.ws/sudo/bugs/
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 file distributed with
sudo or https://www.sudo.ws/sudo/license.html for