The file supports the following directives, described in detail below.
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 Plugin Path Debug or Set are silently ignored.
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 policy_plugin or struct io_plugin symbol contained in the plugin. 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
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 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.
If no file is present, or if it contains no 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 the following:
Plugin sudoers_policy sudoers.so Plugin sudoers_io sudoers.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:
This option is ignored on systems that support either the Fn devname or Fn _ttyname_dev functions, for example BSD , macOS and Solaris.
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.
getconf NGROUPS_MAXwill 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:
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.
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.
Set probe_interfaces false
This setting is only available in sudo version 1.8.10 and higher.
A Debug line consists of the Debug keyword, followed by the name of the program (or plugin) to debug (sudo , visudo , sudoreplay , sudoers ) the debug file name and a comma-separated list of debug flags. The debug flag syntax used by sudo and the sudoers plugin is subsystem @ priority 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.
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 Fn get_user_groups function located in src/sudo.c:
sudo -> get_user_groups @ src/sudo.c:385 sudo <- 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:
The sudoers(5) plugin includes support for additional subsystems.
# # 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/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/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
An Todd C. Miller
See the CONTRIBUTORS file in the sudo distribution (https://www.sudo.ws/contributors.html) for an exhaustive list of people who have contributed to sudo