sudo.conf —
sudo.conf file is used to configure the
sudo front end. It specifies the security policy and
I/O logging plugins, debug flags as well as plugin-agnostic path names and
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. 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.
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 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/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 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 sudo.conf 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
For more information on the sudo plugin
architecture, see the sudo_plugin(5) 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
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./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.
execl(), execle(),
execlp(), exect(),
execv(), execve(),
execvP(), execvp(),
execvpe(), fexecve(),
popen(), posix_spawn(),
posix_spawnp(), system(),
and wordexp() 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: /usr/local/libexec/sudo/sudo_noexec.so.sesh binary. This
setting is only used when sudo is built with
SELinux support. The default value is
/usr/local/libexec/sudo/sesh.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 setuid 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 setuid 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, HP-UX, Linux and Solaris.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 help track down 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
(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
(‘,’).
For example:
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
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 # # 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
sudo distribution
(https://www.sudo.ws/history.html) for a brief history of sudo.
sudo over the years; this
version consists of code written primarily by:
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.
sudo, please submit
a bug report at https://bugzilla.sudo.ws/
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/license.html for complete details.