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.#
’) 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
Plugin sudoers_policy /usr/local/libexec/sudo/sudoers.so
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
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
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
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
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
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_MAX
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.sudo
to only use
the kernel's static list of groups for the user:
Set group_source static
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
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
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
->
’, 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 functionsudo
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:
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.