sudo.conf(5)
NAME
sudo.conf --- configuration for sudo front end
DESCRIPTION
The 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.
Plugin a security policy or I/O logging plugin
Path a plugin-agnostic path
Set a front end setting, such as disable_coredump or group_source
Debug debug flags to aid in debugging 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.
Plugin configuration
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/lib/sudo. In other words:
Plugin sudoers_policy sudoers.so
is equivalent to:
Plugin sudoers_policy /usr/lib/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
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(8) manual.
Path settings
A Path line consists of the Path keyword, followed by the name of the
path to set and its value. For example:
Path noexec /usr/lib/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:
askpass 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 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.
noexec The fully-qualified path to a shared library containing dummy
versions of the execl(), execle(), execlp(), exect(), execv(),
execve(), execvP(), execvp(), execvpe(), fexecve(), popen(),
posix_spawn(), posix_spawnp(), and system() 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 default value is:
/usr/lib/sudo/sudo_noexec.so.
plugin_dir
The default directory to use when searching for plugins that
are specified without a fully qualified path name. The default
value is /usr/lib/sudo.
sesh The fully-qualified path to the sesh binary. This setting is
only used when sudo is built with SELinux support. The default
value is /usr/lib/sudo/sesh.
Other settings
The sudo.conf file also supports the following front end settings:
disable_coredump
Core dumps of 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 command. On Solaris, the coreadm command is used to
configure core dump behavior.
This setting is only available in sudo version 1.8.4 and
higher.
group_source
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
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 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:
static 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 sudo 1.8.7.
dynamic 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 queries. Currently, sudo supports
efficient group queries on AIX, BSD, HP-UX, Linux and
Solaris.
adaptive 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 in 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.
max_groups
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, 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.
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 sudo version 1.8.7 and
higher.
probe_interfaces
By default, 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.
Debug flags
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:
all matches every subsystem
args command line argument processing
conv user conversation
edit sudoedit
event event subsystem
exec command execution
main sudo main function
netif network interface handling
pcomm communication with the plugin
plugin plugin configuration
pty pseudo-tty related code
selinux SELinux-specific handling
util utility functions
utmp utmp handling
The sudoers(5) plugin includes support for additional subsystems.
FILES
/etc/sudo.conf sudo front end configuration
EXAMPLES
#
# 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/lib/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/lib/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 ALSO
sudoers(5), sudo(8), sudo_plugin(8)
HISTORY
See the HISTORY file in the sudo distribution
(https://www.sudo.ws/history.html) for a brief history of sudo.
AUTHORS
Many people have worked on sudo over the years; this version consists of
code written primarily by:
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.
BUGS
If you feel you have found a bug in sudo, please submit a bug report at
https://bugzilla.sudo.ws/
SUPPORT
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.
DISCLAIMER
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.
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