|SUDO.CONF(5)||File Formats Manual||SUDO.CONF(5)|
configuration for sudo front end
sudo.conffile is used to configure the
sudofront end. It specifies the security policy and I/O logging plugins, debug flags as well as plugin-agnostic path names and settings. The
sudo.conffile 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
#’) 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
Setare silently ignored. The
sudo.conffile is always parsed in the “
sudosupports 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
sudofront end. Plugins are dynamically loaded based on the contents of
Pluginline consists of the
Pluginkeyword, 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 io_pluginsymbol 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
Pathsetting, which defaults to /usr/lib/sudo. In other words:
Plugin sudoers_policy sudoers.so
Plugin sudoers_policy /usr/lib/sudo/sudoers.so
sudobinary 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
sudo1.8.5, 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.conffile is present, or if it contains no
sudoersplugin 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
sudoplugin architecture, see the sudo_plugin(8) manual.
Pathline consists of the
Pathkeyword, 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
Pathsettings is only supported in
sudoversion 1.8.16 and higher. 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 wrappers for the
wordexp() library functions that prevent the execution of further commands. This is used to implement the noexec functionality on systems that support
LD_PRELOADor its equivalent. The default value is: /usr/lib/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/lib/sudo.
- The fully-qualified path to the
seshbinary. This setting is only used when
sudois built with SELinux support. The default value is /usr/lib/sudo/sesh.
sudo.conffile also supports the following front end settings:
- Core dumps of
sudoitself are disabled by default to prevent the disclosure of potentially sensitive information. To aid in debugging
sudocrashes, you may wish to re-enable core dumps by setting “disable_coredump” to false in
Set disable_coredump false
sudoso this option can be enabled without compromising security. 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.
sudoto only use the kernel's static list of groups for the user:
Set group_source static
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.
- By default,
sudowill 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
sudoversion 1.8.10 and higher.
sudoversions 1.8.4 and higher support a flexible debugging framework that can help track down what
sudois doing internally if there is a problem. A
Debugline consists of the
Debugkeyword, 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
sudoersplugin 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
Debugentries may be specified per program. Older versions of
sudoonly support a single
Debugentry per program. Plugin-specific
Debugentries are also supported starting with
sudo1.8.12 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
sudoersplugin shared the same
Debugentry as the
sudofront 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 -> get_user_groups @ src/sudo.c:385 sudo <- 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
- matches every subsystem
- command line argument processing
- user conversation
- event subsystem
- command execution
- network interface handling
- communication with the plugin
- plugin configuration
- pseudo-tty related code
- SELinux-specific handling
- utility functions
- utmp handling
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/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
sudodistribution (https://www.sudo.ws/history.html) for a brief history of sudo.
AUTHORS¶Many people have worked on
sudoover the years; this version consists of code written primarily by:
Todd C. MillerSee the CONTRIBUTORS file in the
sudodistribution (https://www.sudo.ws/contributors.html) for an exhaustive list of people who have contributed to
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.
sudois 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
sudoor https://www.sudo.ws/license.html for complete details.
|October 15, 2016||Sudo 1.8.19p1|