path: root/doc/sudo.conf.man.in

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.\" Copyright (c) 2010-2018 Todd C. Miller <Todd.Miller@sudo.ws>
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.TH "SUDO.CONF" "@mansectform@" "October 7, 2018" "Sudo @PACKAGE_VERSION@" "File Formats Manual"
.nh
.if n .ad l
.SH "NAME"
\fBsudo.conf\fR
\- configuration for sudo front end
.SH "DESCRIPTION"
The
\fBsudo.conf\fR
file is used to configure the
\fBsudo\fR
front end.
It specifies the security policy and I/O logging plugins, debug flags
as well as plugin-agnostic path names and settings.
.PP
The
\fBsudo.conf\fR
file supports the following directives, described in detail below.
.TP 10n
Plugin
a security policy or I/O logging plugin
.TP 10n
Path
a plugin-agnostic path
.TP 10n
Set
a front end setting, such as
\fIdisable_coredump\fR
or
\fIgroup_source\fR
.TP 10n
Debug
debug flags to aid in debugging
\fBsudo\fR,
\fBsudoreplay\fR,
\fBvisudo\fR,
and the
\fBsudoers\fR
plugin.
.PP
The pound sign
(\(oq#\(cq)
is used to indicate a comment.
Both the comment character and any text after it, up to the end of
the line, are ignored.
.PP
Long lines can be continued with a backslash
(\(oq\e\(cq)
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.
.PP
Non-comment lines that don't begin with
\fRPlugin\fR,
\fRPath\fR,
\fRDebug\fR,
or
\fRSet\fR
are silently ignored.
.PP
The
\fBsudo.conf\fR
file is always parsed in the
\(lq\fRC\fR\(rq
locale.
.SS "Plugin configuration"
\fBsudo\fR
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
\fBsudo\fR
front end.
Plugins are dynamically loaded based on the contents of
\fBsudo.conf\fR.
.PP
A
\fRPlugin\fR
line consists of the
\fRPlugin\fR
keyword, followed by the
\fIsymbol_name\fR
and the
\fIpath\fR
to the dynamic shared object that contains the plugin.
The
\fIsymbol_name\fR
is the name of the
\fRstruct policy_plugin\fR
or
\fRstruct io_plugin\fR
symbol contained in the plugin.
The
\fIpath\fR
may be fully qualified or relative.
If not fully qualified, it is relative to the directory
specified by the
\fIplugin_dir\fR
\fRPath\fR
setting, which defaults to
\fI@PLUGINDIR@\fR.
In other words:
.nf
.sp
.RS 6n
Plugin sudoers_policy sudoers.so
.RE
.fi
.PP
is equivalent to:
.nf
.sp
.RS 6n
Plugin sudoers_policy @PLUGINDIR@/sudoers.so
.RE
.fi
.PP
If the plugin was compiled statically into the
\fBsudo\fR
binary instead of being installed as a dynamic shared object, the
\fIpath\fR
should be specified without a leading directory,
as it does not actually exist in the file system.
For example:
.nf
.sp
.RS 6n
Plugin sudoers_policy sudoers.so
.RE
.fi
.PP
Starting with
\fBsudo\fR
1.8.5, any additional parameters after the
\fIpath\fR
are passed as arguments to the plugin's
\fIopen\fR
function.
For example, to override the compile-time default sudoers file mode:
.nf
.sp
.RS 6n
Plugin sudoers_policy sudoers.so sudoers_mode=0440
.RE
.fi
.PP
See the
sudoers(@mansectform@)
manual for a list of supported arguments.
.PP
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.
.PP
If no
\fBsudo.conf\fR
file is present, or if it contains no
\fRPlugin\fR
lines, the
\fBsudoers\fR
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:
.nf
.sp
.RS 6n
Plugin sudoers_policy sudoers.so
Plugin sudoers_io sudoers.so
.RE
.fi
.PP
For more information on the
\fBsudo\fR
plugin architecture, see the
sudo_plugin(@mansectform@)
manual.
.SS "Path settings"
A
\fRPath\fR
line consists of the
\fRPath\fR
keyword, followed by the name of the path to set and its value.
For example:
.nf
.sp
.RS 6n
Path noexec @noexec_file@
Path askpass /usr/X11R6/bin/ssh-askpass
.RE
.fi
.PP
If no path name is specified, features relying on the specified
setting will be disabled.
Disabling
\fRPath\fR
settings is only supported in
\fBsudo\fR
version 1.8.16 and higher.
.PP
The following plugin-agnostic paths may be set in the
\fI@sysconfdir@/sudo.conf\fR
file:
.TP 10n
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
\fBsudo\fR
is executed from a graphical (as opposed to text-based) application.
The program specified by
\fIaskpass\fR
should display the argument passed to it as the prompt and write
the user's password to the standard output.
The value of
\fIaskpass\fR
may be overridden by the
\fRSUDO_ASKPASS\fR
environment variable.
.TP 10n
devsearch
.br
An ordered, colon-separated search path of directories to look in for
device nodes.
This is used when mapping the process's tty device number to a device name
on systems that do not provide such a mechanism.
Sudo will
\fInot\fR
recurse into sub-directories.
If terminal devices may be located in a sub-directory of
\fI/dev\fR,
that path must be explicitly listed in
\fIdevsearch\fR.
The default value is:
\fR/dev/pts:/dev/vt:/dev/term:/dev/zcons:/dev/pty:/dev\fR
.sp
This option is ignored on systems that support either the
\fBdevname\fR()
or
\fB_ttyname_dev\fR()
functions, for example
BSD,
macOS and Solaris.
.TP 10n
noexec
The fully-qualified path to a shared library containing wrappers
for the
\fBexecl\fR(),
\fBexecle\fR(),
\fBexeclp\fR(),
\fBexect\fR(),
\fBexecv\fR(),
\fBexecve\fR(),
\fBexecvP\fR(),
\fBexecvp\fR(),
\fBexecvpe\fR(),
\fBfexecve\fR(),
\fBpopen\fR(),
\fBposix_spawn\fR(),
\fBposix_spawnp\fR(),
\fBsystem\fR(),
and
\fBwordexp\fR()
library functions that prevent the execution of further commands.
This is used to implement the
\fInoexec\fR
functionality on systems that support
\fRLD_PRELOAD\fR
or its equivalent.
The default value is:
\fI@noexec_file@\fR.
.TP 10n
plugin_dir
The default directory to use when searching for plugins
that are specified without a fully qualified path name.
The default value is
\fI@PLUGINDIR@\fR.
.TP 10n
sesh
The fully-qualified path to the
\fBsesh\fR
binary.
This setting is only used when
\fBsudo\fR
is built with SELinux support.
The default value is
\fI@sesh_file@\fR.
.SS "Other settings"
The
\fBsudo.conf\fR
file also supports the following front end settings:
.TP 10n
disable_coredump
Core dumps of
\fBsudo\fR
itself are disabled by default to prevent the disclosure of potentially
sensitive information.
To aid in debugging
\fBsudo\fR
crashes, you may wish to re-enable core dumps by setting
\(lqdisable_coredump\(rq
to false in
\fBsudo.conf\fR
as follows:
.nf
.sp
.RS 16n
Set disable_coredump false
.RE
.fi
.RS 10n
.sp
All modern operating systems place restrictions on core dumps
from setuid processes like
\fBsudo\fR
so this option can be enabled without compromising security.
To actually get a
\fBsudo\fR
core file you will likely need to enable core dumps for setuid processes.
On
BSD
and Linux systems this is accomplished in the
sysctl(@mansectsu@)
command.
On Solaris, the
coreadm(1m)
command is used to configure core dump behavior.
.sp
This setting is only available in
\fBsudo\fR
version 1.8.4 and higher.
.RE
.TP 10n
group_source
\fBsudo\fR
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:
.RS 16n
getconf NGROUPS_MAX
.RE
.RS 10n
will return the maximum number of groups.
.sp
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
\fBsudo\fR
version 1.8.7, if the user's kernel group list has the maximum number
of entries,
\fBsudo\fR
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.
.sp
The
\fIgroup_source\fR
setting allows the administrator to change this default behavior.
Supported values for
\fIgroup_source\fR
are:
.TP 10n
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
\(lqstatic\(rq
in that it does not reflect changes to the group database made
after the user logs in.
This was the default behavior prior to
\fBsudo\fR
1.8.7.
.TP 10n
dynamic
Always query the group database directly.
It is
\(lqdynamic\(rq
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,
\fBsudo\fR
supports efficient group queries on AIX,
BSD,
HP-UX, Linux and Solaris.
.TP 10n
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
\fBsudo\fR
1.8.7 and higher.
.PP
For example, to cause
\fBsudo\fR
to only use the kernel's static list of groups for the user:
.nf
.sp
.RS 16n
Set group_source static
.RE
.fi
.sp
This setting is only available in
\fBsudo\fR
version 1.8.7 and higher.
.RE
.TP 10n
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,
\fBsudo\fR
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.
.sp
This setting is only available in
\fBsudo\fR
version 1.8.7 and higher.
It should not be required in
\fBsudo\fR
versions 1.8.24 and higher and may be removed in a later release.
.TP 10n
probe_interfaces
By default,
\fBsudo\fR
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:
.nf
.sp
.RS 16n
Set probe_interfaces false
.RE
.fi
.RS 10n
.sp
This setting is only available in
\fBsudo\fR
version 1.8.10 and higher.
.RE
.SS "Debug flags"
\fBsudo\fR
versions 1.8.4 and higher support a flexible debugging framework
that can help track down what
\fBsudo\fR
is doing internally if there is a problem.
.PP
A
\fRDebug\fR
line consists of the
\fRDebug\fR
keyword, followed by the name of the program (or plugin) to debug
(\fBsudo\fR, \fBvisudo\fR, \fBsudoreplay\fR, \fBsudoers\fR),
the debug file name and a comma-separated list of debug flags.
The debug flag syntax used by
\fBsudo\fR
and the
\fBsudoers\fR
plugin is
\fIsubsystem\fR@\fIpriority\fR
but a plugin is free to use a different format so long as it does
not include a comma
(\(oq\&,\(cq).
.PP
For example:
.nf
.sp
.RS 6n
Debug sudo /var/log/sudo_debug all@warn,plugin@info
.RE
.fi
.PP
would log all debugging statements at the
\fIwarn\fR
level and higher in addition to those at the
\fIinfo\fR
level for the plugin subsystem.
.PP
As of
\fBsudo\fR
1.8.12, multiple
\fRDebug\fR
entries may be specified per program.
Older versions of
\fBsudo\fR
only support a single
\fRDebug\fR
entry per program.
Plugin-specific
\fRDebug\fR
entries are also supported starting with
\fBsudo\fR
1.8.12 and are matched by either the base name of the plugin that was loaded
(for example
\fRsudoers.so\fR)
or by the plugin's fully-qualified path name.
Previously, the
\fBsudoers\fR
plugin shared the same
\fRDebug\fR
entry as the
\fBsudo\fR
front end and could not be configured separately.
.PP
The following priorities are supported, in order of decreasing severity:
\fIcrit\fR, \fIerr\fR, \fIwarn\fR, \fInotice\fR, \fIdiag\fR, \fIinfo\fR, \fItrace\fR
and
\fIdebug\fR.
Each priority, when specified, also includes all priorities higher
than it.
For example, a priority of
\fInotice\fR
would include debug messages logged at
\fInotice\fR
and higher.
.PP
The priorities
\fItrace\fR
and
\fIdebug\fR
also include function call tracing which logs when a function is
entered and when it returns.
For example, the following trace is for the
\fBget_user_groups\fR()
function located in src/sudo.c:
.nf
.sp
.RS 6n
sudo[123] -> get_user_groups @ src/sudo.c:385
sudo[123] <- get_user_groups @ src/sudo.c:429 := groups=10,0,5
.RE
.fi
.PP
When the function is entered, indicated by a right arrow
\(oq->\(cq,
the program, process ID, function, source file and line number
are logged.
When the function returns, indicated by a left arrow
\(oq<-\(cq,
the same information is logged along with the return value.
In this case, the return value is a string.
.PP
The following subsystems are used by the
\fBsudo\fR
front-end:
.TP 12n
\fIall\fR
matches every subsystem
.TP 12n
\fIargs\fR
command line argument processing
.TP 12n
\fIconv\fR
user conversation
.TP 12n
\fIedit\fR
sudoedit
.TP 12n
\fIevent\fR
event subsystem
.TP 12n
\fIexec\fR
command execution
.TP 12n
\fImain\fR
\fBsudo\fR
main function
.TP 12n
\fInetif\fR
network interface handling
.TP 12n
\fIpcomm\fR
communication with the plugin
.TP 12n
\fIplugin\fR
plugin configuration
.TP 12n
\fIpty\fR
pseudo-tty related code
.TP 12n
\fIselinux\fR
SELinux-specific handling
.TP 12n
\fIutil\fR
utility functions
.TP 12n
\fIutmp\fR
utmp handling
.PP
The
sudoers(@mansectform@)
plugin includes support for additional subsystems.
.SH "FILES"
.TP 26n
\fI@sysconfdir@/sudo.conf\fR
\fBsudo\fR
front end configuration
.SH "EXAMPLES"
.nf
.RS 0n
#
# Default @sysconfdir@/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 @PLUGINDIR@ 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 @noexec_file@

#
# 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
.RE
.fi
.SH "SEE ALSO"
sudo_plugin(@mansectform@),
sudoers(@mansectform@),
sudo(@mansectsu@)
.SH "HISTORY"
See the HISTORY file in the
\fBsudo\fR
distribution (https://www.sudo.ws/history.html) for a brief
history of sudo.
.SH "AUTHORS"
Many people have worked on
\fBsudo\fR
over the years; this version consists of code written primarily by:
.sp
.RS 6n
Todd C. Miller
.RE
.PP
See the CONTRIBUTORS file in the
\fBsudo\fR
distribution (https://www.sudo.ws/contributors.html) for an
exhaustive list of people who have contributed to
\fBsudo\fR.
.SH "BUGS"
If you feel you have found a bug in
\fBsudo\fR,
please submit a bug report at https://bugzilla.sudo.ws/
.SH "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.
.SH "DISCLAIMER"
\fBsudo\fR
is provided
\(lqAS IS\(rq
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
\fBsudo\fR
or https://www.sudo.ws/license.html for complete details.