конфигурация для внешнего интерфейса sudo (configuration for sudo front end)
Описание (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 approval_plugin,
audit_plugin, io_plugin, or policy_plugin struct contained in the
plugin. If a plugin implements multiple plugin types, there must
be a Plugin line for each unique symbol name. 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, for
I/O logging (if enabled by the policy) and for auditing. This is
equivalent to the following:
Plugin sudoers_policy sudoers.so
Plugin sudoers_io sudoers.so
Plugin sudoers_audit sudoers.so
Starting with sudo version 1.9.1, some of the logging functionality
of the sudoers plugin has been moved from the policy plugin to an
audit plugin. To maintain compatibility with sudo.conf files from
older sudo versions, if sudoers is configured as the security
policy, it will be used as an audit plugin as well. This
guarantees that the logging behavior will be consistnet with that
of sudo versions 1.9.0 and below.
For more information on the sudo plugin architecture, see the
sudo_plugin(5) 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 intercept /usr/local/libexec/sudo/sudo_intercept.so
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:
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.
devsearch
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 not
recurse into sub-directories. If terminal devices may be
located in a sub-directory of /dev, that path must be
explicitly listed in devsearch. The default value is
/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.
intercept
The fully-qualified path to a shared library containing a
wrapper for the execve() system call that intercepts
attempts to run further commands and performs a policy
check before allowing them to be executed. This is used
to implement the intercept functionality on systems that
support LD_PRELOAD or its equivalent. The default value
is /usr/local/libexec/sudo/sudo_intercept.so.
noexec The fully-qualified path to a shared library containing
wrappers for the execl(), execle(), execlp(), exect(),
execv(), execve(), execveat(), 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.
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/local/libexec/sudo.
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 set-user-ID 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 set-user-ID 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.
developer_mode
By default sudo refuses to load plugins which can be
modified by other than the root user. The plugin should
be owned by root and write access permissions should be
disabled for 'group' and 'other'. To make development of
a plugin easier, you can disable that by setting
'developer_mode' option to true in sudo.conf as follows:
Set developer_mode true
Please note that this creates a security risk, so it is
not recommended on critical systems such as a desktop
machine for daily use, but is intended to be used in
development environments (VM, container, etc). Before
enabling developer mode, ensure you understand the
implications.
This setting is only available in sudo version 1.9.0 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, macOS and Solaris. This is the
default behavior on macOS in sudo 1.9.6 and
higher.
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 on systems other than macOS 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 or larger than 1024
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.
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.
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 settings
sudo versions 1.8.4 and higher support a flexible debugging
framework that can log 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, plugin or shared object to debug, the debug file name
and a comma-separated list of debug flags. The debug flag syntax
used by sudo, the sudoers plugin and its associated programs and
shared objects is subsystem@priority but a third-party plugin is
free to use a different format so long as it does not include a
comma (',').
Examples:
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.
Debug sudo_intercept.so /var/log/intercept_debug all@debug
would log all debugging statements, regardless of level, for the
sudo_intercept.so shared object that implements sudo's intercept
functionality.
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-terminal related code
selinux SELinux-specific handling
util utility functions
utmp utmp handling
The sudoers(5) plugin includes support for additional subsystems.
