| SUDOERS_TIMESTAMP(5) | File Formats and Configurations | SUDOERS_TIMESTAMP(5) |
sudoers_timestamp —
Sudoers Time Stamp Format
The sudoers plugin uses per-user-ID time
stamp files for credential caching. Once a user has been authenticated, they
may use sudo without a password for a short period
of time (5
minutes unless overridden by the timestamp_timeout
option). By default, sudoers uses a separate record
for each terminal, which means that a user's login sessions are
authenticated separately. The
timestamp_type
option can be used to select the type of time stamp record
sudoers will use.
A multi-record time stamp file format was introduced in
sudo 1.8.10 that uses a single file per user.
Previously, a separate file was used for each user and terminal combination
unless tty-based time stamps were disabled. The new format is extensible and
records of multiple types and versions may coexist within the same file.
All records, regardless of type or version, begin with a 16-bit version number and a 16-bit record size.
Time stamp records have the following structure:
/* Time stamp entry types */
#define TS_GLOBAL 0x01U /* not restricted by tty or ppid */
#define TS_TTY 0x02U /* restricted by tty */
#define TS_PPID 0x03U /* restricted by ppid */
#define TS_LOCKEXCL 0x04U /* special lock record */
/* Time stamp flags */
#define TS_DISABLED 0x01U /* entry disabled */
#define TS_ANYUID 0x02U /* ignore uid, only valid in key */
struct timestamp_entry {
unsigned short version; /* version number */
unsigned short size; /* entry size */
unsigned short type; /* TS_GLOBAL, TS_TTY, TS_PPID */
unsigned short flags; /* TS_DISABLED, TS_ANYUID */
uid_t auth_uid; /* uid to authenticate as */
pid_t sid; /* session ID associated with tty/ppid */
struct timespec start_time; /* session/ppid start time */
struct timespec ts; /* time stamp (CLOCK_MONOTONIC) */
union {
dev_t ttydev; /* tty device number */
pid_t ppid; /* parent pid */
} u;
};
The timestamp_entry struct fields are as follows:
TS_GLOBAL,
TS_TTY, or TS_PPID.TS_DISABLED, for records disabled via
sudo -k and
TS_ANYUID, which is used only when matching
records.TS_TTY.TS_TTY or of the parent process for records of
type TS_PPID. The start_time is
used to help prevent reuse of a time stamp record after a user has logged
out. Not all systems support a method to easily retrieve a process's start
time. The start_time field was added in
sudoers version 1.8.22 for the second revision of
the timestamp_entry struct.sudoers uses a monotonic timer that increments
even while the system is suspended. The value of ts is
updated each time a command is run via sudo. If
the difference between ts and the current time is less
than the value of the timestamp_timeout option, no
password is required.TS_TTY.TS_PPID.The tsdump utility, included
with the sudo source distribution, can be used to display the contents of a
sudoers time
stamp file.
In sudoers versions 1.8.10 through 1.8.14,
the entire time stamp file was locked for exclusive access when reading or
writing to the file. Starting in sudoers 1.8.15,
individual records are locked in the time stamp file instead of the entire
file and the lock is held for a longer period of time. This scheme is
described below.
The first record in the time stamp file is of type
TS_LOCKEXCL and is used as a
lock record to
prevent more than one sudo process from adding a new
record at the same time. Once the desired time stamp record has been located
or created (and locked), the TS_LOCKEXCL record is
unlocked. The lock on the individual time stamp record, however, is held
until authentication is complete. This allows
sudoers to avoid prompting for a password multiple
times when it is used more than once in a pipeline.
Records of type TS_GLOBAL cannot be locked
for a long period of time since doing so would interfere with other
sudo processes. Instead, a separate lock record is
used to prevent multiple sudo processes using the
same terminal (or parent process ID) from prompting for a password as the
same time.
Originally, sudo used a single zero-length
file per user and the file's modification time was used as the time stamp.
Later versions of sudo added restrictions on the
ownership of the time stamp files and directory as well as checks on the
validity of the time stamp itself. Notable changes were introduced in the
following sudo versions:
Support was added for the kernel-based tty time stamps available in OpenBSD which do not use an on-disk time stamp file.
Many people have worked on sudo over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS.md file in the sudo
distribution (https://www.sudo.ws/about/contributors/) for an exhaustive
list of people who have contributed to sudo.
If you believe you have found a bug in
sudoers_timestamp, you can either file a bug report
in the sudo bug database, https://bugzilla.sudo.ws/, or open an issue at
https://github.com/sudo-project/sudo/issues. If you would prefer to use
email, messages may be sent to the sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public) or
<sudo@sudo.ws> (private).
Please do not report security vulnerabilities through public GitHub issues, Bugzilla or mailing lists. Instead, report them via email to <Todd.Miller@sudo.ws>. You may encrypt your message with PGP if you would like, using the key found at https://www.sudo.ws/dist/PGPKEYS.
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.
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.md file distributed with
sudo or https://www.sudo.ws/about/license/ for
complete details.
| November 26, 2023 | Sudo 1.9.17p1 |