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diff --git a/docs/sudoers_timestamp.mdoc.in b/docs/sudoers_timestamp.mdoc.in new file mode 100644 index 0000000..633cc75 --- /dev/null +++ b/docs/sudoers_timestamp.mdoc.in @@ -0,0 +1,290 @@ +.\" +.\" SPDX-License-Identifier: ISC +.\" +.\" Copyright (c) 2017-2020, 2022 Todd C. Miller <Todd.Miller@sudo.ws> +.\" +.\" Permission to use, copy, modify, and distribute this software for any +.\" purpose with or without fee is hereby granted, provided that the above +.\" copyright notice and this permission notice appear in all copies. +.\" +.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES +.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR +.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF +.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +.\" +.Dd September 13, 2022 +.Dt SUDOERS_TIMESTAMP @mansectform@ +.Os Sudo @PACKAGE_VERSION@ +.Sh NAME +.Nm sudoers_timestamp +.Nd Sudoers Time Stamp Format +.Sh DESCRIPTION +The +.Nm sudoers +plugin uses per-user time stamp files for credential caching. +Once a user has been authenticated, they may use +.Nm sudo +without a password for a short period of time +.Po +.Em @timeout@ +minutes unless overridden by the +.Em timestamp_timeout +option +.Pc . +By default, +.Nm sudoers +uses a separate record for each terminal, which means that +a user's login sessions are authenticated separately. +The +.Em timestamp_type +option can be used to select the type of time stamp record +.Nm sudoers +will use. +.Pp +A multi-record time stamp file format was introduced in +.Nm 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. +.Pp +All records, regardless of type or version, begin with a 16-bit version +number and a 16-bit record size. +.Pp +Time stamp records have the following structure: +.Bd -literal +/* Time stamp entry types */ +#define TS_GLOBAL 0x01 /* not restricted by tty or ppid */ +#define TS_TTY 0x02 /* restricted by tty */ +#define TS_PPID 0x03 /* restricted by ppid */ +#define TS_LOCKEXCL 0x04 /* special lock record */ + +/* Time stamp flags */ +#define TS_DISABLED 0x01 /* entry disabled */ +#define TS_ANYUID 0x02 /* 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; +}; +.Ed +.Pp +The timestamp_entry struct fields are as follows: +.Bl -tag -width 4n +.It version +The version number of the timestamp_entry struct. +New entries are created with a version number of 2. +Records with different version numbers may coexist in the +same file but are not inter-operable. +.It size +The size of the record in bytes. +.It type +The record type, currently +.Dv TS_GLOBAL , +.Dv TS_TTY , +or +.Dv TS_PPID . +.It flags +Zero or more record flags which can be bit-wise ORed together. +Supported flags are +.Dv TS_DISABLED , +for records disabled via +.Nm sudo +.Fl k +and +.Dv TS_ANYUID , +which is used only when matching records. +.It auth_uid +The user-ID that was used for authentication. +Depending on the value of the +.Em rootpw , +.Em runaspw +and +.Em targetpw +options, the user-ID may be that of the invoking user, the root user, +the default runas user or the target user. +.It sid +The ID of the user's terminal session, if present. +The session ID is only used when matching records of type +.Dv TS_TTY . +.It start_time +The start time of the session leader for records of type +.Dv TS_TTY +or of the parent process for records of type +.Dv TS_PPID . +The +.Em start_time +is used to help prevent re-use 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 +.Em start_time +field was added in +.Nm sudoers +version 1.8.22 for the second revision of the timestamp_entry struct. +.It ts +The actual time stamp. +A monotonic time source (which does not move backward) is used if the +system supports it. +Where possible, +.Nm sudoers +uses a monotonic timer that increments even while the system +is suspended. +The value of +.Em ts +is updated each time a command is run via +.Nm sudo . +If the difference between +.Em ts +and the current time is less than the value of the +.Em timestamp_timeout +option, no password is required. +.It u.ttydev +The device number of the terminal associated with the session for +records of type +.Dv TS_TTY . +.It u.ppid +The ID of the parent process for records of type +.Dv TS_PPID . +.El +.Sh LOCKING +In +.Nm 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 +.Nm 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. +.Pp +The first record in the time stamp file is of type +.Dv TS_LOCKEXCL +and is used as a +.Em lock +record to prevent more than one +.Nm 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 +.Dv TS_LOCKEXCL +record is unlocked. +The lock on the individual time stamp record, however, is held until +authentication is complete. +This allows +.Nm sudoers +to avoid prompting for a password multiple times when it +is used more than once in a pipeline. +.Pp +Records of type +.Dv TS_GLOBAL +cannot be locked for a long period of time since doing so would +interfere with other +.Nm sudo +processes. +Instead, a separate lock record is used to prevent multiple +.Nm sudo +processes using the same terminal (or parent process ID) from +prompting for a password as the same time. +.Sh SEE ALSO +.Xr sudoers @mansectform@ , +.Xr sudo @mansectsu@ +.Sh HISTORY +Originally, +.Nm sudo +used a single zero-length file per user and the file's modification +time was used as the time stamp. +Later versions of +.Nm 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 +.Nm sudo +versions: +.Bl -tag -width 4n +.It 1.4.0 +Support for tty-based time stamp file was added +by appending the terminal name to the time stamp file name. +.It 1.6.2 +The time stamp file was replaced by a per-user directory which +contained any tty-based time stamp files. +.It 1.6.3p2 +The target user name was added to the time stamp file name when the +.Em targetpw +option was set. +.It 1.7.3 +Information about the terminal device was stored in +tty-based time stamp files for validity checks. +This included the terminal device numbers, inode number and, on systems +where it was not updated when the device was written to, the inode change time. +This helped prevent re-use of the time stamp file after logout. +.It 1.8.6p7 +The terminal session ID was added to tty-based time stamp files to +prevent re-use of the time stamp by the same user in a different +terminal session. +It also helped prevent re-use of the time stamp file on systems where +the terminal device's inode change time was updated by writing. +.It 1.8.10 +A new, multi-record time stamp file format was introduced that uses a +single file per user. +The terminal device's change time was not included since most +systems now update the change time after a write is performed +as required by POSIX. +.It 1.8.15 +Individual records are locked in the time stamp file instead of the +entire file and the lock is held until authentication is complete. +.It 1.8.22 +The start time of the terminal session leader or parent process is +now stored in non-global time stamp records. +This prevents re-use of the time stamp file after logout in most cases. +.Pp +Support was added for the kernel-based tty time stamps available in +.Ox +which do not use an on-disk time stamp file. +.El +.Sh AUTHORS +Many people have worked on +.Nm sudo +over the years; this version consists of code written primarily by: +.Bd -ragged -offset indent +.An Todd C. Miller +.Ed +.Pp +See the CONTRIBUTORS.md file in the +.Nm sudo +distribution (https://www.sudo.ws/about/contributors/) for an +exhaustive list of people who have contributed to +.Nm sudo . +.Sh BUGS +If you believe you have found a bug in +.Nm sudo , +you can 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 +.Nm sudo +is provided +.Dq 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 +.Nm sudo +or https://www.sudo.ws/about/license/ for complete details. |