//po4a: entry man manual
= setpriv(1)
:doctype: manpage
:man manual: User Commands
:man source: util-linux {release-version}
:page-layout: base
:command: setpriv

== NAME

setpriv - run a program with different Linux privilege settings

== SYNOPSIS

*setpriv* [options] _program_ [_arguments_]

== DESCRIPTION

Sets or queries various Linux privilege settings that are inherited across *execve*(2).

In comparison to *su*(1) and *runuser*(1), *setpriv* neither uses PAM, nor does it prompt for a password. It is a simple, non-set-user-ID wrapper around *execve*(2), and can be used to drop privileges in the same way as *setuidgid*(8) from *daemontools*, *chpst*(8) from *runit*, or similar tools shipped by other service managers.

== OPTIONS

*--clear-groups*::
Clear supplementary groups.

*-d*, *--dump*::
Dump the current privilege state. This option can be specified more than once to show extra, mostly useless, information. Incompatible with all other options.

*--groups* _group_...::
Set supplementary groups. The argument is a comma-separated list of GIDs or names.

*--inh-caps* (*+*|*-*)_cap_...::
*--ambient-caps* (*+*|*-*)_cap_...::
*--bounding-set* (*+*|*-*)_cap_...::
Set the inheritable capabilities, ambient capabilities or the capability bounding set. See *capabilities*(7). The argument is a comma-separated list of **+**__cap__ and **-**__cap__ entries, which add or remove an entry respectively. _cap_ can either be a human-readable name as seen in *capabilities*(7) without the _cap__ prefix or of the format *cap_N*, where _N_ is the internal capability index used by Linux. *+all* and *-all* can be used to add or remove all caps.
+
The set of capabilities starts out as the current inheritable set for *--inh-caps*, the current ambient set for *--ambient-caps* and the current bounding set for *--bounding-set*.
+
Note the following restrictions (detailed in *capabilities*(7)) regarding modifications to these capability sets:

* A capability can be added to the inheritable set only if it is currently present in the bounding set.
* A capability can be added to the ambient set only if it is currently present in both the permitted and inheritable sets.
* Notwithstanding the syntax offered by *setpriv*, the kernel does not permit capabilities to be added to the bounding set.

+
If you drop a capability from the bounding set without also dropping it from the inheritable set, you are likely to become confused. Do not do that.

*--keep-groups*::
Preserve supplementary groups. Only useful in conjunction with *--rgid*, *--egid*, or *--regid*.

*--init-groups*::
Initialize supplementary groups using initgroups3. Only useful in conjunction with *--ruid* or *--reuid*.

*--list-caps*::
List all known capabilities. This option must be specified alone.

*--nnp*, *--no-new-privs*::
Set the _no_new_privs_ bit. With this bit set, *execve*(2) will not grant new privileges. For example, the set-user-ID and set-group-ID bits as well as file capabilities will be disabled. (Executing binaries with these bits set will still work, but they will not gain privileges. Certain LSMs, especially AppArmor, may result in failures to execute certain programs.) This bit is inherited by child processes and cannot be unset. See *prctl*(2) and _Documentation/prctl/no_new_privs.txt_ in the Linux kernel source.
+
The _no_new_privs_ bit is supported since Linux 3.5.

*--rgid* _gid_, *--egid* _gid_, *--regid* _gid_::
Set the real, effective, or both GIDs. The _gid_ argument can be given as a textual group name.
+
For safety, you must specify one of *--clear-groups*, *--groups*, *--keep-groups*, or *--init-groups* if you set any primary _gid_.

*--ruid* _uid_, *--euid* _uid_, *--reuid* _uid_::
Set the real, effective, or both UIDs. The _uid_ argument can be given as a textual login name.
+
Setting a _uid_ or _gid_ does not change capabilities, although the exec call at the end might change capabilities. This means that, if you are root, you probably want to do something like:
+
*setpriv --reuid=1000 --regid=1000 --inh-caps=-all*

*--securebits* (**+**|*-*)__securebit__...::
Set or clear securebits. The argument is a comma-separated list. The valid securebits are _noroot_, _noroot_locked_, _no_setuid_fixup_, _no_setuid_fixup_locked_, and _keep_caps_locked_. _keep_caps_ is cleared by *execve*(2) and is therefore not allowed.

**--pdeathsig keep**|**clear**|*<signal>*::
Keep, clear or set the parent death signal. Some LSMs, most notably SELinux and AppArmor, clear the signal when the process' credentials change. Using *--pdeathsig keep* will restore the parent death signal after changing credentials to remedy that situation.

*--ptracer* _pid_|**any**|**none**::
When Yama's restricted ptrace mode is in effect (that is, when _/proc/sys/kernel/yama/ptrace_scope_ is set to 1), allow being traced via **ptrace**(2) by the process with the specified PID, or any process, or no process. See **PR_SET_PTRACER**(2const). (Note that this is not inherited by child processes, though it is preserved across **execve**(2).) This option has no effect when Yama is not enabled or is in a mode other than restricted ptrace.

*--selinux-label* _label_::
Request a particular SELinux transition (using a transition on exec, not dyntrans). This will fail and cause *setpriv* to abort if SELinux is not in use, and the transition may be ignored or cause *execve*(2) to fail at SELinux's whim. (In particular, this is unlikely to work in conjunction with _no_new_privs_.) This is similar to *runcon*(1).

*--apparmor-profile* _profile_::
Request a particular AppArmor profile (using a transition on exec). This will fail and cause *setpriv* to abort if AppArmor is not in use, and the transition may be ignored or cause *execve*(2) to fail at AppArmor's whim.

*--landlock-access* _access_::
Enable landlock restrictions for a specific set of system accesses.
To allow specific subgroups of accesses use *--landlock-rule*.
+
Block all filesystem access:
+
*setpriv --landlock-access fs*
+
Block all file deletions and directory creations:
+
*setpriv --landlock-access fs:remove-file,make-dir*
+
For a complete set of supported access categories use *setpriv --help*.
+
The generic placeholder "fs" is subject to change and may be extended in future versions
to support new access types.

*--landlock-rule* _rule_::

Allow one specific access from the categories blocked by *--landlock-access*.
+
The syntax is as follows:
+
*--landlock-rule $ruletype:$access:$rulearg*
+
For example grant file read access to everything under */boot*:
+
*--landlock-rule path-beneath:read-file:/boot*

*--seccomp-filter* _file_::

Load raw BPF seccomp filter code from a file.
+
Filters can for example be created with *enosys*.

*--reset-env*::
* clears all the environment variables except *TERM* environment variable
* initializes the environment variables *HOME*, *SHELL*, *USER*, *LOGNAME* according to the user's passwd entry
* the environment variable *SHELL* defaults to */bin/sh* if none is given in the user's passwd entry.
* resets *PATH* environment variable according to setting in _/etc/login.defs_ (*ENV_PATH*, *ENV_SUPATH* or *ENV_ROOTPATH* variables), or defaults to _/usr/local/bin:/bin:/usr/bin_ for a regular user and to _/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin_ for root.
+
The environment variable *PATH* may be different on systems where _/bin_ and _/sbin_ are merged into _/usr_.

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== NOTES

If applying any specified option fails, _program_ will not be run and *setpriv* will return with exit status 127.

Be careful with this tool -- it may have unexpected security consequences. For example, setting _no_new_privs_ and then execing a program that is SELinux-confined (as this tool would do) may prevent the SELinux restrictions from taking effect.

== EXAMPLES

Note that *setpriv* is not a 1:1 replacement for *su*(1), *runuser*(1), or *sudo*(8).
Unlike those tools, *setpriv* does not use PAM, does not prompt for a password,
and does not perform session or accounting setup. The examples below provide
a starting point for common privilege-dropping scenarios.

If you want to switch UIDs/GIDs similarly to *runuser*(1) (without *--login*), try:

*setpriv --reuid=1000 --regid=1000 --inh-caps=-all --init-groups*

To also reset the environment (as *sudo*(8) does by default), add *--reset-env*:

*setpriv --reuid=1000 --regid=1000 --inh-caps=-all --init-groups --reset-env*

For a more restrictive setup that also limits the bounding set and prevents gaining
new privileges (more restrictive than *runuser* or *sudo*):

*setpriv --reuid=1000 --regid=1000 --init-groups --inh-caps=-all --bounding-set=-all --no-new-privs --reset-env*

If you want to mimic daemontools' *setuid*(8), try:

*setpriv --reuid=1000 --regid=1000 --clear-groups*

== AUTHORS

mailto:luto@amacapital.net[Andy Lutomirski]

== SEE ALSO

*runuser*(1),
*su*(1),
*prctl*(2),
*capabilities*(7),
*landlock*(7)

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