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  4. setpriv(1)

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SETPRIV(1) User Commands SETPRIV(1)

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(1) 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.

OPTION

Clear supplementary groups.
Dump current privilege state. Can be specified more than once to show extra, mostly useless, information. Incompatible with all other options.
Set supplementary groups. The argument is a comma-separated list.
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. If you drop something from the bounding set without also dropping it from the inheritable set, you are likely to become confused. Do not do that.
Preserve supplementary groups. Only useful in conjunction with --rgid, --egid, or --regid.
Initialize supplementary groups using initgroups(3). Only useful in conjunction with --ruid or --reuid.
List all known capabilities. This option must be specified alone.
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.

Set the real, effective, or both GIDs. The gid argument can be given as textual group name.

For safety, you must specify one of --clear-groups, --groups, --keep-groups, or --init-groups if you set any primary gid.

Set the real, effective, or both UIDs. The uid argument can be given as 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

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.
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.
Request a particular SELinux transition (using a transition on exec, not dyntrans). This will fail and cause setpriv(1) 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).
Request a particular AppArmor profile (using a transition on exec). This will fail and cause setpriv(1) to abort if AppArmor is not in use, and the transition may be ignored or cause execve(2) to fail at AppArmor's whim.
Display version information and exit.
Display help text and exit.

NOTES

If applying any specified option fails, program will not be run and setpriv will return with exit code 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.

EXAMPLE

If you're looking for behaviour similar to su(1)/runuser(1), or sudo(8) (without the -g option), try something like:

setpriv --reuid=1000 --regid=1000 --init-groups

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

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

SEE ALSO

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

AUTHOR

Andy Lutomirski

AVAILABILITY

The setpriv command is part of the util-linux package and is available from Linux Kernel Archive.

July 2014 util-linux