sys-utils/setpriv.1

   1 .TH SETPRIV 1 "July 2014" "util-linux" "User Commands"
   2 .SH NAME
   3 setpriv \- run a program with different Linux privilege settings
   4 .SH SYNOPSIS
   5 .B setpriv
   6 [options]
   7 .I program
   8 .RI [ arguments ]
   9 .SH DESCRIPTION
  10 Sets or queries various Linux privilege settings that are inherited across
  11 .BR execve (2).
  12 .PP
  13 In comparison to
  14 .BR su (1)
  15 and
  16 .BR runuser (1),
  17 .BR setpriv (1)
  18 neither uses PAM, nor does it prompt for a password.
  19 It is a simple, non-set-user-ID wrapper around
  20 .BR execve (2),
  21 and can be used to drop privileges in the same way as
  22 .BR setuidgid (8)
  23 from
  24 .BR daemontools ,
  25 .BR chpst (8)
  26 from
  27 .BR runit ,
  28 or similar tools shipped by other service managers.
  29 .SH OPTION
  30 .TP
  31 .B \-\-clear\-groups
  32 Clear supplementary groups.
  33 .TP
  34 .BR \-d , " \-\-dump"
  35 Dump current privilege state.  Can be specified more than once to show extra,
  36 mostly useless, information.  Incompatible with all other options.
  37 .TP
  38 .B \-\-groups \fIgroup\fR...
  39 Set supplementary groups.  The argument is a comma-separated list of GIDs or names.
  40 .TP
  41 .BR \-\-inh\-caps " (" + | \- ) \fIcap "...  or  " \-\-ambient-caps " (" + | \- ) \fIcap "...  or  " \-\-bounding\-set " (" + | \- ) \fIcap ...
  42 Set the inheritable capabilities, ambient capabilities or the capability bounding set.  See
  43 .BR capabilities (7).
  44 The argument is a comma-separated list of
  45 .BI + cap
  46 and
  47 .BI \- cap
  48 entries, which add or remove an entry respectively. \fIcap\fR can either be a
  49 human-readable name as seen in
  50 .BR capabilities (7)
  51 without the \fIcap_\fR prefix or of the format
  52 .BI cap_N ,
  53 where \fIN\fR is the internal capability index used by Linux.
  54 .B +all
  55 and
  56 .B \-all
  57 can be used to add or remove all caps.  The set of capabilities starts out as
  58 the current inheritable set for
  59 .BR \-\-inh\-caps ,
  60 the current ambient set for
  61 .B \-\-ambient\-caps
  62 and the current bounding set for
  63 .BR \-\-bounding\-set .
  64 If you drop something from the bounding set without also dropping it from the
  65 inheritable set, you are likely to become confused.  Do not do that.
  66 .TP
  67 .B \-\-keep\-groups
  68 Preserve supplementary groups.  Only useful in conjunction with
  69 .BR \-\-rgid ,
  70 .BR \-\-egid ", or"
  71 .BR \-\-regid .
  72 .TP
  73 .B \-\-init\-groups
  74 Initialize supplementary groups using
  75 .BR initgroups "(3)."
  76 Only useful in conjunction with
  77 .B \-\-ruid
  78 or
  79 .BR \-\-reuid .
  80 .TP
  81 .B \-\-list\-caps
  82 List all known capabilities.  This option must be specified alone.
  83 .TP
  84 .B \-\-no\-new\-privs
  85 Set the
  86 .I no_new_privs
  87 bit.  With this bit set,
  88 .BR execve (2)
  89 will not grant new privileges.
  90 For example, the set-user-ID and set-group-ID bits as well
  91 as file capabilities will be disabled.  (Executing binaries with these bits set
  92 will still work, but they will not gain privileges.  Certain LSMs, especially
  93 AppArmor, may result in failures to execute certain programs.)  This bit is
  94 inherited by child processes and cannot be unset.  See
  95 .BR prctl (2)
  96 and
  97 .I Documentation/\:prctl/\:no_\:new_\:privs.txt
  98 in the Linux kernel source.
  99 .sp
 100 The no_new_privs bit is supported since Linux 3.5.
 101 .TP
 102 .BI \-\-rgid " gid\fR, " \-\-egid " gid\fR, " \-\-regid " gid"
 103 Set the real, effective, or both GIDs.  The \fIgid\fR argument can be
 104 given as textual group name.
 105 .sp
 106 For safety, you must specify one of
 107 .BR \-\-clear\-groups ,
 108 .BR \-\-groups ,
 109 .BR \-\-keep\-groups ", or"
 110 .B \-\-init\-groups
 111 if you set any primary
 112 .IR gid .
 113 .TP
 114 .BI \-\-ruid " uid\fR, " \-\-euid " uid\fR, " \-\-reuid " uid"
 115 Set the real, effective, or both UIDs.  The \fIuid\fR argument can be
 116 given as textual login name.
 117 .sp
 118 Setting a
 119 .I uid
 120 or
 121 .I gid
 122 does not change capabilities, although the exec call at the end might change
 123 capabilities.  This means that, if you are root, you probably want to do
 124 something like:
 125 .sp
 126 .B "        setpriv \-\-reuid=1000 \-\-regid=1000 \-\-inh\-caps=\-all"
 127 .TP
 128 .BR \-\-securebits " (" + | \- ) \fIsecurebit ...
 129 Set or clear securebits.  The argument is a comma-separated list.
 130 The valid securebits are
 131 .IR noroot ,
 132 .IR noroot_locked ,
 133 .IR no_setuid_fixup ,
 134 .IR no_setuid_fixup_locked ,
 135 and
 136 .IR keep_caps_locked .
 137 .I keep_caps
 138 is cleared by
 139 .BR execve (2)
 140 and is therefore not allowed.
 141 .TP
 142 .BR "\-\-pdeathsig keep" | clear | <signal>
 143 Keep, clear or set the parent death signal.  Some LSMs, most notably SELinux and
 144 AppArmor, clear the signal when the process' credentials change.  Using
 145 \fB\-\-pdeathsig keep\fR will restore the parent death signal after changing
 146 credentials to remedy that situation.
 147 .TP
 148 .BI \-\-selinux\-label " label"
 149 Request a particular SELinux transition (using a transition on exec, not
 150 dyntrans).  This will fail and cause
 151 .BR setpriv (1)
 152 to abort if SELinux is not in use, and the transition may be ignored or cause
 153 .BR execve (2)
 154 to fail at SELinux's whim.  (In particular, this is unlikely to work in
 155 conjunction with
 156 .IR no_new_privs .)
 157 This is similar to
 158 .BR runcon (1).
 159 .TP
 160 .BI \-\-apparmor\-profile " profile"
 161 Request a particular AppArmor profile (using a transition on exec).  This will
 162 fail and cause
 163 .BR setpriv (1)
 164 to abort if AppArmor is not in use, and the transition may be ignored or cause
 165 .BR execve (2)
 166 to fail at AppArmor's whim.
 167 .TP
 168 .B \-\-reset\-env
 169 Clears all the environment variables except TERM; initializes the environment variables HOME, SHELL, USER, LOGNAME
 170 according to the user's passwd entry; sets PATH to \fI/usr/local/bin:/bin:/usr/bin\fR for a regual user and to
 171 \fI/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin\fR for root.
 172 .sp
 173 The environment variable PATH may be different on systems where /bin and /sbin
 174 are merged into /usr.  The environment variable SHELL defaults to \fI/bin/sh\fR if none is given in the user's
 175 passwd entry.
 176 .TP
 177 .BR \-V , " \-\-version"
 178 Display version information and exit.
 179 .TP
 180 .BR \-h , " \-\-help"
 181 Display help text and exit.
 182 .SH NOTES
 183 If applying any specified option fails,
 184 .I program
 185 will not be run and
 186 .B setpriv
 187 will return with exit code 127.
 188 .PP
 189 Be careful with this tool \-\- it may have unexpected security consequences.
 190 For example, setting no_new_privs and then execing a program that is
 191 SELinux\-confined (as this tool would do) may prevent the SELinux
 192 restrictions from taking effect.
 193 .SH EXAMPLE
 194 If you're looking for behaviour similar to
 195 .BR su (1)/ runuser "(1), or " sudo (8)
 196 (without the
 197 .B \-g
 198 option), try something like:
 199 .sp
 200 .B "    setpriv \-\-reuid=1000 \-\-regid=1000 \-\-init\-groups"
 201 .PP
 202 If you want to mimic daemontools'
 203 .BR setuid (8),
 204 try:
 205 .sp
 206 .B "    setpriv \-\-reuid=1000 \-\-regid=1000 \-\-clear\-groups"
 207 .SH SEE ALSO
 208 .BR runuser (1),
 209 .BR su (1),
 210 .BR prctl (2),
 211 .BR capabilities (7)
 212 .SH AUTHOR
 213 .MT luto@amacapital.net
 214 Andy Lutomirski
 215 .ME
 216 .SH AVAILABILITY
 217 The
 218 .B setpriv
 219 command is part of the util-linux package and is available from
 220 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 221 Linux Kernel Archive
 222 .UE .