code.delx.au - pulseaudio/blob - src/daemon/caps.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2004-2006 Lennart Poettering
   5   Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
   6
   7   PulseAudio is free software; you can redistribute it and/or modify
   8   it under the terms of the GNU Lesser General Public License as published
   9   by the Free Software Foundation; either version 2 of the License,
  10   or (at your option) any later version.
  11
  12   PulseAudio is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with PulseAudio; if not, write to the Free Software
  19   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  20   USA.
  21 ***/
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 #include <unistd.h>
  28 #include <errno.h>
  29 #include <string.h>
  30 #include <sys/types.h>
  31 #include <pulsecore/macro.h>
  32
  33 #ifdef HAVE_SYS_CAPABILITY_H
  34 #include <sys/capability.h>
  35 #endif
  36 #ifdef HAVE_SYS_PRCTL_H
  37 #include <sys/prctl.h>
  38 #endif
  39
  40 #include <pulsecore/core-error.h>
  41
  42 #include <pulsecore/log.h>
  43
  44 #include "caps.h"
  45
  46 /* Glibc <= 2.2 has broken unistd.h */
  47 #if defined(linux) && (__GLIBC__ <= 2 && __GLIBC_MINOR__ <= 2)
  48 int setresgid(gid_t r, gid_t e, gid_t s);
  49 int setresuid(uid_t r, uid_t e, uid_t s);
  50 #endif
  51
  52 #ifdef HAVE_GETUID
  53
  54 /* Drop root rights when called SUID root */
  55 void pa_drop_root(void) {
  56     uid_t uid = getuid();
  57
  58     if (uid == 0 || geteuid() != 0)
  59         return;
  60
  61     pa_log_info("Dropping root priviliges.");
  62
  63 #if defined(HAVE_SETRESUID)
  64     pa_assert_se(setresuid(uid, uid, uid) >= 0);
  65 #elif defined(HAVE_SETREUID)
  66     pa_assert_se(setreuid(uid, uid) >= 0);
  67 #else
  68     pa_assert_se(setuid(uid) >= 0);
  69     pa_assert_se(seteuid(uid) >= 0);
  70 #endif
  71
  72     pa_assert_se(getuid() == uid);
  73     pa_assert_se(geteuid() == uid);
  74 }
  75
  76 #else
  77
  78 void pa_drop_root(void) {
  79 }
  80
  81 #endif
  82
  83 #if defined(HAVE_SYS_CAPABILITY_H) && defined(HAVE_SYS_PRCTL_H)
  84
  85 /* Limit permitted capabilities set to CAPSYS_NICE */
  86 void pa_limit_caps(void) {
  87     cap_t caps;
  88     cap_value_t nice_cap = CAP_SYS_NICE;
  89
  90     pa_assert_se(caps = cap_init());
  91     pa_assert_se(cap_clear(caps) == 0);
  92     pa_assert_se(cap_set_flag(caps, CAP_EFFECTIVE, 1, &nice_cap, CAP_SET) == 0);
  93     pa_assert_se(cap_set_flag(caps, CAP_PERMITTED, 1, &nice_cap, CAP_SET) == 0);
  94
  95     if (cap_set_proc(caps) < 0)
  96         /* Hmm, so we couldn't limit our caps, which probably means we
  97          * hadn't any in the first place, so let's just make sure of
  98          * that */
  99         pa_drop_caps();
 100     else
 101         pa_log_info("Limited capabilities successfully to CAP_SYS_NICE.");
 102
 103     pa_assert_se(cap_free(caps) == 0);
 104
 105     pa_assert_se(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == 0);
 106 }
 107
 108 /* Drop all capabilities, effectively becoming a normal user */
 109 void pa_drop_caps(void) {
 110     cap_t caps;
 111
 112     pa_assert_se(prctl(PR_SET_KEEPCAPS, 0, 0, 0, 0) == 0);
 113
 114     pa_assert_se(caps = cap_init());
 115     pa_assert_se(cap_clear(caps) == 0);
 116     pa_assert_se(cap_set_proc(caps) == 0);
 117     pa_assert_se(cap_free(caps) == 0);
 118
 119     pa_assert_se(!pa_have_caps());
 120 }
 121
 122 pa_bool_t pa_have_caps(void) {
 123     cap_t caps;
 124     cap_flag_value_t flag = CAP_CLEAR;
 125
 126     pa_assert_se(caps = cap_get_proc());
 127     pa_assert_se(cap_get_flag(caps, CAP_SYS_NICE, CAP_EFFECTIVE, &flag) >= 0);
 128     pa_assert_se(cap_free(caps) == 0);
 129
 130     return flag == CAP_SET;
 131 }
 132
 133 #else
 134
 135 /* NOOPs in case capabilities are not available. */
 136 void pa_limit_caps(void) {
 137 }
 138
 139 void pa_drop_caps(void) {
 140     pa_drop_root();
 141 }
 142
 143 pa_bool_t pa_have_caps(void) {
 144     return FALSE;
 145 }
 146
 147 #endif