src/daemon/caps.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of PulseAudio.
   5
   6   Copyright 2004-2006 Lennart Poettering
   7   Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
   8
   9   PulseAudio is free software; you can redistribute it and/or modify
  10   it under the terms of the GNU Lesser General Public License as published
  11   by the Free Software Foundation; either version 2 of the License,
  12   or (at your option) any later version.
  13
  14   PulseAudio is distributed in the hope that it will be useful, but
  15   WITHOUT ANY WARRANTY; without even the implied warranty of
  16   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17   General Public License for more details.
  18
  19   You should have received a copy of the GNU Lesser General Public License
  20   along with PulseAudio; if not, write to the Free Software
  21   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  22   USA.
  23 ***/
  24
  25 #ifdef HAVE_CONFIG_H
  26 #include <config.h>
  27 #endif
  28
  29 #include <unistd.h>
  30 #include <errno.h>
  31 #include <string.h>
  32 #include <sys/types.h>
  33 #include <pulsecore/macro.h>
  34
  35 #ifdef HAVE_SYS_CAPABILITY_H
  36 #include <sys/capability.h>
  37 #endif
  38 #ifdef HAVE_SYS_PRCTL_H
  39 #include <sys/prctl.h>
  40 #endif
  41
  42 #include <pulsecore/core-error.h>
  43
  44 #include <pulsecore/log.h>
  45
  46 #include "caps.h"
  47
  48 /* Glibc <= 2.2 has broken unistd.h */
  49 #if defined(linux) && (__GLIBC__ <= 2 && __GLIBC_MINOR__ <= 2)
  50 int setresgid(gid_t r, gid_t e, gid_t s);
  51 int setresuid(uid_t r, uid_t e, uid_t s);
  52 #endif
  53
  54 #ifdef HAVE_GETUID
  55
  56 /* Drop root rights when called SUID root */
  57 void pa_drop_root(void) {
  58     uid_t uid = getuid();
  59
  60     if (uid == 0 || geteuid() != 0)
  61         return;
  62
  63     pa_log_info("Dropping root priviliges.");
  64
  65 #if defined(HAVE_SETRESUID)
  66     setresuid(uid, uid, uid);
  67 #elif defined(HAVE_SETREUID)
  68     setreuid(uid, uid);
  69 #else
  70     setuid(uid);
  71     seteuid(uid);
  72 #endif
  73 }
  74
  75 #else
  76
  77 void pa_drop_root(void) {
  78 }
  79
  80 #endif
  81
  82 #if defined(HAVE_SYS_CAPABILITY_H) && defined(HAVE_SYS_PRCTL_H)
  83
  84 /* Limit permitted capabilities set to CAPSYS_NICE */
  85 int pa_limit_caps(void) {
  86     int r = -1;
  87     cap_t caps;
  88     cap_value_t nice_cap = CAP_SYS_NICE;
  89
  90     caps = cap_init();
  91     pa_assert(caps);
  92     cap_clear(caps);
  93     cap_set_flag(caps, CAP_EFFECTIVE, 1, &nice_cap, CAP_SET);
  94     cap_set_flag(caps, CAP_PERMITTED, 1, &nice_cap, CAP_SET);
  95
  96     if (cap_set_proc(caps) < 0)
  97         goto fail;
  98
  99     if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0)
 100         goto fail;
 101
 102     pa_log_info("Dropped capabilities successfully.");
 103
 104     r = 1;
 105
 106 fail:
 107     cap_free(caps);
 108
 109     return r;
 110 }
 111
 112 /* Drop all capabilities, effectively becoming a normal user */
 113 int pa_drop_caps(void) {
 114     cap_t caps;
 115     int r = -1;
 116
 117     caps = cap_init();
 118     pa_assert(caps);
 119
 120     cap_clear(caps);
 121
 122     prctl(PR_SET_KEEPCAPS, 0, 0, 0, 0);
 123
 124     if (cap_set_proc(caps) < 0) {
 125         pa_log("Failed to drop capabilities: %s", pa_cstrerror(errno));
 126         goto fail;
 127     }
 128
 129     r = 0;
 130
 131 fail:
 132     cap_free(caps);
 133
 134     return r;
 135 }
 136
 137 #else
 138
 139 /* NOOPs in case capabilities are not available. */
 140 int pa_limit_caps(void) {
 141     return 0;
 142 }
 143
 144 int pa_drop_caps(void) {
 145     pa_drop_root();
 146     return 0;
 147 }
 148
 149 #endif
 150