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/***
This file is part of avahi.
avahi is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
avahi is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with avahi; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <avahi-core/log.h>
#include "caps.h"
int avahi_caps_reduce(void) {
int ret = 0;
cap_t caps;
static cap_value_t cap_values[] = { CAP_SYS_CHROOT, CAP_SETUID, CAP_SETGID };
/* Let's reduce our caps to the minimum set and tell Linux to keep
* them across setuid(). This is called before we drop
* privileges. */
caps = cap_init();
assert(caps);
cap_clear(caps);
cap_set_flag(caps, CAP_EFFECTIVE, 3, cap_values, CAP_SET);
cap_set_flag(caps, CAP_PERMITTED, 3, cap_values, CAP_SET);
if (cap_set_proc(caps) < 0) {
avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
ret = -1;
}
cap_free(caps);
/* Retain capabilities across setuid() */
if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0) {
avahi_log_error("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
ret = -1;
}
return ret;
}
int avahi_caps_reduce2(void) {
int ret = 0;
cap_t caps;
static cap_value_t cap_values[] = { CAP_SYS_CHROOT };
/* Reduce our caps to the bare minimum and tell Linux not to keep
* them across setuid(). This is called after we drop
* privileges. */
/* No longer retain caps across setuid() */
if (prctl(PR_SET_KEEPCAPS, 0, 0, 0, 0) < 0) {
avahi_log_error("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
ret = -1;
}
caps = cap_init();
assert(caps);
cap_clear(caps);
/* setuid() zeroed our effective caps, let's get them back */
cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_values, CAP_SET);
cap_set_flag(caps, CAP_PERMITTED, 1, cap_values, CAP_SET);
if (cap_set_proc(caps) < 0) {
avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
ret = -1;
}
cap_free(caps);
return ret;
}
int avahi_caps_drop_all(void) {
cap_t caps;
int ret = 0;
/* Drop all capabilities and turn ourselves into a normal user process */
caps = cap_init();
assert(caps);
cap_clear(caps);
if (cap_set_proc(caps) < 0) {
avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
ret = -1;
}
cap_free(caps);
return ret;
}
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