summaryrefslogtreecommitdiffstats
path: root/avahi-daemon/caps.c
blob: 2d0f39a0342614568f7308b4fe9a9930f8a87c6f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
/* $Id$ */

/***
  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 <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 accross setuid(). This is called before we droppped
     * priviliges. */
    
    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 accros 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 dropped
     * privilige. */
    
    /* 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;
}