chiark / gitweb /
kdbus: update kdbus.h from upstream
[elogind.git] / src / shared / capability.c
1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
2
3 /***
4   This file is part of systemd.
5
6   Copyright 2010 Lennart Poettering
7
8   systemd is free software; you can redistribute it and/or modify it
9   under the terms of the GNU Lesser General Public License as published by
10   the Free Software Foundation; either version 2.1 of the License, or
11   (at your option) any later version.
12
13   systemd is distributed in the hope that it will be useful, but
14   WITHOUT ANY WARRANTY; without even the implied warranty of
15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16   Lesser General Public License for more details.
17
18   You should have received a copy of the GNU Lesser General Public License
19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
20 ***/
21
22 #include <assert.h>
23 #include <string.h>
24 #include <unistd.h>
25 #include <errno.h>
26 #include <stdio.h>
27 #include <sys/types.h>
28 #include <stdarg.h>
29 #include <ctype.h>
30 #include <sys/capability.h>
31 #include <sys/prctl.h>
32
33 #include "macro.h"
34 #include "capability.h"
35 #include "util.h"
36 #include "log.h"
37 #include "fileio.h"
38
39 int have_effective_cap(int value) {
40         cap_t cap;
41         cap_flag_value_t fv;
42         int r;
43
44         cap = cap_get_proc();
45         if (!cap)
46                 return -errno;
47
48         if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
49                 r = -errno;
50         else
51                 r = fv == CAP_SET;
52
53         cap_free(cap);
54         return r;
55 }
56
57 unsigned long cap_last_cap(void) {
58         static __thread unsigned long saved;
59         static __thread bool valid = false;
60         unsigned long p;
61
62         if (valid)
63                 return saved;
64
65         p = (unsigned long) CAP_LAST_CAP;
66
67         if (prctl(PR_CAPBSET_READ, p) < 0) {
68
69                 /* Hmm, look downwards, until we find one that
70                  * works */
71                 for (p--; p > 0; p --)
72                         if (prctl(PR_CAPBSET_READ, p) >= 0)
73                                 break;
74
75         } else {
76
77                 /* Hmm, look upwards, until we find one that doesn't
78                  * work */
79                 for (;; p++)
80                         if (prctl(PR_CAPBSET_READ, p+1) < 0)
81                                 break;
82         }
83
84         saved = p;
85         valid = true;
86
87         return p;
88 }
89
90 int capability_bounding_set_drop(uint64_t drop, bool right_now) {
91         unsigned long i;
92         cap_t after_cap = NULL, temp_cap = NULL;
93         cap_flag_value_t fv;
94         int r;
95
96         /* If we are run as PID 1 we will lack CAP_SETPCAP by default
97          * in the effective set (yes, the kernel drops that when
98          * executing init!), so get it back temporarily so that we can
99          * call PR_CAPBSET_DROP. */
100
101         after_cap = cap_get_proc();
102         if (!after_cap)
103                 return -errno;
104
105         if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0) {
106                 cap_free(after_cap);
107                 return -errno;
108         }
109
110         if (fv != CAP_SET) {
111                 static const cap_value_t v = CAP_SETPCAP;
112
113                 temp_cap = cap_dup(after_cap);
114                 if (!temp_cap) {
115                         r = -errno;
116                         goto finish;
117                 }
118
119                 if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
120                         r = -errno;
121                         goto finish;
122                 }
123
124                 if (cap_set_proc(temp_cap) < 0) {
125                         r = -errno;
126                         goto finish;
127                 }
128         }
129
130         for (i = 0; i <= cap_last_cap(); i++) {
131
132                 if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
133                         cap_value_t v;
134
135                         /* Drop it from the bounding set */
136                         if (prctl(PR_CAPBSET_DROP, i) < 0) {
137                                 r = -errno;
138                                 goto finish;
139                         }
140                         v = i;
141
142                         /* Also drop it from the inheritable set, so
143                          * that anything we exec() loses the
144                          * capability for good. */
145                         if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
146                                 r = -errno;
147                                 goto finish;
148                         }
149
150                         /* If we shall apply this right now drop it
151                          * also from our own capability sets. */
152                         if (right_now) {
153                                 if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
154                                     cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
155                                         r = -errno;
156                                         goto finish;
157                                 }
158                         }
159                 }
160         }
161
162         r = 0;
163
164 finish:
165         if (temp_cap)
166                 cap_free(temp_cap);
167
168         if (after_cap) {
169                 cap_set_proc(after_cap);
170                 cap_free(after_cap);
171         }
172
173         return r;
174 }
175
176 static int drop_from_file(const char *fn, uint64_t drop) {
177         int r, k;
178         uint32_t hi, lo;
179         uint64_t current, after;
180         char *p;
181
182         r = read_one_line_file(fn, &p);
183         if (r < 0)
184                 return r;
185
186         assert_cc(sizeof(hi) == sizeof(unsigned));
187         assert_cc(sizeof(lo) == sizeof(unsigned));
188
189         k = sscanf(p, "%u %u", &lo, &hi);
190         free(p);
191
192         if (k != 2)
193                 return -EIO;
194
195         current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
196         after = current & ~drop;
197
198         if (current == after)
199                 return 0;
200
201         lo = (unsigned) (after & 0xFFFFFFFFULL);
202         hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
203
204         if (asprintf(&p, "%u %u", lo, hi) < 0)
205                 return -ENOMEM;
206
207         r = write_string_file(fn, p);
208         free(p);
209
210         return r;
211 }
212
213 int capability_bounding_set_drop_usermode(uint64_t drop) {
214         int r;
215
216         r = drop_from_file("/proc/sys/kernel/usermodehelper/inheritable", drop);
217         if (r < 0)
218                 return r;
219
220         r = drop_from_file("/proc/sys/kernel/usermodehelper/bset", drop);
221         if (r < 0)
222                 return r;
223
224         return r;
225 }