1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Copyright 2010 Lennart Poettering
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.
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.
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/>.
26 #include <sys/capability.h>
27 #include <sys/prctl.h>
30 #include "alloc-util.h"
31 #include "capability-util.h"
35 #include "parse-util.h"
38 #if 0 /// UNNEEDED by elogind
39 int have_effective_cap(int value) {
40 _cleanup_cap_free_ cap_t cap;
47 if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
54 unsigned long cap_last_cap(void) {
55 static thread_local unsigned long saved;
56 static thread_local bool valid = false;
57 _cleanup_free_ char *content = NULL;
64 /* available since linux-3.2 */
65 r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
67 r = safe_atolu(content, &p);
75 /* fall back to syscall-probing for pre linux-3.2 */
76 p = (unsigned long) CAP_LAST_CAP;
78 if (prctl(PR_CAPBSET_READ, p) < 0) {
80 /* Hmm, look downwards, until we find one that
82 for (p--; p > 0; p --)
83 if (prctl(PR_CAPBSET_READ, p) >= 0)
88 /* Hmm, look upwards, until we find one that doesn't
91 if (prctl(PR_CAPBSET_READ, p+1) < 0)
101 #if 0 /// UNNEEDED by elogind
102 int capability_bounding_set_drop(uint64_t drop, bool right_now) {
103 _cleanup_cap_free_ cap_t after_cap = NULL;
108 /* If we are run as PID 1 we will lack CAP_SETPCAP by default
109 * in the effective set (yes, the kernel drops that when
110 * executing init!), so get it back temporarily so that we can
111 * call PR_CAPBSET_DROP. */
113 after_cap = cap_get_proc();
117 if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
121 _cleanup_cap_free_ cap_t temp_cap = NULL;
122 static const cap_value_t v = CAP_SETPCAP;
124 temp_cap = cap_dup(after_cap);
130 if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
135 if (cap_set_proc(temp_cap) < 0) {
141 for (i = 0; i <= cap_last_cap(); i++) {
143 if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
146 /* Drop it from the bounding set */
147 if (prctl(PR_CAPBSET_DROP, i) < 0) {
153 /* Also drop it from the inheritable set, so
154 * that anything we exec() loses the
155 * capability for good. */
156 if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
161 /* If we shall apply this right now drop it
162 * also from our own capability sets. */
164 if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
165 cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
176 if (cap_set_proc(after_cap) < 0)
182 static int drop_from_file(const char *fn, uint64_t drop) {
185 uint64_t current, after;
188 r = read_one_line_file(fn, &p);
192 assert_cc(sizeof(hi) == sizeof(unsigned));
193 assert_cc(sizeof(lo) == sizeof(unsigned));
195 k = sscanf(p, "%u %u", &lo, &hi);
201 current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
202 after = current & ~drop;
204 if (current == after)
207 lo = (unsigned) (after & 0xFFFFFFFFULL);
208 hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
210 if (asprintf(&p, "%u %u", lo, hi) < 0)
213 r = write_string_file(fn, p, WRITE_STRING_FILE_CREATE);
219 int capability_bounding_set_drop_usermode(uint64_t drop) {
222 r = drop_from_file("/proc/sys/kernel/usermodehelper/inheritable", drop);
226 r = drop_from_file("/proc/sys/kernel/usermodehelper/bset", drop);
233 int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) {
234 _cleanup_cap_free_ cap_t d = NULL;
238 /* Unfortunately we cannot leave privilege dropping to PID 1
239 * here, since we want to run as user but want to keep some
240 * capabilities. Since file capabilities have been introduced
241 * this cannot be done across exec() anymore, unless our
242 * binary has the capability configured in the file system,
243 * which we want to avoid. */
245 if (setresgid(gid, gid, gid) < 0)
246 return log_error_errno(errno, "Failed to change group ID: %m");
248 if (setgroups(0, NULL) < 0)
249 return log_error_errno(errno, "Failed to drop auxiliary groups list: %m");
251 /* Ensure we keep the permitted caps across the setresuid() */
252 if (prctl(PR_SET_KEEPCAPS, 1) < 0)
253 return log_error_errno(errno, "Failed to enable keep capabilities flag: %m");
255 r = setresuid(uid, uid, uid);
257 return log_error_errno(errno, "Failed to change user ID: %m");
259 if (prctl(PR_SET_KEEPCAPS, 0) < 0)
260 return log_error_errno(errno, "Failed to disable keep capabilities flag: %m");
262 /* Drop all caps from the bounding set, except the ones we want */
263 r = capability_bounding_set_drop(~keep_capabilities, true);
265 return log_error_errno(r, "Failed to drop capabilities: %m");
267 /* Now upgrade the permitted caps we still kept to effective caps */
272 if (keep_capabilities) {
273 cap_value_t bits[u64log2(keep_capabilities) + 1];
275 for (i = 0; i < ELEMENTSOF(bits); i++)
276 if (keep_capabilities & (1ULL << i))
279 /* use enough bits */
280 assert(i == 64 || (keep_capabilities >> i) == 0);
281 /* don't use too many bits */
282 assert(keep_capabilities & (1ULL << (i - 1)));
284 if (cap_set_flag(d, CAP_EFFECTIVE, j, bits, CAP_SET) < 0 ||
285 cap_set_flag(d, CAP_PERMITTED, j, bits, CAP_SET) < 0)
286 return log_error_errno(errno, "Failed to enable capabilities bits: %m");
288 if (cap_set_proc(d) < 0)
289 return log_error_errno(errno, "Failed to increase capabilities: %m");
295 int drop_capability(cap_value_t cv) {
296 _cleanup_cap_free_ cap_t tmp_cap = NULL;
298 tmp_cap = cap_get_proc();
302 if ((cap_set_flag(tmp_cap, CAP_INHERITABLE, 1, &cv, CAP_CLEAR) < 0) ||
303 (cap_set_flag(tmp_cap, CAP_PERMITTED, 1, &cv, CAP_CLEAR) < 0) ||
304 (cap_set_flag(tmp_cap, CAP_EFFECTIVE, 1, &cv, CAP_CLEAR) < 0))
307 if (cap_set_proc(tmp_cap) < 0)