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/>.
27 #include <sys/types.h>
30 #include <sys/capability.h>
31 #include <sys/prctl.h>
34 #include "capability.h"
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)
53 unsigned long cap_last_cap(void) {
54 static thread_local unsigned long saved;
55 static thread_local bool valid = false;
61 p = (unsigned long) CAP_LAST_CAP;
63 if (prctl(PR_CAPBSET_READ, p) < 0) {
65 /* Hmm, look downwards, until we find one that
67 for (p--; p > 0; p --)
68 if (prctl(PR_CAPBSET_READ, p) >= 0)
73 /* Hmm, look upwards, until we find one that doesn't
76 if (prctl(PR_CAPBSET_READ, p+1) < 0)
86 int capability_bounding_set_drop(uint64_t drop, bool right_now) {
88 _cleanup_cap_free_ cap_t after_cap = NULL, temp_cap = NULL;
92 /* If we are run as PID 1 we will lack CAP_SETPCAP by default
93 * in the effective set (yes, the kernel drops that when
94 * executing init!), so get it back temporarily so that we can
95 * call PR_CAPBSET_DROP. */
97 after_cap = cap_get_proc();
101 if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
105 static const cap_value_t v = CAP_SETPCAP;
107 temp_cap = cap_dup(after_cap);
113 if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
118 if (cap_set_proc(temp_cap) < 0) {
124 for (i = 0; i <= cap_last_cap(); i++) {
126 if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
129 /* Drop it from the bounding set */
130 if (prctl(PR_CAPBSET_DROP, i) < 0) {
136 /* Also drop it from the inheritable set, so
137 * that anything we exec() loses the
138 * capability for good. */
139 if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
144 /* If we shall apply this right now drop it
145 * also from our own capability sets. */
147 if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
148 cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
159 cap_set_proc(after_cap);
164 static int drop_from_file(const char *fn, uint64_t drop) {
167 uint64_t current, after;
170 r = read_one_line_file(fn, &p);
174 assert_cc(sizeof(hi) == sizeof(unsigned));
175 assert_cc(sizeof(lo) == sizeof(unsigned));
177 k = sscanf(p, "%u %u", &lo, &hi);
183 current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
184 after = current & ~drop;
186 if (current == after)
189 lo = (unsigned) (after & 0xFFFFFFFFULL);
190 hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
192 if (asprintf(&p, "%u %u", lo, hi) < 0)
195 r = write_string_file(fn, p);
201 int capability_bounding_set_drop_usermode(uint64_t drop) {
204 r = drop_from_file("/proc/sys/kernel/usermodehelper/inheritable", drop);
208 r = drop_from_file("/proc/sys/kernel/usermodehelper/bset", drop);