Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
+ 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.
systemd 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
- General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU General Public License
+ You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <ctype.h>
#include <sys/capability.h>
#include <sys/prctl.h>
+#include "grp.h"
#include "macro.h"
-#include "capability.h"
#include "util.h"
#include "log.h"
+#include "fileio.h"
+#include "capability.h"
int have_effective_cap(int value) {
- cap_t cap;
+ _cleanup_cap_free_ cap_t cap;
cap_flag_value_t fv;
- int r;
- if (!(cap = cap_get_proc()))
+ cap = cap_get_proc();
+ if (!cap)
return -errno;
if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
- r = -errno;
+ return -errno;
else
- r = fv == CAP_SET;
-
- cap_free(cap);
- return r;
+ return fv == CAP_SET;
}
unsigned long cap_last_cap(void) {
- static __thread unsigned long saved;
- static __thread bool valid = false;
+ static thread_local unsigned long saved;
+ static thread_local bool valid = false;
unsigned long p;
if (valid)
return p;
}
+
+int capability_bounding_set_drop(uint64_t drop, bool right_now) {
+ unsigned long i;
+ _cleanup_cap_free_ cap_t after_cap = NULL, temp_cap = NULL;
+ cap_flag_value_t fv;
+ int r;
+
+ /* If we are run as PID 1 we will lack CAP_SETPCAP by default
+ * in the effective set (yes, the kernel drops that when
+ * executing init!), so get it back temporarily so that we can
+ * call PR_CAPBSET_DROP. */
+
+ after_cap = cap_get_proc();
+ if (!after_cap)
+ return -errno;
+
+ if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
+ return -errno;
+
+ if (fv != CAP_SET) {
+ static const cap_value_t v = CAP_SETPCAP;
+
+ temp_cap = cap_dup(after_cap);
+ if (!temp_cap) {
+ r = -errno;
+ goto finish;
+ }
+
+ if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
+ r = -errno;
+ goto finish;
+ }
+
+ if (cap_set_proc(temp_cap) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ }
+
+ for (i = 0; i <= cap_last_cap(); i++) {
+
+ if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
+ cap_value_t v;
+
+ /* Drop it from the bounding set */
+ if (prctl(PR_CAPBSET_DROP, i) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ v = (cap_value_t) i;
+
+ /* Also drop it from the inheritable set, so
+ * that anything we exec() loses the
+ * capability for good. */
+ if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
+ r = -errno;
+ goto finish;
+ }
+
+ /* If we shall apply this right now drop it
+ * also from our own capability sets. */
+ if (right_now) {
+ if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
+ cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ }
+ }
+ }
+
+ r = 0;
+
+finish:
+ if (cap_set_proc(after_cap) < 0)
+ return -errno;
+
+ return r;
+}
+
+static int drop_from_file(const char *fn, uint64_t drop) {
+ int r, k;
+ uint32_t hi, lo;
+ uint64_t current, after;
+ char *p;
+
+ r = read_one_line_file(fn, &p);
+ if (r < 0)
+ return r;
+
+ assert_cc(sizeof(hi) == sizeof(unsigned));
+ assert_cc(sizeof(lo) == sizeof(unsigned));
+
+ k = sscanf(p, "%u %u", &lo, &hi);
+ free(p);
+
+ if (k != 2)
+ return -EIO;
+
+ current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
+ after = current & ~drop;
+
+ if (current == after)
+ return 0;
+
+ lo = (unsigned) (after & 0xFFFFFFFFULL);
+ hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
+
+ if (asprintf(&p, "%u %u", lo, hi) < 0)
+ return -ENOMEM;
+
+ r = write_string_file(fn, p);
+ free(p);
+
+ return r;
+}
+
+int capability_bounding_set_drop_usermode(uint64_t drop) {
+ int r;
+
+ r = drop_from_file("/proc/sys/kernel/usermodehelper/inheritable", drop);
+ if (r < 0)
+ return r;
+
+ r = drop_from_file("/proc/sys/kernel/usermodehelper/bset", drop);
+ if (r < 0)
+ return r;
+
+ return r;
+}
+
+int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilites) {
+
+ _cleanup_cap_free_ cap_t d = NULL;
+ cap_value_t bits[sizeof(keep_capabilites)*8];
+ unsigned i, j = 0;
+ int r;
+
+ /* Unfortunately we cannot leave privilege dropping to PID 1
+ * here, since we want to run as user but want to keep some
+ * capabilities. Since file capabilities have been introduced
+ * this cannot be done across exec() anymore, unless our
+ * binary has the capability configured in the file system,
+ * which we want to avoid. */
+
+ if (setresgid(gid, gid, gid) < 0) {
+ log_error("Failed change group ID: %m");
+ return -errno;
+ }
+
+ if (setgroups(0, NULL) < 0) {
+ log_error("Failed to drop auxiliary groups list: %m");
+ return -errno;
+ }
+
+ if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
+ log_error("Failed to enable keep capabilities flag: %m");
+ return -errno;
+ }
+
+ r = setresuid(uid, uid, uid);
+ if (r < 0) {
+ log_error("Failed change user ID: %m");
+ return -errno;
+ }
+
+ if (prctl(PR_SET_KEEPCAPS, 0) < 0) {
+ log_error("Failed to disable keep capabilities flag: %m");
+ return -errno;
+ }
+
+ r = capability_bounding_set_drop(~keep_capabilites, true);
+ if (r < 0) {
+ log_error("Failed to drop capabilities: %s", strerror(-r));
+ return r;
+ }
+
+ d = cap_init();
+ if (!d)
+ return log_oom();
+
+ for (i = 0; i < sizeof(keep_capabilites)*8; i++)
+ if (keep_capabilites & (1ULL << i))
+ bits[j++] = i;
+
+ if (cap_set_flag(d, CAP_EFFECTIVE, j, bits, CAP_SET) < 0 ||
+ cap_set_flag(d, CAP_PERMITTED, j, bits, CAP_SET) < 0) {
+ log_error("Failed to enable capabilities bits: %m");
+ return -errno;
+ }
+
+ if (cap_set_proc(d) < 0) {
+ log_error("Failed to increase capabilities: %m");
+ return -errno;
+ }
+
+ return 0;
+}
~ianmdlvl / elogind.git / blobdiff