-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
-/***
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd 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.
-
- 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
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
-***/
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
-#include <grp.h>
#include <stdio.h>
#include <stdlib.h>
-#include <sys/capability.h>
#include <sys/prctl.h>
#include <unistd.h>
#include "alloc-util.h"
#include "capability-util.h"
+#include "cap-list.h"
#include "fileio.h"
#include "log.h"
#include "macro.h"
+#include "missing_prctl.h"
#include "parse-util.h"
+#include "user-util.h"
#include "util.h"
int have_effective_cap(int value) {
if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
return -errno;
- else
- return fv == CAP_SET;
+
+ return fv == CAP_SET;
}
-unsigned long cap_last_cap(void) {
- static thread_local unsigned long saved;
+unsigned cap_last_cap(void) {
+ static thread_local unsigned saved;
static thread_local bool valid = false;
_cleanup_free_ char *content = NULL;
unsigned long p = 0;
if (r >= 0) {
r = safe_atolu(content, &p);
if (r >= 0) {
+
+ if (p > 63) /* Safety for the future: if one day the kernel learns more than 64 caps,
+ * then we are in trouble (since we, as much userspace and kernel space
+ * store capability masks in uint64_t types). Let's hence protect
+ * ourselves against that and always cap at 63 for now. */
+ p = 63;
+
saved = p;
valid = true;
return p;
}
/* fall back to syscall-probing for pre linux-3.2 */
- p = (unsigned long) CAP_LAST_CAP;
+ p = MIN((unsigned long) CAP_LAST_CAP, 63U);
if (prctl(PR_CAPBSET_READ, p) < 0) {
- /* Hmm, look downwards, until we find one that
- * works */
- for (p--; p > 0; p --)
+ /* Hmm, look downwards, until we find one that works */
+ for (p--; p > 0; p--)
if (prctl(PR_CAPBSET_READ, p) >= 0)
break;
} else {
- /* Hmm, look upwards, until we find one that doesn't
- * work */
- for (;; p++)
+ /* Hmm, look upwards, until we find one that doesn't work */
+ for (; p < 63; p++)
if (prctl(PR_CAPBSET_READ, p+1) < 0)
break;
}
}
int capability_update_inherited_set(cap_t caps, uint64_t set) {
- unsigned long i;
-
- /* Add capabilities in the set to the inherited caps. Do not apply
- * them yet. */
+ /* Add capabilities in the set to the inherited caps, drops capabilities not in the set.
+ * Do not apply them yet. */
- for (i = 0; i < cap_last_cap(); i++) {
-
- if (set & (UINT64_C(1) << i)) {
- cap_value_t v;
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ cap_flag_value_t flag = set & (UINT64_C(1) << i) ? CAP_SET : CAP_CLEAR;
+ cap_value_t v;
- v = (cap_value_t) i;
+ v = (cap_value_t) i;
- /* Make the capability inheritable. */
- if (cap_set_flag(caps, CAP_INHERITABLE, 1, &v, CAP_SET) < 0)
- return -errno;
- }
+ if (cap_set_flag(caps, CAP_INHERITABLE, 1, &v, flag) < 0)
+ return -errno;
}
return 0;
}
int capability_ambient_set_apply(uint64_t set, bool also_inherit) {
- unsigned long i;
_cleanup_cap_free_ cap_t caps = NULL;
+ int r;
- /* Add the capabilities to the ambient set. */
+ /* Remove capabilities requested in ambient set, but not in the bounding set */
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ if (set == 0)
+ break;
+
+ if (FLAGS_SET(set, (UINT64_C(1) << i)) && prctl(PR_CAPBSET_READ, i) != 1) {
+ log_debug("Ambient capability %s requested but missing from bounding set,"
+ " suppressing automatically.", capability_to_name(i));
+ set &= ~(UINT64_C(1) << i);
+ }
+ }
+
+ /* Add the capabilities to the ambient set (an possibly also the inheritable set) */
+
+ /* Check that we can use PR_CAP_AMBIENT or quit early. */
+ if (!ambient_capabilities_supported())
+ return (set & all_capabilities()) == 0 ?
+ 0 : -EOPNOTSUPP; /* if actually no ambient caps are to be set, be silent,
+ * otherwise fail recognizably */
if (also_inherit) {
- int r;
caps = cap_get_proc();
if (!caps)
return -errno;
return -errno;
}
- for (i = 0; i < cap_last_cap(); i++) {
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
if (set & (UINT64_C(1) << i)) {
/* Add the capability to the ambient set. */
if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, i, 0, 0) < 0)
return -errno;
+ } else {
+
+ /* Drop the capability so we don't inherit capabilities we didn't ask for. */
+ r = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, i, 0, 0);
+ if (r < 0)
+ return -errno;
+
+ if (r)
+ if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, i, 0, 0) < 0)
+ return -errno;
+
}
}
return 0;
}
-int capability_bounding_set_drop(uint64_t keep, bool right_now) {
- _cleanup_cap_free_ cap_t after_cap = NULL;
+int capability_gain_cap_setpcap(cap_t *ret_before_caps) {
+ _cleanup_cap_free_ cap_t caps = NULL;
cap_flag_value_t fv;
- unsigned long i;
+ caps = cap_get_proc();
+ if (!caps)
+ return -errno;
+
+ if (cap_get_flag(caps, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
+ return -errno;
+
+ if (fv != CAP_SET) {
+ _cleanup_cap_free_ cap_t temp_cap = NULL;
+ static const cap_value_t v = CAP_SETPCAP;
+
+ temp_cap = cap_dup(caps);
+ if (!temp_cap)
+ return -errno;
+
+ if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0)
+ return -errno;
+
+ if (cap_set_proc(temp_cap) < 0)
+ log_debug_errno(errno, "Can't acquire effective CAP_SETPCAP bit, ignoring: %m");
+
+ /* If we didn't manage to acquire the CAP_SETPCAP bit, we continue anyway, after all this just means
+ * we'll fail later, when we actually intend to drop some capabilities or try to set securebits. */
+ }
+ if (ret_before_caps)
+ /* Return the capabilities as they have been before setting CAP_SETPCAP */
+ *ret_before_caps = TAKE_PTR(caps);
+
+ return 0;
+}
+
+int capability_bounding_set_drop(uint64_t keep, bool right_now) {
+ _cleanup_cap_free_ cap_t before_cap = NULL, after_cap = NULL;
int r;
/* If we are run as PID 1 we will lack CAP_SETPCAP by default
* executing init!), so get it back temporarily so that we can
* call PR_CAPBSET_DROP. */
- after_cap = cap_get_proc();
+ r = capability_gain_cap_setpcap(&before_cap);
+ if (r < 0)
+ return r;
+
+ after_cap = cap_dup(before_cap);
if (!after_cap)
return -errno;
- if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
- return -errno;
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ cap_value_t v;
- if (fv != CAP_SET) {
- _cleanup_cap_free_ cap_t temp_cap = NULL;
- static const cap_value_t v = CAP_SETPCAP;
+ if ((keep & (UINT64_C(1) << i)))
+ continue;
- temp_cap = cap_dup(after_cap);
- if (!temp_cap) {
+ /* Drop it from the bounding set */
+ if (prctl(PR_CAPBSET_DROP, i) < 0) {
r = -errno;
- goto finish;
- }
- if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
- r = -errno;
- goto finish;
+ /* If dropping the capability failed, let's see if we didn't have it in the first place. If so,
+ * continue anyway, as dropping a capability we didn't have in the first place doesn't really
+ * matter anyway. */
+ if (prctl(PR_CAPBSET_READ, i) != 0)
+ goto finish;
}
+ v = (cap_value_t) i;
- if (cap_set_proc(temp_cap) < 0) {
+ /* 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;
}
- }
-
- for (i = 0; i <= cap_last_cap(); i++) {
-
- if (!(keep & (UINT64_C(1) << i))) {
- cap_value_t v;
- /* Drop it from the bounding set */
- if (prctl(PR_CAPBSET_DROP, i) < 0) {
+ /* 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;
}
- 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;
+ if (cap_set_proc(after_cap) < 0) {
+ /* If there are no actual changes anyway then let's ignore this error. */
+ if (cap_compare(before_cap, after_cap) != 0)
+ r = -errno;
+ }
return r;
}
static int drop_from_file(const char *fn, uint64_t keep) {
- int r, k;
- uint32_t hi, lo;
+ _cleanup_free_ char *p = NULL;
uint64_t current, after;
- char *p;
+ uint32_t hi, lo;
+ int r, k;
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);
-
+ k = sscanf(p, "%" PRIu32 " %" PRIu32, &lo, &hi);
if (k != 2)
return -EIO;
- current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
+ current = (uint64_t) lo | ((uint64_t) hi << 32);
after = current & keep;
if (current == after)
return 0;
- lo = (unsigned) (after & 0xFFFFFFFFULL);
- hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
+ lo = after & UINT32_C(0xFFFFFFFF);
+ hi = (after >> 32) & UINT32_C(0xFFFFFFFF);
- if (asprintf(&p, "%u %u", lo, hi) < 0)
- return -ENOMEM;
-
- r = write_string_file(fn, p, WRITE_STRING_FILE_CREATE);
- free(p);
-
- return r;
+ return write_string_filef(fn, 0, "%" PRIu32 " %" PRIu32, lo, hi);
}
int capability_bounding_set_drop_usermode(uint64_t keep) {
}
int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) {
- _cleanup_cap_free_ cap_t d = NULL;
- 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. */
+ /* 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)
return log_error_errno(errno, "Failed to change group ID: %m");
- if (setgroups(0, NULL) < 0)
- return log_error_errno(errno, "Failed to drop auxiliary groups list: %m");
+ r = maybe_setgroups(0, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to drop auxiliary groups list: %m");
- /* Ensure we keep the permitted caps across the setresuid() */
+ /* Ensure we keep the permitted caps across the setresuid(). Note that we do this even if we actually
+ * don't want to keep any capabilities, since we want to be able to drop them from the bounding set
+ * too, and we can only do that if we have capabilities. */
if (prctl(PR_SET_KEEPCAPS, 1) < 0)
return log_error_errno(errno, "Failed to enable keep capabilities flag: %m");
- r = setresuid(uid, uid, uid);
- if (r < 0)
+ if (setresuid(uid, uid, uid) < 0)
return log_error_errno(errno, "Failed to change user ID: %m");
if (prctl(PR_SET_KEEPCAPS, 0) < 0)
return log_error_errno(errno, "Failed to disable keep capabilities flag: %m");
- /* Drop all caps from the bounding set, except the ones we want */
+ /* Drop all caps from the bounding set (as well as the inheritable/permitted/effective sets), except
+ * the ones we want to keep */
r = capability_bounding_set_drop(keep_capabilities, true);
if (r < 0)
return log_error_errno(r, "Failed to drop capabilities: %m");
/* Now upgrade the permitted caps we still kept to effective caps */
- d = cap_init();
- if (!d)
- return log_oom();
-
- if (keep_capabilities) {
+ if (keep_capabilities != 0) {
cap_value_t bits[u64log2(keep_capabilities) + 1];
+ _cleanup_cap_free_ cap_t d = NULL;
+ unsigned i, j = 0;
+
+ d = cap_init();
+ if (!d)
+ return log_oom();
for (i = 0; i < ELEMENTSOF(bits); i++)
if (keep_capabilities & (1ULL << i))
/* use enough bits */
assert(i == 64 || (keep_capabilities >> i) == 0);
/* don't use too many bits */
- assert(keep_capabilities & (1ULL << (i - 1)));
+ assert(keep_capabilities & (UINT64_C(1) << (i - 1)));
if (cap_set_flag(d, CAP_EFFECTIVE, j, bits, CAP_SET) < 0 ||
cap_set_flag(d, CAP_PERMITTED, j, bits, CAP_SET) < 0)
return 0;
}
+
+bool ambient_capabilities_supported(void) {
+ static int cache = -1;
+
+ if (cache >= 0)
+ return cache;
+
+ /* If PR_CAP_AMBIENT returns something valid, or an unexpected error code we assume that ambient caps are
+ * available. */
+
+ cache = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_KILL, 0, 0) >= 0 ||
+ !IN_SET(errno, EINVAL, EOPNOTSUPP, ENOSYS);
+
+ return cache;
+}
+
+bool capability_quintet_mangle(CapabilityQuintet *q) {
+ uint64_t combined, drop = 0;
+ bool ambient_supported;
+
+ assert(q);
+
+ combined = q->effective | q->bounding | q->inheritable | q->permitted;
+
+ ambient_supported = q->ambient != (uint64_t) -1;
+ if (ambient_supported)
+ combined |= q->ambient;
+
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ unsigned long bit = UINT64_C(1) << i;
+ if (!FLAGS_SET(combined, bit))
+ continue;
+
+ if (prctl(PR_CAPBSET_READ, i) > 0)
+ continue;
+
+ drop |= bit;
+
+ log_debug("Not in the current bounding set: %s", capability_to_name(i));
+ }
+
+ q->effective &= ~drop;
+ q->bounding &= ~drop;
+ q->inheritable &= ~drop;
+ q->permitted &= ~drop;
+
+ if (ambient_supported)
+ q->ambient &= ~drop;
+
+ return drop != 0; /* Let the caller know we changed something */
+}
+
+int capability_quintet_enforce(const CapabilityQuintet *q) {
+ _cleanup_cap_free_ cap_t c = NULL, modified = NULL;
+ int r;
+
+ if (q->ambient != (uint64_t) -1) {
+ bool changed = false;
+
+ c = cap_get_proc();
+ if (!c)
+ return -errno;
+
+ /* In order to raise the ambient caps set we first need to raise the matching
+ * inheritable + permitted cap */
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ uint64_t m = UINT64_C(1) << i;
+ cap_value_t cv = (cap_value_t) i;
+ cap_flag_value_t old_value_inheritable, old_value_permitted;
+
+ if ((q->ambient & m) == 0)
+ continue;
+
+ if (cap_get_flag(c, cv, CAP_INHERITABLE, &old_value_inheritable) < 0)
+ return -errno;
+ if (cap_get_flag(c, cv, CAP_PERMITTED, &old_value_permitted) < 0)
+ return -errno;
+
+ if (old_value_inheritable == CAP_SET && old_value_permitted == CAP_SET)
+ continue;
+
+ if (cap_set_flag(c, CAP_INHERITABLE, 1, &cv, CAP_SET) < 0)
+ return -errno;
+ if (cap_set_flag(c, CAP_PERMITTED, 1, &cv, CAP_SET) < 0)
+ return -errno;
+
+ changed = true;
+ }
+
+ if (changed)
+ if (cap_set_proc(c) < 0)
+ return -errno;
+
+ r = capability_ambient_set_apply(q->ambient, false);
+ if (r < 0)
+ return r;
+ }
+
+ if (q->inheritable != (uint64_t) -1 || q->permitted != (uint64_t) -1 || q->effective != (uint64_t) -1) {
+ bool changed = false;
+
+ if (!c) {
+ c = cap_get_proc();
+ if (!c)
+ return -errno;
+ }
+
+ for (unsigned i = 0; i <= cap_last_cap(); i++) {
+ uint64_t m = UINT64_C(1) << i;
+ cap_value_t cv = (cap_value_t) i;
+
+ if (q->inheritable != (uint64_t) -1) {
+ cap_flag_value_t old_value, new_value;
+
+ if (cap_get_flag(c, cv, CAP_INHERITABLE, &old_value) < 0) {
+ if (errno == EINVAL) /* If the kernel knows more caps than this
+ * version of libcap, then this will return
+ * EINVAL. In that case, simply ignore it,
+ * pretend it doesn't exist. */
+ continue;
+
+ return -errno;
+ }
+
+ new_value = (q->inheritable & m) ? CAP_SET : CAP_CLEAR;
+
+ if (old_value != new_value) {
+ changed = true;
+
+ if (cap_set_flag(c, CAP_INHERITABLE, 1, &cv, new_value) < 0)
+ return -errno;
+ }
+ }
+
+ if (q->permitted != (uint64_t) -1) {
+ cap_flag_value_t old_value, new_value;
+
+ if (cap_get_flag(c, cv, CAP_PERMITTED, &old_value) < 0) {
+ if (errno == EINVAL)
+ continue;
+
+ return -errno;
+ }
+
+ new_value = (q->permitted & m) ? CAP_SET : CAP_CLEAR;
+
+ if (old_value != new_value) {
+ changed = true;
+
+ if (cap_set_flag(c, CAP_PERMITTED, 1, &cv, new_value) < 0)
+ return -errno;
+ }
+ }
+
+ if (q->effective != (uint64_t) -1) {
+ cap_flag_value_t old_value, new_value;
+
+ if (cap_get_flag(c, cv, CAP_EFFECTIVE, &old_value) < 0) {
+ if (errno == EINVAL)
+ continue;
+
+ return -errno;
+ }
+
+ new_value = (q->effective & m) ? CAP_SET : CAP_CLEAR;
+
+ if (old_value != new_value) {
+ changed = true;
+
+ if (cap_set_flag(c, CAP_EFFECTIVE, 1, &cv, new_value) < 0)
+ return -errno;
+ }
+ }
+ }
+
+ if (changed) {
+ /* In order to change the bounding caps, we need to keep CAP_SETPCAP for a bit
+ * longer. Let's add it to our list hence for now. */
+ if (q->bounding != (uint64_t) -1) {
+ cap_value_t cv = CAP_SETPCAP;
+
+ modified = cap_dup(c);
+ if (!modified)
+ return -ENOMEM;
+
+ if (cap_set_flag(modified, CAP_PERMITTED, 1, &cv, CAP_SET) < 0)
+ return -errno;
+ if (cap_set_flag(modified, CAP_EFFECTIVE, 1, &cv, CAP_SET) < 0)
+ return -errno;
+
+ if (cap_compare(modified, c) == 0) {
+ /* No change? then drop this nonsense again */
+ cap_free(modified);
+ modified = NULL;
+ }
+ }
+
+ /* Now, let's enforce the caps for the first time. Note that this is where we acquire
+ * caps in any of the sets we currently don't have. We have to do this before
+ * dropping the bounding caps below, since at that point we can never acquire new
+ * caps in inherited/permitted/effective anymore, but only lose them. */
+ if (cap_set_proc(modified ?: c) < 0)
+ return -errno;
+ }
+ }
+
+ if (q->bounding != (uint64_t) -1) {
+ r = capability_bounding_set_drop(q->bounding, false);
+ if (r < 0)
+ return r;
+ }
+
+ /* If needed, let's now set the caps again, this time in the final version, which differs from what
+ * we have already set only in the CAP_SETPCAP bit, which we needed for dropping the bounding
+ * bits. This call only undoes bits and doesn't acquire any which means the bounding caps don't
+ * matter. */
+ if (modified)
+ if (cap_set_proc(c) < 0)
+ return -errno;
+
+ return 0;
+}
projects / thirdparty / systemd.git / blobdiff