308 lines
9.6 KiB
C
308 lines
9.6 KiB
C
/*-*- 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/>.
|
|
***/
|
|
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
#include <sys/capability.h>
|
|
#include <sys/prctl.h>
|
|
#include "grp.h"
|
|
|
|
#include "macro.h"
|
|
#include "util.h"
|
|
#include "log.h"
|
|
#include "fileio.h"
|
|
#include "capability.h"
|
|
|
|
int have_effective_cap(int value) {
|
|
_cleanup_cap_free_ cap_t cap;
|
|
cap_flag_value_t fv;
|
|
|
|
cap = cap_get_proc();
|
|
if (!cap)
|
|
return -errno;
|
|
|
|
if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
|
|
return -errno;
|
|
else
|
|
return fv == CAP_SET;
|
|
}
|
|
|
|
unsigned long cap_last_cap(void) {
|
|
static thread_local unsigned long saved;
|
|
static thread_local bool valid = false;
|
|
_cleanup_free_ char *content = NULL;
|
|
unsigned long p = 0;
|
|
int r;
|
|
|
|
if (valid)
|
|
return saved;
|
|
|
|
/* available since linux-3.2 */
|
|
r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
|
|
if (r >= 0) {
|
|
r = safe_atolu(content, &p);
|
|
if (r >= 0) {
|
|
saved = p;
|
|
valid = true;
|
|
return p;
|
|
}
|
|
}
|
|
|
|
/* fall back to syscall-probing for pre linux-3.2 */
|
|
p = (unsigned long) CAP_LAST_CAP;
|
|
|
|
if (prctl(PR_CAPBSET_READ, p) < 0) {
|
|
|
|
/* 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++)
|
|
if (prctl(PR_CAPBSET_READ, p+1) < 0)
|
|
break;
|
|
}
|
|
|
|
saved = p;
|
|
valid = true;
|
|
|
|
return p;
|
|
}
|
|
|
|
int capability_bounding_set_drop(uint64_t drop, bool right_now) {
|
|
_cleanup_cap_free_ cap_t after_cap = NULL;
|
|
cap_flag_value_t fv;
|
|
unsigned long i;
|
|
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) {
|
|
_cleanup_cap_free_ cap_t temp_cap = NULL;
|
|
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_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. */
|
|
|
|
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");
|
|
|
|
/* Ensure we keep the permitted caps across the setresuid() */
|
|
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)
|
|
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 */
|
|
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) {
|
|
cap_value_t bits[u64log2(keep_capabilities) + 1];
|
|
|
|
for (i = 0; i < ELEMENTSOF(bits); i++)
|
|
if (keep_capabilities & (1ULL << i))
|
|
bits[j++] = i;
|
|
|
|
/* use enough bits */
|
|
assert(i == 64 || (keep_capabilities >> i) == 0);
|
|
/* don't use too many bits */
|
|
assert(keep_capabilities & (1ULL << (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) {
|
|
log_error_errno(errno, "Failed to enable capabilities bits: %m");
|
|
return -errno;
|
|
}
|
|
|
|
if (cap_set_proc(d) < 0)
|
|
return log_error_errno(errno, "Failed to increase capabilities: %m");
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int drop_capability(cap_value_t cv) {
|
|
_cleanup_cap_free_ cap_t tmp_cap = NULL;
|
|
|
|
tmp_cap = cap_get_proc();
|
|
if (!tmp_cap)
|
|
return -errno;
|
|
|
|
if ((cap_set_flag(tmp_cap, CAP_INHERITABLE, 1, &cv, CAP_CLEAR) < 0) ||
|
|
(cap_set_flag(tmp_cap, CAP_PERMITTED, 1, &cv, CAP_CLEAR) < 0) ||
|
|
(cap_set_flag(tmp_cap, CAP_EFFECTIVE, 1, &cv, CAP_CLEAR) < 0))
|
|
return -errno;
|
|
|
|
if (cap_set_proc(tmp_cap) < 0)
|
|
return -errno;
|
|
|
|
return 0;
|
|
}
|