+++ /dev/null
-/*-*- 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, WRITE_STRING_FILE_CREATE);
- 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;
-}
~ianmdlvl / elogind.git / blobdiff