diff options
Diffstat (limited to 'src/shared/capability.c')
| -rw-r--r-- | src/shared/capability.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/src/shared/capability.c b/src/shared/capability.c new file mode 100644 index 0000000000..9b743e86d0 --- /dev/null +++ b/src/shared/capability.c @@ -0,0 +1,224 @@ +/*-*- 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 <assert.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <stdio.h> +#include <sys/types.h> +#include <stdarg.h> +#include <ctype.h> +#include <sys/capability.h> +#include <sys/prctl.h> + +#include "macro.h" +#include "capability.h" +#include "util.h" +#include "log.h" + +int have_effective_cap(int value) { + cap_t cap; + cap_flag_value_t fv; + int r; + + cap = cap_get_proc(); + if (!cap) + return -errno; + + if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0) + r = -errno; + else + r = fv == CAP_SET; + + cap_free(cap); + return r; +} + +unsigned long cap_last_cap(void) { + static __thread unsigned long saved; + static __thread bool valid = false; + unsigned long p; + + if (valid) + return saved; + + 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) { + unsigned long i; + 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) { + cap_free(after_cap); + 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 = 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 (temp_cap) + cap_free(temp_cap); + + if (after_cap) { + cap_set_proc(after_cap); + cap_free(after_cap); + } + + 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_one_line_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; +} |