dccca82b1a
log.h really should only include the bare minimum of other headers, as it is really pulled into pretty much everything else and already in itself one of the most basic pieces of code we have. Let's hence drop inclusion of: 1. sd-id128.h because it's entirely unneeded in current log.h 2. errno.h, dito. 3. sys/signalfd.h which we can replace by a simple struct forward declaration 4. process-util.h which was needed for getpid_cached() which we now hide in a funciton log_emergency_level() instead, which nicely abstracts the details away. 5. sys/socket.h which was needed for struct iovec, but a simple struct forward declaration suffices for that too. Ultimately this actually makes our source tree larger (since users of the functionality above must now include it themselves, log.h won't do that for them), but I think it helps to untangle our web of includes a tiny bit. (Background: I'd like to isolate the generic bits of src/basic/ enough so that we can do a git submodule import into casync for it)
174 lines
5.4 KiB
C
174 lines
5.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <elf.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/random.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/time.h>
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#if HAVE_SYS_AUXV_H
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# include <sys/auxv.h>
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#endif
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#if USE_SYS_RANDOM_H
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# include <sys/random.h>
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#else
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# include <linux/random.h>
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#endif
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#include "fd-util.h"
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#include "io-util.h"
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#include "missing.h"
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#include "random-util.h"
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#include "time-util.h"
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int acquire_random_bytes(void *p, size_t n, bool high_quality_required) {
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static int have_syscall = -1;
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_cleanup_close_ int fd = -1;
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unsigned already_done = 0;
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int r;
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/* Gathers some randomness from the kernel. This call will never block. If
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* high_quality_required, it will always return some data from the kernel,
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* regardless of whether the random pool is fully initialized or not.
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* Otherwise, it will return success if at least some random bytes were
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* successfully acquired, and an error if the kernel has no entropy whatsover
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* for us. */
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/* Use the getrandom() syscall unless we know we don't have it. */
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if (have_syscall != 0) {
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r = getrandom(p, n, GRND_NONBLOCK);
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if (r > 0) {
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have_syscall = true;
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if ((size_t) r == n)
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return 0;
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if (!high_quality_required) {
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/* Fill in the remaining bytes using pseudorandom values */
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pseudorandom_bytes((uint8_t*) p + r, n - r);
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return 0;
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}
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already_done = r;
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} else if (errno == ENOSYS)
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/* We lack the syscall, continue with reading from /dev/urandom. */
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have_syscall = false;
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else if (errno == EAGAIN) {
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/* The kernel has no entropy whatsoever. Let's remember to
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* use the syscall the next time again though.
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*
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* If high_quality_required is false, return an error so that
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* random_bytes() can produce some pseudorandom
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* bytes. Otherwise, fall back to /dev/urandom, which we know
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* is empty, but the kernel will produce some bytes for us on
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* a best-effort basis. */
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have_syscall = true;
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if (!high_quality_required)
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return -ENODATA;
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} else
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return -errno;
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}
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fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (fd < 0)
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return errno == ENOENT ? -ENOSYS : -errno;
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return loop_read_exact(fd, (uint8_t*) p + already_done, n - already_done, true);
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}
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void initialize_srand(void) {
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static bool srand_called = false;
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unsigned x;
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#if HAVE_SYS_AUXV_H
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void *auxv;
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#endif
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if (srand_called)
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return;
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#if HAVE_SYS_AUXV_H
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/* The kernel provides us with 16 bytes of entropy in auxv, so let's
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* try to make use of that to seed the pseudo-random generator. It's
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* better than nothing... */
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auxv = (void*) getauxval(AT_RANDOM);
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if (auxv) {
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assert_cc(sizeof(x) <= 16);
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memcpy(&x, auxv, sizeof(x));
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} else
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#endif
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x = 0;
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x ^= (unsigned) now(CLOCK_REALTIME);
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x ^= (unsigned) gettid();
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srand(x);
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srand_called = true;
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}
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/* INT_MAX gives us only 31 bits, so use 24 out of that. */
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#if RAND_MAX >= INT_MAX
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# define RAND_STEP 3
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#else
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/* SHORT_INT_MAX or lower gives at most 15 bits, we just just 8 out of that. */
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# define RAND_STEP 1
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#endif
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void pseudorandom_bytes(void *p, size_t n) {
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uint8_t *q;
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initialize_srand();
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for (q = p; q < (uint8_t*) p + n; q += RAND_STEP) {
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unsigned rr;
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rr = (unsigned) rand();
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#if RAND_STEP >= 3
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if ((size_t) (q - (uint8_t*) p + 2) < n)
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q[2] = rr >> 16;
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#endif
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#if RAND_STEP >= 2
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if ((size_t) (q - (uint8_t*) p + 1) < n)
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q[1] = rr >> 8;
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#endif
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q[0] = rr;
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}
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}
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void random_bytes(void *p, size_t n) {
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int r;
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r = acquire_random_bytes(p, n, false);
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if (r >= 0)
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return;
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/* If some idiot made /dev/urandom unavailable to us, or the
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* kernel has no entropy, use a PRNG instead. */
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return pseudorandom_bytes(p, n);
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}
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