1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 Copyright 2016 Lennart Poettering
6 #include <linux/if_alg.h>
8 #include <sys/socket.h>
10 #include "alloc-util.h"
12 #include "hexdecoct.h"
16 #include "string-util.h"
19 /* On current kernels the maximum digest (according to "grep digestsize /proc/crypto | sort -u") is actually 32, but
20 * let's add some extra room, the few wasted bytes don't really matter... */
21 #define LONGEST_DIGEST 128
26 uint8_t digest[LONGEST_DIGEST+1];
31 int khash_supported(void) {
34 struct sockaddr_alg alg;
36 .alg.salg_family = AF_ALG,
37 .alg.salg_type = "hash",
38 .alg.salg_name = "sha256", /* a very common algorithm */
41 static int cached = -1;
44 _cleanup_close_ int fd1 = -1, fd2 = -1;
45 uint8_t buf[LONGEST_DIGEST+1];
47 fd1 = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
49 /* The kernel returns EAFNOSUPPORT if AF_ALG is not supported at all */
50 if (IN_SET(errno, EAFNOSUPPORT, EOPNOTSUPP))
51 return (cached = false);
56 if (bind(fd1, &sa.sa, sizeof(sa)) < 0) {
57 /* The kernel returns ENOENT if the selected algorithm is not supported at all. We use a check
58 * for SHA256 as a proxy for whether the whole API is supported at all. After all it's one of
59 * the most common hash functions, and if it isn't supported, that's ample indication that
60 * something is really off. */
62 if (IN_SET(errno, ENOENT, EOPNOTSUPP))
63 return (cached = false);
68 fd2 = accept4(fd1, NULL, 0, SOCK_CLOEXEC);
70 if (errno == EOPNOTSUPP)
71 return (cached = false);
76 if (recv(fd2, buf, sizeof(buf), 0) < 0) {
77 /* On some kernels we get ENOKEY for non-keyed hash functions (such as sha256), let's refuse
78 * using the API in those cases, since the kernel is
79 * broken. https://github.com/systemd/systemd/issues/8278 */
81 if (IN_SET(errno, ENOKEY, EOPNOTSUPP))
82 return (cached = false);
91 int khash_new_with_key(khash **ret, const char *algorithm, const void *key, size_t key_size) {
94 struct sockaddr_alg alg;
96 .alg.salg_family = AF_ALG,
97 .alg.salg_type = "hash",
100 _cleanup_(khash_unrefp) khash *h = NULL;
101 _cleanup_close_ int fd = -1;
106 assert(key || key_size == 0);
108 /* Filter out an empty algorithm early, as we do not support an algorithm by that name. */
109 if (isempty(algorithm))
112 /* Overly long hash algorithm names we definitely do not support */
113 if (strlen(algorithm) >= sizeof(sa.alg.salg_name))
116 supported = khash_supported();
122 fd = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
126 strcpy((char*) sa.alg.salg_name, algorithm);
127 if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
134 if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, key, key_size) < 0)
142 h->fd = accept4(fd, NULL, 0, SOCK_CLOEXEC);
146 h->algorithm = strdup(algorithm);
150 /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
151 (void) send(h->fd, NULL, 0, 0);
153 /* Figure out the digest size */
154 n = recv(h->fd, h->digest, sizeof(h->digest), 0);
157 if (n >= LONGEST_DIGEST) /* longer than what we expected? If so, we don't support this */
160 h->digest_size = (size_t) n;
161 h->digest_valid = true;
163 /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
164 (void) send(h->fd, NULL, 0, 0);
172 int khash_new(khash **ret, const char *algorithm) {
173 return khash_new_with_key(ret, algorithm, NULL, 0);
176 khash* khash_unref(khash *h) {
185 int khash_dup(khash *h, khash **ret) {
186 _cleanup_(khash_unrefp) khash *copy = NULL;
191 copy = newdup(khash, h, 1);
196 copy->algorithm = strdup(h->algorithm);
197 if (!copy->algorithm)
200 copy->fd = accept4(h->fd, NULL, 0, SOCK_CLOEXEC);
204 *ret = TAKE_PTR(copy);
209 const char *khash_get_algorithm(khash *h) {
215 size_t khash_get_size(khash *h) {
218 return h->digest_size;
221 int khash_reset(khash *h) {
226 n = send(h->fd, NULL, 0, 0);
230 h->digest_valid = false;
235 int khash_put(khash *h, const void *buffer, size_t size) {
239 assert(buffer || size == 0);
244 n = send(h->fd, buffer, size, MSG_MORE);
248 h->digest_valid = false;
253 int khash_put_iovec(khash *h, const struct iovec *iovec, size_t n) {
255 mh.msg_iov = (struct iovec*) iovec,
261 assert(iovec || n == 0);
266 k = sendmsg(h->fd, &mh, MSG_MORE);
270 h->digest_valid = false;
275 static int retrieve_digest(khash *h) {
283 n = recv(h->fd, h->digest, h->digest_size, 0);
286 if ((size_t) n != h->digest_size) /* digest size changed? */
289 h->digest_valid = true;
294 int khash_digest_data(khash *h, const void **ret) {
300 r = retrieve_digest(h);
308 int khash_digest_string(khash *h, char **ret) {
315 r = retrieve_digest(h);
319 p = hexmem(h->digest, h->digest_size);