1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 #include <linux/if_alg.h>
5 #include <sys/socket.h>
7 #include "alloc-util.h"
13 #include "string-util.h"
16 /* On current kernels the maximum digest (according to "grep digestsize /proc/crypto | sort -u") is actually 32, but
17 * let's add some extra room, the few wasted bytes don't really matter... */
18 #define LONGEST_DIGEST 128
23 uint8_t digest[LONGEST_DIGEST+1];
28 int khash_supported(void) {
31 struct sockaddr_alg alg;
33 .alg.salg_family = AF_ALG,
34 .alg.salg_type = "hash",
35 .alg.salg_name = "sha256", /* a very common algorithm */
38 static int cached = -1;
41 _cleanup_close_ int fd1 = -1, fd2 = -1;
42 uint8_t buf[LONGEST_DIGEST+1];
44 fd1 = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
46 /* The kernel returns EAFNOSUPPORT if AF_ALG is not supported at all */
47 if (IN_SET(errno, EAFNOSUPPORT, EOPNOTSUPP))
48 return (cached = false);
53 if (bind(fd1, &sa.sa, sizeof(sa)) < 0) {
54 /* The kernel returns ENOENT if the selected algorithm is not supported at all. We use a check
55 * for SHA256 as a proxy for whether the whole API is supported at all. After all it's one of
56 * the most common hash functions, and if it isn't supported, that's ample indication that
57 * something is really off. */
59 if (IN_SET(errno, ENOENT, EOPNOTSUPP))
60 return (cached = false);
65 fd2 = accept4(fd1, NULL, 0, SOCK_CLOEXEC);
67 if (errno == EOPNOTSUPP)
68 return (cached = false);
73 if (recv(fd2, buf, sizeof(buf), 0) < 0) {
74 /* On some kernels we get ENOKEY for non-keyed hash functions (such as sha256), let's refuse
75 * using the API in those cases, since the kernel is
76 * broken. https://github.com/systemd/systemd/issues/8278 */
78 if (IN_SET(errno, ENOKEY, EOPNOTSUPP))
79 return (cached = false);
88 int khash_new_with_key(khash **ret, const char *algorithm, const void *key, size_t key_size) {
91 struct sockaddr_alg alg;
93 .alg.salg_family = AF_ALG,
94 .alg.salg_type = "hash",
97 _cleanup_(khash_unrefp) khash *h = NULL;
98 _cleanup_close_ int fd = -1;
103 assert(key || key_size == 0);
105 /* Filter out an empty algorithm early, as we do not support an algorithm by that name. */
106 if (isempty(algorithm))
109 /* Overly long hash algorithm names we definitely do not support */
110 if (strlen(algorithm) >= sizeof(sa.alg.salg_name))
113 supported = khash_supported();
119 fd = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
123 strcpy((char*) sa.alg.salg_name, algorithm);
124 if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
131 if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, key, key_size) < 0)
139 h->fd = accept4(fd, NULL, 0, SOCK_CLOEXEC);
143 h->algorithm = strdup(algorithm);
147 /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
148 (void) send(h->fd, NULL, 0, 0);
150 /* Figure out the digest size */
151 n = recv(h->fd, h->digest, sizeof(h->digest), 0);
154 if (n >= LONGEST_DIGEST) /* longer than what we expected? If so, we don't support this */
157 h->digest_size = (size_t) n;
158 h->digest_valid = true;
160 /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
161 (void) send(h->fd, NULL, 0, 0);
169 int khash_new(khash **ret, const char *algorithm) {
170 return khash_new_with_key(ret, algorithm, NULL, 0);
173 khash* khash_unref(khash *h) {
182 int khash_dup(khash *h, khash **ret) {
183 _cleanup_(khash_unrefp) khash *copy = NULL;
188 copy = newdup(khash, h, 1);
193 copy->algorithm = strdup(h->algorithm);
194 if (!copy->algorithm)
197 copy->fd = accept4(h->fd, NULL, 0, SOCK_CLOEXEC);
201 *ret = TAKE_PTR(copy);
206 const char *khash_get_algorithm(khash *h) {
212 size_t khash_get_size(khash *h) {
215 return h->digest_size;
218 int khash_reset(khash *h) {
223 n = send(h->fd, NULL, 0, 0);
227 h->digest_valid = false;
232 int khash_put(khash *h, const void *buffer, size_t size) {
236 assert(buffer || size == 0);
241 n = send(h->fd, buffer, size, MSG_MORE);
245 h->digest_valid = false;
250 int khash_put_iovec(khash *h, const struct iovec *iovec, size_t n) {
252 mh.msg_iov = (struct iovec*) iovec,
258 assert(iovec || n == 0);
263 k = sendmsg(h->fd, &mh, MSG_MORE);
267 h->digest_valid = false;
272 static int retrieve_digest(khash *h) {
280 n = recv(h->fd, h->digest, h->digest_size, 0);
283 if ((size_t) n != h->digest_size) /* digest size changed? */
286 h->digest_valid = true;
291 int khash_digest_data(khash *h, const void **ret) {
297 r = retrieve_digest(h);
305 int khash_digest_string(khash *h, char **ret) {
312 r = retrieve_digest(h);
316 p = hexmem(h->digest, h->digest_size);