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1 | /* SPDX-License-Identifier: LGPL-2.1+ */ | |
2 | ||
3 | #include <linux/if_alg.h> | |
4 | #include <stdbool.h> | |
5 | #include <sys/socket.h> | |
6 | ||
7 | #include "alloc-util.h" | |
8 | #include "fd-util.h" | |
9 | #include "hexdecoct.h" | |
10 | #include "khash.h" | |
11 | #include "macro.h" | |
12 | #include "missing.h" | |
13 | #include "string-util.h" | |
14 | #include "util.h" | |
15 | ||
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 | |
19 | ||
20 | struct khash { | |
21 | int fd; | |
22 | char *algorithm; | |
23 | uint8_t digest[LONGEST_DIGEST+1]; | |
24 | size_t digest_size; | |
25 | bool digest_valid; | |
26 | }; | |
27 | ||
28 | int khash_supported(void) { | |
29 | static const union { | |
30 | struct sockaddr sa; | |
31 | struct sockaddr_alg alg; | |
32 | } sa = { | |
33 | .alg.salg_family = AF_ALG, | |
34 | .alg.salg_type = "hash", | |
35 | .alg.salg_name = "sha256", /* a very common algorithm */ | |
36 | }; | |
37 | ||
38 | static int cached = -1; | |
39 | ||
40 | if (cached < 0) { | |
41 | _cleanup_close_ int fd1 = -1, fd2 = -1; | |
42 | uint8_t buf[LONGEST_DIGEST+1]; | |
43 | ||
44 | fd1 = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0); | |
45 | if (fd1 < 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); | |
49 | ||
50 | return -errno; | |
51 | } | |
52 | ||
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. */ | |
58 | ||
59 | if (IN_SET(errno, ENOENT, EOPNOTSUPP)) | |
60 | return (cached = false); | |
61 | ||
62 | return -errno; | |
63 | } | |
64 | ||
65 | fd2 = accept4(fd1, NULL, 0, SOCK_CLOEXEC); | |
66 | if (fd2 < 0) { | |
67 | if (errno == EOPNOTSUPP) | |
68 | return (cached = false); | |
69 | ||
70 | return -errno; | |
71 | } | |
72 | ||
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 */ | |
77 | ||
78 | if (IN_SET(errno, ENOKEY, EOPNOTSUPP)) | |
79 | return (cached = false); | |
80 | } | |
81 | ||
82 | cached = true; | |
83 | } | |
84 | ||
85 | return cached; | |
86 | } | |
87 | ||
88 | int khash_new_with_key(khash **ret, const char *algorithm, const void *key, size_t key_size) { | |
89 | union { | |
90 | struct sockaddr sa; | |
91 | struct sockaddr_alg alg; | |
92 | } sa = { | |
93 | .alg.salg_family = AF_ALG, | |
94 | .alg.salg_type = "hash", | |
95 | }; | |
96 | ||
97 | _cleanup_(khash_unrefp) khash *h = NULL; | |
98 | _cleanup_close_ int fd = -1; | |
99 | int supported; | |
100 | ssize_t n; | |
101 | ||
102 | assert(ret); | |
103 | assert(key || key_size == 0); | |
104 | ||
105 | /* Filter out an empty algorithm early, as we do not support an algorithm by that name. */ | |
106 | if (isempty(algorithm)) | |
107 | return -EINVAL; | |
108 | ||
109 | /* Overly long hash algorithm names we definitely do not support */ | |
110 | if (strlen(algorithm) >= sizeof(sa.alg.salg_name)) | |
111 | return -EOPNOTSUPP; | |
112 | ||
113 | supported = khash_supported(); | |
114 | if (supported < 0) | |
115 | return supported; | |
116 | if (supported == 0) | |
117 | return -EOPNOTSUPP; | |
118 | ||
119 | fd = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0); | |
120 | if (fd < 0) | |
121 | return -errno; | |
122 | ||
123 | strcpy((char*) sa.alg.salg_name, algorithm); | |
124 | if (bind(fd, &sa.sa, sizeof(sa)) < 0) { | |
125 | if (errno == ENOENT) | |
126 | return -EOPNOTSUPP; | |
127 | return -errno; | |
128 | } | |
129 | ||
130 | if (key) { | |
131 | if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, key, key_size) < 0) | |
132 | return -errno; | |
133 | } | |
134 | ||
135 | h = new0(khash, 1); | |
136 | if (!h) | |
137 | return -ENOMEM; | |
138 | ||
139 | h->fd = accept4(fd, NULL, 0, SOCK_CLOEXEC); | |
140 | if (h->fd < 0) | |
141 | return -errno; | |
142 | ||
143 | h->algorithm = strdup(algorithm); | |
144 | if (!h->algorithm) | |
145 | return -ENOMEM; | |
146 | ||
147 | /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */ | |
148 | (void) send(h->fd, NULL, 0, 0); | |
149 | ||
150 | /* Figure out the digest size */ | |
151 | n = recv(h->fd, h->digest, sizeof(h->digest), 0); | |
152 | if (n < 0) | |
153 | return -errno; | |
154 | if (n >= LONGEST_DIGEST) /* longer than what we expected? If so, we don't support this */ | |
155 | return -EOPNOTSUPP; | |
156 | ||
157 | h->digest_size = (size_t) n; | |
158 | h->digest_valid = true; | |
159 | ||
160 | /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */ | |
161 | (void) send(h->fd, NULL, 0, 0); | |
162 | ||
163 | *ret = h; | |
164 | h = NULL; | |
165 | ||
166 | return 0; | |
167 | } | |
168 | ||
169 | int khash_new(khash **ret, const char *algorithm) { | |
170 | return khash_new_with_key(ret, algorithm, NULL, 0); | |
171 | } | |
172 | ||
173 | khash* khash_unref(khash *h) { | |
174 | if (!h) | |
175 | return NULL; | |
176 | ||
177 | safe_close(h->fd); | |
178 | free(h->algorithm); | |
179 | return mfree(h); | |
180 | } | |
181 | ||
182 | int khash_dup(khash *h, khash **ret) { | |
183 | _cleanup_(khash_unrefp) khash *copy = NULL; | |
184 | ||
185 | assert(h); | |
186 | assert(ret); | |
187 | ||
188 | copy = newdup(khash, h, 1); | |
189 | if (!copy) | |
190 | return -ENOMEM; | |
191 | ||
192 | copy->fd = -1; | |
193 | copy->algorithm = strdup(h->algorithm); | |
194 | if (!copy->algorithm) | |
195 | return -ENOMEM; | |
196 | ||
197 | copy->fd = accept4(h->fd, NULL, 0, SOCK_CLOEXEC); | |
198 | if (copy->fd < 0) | |
199 | return -errno; | |
200 | ||
201 | *ret = TAKE_PTR(copy); | |
202 | ||
203 | return 0; | |
204 | } | |
205 | ||
206 | const char *khash_get_algorithm(khash *h) { | |
207 | assert(h); | |
208 | ||
209 | return h->algorithm; | |
210 | } | |
211 | ||
212 | size_t khash_get_size(khash *h) { | |
213 | assert(h); | |
214 | ||
215 | return h->digest_size; | |
216 | } | |
217 | ||
218 | int khash_reset(khash *h) { | |
219 | ssize_t n; | |
220 | ||
221 | assert(h); | |
222 | ||
223 | n = send(h->fd, NULL, 0, 0); | |
224 | if (n < 0) | |
225 | return -errno; | |
226 | ||
227 | h->digest_valid = false; | |
228 | ||
229 | return 0; | |
230 | } | |
231 | ||
232 | int khash_put(khash *h, const void *buffer, size_t size) { | |
233 | ssize_t n; | |
234 | ||
235 | assert(h); | |
236 | assert(buffer || size == 0); | |
237 | ||
238 | if (size <= 0) | |
239 | return 0; | |
240 | ||
241 | n = send(h->fd, buffer, size, MSG_MORE); | |
242 | if (n < 0) | |
243 | return -errno; | |
244 | ||
245 | h->digest_valid = false; | |
246 | ||
247 | return 0; | |
248 | } | |
249 | ||
250 | int khash_put_iovec(khash *h, const struct iovec *iovec, size_t n) { | |
251 | struct msghdr mh = { | |
252 | mh.msg_iov = (struct iovec*) iovec, | |
253 | mh.msg_iovlen = n, | |
254 | }; | |
255 | ssize_t k; | |
256 | ||
257 | assert(h); | |
258 | assert(iovec || n == 0); | |
259 | ||
260 | if (n <= 0) | |
261 | return 0; | |
262 | ||
263 | k = sendmsg(h->fd, &mh, MSG_MORE); | |
264 | if (k < 0) | |
265 | return -errno; | |
266 | ||
267 | h->digest_valid = false; | |
268 | ||
269 | return 0; | |
270 | } | |
271 | ||
272 | static int retrieve_digest(khash *h) { | |
273 | ssize_t n; | |
274 | ||
275 | assert(h); | |
276 | ||
277 | if (h->digest_valid) | |
278 | return 0; | |
279 | ||
280 | n = recv(h->fd, h->digest, h->digest_size, 0); | |
281 | if (n < 0) | |
282 | return n; | |
283 | if ((size_t) n != h->digest_size) /* digest size changed? */ | |
284 | return -EIO; | |
285 | ||
286 | h->digest_valid = true; | |
287 | ||
288 | return 0; | |
289 | } | |
290 | ||
291 | int khash_digest_data(khash *h, const void **ret) { | |
292 | int r; | |
293 | ||
294 | assert(h); | |
295 | assert(ret); | |
296 | ||
297 | r = retrieve_digest(h); | |
298 | if (r < 0) | |
299 | return r; | |
300 | ||
301 | *ret = h->digest; | |
302 | return 0; | |
303 | } | |
304 | ||
305 | int khash_digest_string(khash *h, char **ret) { | |
306 | int r; | |
307 | char *p; | |
308 | ||
309 | assert(h); | |
310 | assert(ret); | |
311 | ||
312 | r = retrieve_digest(h); | |
313 | if (r < 0) | |
314 | return r; | |
315 | ||
316 | p = hexmem(h->digest, h->digest_size); | |
317 | if (!p) | |
318 | return -ENOMEM; | |
319 | ||
320 | *ret = p; | |
321 | return 0; | |
322 | } |