1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * RSA Signature Scheme with Appendix - PKCS #1 v1.5 (RFC 8017 sec 8.2)
4 *
5 * https://www.rfc-editor.org/rfc/rfc8017#section-8.2
6 *
7 * Copyright (c) 2015 - 2024 Intel Corporation
8 */
9
10#include <linux/module.h>
11#include <linux/scatterlist.h>
12#include <crypto/akcipher.h>
13#include <crypto/algapi.h>
14#include <crypto/hash.h>
15#include <crypto/sig.h>
16#include <crypto/internal/akcipher.h>
17#include <crypto/internal/rsa.h>
18#include <crypto/internal/sig.h>
19
20/*
21 * Full Hash Prefix for EMSA-PKCS1-v1_5 encoding method (RFC 9580 table 24)
22 *
23 * RSA keys are usually much larger than the hash of the message to be signed.
24 * The hash is therefore prepended by the Full Hash Prefix and a 0xff padding.
25 * The Full Hash Prefix is an ASN.1 SEQUENCE containing the hash algorithm OID.
26 *
27 * https://www.rfc-editor.org/rfc/rfc9580#table-24
28 */
29
30static const u8 hash_prefix_none[] = { };
31
32static const u8 hash_prefix_md5[] = {
33 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, /* SEQUENCE (SEQUENCE (OID */
34 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, /* <algorithm>, */
35 0x05, 0x00, 0x04, 0x10 /* NULL), OCTET STRING <hash>) */
36};
37
38static const u8 hash_prefix_sha1[] = {
39 0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
40 0x2b, 0x0e, 0x03, 0x02, 0x1a,
41 0x05, 0x00, 0x04, 0x14
42};
43
44static const u8 hash_prefix_rmd160[] = {
45 0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
46 0x2b, 0x24, 0x03, 0x02, 0x01,
47 0x05, 0x00, 0x04, 0x14
48};
49
50static const u8 hash_prefix_sha224[] = {
51 0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
52 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
53 0x05, 0x00, 0x04, 0x1c
54};
55
56static const u8 hash_prefix_sha256[] = {
57 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
58 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
59 0x05, 0x00, 0x04, 0x20
60};
61
62static const u8 hash_prefix_sha384[] = {
63 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
64 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
65 0x05, 0x00, 0x04, 0x30
66};
67
68static const u8 hash_prefix_sha512[] = {
69 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
70 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
71 0x05, 0x00, 0x04, 0x40
72};
73
74static const u8 hash_prefix_sha3_256[] = {
75 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
76 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x08,
77 0x05, 0x00, 0x04, 0x20
78};
79
80static const u8 hash_prefix_sha3_384[] = {
81 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
82 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x09,
83 0x05, 0x00, 0x04, 0x30
84};
85
86static const u8 hash_prefix_sha3_512[] = {
87 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
88 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x0a,
89 0x05, 0x00, 0x04, 0x40
90};
91
92static const struct hash_prefix {
93 const char *name;
94 const u8 *data;
95 size_t size;
96} hash_prefixes[] = {
97#define _(X) { #X, hash_prefix_##X, sizeof(hash_prefix_##X) }
98 _(none),
99 _(md5),
100 _(sha1),
101 _(rmd160),
102 _(sha256),
103 _(sha384),
104 _(sha512),
105 _(sha224),
106#undef _
107#define _(X) { "sha3-" #X, hash_prefix_sha3_##X, sizeof(hash_prefix_sha3_##X) }
108 _(256),
109 _(384),
110 _(512),
111#undef _
112 { NULL }
113};
114
115static const struct hash_prefix *rsassa_pkcs1_find_hash_prefix(const char *name)
116{
117 const struct hash_prefix *p;
118
119 for (p = hash_prefixes; p->name; p++)
120 if (strcmp(name, p->name) == 0)
121 return p;
122 return NULL;
123}
124
125static bool rsassa_pkcs1_invalid_hash_len(unsigned int len,
126 const struct hash_prefix *p)
127{
128 /*
129 * Legacy protocols such as TLS 1.1 or earlier and IKE version 1
130 * do not prepend a Full Hash Prefix to the hash. In that case,
131 * the size of the Full Hash Prefix is zero.
132 */
133 if (p->data == hash_prefix_none)
134 return false;
135
136 /*
137 * The final byte of the Full Hash Prefix encodes the hash length.
138 *
139 * This needs to be revisited should hash algorithms with more than
140 * 1016 bits (127 bytes * 8) ever be added. The length would then
141 * be encoded into more than one byte by ASN.1.
142 */
143 static_assert(HASH_MAX_DIGESTSIZE <= 127);
144
145 return len != p->data[p->size - 1];
146}
147
148struct rsassa_pkcs1_ctx {
149 struct crypto_akcipher *child;
150 unsigned int key_size;
151};
152
153struct rsassa_pkcs1_inst_ctx {
154 struct crypto_akcipher_spawn spawn;
155 const struct hash_prefix *hash_prefix;
156};
157
158static int rsassa_pkcs1_sign(struct crypto_sig *tfm,
159 const void *src, unsigned int slen,
160 void *dst, unsigned int dlen)
161{
162 struct sig_instance *inst = sig_alg_instance(tfm);
163 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
164 const struct hash_prefix *hash_prefix = ictx->hash_prefix;
165 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
166 unsigned int pad_len;
167 unsigned int ps_end;
168 unsigned int len;
169 u8 *in_buf;
170 int err;
171
172 if (!ctx->key_size)
173 return -EINVAL;
174
175 if (dlen < ctx->key_size)
176 return -EOVERFLOW;
177
178 if (rsassa_pkcs1_invalid_hash_len(len: slen, p: hash_prefix))
179 return -EINVAL;
180
181 if (slen + hash_prefix->size > ctx->key_size - 11)
182 return -EOVERFLOW;
183
184 pad_len = ctx->key_size - slen - hash_prefix->size - 1;
185
186 /* RFC 8017 sec 8.2.1 step 1 - EMSA-PKCS1-v1_5 encoding generation */
187 in_buf = dst;
188 memmove(dest: in_buf + pad_len + hash_prefix->size, src, count: slen);
189 memcpy(to: in_buf + pad_len, from: hash_prefix->data, len: hash_prefix->size);
190
191 ps_end = pad_len - 1;
192 in_buf[0] = 0x01;
193 memset(s: in_buf + 1, c: 0xff, n: ps_end - 1);
194 in_buf[ps_end] = 0x00;
195
196
197 /* RFC 8017 sec 8.2.1 step 2 - RSA signature */
198 err = crypto_akcipher_sync_decrypt(tfm: ctx->child, src: in_buf,
199 slen: ctx->key_size - 1, dst: in_buf,
200 dlen: ctx->key_size);
201 if (err < 0)
202 return err;
203
204 len = err;
205 pad_len = ctx->key_size - len;
206
207 /* Four billion to one */
208 if (unlikely(pad_len)) {
209 memmove(dest: dst + pad_len, src: dst, count: len);
210 memset(s: dst, c: 0, n: pad_len);
211 }
212
213 return ctx->key_size;
214}
215
216static int rsassa_pkcs1_verify(struct crypto_sig *tfm,
217 const void *src, unsigned int slen,
218 const void *digest, unsigned int dlen)
219{
220 struct sig_instance *inst = sig_alg_instance(tfm);
221 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
222 const struct hash_prefix *hash_prefix = ictx->hash_prefix;
223 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
224 unsigned int child_reqsize = crypto_akcipher_reqsize(tfm: ctx->child);
225 struct akcipher_request *child_req __free(kfree_sensitive) = NULL;
226 struct crypto_wait cwait;
227 struct scatterlist sg;
228 unsigned int dst_len;
229 unsigned int pos;
230 u8 *out_buf;
231 int err;
232
233 /* RFC 8017 sec 8.2.2 step 1 - length checking */
234 if (!ctx->key_size ||
235 slen != ctx->key_size ||
236 rsassa_pkcs1_invalid_hash_len(len: dlen, p: hash_prefix))
237 return -EINVAL;
238
239 /* RFC 8017 sec 8.2.2 step 2 - RSA verification */
240 child_req = kmalloc(sizeof(*child_req) + child_reqsize + ctx->key_size,
241 GFP_KERNEL);
242 if (!child_req)
243 return -ENOMEM;
244
245 out_buf = (u8 *)(child_req + 1) + child_reqsize;
246 memcpy(to: out_buf, from: src, len: slen);
247
248 crypto_init_wait(wait: &cwait);
249 sg_init_one(&sg, out_buf, slen);
250 akcipher_request_set_tfm(req: child_req, tfm: ctx->child);
251 akcipher_request_set_crypt(req: child_req, src: &sg, dst: &sg, src_len: slen, dst_len: slen);
252 akcipher_request_set_callback(req: child_req, CRYPTO_TFM_REQ_MAY_SLEEP,
253 cmpl: crypto_req_done, data: &cwait);
254
255 err = crypto_akcipher_encrypt(req: child_req);
256 err = crypto_wait_req(err, wait: &cwait);
257 if (err)
258 return err;
259
260 /* RFC 8017 sec 8.2.2 step 3 - EMSA-PKCS1-v1_5 encoding verification */
261 dst_len = child_req->dst_len;
262 if (dst_len < ctx->key_size - 1)
263 return -EINVAL;
264
265 if (dst_len == ctx->key_size) {
266 if (out_buf[0] != 0x00)
267 /* Encrypted value had no leading 0 byte */
268 return -EINVAL;
269
270 dst_len--;
271 out_buf++;
272 }
273
274 if (out_buf[0] != 0x01)
275 return -EBADMSG;
276
277 for (pos = 1; pos < dst_len; pos++)
278 if (out_buf[pos] != 0xff)
279 break;
280
281 if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00)
282 return -EBADMSG;
283 pos++;
284
285 if (hash_prefix->size > dst_len - pos)
286 return -EBADMSG;
287 if (crypto_memneq(a: out_buf + pos, b: hash_prefix->data, size: hash_prefix->size))
288 return -EBADMSG;
289 pos += hash_prefix->size;
290
291 /* RFC 8017 sec 8.2.2 step 4 - comparison of digest with out_buf */
292 if (dlen != dst_len - pos)
293 return -EKEYREJECTED;
294 if (memcmp(digest, out_buf + pos, dlen) != 0)
295 return -EKEYREJECTED;
296
297 return 0;
298}
299
300static unsigned int rsassa_pkcs1_key_size(struct crypto_sig *tfm)
301{
302 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
303
304 return ctx->key_size * BITS_PER_BYTE;
305}
306
307static int rsassa_pkcs1_set_pub_key(struct crypto_sig *tfm,
308 const void *key, unsigned int keylen)
309{
310 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
311
312 return rsa_set_key(child: ctx->child, key_size: &ctx->key_size, RSA_PUB, key, keylen);
313}
314
315static int rsassa_pkcs1_set_priv_key(struct crypto_sig *tfm,
316 const void *key, unsigned int keylen)
317{
318 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
319
320 return rsa_set_key(child: ctx->child, key_size: &ctx->key_size, RSA_PRIV, key, keylen);
321}
322
323static int rsassa_pkcs1_init_tfm(struct crypto_sig *tfm)
324{
325 struct sig_instance *inst = sig_alg_instance(tfm);
326 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
327 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
328 struct crypto_akcipher *child_tfm;
329
330 child_tfm = crypto_spawn_akcipher(spawn: &ictx->spawn);
331 if (IS_ERR(ptr: child_tfm))
332 return PTR_ERR(ptr: child_tfm);
333
334 ctx->child = child_tfm;
335
336 return 0;
337}
338
339static void rsassa_pkcs1_exit_tfm(struct crypto_sig *tfm)
340{
341 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
342
343 crypto_free_akcipher(tfm: ctx->child);
344}
345
346static void rsassa_pkcs1_free(struct sig_instance *inst)
347{
348 struct rsassa_pkcs1_inst_ctx *ctx = sig_instance_ctx(inst);
349 struct crypto_akcipher_spawn *spawn = &ctx->spawn;
350
351 crypto_drop_akcipher(spawn);
352 kfree(objp: inst);
353}
354
355static int rsassa_pkcs1_create(struct crypto_template *tmpl, struct rtattr **tb)
356{
357 struct rsassa_pkcs1_inst_ctx *ctx;
358 struct akcipher_alg *rsa_alg;
359 struct sig_instance *inst;
360 const char *hash_name;
361 u32 mask;
362 int err;
363
364 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, mask_ret: &mask);
365 if (err)
366 return err;
367
368 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
369 if (!inst)
370 return -ENOMEM;
371
372 ctx = sig_instance_ctx(inst);
373
374 err = crypto_grab_akcipher(spawn: &ctx->spawn, inst: sig_crypto_instance(inst),
375 name: crypto_attr_alg_name(rta: tb[1]), type: 0, mask);
376 if (err)
377 goto err_free_inst;
378
379 rsa_alg = crypto_spawn_akcipher_alg(spawn: &ctx->spawn);
380
381 if (strcmp(rsa_alg->base.cra_name, "rsa") != 0) {
382 err = -EINVAL;
383 goto err_free_inst;
384 }
385
386 hash_name = crypto_attr_alg_name(rta: tb[2]);
387 if (IS_ERR(ptr: hash_name)) {
388 err = PTR_ERR(ptr: hash_name);
389 goto err_free_inst;
390 }
391
392 ctx->hash_prefix = rsassa_pkcs1_find_hash_prefix(name: hash_name);
393 if (!ctx->hash_prefix) {
394 err = -EINVAL;
395 goto err_free_inst;
396 }
397
398 err = -ENAMETOOLONG;
399 if (snprintf(buf: inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
400 fmt: "pkcs1(%s,%s)", rsa_alg->base.cra_name,
401 hash_name) >= CRYPTO_MAX_ALG_NAME)
402 goto err_free_inst;
403
404 if (snprintf(buf: inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
405 fmt: "pkcs1(%s,%s)", rsa_alg->base.cra_driver_name,
406 hash_name) >= CRYPTO_MAX_ALG_NAME)
407 goto err_free_inst;
408
409 inst->alg.base.cra_priority = rsa_alg->base.cra_priority;
410 inst->alg.base.cra_ctxsize = sizeof(struct rsassa_pkcs1_ctx);
411
412 inst->alg.init = rsassa_pkcs1_init_tfm;
413 inst->alg.exit = rsassa_pkcs1_exit_tfm;
414
415 inst->alg.sign = rsassa_pkcs1_sign;
416 inst->alg.verify = rsassa_pkcs1_verify;
417 inst->alg.key_size = rsassa_pkcs1_key_size;
418 inst->alg.set_pub_key = rsassa_pkcs1_set_pub_key;
419 inst->alg.set_priv_key = rsassa_pkcs1_set_priv_key;
420
421 inst->free = rsassa_pkcs1_free;
422
423 err = sig_register_instance(tmpl, inst);
424 if (err) {
425err_free_inst:
426 rsassa_pkcs1_free(inst);
427 }
428 return err;
429}
430
431struct crypto_template rsassa_pkcs1_tmpl = {
432 .name = "pkcs1",
433 .create = rsassa_pkcs1_create,
434 .module = THIS_MODULE,
435};
436
437MODULE_ALIAS_CRYPTO("pkcs1");
438