1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* In-software asymmetric public-key crypto subtype
3 *
4 * See Documentation/crypto/asymmetric-keys.rst
5 *
6 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
7 * Written by David Howells (dhowells@redhat.com)
8 */
9
10 #define pr_fmt(fmt) "PKEY: "fmt
11 #include <linux/module.h>
12 #include <linux/export.h>
13 #include <linux/kernel.h>
14 #include <linux/slab.h>
15 #include <linux/seq_file.h>
16 #include <linux/scatterlist.h>
17 #include <linux/asn1.h>
18 #include <keys/asymmetric-subtype.h>
19 #include <crypto/public_key.h>
20 #include <crypto/akcipher.h>
21 #include <crypto/sm2.h>
22 #include <crypto/sm3_base.h>
23
24 MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
25 MODULE_AUTHOR("Red Hat, Inc.");
26 MODULE_LICENSE("GPL");
27
28 /*
29 * Provide a part of a description of the key for /proc/keys.
30 */
public_key_describe(const struct key * asymmetric_key,struct seq_file * m)31 static void public_key_describe(const struct key *asymmetric_key,
32 struct seq_file *m)
33 {
34 struct public_key *key = asymmetric_key->payload.data[asym_crypto];
35
36 if (key)
37 seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
38 }
39
40 /*
41 * Destroy a public key algorithm key.
42 */
public_key_free(struct public_key * key)43 void public_key_free(struct public_key *key)
44 {
45 if (key) {
46 kfree(key->key);
47 kfree(key->params);
48 kfree(key);
49 }
50 }
51 EXPORT_SYMBOL_GPL(public_key_free);
52
53 /*
54 * Destroy a public key algorithm key.
55 */
public_key_destroy(void * payload0,void * payload3)56 static void public_key_destroy(void *payload0, void *payload3)
57 {
58 public_key_free(payload0);
59 public_key_signature_free(payload3);
60 }
61
62 /*
63 * Given a public_key, and an encoding and hash_algo to be used for signing
64 * and/or verification with that key, determine the name of the corresponding
65 * akcipher algorithm. Also check that encoding and hash_algo are allowed.
66 */
67 static int
software_key_determine_akcipher(const struct public_key * pkey,const char * encoding,const char * hash_algo,char alg_name[CRYPTO_MAX_ALG_NAME])68 software_key_determine_akcipher(const struct public_key *pkey,
69 const char *encoding, const char *hash_algo,
70 char alg_name[CRYPTO_MAX_ALG_NAME])
71 {
72 int n;
73
74 if (!encoding)
75 return -EINVAL;
76
77 if (strcmp(pkey->pkey_algo, "rsa") == 0) {
78 /*
79 * RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2].
80 */
81 if (strcmp(encoding, "pkcs1") == 0) {
82 if (!hash_algo)
83 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
84 "pkcs1pad(%s)",
85 pkey->pkey_algo);
86 else
87 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
88 "pkcs1pad(%s,%s)",
89 pkey->pkey_algo, hash_algo);
90 return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
91 }
92 if (strcmp(encoding, "raw") != 0)
93 return -EINVAL;
94 /*
95 * Raw RSA cannot differentiate between different hash
96 * algorithms.
97 */
98 if (hash_algo)
99 return -EINVAL;
100 } else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
101 if (strcmp(encoding, "x962") != 0)
102 return -EINVAL;
103 /*
104 * ECDSA signatures are taken over a raw hash, so they don't
105 * differentiate between different hash algorithms. That means
106 * that the verifier should hard-code a specific hash algorithm.
107 * Unfortunately, in practice ECDSA is used with multiple SHAs,
108 * so we have to allow all of them and not just one.
109 */
110 if (!hash_algo)
111 return -EINVAL;
112 if (strcmp(hash_algo, "sha1") != 0 &&
113 strcmp(hash_algo, "sha224") != 0 &&
114 strcmp(hash_algo, "sha256") != 0 &&
115 strcmp(hash_algo, "sha384") != 0 &&
116 strcmp(hash_algo, "sha512") != 0)
117 return -EINVAL;
118 } else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
119 if (strcmp(encoding, "raw") != 0)
120 return -EINVAL;
121 if (!hash_algo)
122 return -EINVAL;
123 if (strcmp(hash_algo, "sm3") != 0)
124 return -EINVAL;
125 } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
126 if (strcmp(encoding, "raw") != 0)
127 return -EINVAL;
128 if (!hash_algo)
129 return -EINVAL;
130 if (strcmp(hash_algo, "streebog256") != 0 &&
131 strcmp(hash_algo, "streebog512") != 0)
132 return -EINVAL;
133 } else {
134 /* Unknown public key algorithm */
135 return -ENOPKG;
136 }
137 if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
138 return -EINVAL;
139 return 0;
140 }
141
pkey_pack_u32(u8 * dst,u32 val)142 static u8 *pkey_pack_u32(u8 *dst, u32 val)
143 {
144 memcpy(dst, &val, sizeof(val));
145 return dst + sizeof(val);
146 }
147
148 /*
149 * Query information about a key.
150 */
software_key_query(const struct kernel_pkey_params * params,struct kernel_pkey_query * info)151 static int software_key_query(const struct kernel_pkey_params *params,
152 struct kernel_pkey_query *info)
153 {
154 struct crypto_akcipher *tfm;
155 struct public_key *pkey = params->key->payload.data[asym_crypto];
156 char alg_name[CRYPTO_MAX_ALG_NAME];
157 u8 *key, *ptr;
158 int ret, len;
159
160 ret = software_key_determine_akcipher(pkey, params->encoding,
161 params->hash_algo, alg_name);
162 if (ret < 0)
163 return ret;
164
165 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
166 if (IS_ERR(tfm))
167 return PTR_ERR(tfm);
168
169 ret = -ENOMEM;
170 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
171 GFP_KERNEL);
172 if (!key)
173 goto error_free_tfm;
174 memcpy(key, pkey->key, pkey->keylen);
175 ptr = key + pkey->keylen;
176 ptr = pkey_pack_u32(ptr, pkey->algo);
177 ptr = pkey_pack_u32(ptr, pkey->paramlen);
178 memcpy(ptr, pkey->params, pkey->paramlen);
179
180 if (pkey->key_is_private)
181 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
182 else
183 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
184 if (ret < 0)
185 goto error_free_key;
186
187 len = crypto_akcipher_maxsize(tfm);
188 info->key_size = len * 8;
189
190 if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
191 /*
192 * ECDSA key sizes are much smaller than RSA, and thus could
193 * operate on (hashed) inputs that are larger than key size.
194 * For example SHA384-hashed input used with secp256r1
195 * based keys. Set max_data_size to be at least as large as
196 * the largest supported hash size (SHA512)
197 */
198 info->max_data_size = 64;
199
200 /*
201 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
202 * which is actually 2 'key_size'-bit integers encoded in
203 * ASN.1. Account for the ASN.1 encoding overhead here.
204 */
205 info->max_sig_size = 2 * (len + 3) + 2;
206 } else {
207 info->max_data_size = len;
208 info->max_sig_size = len;
209 }
210
211 info->max_enc_size = len;
212 info->max_dec_size = len;
213 info->supported_ops = (KEYCTL_SUPPORTS_ENCRYPT |
214 KEYCTL_SUPPORTS_VERIFY);
215 if (pkey->key_is_private)
216 info->supported_ops |= (KEYCTL_SUPPORTS_DECRYPT |
217 KEYCTL_SUPPORTS_SIGN);
218 ret = 0;
219
220 error_free_key:
221 kfree(key);
222 error_free_tfm:
223 crypto_free_akcipher(tfm);
224 pr_devel("<==%s() = %d\n", __func__, ret);
225 return ret;
226 }
227
228 /*
229 * Do encryption, decryption and signing ops.
230 */
software_key_eds_op(struct kernel_pkey_params * params,const void * in,void * out)231 static int software_key_eds_op(struct kernel_pkey_params *params,
232 const void *in, void *out)
233 {
234 const struct public_key *pkey = params->key->payload.data[asym_crypto];
235 struct akcipher_request *req;
236 struct crypto_akcipher *tfm;
237 struct crypto_wait cwait;
238 struct scatterlist in_sg, out_sg;
239 char alg_name[CRYPTO_MAX_ALG_NAME];
240 char *key, *ptr;
241 int ret;
242
243 pr_devel("==>%s()\n", __func__);
244
245 ret = software_key_determine_akcipher(pkey, params->encoding,
246 params->hash_algo, alg_name);
247 if (ret < 0)
248 return ret;
249
250 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
251 if (IS_ERR(tfm))
252 return PTR_ERR(tfm);
253
254 ret = -ENOMEM;
255 req = akcipher_request_alloc(tfm, GFP_KERNEL);
256 if (!req)
257 goto error_free_tfm;
258
259 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
260 GFP_KERNEL);
261 if (!key)
262 goto error_free_req;
263
264 memcpy(key, pkey->key, pkey->keylen);
265 ptr = key + pkey->keylen;
266 ptr = pkey_pack_u32(ptr, pkey->algo);
267 ptr = pkey_pack_u32(ptr, pkey->paramlen);
268 memcpy(ptr, pkey->params, pkey->paramlen);
269
270 if (pkey->key_is_private)
271 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
272 else
273 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
274 if (ret)
275 goto error_free_key;
276
277 sg_init_one(&in_sg, in, params->in_len);
278 sg_init_one(&out_sg, out, params->out_len);
279 akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
280 params->out_len);
281 crypto_init_wait(&cwait);
282 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
283 CRYPTO_TFM_REQ_MAY_SLEEP,
284 crypto_req_done, &cwait);
285
286 /* Perform the encryption calculation. */
287 switch (params->op) {
288 case kernel_pkey_encrypt:
289 ret = crypto_akcipher_encrypt(req);
290 break;
291 case kernel_pkey_decrypt:
292 ret = crypto_akcipher_decrypt(req);
293 break;
294 case kernel_pkey_sign:
295 ret = crypto_akcipher_sign(req);
296 break;
297 default:
298 BUG();
299 }
300
301 ret = crypto_wait_req(ret, &cwait);
302 if (ret == 0)
303 ret = req->dst_len;
304
305 error_free_key:
306 kfree(key);
307 error_free_req:
308 akcipher_request_free(req);
309 error_free_tfm:
310 crypto_free_akcipher(tfm);
311 pr_devel("<==%s() = %d\n", __func__, ret);
312 return ret;
313 }
314
315 #if IS_REACHABLE(CONFIG_CRYPTO_SM2)
cert_sig_digest_update(const struct public_key_signature * sig,struct crypto_akcipher * tfm_pkey)316 static int cert_sig_digest_update(const struct public_key_signature *sig,
317 struct crypto_akcipher *tfm_pkey)
318 {
319 struct crypto_shash *tfm;
320 struct shash_desc *desc;
321 size_t desc_size;
322 unsigned char dgst[SM3_DIGEST_SIZE];
323 int ret;
324
325 BUG_ON(!sig->data);
326
327 /* SM2 signatures always use the SM3 hash algorithm */
328 if (!sig->hash_algo || strcmp(sig->hash_algo, "sm3") != 0)
329 return -EINVAL;
330
331 ret = sm2_compute_z_digest(tfm_pkey, SM2_DEFAULT_USERID,
332 SM2_DEFAULT_USERID_LEN, dgst);
333 if (ret)
334 return ret;
335
336 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
337 if (IS_ERR(tfm))
338 return PTR_ERR(tfm);
339
340 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
341 desc = kzalloc(desc_size, GFP_KERNEL);
342 if (!desc) {
343 ret = -ENOMEM;
344 goto error_free_tfm;
345 }
346
347 desc->tfm = tfm;
348
349 ret = crypto_shash_init(desc);
350 if (ret < 0)
351 goto error_free_desc;
352
353 ret = crypto_shash_update(desc, dgst, SM3_DIGEST_SIZE);
354 if (ret < 0)
355 goto error_free_desc;
356
357 ret = crypto_shash_finup(desc, sig->data, sig->data_size, sig->digest);
358
359 error_free_desc:
360 kfree(desc);
361 error_free_tfm:
362 crypto_free_shash(tfm);
363 return ret;
364 }
365 #else
cert_sig_digest_update(const struct public_key_signature * sig,struct crypto_akcipher * tfm_pkey)366 static inline int cert_sig_digest_update(
367 const struct public_key_signature *sig,
368 struct crypto_akcipher *tfm_pkey)
369 {
370 return -ENOTSUPP;
371 }
372 #endif /* ! IS_REACHABLE(CONFIG_CRYPTO_SM2) */
373
374 /*
375 * Verify a signature using a public key.
376 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)377 int public_key_verify_signature(const struct public_key *pkey,
378 const struct public_key_signature *sig)
379 {
380 struct crypto_wait cwait;
381 struct crypto_akcipher *tfm;
382 struct akcipher_request *req;
383 struct scatterlist src_sg[2];
384 char alg_name[CRYPTO_MAX_ALG_NAME];
385 char *key, *ptr;
386 int ret;
387
388 pr_devel("==>%s()\n", __func__);
389
390 BUG_ON(!pkey);
391 BUG_ON(!sig);
392 BUG_ON(!sig->s);
393
394 /*
395 * If the signature specifies a public key algorithm, it *must* match
396 * the key's actual public key algorithm.
397 *
398 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
399 * keys do. So the strings can mismatch slightly in that case:
400 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
401 */
402 if (sig->pkey_algo) {
403 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
404 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
405 strcmp(sig->pkey_algo, "ecdsa") != 0))
406 return -EKEYREJECTED;
407 }
408
409 ret = software_key_determine_akcipher(pkey, sig->encoding,
410 sig->hash_algo, alg_name);
411 if (ret < 0)
412 return ret;
413
414 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
415 if (IS_ERR(tfm))
416 return PTR_ERR(tfm);
417
418 ret = -ENOMEM;
419 req = akcipher_request_alloc(tfm, GFP_KERNEL);
420 if (!req)
421 goto error_free_tfm;
422
423 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
424 GFP_KERNEL);
425 if (!key)
426 goto error_free_req;
427
428 memcpy(key, pkey->key, pkey->keylen);
429 ptr = key + pkey->keylen;
430 ptr = pkey_pack_u32(ptr, pkey->algo);
431 ptr = pkey_pack_u32(ptr, pkey->paramlen);
432 memcpy(ptr, pkey->params, pkey->paramlen);
433
434 if (pkey->key_is_private)
435 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
436 else
437 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
438 if (ret)
439 goto error_free_key;
440
441 if (strcmp(pkey->pkey_algo, "sm2") == 0 && sig->data_size) {
442 ret = cert_sig_digest_update(sig, tfm);
443 if (ret)
444 goto error_free_key;
445 }
446
447 sg_init_table(src_sg, 2);
448 sg_set_buf(&src_sg[0], sig->s, sig->s_size);
449 sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
450 akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
451 sig->digest_size);
452 crypto_init_wait(&cwait);
453 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
454 CRYPTO_TFM_REQ_MAY_SLEEP,
455 crypto_req_done, &cwait);
456 ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
457
458 error_free_key:
459 kfree(key);
460 error_free_req:
461 akcipher_request_free(req);
462 error_free_tfm:
463 crypto_free_akcipher(tfm);
464 pr_devel("<==%s() = %d\n", __func__, ret);
465 if (WARN_ON_ONCE(ret > 0))
466 ret = -EINVAL;
467 return ret;
468 }
469 EXPORT_SYMBOL_GPL(public_key_verify_signature);
470
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)471 static int public_key_verify_signature_2(const struct key *key,
472 const struct public_key_signature *sig)
473 {
474 const struct public_key *pk = key->payload.data[asym_crypto];
475 return public_key_verify_signature(pk, sig);
476 }
477
478 /*
479 * Public key algorithm asymmetric key subtype
480 */
481 struct asymmetric_key_subtype public_key_subtype = {
482 .owner = THIS_MODULE,
483 .name = "public_key",
484 .name_len = sizeof("public_key") - 1,
485 .describe = public_key_describe,
486 .destroy = public_key_destroy,
487 .query = software_key_query,
488 .eds_op = software_key_eds_op,
489 .verify_signature = public_key_verify_signature_2,
490 };
491 EXPORT_SYMBOL_GPL(public_key_subtype);
492