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 info->max_data_size = len;
190 info->max_sig_size = len;
191 info->max_enc_size = len;
192 info->max_dec_size = len;
193 info->supported_ops = (KEYCTL_SUPPORTS_ENCRYPT |
194 KEYCTL_SUPPORTS_VERIFY);
195 if (pkey->key_is_private)
196 info->supported_ops |= (KEYCTL_SUPPORTS_DECRYPT |
197 KEYCTL_SUPPORTS_SIGN);
198 ret = 0;
199
200 error_free_key:
201 kfree(key);
202 error_free_tfm:
203 crypto_free_akcipher(tfm);
204 pr_devel("<==%s() = %d\n", __func__, ret);
205 return ret;
206 }
207
208 /*
209 * Do encryption, decryption and signing ops.
210 */
software_key_eds_op(struct kernel_pkey_params * params,const void * in,void * out)211 static int software_key_eds_op(struct kernel_pkey_params *params,
212 const void *in, void *out)
213 {
214 const struct public_key *pkey = params->key->payload.data[asym_crypto];
215 struct akcipher_request *req;
216 struct crypto_akcipher *tfm;
217 struct crypto_wait cwait;
218 struct scatterlist in_sg, out_sg;
219 char alg_name[CRYPTO_MAX_ALG_NAME];
220 char *key, *ptr;
221 int ret;
222
223 pr_devel("==>%s()\n", __func__);
224
225 ret = software_key_determine_akcipher(pkey, params->encoding,
226 params->hash_algo, alg_name);
227 if (ret < 0)
228 return ret;
229
230 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
231 if (IS_ERR(tfm))
232 return PTR_ERR(tfm);
233
234 ret = -ENOMEM;
235 req = akcipher_request_alloc(tfm, GFP_KERNEL);
236 if (!req)
237 goto error_free_tfm;
238
239 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
240 GFP_KERNEL);
241 if (!key)
242 goto error_free_req;
243
244 memcpy(key, pkey->key, pkey->keylen);
245 ptr = key + pkey->keylen;
246 ptr = pkey_pack_u32(ptr, pkey->algo);
247 ptr = pkey_pack_u32(ptr, pkey->paramlen);
248 memcpy(ptr, pkey->params, pkey->paramlen);
249
250 if (pkey->key_is_private)
251 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
252 else
253 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
254 if (ret)
255 goto error_free_key;
256
257 sg_init_one(&in_sg, in, params->in_len);
258 sg_init_one(&out_sg, out, params->out_len);
259 akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
260 params->out_len);
261 crypto_init_wait(&cwait);
262 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
263 CRYPTO_TFM_REQ_MAY_SLEEP,
264 crypto_req_done, &cwait);
265
266 /* Perform the encryption calculation. */
267 switch (params->op) {
268 case kernel_pkey_encrypt:
269 ret = crypto_akcipher_encrypt(req);
270 break;
271 case kernel_pkey_decrypt:
272 ret = crypto_akcipher_decrypt(req);
273 break;
274 case kernel_pkey_sign:
275 ret = crypto_akcipher_sign(req);
276 break;
277 default:
278 BUG();
279 }
280
281 ret = crypto_wait_req(ret, &cwait);
282 if (ret == 0)
283 ret = req->dst_len;
284
285 error_free_key:
286 kfree(key);
287 error_free_req:
288 akcipher_request_free(req);
289 error_free_tfm:
290 crypto_free_akcipher(tfm);
291 pr_devel("<==%s() = %d\n", __func__, ret);
292 return ret;
293 }
294
295 #if IS_REACHABLE(CONFIG_CRYPTO_SM2)
cert_sig_digest_update(const struct public_key_signature * sig,struct crypto_akcipher * tfm_pkey)296 static int cert_sig_digest_update(const struct public_key_signature *sig,
297 struct crypto_akcipher *tfm_pkey)
298 {
299 struct crypto_shash *tfm;
300 struct shash_desc *desc;
301 size_t desc_size;
302 unsigned char dgst[SM3_DIGEST_SIZE];
303 int ret;
304
305 BUG_ON(!sig->data);
306
307 /* SM2 signatures always use the SM3 hash algorithm */
308 if (!sig->hash_algo || strcmp(sig->hash_algo, "sm3") != 0)
309 return -EINVAL;
310
311 ret = sm2_compute_z_digest(tfm_pkey, SM2_DEFAULT_USERID,
312 SM2_DEFAULT_USERID_LEN, dgst);
313 if (ret)
314 return ret;
315
316 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
317 if (IS_ERR(tfm))
318 return PTR_ERR(tfm);
319
320 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
321 desc = kzalloc(desc_size, GFP_KERNEL);
322 if (!desc) {
323 ret = -ENOMEM;
324 goto error_free_tfm;
325 }
326
327 desc->tfm = tfm;
328
329 ret = crypto_shash_init(desc);
330 if (ret < 0)
331 goto error_free_desc;
332
333 ret = crypto_shash_update(desc, dgst, SM3_DIGEST_SIZE);
334 if (ret < 0)
335 goto error_free_desc;
336
337 ret = crypto_shash_finup(desc, sig->data, sig->data_size, sig->digest);
338
339 error_free_desc:
340 kfree(desc);
341 error_free_tfm:
342 crypto_free_shash(tfm);
343 return ret;
344 }
345 #else
cert_sig_digest_update(const struct public_key_signature * sig,struct crypto_akcipher * tfm_pkey)346 static inline int cert_sig_digest_update(
347 const struct public_key_signature *sig,
348 struct crypto_akcipher *tfm_pkey)
349 {
350 return -ENOTSUPP;
351 }
352 #endif /* ! IS_REACHABLE(CONFIG_CRYPTO_SM2) */
353
354 /*
355 * Verify a signature using a public key.
356 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)357 int public_key_verify_signature(const struct public_key *pkey,
358 const struct public_key_signature *sig)
359 {
360 struct crypto_wait cwait;
361 struct crypto_akcipher *tfm;
362 struct akcipher_request *req;
363 struct scatterlist src_sg;
364 char alg_name[CRYPTO_MAX_ALG_NAME];
365 char *buf, *ptr;
366 size_t buf_len;
367 int ret;
368
369 pr_devel("==>%s()\n", __func__);
370
371 BUG_ON(!pkey);
372 BUG_ON(!sig);
373 BUG_ON(!sig->s);
374
375 /*
376 * If the signature specifies a public key algorithm, it *must* match
377 * the key's actual public key algorithm.
378 *
379 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
380 * keys do. So the strings can mismatch slightly in that case:
381 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
382 */
383 if (sig->pkey_algo) {
384 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
385 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
386 strcmp(sig->pkey_algo, "ecdsa") != 0))
387 return -EKEYREJECTED;
388 }
389
390 ret = software_key_determine_akcipher(pkey, sig->encoding,
391 sig->hash_algo, alg_name);
392 if (ret < 0)
393 return ret;
394
395 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
396 if (IS_ERR(tfm))
397 return PTR_ERR(tfm);
398
399 ret = -ENOMEM;
400 req = akcipher_request_alloc(tfm, GFP_KERNEL);
401 if (!req)
402 goto error_free_tfm;
403
404 buf_len = max_t(size_t, pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
405 sig->s_size + sig->digest_size);
406
407 buf = kmalloc(buf_len, GFP_KERNEL);
408 if (!buf)
409 goto error_free_req;
410
411 memcpy(buf, pkey->key, pkey->keylen);
412 ptr = buf + pkey->keylen;
413 ptr = pkey_pack_u32(ptr, pkey->algo);
414 ptr = pkey_pack_u32(ptr, pkey->paramlen);
415 memcpy(ptr, pkey->params, pkey->paramlen);
416
417 if (pkey->key_is_private)
418 ret = crypto_akcipher_set_priv_key(tfm, buf, pkey->keylen);
419 else
420 ret = crypto_akcipher_set_pub_key(tfm, buf, pkey->keylen);
421 if (ret)
422 goto error_free_buf;
423
424 if (strcmp(pkey->pkey_algo, "sm2") == 0 && sig->data_size) {
425 ret = cert_sig_digest_update(sig, tfm);
426 if (ret)
427 goto error_free_buf;
428 }
429
430 memcpy(buf, sig->s, sig->s_size);
431 memcpy(buf + sig->s_size, sig->digest, sig->digest_size);
432
433 sg_init_one(&src_sg, buf, sig->s_size + sig->digest_size);
434 akcipher_request_set_crypt(req, &src_sg, NULL, sig->s_size,
435 sig->digest_size);
436 crypto_init_wait(&cwait);
437 akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
438 CRYPTO_TFM_REQ_MAY_SLEEP,
439 crypto_req_done, &cwait);
440 ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
441
442 error_free_buf:
443 kfree(buf);
444 error_free_req:
445 akcipher_request_free(req);
446 error_free_tfm:
447 crypto_free_akcipher(tfm);
448 pr_devel("<==%s() = %d\n", __func__, ret);
449 if (WARN_ON_ONCE(ret > 0))
450 ret = -EINVAL;
451 return ret;
452 }
453 EXPORT_SYMBOL_GPL(public_key_verify_signature);
454
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)455 static int public_key_verify_signature_2(const struct key *key,
456 const struct public_key_signature *sig)
457 {
458 const struct public_key *pk = key->payload.data[asym_crypto];
459 return public_key_verify_signature(pk, sig);
460 }
461
462 /*
463 * Public key algorithm asymmetric key subtype
464 */
465 struct asymmetric_key_subtype public_key_subtype = {
466 .owner = THIS_MODULE,
467 .name = "public_key",
468 .name_len = sizeof("public_key") - 1,
469 .describe = public_key_describe,
470 .destroy = public_key_destroy,
471 .query = software_key_query,
472 .eds_op = software_key_eds_op,
473 .verify_signature = public_key_verify_signature_2,
474 };
475 EXPORT_SYMBOL_GPL(public_key_subtype);
476