summaryrefslogtreecommitdiffstats
path: root/crypto/asymmetric_keys/public_key.c
blob: eca5671ad3f2288eefe2a07b31d50b1a5728a8ed (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
// SPDX-License-Identifier: GPL-2.0-or-later
/* In-software asymmetric public-key crypto subtype
 *
 * See Documentation/crypto/asymmetric-keys.rst
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) "PKEY: "fmt
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>
#include <linux/asn1.h>
#include <keys/asymmetric-subtype.h>
#include <crypto/public_key.h>
#include <crypto/akcipher.h>
#include <crypto/sm2.h>
#include <crypto/sm3_base.h>

MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");

/*
 * Provide a part of a description of the key for /proc/keys.
 */
static void public_key_describe(const struct key *asymmetric_key,
				struct seq_file *m)
{
	struct public_key *key = asymmetric_key->payload.data[asym_crypto];

	if (key)
		seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
}

/*
 * Destroy a public key algorithm key.
 */
void public_key_free(struct public_key *key)
{
	if (key) {
		kfree(key->key);
		kfree(key->params);
		kfree(key);
	}
}
EXPORT_SYMBOL_GPL(public_key_free);

/*
 * Destroy a public key algorithm key.
 */
static void public_key_destroy(void *payload0, void *payload3)
{
	public_key_free(payload0);
	public_key_signature_free(payload3);
}

/*
 * Given a public_key, and an encoding and hash_algo to be used for signing
 * and/or verification with that key, determine the name of the corresponding
 * akcipher algorithm.  Also check that encoding and hash_algo are allowed.
 */
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])
{
	int n;

	if (!encoding)
		return -EINVAL;

	if (strcmp(pkey->pkey_algo, "rsa") == 0) {
		/*
		 * RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2].
		 */
		if (strcmp(encoding, "pkcs1") == 0) {
			if (!hash_algo)
				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
					     "pkcs1pad(%s)",
					     pkey->pkey_algo);
			else
				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
					     "pkcs1pad(%s,%s)",
					     pkey->pkey_algo, hash_algo);
			return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
		}
		if (strcmp(encoding, "raw") != 0)
			return -EINVAL;
		/*
		 * Raw RSA cannot differentiate between different hash
		 * algorithms.
		 */
		if (hash_algo)
			return -EINVAL;
	} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
		if (strcmp(encoding, "x962") != 0)
			return -EINVAL;
		/*
		 * ECDSA signatures are taken over a raw hash, so they don't
		 * differentiate between different hash algorithms.  That means
		 * that the verifier should hard-code a specific hash algorithm.
		 * Unfortunately, in practice ECDSA is used with multiple SHAs,
		 * so we have to allow all of them and not just one.
		 */
		if (!hash_algo)
			return -EINVAL;
		if (strcmp(hash_algo, "sha1") != 0 &&
		    strcmp(hash_algo, "sha224") != 0 &&
		    strcmp(hash_algo, "sha256") != 0 &&
		    strcmp(hash_algo, "sha384") != 0 &&
		    strcmp(hash_algo, "sha512") != 0)
			return -EINVAL;
	} else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
		if (strcmp(encoding, "raw") != 0)
			return -EINVAL;
		if (!hash_algo)
			return -EINVAL;
		if (strcmp(hash_algo, "sm3") != 0)
			return -EINVAL;
	} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
		if (strcmp(encoding, "raw") != 0)
			return -EINVAL;
		if (!hash_algo)
			return -EINVAL;
		if (strcmp(hash_algo, "streebog256") != 0 &&
		    strcmp(hash_algo, "streebog512") != 0)
			return -EINVAL;
	} else {
		/* Unknown public key algorithm */
		return -ENOPKG;
	}
	if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
		return -EINVAL;
	return 0;
}

static u8 *pkey_pack_u32(u8 *dst, u32 val)
{
	memcpy(dst, &val, sizeof(val));
	return dst + sizeof(val);
}

/*
 * Query information about a key.
 */
static int software_key_query(const struct kernel_pkey_params *params,
			      struct kernel_pkey_query *info)
{
	struct crypto_akcipher *tfm;
	struct public_key *pkey = params->key->payload.data[asym_crypto];
	char alg_name[CRYPTO_MAX_ALG_NAME];
	u8 *key, *ptr;
	int ret, len;

	ret = software_key_determine_akcipher(pkey, params->encoding,
					      params->hash_algo, alg_name);
	if (ret < 0)
		return ret;

	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	ret = -ENOMEM;
	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
		      GFP_KERNEL);
	if (!key)
		goto error_free_tfm;
	memcpy(key, pkey->key, pkey->keylen);
	ptr = key + pkey->keylen;
	ptr = pkey_pack_u32(ptr, pkey->algo);
	ptr = pkey_pack_u32(ptr, pkey->paramlen);
	memcpy(ptr, pkey->params, pkey->paramlen);

	if (pkey->key_is_private)
		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
	else
		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
	if (ret < 0)
		goto error_free_key;

	len = crypto_akcipher_maxsize(tfm);
	info->key_size = len * 8;

	if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
		/*
		 * ECDSA key sizes are much smaller than RSA, and thus could
		 * operate on (hashed) inputs that are larger than key size.
		 * For example SHA384-hashed input used with secp256r1
		 * based keys.  Set max_data_size to be at least as large as
		 * the largest supported hash size (SHA512)
		 */
		info->max_data_size = 64;

		/*
		 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
		 * which is actually 2 'key_size'-bit integers encoded in
		 * ASN.1.  Account for the ASN.1 encoding overhead here.
		 */
		info->max_sig_size = 2 * (len + 3) + 2;
	} else {
		info->max_data_size = len;
		info->max_sig_size = len;
	}

	info->max_enc_size = len;
	info->max_dec_size = len;
	info->supported_ops = (KEYCTL_SUPPORTS_ENCRYPT |
			       KEYCTL_SUPPORTS_VERIFY);
	if (pkey->key_is_private)
		info->supported_ops |= (KEYCTL_SUPPORTS_DECRYPT |
					KEYCTL_SUPPORTS_SIGN);
	ret = 0;

error_free_key:
	kfree(key);
error_free_tfm:
	crypto_free_akcipher(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
}

/*
 * Do encryption, decryption and signing ops.
 */
static int software_key_eds_op(struct kernel_pkey_params *params,
			       const void *in, void *out)
{
	const struct public_key *pkey = params->key->payload.data[asym_crypto];
	struct akcipher_request *req;
	struct crypto_akcipher *tfm;
	struct crypto_wait cwait;
	struct scatterlist in_sg, out_sg;
	char alg_name[CRYPTO_MAX_ALG_NAME];
	char *key, *ptr;
	int ret;

	pr_devel("==>%s()\n", __func__);

	ret = software_key_determine_akcipher(pkey, params->encoding,
					      params->hash_algo, alg_name);
	if (ret < 0)
		return ret;

	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	ret = -ENOMEM;
	req = akcipher_request_alloc(tfm, GFP_KERNEL);
	if (!req)
		goto error_free_tfm;

	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
		      GFP_KERNEL);
	if (!key)
		goto error_free_req;

	memcpy(key, pkey->key, pkey->keylen);
	ptr = key + pkey->keylen;
	ptr = pkey_pack_u32(ptr, pkey->algo);
	ptr = pkey_pack_u32(ptr, pkey->paramlen);
	memcpy(ptr, pkey->params, pkey->paramlen);

	if (pkey->key_is_private)
		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
	else
		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
	if (ret)
		goto error_free_key;

	sg_init_one(&in_sg, in, params->in_len);
	sg_init_one(&out_sg, out, params->out_len);
	akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
				   params->out_len);
	crypto_init_wait(&cwait);
	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
				      CRYPTO_TFM_REQ_MAY_SLEEP,
				      crypto_req_done, &cwait);

	/* Perform the encryption calculation. */
	switch (params->op) {
	case kernel_pkey_encrypt:
		ret = crypto_akcipher_encrypt(req);
		break;
	case kernel_pkey_decrypt:
		ret = crypto_akcipher_decrypt(req);
		break;
	case kernel_pkey_sign:
		ret = crypto_akcipher_sign(req);
		break;
	default:
		BUG();
	}

	ret = crypto_wait_req(ret, &cwait);
	if (ret == 0)
		ret = req->dst_len;

error_free_key:
	kfree(key);
error_free_req:
	akcipher_request_free(req);
error_free_tfm:
	crypto_free_akcipher(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
}

#if IS_REACHABLE(CONFIG_CRYPTO_SM2)
static int cert_sig_digest_update(const struct public_key_signature *sig,
				  struct crypto_akcipher *tfm_pkey)
{
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t desc_size;
	unsigned char dgst[SM3_DIGEST_SIZE];
	int ret;

	BUG_ON(!sig->data);

	/* SM2 signatures always use the SM3 hash algorithm */
	if (!sig->hash_algo || strcmp(sig->hash_algo, "sm3") != 0)
		return -EINVAL;

	ret = sm2_compute_z_digest(tfm_pkey, SM2_DEFAULT_USERID,
					SM2_DEFAULT_USERID_LEN, dgst);
	if (ret)
		return ret;

	tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
	desc = kzalloc(desc_size, GFP_KERNEL);
	if (!desc) {
		ret = -ENOMEM;
		goto error_free_tfm;
	}

	desc->tfm = tfm;

	ret = crypto_shash_init(desc);
	if (ret < 0)
		goto error_free_desc;

	ret = crypto_shash_update(desc, dgst, SM3_DIGEST_SIZE);
	if (ret < 0)
		goto error_free_desc;

	ret = crypto_shash_finup(desc, sig->data, sig->data_size, sig->digest);

error_free_desc:
	kfree(desc);
error_free_tfm:
	crypto_free_shash(tfm);
	return ret;
}
#else
static inline int cert_sig_digest_update(
	const struct public_key_signature *sig,
	struct crypto_akcipher *tfm_pkey)
{
	return -ENOTSUPP;
}
#endif /* ! IS_REACHABLE(CONFIG_CRYPTO_SM2) */

/*
 * Verify a signature using a public key.
 */
int public_key_verify_signature(const struct public_key *pkey,
				const struct public_key_signature *sig)
{
	struct crypto_wait cwait;
	struct crypto_akcipher *tfm;
	struct akcipher_request *req;
	struct scatterlist src_sg[2];
	char alg_name[CRYPTO_MAX_ALG_NAME];
	char *key, *ptr;
	int ret;

	pr_devel("==>%s()\n", __func__);

	BUG_ON(!pkey);
	BUG_ON(!sig);
	BUG_ON(!sig->s);

	/*
	 * If the signature specifies a public key algorithm, it *must* match
	 * the key's actual public key algorithm.
	 *
	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
	 * keys do.  So the strings can mismatch slightly in that case:
	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
	 */
	if (sig->pkey_algo) {
		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
		     strcmp(sig->pkey_algo, "ecdsa") != 0))
			return -EKEYREJECTED;
	}

	ret = software_key_determine_akcipher(pkey, sig->encoding,
					      sig->hash_algo, alg_name);
	if (ret < 0)
		return ret;

	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	ret = -ENOMEM;
	req = akcipher_request_alloc(tfm, GFP_KERNEL);
	if (!req)
		goto error_free_tfm;

	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
		      GFP_KERNEL);
	if (!key)
		goto error_free_req;

	memcpy(key, pkey->key, pkey->keylen);
	ptr = key + pkey->keylen;
	ptr = pkey_pack_u32(ptr, pkey->algo);
	ptr = pkey_pack_u32(ptr, pkey->paramlen);
	memcpy(ptr, pkey->params, pkey->paramlen);

	if (pkey->key_is_private)
		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
	else
		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
	if (ret)
		goto error_free_key;

	if (strcmp(pkey->pkey_algo, "sm2") == 0 && sig->data_size) {
		ret = cert_sig_digest_update(sig, tfm);
		if (ret)
			goto error_free_key;
	}

	sg_init_table(src_sg, 2);
	sg_set_buf(&src_sg[0], sig->s, sig->s_size);
	sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
	akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
				   sig->digest_size);
	crypto_init_wait(&cwait);
	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
				      CRYPTO_TFM_REQ_MAY_SLEEP,
				      crypto_req_done, &cwait);
	ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);

error_free_key:
	kfree(key);
error_free_req:
	akcipher_request_free(req);
error_free_tfm:
	crypto_free_akcipher(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	if (WARN_ON_ONCE(ret > 0))
		ret = -EINVAL;
	return ret;
}
EXPORT_SYMBOL_GPL(public_key_verify_signature);

static int public_key_verify_signature_2(const struct key *key,
					 const struct public_key_signature *sig)
{
	const struct public_key *pk = key->payload.data[asym_crypto];
	return public_key_verify_signature(pk, sig);
}

/*
 * Public key algorithm asymmetric key subtype
 */
struct asymmetric_key_subtype public_key_subtype = {
	.owner			= THIS_MODULE,
	.name			= "public_key",
	.name_len		= sizeof("public_key") - 1,
	.describe		= public_key_describe,
	.destroy		= public_key_destroy,
	.query			= software_key_query,
	.eds_op			= software_key_eds_op,
	.verify_signature	= public_key_verify_signature_2,
};
EXPORT_SYMBOL_GPL(public_key_subtype);