xref: /linux/crypto/asymmetric_keys/public_key.c (revision 0a94608f0f7de9b1135ffea3546afe68eafef57f) 
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  */
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  */
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  */
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
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 
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  */
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  */
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)
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 	ret = sm2_compute_z_digest(tfm_pkey, SM2_DEFAULT_USERID,
308 					SM2_DEFAULT_USERID_LEN, dgst);
309 	if (ret)
310 		return ret;
311 
312 	tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
313 	if (IS_ERR(tfm))
314 		return PTR_ERR(tfm);
315 
316 	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
317 	desc = kzalloc(desc_size, GFP_KERNEL);
318 	if (!desc) {
319 		ret = -ENOMEM;
320 		goto error_free_tfm;
321 	}
322 
323 	desc->tfm = tfm;
324 
325 	ret = crypto_shash_init(desc);
326 	if (ret < 0)
327 		goto error_free_desc;
328 
329 	ret = crypto_shash_update(desc, dgst, SM3_DIGEST_SIZE);
330 	if (ret < 0)
331 		goto error_free_desc;
332 
333 	ret = crypto_shash_finup(desc, sig->data, sig->data_size, sig->digest);
334 
335 error_free_desc:
336 	kfree(desc);
337 error_free_tfm:
338 	crypto_free_shash(tfm);
339 	return ret;
340 }
341 #else
342 static inline int cert_sig_digest_update(
343 	const struct public_key_signature *sig,
344 	struct crypto_akcipher *tfm_pkey)
345 {
346 	return -ENOTSUPP;
347 }
348 #endif /* ! IS_REACHABLE(CONFIG_CRYPTO_SM2) */
349 
350 /*
351  * Verify a signature using a public key.
352  */
353 int public_key_verify_signature(const struct public_key *pkey,
354 				const struct public_key_signature *sig)
355 {
356 	struct crypto_wait cwait;
357 	struct crypto_akcipher *tfm;
358 	struct akcipher_request *req;
359 	struct scatterlist src_sg[2];
360 	char alg_name[CRYPTO_MAX_ALG_NAME];
361 	char *key, *ptr;
362 	int ret;
363 
364 	pr_devel("==>%s()\n", __func__);
365 
366 	BUG_ON(!pkey);
367 	BUG_ON(!sig);
368 	BUG_ON(!sig->s);
369 
370 	/*
371 	 * If the signature specifies a public key algorithm, it *must* match
372 	 * the key's actual public key algorithm.
373 	 *
374 	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
375 	 * keys do.  So the strings can mismatch slightly in that case:
376 	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
377 	 */
378 	if (sig->pkey_algo) {
379 		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
380 		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
381 		     strcmp(sig->pkey_algo, "ecdsa") != 0))
382 			return -EKEYREJECTED;
383 	}
384 
385 	ret = software_key_determine_akcipher(pkey, sig->encoding,
386 					      sig->hash_algo, alg_name);
387 	if (ret < 0)
388 		return ret;
389 
390 	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
391 	if (IS_ERR(tfm))
392 		return PTR_ERR(tfm);
393 
394 	ret = -ENOMEM;
395 	req = akcipher_request_alloc(tfm, GFP_KERNEL);
396 	if (!req)
397 		goto error_free_tfm;
398 
399 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
400 		      GFP_KERNEL);
401 	if (!key)
402 		goto error_free_req;
403 
404 	memcpy(key, pkey->key, pkey->keylen);
405 	ptr = key + pkey->keylen;
406 	ptr = pkey_pack_u32(ptr, pkey->algo);
407 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
408 	memcpy(ptr, pkey->params, pkey->paramlen);
409 
410 	if (pkey->key_is_private)
411 		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
412 	else
413 		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
414 	if (ret)
415 		goto error_free_key;
416 
417 	if (sig->pkey_algo && strcmp(sig->pkey_algo, "sm2") == 0 &&
418 	    sig->data_size) {
419 		ret = cert_sig_digest_update(sig, tfm);
420 		if (ret)
421 			goto error_free_key;
422 	}
423 
424 	sg_init_table(src_sg, 2);
425 	sg_set_buf(&src_sg[0], sig->s, sig->s_size);
426 	sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
427 	akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
428 				   sig->digest_size);
429 	crypto_init_wait(&cwait);
430 	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
431 				      CRYPTO_TFM_REQ_MAY_SLEEP,
432 				      crypto_req_done, &cwait);
433 	ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
434 
435 error_free_key:
436 	kfree(key);
437 error_free_req:
438 	akcipher_request_free(req);
439 error_free_tfm:
440 	crypto_free_akcipher(tfm);
441 	pr_devel("<==%s() = %d\n", __func__, ret);
442 	if (WARN_ON_ONCE(ret > 0))
443 		ret = -EINVAL;
444 	return ret;
445 }
446 EXPORT_SYMBOL_GPL(public_key_verify_signature);
447 
448 static int public_key_verify_signature_2(const struct key *key,
449 					 const struct public_key_signature *sig)
450 {
451 	const struct public_key *pk = key->payload.data[asym_crypto];
452 	return public_key_verify_signature(pk, sig);
453 }
454 
455 /*
456  * Public key algorithm asymmetric key subtype
457  */
458 struct asymmetric_key_subtype public_key_subtype = {
459 	.owner			= THIS_MODULE,
460 	.name			= "public_key",
461 	.name_len		= sizeof("public_key") - 1,
462 	.describe		= public_key_describe,
463 	.destroy		= public_key_destroy,
464 	.query			= software_key_query,
465 	.eds_op			= software_key_eds_op,
466 	.verify_signature	= public_key_verify_signature_2,
467 };
468 EXPORT_SYMBOL_GPL(public_key_subtype);
469