xref: /linux/crypto/asymmetric_keys/public_key.c (revision 6e7fd890f1d6ac83805409e9c346240de2705584) 
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 <crypto/akcipher.h>
12 #include <crypto/public_key.h>
13 #include <crypto/sig.h>
14 #include <keys/asymmetric-subtype.h>
15 #include <linux/asn1.h>
16 #include <linux/err.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/seq_file.h>
20 #include <linux/slab.h>
21 #include <linux/string.h>
22 
23 MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
24 MODULE_AUTHOR("Red Hat, Inc.");
25 MODULE_LICENSE("GPL");
26 
27 /*
28  * Provide a part of a description of the key for /proc/keys.
29  */
30 static void public_key_describe(const struct key *asymmetric_key,
31 				struct seq_file *m)
32 {
33 	struct public_key *key = asymmetric_key->payload.data[asym_crypto];
34 
35 	if (key)
36 		seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
37 }
38 
39 /*
40  * Destroy a public key algorithm key.
41  */
42 void public_key_free(struct public_key *key)
43 {
44 	if (key) {
45 		kfree_sensitive(key->key);
46 		kfree(key->params);
47 		kfree(key);
48 	}
49 }
50 EXPORT_SYMBOL_GPL(public_key_free);
51 
52 /*
53  * Destroy a public key algorithm key.
54  */
55 static void public_key_destroy(void *payload0, void *payload3)
56 {
57 	public_key_free(payload0);
58 	public_key_signature_free(payload3);
59 }
60 
61 /*
62  * Given a public_key, and an encoding and hash_algo to be used for signing
63  * and/or verification with that key, determine the name of the corresponding
64  * akcipher algorithm.  Also check that encoding and hash_algo are allowed.
65  */
66 static int
67 software_key_determine_akcipher(const struct public_key *pkey,
68 				const char *encoding, const char *hash_algo,
69 				char alg_name[CRYPTO_MAX_ALG_NAME], bool *sig,
70 				enum kernel_pkey_operation op)
71 {
72 	int n;
73 
74 	*sig = true;
75 
76 	if (!encoding)
77 		return -EINVAL;
78 
79 	if (strcmp(pkey->pkey_algo, "rsa") == 0) {
80 		/*
81 		 * RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2].
82 		 */
83 		if (strcmp(encoding, "pkcs1") == 0) {
84 			*sig = op == kernel_pkey_sign ||
85 			       op == kernel_pkey_verify;
86 			if (!hash_algo) {
87 				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
88 					     "pkcs1pad(%s)",
89 					     pkey->pkey_algo);
90 			} else {
91 				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
92 					     "pkcs1pad(%s,%s)",
93 					     pkey->pkey_algo, hash_algo);
94 			}
95 			return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
96 		}
97 		if (strcmp(encoding, "raw") != 0)
98 			return -EINVAL;
99 		/*
100 		 * Raw RSA cannot differentiate between different hash
101 		 * algorithms.
102 		 */
103 		if (hash_algo)
104 			return -EINVAL;
105 		*sig = false;
106 	} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
107 		if (strcmp(encoding, "x962") != 0)
108 			return -EINVAL;
109 		/*
110 		 * ECDSA signatures are taken over a raw hash, so they don't
111 		 * differentiate between different hash algorithms.  That means
112 		 * that the verifier should hard-code a specific hash algorithm.
113 		 * Unfortunately, in practice ECDSA is used with multiple SHAs,
114 		 * so we have to allow all of them and not just one.
115 		 */
116 		if (!hash_algo)
117 			return -EINVAL;
118 		if (strcmp(hash_algo, "sha1") != 0 &&
119 		    strcmp(hash_algo, "sha224") != 0 &&
120 		    strcmp(hash_algo, "sha256") != 0 &&
121 		    strcmp(hash_algo, "sha384") != 0 &&
122 		    strcmp(hash_algo, "sha512") != 0 &&
123 		    strcmp(hash_algo, "sha3-256") != 0 &&
124 		    strcmp(hash_algo, "sha3-384") != 0 &&
125 		    strcmp(hash_algo, "sha3-512") != 0)
126 			return -EINVAL;
127 	} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
128 		if (strcmp(encoding, "raw") != 0)
129 			return -EINVAL;
130 		if (!hash_algo)
131 			return -EINVAL;
132 		if (strcmp(hash_algo, "streebog256") != 0 &&
133 		    strcmp(hash_algo, "streebog512") != 0)
134 			return -EINVAL;
135 	} else {
136 		/* Unknown public key algorithm */
137 		return -ENOPKG;
138 	}
139 	if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
140 		return -EINVAL;
141 	return 0;
142 }
143 
144 static u8 *pkey_pack_u32(u8 *dst, u32 val)
145 {
146 	memcpy(dst, &val, sizeof(val));
147 	return dst + sizeof(val);
148 }
149 
150 /*
151  * Query information about a key.
152  */
153 static int software_key_query(const struct kernel_pkey_params *params,
154 			      struct kernel_pkey_query *info)
155 {
156 	struct crypto_akcipher *tfm;
157 	struct public_key *pkey = params->key->payload.data[asym_crypto];
158 	char alg_name[CRYPTO_MAX_ALG_NAME];
159 	struct crypto_sig *sig;
160 	u8 *key, *ptr;
161 	int ret, len;
162 	bool issig;
163 
164 	ret = software_key_determine_akcipher(pkey, params->encoding,
165 					      params->hash_algo, alg_name,
166 					      &issig, kernel_pkey_sign);
167 	if (ret < 0)
168 		return ret;
169 
170 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
171 		      GFP_KERNEL);
172 	if (!key)
173 		return -ENOMEM;
174 
175 	memcpy(key, pkey->key, pkey->keylen);
176 	ptr = key + pkey->keylen;
177 	ptr = pkey_pack_u32(ptr, pkey->algo);
178 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
179 	memcpy(ptr, pkey->params, pkey->paramlen);
180 
181 	if (issig) {
182 		sig = crypto_alloc_sig(alg_name, 0, 0);
183 		if (IS_ERR(sig)) {
184 			ret = PTR_ERR(sig);
185 			goto error_free_key;
186 		}
187 
188 		if (pkey->key_is_private)
189 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
190 		else
191 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
192 		if (ret < 0)
193 			goto error_free_tfm;
194 
195 		len = crypto_sig_maxsize(sig);
196 
197 		info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
198 		if (pkey->key_is_private)
199 			info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
200 
201 		if (strcmp(params->encoding, "pkcs1") == 0) {
202 			info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
203 			if (pkey->key_is_private)
204 				info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
205 		}
206 	} else {
207 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
208 		if (IS_ERR(tfm)) {
209 			ret = PTR_ERR(tfm);
210 			goto error_free_key;
211 		}
212 
213 		if (pkey->key_is_private)
214 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
215 		else
216 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
217 		if (ret < 0)
218 			goto error_free_tfm;
219 
220 		len = crypto_akcipher_maxsize(tfm);
221 
222 		info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
223 		if (pkey->key_is_private)
224 			info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
225 	}
226 
227 	info->key_size = len * 8;
228 
229 	if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
230 		int slen = len;
231 		/*
232 		 * ECDSA key sizes are much smaller than RSA, and thus could
233 		 * operate on (hashed) inputs that are larger than key size.
234 		 * For example SHA384-hashed input used with secp256r1
235 		 * based keys.  Set max_data_size to be at least as large as
236 		 * the largest supported hash size (SHA512)
237 		 */
238 		info->max_data_size = 64;
239 
240 		/*
241 		 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
242 		 * which is actually 2 'key_size'-bit integers encoded in
243 		 * ASN.1.  Account for the ASN.1 encoding overhead here.
244 		 *
245 		 * NIST P192/256/384 may prepend a '0' to a coordinate to
246 		 * indicate a positive integer. NIST P521 never needs it.
247 		 */
248 		if (strcmp(pkey->pkey_algo, "ecdsa-nist-p521") != 0)
249 			slen += 1;
250 		/* Length of encoding the x & y coordinates */
251 		slen = 2 * (slen + 2);
252 		/*
253 		 * If coordinate encoding takes at least 128 bytes then an
254 		 * additional byte for length encoding is needed.
255 		 */
256 		info->max_sig_size = 1 + (slen >= 128) + 1 + slen;
257 	} else {
258 		info->max_data_size = len;
259 		info->max_sig_size = len;
260 	}
261 
262 	info->max_enc_size = len;
263 	info->max_dec_size = len;
264 
265 	ret = 0;
266 
267 error_free_tfm:
268 	if (issig)
269 		crypto_free_sig(sig);
270 	else
271 		crypto_free_akcipher(tfm);
272 error_free_key:
273 	kfree_sensitive(key);
274 	pr_devel("<==%s() = %d\n", __func__, ret);
275 	return ret;
276 }
277 
278 /*
279  * Do encryption, decryption and signing ops.
280  */
281 static int software_key_eds_op(struct kernel_pkey_params *params,
282 			       const void *in, void *out)
283 {
284 	const struct public_key *pkey = params->key->payload.data[asym_crypto];
285 	char alg_name[CRYPTO_MAX_ALG_NAME];
286 	struct crypto_akcipher *tfm;
287 	struct crypto_sig *sig;
288 	char *key, *ptr;
289 	bool issig;
290 	int ksz;
291 	int ret;
292 
293 	pr_devel("==>%s()\n", __func__);
294 
295 	ret = software_key_determine_akcipher(pkey, params->encoding,
296 					      params->hash_algo, alg_name,
297 					      &issig, params->op);
298 	if (ret < 0)
299 		return ret;
300 
301 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
302 		      GFP_KERNEL);
303 	if (!key)
304 		return -ENOMEM;
305 
306 	memcpy(key, pkey->key, pkey->keylen);
307 	ptr = key + pkey->keylen;
308 	ptr = pkey_pack_u32(ptr, pkey->algo);
309 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
310 	memcpy(ptr, pkey->params, pkey->paramlen);
311 
312 	if (issig) {
313 		sig = crypto_alloc_sig(alg_name, 0, 0);
314 		if (IS_ERR(sig)) {
315 			ret = PTR_ERR(sig);
316 			goto error_free_key;
317 		}
318 
319 		if (pkey->key_is_private)
320 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
321 		else
322 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
323 		if (ret)
324 			goto error_free_tfm;
325 
326 		ksz = crypto_sig_maxsize(sig);
327 	} else {
328 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
329 		if (IS_ERR(tfm)) {
330 			ret = PTR_ERR(tfm);
331 			goto error_free_key;
332 		}
333 
334 		if (pkey->key_is_private)
335 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
336 		else
337 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
338 		if (ret)
339 			goto error_free_tfm;
340 
341 		ksz = crypto_akcipher_maxsize(tfm);
342 	}
343 
344 	ret = -EINVAL;
345 
346 	/* Perform the encryption calculation. */
347 	switch (params->op) {
348 	case kernel_pkey_encrypt:
349 		if (issig)
350 			break;
351 		ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
352 						   out, params->out_len);
353 		break;
354 	case kernel_pkey_decrypt:
355 		if (issig)
356 			break;
357 		ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
358 						   out, params->out_len);
359 		break;
360 	case kernel_pkey_sign:
361 		if (!issig)
362 			break;
363 		ret = crypto_sig_sign(sig, in, params->in_len,
364 				      out, params->out_len);
365 		break;
366 	default:
367 		BUG();
368 	}
369 
370 	if (ret == 0)
371 		ret = ksz;
372 
373 error_free_tfm:
374 	if (issig)
375 		crypto_free_sig(sig);
376 	else
377 		crypto_free_akcipher(tfm);
378 error_free_key:
379 	kfree_sensitive(key);
380 	pr_devel("<==%s() = %d\n", __func__, ret);
381 	return ret;
382 }
383 
384 /*
385  * Verify a signature using a public key.
386  */
387 int public_key_verify_signature(const struct public_key *pkey,
388 				const struct public_key_signature *sig)
389 {
390 	char alg_name[CRYPTO_MAX_ALG_NAME];
391 	struct crypto_sig *tfm;
392 	char *key, *ptr;
393 	bool issig;
394 	int ret;
395 
396 	pr_devel("==>%s()\n", __func__);
397 
398 	BUG_ON(!pkey);
399 	BUG_ON(!sig);
400 	BUG_ON(!sig->s);
401 
402 	/*
403 	 * If the signature specifies a public key algorithm, it *must* match
404 	 * the key's actual public key algorithm.
405 	 *
406 	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
407 	 * keys do.  So the strings can mismatch slightly in that case:
408 	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
409 	 */
410 	if (sig->pkey_algo) {
411 		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
412 		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
413 		     strcmp(sig->pkey_algo, "ecdsa") != 0))
414 			return -EKEYREJECTED;
415 	}
416 
417 	ret = software_key_determine_akcipher(pkey, sig->encoding,
418 					      sig->hash_algo, alg_name,
419 					      &issig, kernel_pkey_verify);
420 	if (ret < 0)
421 		return ret;
422 
423 	tfm = crypto_alloc_sig(alg_name, 0, 0);
424 	if (IS_ERR(tfm))
425 		return PTR_ERR(tfm);
426 
427 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
428 		      GFP_KERNEL);
429 	if (!key) {
430 		ret = -ENOMEM;
431 		goto error_free_tfm;
432 	}
433 
434 	memcpy(key, pkey->key, pkey->keylen);
435 	ptr = key + pkey->keylen;
436 	ptr = pkey_pack_u32(ptr, pkey->algo);
437 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
438 	memcpy(ptr, pkey->params, pkey->paramlen);
439 
440 	if (pkey->key_is_private)
441 		ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
442 	else
443 		ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
444 	if (ret)
445 		goto error_free_key;
446 
447 	ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
448 				sig->digest, sig->digest_size);
449 
450 error_free_key:
451 	kfree_sensitive(key);
452 error_free_tfm:
453 	crypto_free_sig(tfm);
454 	pr_devel("<==%s() = %d\n", __func__, ret);
455 	if (WARN_ON_ONCE(ret > 0))
456 		ret = -EINVAL;
457 	return ret;
458 }
459 EXPORT_SYMBOL_GPL(public_key_verify_signature);
460 
461 static int public_key_verify_signature_2(const struct key *key,
462 					 const struct public_key_signature *sig)
463 {
464 	const struct public_key *pk = key->payload.data[asym_crypto];
465 	return public_key_verify_signature(pk, sig);
466 }
467 
468 /*
469  * Public key algorithm asymmetric key subtype
470  */
471 struct asymmetric_key_subtype public_key_subtype = {
472 	.owner			= THIS_MODULE,
473 	.name			= "public_key",
474 	.name_len		= sizeof("public_key") - 1,
475 	.describe		= public_key_describe,
476 	.destroy		= public_key_destroy,
477 	.query			= software_key_query,
478 	.eds_op			= software_key_eds_op,
479 	.verify_signature	= public_key_verify_signature_2,
480 };
481 EXPORT_SYMBOL_GPL(public_key_subtype);
482