xref: /linux/crypto/asymmetric_keys/public_key.c (revision be239684b18e1cdcafcf8c7face4a2f562c745ad) 
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, "sha224") != 0 &&
119 		    strcmp(hash_algo, "sha256") != 0 &&
120 		    strcmp(hash_algo, "sha384") != 0 &&
121 		    strcmp(hash_algo, "sha512") != 0 &&
122 		    strcmp(hash_algo, "sha3-256") != 0 &&
123 		    strcmp(hash_algo, "sha3-384") != 0 &&
124 		    strcmp(hash_algo, "sha3-512") != 0)
125 			return -EINVAL;
126 	} else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
127 		if (strcmp(encoding, "raw") != 0)
128 			return -EINVAL;
129 		if (!hash_algo)
130 			return -EINVAL;
131 		if (strcmp(hash_algo, "sm3") != 0)
132 			return -EINVAL;
133 	} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
134 		if (strcmp(encoding, "raw") != 0)
135 			return -EINVAL;
136 		if (!hash_algo)
137 			return -EINVAL;
138 		if (strcmp(hash_algo, "streebog256") != 0 &&
139 		    strcmp(hash_algo, "streebog512") != 0)
140 			return -EINVAL;
141 	} else {
142 		/* Unknown public key algorithm */
143 		return -ENOPKG;
144 	}
145 	if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
146 		return -EINVAL;
147 	return 0;
148 }
149 
150 static u8 *pkey_pack_u32(u8 *dst, u32 val)
151 {
152 	memcpy(dst, &val, sizeof(val));
153 	return dst + sizeof(val);
154 }
155 
156 /*
157  * Query information about a key.
158  */
159 static int software_key_query(const struct kernel_pkey_params *params,
160 			      struct kernel_pkey_query *info)
161 {
162 	struct crypto_akcipher *tfm;
163 	struct public_key *pkey = params->key->payload.data[asym_crypto];
164 	char alg_name[CRYPTO_MAX_ALG_NAME];
165 	struct crypto_sig *sig;
166 	u8 *key, *ptr;
167 	int ret, len;
168 	bool issig;
169 
170 	ret = software_key_determine_akcipher(pkey, params->encoding,
171 					      params->hash_algo, alg_name,
172 					      &issig, kernel_pkey_sign);
173 	if (ret < 0)
174 		return ret;
175 
176 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
177 		      GFP_KERNEL);
178 	if (!key)
179 		return -ENOMEM;
180 
181 	memcpy(key, pkey->key, pkey->keylen);
182 	ptr = key + pkey->keylen;
183 	ptr = pkey_pack_u32(ptr, pkey->algo);
184 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
185 	memcpy(ptr, pkey->params, pkey->paramlen);
186 
187 	if (issig) {
188 		sig = crypto_alloc_sig(alg_name, 0, 0);
189 		if (IS_ERR(sig)) {
190 			ret = PTR_ERR(sig);
191 			goto error_free_key;
192 		}
193 
194 		if (pkey->key_is_private)
195 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
196 		else
197 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
198 		if (ret < 0)
199 			goto error_free_tfm;
200 
201 		len = crypto_sig_maxsize(sig);
202 
203 		info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
204 		if (pkey->key_is_private)
205 			info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
206 
207 		if (strcmp(params->encoding, "pkcs1") == 0) {
208 			info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
209 			if (pkey->key_is_private)
210 				info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
211 		}
212 	} else {
213 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
214 		if (IS_ERR(tfm)) {
215 			ret = PTR_ERR(tfm);
216 			goto error_free_key;
217 		}
218 
219 		if (pkey->key_is_private)
220 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
221 		else
222 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
223 		if (ret < 0)
224 			goto error_free_tfm;
225 
226 		len = crypto_akcipher_maxsize(tfm);
227 
228 		info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
229 		if (pkey->key_is_private)
230 			info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
231 	}
232 
233 	info->key_size = len * 8;
234 
235 	if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
236 		/*
237 		 * ECDSA key sizes are much smaller than RSA, and thus could
238 		 * operate on (hashed) inputs that are larger than key size.
239 		 * For example SHA384-hashed input used with secp256r1
240 		 * based keys.  Set max_data_size to be at least as large as
241 		 * the largest supported hash size (SHA512)
242 		 */
243 		info->max_data_size = 64;
244 
245 		/*
246 		 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
247 		 * which is actually 2 'key_size'-bit integers encoded in
248 		 * ASN.1.  Account for the ASN.1 encoding overhead here.
249 		 */
250 		info->max_sig_size = 2 * (len + 3) + 2;
251 	} else {
252 		info->max_data_size = len;
253 		info->max_sig_size = len;
254 	}
255 
256 	info->max_enc_size = len;
257 	info->max_dec_size = len;
258 
259 	ret = 0;
260 
261 error_free_tfm:
262 	if (issig)
263 		crypto_free_sig(sig);
264 	else
265 		crypto_free_akcipher(tfm);
266 error_free_key:
267 	kfree_sensitive(key);
268 	pr_devel("<==%s() = %d\n", __func__, ret);
269 	return ret;
270 }
271 
272 /*
273  * Do encryption, decryption and signing ops.
274  */
275 static int software_key_eds_op(struct kernel_pkey_params *params,
276 			       const void *in, void *out)
277 {
278 	const struct public_key *pkey = params->key->payload.data[asym_crypto];
279 	char alg_name[CRYPTO_MAX_ALG_NAME];
280 	struct crypto_akcipher *tfm;
281 	struct crypto_sig *sig;
282 	char *key, *ptr;
283 	bool issig;
284 	int ksz;
285 	int ret;
286 
287 	pr_devel("==>%s()\n", __func__);
288 
289 	ret = software_key_determine_akcipher(pkey, params->encoding,
290 					      params->hash_algo, alg_name,
291 					      &issig, params->op);
292 	if (ret < 0)
293 		return ret;
294 
295 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
296 		      GFP_KERNEL);
297 	if (!key)
298 		return -ENOMEM;
299 
300 	memcpy(key, pkey->key, pkey->keylen);
301 	ptr = key + pkey->keylen;
302 	ptr = pkey_pack_u32(ptr, pkey->algo);
303 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
304 	memcpy(ptr, pkey->params, pkey->paramlen);
305 
306 	if (issig) {
307 		sig = crypto_alloc_sig(alg_name, 0, 0);
308 		if (IS_ERR(sig)) {
309 			ret = PTR_ERR(sig);
310 			goto error_free_key;
311 		}
312 
313 		if (pkey->key_is_private)
314 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
315 		else
316 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
317 		if (ret)
318 			goto error_free_tfm;
319 
320 		ksz = crypto_sig_maxsize(sig);
321 	} else {
322 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
323 		if (IS_ERR(tfm)) {
324 			ret = PTR_ERR(tfm);
325 			goto error_free_key;
326 		}
327 
328 		if (pkey->key_is_private)
329 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
330 		else
331 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
332 		if (ret)
333 			goto error_free_tfm;
334 
335 		ksz = crypto_akcipher_maxsize(tfm);
336 	}
337 
338 	ret = -EINVAL;
339 
340 	/* Perform the encryption calculation. */
341 	switch (params->op) {
342 	case kernel_pkey_encrypt:
343 		if (issig)
344 			break;
345 		ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
346 						   out, params->out_len);
347 		break;
348 	case kernel_pkey_decrypt:
349 		if (issig)
350 			break;
351 		ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
352 						   out, params->out_len);
353 		break;
354 	case kernel_pkey_sign:
355 		if (!issig)
356 			break;
357 		ret = crypto_sig_sign(sig, in, params->in_len,
358 				      out, params->out_len);
359 		break;
360 	default:
361 		BUG();
362 	}
363 
364 	if (ret == 0)
365 		ret = ksz;
366 
367 error_free_tfm:
368 	if (issig)
369 		crypto_free_sig(sig);
370 	else
371 		crypto_free_akcipher(tfm);
372 error_free_key:
373 	kfree_sensitive(key);
374 	pr_devel("<==%s() = %d\n", __func__, ret);
375 	return ret;
376 }
377 
378 /*
379  * Verify a signature using a public key.
380  */
381 int public_key_verify_signature(const struct public_key *pkey,
382 				const struct public_key_signature *sig)
383 {
384 	char alg_name[CRYPTO_MAX_ALG_NAME];
385 	struct crypto_sig *tfm;
386 	char *key, *ptr;
387 	bool issig;
388 	int ret;
389 
390 	pr_devel("==>%s()\n", __func__);
391 
392 	BUG_ON(!pkey);
393 	BUG_ON(!sig);
394 	BUG_ON(!sig->s);
395 
396 	/*
397 	 * If the signature specifies a public key algorithm, it *must* match
398 	 * the key's actual public key algorithm.
399 	 *
400 	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
401 	 * keys do.  So the strings can mismatch slightly in that case:
402 	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
403 	 */
404 	if (sig->pkey_algo) {
405 		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
406 		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
407 		     strcmp(sig->pkey_algo, "ecdsa") != 0))
408 			return -EKEYREJECTED;
409 	}
410 
411 	ret = software_key_determine_akcipher(pkey, sig->encoding,
412 					      sig->hash_algo, alg_name,
413 					      &issig, kernel_pkey_verify);
414 	if (ret < 0)
415 		return ret;
416 
417 	tfm = crypto_alloc_sig(alg_name, 0, 0);
418 	if (IS_ERR(tfm))
419 		return PTR_ERR(tfm);
420 
421 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
422 		      GFP_KERNEL);
423 	if (!key) {
424 		ret = -ENOMEM;
425 		goto error_free_tfm;
426 	}
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_sig_set_privkey(tfm, key, pkey->keylen);
436 	else
437 		ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
438 	if (ret)
439 		goto error_free_key;
440 
441 	ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
442 				sig->digest, sig->digest_size);
443 
444 error_free_key:
445 	kfree_sensitive(key);
446 error_free_tfm:
447 	crypto_free_sig(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 
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