xref: /linux/crypto/asymmetric_keys/public_key.c (revision 6f7e6393d1ce636bb7ec77a7fe7b77458fddf701) 
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 (!*sig) {
87 				/*
88 				 * For encrypt/decrypt, hash_algo is not used
89 				 * but allowed to be set for historic reasons.
90 				 */
91 				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
92 					     "pkcs1pad(%s)",
93 					     pkey->pkey_algo);
94 			} else {
95 				if (!hash_algo)
96 					hash_algo = "none";
97 				n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
98 					     "pkcs1(%s,%s)",
99 					     pkey->pkey_algo, hash_algo);
100 			}
101 			return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
102 		}
103 		if (strcmp(encoding, "raw") != 0)
104 			return -EINVAL;
105 		/*
106 		 * Raw RSA cannot differentiate between different hash
107 		 * algorithms.
108 		 */
109 		if (hash_algo)
110 			return -EINVAL;
111 		*sig = false;
112 	} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
113 		if (strcmp(encoding, "x962") != 0 &&
114 		    strcmp(encoding, "p1363") != 0)
115 			return -EINVAL;
116 		/*
117 		 * ECDSA signatures are taken over a raw hash, so they don't
118 		 * differentiate between different hash algorithms.  That means
119 		 * that the verifier should hard-code a specific hash algorithm.
120 		 * Unfortunately, in practice ECDSA is used with multiple SHAs,
121 		 * so we have to allow all of them and not just one.
122 		 */
123 		if (!hash_algo)
124 			return -EINVAL;
125 		if (strcmp(hash_algo, "sha1") != 0 &&
126 		    strcmp(hash_algo, "sha224") != 0 &&
127 		    strcmp(hash_algo, "sha256") != 0 &&
128 		    strcmp(hash_algo, "sha384") != 0 &&
129 		    strcmp(hash_algo, "sha512") != 0 &&
130 		    strcmp(hash_algo, "sha3-256") != 0 &&
131 		    strcmp(hash_algo, "sha3-384") != 0 &&
132 		    strcmp(hash_algo, "sha3-512") != 0)
133 			return -EINVAL;
134 		n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME, "%s(%s)",
135 			     encoding, pkey->pkey_algo);
136 		return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
137 	} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
138 		if (strcmp(encoding, "raw") != 0)
139 			return -EINVAL;
140 		if (!hash_algo)
141 			return -EINVAL;
142 		if (strcmp(hash_algo, "streebog256") != 0 &&
143 		    strcmp(hash_algo, "streebog512") != 0)
144 			return -EINVAL;
145 	} else if (strcmp(pkey->pkey_algo, "mldsa44") == 0 ||
146 		   strcmp(pkey->pkey_algo, "mldsa65") == 0 ||
147 		   strcmp(pkey->pkey_algo, "mldsa87") == 0) {
148 		if (strcmp(encoding, "raw") != 0)
149 			return -EINVAL;
150 		if (!hash_algo)
151 			return -EINVAL;
152 		if (strcmp(hash_algo, "none") != 0 &&
153 		    strcmp(hash_algo, "sha512") != 0)
154 			return -EINVAL;
155 	} else {
156 		/* Unknown public key algorithm */
157 		return -ENOPKG;
158 	}
159 	if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
160 		return -EINVAL;
161 	return 0;
162 }
163 
164 static u8 *pkey_pack_u32(u8 *dst, u32 val)
165 {
166 	memcpy(dst, &val, sizeof(val));
167 	return dst + sizeof(val);
168 }
169 
170 /*
171  * Query information about a key.
172  */
173 static int software_key_query(const struct kernel_pkey_params *params,
174 			      struct kernel_pkey_query *info)
175 {
176 	struct public_key *pkey = params->key->payload.data[asym_crypto];
177 	char alg_name[CRYPTO_MAX_ALG_NAME];
178 	u8 *key, *ptr;
179 	int ret, len;
180 	bool issig;
181 
182 	ret = software_key_determine_akcipher(pkey, params->encoding,
183 					      params->hash_algo, alg_name,
184 					      &issig, kernel_pkey_sign);
185 	if (ret < 0)
186 		return ret;
187 
188 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
189 		      GFP_KERNEL);
190 	if (!key)
191 		return -ENOMEM;
192 
193 	memcpy(key, pkey->key, pkey->keylen);
194 	ptr = key + pkey->keylen;
195 	ptr = pkey_pack_u32(ptr, pkey->algo);
196 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
197 	memcpy(ptr, pkey->params, pkey->paramlen);
198 
199 	memset(info, 0, sizeof(*info));
200 
201 	if (issig) {
202 		struct crypto_sig *sig;
203 
204 		sig = crypto_alloc_sig(alg_name, 0, 0);
205 		if (IS_ERR(sig)) {
206 			ret = PTR_ERR(sig);
207 			goto error_free_key;
208 		}
209 
210 		if (pkey->key_is_private)
211 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
212 		else
213 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
214 		if (ret < 0)
215 			goto error_free_sig;
216 
217 		len = crypto_sig_keysize(sig);
218 		info->key_size = len;
219 		info->max_sig_size = crypto_sig_maxsize(sig);
220 		info->max_data_size = crypto_sig_digestsize(sig);
221 
222 		info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
223 		if (pkey->key_is_private)
224 			info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
225 
226 		if (strcmp(params->encoding, "pkcs1") == 0) {
227 			info->max_enc_size = len / BITS_PER_BYTE;
228 			info->max_dec_size = len / BITS_PER_BYTE;
229 
230 			info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
231 			if (pkey->key_is_private)
232 				info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
233 		}
234 
235 error_free_sig:
236 		crypto_free_sig(sig);
237 	} else {
238 		struct crypto_akcipher *tfm;
239 
240 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
241 		if (IS_ERR(tfm)) {
242 			ret = PTR_ERR(tfm);
243 			goto error_free_key;
244 		}
245 
246 		if (pkey->key_is_private)
247 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
248 		else
249 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
250 		if (ret < 0)
251 			goto error_free_akcipher;
252 
253 		len = crypto_akcipher_maxsize(tfm);
254 		info->key_size = len * BITS_PER_BYTE;
255 		info->max_sig_size = len;
256 		info->max_data_size = len;
257 		info->max_enc_size = len;
258 		info->max_dec_size = len;
259 
260 		info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
261 		if (pkey->key_is_private)
262 			info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
263 
264 error_free_akcipher:
265 		crypto_free_akcipher(tfm);
266 	}
267 
268 error_free_key:
269 	kfree_sensitive(key);
270 	pr_devel("<==%s() = %d\n", __func__, ret);
271 	return ret;
272 }
273 
274 /*
275  * Do encryption, decryption and signing ops.
276  */
277 static int software_key_eds_op(struct kernel_pkey_params *params,
278 			       const void *in, void *out)
279 {
280 	const struct public_key *pkey = params->key->payload.data[asym_crypto];
281 	char alg_name[CRYPTO_MAX_ALG_NAME];
282 	struct crypto_akcipher *tfm;
283 	struct crypto_sig *sig;
284 	char *key, *ptr;
285 	bool issig;
286 	int ret;
287 
288 	pr_devel("==>%s()\n", __func__);
289 
290 	ret = software_key_determine_akcipher(pkey, params->encoding,
291 					      params->hash_algo, alg_name,
292 					      &issig, params->op);
293 	if (ret < 0)
294 		return ret;
295 
296 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
297 		      GFP_KERNEL);
298 	if (!key)
299 		return -ENOMEM;
300 
301 	memcpy(key, pkey->key, pkey->keylen);
302 	ptr = key + pkey->keylen;
303 	ptr = pkey_pack_u32(ptr, pkey->algo);
304 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
305 	memcpy(ptr, pkey->params, pkey->paramlen);
306 
307 	if (issig) {
308 		sig = crypto_alloc_sig(alg_name, 0, 0);
309 		if (IS_ERR(sig)) {
310 			ret = PTR_ERR(sig);
311 			goto error_free_key;
312 		}
313 
314 		if (pkey->key_is_private)
315 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
316 		else
317 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
318 		if (ret)
319 			goto error_free_tfm;
320 	} else {
321 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
322 		if (IS_ERR(tfm)) {
323 			ret = PTR_ERR(tfm);
324 			goto error_free_key;
325 		}
326 
327 		if (pkey->key_is_private)
328 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
329 		else
330 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
331 		if (ret)
332 			goto error_free_tfm;
333 	}
334 
335 	ret = -EINVAL;
336 
337 	/* Perform the encryption calculation. */
338 	switch (params->op) {
339 	case kernel_pkey_encrypt:
340 		if (issig)
341 			break;
342 		ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
343 						   out, params->out_len);
344 		break;
345 	case kernel_pkey_decrypt:
346 		if (issig)
347 			break;
348 		ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
349 						   out, params->out_len);
350 		break;
351 	case kernel_pkey_sign:
352 		if (!issig)
353 			break;
354 		ret = crypto_sig_sign(sig, in, params->in_len,
355 				      out, params->out_len);
356 		break;
357 	default:
358 		BUG();
359 	}
360 
361 	if (!issig && ret == 0)
362 		ret = crypto_akcipher_maxsize(tfm);
363 
364 error_free_tfm:
365 	if (issig)
366 		crypto_free_sig(sig);
367 	else
368 		crypto_free_akcipher(tfm);
369 error_free_key:
370 	kfree_sensitive(key);
371 	pr_devel("<==%s() = %d\n", __func__, ret);
372 	return ret;
373 }
374 
375 /*
376  * Verify a signature using a public key.
377  */
378 int public_key_verify_signature(const struct public_key *pkey,
379 				const struct public_key_signature *sig)
380 {
381 	char alg_name[CRYPTO_MAX_ALG_NAME];
382 	struct crypto_sig *tfm;
383 	char *key, *ptr;
384 	bool issig;
385 	int ret;
386 
387 	pr_devel("==>%s()\n", __func__);
388 
389 	BUG_ON(!pkey);
390 	BUG_ON(!sig);
391 	BUG_ON(!sig->s);
392 
393 	/*
394 	 * If the signature specifies a public key algorithm, it *must* match
395 	 * the key's actual public key algorithm.
396 	 *
397 	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
398 	 * keys do.  So the strings can mismatch slightly in that case:
399 	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
400 	 */
401 	if (sig->pkey_algo) {
402 		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
403 		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
404 		     strcmp(sig->pkey_algo, "ecdsa") != 0))
405 			return -EKEYREJECTED;
406 	}
407 
408 	ret = software_key_determine_akcipher(pkey, sig->encoding,
409 					      sig->hash_algo, alg_name,
410 					      &issig, kernel_pkey_verify);
411 	if (ret < 0)
412 		return ret;
413 
414 	tfm = crypto_alloc_sig(alg_name, 0, 0);
415 	if (IS_ERR(tfm))
416 		return PTR_ERR(tfm);
417 
418 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
419 		      GFP_KERNEL);
420 	if (!key) {
421 		ret = -ENOMEM;
422 		goto error_free_tfm;
423 	}
424 
425 	memcpy(key, pkey->key, pkey->keylen);
426 	ptr = key + pkey->keylen;
427 	ptr = pkey_pack_u32(ptr, pkey->algo);
428 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
429 	memcpy(ptr, pkey->params, pkey->paramlen);
430 
431 	if (pkey->key_is_private)
432 		ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
433 	else
434 		ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
435 	if (ret)
436 		goto error_free_key;
437 
438 	ret = crypto_sig_verify(tfm, sig->s, sig->s_size, sig->m, sig->m_size);
439 
440 error_free_key:
441 	kfree_sensitive(key);
442 error_free_tfm:
443 	crypto_free_sig(tfm);
444 	pr_devel("<==%s() = %d\n", __func__, ret);
445 	if (WARN_ON_ONCE(ret > 0))
446 		ret = -EINVAL;
447 	return ret;
448 }
449 EXPORT_SYMBOL_GPL(public_key_verify_signature);
450 
451 static int public_key_verify_signature_2(const struct key *key,
452 					 const struct public_key_signature *sig)
453 {
454 	const struct public_key *pk = key->payload.data[asym_crypto];
455 	return public_key_verify_signature(pk, sig);
456 }
457 
458 /*
459  * Public key algorithm asymmetric key subtype
460  */
461 struct asymmetric_key_subtype public_key_subtype = {
462 	.owner			= THIS_MODULE,
463 	.name			= "public_key",
464 	.name_len		= sizeof("public_key") - 1,
465 	.describe		= public_key_describe,
466 	.destroy		= public_key_destroy,
467 	.query			= software_key_query,
468 	.eds_op			= software_key_eds_op,
469 	.verify_signature	= public_key_verify_signature_2,
470 };
471 EXPORT_SYMBOL_GPL(public_key_subtype);
472