xref: /linux/crypto/asymmetric_keys/public_key.c (revision 7a9b709e7cc5ce1ffb84ce07bf6d157e1de758df) 
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 {
146 		/* Unknown public key algorithm */
147 		return -ENOPKG;
148 	}
149 	if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
150 		return -EINVAL;
151 	return 0;
152 }
153 
154 static u8 *pkey_pack_u32(u8 *dst, u32 val)
155 {
156 	memcpy(dst, &val, sizeof(val));
157 	return dst + sizeof(val);
158 }
159 
160 /*
161  * Query information about a key.
162  */
163 static int software_key_query(const struct kernel_pkey_params *params,
164 			      struct kernel_pkey_query *info)
165 {
166 	struct crypto_akcipher *tfm;
167 	struct public_key *pkey = params->key->payload.data[asym_crypto];
168 	char alg_name[CRYPTO_MAX_ALG_NAME];
169 	struct crypto_sig *sig;
170 	u8 *key, *ptr;
171 	int ret, len;
172 	bool issig;
173 
174 	ret = software_key_determine_akcipher(pkey, params->encoding,
175 					      params->hash_algo, alg_name,
176 					      &issig, kernel_pkey_sign);
177 	if (ret < 0)
178 		return ret;
179 
180 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
181 		      GFP_KERNEL);
182 	if (!key)
183 		return -ENOMEM;
184 
185 	memcpy(key, pkey->key, pkey->keylen);
186 	ptr = key + pkey->keylen;
187 	ptr = pkey_pack_u32(ptr, pkey->algo);
188 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
189 	memcpy(ptr, pkey->params, pkey->paramlen);
190 
191 	if (issig) {
192 		sig = crypto_alloc_sig(alg_name, 0, 0);
193 		if (IS_ERR(sig)) {
194 			ret = PTR_ERR(sig);
195 			goto error_free_key;
196 		}
197 
198 		if (pkey->key_is_private)
199 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
200 		else
201 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
202 		if (ret < 0)
203 			goto error_free_tfm;
204 
205 		len = crypto_sig_keysize(sig);
206 		info->max_sig_size = crypto_sig_maxsize(sig);
207 		info->max_data_size = crypto_sig_digestsize(sig);
208 
209 		info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
210 		if (pkey->key_is_private)
211 			info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
212 
213 		if (strcmp(params->encoding, "pkcs1") == 0) {
214 			info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
215 			if (pkey->key_is_private)
216 				info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
217 		}
218 	} else {
219 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
220 		if (IS_ERR(tfm)) {
221 			ret = PTR_ERR(tfm);
222 			goto error_free_key;
223 		}
224 
225 		if (pkey->key_is_private)
226 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
227 		else
228 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
229 		if (ret < 0)
230 			goto error_free_tfm;
231 
232 		len = crypto_akcipher_maxsize(tfm);
233 		info->max_sig_size = len;
234 		info->max_data_size = len;
235 
236 		info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
237 		if (pkey->key_is_private)
238 			info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
239 	}
240 
241 	info->key_size = len * 8;
242 	info->max_enc_size = len;
243 	info->max_dec_size = len;
244 
245 	ret = 0;
246 
247 error_free_tfm:
248 	if (issig)
249 		crypto_free_sig(sig);
250 	else
251 		crypto_free_akcipher(tfm);
252 error_free_key:
253 	kfree_sensitive(key);
254 	pr_devel("<==%s() = %d\n", __func__, ret);
255 	return ret;
256 }
257 
258 /*
259  * Do encryption, decryption and signing ops.
260  */
261 static int software_key_eds_op(struct kernel_pkey_params *params,
262 			       const void *in, void *out)
263 {
264 	const struct public_key *pkey = params->key->payload.data[asym_crypto];
265 	char alg_name[CRYPTO_MAX_ALG_NAME];
266 	struct crypto_akcipher *tfm;
267 	struct crypto_sig *sig;
268 	char *key, *ptr;
269 	bool issig;
270 	int ret;
271 
272 	pr_devel("==>%s()\n", __func__);
273 
274 	ret = software_key_determine_akcipher(pkey, params->encoding,
275 					      params->hash_algo, alg_name,
276 					      &issig, params->op);
277 	if (ret < 0)
278 		return ret;
279 
280 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
281 		      GFP_KERNEL);
282 	if (!key)
283 		return -ENOMEM;
284 
285 	memcpy(key, pkey->key, pkey->keylen);
286 	ptr = key + pkey->keylen;
287 	ptr = pkey_pack_u32(ptr, pkey->algo);
288 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
289 	memcpy(ptr, pkey->params, pkey->paramlen);
290 
291 	if (issig) {
292 		sig = crypto_alloc_sig(alg_name, 0, 0);
293 		if (IS_ERR(sig)) {
294 			ret = PTR_ERR(sig);
295 			goto error_free_key;
296 		}
297 
298 		if (pkey->key_is_private)
299 			ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
300 		else
301 			ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
302 		if (ret)
303 			goto error_free_tfm;
304 	} else {
305 		tfm = crypto_alloc_akcipher(alg_name, 0, 0);
306 		if (IS_ERR(tfm)) {
307 			ret = PTR_ERR(tfm);
308 			goto error_free_key;
309 		}
310 
311 		if (pkey->key_is_private)
312 			ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
313 		else
314 			ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
315 		if (ret)
316 			goto error_free_tfm;
317 	}
318 
319 	ret = -EINVAL;
320 
321 	/* Perform the encryption calculation. */
322 	switch (params->op) {
323 	case kernel_pkey_encrypt:
324 		if (issig)
325 			break;
326 		ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
327 						   out, params->out_len);
328 		break;
329 	case kernel_pkey_decrypt:
330 		if (issig)
331 			break;
332 		ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
333 						   out, params->out_len);
334 		break;
335 	case kernel_pkey_sign:
336 		if (!issig)
337 			break;
338 		ret = crypto_sig_sign(sig, in, params->in_len,
339 				      out, params->out_len);
340 		break;
341 	default:
342 		BUG();
343 	}
344 
345 	if (!issig && ret == 0)
346 		ret = crypto_akcipher_maxsize(tfm);
347 
348 error_free_tfm:
349 	if (issig)
350 		crypto_free_sig(sig);
351 	else
352 		crypto_free_akcipher(tfm);
353 error_free_key:
354 	kfree_sensitive(key);
355 	pr_devel("<==%s() = %d\n", __func__, ret);
356 	return ret;
357 }
358 
359 /*
360  * Verify a signature using a public key.
361  */
362 int public_key_verify_signature(const struct public_key *pkey,
363 				const struct public_key_signature *sig)
364 {
365 	char alg_name[CRYPTO_MAX_ALG_NAME];
366 	struct crypto_sig *tfm;
367 	char *key, *ptr;
368 	bool issig;
369 	int ret;
370 
371 	pr_devel("==>%s()\n", __func__);
372 
373 	BUG_ON(!pkey);
374 	BUG_ON(!sig);
375 	BUG_ON(!sig->s);
376 
377 	/*
378 	 * If the signature specifies a public key algorithm, it *must* match
379 	 * the key's actual public key algorithm.
380 	 *
381 	 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
382 	 * keys do.  So the strings can mismatch slightly in that case:
383 	 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
384 	 */
385 	if (sig->pkey_algo) {
386 		if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
387 		    (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
388 		     strcmp(sig->pkey_algo, "ecdsa") != 0))
389 			return -EKEYREJECTED;
390 	}
391 
392 	ret = software_key_determine_akcipher(pkey, sig->encoding,
393 					      sig->hash_algo, alg_name,
394 					      &issig, kernel_pkey_verify);
395 	if (ret < 0)
396 		return ret;
397 
398 	tfm = crypto_alloc_sig(alg_name, 0, 0);
399 	if (IS_ERR(tfm))
400 		return PTR_ERR(tfm);
401 
402 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
403 		      GFP_KERNEL);
404 	if (!key) {
405 		ret = -ENOMEM;
406 		goto error_free_tfm;
407 	}
408 
409 	memcpy(key, pkey->key, pkey->keylen);
410 	ptr = key + pkey->keylen;
411 	ptr = pkey_pack_u32(ptr, pkey->algo);
412 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
413 	memcpy(ptr, pkey->params, pkey->paramlen);
414 
415 	if (pkey->key_is_private)
416 		ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
417 	else
418 		ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
419 	if (ret)
420 		goto error_free_key;
421 
422 	ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
423 				sig->digest, sig->digest_size);
424 
425 error_free_key:
426 	kfree_sensitive(key);
427 error_free_tfm:
428 	crypto_free_sig(tfm);
429 	pr_devel("<==%s() = %d\n", __func__, ret);
430 	if (WARN_ON_ONCE(ret > 0))
431 		ret = -EINVAL;
432 	return ret;
433 }
434 EXPORT_SYMBOL_GPL(public_key_verify_signature);
435 
436 static int public_key_verify_signature_2(const struct key *key,
437 					 const struct public_key_signature *sig)
438 {
439 	const struct public_key *pk = key->payload.data[asym_crypto];
440 	return public_key_verify_signature(pk, sig);
441 }
442 
443 /*
444  * Public key algorithm asymmetric key subtype
445  */
446 struct asymmetric_key_subtype public_key_subtype = {
447 	.owner			= THIS_MODULE,
448 	.name			= "public_key",
449 	.name_len		= sizeof("public_key") - 1,
450 	.describe		= public_key_describe,
451 	.destroy		= public_key_destroy,
452 	.query			= software_key_query,
453 	.eds_op			= software_key_eds_op,
454 	.verify_signature	= public_key_verify_signature_2,
455 };
456 EXPORT_SYMBOL_GPL(public_key_subtype);
457