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 */
public_key_describe(const struct key * asymmetric_key,struct seq_file * m)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 */
public_key_free(struct public_key * key)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 */
public_key_destroy(void * payload0,void * payload3)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
software_key_determine_akcipher(const struct public_key * pkey,const char * encoding,const char * hash_algo,char alg_name[CRYPTO_MAX_ALG_NAME],bool * sig,enum kernel_pkey_operation op)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
pkey_pack_u32(u8 * dst,u32 val)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 */
software_key_query(const struct kernel_pkey_params * params,struct kernel_pkey_query * info)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 */
software_key_eds_op(struct kernel_pkey_params * params,const void * in,void * out)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 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)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
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)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