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 return -EINVAL;
124 } else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
125 if (strcmp(encoding, "raw") != 0)
126 return -EINVAL;
127 if (!hash_algo)
128 return -EINVAL;
129 if (strcmp(hash_algo, "sm3") != 0)
130 return -EINVAL;
131 } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
132 if (strcmp(encoding, "raw") != 0)
133 return -EINVAL;
134 if (!hash_algo)
135 return -EINVAL;
136 if (strcmp(hash_algo, "streebog256") != 0 &&
137 strcmp(hash_algo, "streebog512") != 0)
138 return -EINVAL;
139 } else {
140 /* Unknown public key algorithm */
141 return -ENOPKG;
142 }
143 if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
144 return -EINVAL;
145 return 0;
146 }
147
pkey_pack_u32(u8 * dst,u32 val)148 static u8 *pkey_pack_u32(u8 *dst, u32 val)
149 {
150 memcpy(dst, &val, sizeof(val));
151 return dst + sizeof(val);
152 }
153
154 /*
155 * Query information about a key.
156 */
software_key_query(const struct kernel_pkey_params * params,struct kernel_pkey_query * info)157 static int software_key_query(const struct kernel_pkey_params *params,
158 struct kernel_pkey_query *info)
159 {
160 struct crypto_akcipher *tfm;
161 struct public_key *pkey = params->key->payload.data[asym_crypto];
162 char alg_name[CRYPTO_MAX_ALG_NAME];
163 struct crypto_sig *sig;
164 u8 *key, *ptr;
165 int ret, len;
166 bool issig;
167
168 ret = software_key_determine_akcipher(pkey, params->encoding,
169 params->hash_algo, alg_name,
170 &issig, kernel_pkey_sign);
171 if (ret < 0)
172 return ret;
173
174 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
175 GFP_KERNEL);
176 if (!key)
177 return -ENOMEM;
178
179 memcpy(key, pkey->key, pkey->keylen);
180 ptr = key + pkey->keylen;
181 ptr = pkey_pack_u32(ptr, pkey->algo);
182 ptr = pkey_pack_u32(ptr, pkey->paramlen);
183 memcpy(ptr, pkey->params, pkey->paramlen);
184
185 if (issig) {
186 sig = crypto_alloc_sig(alg_name, 0, 0);
187 if (IS_ERR(sig)) {
188 ret = PTR_ERR(sig);
189 goto error_free_key;
190 }
191
192 if (pkey->key_is_private)
193 ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
194 else
195 ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
196 if (ret < 0)
197 goto error_free_tfm;
198
199 len = crypto_sig_maxsize(sig);
200
201 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
202 if (pkey->key_is_private)
203 info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
204
205 if (strcmp(params->encoding, "pkcs1") == 0) {
206 info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
207 if (pkey->key_is_private)
208 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
209 }
210 } else {
211 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
212 if (IS_ERR(tfm)) {
213 ret = PTR_ERR(tfm);
214 goto error_free_key;
215 }
216
217 if (pkey->key_is_private)
218 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
219 else
220 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
221 if (ret < 0)
222 goto error_free_tfm;
223
224 len = crypto_akcipher_maxsize(tfm);
225
226 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
227 if (pkey->key_is_private)
228 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
229 }
230
231 info->key_size = len * 8;
232
233 if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
234 /*
235 * ECDSA key sizes are much smaller than RSA, and thus could
236 * operate on (hashed) inputs that are larger than key size.
237 * For example SHA384-hashed input used with secp256r1
238 * based keys. Set max_data_size to be at least as large as
239 * the largest supported hash size (SHA512)
240 */
241 info->max_data_size = 64;
242
243 /*
244 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
245 * which is actually 2 'key_size'-bit integers encoded in
246 * ASN.1. Account for the ASN.1 encoding overhead here.
247 */
248 info->max_sig_size = 2 * (len + 3) + 2;
249 } else {
250 info->max_data_size = len;
251 info->max_sig_size = len;
252 }
253
254 info->max_enc_size = len;
255 info->max_dec_size = len;
256
257 ret = 0;
258
259 error_free_tfm:
260 if (issig)
261 crypto_free_sig(sig);
262 else
263 crypto_free_akcipher(tfm);
264 error_free_key:
265 kfree_sensitive(key);
266 pr_devel("<==%s() = %d\n", __func__, ret);
267 return ret;
268 }
269
270 /*
271 * Do encryption, decryption and signing ops.
272 */
software_key_eds_op(struct kernel_pkey_params * params,const void * in,void * out)273 static int software_key_eds_op(struct kernel_pkey_params *params,
274 const void *in, void *out)
275 {
276 const struct public_key *pkey = params->key->payload.data[asym_crypto];
277 char alg_name[CRYPTO_MAX_ALG_NAME];
278 struct crypto_akcipher *tfm;
279 struct crypto_sig *sig;
280 char *key, *ptr;
281 bool issig;
282 int ksz;
283 int ret;
284
285 pr_devel("==>%s()\n", __func__);
286
287 ret = software_key_determine_akcipher(pkey, params->encoding,
288 params->hash_algo, alg_name,
289 &issig, params->op);
290 if (ret < 0)
291 return ret;
292
293 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
294 GFP_KERNEL);
295 if (!key)
296 return -ENOMEM;
297
298 memcpy(key, pkey->key, pkey->keylen);
299 ptr = key + pkey->keylen;
300 ptr = pkey_pack_u32(ptr, pkey->algo);
301 ptr = pkey_pack_u32(ptr, pkey->paramlen);
302 memcpy(ptr, pkey->params, pkey->paramlen);
303
304 if (issig) {
305 sig = crypto_alloc_sig(alg_name, 0, 0);
306 if (IS_ERR(sig)) {
307 ret = PTR_ERR(sig);
308 goto error_free_key;
309 }
310
311 if (pkey->key_is_private)
312 ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
313 else
314 ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
315 if (ret)
316 goto error_free_tfm;
317
318 ksz = crypto_sig_maxsize(sig);
319 } else {
320 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
321 if (IS_ERR(tfm)) {
322 ret = PTR_ERR(tfm);
323 goto error_free_key;
324 }
325
326 if (pkey->key_is_private)
327 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
328 else
329 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
330 if (ret)
331 goto error_free_tfm;
332
333 ksz = crypto_akcipher_maxsize(tfm);
334 }
335
336 ret = -EINVAL;
337
338 /* Perform the encryption calculation. */
339 switch (params->op) {
340 case kernel_pkey_encrypt:
341 if (issig)
342 break;
343 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
344 out, params->out_len);
345 break;
346 case kernel_pkey_decrypt:
347 if (issig)
348 break;
349 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
350 out, params->out_len);
351 break;
352 case kernel_pkey_sign:
353 if (!issig)
354 break;
355 ret = crypto_sig_sign(sig, in, params->in_len,
356 out, params->out_len);
357 break;
358 default:
359 BUG();
360 }
361
362 if (ret == 0)
363 ret = ksz;
364
365 error_free_tfm:
366 if (issig)
367 crypto_free_sig(sig);
368 else
369 crypto_free_akcipher(tfm);
370 error_free_key:
371 kfree_sensitive(key);
372 pr_devel("<==%s() = %d\n", __func__, ret);
373 return ret;
374 }
375
376 /*
377 * Verify a signature using a public key.
378 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)379 int public_key_verify_signature(const struct public_key *pkey,
380 const struct public_key_signature *sig)
381 {
382 char alg_name[CRYPTO_MAX_ALG_NAME];
383 struct crypto_sig *tfm;
384 char *key, *ptr;
385 bool issig;
386 int ret;
387
388 pr_devel("==>%s()\n", __func__);
389
390 BUG_ON(!pkey);
391 BUG_ON(!sig);
392 BUG_ON(!sig->s);
393
394 /*
395 * If the signature specifies a public key algorithm, it *must* match
396 * the key's actual public key algorithm.
397 *
398 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
399 * keys do. So the strings can mismatch slightly in that case:
400 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
401 */
402 if (sig->pkey_algo) {
403 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
404 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
405 strcmp(sig->pkey_algo, "ecdsa") != 0))
406 return -EKEYREJECTED;
407 }
408
409 ret = software_key_determine_akcipher(pkey, sig->encoding,
410 sig->hash_algo, alg_name,
411 &issig, kernel_pkey_verify);
412 if (ret < 0)
413 return ret;
414
415 tfm = crypto_alloc_sig(alg_name, 0, 0);
416 if (IS_ERR(tfm))
417 return PTR_ERR(tfm);
418
419 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
420 GFP_KERNEL);
421 if (!key) {
422 ret = -ENOMEM;
423 goto error_free_tfm;
424 }
425
426 memcpy(key, pkey->key, pkey->keylen);
427 ptr = key + pkey->keylen;
428 ptr = pkey_pack_u32(ptr, pkey->algo);
429 ptr = pkey_pack_u32(ptr, pkey->paramlen);
430 memcpy(ptr, pkey->params, pkey->paramlen);
431
432 if (pkey->key_is_private)
433 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
434 else
435 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
436 if (ret)
437 goto error_free_key;
438
439 ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
440 sig->digest, sig->digest_size);
441
442 error_free_key:
443 kfree_sensitive(key);
444 error_free_tfm:
445 crypto_free_sig(tfm);
446 pr_devel("<==%s() = %d\n", __func__, ret);
447 if (WARN_ON_ONCE(ret > 0))
448 ret = -EINVAL;
449 return ret;
450 }
451 EXPORT_SYMBOL_GPL(public_key_verify_signature);
452
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)453 static int public_key_verify_signature_2(const struct key *key,
454 const struct public_key_signature *sig)
455 {
456 const struct public_key *pk = key->payload.data[asym_crypto];
457 return public_key_verify_signature(pk, sig);
458 }
459
460 /*
461 * Public key algorithm asymmetric key subtype
462 */
463 struct asymmetric_key_subtype public_key_subtype = {
464 .owner = THIS_MODULE,
465 .name = "public_key",
466 .name_len = sizeof("public_key") - 1,
467 .describe = public_key_describe,
468 .destroy = public_key_destroy,
469 .query = software_key_query,
470 .eds_op = software_key_eds_op,
471 .verify_signature = public_key_verify_signature_2,
472 };
473 EXPORT_SYMBOL_GPL(public_key_subtype);
474