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 (!*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
pkey_pack_u32(u8 * dst,u32 val)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 */
software_key_query(const struct kernel_pkey_params * params,struct kernel_pkey_query * info)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 */
software_key_eds_op(struct kernel_pkey_params * params,const void * in,void * out)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 */
public_key_verify_signature(const struct public_key * pkey,const struct public_key_signature * sig)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
public_key_verify_signature_2(const struct key * key,const struct public_key_signature * sig)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