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
23MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
24MODULE_AUTHOR("Red Hat, Inc.");
25MODULE_LICENSE("GPL");
26
27/*
28 * Provide a part of a description of the key for /proc/keys.
29 */
30static 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, fmt: "%s.%s", key->id_type, key->pkey_algo);
37}
38
39/*
40 * Destroy a public key algorithm key.
41 */
42void public_key_free(struct public_key *key)
43{
44 if (key) {
45 kfree_sensitive(objp: key->key);
46 kfree(objp: key->params);
47 kfree(objp: key);
48 }
49}
50EXPORT_SYMBOL_GPL(public_key_free);
51
52/*
53 * Destroy a public key algorithm key.
54 */
55static void public_key_destroy(void *payload0, void *payload3)
56{
57 public_key_free(payload0);
58 public_key_signature_free(sig: 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 */
66static int
67software_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(buf: alg_name, CRYPTO_MAX_ALG_NAME,
92 fmt: "pkcs1pad(%s)",
93 pkey->pkey_algo);
94 } else {
95 if (!hash_algo)
96 hash_algo = "none";
97 n = snprintf(buf: alg_name, CRYPTO_MAX_ALG_NAME,
98 fmt: "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(buf: alg_name, CRYPTO_MAX_ALG_NAME, fmt: "%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
154static 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 */
163static int software_key_query(const struct kernel_pkey_params *params,
164 struct kernel_pkey_query *info)
165{
166 struct public_key *pkey = params->key->payload.data[asym_crypto];
167 char alg_name[CRYPTO_MAX_ALG_NAME];
168 u8 *key, *ptr;
169 int ret, len;
170 bool issig;
171
172 ret = software_key_determine_akcipher(pkey, encoding: params->encoding,
173 hash_algo: params->hash_algo, alg_name,
174 sig: &issig, op: kernel_pkey_sign);
175 if (ret < 0)
176 return ret;
177
178 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
179 GFP_KERNEL);
180 if (!key)
181 return -ENOMEM;
182
183 memcpy(key, pkey->key, pkey->keylen);
184 ptr = key + pkey->keylen;
185 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
186 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
187 memcpy(ptr, pkey->params, pkey->paramlen);
188
189 memset(info, 0, sizeof(*info));
190
191 if (issig) {
192 struct crypto_sig *sig;
193
194 sig = crypto_alloc_sig(alg_name, type: 0, mask: 0);
195 if (IS_ERR(ptr: sig)) {
196 ret = PTR_ERR(ptr: sig);
197 goto error_free_key;
198 }
199
200 if (pkey->key_is_private)
201 ret = crypto_sig_set_privkey(tfm: sig, key, keylen: pkey->keylen);
202 else
203 ret = crypto_sig_set_pubkey(tfm: sig, key, keylen: pkey->keylen);
204 if (ret < 0)
205 goto error_free_sig;
206
207 len = crypto_sig_keysize(tfm: sig);
208 info->key_size = len;
209 info->max_sig_size = crypto_sig_maxsize(tfm: sig);
210 info->max_data_size = crypto_sig_digestsize(tfm: sig);
211
212 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
213 if (pkey->key_is_private)
214 info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
215
216 if (strcmp(params->encoding, "pkcs1") == 0) {
217 info->max_enc_size = len / BITS_PER_BYTE;
218 info->max_dec_size = len / BITS_PER_BYTE;
219
220 info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
221 if (pkey->key_is_private)
222 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
223 }
224
225error_free_sig:
226 crypto_free_sig(tfm: sig);
227 } else {
228 struct crypto_akcipher *tfm;
229
230 tfm = crypto_alloc_akcipher(alg_name, type: 0, mask: 0);
231 if (IS_ERR(ptr: tfm)) {
232 ret = PTR_ERR(ptr: tfm);
233 goto error_free_key;
234 }
235
236 if (pkey->key_is_private)
237 ret = crypto_akcipher_set_priv_key(tfm, key, keylen: pkey->keylen);
238 else
239 ret = crypto_akcipher_set_pub_key(tfm, key, keylen: pkey->keylen);
240 if (ret < 0)
241 goto error_free_akcipher;
242
243 len = crypto_akcipher_maxsize(tfm);
244 info->key_size = len * BITS_PER_BYTE;
245 info->max_sig_size = len;
246 info->max_data_size = len;
247 info->max_enc_size = len;
248 info->max_dec_size = len;
249
250 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
251 if (pkey->key_is_private)
252 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
253
254error_free_akcipher:
255 crypto_free_akcipher(tfm);
256 }
257
258error_free_key:
259 kfree_sensitive(objp: key);
260 pr_devel("<==%s() = %d\n", __func__, ret);
261 return ret;
262}
263
264/*
265 * Do encryption, decryption and signing ops.
266 */
267static int software_key_eds_op(struct kernel_pkey_params *params,
268 const void *in, void *out)
269{
270 const struct public_key *pkey = params->key->payload.data[asym_crypto];
271 char alg_name[CRYPTO_MAX_ALG_NAME];
272 struct crypto_akcipher *tfm;
273 struct crypto_sig *sig;
274 char *key, *ptr;
275 bool issig;
276 int ret;
277
278 pr_devel("==>%s()\n", __func__);
279
280 ret = software_key_determine_akcipher(pkey, encoding: params->encoding,
281 hash_algo: params->hash_algo, alg_name,
282 sig: &issig, op: params->op);
283 if (ret < 0)
284 return ret;
285
286 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
287 GFP_KERNEL);
288 if (!key)
289 return -ENOMEM;
290
291 memcpy(key, pkey->key, pkey->keylen);
292 ptr = key + pkey->keylen;
293 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
294 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
295 memcpy(ptr, pkey->params, pkey->paramlen);
296
297 if (issig) {
298 sig = crypto_alloc_sig(alg_name, type: 0, mask: 0);
299 if (IS_ERR(ptr: sig)) {
300 ret = PTR_ERR(ptr: sig);
301 goto error_free_key;
302 }
303
304 if (pkey->key_is_private)
305 ret = crypto_sig_set_privkey(tfm: sig, key, keylen: pkey->keylen);
306 else
307 ret = crypto_sig_set_pubkey(tfm: sig, key, keylen: pkey->keylen);
308 if (ret)
309 goto error_free_tfm;
310 } else {
311 tfm = crypto_alloc_akcipher(alg_name, type: 0, mask: 0);
312 if (IS_ERR(ptr: tfm)) {
313 ret = PTR_ERR(ptr: tfm);
314 goto error_free_key;
315 }
316
317 if (pkey->key_is_private)
318 ret = crypto_akcipher_set_priv_key(tfm, key, keylen: pkey->keylen);
319 else
320 ret = crypto_akcipher_set_pub_key(tfm, key, keylen: pkey->keylen);
321 if (ret)
322 goto error_free_tfm;
323 }
324
325 ret = -EINVAL;
326
327 /* Perform the encryption calculation. */
328 switch (params->op) {
329 case kernel_pkey_encrypt:
330 if (issig)
331 break;
332 ret = crypto_akcipher_sync_encrypt(tfm, src: in, slen: params->in_len,
333 dst: out, dlen: params->out_len);
334 break;
335 case kernel_pkey_decrypt:
336 if (issig)
337 break;
338 ret = crypto_akcipher_sync_decrypt(tfm, src: in, slen: params->in_len,
339 dst: out, dlen: params->out_len);
340 break;
341 case kernel_pkey_sign:
342 if (!issig)
343 break;
344 ret = crypto_sig_sign(tfm: sig, src: in, slen: params->in_len,
345 dst: out, dlen: params->out_len);
346 break;
347 default:
348 BUG();
349 }
350
351 if (!issig && ret == 0)
352 ret = crypto_akcipher_maxsize(tfm);
353
354error_free_tfm:
355 if (issig)
356 crypto_free_sig(tfm: sig);
357 else
358 crypto_free_akcipher(tfm);
359error_free_key:
360 kfree_sensitive(objp: key);
361 pr_devel("<==%s() = %d\n", __func__, ret);
362 return ret;
363}
364
365/*
366 * Verify a signature using a public key.
367 */
368int public_key_verify_signature(const struct public_key *pkey,
369 const struct public_key_signature *sig)
370{
371 char alg_name[CRYPTO_MAX_ALG_NAME];
372 struct crypto_sig *tfm;
373 char *key, *ptr;
374 bool issig;
375 int ret;
376
377 pr_devel("==>%s()\n", __func__);
378
379 BUG_ON(!pkey);
380 BUG_ON(!sig);
381 BUG_ON(!sig->s);
382
383 /*
384 * If the signature specifies a public key algorithm, it *must* match
385 * the key's actual public key algorithm.
386 *
387 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
388 * keys do. So the strings can mismatch slightly in that case:
389 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
390 */
391 if (sig->pkey_algo) {
392 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
393 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
394 strcmp(sig->pkey_algo, "ecdsa") != 0))
395 return -EKEYREJECTED;
396 }
397
398 ret = software_key_determine_akcipher(pkey, encoding: sig->encoding,
399 hash_algo: sig->hash_algo, alg_name,
400 sig: &issig, op: kernel_pkey_verify);
401 if (ret < 0)
402 return ret;
403
404 tfm = crypto_alloc_sig(alg_name, type: 0, mask: 0);
405 if (IS_ERR(ptr: tfm))
406 return PTR_ERR(ptr: tfm);
407
408 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
409 GFP_KERNEL);
410 if (!key) {
411 ret = -ENOMEM;
412 goto error_free_tfm;
413 }
414
415 memcpy(key, pkey->key, pkey->keylen);
416 ptr = key + pkey->keylen;
417 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
418 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
419 memcpy(ptr, pkey->params, pkey->paramlen);
420
421 if (pkey->key_is_private)
422 ret = crypto_sig_set_privkey(tfm, key, keylen: pkey->keylen);
423 else
424 ret = crypto_sig_set_pubkey(tfm, key, keylen: pkey->keylen);
425 if (ret)
426 goto error_free_key;
427
428 ret = crypto_sig_verify(tfm, src: sig->s, slen: sig->s_size,
429 digest: sig->digest, dlen: sig->digest_size);
430
431error_free_key:
432 kfree_sensitive(objp: key);
433error_free_tfm:
434 crypto_free_sig(tfm);
435 pr_devel("<==%s() = %d\n", __func__, ret);
436 if (WARN_ON_ONCE(ret > 0))
437 ret = -EINVAL;
438 return ret;
439}
440EXPORT_SYMBOL_GPL(public_key_verify_signature);
441
442static int public_key_verify_signature_2(const struct key *key,
443 const struct public_key_signature *sig)
444{
445 const struct public_key *pk = key->payload.data[asym_crypto];
446 return public_key_verify_signature(pk, sig);
447}
448
449/*
450 * Public key algorithm asymmetric key subtype
451 */
452struct asymmetric_key_subtype public_key_subtype = {
453 .owner = THIS_MODULE,
454 .name = "public_key",
455 .name_len = sizeof("public_key") - 1,
456 .describe = public_key_describe,
457 .destroy = public_key_destroy,
458 .query = software_key_query,
459 .eds_op = software_key_eds_op,
460 .verify_signature = public_key_verify_signature_2,
461};
462EXPORT_SYMBOL_GPL(public_key_subtype);
463

source code of linux/crypto/asymmetric_keys/public_key.c