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 (!hash_algo) {
87 n = snprintf(buf: alg_name, CRYPTO_MAX_ALG_NAME,
88 fmt: "pkcs1pad(%s)",
89 pkey->pkey_algo);
90 } else {
91 n = snprintf(buf: alg_name, CRYPTO_MAX_ALG_NAME,
92 fmt: "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, "sm2") == 0) {
128 if (strcmp(encoding, "raw") != 0)
129 return -EINVAL;
130 if (!hash_algo)
131 return -EINVAL;
132 if (strcmp(hash_algo, "sm3") != 0)
133 return -EINVAL;
134 } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
135 if (strcmp(encoding, "raw") != 0)
136 return -EINVAL;
137 if (!hash_algo)
138 return -EINVAL;
139 if (strcmp(hash_algo, "streebog256") != 0 &&
140 strcmp(hash_algo, "streebog512") != 0)
141 return -EINVAL;
142 } else {
143 /* Unknown public key algorithm */
144 return -ENOPKG;
145 }
146 if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
147 return -EINVAL;
148 return 0;
149}
150
151static u8 *pkey_pack_u32(u8 *dst, u32 val)
152{
153 memcpy(dst, &val, sizeof(val));
154 return dst + sizeof(val);
155}
156
157/*
158 * Query information about a key.
159 */
160static int software_key_query(const struct kernel_pkey_params *params,
161 struct kernel_pkey_query *info)
162{
163 struct crypto_akcipher *tfm;
164 struct public_key *pkey = params->key->payload.data[asym_crypto];
165 char alg_name[CRYPTO_MAX_ALG_NAME];
166 struct crypto_sig *sig;
167 u8 *key, *ptr;
168 int ret, len;
169 bool issig;
170
171 ret = software_key_determine_akcipher(pkey, encoding: params->encoding,
172 hash_algo: params->hash_algo, alg_name,
173 sig: &issig, op: kernel_pkey_sign);
174 if (ret < 0)
175 return ret;
176
177 key = kmalloc(size: pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
178 GFP_KERNEL);
179 if (!key)
180 return -ENOMEM;
181
182 memcpy(key, pkey->key, pkey->keylen);
183 ptr = key + pkey->keylen;
184 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
185 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
186 memcpy(ptr, pkey->params, pkey->paramlen);
187
188 if (issig) {
189 sig = crypto_alloc_sig(alg_name, type: 0, mask: 0);
190 if (IS_ERR(ptr: sig)) {
191 ret = PTR_ERR(ptr: sig);
192 goto error_free_key;
193 }
194
195 if (pkey->key_is_private)
196 ret = crypto_sig_set_privkey(tfm: sig, key, keylen: pkey->keylen);
197 else
198 ret = crypto_sig_set_pubkey(tfm: sig, key, keylen: pkey->keylen);
199 if (ret < 0)
200 goto error_free_tfm;
201
202 len = crypto_sig_maxsize(tfm: sig);
203
204 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
205 if (pkey->key_is_private)
206 info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
207
208 if (strcmp(params->encoding, "pkcs1") == 0) {
209 info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
210 if (pkey->key_is_private)
211 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
212 }
213 } else {
214 tfm = crypto_alloc_akcipher(alg_name, type: 0, mask: 0);
215 if (IS_ERR(ptr: tfm)) {
216 ret = PTR_ERR(ptr: tfm);
217 goto error_free_key;
218 }
219
220 if (pkey->key_is_private)
221 ret = crypto_akcipher_set_priv_key(tfm, key, keylen: pkey->keylen);
222 else
223 ret = crypto_akcipher_set_pub_key(tfm, key, keylen: pkey->keylen);
224 if (ret < 0)
225 goto error_free_tfm;
226
227 len = crypto_akcipher_maxsize(tfm);
228
229 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
230 if (pkey->key_is_private)
231 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
232 }
233
234 info->key_size = len * 8;
235
236 if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
237 /*
238 * ECDSA key sizes are much smaller than RSA, and thus could
239 * operate on (hashed) inputs that are larger than key size.
240 * For example SHA384-hashed input used with secp256r1
241 * based keys. Set max_data_size to be at least as large as
242 * the largest supported hash size (SHA512)
243 */
244 info->max_data_size = 64;
245
246 /*
247 * Verify takes ECDSA-Sig (described in RFC 5480) as input,
248 * which is actually 2 'key_size'-bit integers encoded in
249 * ASN.1. Account for the ASN.1 encoding overhead here.
250 */
251 info->max_sig_size = 2 * (len + 3) + 2;
252 } else {
253 info->max_data_size = len;
254 info->max_sig_size = len;
255 }
256
257 info->max_enc_size = len;
258 info->max_dec_size = len;
259
260 ret = 0;
261
262error_free_tfm:
263 if (issig)
264 crypto_free_sig(tfm: sig);
265 else
266 crypto_free_akcipher(tfm);
267error_free_key:
268 kfree_sensitive(objp: key);
269 pr_devel("<==%s() = %d\n", __func__, ret);
270 return ret;
271}
272
273/*
274 * Do encryption, decryption and signing ops.
275 */
276static int software_key_eds_op(struct kernel_pkey_params *params,
277 const void *in, void *out)
278{
279 const struct public_key *pkey = params->key->payload.data[asym_crypto];
280 char alg_name[CRYPTO_MAX_ALG_NAME];
281 struct crypto_akcipher *tfm;
282 struct crypto_sig *sig;
283 char *key, *ptr;
284 bool issig;
285 int ksz;
286 int ret;
287
288 pr_devel("==>%s()\n", __func__);
289
290 ret = software_key_determine_akcipher(pkey, encoding: params->encoding,
291 hash_algo: params->hash_algo, alg_name,
292 sig: &issig, op: params->op);
293 if (ret < 0)
294 return ret;
295
296 key = kmalloc(size: pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
297 GFP_KERNEL);
298 if (!key)
299 return -ENOMEM;
300
301 memcpy(key, pkey->key, pkey->keylen);
302 ptr = key + pkey->keylen;
303 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
304 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
305 memcpy(ptr, pkey->params, pkey->paramlen);
306
307 if (issig) {
308 sig = crypto_alloc_sig(alg_name, type: 0, mask: 0);
309 if (IS_ERR(ptr: sig)) {
310 ret = PTR_ERR(ptr: sig);
311 goto error_free_key;
312 }
313
314 if (pkey->key_is_private)
315 ret = crypto_sig_set_privkey(tfm: sig, key, keylen: pkey->keylen);
316 else
317 ret = crypto_sig_set_pubkey(tfm: sig, key, keylen: pkey->keylen);
318 if (ret)
319 goto error_free_tfm;
320
321 ksz = crypto_sig_maxsize(tfm: sig);
322 } else {
323 tfm = crypto_alloc_akcipher(alg_name, type: 0, mask: 0);
324 if (IS_ERR(ptr: tfm)) {
325 ret = PTR_ERR(ptr: tfm);
326 goto error_free_key;
327 }
328
329 if (pkey->key_is_private)
330 ret = crypto_akcipher_set_priv_key(tfm, key, keylen: pkey->keylen);
331 else
332 ret = crypto_akcipher_set_pub_key(tfm, key, keylen: pkey->keylen);
333 if (ret)
334 goto error_free_tfm;
335
336 ksz = crypto_akcipher_maxsize(tfm);
337 }
338
339 ret = -EINVAL;
340
341 /* Perform the encryption calculation. */
342 switch (params->op) {
343 case kernel_pkey_encrypt:
344 if (issig)
345 break;
346 ret = crypto_akcipher_sync_encrypt(tfm, src: in, slen: params->in_len,
347 dst: out, dlen: params->out_len);
348 break;
349 case kernel_pkey_decrypt:
350 if (issig)
351 break;
352 ret = crypto_akcipher_sync_decrypt(tfm, src: in, slen: params->in_len,
353 dst: out, dlen: params->out_len);
354 break;
355 case kernel_pkey_sign:
356 if (!issig)
357 break;
358 ret = crypto_sig_sign(tfm: sig, src: in, slen: params->in_len,
359 dst: out, dlen: params->out_len);
360 break;
361 default:
362 BUG();
363 }
364
365 if (ret == 0)
366 ret = ksz;
367
368error_free_tfm:
369 if (issig)
370 crypto_free_sig(tfm: sig);
371 else
372 crypto_free_akcipher(tfm);
373error_free_key:
374 kfree_sensitive(objp: key);
375 pr_devel("<==%s() = %d\n", __func__, ret);
376 return ret;
377}
378
379/*
380 * Verify a signature using a public key.
381 */
382int public_key_verify_signature(const struct public_key *pkey,
383 const struct public_key_signature *sig)
384{
385 char alg_name[CRYPTO_MAX_ALG_NAME];
386 struct crypto_sig *tfm;
387 char *key, *ptr;
388 bool issig;
389 int ret;
390
391 pr_devel("==>%s()\n", __func__);
392
393 BUG_ON(!pkey);
394 BUG_ON(!sig);
395 BUG_ON(!sig->s);
396
397 /*
398 * If the signature specifies a public key algorithm, it *must* match
399 * the key's actual public key algorithm.
400 *
401 * Small exception: ECDSA signatures don't specify the curve, but ECDSA
402 * keys do. So the strings can mismatch slightly in that case:
403 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
404 */
405 if (sig->pkey_algo) {
406 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
407 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
408 strcmp(sig->pkey_algo, "ecdsa") != 0))
409 return -EKEYREJECTED;
410 }
411
412 ret = software_key_determine_akcipher(pkey, encoding: sig->encoding,
413 hash_algo: sig->hash_algo, alg_name,
414 sig: &issig, op: kernel_pkey_verify);
415 if (ret < 0)
416 return ret;
417
418 tfm = crypto_alloc_sig(alg_name, type: 0, mask: 0);
419 if (IS_ERR(ptr: tfm))
420 return PTR_ERR(ptr: tfm);
421
422 key = kmalloc(size: pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
423 GFP_KERNEL);
424 if (!key) {
425 ret = -ENOMEM;
426 goto error_free_tfm;
427 }
428
429 memcpy(key, pkey->key, pkey->keylen);
430 ptr = key + pkey->keylen;
431 ptr = pkey_pack_u32(dst: ptr, val: pkey->algo);
432 ptr = pkey_pack_u32(dst: ptr, val: pkey->paramlen);
433 memcpy(ptr, pkey->params, pkey->paramlen);
434
435 if (pkey->key_is_private)
436 ret = crypto_sig_set_privkey(tfm, key, keylen: pkey->keylen);
437 else
438 ret = crypto_sig_set_pubkey(tfm, key, keylen: pkey->keylen);
439 if (ret)
440 goto error_free_key;
441
442 ret = crypto_sig_verify(tfm, src: sig->s, slen: sig->s_size,
443 digest: sig->digest, dlen: sig->digest_size);
444
445error_free_key:
446 kfree_sensitive(objp: key);
447error_free_tfm:
448 crypto_free_sig(tfm);
449 pr_devel("<==%s() = %d\n", __func__, ret);
450 if (WARN_ON_ONCE(ret > 0))
451 ret = -EINVAL;
452 return ret;
453}
454EXPORT_SYMBOL_GPL(public_key_verify_signature);
455
456static int public_key_verify_signature_2(const struct key *key,
457 const struct public_key_signature *sig)
458{
459 const struct public_key *pk = key->payload.data[asym_crypto];
460 return public_key_verify_signature(pk, sig);
461}
462
463/*
464 * Public key algorithm asymmetric key subtype
465 */
466struct asymmetric_key_subtype public_key_subtype = {
467 .owner = THIS_MODULE,
468 .name = "public_key",
469 .name_len = sizeof("public_key") - 1,
470 .describe = public_key_describe,
471 .destroy = public_key_destroy,
472 .query = software_key_query,
473 .eds_op = software_key_eds_op,
474 .verify_signature = public_key_verify_signature_2,
475};
476EXPORT_SYMBOL_GPL(public_key_subtype);
477

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