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, "%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(key->key);
46		kfree(key->params);
47		kfree(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(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(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
148static 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 */
157static 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
259error_free_tfm:
260	if (issig)
261		crypto_free_sig(sig);
262	else
263		crypto_free_akcipher(tfm);
264error_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 */
273static 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
365error_free_tfm:
366	if (issig)
367		crypto_free_sig(sig);
368	else
369		crypto_free_akcipher(tfm);
370error_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 */
379int 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
442error_free_key:
443	kfree_sensitive(key);
444error_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}
451EXPORT_SYMBOL_GPL(public_key_verify_signature);
452
453static 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 */
463struct 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};
473EXPORT_SYMBOL_GPL(public_key_subtype);
474