xref: /linux/crypto/asymmetric_keys/public_key.c (revision 4be5e8648b0c287aefc6ac3f3a0b12c696054f43) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* In-software asymmetric public-key crypto subtype
3  *
4  * See Documentation/crypto/asymmetric-keys.txt
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 <linux/module.h>
12 #include <linux/export.h>
13 #include <linux/kernel.h>
14 #include <linux/slab.h>
15 #include <linux/seq_file.h>
16 #include <linux/scatterlist.h>
17 #include <keys/asymmetric-subtype.h>
18 #include <crypto/public_key.h>
19 #include <crypto/akcipher.h>
20 
21 MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
22 MODULE_AUTHOR("Red Hat, Inc.");
23 MODULE_LICENSE("GPL");
24 
25 /*
26  * Provide a part of a description of the key for /proc/keys.
27  */
28 static void public_key_describe(const struct key *asymmetric_key,
29 				struct seq_file *m)
30 {
31 	struct public_key *key = asymmetric_key->payload.data[asym_crypto];
32 
33 	if (key)
34 		seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
35 }
36 
37 /*
38  * Destroy a public key algorithm key.
39  */
40 void public_key_free(struct public_key *key)
41 {
42 	if (key) {
43 		kfree(key->key);
44 		kfree(key->params);
45 		kfree(key);
46 	}
47 }
48 EXPORT_SYMBOL_GPL(public_key_free);
49 
50 /*
51  * Destroy a public key algorithm key.
52  */
53 static void public_key_destroy(void *payload0, void *payload3)
54 {
55 	public_key_free(payload0);
56 	public_key_signature_free(payload3);
57 }
58 
59 /*
60  * Determine the crypto algorithm name.
61  */
62 static
63 int software_key_determine_akcipher(const char *encoding,
64 				    const char *hash_algo,
65 				    const struct public_key *pkey,
66 				    char alg_name[CRYPTO_MAX_ALG_NAME])
67 {
68 	int n;
69 
70 	if (strcmp(encoding, "pkcs1") == 0) {
71 		/* The data wangled by the RSA algorithm is typically padded
72 		 * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
73 		 * sec 8.2].
74 		 */
75 		if (!hash_algo)
76 			n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
77 				     "pkcs1pad(%s)",
78 				     pkey->pkey_algo);
79 		else
80 			n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
81 				     "pkcs1pad(%s,%s)",
82 				     pkey->pkey_algo, hash_algo);
83 		return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
84 	}
85 
86 	if (strcmp(encoding, "raw") == 0) {
87 		strcpy(alg_name, pkey->pkey_algo);
88 		return 0;
89 	}
90 
91 	return -ENOPKG;
92 }
93 
94 static u8 *pkey_pack_u32(u8 *dst, u32 val)
95 {
96 	memcpy(dst, &val, sizeof(val));
97 	return dst + sizeof(val);
98 }
99 
100 /*
101  * Query information about a key.
102  */
103 static int software_key_query(const struct kernel_pkey_params *params,
104 			      struct kernel_pkey_query *info)
105 {
106 	struct crypto_akcipher *tfm;
107 	struct public_key *pkey = params->key->payload.data[asym_crypto];
108 	char alg_name[CRYPTO_MAX_ALG_NAME];
109 	u8 *key, *ptr;
110 	int ret, len;
111 
112 	ret = software_key_determine_akcipher(params->encoding,
113 					      params->hash_algo,
114 					      pkey, alg_name);
115 	if (ret < 0)
116 		return ret;
117 
118 	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
119 	if (IS_ERR(tfm))
120 		return PTR_ERR(tfm);
121 
122 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
123 		      GFP_KERNEL);
124 	if (!key)
125 		goto error_free_tfm;
126 	memcpy(key, pkey->key, pkey->keylen);
127 	ptr = key + pkey->keylen;
128 	ptr = pkey_pack_u32(ptr, pkey->algo);
129 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
130 	memcpy(ptr, pkey->params, pkey->paramlen);
131 
132 	if (pkey->key_is_private)
133 		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
134 	else
135 		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
136 	if (ret < 0)
137 		goto error_free_key;
138 
139 	len = crypto_akcipher_maxsize(tfm);
140 	info->key_size = len * 8;
141 	info->max_data_size = len;
142 	info->max_sig_size = len;
143 	info->max_enc_size = len;
144 	info->max_dec_size = len;
145 	info->supported_ops = (KEYCTL_SUPPORTS_ENCRYPT |
146 			       KEYCTL_SUPPORTS_VERIFY);
147 	if (pkey->key_is_private)
148 		info->supported_ops |= (KEYCTL_SUPPORTS_DECRYPT |
149 					KEYCTL_SUPPORTS_SIGN);
150 	ret = 0;
151 
152 error_free_key:
153 	kfree(key);
154 error_free_tfm:
155 	crypto_free_akcipher(tfm);
156 	pr_devel("<==%s() = %d\n", __func__, ret);
157 	return ret;
158 }
159 
160 /*
161  * Do encryption, decryption and signing ops.
162  */
163 static int software_key_eds_op(struct kernel_pkey_params *params,
164 			       const void *in, void *out)
165 {
166 	const struct public_key *pkey = params->key->payload.data[asym_crypto];
167 	struct akcipher_request *req;
168 	struct crypto_akcipher *tfm;
169 	struct crypto_wait cwait;
170 	struct scatterlist in_sg, out_sg;
171 	char alg_name[CRYPTO_MAX_ALG_NAME];
172 	char *key, *ptr;
173 	int ret;
174 
175 	pr_devel("==>%s()\n", __func__);
176 
177 	ret = software_key_determine_akcipher(params->encoding,
178 					      params->hash_algo,
179 					      pkey, alg_name);
180 	if (ret < 0)
181 		return ret;
182 
183 	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
184 	if (IS_ERR(tfm))
185 		return PTR_ERR(tfm);
186 
187 	ret = -ENOMEM;
188 	req = akcipher_request_alloc(tfm, GFP_KERNEL);
189 	if (!req)
190 		goto error_free_tfm;
191 
192 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
193 		      GFP_KERNEL);
194 	if (!key)
195 		goto error_free_req;
196 
197 	memcpy(key, pkey->key, pkey->keylen);
198 	ptr = key + pkey->keylen;
199 	ptr = pkey_pack_u32(ptr, pkey->algo);
200 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
201 	memcpy(ptr, pkey->params, pkey->paramlen);
202 
203 	if (pkey->key_is_private)
204 		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
205 	else
206 		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
207 	if (ret)
208 		goto error_free_key;
209 
210 	sg_init_one(&in_sg, in, params->in_len);
211 	sg_init_one(&out_sg, out, params->out_len);
212 	akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
213 				   params->out_len);
214 	crypto_init_wait(&cwait);
215 	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
216 				      CRYPTO_TFM_REQ_MAY_SLEEP,
217 				      crypto_req_done, &cwait);
218 
219 	/* Perform the encryption calculation. */
220 	switch (params->op) {
221 	case kernel_pkey_encrypt:
222 		ret = crypto_akcipher_encrypt(req);
223 		break;
224 	case kernel_pkey_decrypt:
225 		ret = crypto_akcipher_decrypt(req);
226 		break;
227 	case kernel_pkey_sign:
228 		ret = crypto_akcipher_sign(req);
229 		break;
230 	default:
231 		BUG();
232 	}
233 
234 	ret = crypto_wait_req(ret, &cwait);
235 	if (ret == 0)
236 		ret = req->dst_len;
237 
238 error_free_key:
239 	kfree(key);
240 error_free_req:
241 	akcipher_request_free(req);
242 error_free_tfm:
243 	crypto_free_akcipher(tfm);
244 	pr_devel("<==%s() = %d\n", __func__, ret);
245 	return ret;
246 }
247 
248 /*
249  * Verify a signature using a public key.
250  */
251 int public_key_verify_signature(const struct public_key *pkey,
252 				const struct public_key_signature *sig)
253 {
254 	struct crypto_wait cwait;
255 	struct crypto_akcipher *tfm;
256 	struct akcipher_request *req;
257 	struct scatterlist src_sg[2];
258 	char alg_name[CRYPTO_MAX_ALG_NAME];
259 	char *key, *ptr;
260 	int ret;
261 
262 	pr_devel("==>%s()\n", __func__);
263 
264 	BUG_ON(!pkey);
265 	BUG_ON(!sig);
266 	BUG_ON(!sig->s);
267 
268 	ret = software_key_determine_akcipher(sig->encoding,
269 					      sig->hash_algo,
270 					      pkey, alg_name);
271 	if (ret < 0)
272 		return ret;
273 
274 	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
275 	if (IS_ERR(tfm))
276 		return PTR_ERR(tfm);
277 
278 	ret = -ENOMEM;
279 	req = akcipher_request_alloc(tfm, GFP_KERNEL);
280 	if (!req)
281 		goto error_free_tfm;
282 
283 	key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
284 		      GFP_KERNEL);
285 	if (!key)
286 		goto error_free_req;
287 
288 	memcpy(key, pkey->key, pkey->keylen);
289 	ptr = key + pkey->keylen;
290 	ptr = pkey_pack_u32(ptr, pkey->algo);
291 	ptr = pkey_pack_u32(ptr, pkey->paramlen);
292 	memcpy(ptr, pkey->params, pkey->paramlen);
293 
294 	if (pkey->key_is_private)
295 		ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
296 	else
297 		ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
298 	if (ret)
299 		goto error_free_key;
300 
301 	sg_init_table(src_sg, 2);
302 	sg_set_buf(&src_sg[0], sig->s, sig->s_size);
303 	sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
304 	akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
305 				   sig->digest_size);
306 	crypto_init_wait(&cwait);
307 	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
308 				      CRYPTO_TFM_REQ_MAY_SLEEP,
309 				      crypto_req_done, &cwait);
310 	ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
311 
312 error_free_key:
313 	kfree(key);
314 error_free_req:
315 	akcipher_request_free(req);
316 error_free_tfm:
317 	crypto_free_akcipher(tfm);
318 	pr_devel("<==%s() = %d\n", __func__, ret);
319 	if (WARN_ON_ONCE(ret > 0))
320 		ret = -EINVAL;
321 	return ret;
322 }
323 EXPORT_SYMBOL_GPL(public_key_verify_signature);
324 
325 static int public_key_verify_signature_2(const struct key *key,
326 					 const struct public_key_signature *sig)
327 {
328 	const struct public_key *pk = key->payload.data[asym_crypto];
329 	return public_key_verify_signature(pk, sig);
330 }
331 
332 /*
333  * Public key algorithm asymmetric key subtype
334  */
335 struct asymmetric_key_subtype public_key_subtype = {
336 	.owner			= THIS_MODULE,
337 	.name			= "public_key",
338 	.name_len		= sizeof("public_key") - 1,
339 	.describe		= public_key_describe,
340 	.destroy		= public_key_destroy,
341 	.query			= software_key_query,
342 	.eds_op			= software_key_eds_op,
343 	.verify_signature	= public_key_verify_signature_2,
344 };
345 EXPORT_SYMBOL_GPL(public_key_subtype);
346