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Dmitry Kasatkin051dbb92011-10-14 15:25:16 +03001/*
2 * Copyright (C) 2011 Nokia Corporation
3 * Copyright (C) 2011 Intel Corporation
4 *
5 * Author:
6 * Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
7 * <dmitry.kasatkin@intel.com>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation, version 2 of the License.
12 *
13 * File: sign.c
14 * implements signature (RSA) verification
15 * pkcs decoding is based on LibTomCrypt code
16 */
17
18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20#include <linux/err.h>
21#include <linux/module.h>
22#include <linux/slab.h>
23#include <linux/key.h>
24#include <linux/crypto.h>
25#include <crypto/hash.h>
26#include <crypto/sha.h>
27#include <keys/user-type.h>
28#include <linux/mpi.h>
29#include <linux/digsig.h>
30
31static struct crypto_shash *shash;
32
33static int pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
34 unsigned long msglen,
35 unsigned long modulus_bitlen,
36 unsigned char *out,
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020037 unsigned long *outlen)
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030038{
39 unsigned long modulus_len, ps_len, i;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030040
41 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
42
43 /* test message size */
44 if ((msglen > modulus_len) || (modulus_len < 11))
45 return -EINVAL;
46
47 /* separate encoded message */
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020048 if ((msg[0] != 0x00) || (msg[1] != (unsigned char)1))
49 return -EINVAL;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030050
51 for (i = 2; i < modulus_len - 1; i++)
52 if (msg[i] != 0xFF)
53 break;
54
55 /* separator check */
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020056 if (msg[i] != 0)
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030057 /* There was no octet with hexadecimal value 0x00
58 to separate ps from m. */
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020059 return -EINVAL;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030060
61 ps_len = i - 2;
62
63 if (*outlen < (msglen - (2 + ps_len + 1))) {
64 *outlen = msglen - (2 + ps_len + 1);
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020065 return -EOVERFLOW;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030066 }
67
68 *outlen = (msglen - (2 + ps_len + 1));
69 memcpy(out, &msg[2 + ps_len + 1], *outlen);
70
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020071 return 0;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030072}
73
74/*
75 * RSA Signature verification with public key
76 */
77static int digsig_verify_rsa(struct key *key,
78 const char *sig, int siglen,
79 const char *h, int hlen)
80{
81 int err = -EINVAL;
82 unsigned long len;
83 unsigned long mlen, mblen;
84 unsigned nret, l;
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +020085 int head, i;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030086 unsigned char *out1 = NULL, *out2 = NULL;
87 MPI in = NULL, res = NULL, pkey[2];
88 uint8_t *p, *datap, *endp;
89 struct user_key_payload *ukp;
90 struct pubkey_hdr *pkh;
91
92 down_read(&key->sem);
93 ukp = key->payload.data;
Dmitry Kasatkinf58a0812012-01-26 19:13:25 +020094
95 if (ukp->datalen < sizeof(*pkh))
96 goto err1;
97
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +030098 pkh = (struct pubkey_hdr *)ukp->data;
99
100 if (pkh->version != 1)
101 goto err1;
102
103 if (pkh->algo != PUBKEY_ALGO_RSA)
104 goto err1;
105
106 if (pkh->nmpi != 2)
107 goto err1;
108
109 datap = pkh->mpi;
Dmitry Kasatkinf58a0812012-01-26 19:13:25 +0200110 endp = ukp->data + ukp->datalen;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300111
Dmitry Kasatkin86f8bed2012-01-26 19:13:24 +0200112 err = -ENOMEM;
113
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300114 for (i = 0; i < pkh->nmpi; i++) {
115 unsigned int remaining = endp - datap;
116 pkey[i] = mpi_read_from_buffer(datap, &remaining);
Dmitry Kasatkin86f8bed2012-01-26 19:13:24 +0200117 if (!pkey[i])
118 goto err;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300119 datap += remaining;
120 }
121
122 mblen = mpi_get_nbits(pkey[0]);
123 mlen = (mblen + 7)/8;
124
Dmitry Kasatkinf58a0812012-01-26 19:13:25 +0200125 if (mlen == 0)
126 goto err;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300127
128 out1 = kzalloc(mlen, GFP_KERNEL);
129 if (!out1)
130 goto err;
131
132 out2 = kzalloc(mlen, GFP_KERNEL);
133 if (!out2)
134 goto err;
135
136 nret = siglen;
137 in = mpi_read_from_buffer(sig, &nret);
138 if (!in)
139 goto err;
140
141 res = mpi_alloc(mpi_get_nlimbs(in) * 2);
142 if (!res)
143 goto err;
144
145 err = mpi_powm(res, in, pkey[1], pkey[0]);
146 if (err)
147 goto err;
148
149 if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
150 err = -EINVAL;
151 goto err;
152 }
153
154 p = mpi_get_buffer(res, &l, NULL);
155 if (!p) {
156 err = -EINVAL;
157 goto err;
158 }
159
160 len = mlen;
161 head = len - l;
162 memset(out1, 0, head);
163 memcpy(out1 + head, p, l);
164
YOSHIFUJI Hideakie35e5b22013-01-25 16:54:20 +0200165 kfree(p);
166
Dmitry Kasatkinb35e2862012-01-26 19:13:26 +0200167 err = pkcs_1_v1_5_decode_emsa(out1, len, mblen, out2, &len);
Dmitry Kasatkinb57beb22012-09-12 13:26:55 +0300168 if (err)
169 goto err;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300170
Dmitry Kasatkinb57beb22012-09-12 13:26:55 +0300171 if (len != hlen || memcmp(out2, h, hlen))
172 err = -EINVAL;
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300173
174err:
175 mpi_free(in);
176 mpi_free(res);
177 kfree(out1);
178 kfree(out2);
Dmitry Kasatkin86f8bed2012-01-26 19:13:24 +0200179 while (--i >= 0)
180 mpi_free(pkey[i]);
Dmitry Kasatkin051dbb92011-10-14 15:25:16 +0300181err1:
182 up_read(&key->sem);
183
184 return err;
185}
186
187/**
188 * digsig_verify() - digital signature verification with public key
189 * @keyring: keyring to search key in
190 * @sig: digital signature
191 * @sigen: length of the signature
192 * @data: data
193 * @datalen: length of the data
194 * @return: 0 on success, -EINVAL otherwise
195 *
196 * Verifies data integrity against digital signature.
197 * Currently only RSA is supported.
198 * Normally hash of the content is used as a data for this function.
199 *
200 */
201int digsig_verify(struct key *keyring, const char *sig, int siglen,
202 const char *data, int datalen)
203{
204 int err = -ENOMEM;
205 struct signature_hdr *sh = (struct signature_hdr *)sig;
206 struct shash_desc *desc = NULL;
207 unsigned char hash[SHA1_DIGEST_SIZE];
208 struct key *key;
209 char name[20];
210
211 if (siglen < sizeof(*sh) + 2)
212 return -EINVAL;
213
214 if (sh->algo != PUBKEY_ALGO_RSA)
215 return -ENOTSUPP;
216
217 sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
218
219 if (keyring) {
220 /* search in specific keyring */
221 key_ref_t kref;
222 kref = keyring_search(make_key_ref(keyring, 1UL),
223 &key_type_user, name);
224 if (IS_ERR(kref))
225 key = ERR_PTR(PTR_ERR(kref));
226 else
227 key = key_ref_to_ptr(kref);
228 } else {
229 key = request_key(&key_type_user, name, NULL);
230 }
231 if (IS_ERR(key)) {
232 pr_err("key not found, id: %s\n", name);
233 return PTR_ERR(key);
234 }
235
236 desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
237 GFP_KERNEL);
238 if (!desc)
239 goto err;
240
241 desc->tfm = shash;
242 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
243
244 crypto_shash_init(desc);
245 crypto_shash_update(desc, data, datalen);
246 crypto_shash_update(desc, sig, sizeof(*sh));
247 crypto_shash_final(desc, hash);
248
249 kfree(desc);
250
251 /* pass signature mpis address */
252 err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
253 hash, sizeof(hash));
254
255err:
256 key_put(key);
257
258 return err ? -EINVAL : 0;
259}
260EXPORT_SYMBOL_GPL(digsig_verify);
261
262static int __init digsig_init(void)
263{
264 shash = crypto_alloc_shash("sha1", 0, 0);
265 if (IS_ERR(shash)) {
266 pr_err("shash allocation failed\n");
267 return PTR_ERR(shash);
268 }
269
270 return 0;
271
272}
273
274static void __exit digsig_cleanup(void)
275{
276 crypto_free_shash(shash);
277}
278
279module_init(digsig_init);
280module_exit(digsig_cleanup);
281
282MODULE_LICENSE("GPL");