2 * Copyright (C) 2011 Nokia Corporation
3 * Copyright (C) 2011 Intel Corporation
6 * Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
7 * <dmitry.kasatkin@intel.com>
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.
14 * implements signature (RSA) verification
15 * pkcs decoding is based on LibTomCrypt code
18 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
31 static struct crypto_shash *shash;
33 static int pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
35 unsigned long modulus_bitlen,
37 unsigned long *outlen,
40 unsigned long modulus_len, ps_len, i;
43 /* default to invalid packet */
46 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
48 /* test message size */
49 if ((msglen > modulus_len) || (modulus_len < 11))
52 /* separate encoded message */
53 if ((msg[0] != 0x00) || (msg[1] != (unsigned char)1)) {
58 for (i = 2; i < modulus_len - 1; i++)
64 /* There was no octet with hexadecimal value 0x00
65 to separate ps from m. */
72 if (*outlen < (msglen - (2 + ps_len + 1))) {
73 *outlen = msglen - (2 + ps_len + 1);
78 *outlen = (msglen - (2 + ps_len + 1));
79 memcpy(out, &msg[2 + ps_len + 1], *outlen);
89 * RSA Signature verification with public key
91 static int digsig_verify_rsa(struct key *key,
92 const char *sig, int siglen,
93 const char *h, int hlen)
97 unsigned long mlen, mblen;
100 unsigned char *out1 = NULL, *out2 = NULL;
101 MPI in = NULL, res = NULL, pkey[2];
102 uint8_t *p, *datap, *endp;
103 struct user_key_payload *ukp;
104 struct pubkey_hdr *pkh;
106 down_read(&key->sem);
107 ukp = key->payload.data;
109 if (ukp->datalen < sizeof(*pkh))
112 pkh = (struct pubkey_hdr *)ukp->data;
114 if (pkh->version != 1)
117 if (pkh->algo != PUBKEY_ALGO_RSA)
124 endp = ukp->data + ukp->datalen;
126 for (i = 0; i < pkh->nmpi; i++) {
127 unsigned int remaining = endp - datap;
128 pkey[i] = mpi_read_from_buffer(datap, &remaining);
132 mblen = mpi_get_nbits(pkey[0]);
133 mlen = (mblen + 7)/8;
138 out1 = kzalloc(mlen, GFP_KERNEL);
142 out2 = kzalloc(mlen, GFP_KERNEL);
147 in = mpi_read_from_buffer(sig, &nret);
151 res = mpi_alloc(mpi_get_nlimbs(in) * 2);
155 err = mpi_powm(res, in, pkey[1], pkey[0]);
159 if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
164 p = mpi_get_buffer(res, &l, NULL);
172 memset(out1, 0, head);
173 memcpy(out1 + head, p, l);
176 pkcs_1_v1_5_decode_emsa(out1, len, mblen, out2, &len, &valid);
178 if (valid && len == hlen)
179 err = memcmp(out2, h, hlen);
195 * digsig_verify() - digital signature verification with public key
196 * @keyring: keyring to search key in
197 * @sig: digital signature
198 * @sigen: length of the signature
200 * @datalen: length of the data
201 * @return: 0 on success, -EINVAL otherwise
203 * Verifies data integrity against digital signature.
204 * Currently only RSA is supported.
205 * Normally hash of the content is used as a data for this function.
208 int digsig_verify(struct key *keyring, const char *sig, int siglen,
209 const char *data, int datalen)
212 struct signature_hdr *sh = (struct signature_hdr *)sig;
213 struct shash_desc *desc = NULL;
214 unsigned char hash[SHA1_DIGEST_SIZE];
218 if (siglen < sizeof(*sh) + 2)
221 if (sh->algo != PUBKEY_ALGO_RSA)
224 sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
227 /* search in specific keyring */
229 kref = keyring_search(make_key_ref(keyring, 1UL),
230 &key_type_user, name);
232 key = ERR_PTR(PTR_ERR(kref));
234 key = key_ref_to_ptr(kref);
236 key = request_key(&key_type_user, name, NULL);
239 pr_err("key not found, id: %s\n", name);
243 desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
249 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
251 crypto_shash_init(desc);
252 crypto_shash_update(desc, data, datalen);
253 crypto_shash_update(desc, sig, sizeof(*sh));
254 crypto_shash_final(desc, hash);
258 /* pass signature mpis address */
259 err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
265 return err ? -EINVAL : 0;
267 EXPORT_SYMBOL_GPL(digsig_verify);
269 static int __init digsig_init(void)
271 shash = crypto_alloc_shash("sha1", 0, 0);
273 pr_err("shash allocation failed\n");
274 return PTR_ERR(shash);
281 static void __exit digsig_cleanup(void)
283 crypto_free_shash(shash);
286 module_init(digsig_init);
287 module_exit(digsig_cleanup);
289 MODULE_LICENSE("GPL");