Root/lib/digsig.c

Source at commit b386be689295730688885552666ea40b2e639b14 created 8 years 11 months ago.
By Maarten ter Huurne, Revert "MIPS: JZ4740: reset: Initialize hibernate wakeup counters."
1/*
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,
37            unsigned long *outlen)
38{
39    unsigned long modulus_len, ps_len, i;
40
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 */
48    if ((msg[0] != 0x00) || (msg[1] != (unsigned char)1))
49        return -EINVAL;
50
51    for (i = 2; i < modulus_len - 1; i++)
52        if (msg[i] != 0xFF)
53            break;
54
55    /* separator check */
56    if (msg[i] != 0)
57        /* There was no octet with hexadecimal value 0x00
58        to separate ps from m. */
59        return -EINVAL;
60
61    ps_len = i - 2;
62
63    if (*outlen < (msglen - (2 + ps_len + 1))) {
64        *outlen = msglen - (2 + ps_len + 1);
65        return -EOVERFLOW;
66    }
67
68    *outlen = (msglen - (2 + ps_len + 1));
69    memcpy(out, &msg[2 + ps_len + 1], *outlen);
70
71    return 0;
72}
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;
85    int head, i;
86    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;
94
95    if (ukp->datalen < sizeof(*pkh))
96        goto err1;
97
98    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;
110    endp = ukp->data + ukp->datalen;
111
112    err = -ENOMEM;
113
114    for (i = 0; i < pkh->nmpi; i++) {
115        unsigned int remaining = endp - datap;
116        pkey[i] = mpi_read_from_buffer(datap, &remaining);
117        if (!pkey[i])
118            goto err;
119        datap += remaining;
120    }
121
122    mblen = mpi_get_nbits(pkey[0]);
123    mlen = (mblen + 7)/8;
124
125    if (mlen == 0)
126        goto err;
127
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
165    err = pkcs_1_v1_5_decode_emsa(out1, len, mblen, out2, &len);
166
167    if (!err && len == hlen)
168        err = memcmp(out2, h, hlen);
169
170err:
171    mpi_free(in);
172    mpi_free(res);
173    kfree(out1);
174    kfree(out2);
175    while (--i >= 0)
176        mpi_free(pkey[i]);
177err1:
178    up_read(&key->sem);
179
180    return err;
181}
182
183/**
184 * digsig_verify() - digital signature verification with public key
185 * @keyring: keyring to search key in
186 * @sig: digital signature
187 * @sigen: length of the signature
188 * @data: data
189 * @datalen: length of the data
190 * @return: 0 on success, -EINVAL otherwise
191 *
192 * Verifies data integrity against digital signature.
193 * Currently only RSA is supported.
194 * Normally hash of the content is used as a data for this function.
195 *
196 */
197int digsig_verify(struct key *keyring, const char *sig, int siglen,
198                        const char *data, int datalen)
199{
200    int err = -ENOMEM;
201    struct signature_hdr *sh = (struct signature_hdr *)sig;
202    struct shash_desc *desc = NULL;
203    unsigned char hash[SHA1_DIGEST_SIZE];
204    struct key *key;
205    char name[20];
206
207    if (siglen < sizeof(*sh) + 2)
208        return -EINVAL;
209
210    if (sh->algo != PUBKEY_ALGO_RSA)
211        return -ENOTSUPP;
212
213    sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
214
215    if (keyring) {
216        /* search in specific keyring */
217        key_ref_t kref;
218        kref = keyring_search(make_key_ref(keyring, 1UL),
219                        &key_type_user, name);
220        if (IS_ERR(kref))
221            key = ERR_PTR(PTR_ERR(kref));
222        else
223            key = key_ref_to_ptr(kref);
224    } else {
225        key = request_key(&key_type_user, name, NULL);
226    }
227    if (IS_ERR(key)) {
228        pr_err("key not found, id: %s\n", name);
229        return PTR_ERR(key);
230    }
231
232    desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
233               GFP_KERNEL);
234    if (!desc)
235        goto err;
236
237    desc->tfm = shash;
238    desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
239
240    crypto_shash_init(desc);
241    crypto_shash_update(desc, data, datalen);
242    crypto_shash_update(desc, sig, sizeof(*sh));
243    crypto_shash_final(desc, hash);
244
245    kfree(desc);
246
247    /* pass signature mpis address */
248    err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
249                 hash, sizeof(hash));
250
251err:
252    key_put(key);
253
254    return err ? -EINVAL : 0;
255}
256EXPORT_SYMBOL_GPL(digsig_verify);
257
258static int __init digsig_init(void)
259{
260    shash = crypto_alloc_shash("sha1", 0, 0);
261    if (IS_ERR(shash)) {
262        pr_err("shash allocation failed\n");
263        return PTR_ERR(shash);
264    }
265
266    return 0;
267
268}
269
270static void __exit digsig_cleanup(void)
271{
272    crypto_free_shash(shash);
273}
274
275module_init(digsig_init);
276module_exit(digsig_cleanup);
277
278MODULE_LICENSE("GPL");
279

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