projects/linux·blob uaccess-cleanups · refs

244 lines · 4.9 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2011 Nokia Corporation
4 * Copyright (C) 2011 Intel Corporation
5 *
6 * Author:
7 * Dmitry Kasatkin <[email protected]>
8 * <[email protected]>
9 *
10 * File: sign.c
11 * implements signature (RSA) verification
12 * pkcs decoding is based on LibTomCrypt code
13 */
14
15#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16
17#include <linux/err.h>
18#include <linux/module.h>
19#include <linux/slab.h>
20#include <linux/key.h>
21#include <crypto/sha1.h>
22#include <keys/user-type.h>
23#include <linux/mpi.h>
24#include <linux/digsig.h>
25
26static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
27 unsigned long msglen,
28 unsigned long modulus_bitlen,
29 unsigned long *outlen)
30{
31 unsigned long modulus_len, ps_len, i;
32
33 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
34
35 /* test message size */
36 if ((msglen > modulus_len) || (modulus_len < 11))
37 return NULL;
38
39 /* separate encoded message */
40 if (msg[0] != 0x00 || msg[1] != 0x01)
41 return NULL;
42
43 for (i = 2; i < modulus_len - 1; i++)
44 if (msg[i] != 0xFF)
45 break;
46
47 /* separator check */
48 if (msg[i] != 0)
49 /* There was no octet with hexadecimal value 0x00
50 to separate ps from m. */
51 return NULL;
52
53 ps_len = i - 2;
54
55 *outlen = (msglen - (2 + ps_len + 1));
56
57 return msg + 2 + ps_len + 1;
58}
59
60/*
61 * RSA Signature verification with public key
62 */
63static int digsig_verify_rsa(struct key *key,
64 const char *sig, int siglen,
65 const char *h, int hlen)
66{
67 int err = -EINVAL;
68 unsigned long len;
69 unsigned long mlen, mblen;
70 unsigned nret, l;
71 int head, i;
72 unsigned char *out1 = NULL;
73 const char *m;
74 MPI in = NULL, res = NULL, pkey[2];
75 uint8_t *p, *datap;
76 const uint8_t *endp;
77 const struct user_key_payload *ukp;
78 struct pubkey_hdr *pkh;
79
80 down_read(&key->sem);
81 ukp = user_key_payload_locked(key);
82
83 if (!ukp) {
84 /* key was revoked before we acquired its semaphore */
85 err = -EKEYREVOKED;
86 goto err1;
87 }
88
89 if (ukp->datalen < sizeof(*pkh))
90 goto err1;
91
92 pkh = (struct pubkey_hdr *)ukp->data;
93
94 if (pkh->version != 1)
95 goto err1;
96
97 if (pkh->algo != PUBKEY_ALGO_RSA)
98 goto err1;
99
100 if (pkh->nmpi != 2)
101 goto err1;
102
103 datap = pkh->mpi;
104 endp = ukp->data + ukp->datalen;
105
106 for (i = 0; i < pkh->nmpi; i++) {
107 unsigned int remaining = endp - datap;
108 pkey[i] = mpi_read_from_buffer(datap, &remaining);
109 if (IS_ERR(pkey[i])) {
110 err = PTR_ERR(pkey[i]);
111 goto err;
112 }
113 datap += remaining;
114 }
115
116 mblen = mpi_get_nbits(pkey[0]);
117 mlen = DIV_ROUND_UP(mblen, 8);
118
119 if (mlen == 0) {
120 err = -EINVAL;
121 goto err;
122 }
123
124 err = -ENOMEM;
125
126 out1 = kzalloc(mlen, GFP_KERNEL);
127 if (!out1)
128 goto err;
129
130 nret = siglen;
131 in = mpi_read_from_buffer(sig, &nret);
132 if (IS_ERR(in)) {
133 err = PTR_ERR(in);
134 goto err;
135 }
136
137 res = mpi_alloc(mpi_get_nlimbs(in) * 2);
138 if (!res)
139 goto err;
140
141 err = mpi_powm(res, in, pkey[1], pkey[0]);
142 if (err)
143 goto err;
144
145 if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
146 err = -EINVAL;
147 goto err;
148 }
149
150 p = mpi_get_buffer(res, &l, NULL);
151 if (!p) {
152 err = -EINVAL;
153 goto err;
154 }
155
156 len = mlen;
157 head = len - l;
158 memcpy(out1 + head, p, l);
159
160 kfree(p);
161
162 m = pkcs_1_v1_5_decode_emsa(out1, len, mblen, &len);
163
164 if (!m || len != hlen || memcmp(m, h, hlen))
165 err = -EINVAL;
166
167err:
168 mpi_free(in);
169 mpi_free(res);
170 kfree(out1);
171 while (--i >= 0)
172 mpi_free(pkey[i]);
173err1:
174 up_read(&key->sem);
175
176 return err;
177}
178
179/**
180 * digsig_verify() - digital signature verification with public key
181 * @keyring: keyring to search key in
182 * @sig: digital signature
183 * @siglen: length of the signature
184 * @data: data
185 * @datalen: length of the data
186 *
187 * Returns 0 on success, -EINVAL otherwise
188 *
189 * Verifies data integrity against digital signature.
190 * Currently only RSA is supported.
191 * Normally hash of the content is used as a data for this function.
192 *
193 */
194int digsig_verify(struct key *keyring, const char *sig, int siglen,
195 const char *data, int datalen)
196{
197 struct signature_hdr *sh = (struct signature_hdr *)sig;
198 struct sha1_ctx ctx;
199 unsigned char hash[SHA1_DIGEST_SIZE];
200 struct key *key;
201 char name[20];
202 int err;
203
204 if (siglen < sizeof(*sh) + 2)
205 return -EINVAL;
206
207 if (sh->algo != PUBKEY_ALGO_RSA)
208 return -ENOTSUPP;
209
210 sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
211
212 if (keyring) {
213 /* search in specific keyring */
214 key_ref_t kref;
215 kref = keyring_search(make_key_ref(keyring, 1UL),
216 &key_type_user, name, true);
217 if (IS_ERR(kref))
218 key = ERR_CAST(kref);
219 else
220 key = key_ref_to_ptr(kref);
221 } else {
222 key = request_key(&key_type_user, name, NULL);
223 }
224 if (IS_ERR(key)) {
225 pr_err("key not found, id: %s\n", name);
226 return PTR_ERR(key);
227 }
228
229 sha1_init(&ctx);
230 sha1_update(&ctx, data, datalen);
231 sha1_update(&ctx, sig, sizeof(*sh));
232 sha1_final(&ctx, hash);
233
234 /* pass signature mpis address */
235 err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
236 hash, sizeof(hash));
237
238 key_put(key);
239
240 return err ? -EINVAL : 0;
241}
242EXPORT_SYMBOL_GPL(digsig_verify);
243
244MODULE_LICENSE("GPL");