1 /*
2  * Copyright (C) 2013 Intel Corporation
3  *
4  * Author:
5  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation, version 2 of the License.
10  *
11  */
12 
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14 
15 #include <linux/err.h>
16 #include <linux/key-type.h>
17 #include <crypto/public_key.h>
18 #include <keys/asymmetric-type.h>
19 
20 #include "integrity.h"
21 
22 /*
23  * Request an asymmetric key.
24  */
25 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
26 {
27 	struct key *key;
28 	char name[12];
29 
30 	sprintf(name, "id:%x", keyid);
31 
32 	pr_debug("key search: \"%s\"\n", name);
33 
34 	if (keyring) {
35 		/* search in specific keyring */
36 		key_ref_t kref;
37 		kref = keyring_search(make_key_ref(keyring, 1),
38 				      &key_type_asymmetric, name);
39 		if (IS_ERR(kref))
40 			key = ERR_CAST(kref);
41 		else
42 			key = key_ref_to_ptr(kref);
43 	} else {
44 		key = request_key(&key_type_asymmetric, name, NULL);
45 	}
46 
47 	if (IS_ERR(key)) {
48 		pr_warn("Request for unknown key '%s' err %ld\n",
49 			name, PTR_ERR(key));
50 		switch (PTR_ERR(key)) {
51 			/* Hide some search errors */
52 		case -EACCES:
53 		case -ENOTDIR:
54 		case -EAGAIN:
55 			return ERR_PTR(-ENOKEY);
56 		default:
57 			return key;
58 		}
59 	}
60 
61 	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
62 
63 	return key;
64 }
65 
66 int asymmetric_verify(struct key *keyring, const char *sig,
67 		      int siglen, const char *data, int datalen)
68 {
69 	struct public_key_signature pks;
70 	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
71 	struct key *key;
72 	int ret = -ENOMEM;
73 
74 	if (siglen <= sizeof(*hdr))
75 		return -EBADMSG;
76 
77 	siglen -= sizeof(*hdr);
78 
79 	if (siglen != __be16_to_cpu(hdr->sig_size))
80 		return -EBADMSG;
81 
82 	if (hdr->hash_algo >= PKEY_HASH__LAST)
83 		return -ENOPKG;
84 
85 	key = request_asymmetric_key(keyring, __be32_to_cpu(hdr->keyid));
86 	if (IS_ERR(key))
87 		return PTR_ERR(key);
88 
89 	memset(&pks, 0, sizeof(pks));
90 
91 	pks.pkey_hash_algo = hdr->hash_algo;
92 	pks.digest = (u8 *)data;
93 	pks.digest_size = datalen;
94 	pks.nr_mpi = 1;
95 	pks.rsa.s = mpi_read_raw_data(hdr->sig, siglen);
96 
97 	if (pks.rsa.s)
98 		ret = verify_signature(key, &pks);
99 
100 	mpi_free(pks.rsa.s);
101 	key_put(key);
102 	pr_debug("%s() = %d\n", __func__, ret);
103 	return ret;
104 }
105