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/ratelimit.h>
17 #include <linux/key-type.h>
18 #include <crypto/public_key.h>
19 #include <keys/asymmetric-type.h>
20 
21 #include "integrity.h"
22 
23 /*
24  * Request an asymmetric key.
25  */
26 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
27 {
28 	struct key *key;
29 	char name[12];
30 
31 	sprintf(name, "id:%08x", keyid);
32 
33 	pr_debug("key search: \"%s\"\n", name);
34 
35 	if (keyring) {
36 		/* search in specific keyring */
37 		key_ref_t kref;
38 		kref = keyring_search(make_key_ref(keyring, 1),
39 				      &key_type_asymmetric, name);
40 		if (IS_ERR(kref))
41 			key = ERR_CAST(kref);
42 		else
43 			key = key_ref_to_ptr(kref);
44 	} else {
45 		key = request_key(&key_type_asymmetric, name, NULL);
46 	}
47 
48 	if (IS_ERR(key)) {
49 		pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
50 				   name, PTR_ERR(key));
51 		switch (PTR_ERR(key)) {
52 			/* Hide some search errors */
53 		case -EACCES:
54 		case -ENOTDIR:
55 		case -EAGAIN:
56 			return ERR_PTR(-ENOKEY);
57 		default:
58 			return key;
59 		}
60 	}
61 
62 	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
63 
64 	return key;
65 }
66 
67 int asymmetric_verify(struct key *keyring, const char *sig,
68 		      int siglen, const char *data, int datalen)
69 {
70 	struct public_key_signature pks;
71 	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
72 	struct key *key;
73 	int ret = -ENOMEM;
74 
75 	if (siglen <= sizeof(*hdr))
76 		return -EBADMSG;
77 
78 	siglen -= sizeof(*hdr);
79 
80 	if (siglen != __be16_to_cpu(hdr->sig_size))
81 		return -EBADMSG;
82 
83 	if (hdr->hash_algo >= PKEY_HASH__LAST)
84 		return -ENOPKG;
85 
86 	key = request_asymmetric_key(keyring, __be32_to_cpu(hdr->keyid));
87 	if (IS_ERR(key))
88 		return PTR_ERR(key);
89 
90 	memset(&pks, 0, sizeof(pks));
91 
92 	pks.pkey_hash_algo = hdr->hash_algo;
93 	pks.digest = (u8 *)data;
94 	pks.digest_size = datalen;
95 	pks.nr_mpi = 1;
96 	pks.rsa.s = mpi_read_raw_data(hdr->sig, siglen);
97 
98 	if (pks.rsa.s)
99 		ret = verify_signature(key, &pks);
100 
101 	mpi_free(pks.rsa.s);
102 	key_put(key);
103 	pr_debug("%s() = %d\n", __func__, ret);
104 	return ret;
105 }
106