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 #include <keys/system_keyring.h>
21 
22 #include "integrity.h"
23 
24 /*
25  * Request an asymmetric key.
26  */
27 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
28 {
29 	struct key *key;
30 	char name[12];
31 
32 	sprintf(name, "id:%08x", keyid);
33 
34 	pr_debug("key search: \"%s\"\n", name);
35 
36 	key = get_ima_blacklist_keyring();
37 	if (key) {
38 		key_ref_t kref;
39 
40 		kref = keyring_search(make_key_ref(key, 1),
41 				     &key_type_asymmetric, name);
42 		if (!IS_ERR(kref)) {
43 			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
44 			return ERR_PTR(-EKEYREJECTED);
45 		}
46 	}
47 
48 	if (keyring) {
49 		/* search in specific keyring */
50 		key_ref_t kref;
51 
52 		kref = keyring_search(make_key_ref(keyring, 1),
53 				      &key_type_asymmetric, name);
54 		if (IS_ERR(kref))
55 			key = ERR_CAST(kref);
56 		else
57 			key = key_ref_to_ptr(kref);
58 	} else {
59 		key = request_key(&key_type_asymmetric, name, NULL);
60 	}
61 
62 	if (IS_ERR(key)) {
63 		pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
64 				   name, PTR_ERR(key));
65 		switch (PTR_ERR(key)) {
66 			/* Hide some search errors */
67 		case -EACCES:
68 		case -ENOTDIR:
69 		case -EAGAIN:
70 			return ERR_PTR(-ENOKEY);
71 		default:
72 			return key;
73 		}
74 	}
75 
76 	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
77 
78 	return key;
79 }
80 
81 int asymmetric_verify(struct key *keyring, const char *sig,
82 		      int siglen, const char *data, int datalen)
83 {
84 	struct public_key_signature pks;
85 	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
86 	struct key *key;
87 	int ret = -ENOMEM;
88 
89 	if (siglen <= sizeof(*hdr))
90 		return -EBADMSG;
91 
92 	siglen -= sizeof(*hdr);
93 
94 	if (siglen != __be16_to_cpu(hdr->sig_size))
95 		return -EBADMSG;
96 
97 	if (hdr->hash_algo >= PKEY_HASH__LAST)
98 		return -ENOPKG;
99 
100 	key = request_asymmetric_key(keyring, __be32_to_cpu(hdr->keyid));
101 	if (IS_ERR(key))
102 		return PTR_ERR(key);
103 
104 	memset(&pks, 0, sizeof(pks));
105 
106 	pks.pkey_algo = PKEY_ALGO_RSA;
107 	pks.pkey_hash_algo = hdr->hash_algo;
108 	pks.digest = (u8 *)data;
109 	pks.digest_size = datalen;
110 	pks.s = hdr->sig;
111 	pks.s_size = siglen;
112 	ret = verify_signature(key, &pks);
113 	key_put(key);
114 	pr_debug("%s() = %d\n", __func__, ret);
115 	return ret;
116 }
117