1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2013 Intel Corporation
4  *
5  * Author:
6  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
7  */
8 
9 #include <linux/err.h>
10 #include <linux/ratelimit.h>
11 #include <linux/key-type.h>
12 #include <crypto/public_key.h>
13 #include <crypto/hash_info.h>
14 #include <keys/asymmetric-type.h>
15 #include <keys/system_keyring.h>
16 
17 #include "integrity.h"
18 
19 /*
20  * Request an asymmetric key.
21  */
22 static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
23 {
24 	struct key *key;
25 	char name[12];
26 
27 	sprintf(name, "id:%08x", keyid);
28 
29 	pr_debug("key search: \"%s\"\n", name);
30 
31 	key = get_ima_blacklist_keyring();
32 	if (key) {
33 		key_ref_t kref;
34 
35 		kref = keyring_search(make_key_ref(key, 1),
36 				      &key_type_asymmetric, name, true);
37 		if (!IS_ERR(kref)) {
38 			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
39 			return ERR_PTR(-EKEYREJECTED);
40 		}
41 	}
42 
43 	if (keyring) {
44 		/* search in specific keyring */
45 		key_ref_t kref;
46 
47 		kref = keyring_search(make_key_ref(keyring, 1),
48 				      &key_type_asymmetric, name, true);
49 		if (IS_ERR(kref))
50 			key = ERR_CAST(kref);
51 		else
52 			key = key_ref_to_ptr(kref);
53 	} else {
54 		key = request_key(&key_type_asymmetric, name, NULL);
55 	}
56 
57 	if (IS_ERR(key)) {
58 		pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
59 				   name, PTR_ERR(key));
60 		switch (PTR_ERR(key)) {
61 			/* Hide some search errors */
62 		case -EACCES:
63 		case -ENOTDIR:
64 		case -EAGAIN:
65 			return ERR_PTR(-ENOKEY);
66 		default:
67 			return key;
68 		}
69 	}
70 
71 	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
72 
73 	return key;
74 }
75 
76 int asymmetric_verify(struct key *keyring, const char *sig,
77 		      int siglen, const char *data, int datalen)
78 {
79 	struct public_key_signature pks;
80 	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
81 	struct key *key;
82 	int ret;
83 
84 	if (siglen <= sizeof(*hdr))
85 		return -EBADMSG;
86 
87 	siglen -= sizeof(*hdr);
88 
89 	if (siglen != be16_to_cpu(hdr->sig_size))
90 		return -EBADMSG;
91 
92 	if (hdr->hash_algo >= HASH_ALGO__LAST)
93 		return -ENOPKG;
94 
95 	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
96 	if (IS_ERR(key))
97 		return PTR_ERR(key);
98 
99 	memset(&pks, 0, sizeof(pks));
100 
101 	pks.hash_algo = hash_algo_name[hdr->hash_algo];
102 	switch (hdr->hash_algo) {
103 	case HASH_ALGO_STREEBOG_256:
104 	case HASH_ALGO_STREEBOG_512:
105 		/* EC-RDSA and Streebog should go together. */
106 		pks.pkey_algo = "ecrdsa";
107 		pks.encoding = "raw";
108 		break;
109 	case HASH_ALGO_SM3_256:
110 		/* SM2 and SM3 should go together. */
111 		pks.pkey_algo = "sm2";
112 		pks.encoding = "raw";
113 		break;
114 	default:
115 		pks.pkey_algo = "rsa";
116 		pks.encoding = "pkcs1";
117 		break;
118 	}
119 	pks.digest = (u8 *)data;
120 	pks.digest_size = datalen;
121 	pks.s = hdr->sig;
122 	pks.s_size = siglen;
123 	ret = verify_signature(key, &pks);
124 	key_put(key);
125 	pr_debug("%s() = %d\n", __func__, ret);
126 	return ret;
127 }
128 
129 /**
130  * integrity_kernel_module_request - prevent crypto-pkcs1pad(rsa,*) requests
131  * @kmod_name: kernel module name
132  *
133  * We have situation, when public_key_verify_signature() in case of RSA
134  * algorithm use alg_name to store internal information in order to
135  * construct an algorithm on the fly, but crypto_larval_lookup() will try
136  * to use alg_name in order to load kernel module with same name.
137  * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
138  * we are safe to fail such module request from crypto_larval_lookup().
139  *
140  * In this way we prevent modprobe execution during digsig verification
141  * and avoid possible deadlock if modprobe and/or it's dependencies
142  * also signed with digsig.
143  */
144 int integrity_kernel_module_request(char *kmod_name)
145 {
146 	if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
147 		return -EINVAL;
148 
149 	return 0;
150 }
151