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  */
request_asymmetric_key(struct key * keyring,uint32_t keyid)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 		if (keyring)
59 			pr_err_ratelimited("Request for unknown key '%s' in '%s' keyring. err %ld\n",
60 					   name, keyring->description,
61 					   PTR_ERR(key));
62 		else
63 			pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
64 					   name, PTR_ERR(key));
65 
66 		switch (PTR_ERR(key)) {
67 			/* Hide some search errors */
68 		case -EACCES:
69 		case -ENOTDIR:
70 		case -EAGAIN:
71 			return ERR_PTR(-ENOKEY);
72 		default:
73 			return key;
74 		}
75 	}
76 
77 	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
78 
79 	return key;
80 }
81 
asymmetric_verify(struct key * keyring,const char * sig,int siglen,const char * data,int datalen)82 int asymmetric_verify(struct key *keyring, const char *sig,
83 		      int siglen, const char *data, int datalen)
84 {
85 	struct public_key_signature pks;
86 	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
87 	const struct public_key *pk;
88 	struct key *key;
89 	int ret;
90 
91 	if (siglen <= sizeof(*hdr))
92 		return -EBADMSG;
93 
94 	siglen -= sizeof(*hdr);
95 
96 	if (siglen != be16_to_cpu(hdr->sig_size))
97 		return -EBADMSG;
98 
99 	if (hdr->hash_algo >= HASH_ALGO__LAST)
100 		return -ENOPKG;
101 
102 	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
103 	if (IS_ERR(key))
104 		return PTR_ERR(key);
105 
106 	memset(&pks, 0, sizeof(pks));
107 
108 	pks.hash_algo = hash_algo_name[hdr->hash_algo];
109 
110 	pk = asymmetric_key_public_key(key);
111 	pks.pkey_algo = pk->pkey_algo;
112 	if (!strcmp(pk->pkey_algo, "rsa")) {
113 		pks.encoding = "pkcs1";
114 	} else if (!strncmp(pk->pkey_algo, "ecdsa-", 6)) {
115 		/* edcsa-nist-p192 etc. */
116 		pks.encoding = "x962";
117 	} else if (!strcmp(pk->pkey_algo, "ecrdsa") ||
118 		   !strcmp(pk->pkey_algo, "sm2")) {
119 		pks.encoding = "raw";
120 	} else {
121 		ret = -ENOPKG;
122 		goto out;
123 	}
124 
125 	pks.digest = (u8 *)data;
126 	pks.digest_size = datalen;
127 	pks.s = hdr->sig;
128 	pks.s_size = siglen;
129 	ret = verify_signature(key, &pks);
130 out:
131 	key_put(key);
132 	pr_debug("%s() = %d\n", __func__, ret);
133 	return ret;
134 }
135 
136 /**
137  * integrity_kernel_module_request - prevent crypto-pkcs1pad(rsa,*) requests
138  * @kmod_name: kernel module name
139  *
140  * We have situation, when public_key_verify_signature() in case of RSA
141  * algorithm use alg_name to store internal information in order to
142  * construct an algorithm on the fly, but crypto_larval_lookup() will try
143  * to use alg_name in order to load kernel module with same name.
144  * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
145  * we are safe to fail such module request from crypto_larval_lookup().
146  *
147  * In this way we prevent modprobe execution during digsig verification
148  * and avoid possible deadlock if modprobe and/or it's dependencies
149  * also signed with digsig.
150  */
integrity_kernel_module_request(char * kmod_name)151 int integrity_kernel_module_request(char *kmod_name)
152 {
153 	if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
154 		return -EINVAL;
155 
156 	return 0;
157 }
158