xref: /openbmc/linux/security/integrity/digsig.c (revision 44900c3e)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2011 Intel Corporation
4  *
5  * Author:
6  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
7  */
8 
9 #include <linux/err.h>
10 #include <linux/sched.h>
11 #include <linux/slab.h>
12 #include <linux/cred.h>
13 #include <linux/kernel_read_file.h>
14 #include <linux/key-type.h>
15 #include <linux/digsig.h>
16 #include <linux/vmalloc.h>
17 #include <crypto/public_key.h>
18 #include <keys/system_keyring.h>
19 
20 #include "integrity.h"
21 
22 static struct key *keyring[INTEGRITY_KEYRING_MAX];
23 
24 static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
25 #ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
26 	"_evm",
27 	"_ima",
28 #else
29 	".evm",
30 	".ima",
31 #endif
32 	".platform",
33 	".machine",
34 };
35 
36 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
37 #define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
38 #else
39 #define restrict_link_to_ima restrict_link_by_builtin_trusted
40 #endif
41 
42 static struct key *integrity_keyring_from_id(const unsigned int id)
43 {
44 	if (id >= INTEGRITY_KEYRING_MAX)
45 		return ERR_PTR(-EINVAL);
46 
47 	if (!keyring[id]) {
48 		keyring[id] =
49 			request_key(&key_type_keyring, keyring_name[id], NULL);
50 		if (IS_ERR(keyring[id])) {
51 			int err = PTR_ERR(keyring[id]);
52 			pr_err("no %s keyring: %d\n", keyring_name[id], err);
53 			keyring[id] = NULL;
54 			return ERR_PTR(err);
55 		}
56 	}
57 
58 	return keyring[id];
59 }
60 
61 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
62 			    const char *digest, int digestlen)
63 {
64 	struct key *keyring;
65 
66 	if (siglen < 2)
67 		return -EINVAL;
68 
69 	keyring = integrity_keyring_from_id(id);
70 	if (IS_ERR(keyring))
71 		return PTR_ERR(keyring);
72 
73 	switch (sig[1]) {
74 	case 1:
75 		/* v1 API expect signature without xattr type */
76 		return digsig_verify(keyring, sig + 1, siglen - 1, digest,
77 				     digestlen);
78 	case 2: /* regular file data hash based signature */
79 	case 3: /* struct ima_file_id data based signature */
80 		return asymmetric_verify(keyring, sig, siglen, digest,
81 					 digestlen);
82 	}
83 
84 	return -EOPNOTSUPP;
85 }
86 
87 int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
88 {
89 	struct key *keyring;
90 
91 	keyring = integrity_keyring_from_id(id);
92 	if (IS_ERR(keyring))
93 		return PTR_ERR(keyring);
94 
95 	return ima_modsig_verify(keyring, modsig);
96 }
97 
98 static int __init __integrity_init_keyring(const unsigned int id,
99 					   key_perm_t perm,
100 					   struct key_restriction *restriction)
101 {
102 	const struct cred *cred = current_cred();
103 	int err = 0;
104 
105 	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
106 				    KGIDT_INIT(0), cred, perm,
107 				    KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
108 	if (IS_ERR(keyring[id])) {
109 		err = PTR_ERR(keyring[id]);
110 		pr_info("Can't allocate %s keyring (%d)\n",
111 			keyring_name[id], err);
112 		keyring[id] = NULL;
113 	} else {
114 		if (id == INTEGRITY_KEYRING_PLATFORM)
115 			set_platform_trusted_keys(keyring[id]);
116 		if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
117 			set_machine_trusted_keys(keyring[id]);
118 		if (id == INTEGRITY_KEYRING_IMA)
119 			load_module_cert(keyring[id]);
120 	}
121 
122 	return err;
123 }
124 
125 int __init integrity_init_keyring(const unsigned int id)
126 {
127 	struct key_restriction *restriction;
128 	key_perm_t perm;
129 	int ret;
130 
131 	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
132 		| KEY_USR_READ | KEY_USR_SEARCH;
133 
134 	if (id == INTEGRITY_KEYRING_PLATFORM ||
135 	    (id == INTEGRITY_KEYRING_MACHINE &&
136 	    !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
137 		restriction = NULL;
138 		goto out;
139 	}
140 
141 	if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
142 		return 0;
143 
144 	restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
145 	if (!restriction)
146 		return -ENOMEM;
147 
148 	if (id == INTEGRITY_KEYRING_MACHINE)
149 		restriction->check = restrict_link_by_ca;
150 	else
151 		restriction->check = restrict_link_to_ima;
152 
153 	/*
154 	 * MOK keys can only be added through a read-only runtime services
155 	 * UEFI variable during boot. No additional keys shall be allowed to
156 	 * load into the machine keyring following init from userspace.
157 	 */
158 	if (id != INTEGRITY_KEYRING_MACHINE)
159 		perm |= KEY_USR_WRITE;
160 
161 out:
162 	ret = __integrity_init_keyring(id, perm, restriction);
163 	if (ret)
164 		kfree(restriction);
165 	return ret;
166 }
167 
168 static int __init integrity_add_key(const unsigned int id, const void *data,
169 				    off_t size, key_perm_t perm)
170 {
171 	key_ref_t key;
172 	int rc = 0;
173 
174 	if (!keyring[id])
175 		return -EINVAL;
176 
177 	key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
178 				   NULL, data, size, perm,
179 				   KEY_ALLOC_NOT_IN_QUOTA);
180 	if (IS_ERR(key)) {
181 		rc = PTR_ERR(key);
182 		pr_err("Problem loading X.509 certificate %d\n", rc);
183 	} else {
184 		pr_notice("Loaded X.509 cert '%s'\n",
185 			  key_ref_to_ptr(key)->description);
186 		key_ref_put(key);
187 	}
188 
189 	return rc;
190 
191 }
192 
193 int __init integrity_load_x509(const unsigned int id, const char *path)
194 {
195 	void *data = NULL;
196 	size_t size;
197 	int rc;
198 	key_perm_t perm;
199 
200 	rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
201 					READING_X509_CERTIFICATE);
202 	if (rc < 0) {
203 		pr_err("Unable to open file: %s (%d)", path, rc);
204 		return rc;
205 	}
206 	size = rc;
207 
208 	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
209 
210 	pr_info("Loading X.509 certificate: %s\n", path);
211 	rc = integrity_add_key(id, (const void *)data, size, perm);
212 
213 	vfree(data);
214 	return rc;
215 }
216 
217 int __init integrity_load_cert(const unsigned int id, const char *source,
218 			       const void *data, size_t len, key_perm_t perm)
219 {
220 	if (!data)
221 		return -EINVAL;
222 
223 	pr_info("Loading X.509 certificate: %s\n", source);
224 	return integrity_add_key(id, data, len, perm);
225 }
226