1 /* System trusted keyring for trusted public keys 2 * 3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public Licence 8 * as published by the Free Software Foundation; either version 9 * 2 of the Licence, or (at your option) any later version. 10 */ 11 12 #include <linux/export.h> 13 #include <linux/kernel.h> 14 #include <linux/sched.h> 15 #include <linux/cred.h> 16 #include <linux/err.h> 17 #include <linux/slab.h> 18 #include <linux/verification.h> 19 #include <keys/asymmetric-type.h> 20 #include <keys/system_keyring.h> 21 #include <crypto/pkcs7.h> 22 23 static struct key *builtin_trusted_keys; 24 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING 25 static struct key *secondary_trusted_keys; 26 #endif 27 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING 28 static struct key *platform_trusted_keys; 29 #endif 30 31 extern __initconst const u8 system_certificate_list[]; 32 extern __initconst const unsigned long system_certificate_list_size; 33 34 /** 35 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA 36 * 37 * Restrict the addition of keys into a keyring based on the key-to-be-added 38 * being vouched for by a key in the built in system keyring. 39 */ 40 int restrict_link_by_builtin_trusted(struct key *dest_keyring, 41 const struct key_type *type, 42 const union key_payload *payload, 43 struct key *restriction_key) 44 { 45 return restrict_link_by_signature(dest_keyring, type, payload, 46 builtin_trusted_keys); 47 } 48 49 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING 50 /** 51 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring 52 * addition by both builtin and secondary keyrings 53 * 54 * Restrict the addition of keys into a keyring based on the key-to-be-added 55 * being vouched for by a key in either the built-in or the secondary system 56 * keyrings. 57 */ 58 int restrict_link_by_builtin_and_secondary_trusted( 59 struct key *dest_keyring, 60 const struct key_type *type, 61 const union key_payload *payload, 62 struct key *restrict_key) 63 { 64 /* If we have a secondary trusted keyring, then that contains a link 65 * through to the builtin keyring and the search will follow that link. 66 */ 67 if (type == &key_type_keyring && 68 dest_keyring == secondary_trusted_keys && 69 payload == &builtin_trusted_keys->payload) 70 /* Allow the builtin keyring to be added to the secondary */ 71 return 0; 72 73 return restrict_link_by_signature(dest_keyring, type, payload, 74 secondary_trusted_keys); 75 } 76 77 /** 78 * Allocate a struct key_restriction for the "builtin and secondary trust" 79 * keyring. Only for use in system_trusted_keyring_init(). 80 */ 81 static __init struct key_restriction *get_builtin_and_secondary_restriction(void) 82 { 83 struct key_restriction *restriction; 84 85 restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL); 86 87 if (!restriction) 88 panic("Can't allocate secondary trusted keyring restriction\n"); 89 90 restriction->check = restrict_link_by_builtin_and_secondary_trusted; 91 92 return restriction; 93 } 94 #endif 95 96 /* 97 * Create the trusted keyrings 98 */ 99 static __init int system_trusted_keyring_init(void) 100 { 101 pr_notice("Initialise system trusted keyrings\n"); 102 103 builtin_trusted_keys = 104 keyring_alloc(".builtin_trusted_keys", 105 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(), 106 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 107 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH), 108 KEY_ALLOC_NOT_IN_QUOTA, 109 NULL, NULL); 110 if (IS_ERR(builtin_trusted_keys)) 111 panic("Can't allocate builtin trusted keyring\n"); 112 113 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING 114 secondary_trusted_keys = 115 keyring_alloc(".secondary_trusted_keys", 116 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(), 117 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 118 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH | 119 KEY_USR_WRITE), 120 KEY_ALLOC_NOT_IN_QUOTA, 121 get_builtin_and_secondary_restriction(), 122 NULL); 123 if (IS_ERR(secondary_trusted_keys)) 124 panic("Can't allocate secondary trusted keyring\n"); 125 126 if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0) 127 panic("Can't link trusted keyrings\n"); 128 #endif 129 130 return 0; 131 } 132 133 /* 134 * Must be initialised before we try and load the keys into the keyring. 135 */ 136 device_initcall(system_trusted_keyring_init); 137 138 /* 139 * Load the compiled-in list of X.509 certificates. 140 */ 141 static __init int load_system_certificate_list(void) 142 { 143 key_ref_t key; 144 const u8 *p, *end; 145 size_t plen; 146 147 pr_notice("Loading compiled-in X.509 certificates\n"); 148 149 p = system_certificate_list; 150 end = p + system_certificate_list_size; 151 while (p < end) { 152 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more 153 * than 256 bytes in size. 154 */ 155 if (end - p < 4) 156 goto dodgy_cert; 157 if (p[0] != 0x30 && 158 p[1] != 0x82) 159 goto dodgy_cert; 160 plen = (p[2] << 8) | p[3]; 161 plen += 4; 162 if (plen > end - p) 163 goto dodgy_cert; 164 165 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1), 166 "asymmetric", 167 NULL, 168 p, 169 plen, 170 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 171 KEY_USR_VIEW | KEY_USR_READ), 172 KEY_ALLOC_NOT_IN_QUOTA | 173 KEY_ALLOC_BUILT_IN | 174 KEY_ALLOC_BYPASS_RESTRICTION); 175 if (IS_ERR(key)) { 176 pr_err("Problem loading in-kernel X.509 certificate (%ld)\n", 177 PTR_ERR(key)); 178 } else { 179 pr_notice("Loaded X.509 cert '%s'\n", 180 key_ref_to_ptr(key)->description); 181 key_ref_put(key); 182 } 183 p += plen; 184 } 185 186 return 0; 187 188 dodgy_cert: 189 pr_err("Problem parsing in-kernel X.509 certificate list\n"); 190 return 0; 191 } 192 late_initcall(load_system_certificate_list); 193 194 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION 195 196 /** 197 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data. 198 * @data: The data to be verified (NULL if expecting internal data). 199 * @len: Size of @data. 200 * @raw_pkcs7: The PKCS#7 message that is the signature. 201 * @pkcs7_len: The size of @raw_pkcs7. 202 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only, 203 * (void *)1UL for all trusted keys). 204 * @usage: The use to which the key is being put. 205 * @view_content: Callback to gain access to content. 206 * @ctx: Context for callback. 207 */ 208 int verify_pkcs7_signature(const void *data, size_t len, 209 const void *raw_pkcs7, size_t pkcs7_len, 210 struct key *trusted_keys, 211 enum key_being_used_for usage, 212 int (*view_content)(void *ctx, 213 const void *data, size_t len, 214 size_t asn1hdrlen), 215 void *ctx) 216 { 217 struct pkcs7_message *pkcs7; 218 int ret; 219 220 pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len); 221 if (IS_ERR(pkcs7)) 222 return PTR_ERR(pkcs7); 223 224 /* The data should be detached - so we need to supply it. */ 225 if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) { 226 pr_err("PKCS#7 signature with non-detached data\n"); 227 ret = -EBADMSG; 228 goto error; 229 } 230 231 ret = pkcs7_verify(pkcs7, usage); 232 if (ret < 0) 233 goto error; 234 235 if (!trusted_keys) { 236 trusted_keys = builtin_trusted_keys; 237 } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) { 238 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING 239 trusted_keys = secondary_trusted_keys; 240 #else 241 trusted_keys = builtin_trusted_keys; 242 #endif 243 } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) { 244 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING 245 trusted_keys = platform_trusted_keys; 246 #else 247 trusted_keys = NULL; 248 #endif 249 if (!trusted_keys) { 250 ret = -ENOKEY; 251 pr_devel("PKCS#7 platform keyring is not available\n"); 252 goto error; 253 } 254 } 255 ret = pkcs7_validate_trust(pkcs7, trusted_keys); 256 if (ret < 0) { 257 if (ret == -ENOKEY) 258 pr_devel("PKCS#7 signature not signed with a trusted key\n"); 259 goto error; 260 } 261 262 if (view_content) { 263 size_t asn1hdrlen; 264 265 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen); 266 if (ret < 0) { 267 if (ret == -ENODATA) 268 pr_devel("PKCS#7 message does not contain data\n"); 269 goto error; 270 } 271 272 ret = view_content(ctx, data, len, asn1hdrlen); 273 } 274 275 error: 276 pkcs7_free_message(pkcs7); 277 pr_devel("<==%s() = %d\n", __func__, ret); 278 return ret; 279 } 280 EXPORT_SYMBOL_GPL(verify_pkcs7_signature); 281 282 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */ 283 284 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING 285 void __init set_platform_trusted_keys(struct key *keyring) 286 { 287 platform_trusted_keys = keyring; 288 } 289 #endif 290