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