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