certs/system_keyring.c

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