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