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 *system_trusted_keyring;
  22
  23 extern __initconst const u8 system_certificate_list[];
  24 extern __initconst const unsigned long system_certificate_list_size;
  25
  26 /**
  27  * restrict_link_by_builtin_trusted - Restrict keyring addition by system CA
  28  *
  29  * Restrict the addition of keys into a keyring based on the key-to-be-added
  30  * being vouched for by a key in the system keyring.
  31  */
  32 int restrict_link_by_builtin_trusted(struct key *keyring,
  33                                      const struct key_type *type,
  34                                      unsigned long flags,
  35                                      const union key_payload *payload)
  36 {
  37         return restrict_link_by_signature(system_trusted_keyring,
  38                                           type, payload);
  39 }
  40
  41 /*
  42  * Load the compiled-in keys
  43  */
  44 static __init int system_trusted_keyring_init(void)
  45 {
  46         pr_notice("Initialise system trusted keyring\n");
  47
  48         system_trusted_keyring =
  49                 keyring_alloc(".system_keyring",
  50                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  51                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  52                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
  53                               KEY_ALLOC_NOT_IN_QUOTA,
  54                               restrict_link_by_builtin_trusted, NULL);
  55         if (IS_ERR(system_trusted_keyring))
  56                 panic("Can't allocate system trusted keyring\n");
  57         return 0;
  58 }
  59
  60 /*
  61  * Must be initialised before we try and load the keys into the keyring.
  62  */
  63 device_initcall(system_trusted_keyring_init);
  64
  65 /*
  66  * Load the compiled-in list of X.509 certificates.
  67  */
  68 static __init int load_system_certificate_list(void)
  69 {
  70         key_ref_t key;
  71         const u8 *p, *end;
  72         size_t plen;
  73
  74         pr_notice("Loading compiled-in X.509 certificates\n");
  75
  76         p = system_certificate_list;
  77         end = p + system_certificate_list_size;
  78         while (p < end) {
  79                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
  80                  * than 256 bytes in size.
  81                  */
  82                 if (end - p < 4)
  83                         goto dodgy_cert;
  84                 if (p[0] != 0x30 &&
  85                     p[1] != 0x82)
  86                         goto dodgy_cert;
  87                 plen = (p[2] << 8) | p[3];
  88                 plen += 4;
  89                 if (plen > end - p)
  90                         goto dodgy_cert;
  91
  92                 key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
  93                                            "asymmetric",
  94                                            NULL,
  95                                            p,
  96                                            plen,
  97                                            ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  98                                            KEY_USR_VIEW | KEY_USR_READ),
  99                                            KEY_ALLOC_NOT_IN_QUOTA |
 100                                            KEY_ALLOC_TRUSTED |
 101                                            KEY_ALLOC_BUILT_IN |
 102                                            KEY_ALLOC_BYPASS_RESTRICTION);
 103                 if (IS_ERR(key)) {
 104                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 105                                PTR_ERR(key));
 106                 } else {
 107                         pr_notice("Loaded X.509 cert '%s'\n",
 108                                   key_ref_to_ptr(key)->description);
 109                         key_ref_put(key);
 110                 }
 111                 p += plen;
 112         }
 113
 114         return 0;
 115
 116 dodgy_cert:
 117         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 118         return 0;
 119 }
 120 late_initcall(load_system_certificate_list);
 121
 122 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 123
 124 /**
 125  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 126  * @data: The data to be verified (NULL if expecting internal data).
 127  * @len: Size of @data.
 128  * @raw_pkcs7: The PKCS#7 message that is the signature.
 129  * @pkcs7_len: The size of @raw_pkcs7.
 130  * @trusted_keys: Trusted keys to use (NULL for system_trusted_keyring).
 131  * @usage: The use to which the key is being put.
 132  * @view_content: Callback to gain access to content.
 133  * @ctx: Context for callback.
 134  */
 135 int verify_pkcs7_signature(const void *data, size_t len,
 136                            const void *raw_pkcs7, size_t pkcs7_len,
 137                            struct key *trusted_keys,
 138                            enum key_being_used_for usage,
 139                            int (*view_content)(void *ctx,
 140                                                const void *data, size_t len,
 141                                                size_t asn1hdrlen),
 142                            void *ctx)
 143 {
 144         struct pkcs7_message *pkcs7;
 145         int ret;
 146
 147         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 148         if (IS_ERR(pkcs7))
 149                 return PTR_ERR(pkcs7);
 150
 151         /* The data should be detached - so we need to supply it. */
 152         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 153                 pr_err("PKCS#7 signature with non-detached data\n");
 154                 ret = -EBADMSG;
 155                 goto error;
 156         }
 157
 158         ret = pkcs7_verify(pkcs7, usage);
 159         if (ret < 0)
 160                 goto error;
 161
 162         if (!trusted_keys)
 163                 trusted_keys = system_trusted_keyring;
 164         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 165         if (ret < 0) {
 166                 if (ret == -ENOKEY)
 167                         pr_err("PKCS#7 signature not signed with a trusted key\n");
 168                 goto error;
 169         }
 170
 171         if (view_content) {
 172                 size_t asn1hdrlen;
 173
 174                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 175                 if (ret < 0) {
 176                         if (ret == -ENODATA)
 177                                 pr_devel("PKCS#7 message does not contain data\n");
 178                         goto error;
 179                 }
 180
 181                 ret = view_content(ctx, data, len, asn1hdrlen);
 182         }
 183
 184 error:
 185         pkcs7_free_message(pkcs7);
 186         pr_devel("<==%s() = %d\n", __func__, ret);
 187         return ret;
 188 }
 189 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 190
 191 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */