crypto/asymmetric_keys/x509_public_key.c

   1 /* Instantiate a public key crypto key from an X.509 Certificate
   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 #define pr_fmt(fmt) "X.509: "fmt
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/slab.h>
  16 #include <linux/err.h>
  17 #include <linux/mpi.h>
  18 #include <linux/asn1_decoder.h>
  19 #include <keys/asymmetric-subtype.h>
  20 #include <keys/asymmetric-parser.h>
  21 #include <keys/system_keyring.h>
  22 #include <crypto/hash.h>
  23 #include "asymmetric_keys.h"
  24 #include "public_key.h"
  25 #include "x509_parser.h"
  26
  27 static bool use_builtin_keys;
  28 static struct asymmetric_key_id *ca_keyid;
  29
  30 #ifndef MODULE
  31 static int __init ca_keys_setup(char *str)
  32 {
  33         if (!str)               /* default system keyring */
  34                 return 1;
  35
  36         if (strncmp(str, "id:", 3) == 0) {
  37                 struct asymmetric_key_id *p;
  38                 p = asymmetric_key_hex_to_key_id(str + 3);
  39                 if (p == ERR_PTR(-EINVAL))
  40                         pr_err("Unparsable hex string in ca_keys\n");
  41                 else if (!IS_ERR(p))
  42                         ca_keyid = p;   /* owner key 'id:xxxxxx' */
  43         } else if (strcmp(str, "builtin") == 0) {
  44                 use_builtin_keys = true;
  45         }
  46
  47         return 1;
  48 }
  49 __setup("ca_keys=", ca_keys_setup);
  50 #endif
  51
  52 /**
  53  * x509_request_asymmetric_key - Request a key by X.509 certificate params.
  54  * @keyring: The keys to search.
  55  * @kid: The key ID.
  56  * @partial: Use partial match if true, exact if false.
  57  *
  58  * Find a key in the given keyring by subject name and key ID.  These might,
  59  * for instance, be the issuer name and the authority key ID of an X.509
  60  * certificate that needs to be verified.
  61  */
  62 struct key *x509_request_asymmetric_key(struct key *keyring,
  63                                         const struct asymmetric_key_id *kid,
  64                                         bool partial)
  65 {
  66         key_ref_t key;
  67         char *id, *p;
  68
  69         /* Construct an identifier "id:<keyid>". */
  70         p = id = kmalloc(2 + 1 + kid->len * 2 + 1, GFP_KERNEL);
  71         if (!id)
  72                 return ERR_PTR(-ENOMEM);
  73
  74         if (partial) {
  75                 *p++ = 'i';
  76                 *p++ = 'd';
  77         } else {
  78                 *p++ = 'e';
  79                 *p++ = 'x';
  80         }
  81         *p++ = ':';
  82         p = bin2hex(p, kid->data, kid->len);
  83         *p = 0;
  84
  85         pr_debug("Look up: \"%s\"\n", id);
  86
  87         key = keyring_search(make_key_ref(keyring, 1),
  88                              &key_type_asymmetric, id);
  89         if (IS_ERR(key))
  90                 pr_debug("Request for key '%s' err %ld\n", id, PTR_ERR(key));
  91         kfree(id);
  92
  93         if (IS_ERR(key)) {
  94                 switch (PTR_ERR(key)) {
  95                         /* Hide some search errors */
  96                 case -EACCES:
  97                 case -ENOTDIR:
  98                 case -EAGAIN:
  99                         return ERR_PTR(-ENOKEY);
 100                 default:
 101                         return ERR_CAST(key);
 102                 }
 103         }
 104
 105         pr_devel("<==%s() = 0 [%x]\n", __func__,
 106                  key_serial(key_ref_to_ptr(key)));
 107         return key_ref_to_ptr(key);
 108 }
 109 EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
 110
 111 /*
 112  * Set up the signature parameters in an X.509 certificate.  This involves
 113  * digesting the signed data and extracting the signature.
 114  */
 115 int x509_get_sig_params(struct x509_certificate *cert)
 116 {
 117         struct crypto_shash *tfm;
 118         struct shash_desc *desc;
 119         size_t digest_size, desc_size;
 120         void *digest;
 121         int ret;
 122
 123         pr_devel("==>%s()\n", __func__);
 124
 125         if (cert->unsupported_crypto)
 126                 return -ENOPKG;
 127         if (cert->sig.rsa.s)
 128                 return 0;
 129
 130         cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
 131         if (!cert->sig.rsa.s)
 132                 return -ENOMEM;
 133         cert->sig.nr_mpi = 1;
 134
 135         /* Allocate the hashing algorithm we're going to need and find out how
 136          * big the hash operational data will be.
 137          */
 138         tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
 139         if (IS_ERR(tfm)) {
 140                 if (PTR_ERR(tfm) == -ENOENT) {
 141                         cert->unsupported_crypto = true;
 142                         return -ENOPKG;
 143                 }
 144                 return PTR_ERR(tfm);
 145         }
 146
 147         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
 148         digest_size = crypto_shash_digestsize(tfm);
 149
 150         /* We allocate the hash operational data storage on the end of the
 151          * digest storage space.
 152          */
 153         ret = -ENOMEM;
 154         digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
 155         if (!digest)
 156                 goto error;
 157
 158         cert->sig.digest = digest;
 159         cert->sig.digest_size = digest_size;
 160
 161         desc = digest + digest_size;
 162         desc->tfm = tfm;
 163         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 164
 165         ret = crypto_shash_init(desc);
 166         if (ret < 0)
 167                 goto error;
 168         might_sleep();
 169         ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
 170 error:
 171         crypto_free_shash(tfm);
 172         pr_devel("<==%s() = %d\n", __func__, ret);
 173         return ret;
 174 }
 175 EXPORT_SYMBOL_GPL(x509_get_sig_params);
 176
 177 /*
 178  * Check the signature on a certificate using the provided public key
 179  */
 180 int x509_check_signature(const struct public_key *pub,
 181                          struct x509_certificate *cert)
 182 {
 183         int ret;
 184
 185         pr_devel("==>%s()\n", __func__);
 186
 187         ret = x509_get_sig_params(cert);
 188         if (ret < 0)
 189                 return ret;
 190
 191         ret = public_key_verify_signature(pub, &cert->sig);
 192         if (ret == -ENOPKG)
 193                 cert->unsupported_crypto = true;
 194         pr_debug("Cert Verification: %d\n", ret);
 195         return ret;
 196 }
 197 EXPORT_SYMBOL_GPL(x509_check_signature);
 198
 199 /*
 200  * Check the new certificate against the ones in the trust keyring.  If one of
 201  * those is the signing key and validates the new certificate, then mark the
 202  * new certificate as being trusted.
 203  *
 204  * Return 0 if the new certificate was successfully validated, 1 if we couldn't
 205  * find a matching parent certificate in the trusted list and an error if there
 206  * is a matching certificate but the signature check fails.
 207  */
 208 static int x509_validate_trust(struct x509_certificate *cert,
 209                                struct key *trust_keyring)
 210 {
 211         struct key *key;
 212         int ret = 1;
 213
 214         if (!trust_keyring)
 215                 return -EOPNOTSUPP;
 216
 217         if (ca_keyid && !asymmetric_key_id_partial(cert->authority, ca_keyid))
 218                 return -EPERM;
 219
 220         key = x509_request_asymmetric_key(trust_keyring, cert->authority,
 221                                           false);
 222         if (!IS_ERR(key))  {
 223                 if (!use_builtin_keys
 224                     || test_bit(KEY_FLAG_BUILTIN, &key->flags))
 225                         ret = x509_check_signature(key->payload.data, cert);
 226                 key_put(key);
 227         }
 228         return ret;
 229 }
 230
 231 /*
 232  * Attempt to parse a data blob for a key as an X509 certificate.
 233  */
 234 static int x509_key_preparse(struct key_preparsed_payload *prep)
 235 {
 236         struct asymmetric_key_ids *kids;
 237         struct x509_certificate *cert;
 238         const char *q;
 239         size_t srlen, sulen;
 240         char *desc = NULL, *p;
 241         int ret;
 242
 243         cert = x509_cert_parse(prep->data, prep->datalen);
 244         if (IS_ERR(cert))
 245                 return PTR_ERR(cert);
 246
 247         pr_devel("Cert Issuer: %s\n", cert->issuer);
 248         pr_devel("Cert Subject: %s\n", cert->subject);
 249
 250         if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
 251             cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
 252             cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
 253             !pkey_algo[cert->pub->pkey_algo] ||
 254             !pkey_algo[cert->sig.pkey_algo] ||
 255             !hash_algo_name[cert->sig.pkey_hash_algo]) {
 256                 ret = -ENOPKG;
 257                 goto error_free_cert;
 258         }
 259
 260         pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
 261         pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 262                  cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
 263                  cert->valid_from.tm_mday, cert->valid_from.tm_hour,
 264                  cert->valid_from.tm_min,  cert->valid_from.tm_sec);
 265         pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
 266                  cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
 267                  cert->valid_to.tm_mday, cert->valid_to.tm_hour,
 268                  cert->valid_to.tm_min,  cert->valid_to.tm_sec);
 269         pr_devel("Cert Signature: %s + %s\n",
 270                  pkey_algo_name[cert->sig.pkey_algo],
 271                  hash_algo_name[cert->sig.pkey_hash_algo]);
 272
 273         cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
 274         cert->pub->id_type = PKEY_ID_X509;
 275
 276         /* Check the signature on the key if it appears to be self-signed */
 277         if (!cert->authority ||
 278             asymmetric_key_id_same(cert->skid, cert->authority)) {
 279                 ret = x509_check_signature(cert->pub, cert); /* self-signed */
 280                 if (ret < 0)
 281                         goto error_free_cert;
 282         } else if (!prep->trusted) {
 283                 ret = x509_validate_trust(cert, get_system_trusted_keyring());
 284                 if (!ret)
 285                         prep->trusted = 1;
 286         }
 287
 288         /* Propose a description */
 289         sulen = strlen(cert->subject);
 290         if (cert->raw_skid) {
 291                 srlen = cert->raw_skid_size;
 292                 q = cert->raw_skid;
 293         } else {
 294                 srlen = cert->raw_serial_size;
 295                 q = cert->raw_serial;
 296         }
 297         if (srlen > 1 && *q == 0) {
 298                 srlen--;
 299                 q++;
 300         }
 301
 302         ret = -ENOMEM;
 303         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 304         if (!desc)
 305                 goto error_free_cert;
 306         p = memcpy(desc, cert->subject, sulen);
 307         p += sulen;
 308         *p++ = ':';
 309         *p++ = ' ';
 310         p = bin2hex(p, q, srlen);
 311         *p = 0;
 312
 313         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 314         if (!kids)
 315                 goto error_free_desc;
 316         kids->id[0] = cert->id;
 317         kids->id[1] = cert->skid;
 318
 319         /* We're pinning the module by being linked against it */
 320         __module_get(public_key_subtype.owner);
 321         prep->type_data[0] = &public_key_subtype;
 322         prep->type_data[1] = kids;
 323         prep->payload[0] = cert->pub;
 324         prep->description = desc;
 325         prep->quotalen = 100;
 326
 327         /* We've finished with the certificate */
 328         cert->pub = NULL;
 329         cert->id = NULL;
 330         cert->skid = NULL;
 331         desc = NULL;
 332         ret = 0;
 333
 334 error_free_desc:
 335         kfree(desc);
 336 error_free_cert:
 337         x509_free_certificate(cert);
 338         return ret;
 339 }
 340
 341 static struct asymmetric_key_parser x509_key_parser = {
 342         .owner  = THIS_MODULE,
 343         .name   = "x509",
 344         .parse  = x509_key_preparse,
 345 };
 346
 347 /*
 348  * Module stuff
 349  */
 350 static int __init x509_key_init(void)
 351 {
 352         return register_asymmetric_key_parser(&x509_key_parser);
 353 }
 354
 355 static void __exit x509_key_exit(void)
 356 {
 357         unregister_asymmetric_key_parser(&x509_key_parser);
 358 }
 359
 360 module_init(x509_key_init);
 361 module_exit(x509_key_exit);
 362
 363 MODULE_DESCRIPTION("X.509 certificate parser");
 364 MODULE_LICENSE("GPL");