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 <keys/asymmetric-subtype.h>
  17 #include <keys/asymmetric-parser.h>
  18 #include <keys/system_keyring.h>
  19 #include <crypto/hash.h>
  20 #include "asymmetric_keys.h"
  21 #include "x509_parser.h"
  22
  23 static bool use_builtin_keys;
  24 static struct asymmetric_key_id *ca_keyid;
  25
  26 #ifndef MODULE
  27 static struct {
  28         struct asymmetric_key_id id;
  29         unsigned char data[10];
  30 } cakey;
  31
  32 static int __init ca_keys_setup(char *str)
  33 {
  34         if (!str)               /* default system keyring */
  35                 return 1;
  36
  37         if (strncmp(str, "id:", 3) == 0) {
  38                 struct asymmetric_key_id *p = &cakey.id;
  39                 size_t hexlen = (strlen(str) - 3) / 2;
  40                 int ret;
  41
  42                 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
  43                         pr_err("Missing or invalid ca_keys id\n");
  44                         return 1;
  45                 }
  46
  47                 ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
  48                 if (ret < 0)
  49                         pr_err("Unparsable ca_keys id hex string\n");
  50                 else
  51                         ca_keyid = p;   /* owner key 'id:xxxxxx' */
  52         } else if (strcmp(str, "builtin") == 0) {
  53                 use_builtin_keys = true;
  54         }
  55
  56         return 1;
  57 }
  58 __setup("ca_keys=", ca_keys_setup);
  59 #endif
  60
  61 /**
  62  * x509_request_asymmetric_key - Request a key by X.509 certificate params.
  63  * @keyring: The keys to search.
  64  * @id: The issuer & serialNumber to look for or NULL.
  65  * @skid: The subjectKeyIdentifier to look for or NULL.
  66  * @partial: Use partial match if true, exact if false.
  67  *
  68  * Find a key in the given keyring by identifier.  The preferred identifier is
  69  * the issuer + serialNumber and the fallback identifier is the
  70  * subjectKeyIdentifier.  If both are given, the lookup is by the former, but
  71  * the latter must also match.
  72  */
  73 struct key *x509_request_asymmetric_key(struct key *keyring,
  74                                         const struct asymmetric_key_id *id,
  75                                         const struct asymmetric_key_id *skid,
  76                                         bool partial)
  77 {
  78         struct key *key;
  79         key_ref_t ref;
  80         const char *lookup;
  81         char *req, *p;
  82         int len;
  83
  84         if (id) {
  85                 lookup = id->data;
  86                 len = id->len;
  87         } else {
  88                 lookup = skid->data;
  89                 len = skid->len;
  90         }
  91
  92         /* Construct an identifier "id:<keyid>". */
  93         p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
  94         if (!req)
  95                 return ERR_PTR(-ENOMEM);
  96
  97         if (partial) {
  98                 *p++ = 'i';
  99                 *p++ = 'd';
 100         } else {
 101                 *p++ = 'e';
 102                 *p++ = 'x';
 103         }
 104         *p++ = ':';
 105         p = bin2hex(p, lookup, len);
 106         *p = 0;
 107
 108         pr_debug("Look up: \"%s\"\n", req);
 109
 110         ref = keyring_search(make_key_ref(keyring, 1),
 111                              &key_type_asymmetric, req);
 112         if (IS_ERR(ref))
 113                 pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
 114         kfree(req);
 115
 116         if (IS_ERR(ref)) {
 117                 switch (PTR_ERR(ref)) {
 118                         /* Hide some search errors */
 119                 case -EACCES:
 120                 case -ENOTDIR:
 121                 case -EAGAIN:
 122                         return ERR_PTR(-ENOKEY);
 123                 default:
 124                         return ERR_CAST(ref);
 125                 }
 126         }
 127
 128         key = key_ref_to_ptr(ref);
 129         if (id && skid) {
 130                 const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
 131                 if (!kids->id[1]) {
 132                         pr_debug("issuer+serial match, but expected SKID missing\n");
 133                         goto reject;
 134                 }
 135                 if (!asymmetric_key_id_same(skid, kids->id[1])) {
 136                         pr_debug("issuer+serial match, but SKID does not\n");
 137                         goto reject;
 138                 }
 139         }
 140
 141         pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
 142         return key;
 143
 144 reject:
 145         key_put(key);
 146         return ERR_PTR(-EKEYREJECTED);
 147 }
 148 EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
 149
 150 /*
 151  * Set up the signature parameters in an X.509 certificate.  This involves
 152  * digesting the signed data and extracting the signature.
 153  */
 154 int x509_get_sig_params(struct x509_certificate *cert)
 155 {
 156         struct crypto_shash *tfm;
 157         struct shash_desc *desc;
 158         size_t digest_size, desc_size;
 159         void *digest;
 160         int ret;
 161
 162         pr_devel("==>%s()\n", __func__);
 163
 164         if (cert->unsupported_crypto)
 165                 return -ENOPKG;
 166         if (cert->sig.s)
 167                 return 0;
 168
 169         cert->sig.s = kmemdup(cert->raw_sig, cert->raw_sig_size,
 170                               GFP_KERNEL);
 171         if (!cert->sig.s)
 172                 return -ENOMEM;
 173
 174         cert->sig.s_size = cert->raw_sig_size;
 175
 176         /* Allocate the hashing algorithm we're going to need and find out how
 177          * big the hash operational data will be.
 178          */
 179         tfm = crypto_alloc_shash(cert->sig.hash_algo, 0, 0);
 180         if (IS_ERR(tfm)) {
 181                 if (PTR_ERR(tfm) == -ENOENT) {
 182                         cert->unsupported_crypto = true;
 183                         return -ENOPKG;
 184                 }
 185                 return PTR_ERR(tfm);
 186         }
 187
 188         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
 189         digest_size = crypto_shash_digestsize(tfm);
 190
 191         /* We allocate the hash operational data storage on the end of the
 192          * digest storage space.
 193          */
 194         ret = -ENOMEM;
 195         digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
 196                          GFP_KERNEL);
 197         if (!digest)
 198                 goto error;
 199
 200         cert->sig.digest = digest;
 201         cert->sig.digest_size = digest_size;
 202
 203         desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
 204         desc->tfm = tfm;
 205         desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 206
 207         ret = crypto_shash_init(desc);
 208         if (ret < 0)
 209                 goto error;
 210         might_sleep();
 211         ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
 212 error:
 213         crypto_free_shash(tfm);
 214         pr_devel("<==%s() = %d\n", __func__, ret);
 215         return ret;
 216 }
 217 EXPORT_SYMBOL_GPL(x509_get_sig_params);
 218
 219 /*
 220  * Check the signature on a certificate using the provided public key
 221  */
 222 int x509_check_signature(const struct public_key *pub,
 223                          struct x509_certificate *cert)
 224 {
 225         int ret;
 226
 227         pr_devel("==>%s()\n", __func__);
 228
 229         ret = x509_get_sig_params(cert);
 230         if (ret < 0)
 231                 return ret;
 232
 233         ret = public_key_verify_signature(pub, &cert->sig);
 234         if (ret == -ENOPKG)
 235                 cert->unsupported_crypto = true;
 236         pr_debug("Cert Verification: %d\n", ret);
 237         return ret;
 238 }
 239 EXPORT_SYMBOL_GPL(x509_check_signature);
 240
 241 /*
 242  * Check the new certificate against the ones in the trust keyring.  If one of
 243  * those is the signing key and validates the new certificate, then mark the
 244  * new certificate as being trusted.
 245  *
 246  * Return 0 if the new certificate was successfully validated, 1 if we couldn't
 247  * find a matching parent certificate in the trusted list and an error if there
 248  * is a matching certificate but the signature check fails.
 249  */
 250 static int x509_validate_trust(struct x509_certificate *cert,
 251                                struct key *trust_keyring)
 252 {
 253         struct key *key;
 254         int ret = 1;
 255
 256         if (!trust_keyring)
 257                 return -EOPNOTSUPP;
 258
 259         if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
 260                 return -EPERM;
 261
 262         key = x509_request_asymmetric_key(trust_keyring,
 263                                           cert->akid_id, cert->akid_skid,
 264                                           false);
 265         if (!IS_ERR(key))  {
 266                 if (!use_builtin_keys
 267                     || test_bit(KEY_FLAG_BUILTIN, &key->flags))
 268                         ret = x509_check_signature(key->payload.data[asym_crypto],
 269                                                    cert);
 270                 key_put(key);
 271         }
 272         return ret;
 273 }
 274
 275 /*
 276  * Attempt to parse a data blob for a key as an X509 certificate.
 277  */
 278 static int x509_key_preparse(struct key_preparsed_payload *prep)
 279 {
 280         struct asymmetric_key_ids *kids;
 281         struct x509_certificate *cert;
 282         const char *q;
 283         size_t srlen, sulen;
 284         char *desc = NULL, *p;
 285         int ret;
 286
 287         cert = x509_cert_parse(prep->data, prep->datalen);
 288         if (IS_ERR(cert))
 289                 return PTR_ERR(cert);
 290
 291         pr_devel("Cert Issuer: %s\n", cert->issuer);
 292         pr_devel("Cert Subject: %s\n", cert->subject);
 293
 294         if (!cert->pub->pkey_algo ||
 295             !cert->sig.pkey_algo ||
 296             !cert->sig.hash_algo) {
 297                 ret = -ENOPKG;
 298                 goto error_free_cert;
 299         }
 300
 301         pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 302         pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
 303         pr_devel("Cert Signature: %s + %s\n",
 304                  cert->sig.pkey_algo,
 305                  cert->sig.hash_algo);
 306
 307         cert->pub->id_type = "X509";
 308
 309         /* Check the signature on the key if it appears to be self-signed */
 310         if ((!cert->akid_skid && !cert->akid_id) ||
 311             asymmetric_key_id_same(cert->skid, cert->akid_skid) ||
 312             asymmetric_key_id_same(cert->id, cert->akid_id)) {
 313                 ret = x509_check_signature(cert->pub, cert); /* self-signed */
 314                 if (ret < 0)
 315                         goto error_free_cert;
 316         } else if (!prep->trusted) {
 317                 ret = x509_validate_trust(cert, get_system_trusted_keyring());
 318                 if (ret)
 319                         ret = x509_validate_trust(cert, get_ima_mok_keyring());
 320                 if (!ret)
 321                         prep->trusted = 1;
 322         }
 323
 324         /* Propose a description */
 325         sulen = strlen(cert->subject);
 326         if (cert->raw_skid) {
 327                 srlen = cert->raw_skid_size;
 328                 q = cert->raw_skid;
 329         } else {
 330                 srlen = cert->raw_serial_size;
 331                 q = cert->raw_serial;
 332         }
 333
 334         ret = -ENOMEM;
 335         desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
 336         if (!desc)
 337                 goto error_free_cert;
 338         p = memcpy(desc, cert->subject, sulen);
 339         p += sulen;
 340         *p++ = ':';
 341         *p++ = ' ';
 342         p = bin2hex(p, q, srlen);
 343         *p = 0;
 344
 345         kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
 346         if (!kids)
 347                 goto error_free_desc;
 348         kids->id[0] = cert->id;
 349         kids->id[1] = cert->skid;
 350
 351         /* We're pinning the module by being linked against it */
 352         __module_get(public_key_subtype.owner);
 353         prep->payload.data[asym_subtype] = &public_key_subtype;
 354         prep->payload.data[asym_key_ids] = kids;
 355         prep->payload.data[asym_crypto] = cert->pub;
 356         prep->description = desc;
 357         prep->quotalen = 100;
 358
 359         /* We've finished with the certificate */
 360         cert->pub = NULL;
 361         cert->id = NULL;
 362         cert->skid = NULL;
 363         desc = NULL;
 364         ret = 0;
 365
 366 error_free_desc:
 367         kfree(desc);
 368 error_free_cert:
 369         x509_free_certificate(cert);
 370         return ret;
 371 }
 372
 373 static struct asymmetric_key_parser x509_key_parser = {
 374         .owner  = THIS_MODULE,
 375         .name   = "x509",
 376         .parse  = x509_key_preparse,
 377 };
 378
 379 /*
 380  * Module stuff
 381  */
 382 static int __init x509_key_init(void)
 383 {
 384         return register_asymmetric_key_parser(&x509_key_parser);
 385 }
 386
 387 static void __exit x509_key_exit(void)
 388 {
 389         unregister_asymmetric_key_parser(&x509_key_parser);
 390 }
 391
 392 module_init(x509_key_init);
 393 module_exit(x509_key_exit);
 394
 395 MODULE_DESCRIPTION("X.509 certificate parser");
 396 MODULE_LICENSE("GPL");