src/crypto/ocsp.c

   1 /*
   2  * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  */
  19
  20 FILE_LICENCE ( GPL2_OR_LATER );
  21
  22 #include <stdint.h>
  23 #include <stdlib.h>
  24 #include <stdio.h>
  25 #include <string.h>
  26 #include <errno.h>
  27 #include <ipxe/asn1.h>
  28 #include <ipxe/x509.h>
  29 #include <ipxe/sha1.h>
  30 #include <ipxe/base64.h>
  31 #include <ipxe/uri.h>
  32 #include <ipxe/ocsp.h>
  33 #include <config/crypto.h>
  34
  35 /** @file
  36  *
  37  * Online Certificate Status Protocol
  38  *
  39  */
  40
  41 /* Disambiguate the various error causes */
  42 #define EACCES_CERT_STATUS                                              \
  43         __einfo_error ( EINFO_EACCES_CERT_STATUS )
  44 #define EINFO_EACCES_CERT_STATUS                                        \
  45         __einfo_uniqify ( EINFO_EACCES, 0x01,                           \
  46                           "Certificate status not good" )
  47 #define EACCES_CERT_MISMATCH                                            \
  48         __einfo_error ( EINFO_EACCES_CERT_MISMATCH )
  49 #define EINFO_EACCES_CERT_MISMATCH                                      \
  50         __einfo_uniqify ( EINFO_EACCES, 0x02,                           \
  51                           "Certificate ID mismatch" )
  52 #define EACCES_NON_OCSP_SIGNING                                         \
  53         __einfo_error ( EINFO_EACCES_NON_OCSP_SIGNING )
  54 #define EINFO_EACCES_NON_OCSP_SIGNING                                   \
  55         __einfo_uniqify ( EINFO_EACCES, 0x03,                           \
  56                           "Not an OCSP signing certificate" )
  57 #define EACCES_STALE                                                    \
  58         __einfo_error ( EINFO_EACCES_STALE )
  59 #define EINFO_EACCES_STALE                                              \
  60         __einfo_uniqify ( EINFO_EACCES, 0x04,                           \
  61                           "Stale (or premature) OCSP repsonse" )
  62 #define EACCES_NO_RESPONDER                                             \
  63         __einfo_error ( EINFO_EACCES_NO_RESPONDER )
  64 #define EINFO_EACCES_NO_RESPONDER                                       \
  65         __einfo_uniqify ( EINFO_EACCES, 0x05,                           \
  66                           "Missing OCSP responder certificate" )
  67 #define ENOTSUP_RESPONSE_TYPE                                           \
  68         __einfo_error ( EINFO_ENOTSUP_RESPONSE_TYPE )
  69 #define EINFO_ENOTSUP_RESPONSE_TYPE                                     \
  70         __einfo_uniqify ( EINFO_ENOTSUP, 0x01,                          \
  71                           "Unsupported OCSP response type" )
  72 #define ENOTSUP_RESPONDER_ID                                            \
  73         __einfo_error ( EINFO_ENOTSUP_RESPONDER_ID )
  74 #define EINFO_ENOTSUP_RESPONDER_ID                                      \
  75         __einfo_uniqify ( EINFO_ENOTSUP, 0x02,                          \
  76                           "Unsupported OCSP responder ID" )
  77 #define EPROTO_MALFORMED_REQUEST                                        \
  78         __einfo_error ( EINFO_EPROTO_MALFORMED_REQUEST )
  79 #define EINFO_EPROTO_MALFORMED_REQUEST                                  \
  80         __einfo_uniqify ( EINFO_EPROTO, OCSP_STATUS_MALFORMED_REQUEST,  \
  81                           "Illegal confirmation request" )
  82 #define EPROTO_INTERNAL_ERROR                                           \
  83         __einfo_error ( EINFO_EPROTO_INTERNAL_ERROR )
  84 #define EINFO_EPROTO_INTERNAL_ERROR                                     \
  85         __einfo_uniqify ( EINFO_EPROTO, OCSP_STATUS_INTERNAL_ERROR,     \
  86                           "Internal error in issuer" )
  87 #define EPROTO_TRY_LATER                                                \
  88         __einfo_error ( EINFO_EPROTO_TRY_LATER )
  89 #define EINFO_EPROTO_TRY_LATER                                          \
  90         __einfo_uniqify ( EINFO_EPROTO, OCSP_STATUS_TRY_LATER,          \
  91                           "Try again later" )
  92 #define EPROTO_SIG_REQUIRED                                             \
  93         __einfo_error ( EINFO_EPROTO_SIG_REQUIRED )
  94 #define EINFO_EPROTO_SIG_REQUIRED                                       \
  95         __einfo_uniqify ( EINFO_EPROTO, OCSP_STATUS_SIG_REQUIRED,       \
  96                           "Must sign the request" )
  97 #define EPROTO_UNAUTHORIZED                                             \
  98         __einfo_error ( EINFO_EPROTO_UNAUTHORIZED )
  99 #define EINFO_EPROTO_UNAUTHORIZED                                       \
 100         __einfo_uniqify ( EINFO_EPROTO, OCSP_STATUS_UNAUTHORIZED,       \
 101                           "Request unauthorized" )
 102 #define EPROTO_STATUS( status )                                         \
 103         EUNIQ ( EINFO_EPROTO, (status), EPROTO_MALFORMED_REQUEST,       \
 104                 EPROTO_INTERNAL_ERROR, EPROTO_TRY_LATER,                \
 105                 EPROTO_SIG_REQUIRED, EPROTO_UNAUTHORIZED )
 106
 107 /** OCSP digest algorithm */
 108 #define ocsp_digest_algorithm sha1_algorithm
 109
 110 /** OCSP digest algorithm identifier */
 111 static const uint8_t ocsp_algorithm_id[] =
 112         { OCSP_ALGORITHM_IDENTIFIER ( ASN1_OID_SHA1 ) };
 113
 114 /** OCSP basic response type */
 115 static const uint8_t oid_basic_response_type[] = { ASN1_OID_OCSP_BASIC };
 116
 117 /** OCSP basic response type cursor */
 118 static struct asn1_cursor oid_basic_response_type_cursor =
 119         ASN1_OID_CURSOR ( oid_basic_response_type );
 120
 121 /**
 122  * Free OCSP check
 123  *
 124  * @v refcnt            Reference count
 125  */
 126 static void ocsp_free ( struct refcnt *refcnt ) {
 127         struct ocsp_check *ocsp =
 128                 container_of ( refcnt, struct ocsp_check, refcnt );
 129
 130         x509_put ( ocsp->cert );
 131         x509_put ( ocsp->issuer );
 132         free ( ocsp->uri_string );
 133         free ( ocsp->request.builder.data );
 134         free ( ocsp->response.data );
 135         x509_put ( ocsp->response.signer );
 136         free ( ocsp );
 137 }
 138
 139 /**
 140  * Build OCSP request
 141  *
 142  * @v ocsp              OCSP check
 143  * @ret rc              Return status code
 144  */
 145 static int ocsp_request ( struct ocsp_check *ocsp ) {
 146         struct digest_algorithm *digest = &ocsp_digest_algorithm;
 147         struct asn1_builder *builder = &ocsp->request.builder;
 148         struct asn1_cursor *cert_id = &ocsp->request.cert_id;
 149         uint8_t digest_ctx[digest->ctxsize];
 150         uint8_t name_digest[digest->digestsize];
 151         uint8_t pubkey_digest[digest->digestsize];
 152         int rc;
 153
 154         /* Generate digests */
 155         digest_init ( digest, digest_ctx );
 156         digest_update ( digest, digest_ctx, ocsp->cert->issuer.raw.data,
 157                         ocsp->cert->issuer.raw.len );
 158         digest_final ( digest, digest_ctx, name_digest );
 159         digest_init ( digest, digest_ctx );
 160         digest_update ( digest, digest_ctx,
 161                         ocsp->issuer->subject.public_key.raw_bits.data,
 162                         ocsp->issuer->subject.public_key.raw_bits.len );
 163         digest_final ( digest, digest_ctx, pubkey_digest );
 164
 165         /* Construct request */
 166         if ( ( rc = ( asn1_prepend_raw ( builder, ocsp->cert->serial.raw.data,
 167                                          ocsp->cert->serial.raw.len ),
 168                       asn1_prepend ( builder, ASN1_OCTET_STRING,
 169                                      pubkey_digest, sizeof ( pubkey_digest ) ),
 170                       asn1_prepend ( builder, ASN1_OCTET_STRING,
 171                                      name_digest, sizeof ( name_digest ) ),
 172                       asn1_prepend ( builder, ASN1_SEQUENCE,
 173                                      ocsp_algorithm_id,
 174                                      sizeof ( ocsp_algorithm_id ) ),
 175                       asn1_wrap ( builder, ASN1_SEQUENCE ),
 176                       asn1_wrap ( builder, ASN1_SEQUENCE ),
 177                       asn1_wrap ( builder, ASN1_SEQUENCE ),
 178                       asn1_wrap ( builder, ASN1_SEQUENCE ),
 179                       asn1_wrap ( builder, ASN1_SEQUENCE ) ) ) != 0 ) {
 180                 DBGC ( ocsp, "OCSP %p \"%s\" could not build request: %s\n",
 181                        ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 182                 return rc;
 183         }
 184         DBGC2 ( ocsp, "OCSP %p \"%s\" request is:\n",
 185                 ocsp, x509_name ( ocsp->cert ) );
 186         DBGC2_HDA ( ocsp, 0, builder->data, builder->len );
 187
 188         /* Parse certificate ID for comparison with response */
 189         cert_id->data = builder->data;
 190         cert_id->len = builder->len;
 191         if ( ( rc = ( asn1_enter ( cert_id, ASN1_SEQUENCE ),
 192                       asn1_enter ( cert_id, ASN1_SEQUENCE ),
 193                       asn1_enter ( cert_id, ASN1_SEQUENCE ),
 194                       asn1_enter ( cert_id, ASN1_SEQUENCE ) ) ) != 0 ) {
 195                 DBGC ( ocsp, "OCSP %p \"%s\" could not locate certID: %s\n",
 196                        ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 197                 return rc;
 198         }
 199
 200         return 0;
 201 }
 202
 203 /**
 204  * Build OCSP URI string
 205  *
 206  * @v ocsp              OCSP check
 207  * @ret rc              Return status code
 208  */
 209 static int ocsp_uri_string ( struct ocsp_check *ocsp ) {
 210         struct x509_ocsp_responder *responder =
 211                 &ocsp->cert->extensions.auth_info.ocsp;
 212         struct uri path_uri;
 213         char *path_base64_string;
 214         char *path_uri_string;
 215         size_t path_len;
 216         size_t len;
 217         int rc;
 218
 219         /* Sanity check */
 220         if ( ! responder->uri.len ) {
 221                 DBGC ( ocsp, "OCSP %p \"%s\" has no OCSP URI\n",
 222                        ocsp, x509_name ( ocsp->cert ) );
 223                 rc = -ENOTTY;
 224                 goto err_no_uri;
 225         }
 226
 227         /* Base64-encode the request as the URI path */
 228         path_len = ( base64_encoded_len ( ocsp->request.builder.len )
 229                      + 1 /* NUL */ );
 230         path_base64_string = malloc ( path_len );
 231         if ( ! path_base64_string ) {
 232                 rc = -ENOMEM;
 233                 goto err_path_base64;
 234         }
 235         base64_encode ( ocsp->request.builder.data, ocsp->request.builder.len,
 236                         path_base64_string, path_len );
 237
 238         /* URI-encode the Base64-encoded request */
 239         memset ( &path_uri, 0, sizeof ( path_uri ) );
 240         path_uri.path = path_base64_string;
 241         path_uri_string = format_uri_alloc ( &path_uri );
 242         if ( ! path_uri_string ) {
 243                 rc = -ENOMEM;
 244                 goto err_path_uri;
 245         }
 246
 247         /* Construct URI string */
 248         len = ( responder->uri.len + strlen ( path_uri_string ) + 1 /* NUL */ );
 249         ocsp->uri_string = zalloc ( len );
 250         if ( ! ocsp->uri_string ) {
 251                 rc = -ENOMEM;
 252                 goto err_ocsp_uri;
 253         }
 254         memcpy ( ocsp->uri_string, responder->uri.data, responder->uri.len );
 255         strcpy ( &ocsp->uri_string[responder->uri.len], path_uri_string );
 256         DBGC2 ( ocsp, "OCSP %p \"%s\" URI is %s\n",
 257                 ocsp, x509_name ( ocsp->cert ), ocsp->uri_string );
 258
 259         /* Success */
 260         rc = 0;
 261
 262  err_ocsp_uri:
 263         free ( path_uri_string );
 264  err_path_uri:
 265         free ( path_base64_string );
 266  err_path_base64:
 267  err_no_uri:
 268         return rc;
 269 }
 270
 271 /**
 272  * Create OCSP check
 273  *
 274  * @v cert              Certificate to check
 275  * @v issuer            Issuing certificate
 276  * @ret ocsp            OCSP check
 277  * @ret rc              Return status code
 278  */
 279 int ocsp_check ( struct x509_certificate *cert,
 280                  struct x509_certificate *issuer,
 281                  struct ocsp_check **ocsp ) {
 282         int rc;
 283
 284         /* Sanity checks */
 285         assert ( cert != NULL );
 286         assert ( issuer != NULL );
 287         assert ( issuer->valid );
 288
 289         /* Allocate and initialise check */
 290         *ocsp = zalloc ( sizeof ( **ocsp ) );
 291         if ( ! *ocsp ) {
 292                 rc = -ENOMEM;
 293                 goto err_alloc;
 294         }
 295         ref_init ( &(*ocsp)->refcnt, ocsp_free );
 296         (*ocsp)->cert = x509_get ( cert );
 297         (*ocsp)->issuer = x509_get ( issuer );
 298
 299         /* Build request */
 300         if ( ( rc = ocsp_request ( *ocsp ) ) != 0 )
 301                 goto err_request;
 302
 303         /* Build URI string */
 304         if ( ( rc = ocsp_uri_string ( *ocsp ) ) != 0 )
 305                 goto err_uri_string;
 306
 307         return 0;
 308
 309  err_uri_string:
 310  err_request:
 311         ocsp_put ( *ocsp );
 312  err_alloc:
 313         *ocsp = NULL;
 314         return rc;
 315 }
 316
 317 /**
 318  * Parse OCSP response status
 319  *
 320  * @v ocsp              OCSP check
 321  * @v raw               ASN.1 cursor
 322  * @ret rc              Return status code
 323  */
 324 static int ocsp_parse_response_status ( struct ocsp_check *ocsp,
 325                                         const struct asn1_cursor *raw ) {
 326         struct asn1_cursor cursor;
 327         uint8_t status;
 328         int rc;
 329
 330         /* Enter responseStatus */
 331         memcpy ( &cursor, raw, sizeof ( cursor ) );
 332         if ( ( rc = asn1_enter ( &cursor, ASN1_ENUMERATED ) ) != 0 ) {
 333                 DBGC ( ocsp, "OCSP %p \"%s\" could not locate responseStatus: "
 334                        "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 335                 return rc;
 336         }
 337
 338         /* Extract response status */
 339         if ( cursor.len != sizeof ( status ) ) {
 340                 DBGC ( ocsp, "OCSP %p \"%s\" invalid status:\n",
 341                        ocsp, x509_name ( ocsp->cert ) );
 342                 DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 343                 return -EINVAL;
 344         }
 345         memcpy ( &status, cursor.data, sizeof ( status ) );
 346
 347         /* Check response status */
 348         if ( status != OCSP_STATUS_SUCCESSFUL ) {
 349                 DBGC ( ocsp, "OCSP %p \"%s\" response status %d\n",
 350                        ocsp, x509_name ( ocsp->cert ), status );
 351                 return EPROTO_STATUS ( status );
 352         }
 353
 354         return 0;
 355 }
 356
 357 /**
 358  * Parse OCSP response type
 359  *
 360  * @v ocsp              OCSP check
 361  * @v raw               ASN.1 cursor
 362  * @ret rc              Return status code
 363  */
 364 static int ocsp_parse_response_type ( struct ocsp_check *ocsp,
 365                                       const struct asn1_cursor *raw ) {
 366         struct asn1_cursor cursor;
 367
 368         /* Enter responseType */
 369         memcpy ( &cursor, raw, sizeof ( cursor ) );
 370         asn1_enter ( &cursor, ASN1_OID );
 371
 372         /* Check responseType is "basic" */
 373         if ( asn1_compare ( &oid_basic_response_type_cursor, &cursor ) != 0 ) {
 374                 DBGC ( ocsp, "OCSP %p \"%s\" response type not supported:\n",
 375                        ocsp, x509_name ( ocsp->cert ) );
 376                 DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 377                 return -ENOTSUP_RESPONSE_TYPE;
 378         }
 379
 380         return 0;
 381 }
 382
 383 /**
 384  * Compare responder's certificate name
 385  *
 386  * @v ocsp              OCSP check
 387  * @v cert              Certificate
 388  * @ret difference      Difference as returned by memcmp()
 389  */
 390 static int ocsp_compare_responder_name ( struct ocsp_check *ocsp,
 391                                          struct x509_certificate *cert ) {
 392         struct ocsp_responder *responder = &ocsp->response.responder;
 393
 394         /* Compare responder ID with certificate's subject */
 395         return asn1_compare ( &responder->id, &cert->subject.raw );
 396 }
 397
 398 /**
 399  * Compare responder's certificate public key hash
 400  *
 401  * @v ocsp              OCSP check
 402  * @v cert              Certificate
 403  * @ret difference      Difference as returned by memcmp()
 404  */
 405 static int ocsp_compare_responder_key_hash ( struct ocsp_check *ocsp,
 406                                              struct x509_certificate *cert ) {
 407         struct ocsp_responder *responder = &ocsp->response.responder;
 408         struct asn1_cursor key_hash;
 409         uint8_t ctx[SHA1_CTX_SIZE];
 410         uint8_t digest[SHA1_DIGEST_SIZE];
 411         int difference;
 412
 413         /* Enter responder key hash */
 414         memcpy ( &key_hash, &responder->id, sizeof ( key_hash ) );
 415         asn1_enter ( &key_hash, ASN1_OCTET_STRING );
 416
 417         /* Sanity check */
 418         difference = ( sizeof ( digest ) - key_hash.len );
 419         if ( difference )
 420                 return difference;
 421
 422         /* Generate SHA1 hash of certificate's public key */
 423         digest_init ( &sha1_algorithm, ctx );
 424         digest_update ( &sha1_algorithm, ctx,
 425                         cert->subject.public_key.raw_bits.data,
 426                         cert->subject.public_key.raw_bits.len );
 427         digest_final ( &sha1_algorithm, ctx, digest );
 428
 429         /* Compare responder key hash with hash of certificate's public key */
 430         return memcmp ( digest, key_hash.data, sizeof ( digest ) );
 431 }
 432
 433 /**
 434  * Parse OCSP responder ID
 435  *
 436  * @v ocsp              OCSP check
 437  * @v raw               ASN.1 cursor
 438  * @ret rc              Return status code
 439  */
 440 static int ocsp_parse_responder_id ( struct ocsp_check *ocsp,
 441                                      const struct asn1_cursor *raw ) {
 442         struct ocsp_responder *responder = &ocsp->response.responder;
 443         struct asn1_cursor *responder_id = &responder->id;
 444         unsigned int type;
 445
 446         /* Enter responder ID */
 447         memcpy ( responder_id, raw, sizeof ( *responder_id ) );
 448         type = asn1_type ( responder_id );
 449         asn1_enter_any ( responder_id );
 450
 451         /* Identify responder ID type */
 452         switch ( type ) {
 453         case ASN1_EXPLICIT_TAG ( 1 ) :
 454                 DBGC2 ( ocsp, "OCSP %p \"%s\" responder identified by name\n",
 455                         ocsp, x509_name ( ocsp->cert ) );
 456                 responder->compare = ocsp_compare_responder_name;
 457                 return 0;
 458         case ASN1_EXPLICIT_TAG ( 2 ) :
 459                 DBGC2 ( ocsp, "OCSP %p \"%s\" responder identified by key "
 460                         "hash\n", ocsp, x509_name ( ocsp->cert ) );
 461                 responder->compare = ocsp_compare_responder_key_hash;
 462                 return 0;
 463         default:
 464                 DBGC ( ocsp, "OCSP %p \"%s\" unsupported responder ID type "
 465                        "%d\n", ocsp, x509_name ( ocsp->cert ), type );
 466                 return -ENOTSUP_RESPONDER_ID;
 467         }
 468 }
 469
 470 /**
 471  * Parse OCSP certificate ID
 472  *
 473  * @v ocsp              OCSP check
 474  * @v raw               ASN.1 cursor
 475  * @ret rc              Return status code
 476  */
 477 static int ocsp_parse_cert_id ( struct ocsp_check *ocsp,
 478                                 const struct asn1_cursor *raw ) {
 479         struct asn1_cursor cursor;
 480
 481         /* Check certID matches request */
 482         memcpy ( &cursor, raw, sizeof ( cursor ) );
 483         asn1_shrink_any ( &cursor );
 484         if ( asn1_compare ( &cursor, &ocsp->request.cert_id ) != 0 ) {
 485                 DBGC ( ocsp, "OCSP %p \"%s\" certID mismatch:\n",
 486                        ocsp, x509_name ( ocsp->cert ) );
 487                 DBGC_HDA ( ocsp, 0, ocsp->request.cert_id.data,
 488                            ocsp->request.cert_id.len );
 489                 DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 490                 return -EACCES_CERT_MISMATCH;
 491         }
 492
 493         return 0;
 494 }
 495
 496 /**
 497  * Parse OCSP responses
 498  *
 499  * @v ocsp              OCSP check
 500  * @v raw               ASN.1 cursor
 501  * @ret rc              Return status code
 502  */
 503 static int ocsp_parse_responses ( struct ocsp_check *ocsp,
 504                                   const struct asn1_cursor *raw ) {
 505         struct ocsp_response *response = &ocsp->response;
 506         struct asn1_cursor cursor;
 507         int rc;
 508
 509         /* Enter responses */
 510         memcpy ( &cursor, raw, sizeof ( cursor ) );
 511         asn1_enter ( &cursor, ASN1_SEQUENCE );
 512
 513         /* Enter first singleResponse */
 514         asn1_enter ( &cursor, ASN1_SEQUENCE );
 515
 516         /* Parse certID */
 517         if ( ( rc = ocsp_parse_cert_id ( ocsp, &cursor ) ) != 0 )
 518                 return rc;
 519         asn1_skip_any ( &cursor );
 520
 521         /* Check certStatus */
 522         if ( asn1_type ( &cursor ) != ASN1_IMPLICIT_TAG ( 0 ) ) {
 523                 DBGC ( ocsp, "OCSP %p \"%s\" non-good certStatus:\n",
 524                        ocsp, x509_name ( ocsp->cert ) );
 525                 DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 526                 return -EACCES_CERT_STATUS;
 527         }
 528         asn1_skip_any ( &cursor );
 529
 530         /* Parse thisUpdate */
 531         if ( ( rc = asn1_generalized_time ( &cursor,
 532                                             &response->this_update ) ) != 0 ) {
 533                 DBGC ( ocsp, "OCSP %p \"%s\" could not parse thisUpdate: %s\n",
 534                        ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 535                 return rc;
 536         }
 537         DBGC2 ( ocsp, "OCSP %p \"%s\" this update was at time %lld\n",
 538                 ocsp, x509_name ( ocsp->cert ), response->this_update );
 539         asn1_skip_any ( &cursor );
 540
 541         /* Parse nextUpdate, if present */
 542         if ( asn1_type ( &cursor ) == ASN1_EXPLICIT_TAG ( 0 ) ) {
 543                 asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );
 544                 if ( ( rc = asn1_generalized_time ( &cursor,
 545                                              &response->next_update ) ) != 0 ) {
 546                         DBGC ( ocsp, "OCSP %p \"%s\" could not parse "
 547                                "nextUpdate: %s\n", ocsp,
 548                                x509_name ( ocsp->cert ), strerror ( rc ) );
 549                         return rc;
 550                 }
 551                 DBGC2 ( ocsp, "OCSP %p \"%s\" next update is at time %lld\n",
 552                         ocsp, x509_name ( ocsp->cert ), response->next_update );
 553         } else {
 554                 /* If no nextUpdate is present, this indicates that
 555                  * "newer revocation information is available all the
 556                  * time".  Actually, this indicates that there is no
 557                  * point to performing the OCSP check, since an
 558                  * attacker could replay the response at any future
 559                  * time and it would still be valid.
 560                  */
 561                 DBGC ( ocsp, "OCSP %p \"%s\" responder is a moron\n",
 562                        ocsp, x509_name ( ocsp->cert ) );
 563                 response->next_update = time ( NULL );
 564         }
 565
 566         return 0;
 567 }
 568
 569 /**
 570  * Parse OCSP response data
 571  *
 572  * @v ocsp              OCSP check
 573  * @v raw               ASN.1 cursor
 574  * @ret rc              Return status code
 575  */
 576 static int ocsp_parse_tbs_response_data ( struct ocsp_check *ocsp,
 577                                           const struct asn1_cursor *raw ) {
 578         struct ocsp_response *response = &ocsp->response;
 579         struct asn1_cursor cursor;
 580         int rc;
 581
 582         /* Record raw tbsResponseData */
 583         memcpy ( &cursor, raw, sizeof ( cursor ) );
 584         asn1_shrink_any ( &cursor );
 585         memcpy ( &response->tbs, &cursor, sizeof ( response->tbs ) );
 586
 587         /* Enter tbsResponseData */
 588         asn1_enter ( &cursor, ASN1_SEQUENCE );
 589
 590         /* Skip version, if present */
 591         asn1_skip_if_exists ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );
 592
 593         /* Parse responderID */
 594         if ( ( rc = ocsp_parse_responder_id ( ocsp, &cursor ) ) != 0 )
 595                 return rc;
 596         asn1_skip_any ( &cursor );
 597
 598         /* Skip producedAt */
 599         asn1_skip_any ( &cursor );
 600
 601         /* Parse responses */
 602         if ( ( rc = ocsp_parse_responses ( ocsp, &cursor ) ) != 0 )
 603                 return rc;
 604
 605         return 0;
 606 }
 607
 608 /**
 609  * Parse OCSP certificates
 610  *
 611  * @v ocsp              OCSP check
 612  * @v raw               ASN.1 cursor
 613  * @ret rc              Return status code
 614  */
 615 static int ocsp_parse_certs ( struct ocsp_check *ocsp,
 616                               const struct asn1_cursor *raw ) {
 617         struct ocsp_response *response = &ocsp->response;
 618         struct asn1_cursor cursor;
 619         struct x509_certificate *cert;
 620         int rc;
 621
 622         /* Enter certs */
 623         memcpy ( &cursor, raw, sizeof ( cursor ) );
 624         asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );
 625         asn1_enter ( &cursor, ASN1_SEQUENCE );
 626
 627         /* Parse certificate, if present.  The data structure permits
 628          * multiple certificates, but the protocol requires that the
 629          * OCSP signing certificate must either be the issuer itself,
 630          * or must be directly issued by the issuer (see RFC2560
 631          * section 4.2.2.2 "Authorized Responders").  We therefore
 632          * need to identify only the single certificate matching the
 633          * Responder ID.
 634          */
 635         while ( cursor.len ) {
 636
 637                 /* Parse certificate */
 638                 if ( ( rc = x509_certificate ( cursor.data, cursor.len,
 639                                                &cert ) ) != 0 ) {
 640                         DBGC ( ocsp, "OCSP %p \"%s\" could not parse "
 641                                "certificate: %s\n", ocsp,
 642                                x509_name ( ocsp->cert ), strerror ( rc ) );
 643                         DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 644                         return rc;
 645                 }
 646
 647                 /* Use if this certificate matches the responder ID */
 648                 if ( response->responder.compare ( ocsp, cert ) == 0 ) {
 649                         response->signer = cert;
 650                         DBGC2 ( ocsp, "OCSP %p \"%s\" response is signed by ",
 651                                 ocsp, x509_name ( ocsp->cert ) );
 652                         DBGC2 ( ocsp, "\"%s\"\n",
 653                                 x509_name ( response->signer ) );
 654                         return 0;
 655                 }
 656
 657                 /* Otherwise, discard this certificate */
 658                 x509_put ( cert );
 659                 asn1_skip_any ( &cursor );
 660         }
 661
 662         DBGC ( ocsp, "OCSP %p \"%s\" missing responder certificate\n",
 663                ocsp, x509_name ( ocsp->cert ) );
 664         return -EACCES_NO_RESPONDER;
 665 }
 666
 667 /**
 668  * Parse OCSP basic response
 669  *
 670  * @v ocsp              OCSP check
 671  * @v raw               ASN.1 cursor
 672  * @ret rc              Return status code
 673  */
 674 static int ocsp_parse_basic_response ( struct ocsp_check *ocsp,
 675                                        const struct asn1_cursor *raw ) {
 676         struct ocsp_response *response = &ocsp->response;
 677         struct asn1_algorithm **algorithm = &response->algorithm;
 678         struct asn1_bit_string *signature = &response->signature;
 679         struct asn1_cursor cursor;
 680         int rc;
 681
 682         /* Enter BasicOCSPResponse */
 683         memcpy ( &cursor, raw, sizeof ( cursor ) );
 684         asn1_enter ( &cursor, ASN1_SEQUENCE );
 685
 686         /* Parse tbsResponseData */
 687         if ( ( rc = ocsp_parse_tbs_response_data ( ocsp, &cursor ) ) != 0 )
 688                 return rc;
 689         asn1_skip_any ( &cursor );
 690
 691         /* Parse signatureAlgorithm */
 692         if ( ( rc = asn1_signature_algorithm ( &cursor, algorithm ) ) != 0 ) {
 693                 DBGC ( ocsp, "OCSP %p \"%s\" cannot parse signature "
 694                        "algorithm: %s\n",
 695                        ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 696                 return rc;
 697         }
 698         DBGC2 ( ocsp, "OCSP %p \"%s\" signature algorithm is %s\n",
 699                 ocsp, x509_name ( ocsp->cert ), (*algorithm)->name );
 700         asn1_skip_any ( &cursor );
 701
 702         /* Parse signature */
 703         if ( ( rc = asn1_integral_bit_string ( &cursor, signature ) ) != 0 ) {
 704                 DBGC ( ocsp, "OCSP %p \"%s\" cannot parse signature: %s\n",
 705                        ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 706                 return rc;
 707         }
 708         asn1_skip_any ( &cursor );
 709
 710         /* Parse certs, if present */
 711         if ( ( asn1_type ( &cursor ) == ASN1_EXPLICIT_TAG ( 0 ) ) &&
 712              ( ( rc = ocsp_parse_certs ( ocsp, &cursor ) ) != 0 ) )
 713                 return rc;
 714
 715         return 0;
 716 }
 717
 718 /**
 719  * Parse OCSP response bytes
 720  *
 721  * @v ocsp              OCSP check
 722  * @v raw               ASN.1 cursor
 723  * @ret rc              Return status code
 724  */
 725 static int ocsp_parse_response_bytes ( struct ocsp_check *ocsp,
 726                                        const struct asn1_cursor *raw ) {
 727         struct asn1_cursor cursor;
 728         int rc;
 729
 730         /* Enter responseBytes */
 731         memcpy ( &cursor, raw, sizeof ( cursor ) );
 732         asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );
 733         asn1_enter ( &cursor, ASN1_SEQUENCE );
 734
 735         /* Parse responseType */
 736         if ( ( rc = ocsp_parse_response_type ( ocsp, &cursor ) ) != 0 )
 737                 return rc;
 738         asn1_skip_any ( &cursor );
 739
 740         /* Enter response */
 741         asn1_enter ( &cursor, ASN1_OCTET_STRING );
 742
 743         /* Parse response */
 744         if ( ( rc = ocsp_parse_basic_response ( ocsp, &cursor ) ) != 0 )
 745                 return rc;
 746
 747         return 0;
 748 }
 749
 750 /**
 751  * Parse OCSP response
 752  *
 753  * @v ocsp              OCSP check
 754  * @v raw               ASN.1 cursor
 755  * @ret rc              Return status code
 756  */
 757 static int ocsp_parse_response ( struct ocsp_check *ocsp,
 758                                  const struct asn1_cursor *raw ) {
 759         struct asn1_cursor cursor;
 760         int rc;
 761
 762         /* Enter OCSPResponse */
 763         memcpy ( &cursor, raw, sizeof ( cursor ) );
 764         asn1_enter ( &cursor, ASN1_SEQUENCE );
 765
 766         /* Parse responseStatus */
 767         if ( ( rc = ocsp_parse_response_status ( ocsp, &cursor ) ) != 0 )
 768                 return rc;
 769         asn1_skip_any ( &cursor );
 770
 771         /* Parse responseBytes */
 772         if ( ( rc = ocsp_parse_response_bytes ( ocsp, &cursor ) ) != 0 )
 773                 return rc;
 774
 775         return 0;
 776 }
 777
 778 /**
 779  * Receive OCSP response
 780  *
 781  * @v ocsp              OCSP check
 782  * @v data              Response data
 783  * @v len               Length of response data
 784  * @ret rc              Return status code
 785  */
 786 int ocsp_response ( struct ocsp_check *ocsp, const void *data, size_t len ) {
 787         struct ocsp_response *response = &ocsp->response;
 788         struct asn1_cursor cursor;
 789         int rc;
 790
 791         /* Duplicate data */
 792         x509_put ( response->signer );
 793         response->signer = NULL;
 794         free ( response->data );
 795         response->data = malloc ( len );
 796         if ( ! response->data )
 797                 return -ENOMEM;
 798         memcpy ( response->data, data, len );
 799         cursor.data = response->data;
 800         cursor.len = len;
 801
 802         /* Parse response */
 803         if ( ( rc = ocsp_parse_response ( ocsp, &cursor ) ) != 0 )
 804                 return rc;
 805
 806         return 0;
 807 }
 808
 809 /**
 810  * OCSP dummy root certificate store
 811  *
 812  * OCSP validation uses no root certificates, since it takes place
 813  * only when there already exists a validated issuer certificate.
 814  */
 815 static struct x509_root ocsp_root = {
 816         .digest = &ocsp_digest_algorithm,
 817         .count = 0,
 818         .fingerprints = NULL,
 819 };
 820
 821 /**
 822  * Check OCSP response signature
 823  *
 824  * @v ocsp              OCSP check
 825  * @v signer            Signing certificate
 826  * @ret rc              Return status code
 827  */
 828 static int ocsp_check_signature ( struct ocsp_check *ocsp,
 829                                   struct x509_certificate *signer ) {
 830         struct ocsp_response *response = &ocsp->response;
 831         struct digest_algorithm *digest = response->algorithm->digest;
 832         struct pubkey_algorithm *pubkey = response->algorithm->pubkey;
 833         struct x509_public_key *public_key = &signer->subject.public_key;
 834         uint8_t digest_ctx[ digest->ctxsize ];
 835         uint8_t digest_out[ digest->digestsize ];
 836         uint8_t pubkey_ctx[ pubkey->ctxsize ];
 837         int rc;
 838
 839         /* Generate digest */
 840         digest_init ( digest, digest_ctx );
 841         digest_update ( digest, digest_ctx, response->tbs.data,
 842                         response->tbs.len );
 843         digest_final ( digest, digest_ctx, digest_out );
 844
 845         /* Initialise public-key algorithm */
 846         if ( ( rc = pubkey_init ( pubkey, pubkey_ctx, public_key->raw.data,
 847                                   public_key->raw.len ) ) != 0 ) {
 848                 DBGC ( ocsp, "OCSP %p \"%s\" could not initialise public key: "
 849                        "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 850                 goto err_init;
 851         }
 852
 853         /* Verify digest */
 854         if ( ( rc = pubkey_verify ( pubkey, pubkey_ctx, digest, digest_out,
 855                                     response->signature.data,
 856                                     response->signature.len ) ) != 0 ) {
 857                 DBGC ( ocsp, "OCSP %p \"%s\" signature verification failed: "
 858                        "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 859                 goto err_verify;
 860         }
 861
 862         DBGC2 ( ocsp, "OCSP %p \"%s\" signature is correct\n",
 863                 ocsp, x509_name ( ocsp->cert ) );
 864
 865  err_verify:
 866         pubkey_final ( pubkey, pubkey_ctx );
 867  err_init:
 868         return rc;
 869 }
 870
 871 /**
 872  * Validate OCSP response
 873  *
 874  * @v ocsp              OCSP check
 875  * @v time              Time at which to validate response
 876  * @ret rc              Return status code
 877  */
 878 int ocsp_validate ( struct ocsp_check *ocsp, time_t time ) {
 879         struct ocsp_response *response = &ocsp->response;
 880         struct x509_certificate *signer;
 881         int rc;
 882
 883         /* Sanity checks */
 884         assert ( response->data != NULL );
 885
 886         /* The response may include a signer certificate; if this is
 887          * not present then the response must have been signed
 888          * directly by the issuer.
 889          */
 890         signer = ( response->signer ? response->signer : ocsp->issuer );
 891
 892         /* Validate signer, if applicable.  If the signer is not the
 893          * issuer, then it must be signed directly by the issuer.
 894          */
 895         if ( signer != ocsp->issuer ) {
 896                 /* Forcibly invalidate the signer, since we need to
 897                  * ensure that it was signed by our issuer (and not
 898                  * some other issuer).  This prevents a sub-CA's OCSP
 899                  * certificate from fraudulently signing OCSP
 900                  * responses from the parent CA.
 901                  */
 902                 x509_invalidate ( signer );
 903                 if ( ( rc = x509_validate ( signer, ocsp->issuer, time,
 904                                             &ocsp_root ) ) != 0 ) {
 905                         DBGC ( ocsp, "OCSP %p \"%s\" could not validate ",
 906                                ocsp, x509_name ( ocsp->cert ) );
 907                         DBGC ( ocsp, "signer \"%s\": %s\n",
 908                                x509_name ( signer ), strerror ( rc ) );
 909                         return rc;
 910                 }
 911
 912                 /* If signer is not the issuer, then it must have the
 913                  * extendedKeyUsage id-kp-OCSPSigning.
 914                  */
 915                 if ( ! ( signer->extensions.ext_usage.bits &
 916                          X509_OCSP_SIGNING ) ) {
 917                         DBGC ( ocsp, "OCSP %p \"%s\" ",
 918                                ocsp, x509_name ( ocsp->cert ) );
 919                         DBGC ( ocsp, "signer \"%s\" is not an OCSP-signing "
 920                                "certificate\n", x509_name ( signer ) );
 921                         return -EACCES_NON_OCSP_SIGNING;
 922                 }
 923         }
 924
 925         /* Check OCSP response signature */
 926         if ( ( rc = ocsp_check_signature ( ocsp, signer ) ) != 0 )
 927                 return rc;
 928
 929         /* Check OCSP response is valid at the specified time
 930          * (allowing for some margin of error).
 931          */
 932         if ( response->this_update > ( time + TIMESTAMP_ERROR_MARGIN ) ) {
 933                 DBGC ( ocsp, "OCSP %p \"%s\" response is not yet valid (at "
 934                        "time %lld)\n", ocsp, x509_name ( ocsp->cert ), time );
 935                 return -EACCES_STALE;
 936         }
 937         if ( response->next_update < ( time - TIMESTAMP_ERROR_MARGIN ) ) {
 938                 DBGC ( ocsp, "OCSP %p \"%s\" response is stale (at time "
 939                        "%lld)\n", ocsp, x509_name ( ocsp->cert ), time );
 940                 return -EACCES_STALE;
 941         }
 942         DBGC2 ( ocsp, "OCSP %p \"%s\" response is valid (at time %lld)\n",
 943                 ocsp, x509_name ( ocsp->cert ), time );
 944
 945         /* Mark certificate as passing OCSP verification */
 946         ocsp->cert->extensions.auth_info.ocsp.good = 1;
 947
 948         /* Validate certificate against issuer */
 949         if ( ( rc = x509_validate ( ocsp->cert, ocsp->issuer, time,
 950                                     &ocsp_root ) ) != 0 ) {
 951                 DBGC ( ocsp, "OCSP %p \"%s\" could not validate certificate: "
 952                        "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 953                 return rc;
 954         }
 955         DBGC ( ocsp, "OCSP %p \"%s\" successfully validated ",
 956                ocsp, x509_name ( ocsp->cert ) );
 957         DBGC ( ocsp, "using \"%s\"\n", x509_name ( signer ) );
 958
 959         return 0;
 960 }