src/scepclient/scep.c

   1 /*
   2  * Copyright (C) 2012 Tobias Brunner
   3  * Copyright (C) 2005 Jan Hutter, Martin Willi
   4  * Hochschule fuer Technik Rapperswil
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2 of the License, or (at your
   9  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * for more details.
  15  */
  16
  17 #include <string.h>
  18 #include <stdlib.h>
  19
  20 #include <library.h>
  21 #include <utils/debug.h>
  22 #include <asn1/asn1.h>
  23 #include <asn1/asn1_parser.h>
  24 #include <asn1/oid.h>
  25 #include <crypto/pkcs9.h>
  26 #include <crypto/rngs/rng.h>
  27 #include <crypto/hashers/hasher.h>
  28
  29 #include "scep.h"
  30
  31 static const char *pkiStatus_values[] = { "0", "2", "3" };
  32
  33 static const char *pkiStatus_names[] = {
  34         "SUCCESS",
  35         "FAILURE",
  36         "PENDING",
  37         "UNKNOWN"
  38 };
  39
  40 static const char *msgType_values[] = { "3", "19", "20", "21", "22" };
  41
  42 static const char *msgType_names[] = {
  43         "CertRep",
  44         "PKCSReq",
  45         "GetCertInitial",
  46         "GetCert",
  47         "GetCRL",
  48         "Unknown"
  49 };
  50
  51 static const char *failInfo_reasons[] = {
  52         "badAlg - unrecognized or unsupported algorithm identifier",
  53         "badMessageCheck - integrity check failed",
  54         "badRequest - transaction not permitted or supported",
  55         "badTime - Message time field was not sufficiently close to the system time",
  56         "badCertId - No certificate could be identified matching the provided criteria"
  57 };
  58
  59 const scep_attributes_t empty_scep_attributes = {
  60         SCEP_Unknown_MSG   , /* msgType */
  61         SCEP_UNKNOWN       , /* pkiStatus */
  62         SCEP_unknown_REASON, /* failInfo */
  63         { NULL, 0 }        , /* transID */
  64         { NULL, 0 }        , /* senderNonce */
  65         { NULL, 0 }        , /* recipientNonce */
  66 };
  67
  68 /**
  69  * Extract X.501 attributes
  70  */
  71 void extract_attributes(pkcs7_t *pkcs7, enumerator_t *enumerator,
  72                                                 scep_attributes_t *attrs)
  73 {
  74         chunk_t attr;
  75
  76         if (pkcs7->get_attribute(pkcs7, OID_PKI_MESSAGE_TYPE, enumerator, &attr))
  77         {
  78                 scep_msg_t m;
  79
  80                 for (m = SCEP_CertRep_MSG; m < SCEP_Unknown_MSG; m++)
  81                 {
  82                         if (strncmp(msgType_values[m], attr.ptr, attr.len) == 0)
  83                         {
  84                                 attrs->msgType = m;
  85                         }
  86                 }
  87                 DBG2(DBG_APP, "messageType:  %s", msgType_names[attrs->msgType]);
  88                 free(attr.ptr);
  89         }
  90         if (pkcs7->get_attribute(pkcs7, OID_PKI_STATUS, enumerator, &attr))
  91         {
  92                 pkiStatus_t s;
  93
  94                 for (s = SCEP_SUCCESS; s < SCEP_UNKNOWN; s++)
  95                 {
  96                         if (strncmp(pkiStatus_values[s], attr.ptr, attr.len) == 0)
  97                         {
  98                                 attrs->pkiStatus = s;
  99                         }
 100                 }
 101                 DBG2(DBG_APP, "pkiStatus:    %s", pkiStatus_names[attrs->pkiStatus]);
 102                 free(attr.ptr);
 103         }
 104         if (pkcs7->get_attribute(pkcs7, OID_PKI_FAIL_INFO, enumerator, &attr))
 105         {
 106                 if (attr.len == 1 && *attr.ptr >= '0' && *attr.ptr <= '4')
 107                 {
 108                         attrs->failInfo = (failInfo_t)(*attr.ptr - '0');
 109                 }
 110                 if (attrs->failInfo != SCEP_unknown_REASON)
 111                 {
 112                         DBG1(DBG_APP, "failInfo:     %s", failInfo_reasons[attrs->failInfo]);
 113                 }
 114                 free(attr.ptr);
 115         }
 116
 117         pkcs7->get_attribute(pkcs7, OID_PKI_SENDER_NONCE, enumerator,
 118                                                  &attrs->senderNonce);
 119         pkcs7->get_attribute(pkcs7, OID_PKI_RECIPIENT_NONCE, enumerator,
 120                                                  &attrs->recipientNonce);
 121         pkcs7->get_attribute(pkcs7, OID_PKI_TRANS_ID, enumerator,
 122                                                  &attrs->transID);
 123 }
 124
 125 /**
 126  * Generates a unique fingerprint of the pkcs10 request
 127  * by computing an MD5 hash over it
 128  */
 129 chunk_t scep_generate_pkcs10_fingerprint(chunk_t pkcs10)
 130 {
 131         chunk_t digest = chunk_alloca(HASH_SIZE_MD5);
 132         hasher_t *hasher;
 133
 134         hasher = lib->crypto->create_hasher(lib->crypto, HASH_MD5);
 135         if (!hasher || !hasher->get_hash(hasher, pkcs10, digest.ptr))
 136         {
 137                 DESTROY_IF(hasher);
 138                 return chunk_empty;
 139         }
 140         hasher->destroy(hasher);
 141
 142         return chunk_to_hex(digest, NULL, FALSE);
 143 }
 144
 145 /**
 146  * Generate a transaction id as the MD5 hash of an public key
 147  * the transaction id is also used as a unique serial number
 148  */
 149 void scep_generate_transaction_id(public_key_t *key, chunk_t *transID,
 150                                                                   chunk_t *serialNumber)
 151 {
 152         chunk_t digest = chunk_alloca(HASH_SIZE_MD5);
 153         chunk_t keyEncoding = chunk_empty, keyInfo;
 154         hasher_t *hasher;
 155         bool msb_set;
 156         u_char *pos;
 157
 158         key->get_encoding(key, PUBKEY_ASN1_DER, &keyEncoding);
 159
 160         keyInfo = asn1_wrap(ASN1_SEQUENCE, "mm",
 161                                                 asn1_algorithmIdentifier(OID_RSA_ENCRYPTION),
 162                                                 asn1_bitstring("m", keyEncoding));
 163
 164         hasher = lib->crypto->create_hasher(lib->crypto, HASH_MD5);
 165         if (!hasher || !hasher->get_hash(hasher, keyInfo, digest.ptr))
 166         {
 167                 memset(digest.ptr, 0, digest.len);
 168         }
 169         DESTROY_IF(hasher);
 170         free(keyInfo.ptr);
 171
 172         /* is the most significant bit of the digest set? */
 173         msb_set = (*digest.ptr & 0x80) == 0x80;
 174
 175         /* allocate space for the serialNumber */
 176         serialNumber->len = msb_set + digest.len;
 177         serialNumber->ptr = malloc(serialNumber->len);
 178
 179         /* the serial number as the two's complement of the digest */
 180         pos = serialNumber->ptr;
 181         if (msb_set)
 182         {
 183                 *pos++ = 0x00;
 184         }
 185         memcpy(pos, digest.ptr, digest.len);
 186
 187         /* the transaction id is the serial number in hex format */
 188         *transID = chunk_to_hex(digest, NULL, TRUE);
 189 }
 190
 191 /**
 192  * Builds a pkcs7 enveloped and signed scep request
 193  */
 194 chunk_t scep_build_request(chunk_t data, chunk_t transID, scep_msg_t msg,
 195                                         certificate_t *enc_cert, encryption_algorithm_t enc_alg,
 196                                         size_t key_size, certificate_t *signer_cert,
 197                                         hash_algorithm_t digest_alg, private_key_t *private_key)
 198 {
 199         chunk_t request;
 200         container_t *container;
 201         char nonce[16];
 202         rng_t *rng;
 203         chunk_t senderNonce, msgType;
 204
 205         /* generate senderNonce */
 206         rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
 207         if (!rng || !rng->get_bytes(rng, sizeof(nonce), nonce))
 208         {
 209                 DESTROY_IF(rng);
 210                 return chunk_empty;
 211         }
 212         rng->destroy(rng);
 213
 214         /* encrypt data in enveloped-data PKCS#7 */
 215         container = lib->creds->create(lib->creds,
 216                                         CRED_CONTAINER, CONTAINER_PKCS7_ENVELOPED_DATA,
 217                                         BUILD_BLOB, data,
 218                                         BUILD_CERT, enc_cert,
 219                                         BUILD_ENCRYPTION_ALG, enc_alg,
 220                                         BUILD_KEY_SIZE, (int)key_size,
 221                                         BUILD_END);
 222         if (!container)
 223         {
 224                 return chunk_empty;
 225         }
 226         if (!container->get_encoding(container, &request))
 227         {
 228                 container->destroy(container);
 229                 return chunk_empty;
 230         }
 231         container->destroy(container);
 232
 233         /* sign enveloped-data in a signed-data PKCS#7 */
 234         senderNonce = asn1_wrap(ASN1_OCTET_STRING, "c", chunk_from_thing(nonce));
 235         transID = asn1_wrap(ASN1_PRINTABLESTRING, "c", transID);
 236         msgType = asn1_wrap(ASN1_PRINTABLESTRING, "c",
 237                                                 chunk_create((char*)msgType_values[msg],
 238                                                                          strlen(msgType_values[msg])));
 239
 240         container = lib->creds->create(lib->creds,
 241                                         CRED_CONTAINER, CONTAINER_PKCS7_SIGNED_DATA,
 242                                         BUILD_BLOB, request,
 243                                         BUILD_SIGNING_CERT, signer_cert,
 244                                         BUILD_SIGNING_KEY, private_key,
 245                                         BUILD_DIGEST_ALG, digest_alg,
 246                                         BUILD_PKCS7_ATTRIBUTE, OID_PKI_SENDER_NONCE, senderNonce,
 247                                         BUILD_PKCS7_ATTRIBUTE, OID_PKI_TRANS_ID, transID,
 248                                         BUILD_PKCS7_ATTRIBUTE, OID_PKI_MESSAGE_TYPE, msgType,
 249                                         BUILD_END);
 250
 251         free(request.ptr);
 252         free(senderNonce.ptr);
 253         free(transID.ptr);
 254         free(msgType.ptr);
 255
 256         if (!container)
 257         {
 258                 return chunk_empty;
 259         }
 260         if (!container->get_encoding(container, &request))
 261         {
 262                 container->destroy(container);
 263                 return chunk_empty;
 264         }
 265         container->destroy(container);
 266
 267         return request;
 268 }
 269
 270 /**
 271  * Converts a binary request to base64 with 64 characters per line
 272  * newline and '+' characters are escaped by %0A and %2B, respectively
 273  */
 274 static char* escape_http_request(chunk_t req)
 275 {
 276         char *escaped_req = NULL;
 277         char *p1, *p2;
 278         int lines = 0;
 279         int plus  = 0;
 280         int n     = 0;
 281
 282         /* compute and allocate the size of the base64-encoded request */
 283         int len = 1 + 4 * ((req.len + 2) / 3);
 284         char *encoded_req = malloc(len);
 285
 286         /* do the base64 conversion */
 287         chunk_t base64 = chunk_to_base64(req, encoded_req);
 288         len = base64.len + 1;
 289
 290         /* compute newline characters to be inserted every 64 characters */
 291         lines = (len - 2) / 64;
 292
 293         /* count number of + characters to be escaped */
 294         p1 = encoded_req;
 295         while (*p1 != '\0')
 296         {
 297                 if (*p1++ == '+')
 298                 {
 299                         plus++;
 300                 }
 301         }
 302
 303         escaped_req = malloc(len + 3 * (lines + plus));
 304
 305         /* escape special characters in the request */
 306         p1 = encoded_req;
 307         p2 = escaped_req;
 308         while (*p1 != '\0')
 309         {
 310                 if (n == 64)
 311                 {
 312                         memcpy(p2, "%0A", 3);
 313                         p2 += 3;
 314                         n = 0;
 315                 }
 316                 if (*p1 == '+')
 317                 {
 318                         memcpy(p2, "%2B", 3);
 319                         p2 += 3;
 320                 }
 321                 else
 322                 {
 323                         *p2++ = *p1;
 324                 }
 325                 p1++;
 326                 n++;
 327         }
 328         *p2 = '\0';
 329         free(encoded_req);
 330         return escaped_req;
 331 }
 332
 333 /**
 334  * Send a SCEP request via HTTP and wait for a response
 335  */
 336 bool scep_http_request(const char *url, chunk_t msg, scep_op_t op,
 337                                            bool http_get_request, chunk_t *response)
 338 {
 339         int len;
 340         status_t status;
 341         char *complete_url = NULL;
 342
 343         /* initialize response */
 344         *response = chunk_empty;
 345
 346         DBG2(DBG_APP, "sending scep request to '%s'", url);
 347
 348         if (op == SCEP_PKI_OPERATION)
 349         {
 350                 const char operation[] = "PKIOperation";
 351
 352                 if (http_get_request)
 353                 {
 354                         char *escaped_req = escape_http_request(msg);
 355
 356                         /* form complete url */
 357                         len = strlen(url) + 20 + strlen(operation) + strlen(escaped_req) + 1;
 358                         complete_url = malloc(len);
 359                         snprintf(complete_url, len, "%s?operation=%s&message=%s"
 360                                         , url, operation, escaped_req);
 361                         free(escaped_req);
 362
 363                         status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
 364                                                                                  FETCH_HTTP_VERSION_1_0,
 365                                                                                  FETCH_REQUEST_HEADER, "Pragma:",
 366                                                                                  FETCH_REQUEST_HEADER, "Host:",
 367                                                                                  FETCH_REQUEST_HEADER, "Accept:",
 368                                                                                  FETCH_END);
 369                 }
 370                 else /* HTTP_POST */
 371                 {
 372                         /* form complete url */
 373                         len = strlen(url) + 11 + strlen(operation) + 1;
 374                         complete_url = malloc(len);
 375                         snprintf(complete_url, len, "%s?operation=%s", url, operation);
 376
 377                         status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
 378                                                                                  FETCH_HTTP_VERSION_1_0,
 379                                                                                  FETCH_REQUEST_DATA, msg,
 380                                                                                  FETCH_REQUEST_TYPE, "",
 381                                                                                  FETCH_REQUEST_HEADER, "Expect:",
 382                                                                                  FETCH_END);
 383                 }
 384         }
 385         else  /* SCEP_GET_CA_CERT */
 386         {
 387                 const char operation[] = "GetCACert";
 388                 int i;
 389
 390                 /* escape spaces, TODO: complete URL escape */
 391                 for (i = 0; i < msg.len; i++)
 392                 {
 393                         if (msg.ptr[i] == ' ')
 394                         {
 395                                 msg.ptr[i] = '+';
 396                         }
 397                 }
 398
 399                 /* form complete url */
 400                 len = strlen(url) + 32 + strlen(operation) + msg.len + 1;
 401                 complete_url = malloc(len);
 402                 snprintf(complete_url, len, "%s?operation=%s&message=%.*s",
 403                                  url, operation, (int)msg.len, msg.ptr);
 404
 405                 status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
 406                                                                          FETCH_HTTP_VERSION_1_0,
 407                                                                          FETCH_END);
 408         }
 409
 410         free(complete_url);
 411         return (status == SUCCESS);
 412 }
 413
 414 err_t scep_parse_response(chunk_t response, chunk_t transID,
 415                                                   container_t **out, scep_attributes_t *attrs)
 416 {
 417         enumerator_t *enumerator;
 418         bool verified = FALSE;
 419         container_t *container;
 420         auth_cfg_t *auth;
 421
 422         container = lib->creds->create(lib->creds, CRED_CONTAINER, CONTAINER_PKCS7,
 423                                                                    BUILD_BLOB_ASN1_DER, response, BUILD_END);
 424         if (!container)
 425         {
 426                 return "error parsing the scep response";
 427         }
 428         if (container->get_type(container) != CONTAINER_PKCS7_SIGNED_DATA)
 429         {
 430                 container->destroy(container);
 431                 return "scep response is not PKCS#7 signed-data";
 432         }
 433
 434         enumerator = container->create_signature_enumerator(container);
 435         while (enumerator->enumerate(enumerator, &auth))
 436         {
 437                 verified = TRUE;
 438                 extract_attributes((pkcs7_t*)container, enumerator, attrs);
 439                 if (!chunk_equals(transID, attrs->transID))
 440                 {
 441                         enumerator->destroy(enumerator);
 442                         container->destroy(container);
 443                         return "transaction ID of scep response does not match";
 444                 }
 445         }
 446         enumerator->destroy(enumerator);
 447         if (!verified)
 448         {
 449                 container->destroy(container);
 450                 return "unable to verify PKCS#7 container";
 451         }
 452         *out = container;
 453         return NULL;
 454 }