src/security/PeerConnector.cc

   1 /*
   2  * Copyright (C) 1996-2016 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section 83    TLS Server/Peer negotiation */
  10
  11 #include "squid.h"
  12 #include "acl/FilledChecklist.h"
  13 #include "comm/Loops.h"
  14 #include "Downloader.h"
  15 #include "errorpage.h"
  16 #include "fde.h"
  17 #include "http/Stream.h"
  18 #include "HttpRequest.h"
  19 #include "security/NegotiationHistory.h"
  20 #include "security/PeerConnector.h"
  21 #include "SquidConfig.h"
  22 #if USE_OPENSSL
  23 #include "ssl/bio.h"
  24 #include "ssl/cert_validate_message.h"
  25 #include "ssl/Config.h"
  26 #include "ssl/helper.h"
  27 #endif
  28
  29 CBDATA_NAMESPACED_CLASS_INIT(Security, PeerConnector);
  30
  31 Security::PeerConnector::PeerConnector(const Comm::ConnectionPointer &aServerConn, AsyncCall::Pointer &aCallback, const AccessLogEntryPointer &alp, const time_t timeout) :
  32     AsyncJob("Security::PeerConnector"),
  33     serverConn(aServerConn),
  34     al(alp),
  35     callback(aCallback),
  36     negotiationTimeout(timeout),
  37     startTime(squid_curtime),
  38     useCertValidator_(true),
  39     certsDownloads(0)
  40 {
  41     debugs(83, 5, "Security::PeerConnector constructed, this=" << (void*)this);
  42     // if this throws, the caller's cb dialer is not our CbDialer
  43     Must(dynamic_cast<CbDialer*>(callback->getDialer()));
  44 }
  45
  46 Security::PeerConnector::~PeerConnector()
  47 {
  48     debugs(83, 5, "Security::PeerConnector destructed, this=" << (void*)this);
  49 }
  50
  51 bool Security::PeerConnector::doneAll() const
  52 {
  53     return (!callback || callback->canceled()) && AsyncJob::doneAll();
  54 }
  55
  56 /// Preps connection and SSL state. Calls negotiate().
  57 void
  58 Security::PeerConnector::start()
  59 {
  60     AsyncJob::start();
  61
  62     Security::SessionPointer tmp;
  63     if (prepareSocket() && initialize(tmp))
  64         negotiate();
  65     else
  66         mustStop("Security::PeerConnector TLS socket initialize failed");
  67 }
  68
  69 void
  70 Security::PeerConnector::commCloseHandler(const CommCloseCbParams &params)
  71 {
  72     debugs(83, 5, "FD " << params.fd << ", Security::PeerConnector=" << params.data);
  73     connectionClosed("Security::PeerConnector::commCloseHandler");
  74 }
  75
  76 void
  77 Security::PeerConnector::connectionClosed(const char *reason)
  78 {
  79     mustStop(reason);
  80     callback = NULL;
  81 }
  82
  83 bool
  84 Security::PeerConnector::prepareSocket()
  85 {
  86     const int fd = serverConnection()->fd;
  87     if (!Comm::IsConnOpen(serverConn) || fd_table[serverConn->fd].closing()) {
  88         connectionClosed("Security::PeerConnector::prepareSocket");
  89         return false;
  90     }
  91
  92     // watch for external connection closures
  93     typedef CommCbMemFunT<Security::PeerConnector, CommCloseCbParams> Dialer;
  94     closeHandler = JobCallback(9, 5, Dialer, this, Security::PeerConnector::commCloseHandler);
  95     comm_add_close_handler(fd, closeHandler);
  96     return true;
  97 }
  98
  99 bool
 100 Security::PeerConnector::initialize(Security::SessionPointer &serverSession)
 101 {
 102 #if USE_OPENSSL
 103     Security::ContextPointer ctx(getTlsContext());
 104     assert(ctx);
 105
 106     if (!Ssl::CreateClient(ctx, serverConnection(), "server https start")) {
 107         const auto xerrno = errno;
 108         const auto ssl_error = ERR_get_error();
 109         ErrorState *anErr = new ErrorState(ERR_SOCKET_FAILURE, Http::scInternalServerError, request.getRaw());
 110         anErr->xerrno = xerrno;
 111         debugs(83, DBG_IMPORTANT, "Error allocating TLS handle: " << Security::ErrorString(ssl_error));
 112         noteNegotiationDone(anErr);
 113         bail(anErr);
 114         return false;
 115     }
 116
 117     // A TLS/SSL session has now been created for the connection and stored in fd_table
 118     serverSession = fd_table[serverConnection()->fd].ssl;
 119
 120     // If CertValidation Helper used do not lookup checklist for errors,
 121     // but keep a list of errors to send it to CertValidator
 122     if (!Ssl::TheConfig.ssl_crt_validator) {
 123         // Create the ACL check list now, while we have access to more info.
 124         // The list is used in ssl_verify_cb() and is freed in ssl_free().
 125         if (acl_access *acl = ::Config.ssl_client.cert_error) {
 126             ACLFilledChecklist *check = new ACLFilledChecklist(acl, request.getRaw(), dash_str);
 127             check->al = al;
 128             // check->fd(fd); XXX: need client FD here
 129             SSL_set_ex_data(serverSession.get(), ssl_ex_index_cert_error_check, check);
 130         }
 131     }
 132
 133     return true;
 134 #else
 135     return false;
 136 #endif
 137 }
 138
 139 void
 140 Security::PeerConnector::setReadTimeout()
 141 {
 142     int timeToRead;
 143     if (negotiationTimeout) {
 144         const int timeUsed = squid_curtime - startTime;
 145         const int timeLeft = max(0, static_cast<int>(negotiationTimeout - timeUsed));
 146         timeToRead = min(static_cast<int>(::Config.Timeout.read), timeLeft);
 147     } else
 148         timeToRead = ::Config.Timeout.read;
 149     AsyncCall::Pointer nil;
 150     commSetConnTimeout(serverConnection(), timeToRead, nil);
 151 }
 152
 153 void
 154 Security::PeerConnector::recordNegotiationDetails()
 155 {
 156     const int fd = serverConnection()->fd;
 157     Security::SessionPointer session(fd_table[fd].ssl);
 158
 159     // retrieve TLS server negotiated information if any
 160     serverConnection()->tlsNegotiations()->retrieveNegotiatedInfo(session);
 161
 162 #if USE_OPENSSL
 163     // retrieve TLS parsed extra info
 164     BIO *b = SSL_get_rbio(session.get());
 165     Ssl::ServerBio *bio = static_cast<Ssl::ServerBio *>(b->ptr);
 166     if (const Security::TlsDetails::Pointer &details = bio->receivedHelloDetails())
 167         serverConnection()->tlsNegotiations()->retrieveParsedInfo(details);
 168 #endif
 169 }
 170
 171 void
 172 Security::PeerConnector::negotiate()
 173 {
 174     if (!Comm::IsConnOpen(serverConnection()))
 175         return;
 176
 177     const int fd = serverConnection()->fd;
 178     if (fd_table[fd].closing())
 179         return;
 180
 181 #if USE_OPENSSL
 182     const int result = SSL_connect(fd_table[fd].ssl.get());
 183 #else
 184     const int result = -1;
 185 #endif
 186     if (result <= 0) {
 187         handleNegotiateError(result);
 188         return; // we might be gone by now
 189     }
 190
 191     recordNegotiationDetails();
 192
 193     if (!sslFinalized())
 194         return;
 195
 196     callBack();
 197 }
 198
 199 bool
 200 Security::PeerConnector::sslFinalized()
 201 {
 202 #if USE_OPENSSL
 203     if (Ssl::TheConfig.ssl_crt_validator && useCertValidator_) {
 204         const int fd = serverConnection()->fd;
 205         Security::SessionPointer session(fd_table[fd].ssl);
 206
 207         Ssl::CertValidationRequest validationRequest;
 208         // WARNING: Currently we do not use any locking for any of the
 209         // members of the Ssl::CertValidationRequest class. In this code the
 210         // Ssl::CertValidationRequest object used only to pass data to
 211         // Ssl::CertValidationHelper::submit method.
 212         validationRequest.ssl = session.get();
 213         if (SBuf *dName = (SBuf *)SSL_get_ex_data(session.get(), ssl_ex_index_server))
 214             validationRequest.domainName = dName->c_str();
 215         if (Security::CertErrors *errs = static_cast<Security::CertErrors *>(SSL_get_ex_data(session.get(), ssl_ex_index_ssl_errors)))
 216             // validationRequest disappears on return so no need to cbdataReference
 217             validationRequest.errors = errs;
 218         try {
 219             debugs(83, 5, "Sending SSL certificate for validation to ssl_crtvd.");
 220             AsyncCall::Pointer call = asyncCall(83,5, "Security::PeerConnector::sslCrtvdHandleReply", Ssl::CertValidationHelper::CbDialer(this, &Security::PeerConnector::sslCrtvdHandleReply, nullptr));
 221             Ssl::CertValidationHelper::GetInstance()->sslSubmit(validationRequest, call);
 222             return false;
 223         } catch (const std::exception &e) {
 224             debugs(83, DBG_IMPORTANT, "ERROR: Failed to compose ssl_crtvd " <<
 225                    "request for " << validationRequest.domainName <<
 226                    " certificate: " << e.what() << "; will now block to " <<
 227                    "validate that certificate.");
 228             // fall through to do blocking in-process generation.
 229             ErrorState *anErr = new ErrorState(ERR_GATEWAY_FAILURE, Http::scInternalServerError, request.getRaw());
 230
 231             noteNegotiationDone(anErr);
 232             bail(anErr);
 233             serverConn->close();
 234             return true;
 235         }
 236     }
 237 #endif
 238
 239     noteNegotiationDone(NULL);
 240     return true;
 241 }
 242
 243 #if USE_OPENSSL
 244 void
 245 Security::PeerConnector::sslCrtvdHandleReply(Ssl::CertValidationResponse::Pointer validationResponse)
 246 {
 247     Must(validationResponse != NULL);
 248
 249     Ssl::ErrorDetail *errDetails = NULL;
 250     bool validatorFailed = false;
 251     if (!Comm::IsConnOpen(serverConnection())) {
 252         return;
 253     }
 254
 255     if (Debug::Enabled(83, 5)) {
 256         Security::SessionPointer ssl(fd_table[serverConnection()->fd].ssl);
 257         SBuf *server = static_cast<SBuf *>(SSL_get_ex_data(ssl.get(), ssl_ex_index_server));
 258         debugs(83,5, RawPointer("host", server) << " cert validation result: " << validationResponse->resultCode);
 259     }
 260
 261     if (validationResponse->resultCode == ::Helper::Error) {
 262         if (Security::CertErrors *errs = sslCrtvdCheckForErrors(*validationResponse, errDetails)) {
 263             Security::SessionPointer session(fd_table[serverConnection()->fd].ssl);
 264             Security::CertErrors *oldErrs = static_cast<Security::CertErrors*>(SSL_get_ex_data(session.get(), ssl_ex_index_ssl_errors));
 265             SSL_set_ex_data(session.get(), ssl_ex_index_ssl_errors,  (void *)errs);
 266             delete oldErrs;
 267         }
 268     } else if (validationResponse->resultCode != ::Helper::Okay)
 269         validatorFailed = true;
 270
 271     if (!errDetails && !validatorFailed) {
 272         noteNegotiationDone(NULL);
 273         callBack();
 274         return;
 275     }
 276
 277     ErrorState *anErr = NULL;
 278     if (validatorFailed) {
 279         anErr = new ErrorState(ERR_GATEWAY_FAILURE, Http::scInternalServerError, request.getRaw());
 280     }  else {
 281         anErr =  new ErrorState(ERR_SECURE_CONNECT_FAIL, Http::scServiceUnavailable, request.getRaw());
 282         anErr->detail = errDetails;
 283         /*anErr->xerrno= Should preserved*/
 284     }
 285
 286     noteNegotiationDone(anErr);
 287     bail(anErr);
 288     serverConn->close();
 289     return;
 290 }
 291 #endif
 292
 293 #if USE_OPENSSL
 294 /// Checks errors in the cert. validator response against sslproxy_cert_error.
 295 /// The first honored error, if any, is returned via errDetails parameter.
 296 /// The method returns all seen errors except SSL_ERROR_NONE as Security::CertErrors.
 297 Security::CertErrors *
 298 Security::PeerConnector::sslCrtvdCheckForErrors(Ssl::CertValidationResponse const &resp, Ssl::ErrorDetail *& errDetails)
 299 {
 300     ACLFilledChecklist *check = NULL;
 301     if (acl_access *acl = ::Config.ssl_client.cert_error) {
 302         check = new ACLFilledChecklist(acl, request.getRaw(), dash_str);
 303         check->al = al;
 304     }
 305
 306     Security::CertErrors *errs = nullptr;
 307     Security::SessionPointer session(fd_table[serverConnection()->fd].ssl);
 308     typedef Ssl::CertValidationResponse::RecvdErrors::const_iterator SVCRECI;
 309     for (SVCRECI i = resp.errors.begin(); i != resp.errors.end(); ++i) {
 310         debugs(83, 7, "Error item: " << i->error_no << " " << i->error_reason);
 311
 312         assert(i->error_no != SSL_ERROR_NONE);
 313
 314         if (!errDetails) {
 315             bool allowed = false;
 316             if (check) {
 317                 check->sslErrors = new Security::CertErrors(Security::CertError(i->error_no, i->cert, i->error_depth));
 318                 if (check->fastCheck() == ACCESS_ALLOWED)
 319                     allowed = true;
 320             }
 321             // else the Config.ssl_client.cert_error access list is not defined
 322             // and the first error will cause the error page
 323
 324             if (allowed) {
 325                 debugs(83, 3, "bypassing SSL error " << i->error_no << " in " << "buffer");
 326             } else {
 327                 debugs(83, 5, "confirming SSL error " << i->error_no);
 328                 X509 *brokenCert = i->cert.get();
 329                 Security::CertPointer peerCert(SSL_get_peer_certificate(session.get()));
 330                 const char *aReason = i->error_reason.empty() ? NULL : i->error_reason.c_str();
 331                 errDetails = new Ssl::ErrorDetail(i->error_no, peerCert.get(), brokenCert, aReason);
 332             }
 333             if (check) {
 334                 delete check->sslErrors;
 335                 check->sslErrors = NULL;
 336             }
 337         }
 338
 339         if (!errs)
 340             errs = new Security::CertErrors(Security::CertError(i->error_no, i->cert, i->error_depth));
 341         else
 342             errs->push_back_unique(Security::CertError(i->error_no, i->cert, i->error_depth));
 343     }
 344     if (check)
 345         delete check;
 346
 347     return errs;
 348 }
 349 #endif
 350
 351 /// A wrapper for Comm::SetSelect() notifications.
 352 void
 353 Security::PeerConnector::NegotiateSsl(int, void *data)
 354 {
 355     PeerConnector *pc = static_cast<Security::PeerConnector *>(data);
 356     // Use job calls to add done() checks and other job logic/protections.
 357     CallJobHere(83, 7, pc, Security::PeerConnector, negotiate);
 358 }
 359
 360 void
 361 Security::PeerConnector::handleNegotiateError(const int ret)
 362 {
 363 #if USE_OPENSSL
 364     const int fd = serverConnection()->fd;
 365     unsigned long ssl_lib_error = SSL_ERROR_NONE;
 366     Security::SessionPointer session(fd_table[fd].ssl);
 367     const int ssl_error = SSL_get_error(session.get(), ret);
 368
 369     switch (ssl_error) {
 370     case SSL_ERROR_WANT_READ:
 371         noteWantRead();
 372         return;
 373
 374     case SSL_ERROR_WANT_WRITE:
 375         noteWantWrite();
 376         return;
 377
 378     case SSL_ERROR_SSL:
 379     case SSL_ERROR_SYSCALL:
 380         ssl_lib_error = ERR_get_error();
 381         // proceed to the general error handling code
 382         break;
 383     default:
 384         // no special error handling for all other errors
 385         break;
 386     }
 387
 388     // Log connection details, if any
 389     recordNegotiationDetails();
 390     noteNegotiationError(ret, ssl_error, ssl_lib_error);
 391 #endif
 392 }
 393
 394 void
 395 Security::PeerConnector::noteWantRead()
 396 {
 397     const int fd = serverConnection()->fd;
 398 #if USE_OPENSSL
 399     Security::SessionPointer session(fd_table[fd].ssl);
 400     BIO *b = SSL_get_rbio(session.get());
 401     Ssl::ServerBio *srvBio = static_cast<Ssl::ServerBio *>(b->ptr);
 402     if (srvBio->holdRead()) {
 403         if (srvBio->gotHello()) {
 404             if (checkForMissingCertificates())
 405                 return; // Wait to download certificates before proceed.
 406
 407             srvBio->holdRead(false);
 408             // schedule a negotiateSSl to allow openSSL parse received data
 409             Security::PeerConnector::NegotiateSsl(fd, this);
 410             return;
 411         } else if (srvBio->gotHelloFailed()) {
 412             srvBio->holdRead(false);
 413             debugs(83, DBG_IMPORTANT, "Error parsing SSL Server Hello Message on FD " << fd);
 414             // schedule a negotiateSSl to allow openSSL parse received data
 415             Security::PeerConnector::NegotiateSsl(fd, this);
 416             return;
 417         }
 418     }
 419 #endif
 420     setReadTimeout();
 421     Comm::SetSelect(fd, COMM_SELECT_READ, &NegotiateSsl, this, 0);
 422 }
 423
 424 void
 425 Security::PeerConnector::noteWantWrite()
 426 {
 427     const int fd = serverConnection()->fd;
 428     Comm::SetSelect(fd, COMM_SELECT_WRITE, &NegotiateSsl, this, 0);
 429     return;
 430 }
 431
 432 void
 433 Security::PeerConnector::noteNegotiationError(const int ret, const int ssl_error, const int ssl_lib_error)
 434 {
 435 #if USE_OPENSSL // not used unless OpenSSL enabled.
 436 #if defined(EPROTO)
 437     int sysErrNo = EPROTO;
 438 #else
 439     int sysErrNo = EACCES;
 440 #endif
 441
 442     // store/report errno when ssl_error is SSL_ERROR_SYSCALL, ssl_lib_error is 0, and ret is -1
 443     if (ssl_error == SSL_ERROR_SYSCALL && ret == -1 && ssl_lib_error == 0)
 444         sysErrNo = errno;
 445
 446     const int fd = serverConnection()->fd;
 447     debugs(83, DBG_IMPORTANT, "Error negotiating SSL on FD " << fd <<
 448            ": " << Security::ErrorString(ssl_lib_error) << " (" <<
 449            ssl_error << "/" << ret << "/" << errno << ")");
 450
 451     ErrorState *anErr = NULL;
 452     if (request != NULL)
 453         anErr = ErrorState::NewForwarding(ERR_SECURE_CONNECT_FAIL, request.getRaw());
 454     else
 455         anErr = new ErrorState(ERR_SECURE_CONNECT_FAIL, Http::scServiceUnavailable, NULL);
 456     anErr->xerrno = sysErrNo;
 457
 458     Security::SessionPointer session(fd_table[fd].ssl);
 459     Ssl::ErrorDetail *errFromFailure = static_cast<Ssl::ErrorDetail *>(SSL_get_ex_data(session.get(), ssl_ex_index_ssl_error_detail));
 460     if (errFromFailure != NULL) {
 461         // The errFromFailure is attached to the ssl object
 462         // and will be released when ssl object destroyed.
 463         // Copy errFromFailure to a new Ssl::ErrorDetail object
 464         anErr->detail = new Ssl::ErrorDetail(*errFromFailure);
 465     } else {
 466         // server_cert can be NULL here
 467         X509 *server_cert = SSL_get_peer_certificate(session.get());
 468         anErr->detail = new Ssl::ErrorDetail(SQUID_ERR_SSL_HANDSHAKE, server_cert, NULL);
 469         X509_free(server_cert);
 470     }
 471
 472     if (ssl_lib_error != SSL_ERROR_NONE)
 473         anErr->detail->setLibError(ssl_lib_error);
 474
 475     noteNegotiationDone(anErr);
 476     bail(anErr);
 477 #endif
 478 }
 479
 480 void
 481 Security::PeerConnector::bail(ErrorState *error)
 482 {
 483     Must(error); // or the recepient will not know there was a problem
 484     Must(callback != NULL);
 485     CbDialer *dialer = dynamic_cast<CbDialer*>(callback->getDialer());
 486     Must(dialer);
 487     dialer->answer().error = error;
 488
 489     callBack();
 490     // Our job is done. The callabck recepient will probably close the failed
 491     // peer connection and try another peer or go direct (if possible). We
 492     // can close the connection ourselves (our error notification would reach
 493     // the recepient before the fd-closure notification), but we would rather
 494     // minimize the number of fd-closure notifications and let the recepient
 495     // manage the TCP state of the connection.
 496 }
 497
 498 void
 499 Security::PeerConnector::callBack()
 500 {
 501     AsyncCall::Pointer cb = callback;
 502     // Do this now so that if we throw below, swanSong() assert that we _tried_
 503     // to call back holds.
 504     callback = NULL; // this should make done() true
 505
 506     // remove close handler
 507     comm_remove_close_handler(serverConnection()->fd, closeHandler);
 508
 509     CbDialer *dialer = dynamic_cast<CbDialer*>(cb->getDialer());
 510     Must(dialer);
 511     dialer->answer().conn = serverConnection();
 512     ScheduleCallHere(cb);
 513 }
 514
 515 void
 516 Security::PeerConnector::swanSong()
 517 {
 518     // XXX: unregister fd-closure monitoring and CommSetSelect interest, if any
 519     AsyncJob::swanSong();
 520     if (callback != NULL) { // paranoid: we have left the caller waiting
 521         debugs(83, DBG_IMPORTANT, "BUG: Unexpected state while connecting to a cache_peer or origin server");
 522         ErrorState *anErr = new ErrorState(ERR_GATEWAY_FAILURE, Http::scInternalServerError, request.getRaw());
 523         bail(anErr);
 524         assert(!callback);
 525         return;
 526     }
 527 }
 528
 529 const char *
 530 Security::PeerConnector::status() const
 531 {
 532     static MemBuf buf;
 533     buf.reset();
 534
 535     // TODO: redesign AsyncJob::status() API to avoid this
 536     // id and stop reason reporting duplication.
 537     buf.append(" [", 2);
 538     if (stopReason != NULL) {
 539         buf.append("Stopped, reason:", 16);
 540         buf.appendf("%s",stopReason);
 541     }
 542     if (serverConn != NULL)
 543         buf.appendf(" FD %d", serverConn->fd);
 544     buf.appendf(" %s%u]", id.prefix(), id.value);
 545     buf.terminate();
 546
 547     return buf.content();
 548 }
 549
 550 #if USE_OPENSSL
 551 /// CallDialer to allow use Downloader objects within PeerConnector class.
 552 class PeerConnectorCertDownloaderDialer: public Downloader::CbDialer
 553 {
 554 public:
 555     typedef void (Security::PeerConnector::*Method)(SBuf &object, int status);
 556
 557     PeerConnectorCertDownloaderDialer(Method method, Security::PeerConnector *pc):
 558         method_(method),
 559         peerConnector_(pc) {}
 560
 561     /* CallDialer API */
 562     virtual bool canDial(AsyncCall &call) { return peerConnector_.valid(); }
 563     virtual void dial(AsyncCall &call) { ((&(*peerConnector_))->*method_)(object, status); }
 564     Method method_; ///< The Security::PeerConnector method to dial
 565     CbcPointer<Security::PeerConnector> peerConnector_; ///< The Security::PeerConnector object
 566 };
 567
 568 void
 569 Security::PeerConnector::startCertDownloading(SBuf &url)
 570 {
 571     AsyncCall::Pointer certCallback = asyncCall(81, 4,
 572                                       "Security::PeerConnector::certDownloadingDone",
 573                                       PeerConnectorCertDownloaderDialer(&Security::PeerConnector::certDownloadingDone, this));
 574
 575     const Downloader *csd = (request ? dynamic_cast<const Downloader*>(request->downloader.valid()) : nullptr);
 576     Downloader *dl = new Downloader(url, certCallback, csd ? csd->nestedLevel() + 1 : 1);
 577     AsyncJob::Start(dl);
 578 }
 579
 580 void
 581 Security::PeerConnector::certDownloadingDone(SBuf &obj, int downloadStatus)
 582 {
 583     ++certsDownloads;
 584     debugs(81, 5, "Certificate downloading status: " << downloadStatus << " certificate size: " << obj.length());
 585
 586     // get ServerBio from SSL object
 587     const int fd = serverConnection()->fd;
 588     Security::SessionPointer session(fd_table[fd].ssl);
 589     BIO *b = SSL_get_rbio(session.get());
 590     Ssl::ServerBio *srvBio = static_cast<Ssl::ServerBio *>(b->ptr);
 591
 592     // Parse Certificate. Assume that it is in DER format.
 593     // According to RFC 4325:
 594     //  The server must provide a DER encoded certificate or a collection
 595     // collection of certificates in a "certs-only" CMS message.
 596     //  The applications MUST accept DER encoded certificates and SHOULD
 597     // be able to accept collection of certificates.
 598     // TODO: support collection of certificates
 599     const unsigned char *raw = (const unsigned char*)obj.rawContent();
 600     if (X509 *cert = d2i_X509(NULL, &raw, obj.length())) {
 601         char buffer[1024];
 602         debugs(81, 5, "Retrieved certificate: " << X509_NAME_oneline(X509_get_subject_name(cert), buffer, 1024));
 603         const Security::CertList &certsList = srvBio->serverCertificatesIfAny();
 604         if (const char *issuerUri = Ssl::uriOfIssuerIfMissing(cert,  certsList)) {
 605             urlsOfMissingCerts.push(SBuf(issuerUri));
 606         }
 607         Ssl::SSL_add_untrusted_cert(session.get(), cert);
 608     }
 609
 610     // Check if there are URIs to download from and if yes start downloading
 611     // the first in queue.
 612     if (urlsOfMissingCerts.size() && certsDownloads <= MaxCertsDownloads) {
 613         startCertDownloading(urlsOfMissingCerts.front());
 614         urlsOfMissingCerts.pop();
 615         return;
 616     }
 617
 618     srvBio->holdRead(false);
 619     Security::PeerConnector::NegotiateSsl(serverConnection()->fd, this);
 620 }
 621
 622 bool
 623 Security::PeerConnector::checkForMissingCertificates()
 624 {
 625     // Check for nested SSL certificates downloads. For example when the
 626     // certificate located in an SSL site which requires to download a
 627     // a missing certificate (... from an SSL site which requires to ...).
 628
 629     const Downloader *csd = (request ? request->downloader.get() : nullptr);
 630     if (csd && csd->nestedLevel() >= MaxNestedDownloads)
 631         return false;
 632
 633     const int fd = serverConnection()->fd;
 634     Security::SessionPointer session(fd_table[fd].ssl);
 635     BIO *b = SSL_get_rbio(session.get());
 636     Ssl::ServerBio *srvBio = static_cast<Ssl::ServerBio *>(b->ptr);
 637     const Security::CertList &certs = srvBio->serverCertificatesIfAny();
 638
 639     if (certs.size()) {
 640         debugs(83, 5, "SSL server sent " << certs.size() << " certificates");
 641         Ssl::missingChainCertificatesUrls(urlsOfMissingCerts, certs);
 642         if (urlsOfMissingCerts.size()) {
 643             startCertDownloading(urlsOfMissingCerts.front());
 644             urlsOfMissingCerts.pop();
 645             return true;
 646         }
 647     }
 648
 649     return false;
 650 }
 651 #endif //USE_OPENSSL
 652