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