Remove the last of the TLS fallback code.

net/socket/ssl_client_socket_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/socket/ssl_client_socket_impl.h"
 
 #include <errno.h>
 #include <openssl/bio.h>
 #include <openssl/bytestring.h>
 #include <openssl/err.h>
@@ skipping 777 matching lines @@
 
   SSLConnectionStatusSetCipherSuite(
       static_cast<uint16_t>(SSL_CIPHER_get_id(cipher)),
       &ssl_info->connection_status);
   SSLConnectionStatusSetVersion(GetNetSSLVersion(ssl_),
                                 &ssl_info->connection_status);
 
   if (!SSL_get_secure_renegotiation_support(ssl_))
     ssl_info->connection_status |= SSL_CONNECTION_NO_RENEGOTIATION_EXTENSION;
 
-  if (ssl_config_.version_fallback)
-    ssl_info->connection_status |= SSL_CONNECTION_VERSION_FALLBACK;

[mmenke, 2016/10/03 16:01:03]

Can we remove SSL_CONNECTION_VERSION_FALLBACK from
ssl_connection_status_flags.h?

[davidben, 2016/10/03 19:09:24]

Done. Note this changes behavior slightly, but I think it's fine? Updated commit
description accordingly. The other option is we drop those cache entries on the
floor, which isn't wrong.

[mmenke, 2016/10/03 20:12:01]

I think it's fine, but I'd also be fine with dropping them.

-
   ssl_info->handshake_type = SSL_session_reused(ssl_)
                                  ? SSLInfo::HANDSHAKE_RESUME
                                  : SSLInfo::HANDSHAKE_FULL;
 
   return true;
 }
 
 void SSLClientSocketImpl::GetConnectionAttempts(ConnectionAttempts* out) const {
   out->clear();
 }
@@ skipping 153 matching lines @@
 
   // Same as above, this time for the SSL mode.
   SslSetClearMask mode;
 
   mode.ConfigureFlag(SSL_MODE_RELEASE_BUFFERS, true);
   mode.ConfigureFlag(SSL_MODE_CBC_RECORD_SPLITTING, true);
 
   mode.ConfigureFlag(SSL_MODE_ENABLE_FALSE_START,
                      ssl_config_.false_start_enabled);
 
-  mode.ConfigureFlag(SSL_MODE_SEND_FALLBACK_SCSV, ssl_config_.version_fallback);
-
   SSL_set_mode(ssl_, mode.set_mask);
   SSL_clear_mode(ssl_, mode.clear_mask);
 
   // Use BoringSSL defaults, but disable HMAC-SHA256 and HMAC-SHA384 ciphers
   // (note that SHA256 and SHA384 only select legacy CBC ciphers). Also disable
   // DHE_RSA_WITH_AES_256_GCM_SHA384. Historically, AES_256_GCM was not
   // supported. As DHE is being deprecated, don't add a cipher only to remove it
   // immediately.
   std::string command;
   if (SSLClientSocket::IsPostQuantumExperimentEnabled()) {
@@ skipping 164 matching lines @@
   }
 
   next_handshake_state_ = STATE_HANDSHAKE_COMPLETE;
   return net_error;
 }
 
 int SSLClientSocketImpl::DoHandshakeComplete(int result) {
   if (result < 0)
     return result;
 
-  if (ssl_config_.version_fallback &&
-      ssl_config_.version_max < ssl_config_.version_fallback_min) {
-    return ERR_SSL_FALLBACK_BEYOND_MINIMUM_VERSION;
-  }
-
   // DHE is offered on the deprecated cipher fallback and then rejected
   // afterwards. This is to aid in diagnosing connection failures because a
   // server requires DHE ciphers.
   //
   // TODO(davidben): A few releases after DHE's removal, remove this logic.
   if (!ssl_config_.dhe_enabled &&
       SSL_CIPHER_is_DHE(SSL_get_current_cipher(ssl_))) {
     return ERR_SSL_OBSOLETE_CIPHER;
   }
 
@@ skipping 848 matching lines @@
 
 void SSLClientSocketImpl::AddCTInfoToSSLInfo(SSLInfo* ssl_info) const {
   ssl_info->UpdateCertificateTransparencyInfo(ct_verify_result_);
 }
 
 std::string SSLClientSocketImpl::GetSessionCacheKey() const {
   std::string result = host_and_port_.ToString();
   result.append("/");
   result.append(ssl_session_cache_shard_);
 
-  // Shard the session cache based on maximum protocol version. This causes
-  // fallback connections to use a separate session cache.
-  result.append("/");
-  switch (ssl_config_.version_max) {
-    case SSL_PROTOCOL_VERSION_TLS1:
-      result.append("tls1");
-      break;
-    case SSL_PROTOCOL_VERSION_TLS1_1:
-      result.append("tls1.1");
-      break;
-    case SSL_PROTOCOL_VERSION_TLS1_2:
-      result.append("tls1.2");
-      break;
-    case SSL_PROTOCOL_VERSION_TLS1_3:
-      result.append("tls1.3");
-      break;
-    default:
-      NOTREACHED();
-  }
-
   result.append("/");
   if (ssl_config_.deprecated_cipher_suites_enabled)
     result.append("deprecated");
 
   result.append("/");
   if (ssl_config_.channel_id_enabled)
     result.append("channelid");
 
   return result;
 }
@@ skipping 219 matching lines @@
   }
   UMA_HISTOGRAM_ENUMERATION("DomainBoundCerts.Support", supported,
                             CHANNEL_ID_USAGE_MAX);
 }
 
 bool SSLClientSocketImpl::IsChannelIDEnabled() const {
   return ssl_config_.channel_id_enabled && channel_id_service_;
 }
 
 }  // namespace net