commit 1ac22cc4e4128c03c402f9f5adb683aaf37a6e74
author dschinazi <dschinazi@google.com> Tue Jun 25 11:47:50 2019 -0700
committer Copybara-Service <copybara-worker@google.com> Tue Jun 25 11:49:26 2019 -0700
tree 1ce79208c04059be50c60c623b83958df963a455
parent 198aa9940e16cacb39d2fa6c02064c1dd73e0d9d

Apply GREASE to QUIC Version Negotiation packets

This prevents client implementations from breaking when they observe unknown versions.

This also ensures that the produced packet will always be long enough to allow QUIC proxy munging.

gfe-relnote: minor change to packet format of Version Negotiation packets, protected by --gfe2_reloadable_flag_quic_disable_version_negotiation_grease_randomness
PiperOrigin-RevId: 255015606
Change-Id: I8070d543a765e914a2cdc07fd941fa5e1b359c14

quic/core/quic_versions.cc

diff --git a/quic/core/quic_versions.cc b/quic/core/quic_versions.cc
index 7e828a7..afaae66 100644
--- a/quic/core/quic_versions.cc
+++ b/quic/core/quic_versions.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "net/third_party/quiche/src/quic/core/crypto/quic_random.h"
 #include "net/third_party/quiche/src/quic/core/quic_tag.h"
 #include "net/third_party/quiche/src/quic/core/quic_types.h"
 #include "net/third_party/quiche/src/quic/platform/api/quic_arraysize.h"
@@ -25,6 +26,22 @@
   return MakeQuicTag(d, c, b, a);
 }
 
+QuicVersionLabel CreateRandomVersionLabelForNegotiation() {
+  if (!GetQuicReloadableFlag(quic_version_negotiation_grease)) {
+    return MakeVersionLabel(0xda, 0x5a, 0x3a, 0x3a);
+  }
+  QUIC_RELOADABLE_FLAG_COUNT_N(quic_version_negotiation_grease, 2, 2);
+  QuicVersionLabel result;
+  if (!GetQuicFlag(FLAGS_quic_disable_version_negotiation_grease_randomness)) {
+    QuicRandom::GetInstance()->RandBytes(&result, sizeof(result));
+  } else {
+    result = MakeVersionLabel(0xd1, 0x57, 0x38, 0x3f);
+  }
+  result &= 0xf0f0f0f0;
+  result |= 0x0a0a0a0a;
+  return result;
+}
+
 }  // namespace
 
 ParsedQuicVersion::ParsedQuicVersion(HandshakeProtocol handshake_protocol,
@@ -112,7 +129,7 @@
       }
       return MakeVersionLabel(proto, '0', '9', '9');
     case QUIC_VERSION_RESERVED_FOR_NEGOTIATION:
-      return MakeVersionLabel(0xda, 0x5a, 0x3a, 0x3a);
+      return CreateRandomVersionLabelForNegotiation();
     default:
       // This is a bug because we should never attempt to convert an invalid
       // QuicTransportVersion to be written to the wire.