From: Anthony Martin <ality@pbrane.org>
Date: Tue, 4 Feb 2014 15:51:37 +0000 (-0500)
Subject: crypto/tls: do not send the current time in hello messages
X-Git-Tag: go1.3beta1~813
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=c2d02b3b9fd6847535ac18b24582a8bb98a3eb30;p=gostls13.git

crypto/tls: do not send the current time in hello messages

This reduces the ability to fingerprint TLS connections.

The impeteus for this change was a recent change to OpenSSL
by Nick Mathewson:

http://git.openssl.org/gitweb/?p=openssl.git;a=commit;h=2016265dfb

LGTM=agl
R=agl
CC=golang-codereviews
https://golang.org/cl/57230043
---

diff --git a/src/pkg/crypto/tls/handshake_client.go b/src/pkg/crypto/tls/handshake_client.go
index 49ff0d768f..dbbccfee46 100644
--- a/src/pkg/crypto/tls/handshake_client.go
+++ b/src/pkg/crypto/tls/handshake_client.go
@@ -63,12 +63,7 @@ NextCipherSuite:
 		}
 	}
 
-	t := uint32(c.config.time().Unix())
-	hello.random[0] = byte(t >> 24)
-	hello.random[1] = byte(t >> 16)
-	hello.random[2] = byte(t >> 8)
-	hello.random[3] = byte(t)
-	_, err := io.ReadFull(c.config.rand(), hello.random[4:])
+	_, err := io.ReadFull(c.config.rand(), hello.random)
 	if err != nil {
 		c.sendAlert(alertInternalError)
 		return errors.New("tls: short read from Rand: " + err.Error())
diff --git a/src/pkg/crypto/tls/handshake_server.go b/src/pkg/crypto/tls/handshake_server.go
index ceb032a805..e441ccbcce 100644
--- a/src/pkg/crypto/tls/handshake_server.go
+++ b/src/pkg/crypto/tls/handshake_server.go
@@ -146,17 +146,12 @@ Curves:
 	}
 
 	hs.hello.vers = c.vers
-	t := uint32(config.time().Unix())
 	hs.hello.random = make([]byte, 32)
-	hs.hello.random[0] = byte(t >> 24)
-	hs.hello.random[1] = byte(t >> 16)
-	hs.hello.random[2] = byte(t >> 8)
-	hs.hello.random[3] = byte(t)
-	hs.hello.secureRenegotiation = hs.clientHello.secureRenegotiation
-	_, err = io.ReadFull(config.rand(), hs.hello.random[4:])
+	_, err = io.ReadFull(config.rand(), hs.hello.random)
 	if err != nil {
 		return false, c.sendAlert(alertInternalError)
 	}
+	hs.hello.secureRenegotiation = hs.clientHello.secureRenegotiation
 	hs.hello.compressionMethod = compressionNone
 	if len(hs.clientHello.serverName) > 0 {
 		c.serverName = hs.clientHello.serverName