From: Adam Langley <agl@golang.org>
Date: Fri, 21 Sep 2012 19:54:46 +0000 (+1000)
Subject: [release-branch.go1] crypto/tls: return better error message in the case of an SSLv2... 
X-Git-Tag: go1.0.3~73
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=a3ab361b9cd91d0e827d0fb76fd4f020bd8d2c20;p=gostls13.git

[release-branch.go1] crypto/tls: return better error message in the case of an SSLv2 handshake.

««« backport 8048fe8f6f4b
crypto/tls: return better error message in the case of an SSLv2 handshake.

Update #3930
Return a better error message in this situation.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6474055

»»»
---

diff --git a/src/pkg/crypto/tls/conn.go b/src/pkg/crypto/tls/conn.go
index 2a5115dc6a..455910af41 100644
--- a/src/pkg/crypto/tls/conn.go
+++ b/src/pkg/crypto/tls/conn.go
@@ -487,6 +487,16 @@ Again:
 		return err
 	}
 	typ := recordType(b.data[0])
+
+	// No valid TLS record has a type of 0x80, however SSLv2 handshakes
+	// start with a uint16 length where the MSB is set and the first record
+	// is always < 256 bytes long. Therefore typ == 0x80 strongly suggests
+	// an SSLv2 client.
+	if want == recordTypeHandshake && typ == 0x80 {
+		c.sendAlert(alertProtocolVersion)
+		return errors.New("tls: unsupported SSLv2 handshake received")
+	}
+
 	vers := uint16(b.data[1])<<8 | uint16(b.data[2])
 	n := int(b.data[3])<<8 | int(b.data[4])
 	if c.haveVers && vers != c.vers {