net: don't always add TLS padding.

net/third_party/nss/ssl/ssl3ext.c

 /*
  * SSL3 Protocol
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* TLS extension code moved here from ssl3ecc.c */
 
 #include "nssrenam.h"
@@ skipping 2324 matching lines @@
 }
 
 unsigned int
 ssl3_CalculatePaddingExtensionLength(unsigned int clientHelloLength)
 {
     unsigned int recordLength = 1 /* handshake message type */ +
                                 3 /* handshake message length */ +
                                 clientHelloLength;
     unsigned int extensionLength;
 
-    /* This condition should be:
-     *   if (recordLength < 256 || recordLength >= 512) {
-     * It has been changed, temporarily, to test whether 512 byte ClientHellos
-     * are a compatibility problem. */
-    if (recordLength >= 512) {
+    if (recordLength < 256 || recordLength >= 512) {
         return 0;
     }
 
     extensionLength = 512 - recordLength;
     /* Extensions take at least four bytes to encode. */
     if (extensionLength < 4) {
         extensionLength = 4;
     }
 
     return extensionLength;
 }
 
 /* ssl3_AppendPaddingExtension possibly adds an extension which ensures that a
  * ClientHello record is either < 256 bytes or is >= 512 bytes. This ensures
  * that we don't trigger bugs in F5 products. */
 PRInt32
 ssl3_AppendPaddingExtension(sslSocket *ss, unsigned int extensionLen,
                             PRUint32 maxBytes)
 {
     unsigned int paddingLen = extensionLen - 4;
-    static unsigned char padding[512];
+    static unsigned char padding[256];
 
     if (extensionLen == 0) {
         return 0;
     }
 
     if (extensionLen < 4 ||
         extensionLen > maxBytes ||
         paddingLen > sizeof(padding)) {
         PORT_Assert(0);
         return -1;
@@ skipping 63 matching lines @@
 
     if (!data->len) {
         /* Empty extension data: RFC 6962 mandates non-empty contents. */
         return SECFailure;
     }
     *scts = *data;
     /* Keep track of negotiated extensions. */
     ss->xtnData.negotiated[ss->xtnData.numNegotiated++] = ex_type;
     return SECSuccess;
 }