Send only one byte of data in the first CBC encrypted aplication data

net/third_party/nss/patches/cbcrandomiv.patch

Index: net/third_party/nss/patches/cbcrandomiv.patch
===================================================================
--- net/third_party/nss/patches/cbcrandomiv.patch	(revision 0)
+++ net/third_party/nss/patches/cbcrandomiv.patch	(revision 0)
@@ -0,0 +1,59 @@
+Index: mozilla/security/nss/lib/ssl/ssl3con.c
+===================================================================
+RCS file: /cvsroot/mozilla/security/nss/lib/ssl/ssl3con.c,v
+retrieving revision 1.142.2.5
+diff -u -p -u -r1.142.2.5 ssl3con.c
+--- mozilla/security/nss/lib/ssl/ssl3con.c	25 Jan 2011 01:49:22 -0000	1.142.2.5
++++ mozilla/security/nss/lib/ssl/ssl3con.c	11 Aug 2011 02:15:58 -0000
+@@ -2315,6 +2315,8 @@ ssl3_SendApplicationData(sslSocket *ss, 
+ {
+     PRInt32   totalSent	= 0;
+     PRInt32   discarded = 0;
++    PRBool    isBlockCipher;
++    int       recordIndex;
+ 
+     PORT_Assert( ss->opt.noLocks || ssl_HaveXmitBufLock(ss) );
+     if (len < 0 || !in) {
+@@ -2339,7 +2341,12 @@ ssl3_SendApplicationData(sslSocket *ss, 
+ 	len--;
+ 	discarded = 1;
+     }
+-    while (len > totalSent) {
++
++    ssl_GetSpecReadLock(ss);
++    isBlockCipher = ss->ssl3.cwSpec->cipher_def->type == type_block;
++    ssl_ReleaseSpecReadLock(ss);
++
++    for (recordIndex = 0; len > totalSent; recordIndex++) {
+ 	PRInt32   sent, toSend;
+ 
+ 	if (totalSent > 0) {
+@@ -2354,6 +2361,28 @@ ssl3_SendApplicationData(sslSocket *ss, 
+ 	    ssl_GetXmitBufLock(ss);
+ 	}
+ 	toSend = PR_MIN(len - totalSent, MAX_FRAGMENT_LENGTH);
++	if (isBlockCipher &&
++	    ss->ssl3.cwSpec->version <= SSL_LIBRARY_VERSION_3_1_TLS) {
++	    /*
++	     * We assume that block ciphers are used in CBC mode and send
++	     * only one byte in the first record.  This effectively
++	     * randomizes the IV in a backward compatible way.
++	     *
++	     * We get back to the MAX_FRAGMENT_LENGTH record boundary in
++	     * the second record.  So for a large amount of data, we send
++	     *     1
++	     *     MAX_FRAGMENT_LENGTH - 1
++	     *     MAX_FRAGMENT_LENGTH
++	     *     MAX_FRAGMENT_LENGTH
++	     *     ...
++	     */
++	    if (recordIndex == 0) {
++		toSend = 1;
++	    } else if (recordIndex == 1 &&
++		       len - totalSent > MAX_FRAGMENT_LENGTH) {
++		toSend--;
++	    }
++	}
+ 	sent = ssl3_SendRecord(ss, content_application_data, 
+ 	                       in + totalSent, toSend, flags);
+ 	if (sent < 0) {