net: Precede each CBC encrypted application data record with an empty one.

net/third_party/nss/patches/cbcrandomiv.patch

Index: net/third_party/nss/patches/cbcrandomiv.patch
diff --git a/net/third_party/nss/patches/cbcrandomiv.patch b/net/third_party/nss/patches/cbcrandomiv.patch
new file mode 100644
index 0000000000000000000000000000000000000000..9f1b57a0bcc124adb5e01eab8c1991c857d761ce
--- /dev/null
+++ b/net/third_party/nss/patches/cbcrandomiv.patch
@@ -0,0 +1,73 @@
+commit 36840201a321147d9c33a944784ff56980aae5d8
+Author: Adam Langley <agl@chromium.org>
+Date:   Wed Jun 22 13:36:50 2011 -0400
+
+    cbcrandomiv.patch
+
+diff --git a/mozilla/security/nss/lib/ssl/ssl3con.c b/mozilla/security/nss/lib/ssl/ssl3con.c
+index 2cc1e05..eb7d63e 100644
+--- a/mozilla/security/nss/lib/ssl/ssl3con.c
++++ b/mozilla/security/nss/lib/ssl/ssl3con.c
+@@ -2229,7 +2229,7 @@ ssl3_SendRecord(   sslSocket *        ss,
+ 	return SECFailure;
+     }
+ 
+-    while (nIn > 0) {
++    do {
+ 	PRUint32  contentLen = PR_MIN(nIn, MAX_FRAGMENT_LENGTH);
+ 
+ 	if (wrBuf->space < contentLen + SSL3_BUFFER_FUDGE) {
+@@ -2306,7 +2306,7 @@ ssl3_SendRecord(   sslSocket *        ss,
+ 	    }
+ 	}
+ 	totalSent += contentLen;
+-    }
++    } while (nIn > 0);
+     return totalSent;
+ }
+ 
+@@ -2321,6 +2321,7 @@ ssl3_SendApplicationData(sslSocket *ss, const unsigned char *in,
+ {
+     PRInt32   totalSent	= 0;
+     PRInt32   discarded = 0;
++    PRBool    isBlockCipher;
+ 
+     PORT_Assert( ss->opt.noLocks || ssl_HaveXmitBufLock(ss) );
+     if (len < 0 || !in) {
+@@ -2345,6 +2346,28 @@ ssl3_SendApplicationData(sslSocket *ss, const unsigned char *in,
+ 	len--;
+ 	discarded = 1;
+     }
++
++    ssl_GetSpecReadLock(ss);
++    isBlockCipher = ss->ssl3.cwSpec->cipher_def->type == type_block;
++    ssl_ReleaseSpecReadLock(ss);
++
++    if (isBlockCipher && len > 0) {
++	// We assume that block ciphers are used in CBC mode and prepend an
++	// empty record. This effectively randomizes the IV in a backwards
++	// compatible way.
++	PRInt32 sent = ssl3_SendRecord(ss, content_application_data,
++				       in, 0 /* no payload */, flags);
++	if (sent < 0) {
++	    return SECFailure; /* error code set by ssl3_SendRecord */
++	}
++	if (ss->pendingBuf.len) {
++	    /* must be a non-blocking socket */
++	    PORT_Assert(!ssl_SocketIsBlocking(ss));
++	    PORT_Assert(ss->lastWriteBlocked);
++	    return SECFailure;
++	}
++    }
++
+     while (len > totalSent) {
+ 	PRInt32   sent, toSend;
+ 
+@@ -2377,6 +2400,7 @@ ssl3_SendApplicationData(sslSocket *ss, const unsigned char *in,
+ 	    break;	
+ 	}
+     }
++
+     if (ss->pendingBuf.len) {
+ 	/* Must be non-blocking. */
+ 	PORT_Assert(!ssl_SocketIsBlocking(ss));