Implement the encrypt-then-MAC TLS extension.

net/third_party/nss/ssl/ssl3ext.c

Index: net/third_party/nss/ssl/ssl3ext.c
===================================================================
--- net/third_party/nss/ssl/ssl3ext.c	(revision 252347)
+++ net/third_party/nss/ssl/ssl3ext.c	(working copy)
@@ -87,6 +87,12 @@
 static SECStatus ssl3_ClientHandleSignedCertTimestampXtn(sslSocket *ss,
 							 PRUint16 ex_type,
 							 SECItem *data);
+static PRInt32 ssl3_ClientSendEncryptThenMACXtn(sslSocket *ss,
+						PRBool append,
+						PRUint32 maxBytes);
+static SECStatus ssl3_ClientHandleEncryptThenMACXtn(sslSocket *ss,
+						    PRUint16 ex_type,
+						    SECItem *data);
 
 /*
  * Write bytes.  Using this function means the SECItem structure
@@ -267,6 +273,7 @@
     { ssl_cert_status_xtn,        &ssl3_ClientHandleStatusRequestXtn },
     { ssl_signed_certificate_timestamp_xtn,
       &ssl3_ClientHandleSignedCertTimestampXtn },
+    { ssl_encrypt_then_mac_xtn,   &ssl3_ClientHandleEncryptThenMACXtn },
     { -1, NULL }
 };
 
@@ -297,7 +304,8 @@
     { ssl_cert_status_xtn,        &ssl3_ClientSendStatusRequestXtn },
     { ssl_signature_algorithms_xtn, &ssl3_ClientSendSigAlgsXtn },
     { ssl_signed_certificate_timestamp_xtn,
-      &ssl3_ClientSendSignedCertTimestampXtn }
+      &ssl3_ClientSendSignedCertTimestampXtn },
+    { ssl_encrypt_then_mac_xtn, &ssl3_ClientSendEncryptThenMACXtn }
     /* any extra entries will appear as { 0, NULL }    */
 };
 
@@ -2451,3 +2459,50 @@
     ss->xtnData.negotiated[ss->xtnData.numNegotiated++] = ex_type;
     return SECSuccess;
 }
+
+static PRInt32
+ssl3_ClientSendEncryptThenMACXtn(sslSocket *ss, PRBool append,
+                                 PRUint32 maxBytes)
+{
+    PRInt32 extension_length = 2 /* extension_type */ +
+            2 /* length(extension_data) */;
+
+    /* Only send the extension if processing is enabled. */
+    if (!ss->opt.enableEncryptThenMAC)
+        return 0;
+
+    if (append && maxBytes >= extension_length) {
+        SECStatus rv;
+        /* extension_type */
+        rv = ssl3_AppendHandshakeNumber(ss,
+                                        ssl_encrypt_then_mac_xtn,
+                                        2);
+        if (rv != SECSuccess)
+            goto loser;
+        /* zero length */
+        rv = ssl3_AppendHandshakeNumber(ss, 0, 2);
+        if (rv != SECSuccess)
+            goto loser;
+        ss->xtnData.advertised[ss->xtnData.numAdvertised++] =
+                ssl_encrypt_then_mac_xtn;
+    } else if (maxBytes < extension_length) {
+        PORT_Assert(0);
+        return 0;
+    }
+
+    return extension_length;
+loser:
+    return -1;
+}
+
+static SECStatus
+ssl3_ClientHandleEncryptThenMACXtn(sslSocket *ss, PRUint16 ex_type,
+                                   SECItem *data)
+{
+    /* The echoed extension must be empty. */
+    if (data->len != 0)
+       return SECFailure;
+    /* Keep track of negotiated extensions. */
+    ss->xtnData.negotiated[ss->xtnData.numNegotiated++] = ex_type;
+    return SECSuccess;
+}