commit 1a7a17e5484b3f634c0341905f474ac148b9adfc
author Angus Gratton <angus@espressif.com> Wed Jun 20 15:43:50 2018 +1000
committer Simon Butcher <simon.butcher@arm.com> Fri Jul 20 23:09:29 2018 +0100
tree 3420fee6a73798dca11e542e1bed99c522a87849
parent 34817929ea8716ff212b71b5a59e2307b4696321

Check for invalid short Alert messages

(Short Change Cipher Spec & Handshake messages are already checked for.)

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index b7c8881..f1856e2 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4187,6 +4187,16 @@
 
     if( ssl->in_msgtype == MBEDTLS_SSL_MSG_ALERT )
     {
+        if( ssl->in_msglen != 2 )
+        {
+            /* Note: Standard allows for more than one 2 byte alert
+               to be packed in a single message, but Mbed TLS doesn't
+               currently support this. */
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid alert message, len: %d",
+                           ssl->in_msglen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
         MBEDTLS_SSL_DEBUG_MSG( 2, ( "got an alert message, type: [%d:%d]",
                        ssl->in_msg[0], ssl->in_msg[1] ) );