commit 98801af26b9bf8e543e93bd279439ba58977c1c1
author Jarno Lamsa <jarno.lamsa@arm.com> Tue Dec 17 15:57:41 2019 +0200
committer Jarno Lamsa <jarno.lamsa@arm.com> Thu Dec 19 09:02:02 2019 +0200
tree 1776a94e42648dcda690585b069cbb1f839fb2bc
parent b57d7fd568da2bd241ce0d08b8a88e82e4d81d94

Protect setting of hello_random flag

The handshake flag tells when the handshake hello.random
is set and can be used later to decide if we have the correct
keys.

library/ssl_srv.c

diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 8d14374..e349ed8 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -1223,8 +1223,14 @@
     mbedtls_platform_memcpy( ssl->session_negotiate->id, p, ssl->session_negotiate->id_len );
 
     p += sess_len;
+
+    ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_UNSET;
     memset( ssl->handshake->randbytes, 0, 64 );
     mbedtls_platform_memcpy( ssl->handshake->randbytes + 32 - chal_len, p, chal_len );
+    if( mbedtls_platform_memcmp( ssl->handshake->randbytes + 32 - chal_len, p, chal_len ) == 0 )
+    {
+        ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_SET;
+    }
 
     /*
      * Check for TLS_EMPTY_RENEGOTIATION_INFO_SCSV
@@ -1717,10 +1723,14 @@
     /*
      * Save client random (inc. Unix time)
      */
+    ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_UNSET;
     MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, random bytes", buf + 2, 32 );
 
     mbedtls_platform_memcpy( ssl->handshake->randbytes, buf + 2, 32 );
-
+    if( mbedtls_platform_memcmp( ssl->handshake->randbytes, buf + 2, 32 ) == 0 )
+    {
+        ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_SET;
+    }
     /*
      * Check the session ID length and save session ID
      */
@@ -2814,8 +2824,12 @@
     }
 
     p += 28;
-
+    ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_UNSET;
     mbedtls_platform_memcpy( ssl->handshake->randbytes + 32, buf + 6, 32 );
+    if( mbedtls_platform_memcmp( ssl->handshake->randbytes + 32, buf + 6, 32 ) == 0 )
+    {
+        ssl->handshake->hello_random_set = MBEDTLS_SSL_FI_FLAG_SET;
+    }
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, random bytes", buf + 6, 32 );