commit 84bde419e134a318becb61537459d7365af7f4bd
author Andrzej Kurek <andrzej.kurek@arm.com> Mon Jul 06 15:27:34 2020 -0400
committer Andrzej Kurek <andrzej.kurek@arm.com> Mon Jul 06 15:27:34 2020 -0400
tree 2b887ea4df13526366334e6ba88266ffd19b3ff9
parent 74f7d0f03de292474ed16500575aee45758fa491

Add FI countermeasures to the ssl module

This commit adds mainly buffer pointer and length duplication and checks,
but also some hamming distance and return values checking improvements.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>

library/ssl_cli.c

diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 24c73b5..5b47c0a 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -3587,7 +3587,10 @@
 {
     int ret;
     unsigned char *p, *end;
+    volatile unsigned char *buf_dup = buf;
+    volatile size_t buflen_dup = buflen;
     size_t n;
+
     mbedtls_ssl_ciphersuite_handle_t ciphersuite_info =
         mbedtls_ssl_handshake_get_ciphersuite( ssl->handshake );
 
@@ -3870,7 +3873,12 @@
     }
 
     *olen = p - buf;
-    return( 0 );
+    /* Secure against buffer substitution */
+    if( buf_dup == buf && buflen_dup == buflen )
+    {
+       return( 0 );
+    }
+    return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
 }
 
 static int ssl_out_client_key_exchange_postprocess( mbedtls_ssl_context *ssl )