Fix uninitialised memory access in constant time functions
Fix an issue reported by Coverity whereby some constant time functions
called from the ssl decrypt code could potentially access uninitialised
memory.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/library/constant_time.c b/library/constant_time.c
index a6451bb..0b409b3 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -514,6 +514,12 @@
PSA_CHK( psa_hash_update( &operation, add_data, add_data_len ) );
PSA_CHK( psa_hash_update( &operation, data, min_data_len ) );
+ /* Fill the hash buffer in advance with something that is
+ * not a valid hash (barring an attack on the hash and
+ * deliberately-crafted input), in case the caller doesn't
+ * check the return status properly. */
+ memset( output, '!', hash_size );
+
/* For each possible length, compute the hash up to that point */
for( offset = min_data_len; offset <= max_data_len; offset++ )
{
@@ -609,6 +615,12 @@
MD_CHK( mbedtls_md_update( ctx, add_data, add_data_len ) );
MD_CHK( mbedtls_md_update( ctx, data, min_data_len ) );
+ /* Fill the hash buffer in advance with something that is
+ * not a valid hash (barring an attack on the hash and
+ * deliberately-crafted input), in case the caller doesn't
+ * check the return status properly. */
+ memset( output, '!', hash_size );
+
/* For each possible length, compute the hash up to that point */
for( offset = min_data_len; offset <= max_data_len; offset++ )
{