Introduce MD handle type
As has been previously done for ciphersuites, this commit introduces
a zero-cost abstraction layer around the type
mbedtls_md_info const *
whose valid values represent implementations of message digest algorithms.
Access to a particular digest implementation can be requested by name or
digest ID through the API mbedtls_md_info_from_xxx(), which either returns
a valid implementation or NULL, representing failure.
This commit replaces such uses of `mbedtls_md_info const *` by an abstract
type `mbedtls_md_handle_t` whose valid values represent digest implementations,
and which has a designated invalid value MBEDTLS_MD_INVALID_HANDLE.
The purpose of this abstraction layer is to pave the way for builds which
support precisely one digest algorithm. In this case, mbedtls_md_handle_t
can be implemented as a two-valued type, with one value representing the
invalid handle, and the unique valid value representing the unique enabled
digest.
diff --git a/library/pk.c b/library/pk.c
index 161a135..93c5764 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -205,13 +205,16 @@
*/
static inline int pk_hashlen_helper( mbedtls_md_type_t md_alg, size_t *hash_len )
{
- const mbedtls_md_info_t *md_info;
+ mbedtls_md_handle_t md_info;
if( *hash_len != 0 )
return( 0 );
- if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )
+ if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) ==
+ MBEDTLS_MD_INVALID_HANDLE )
+ {
return( -1 );
+ }
*hash_len = mbedtls_md_get_size( md_info );
return( 0 );