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/hkdf.c b/library/hkdf.c
index 82d8a42..d64dc4d 100644
--- a/library/hkdf.c
+++ b/library/hkdf.c
@@ -30,7 +30,7 @@
#include "mbedtls/hkdf.h"
#include "mbedtls/platform_util.h"
-int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt,
+int mbedtls_hkdf( mbedtls_md_handle_t md, const unsigned char *salt,
size_t salt_len, const unsigned char *ikm, size_t ikm_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len )
@@ -51,7 +51,7 @@
return( ret );
}
-int mbedtls_hkdf_extract( const mbedtls_md_info_t *md,
+int mbedtls_hkdf_extract( mbedtls_md_handle_t md,
const unsigned char *salt, size_t salt_len,
const unsigned char *ikm, size_t ikm_len,
unsigned char *prk )
@@ -81,7 +81,7 @@
return( mbedtls_md_hmac( md, salt, salt_len, ikm, ikm_len, prk ) );
}
-int mbedtls_hkdf_expand( const mbedtls_md_info_t *md, const unsigned char *prk,
+int mbedtls_hkdf_expand( mbedtls_md_handle_t md, const unsigned char *prk,
size_t prk_len, const unsigned char *info,
size_t info_len, unsigned char *okm, size_t okm_len )
{