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MD: Use no-op for context SHA-256 init() and free()

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When MBEDTLS_MD_SINGLE_HASH is set, the underlying digest's
context is embedded into mbedtls_md_context_t, which is
zeroized before the underlying digest's init() function
is called. For those digests where initialization is
zeroization, the init() call can therefore be omitted.

Similarly, when free()-ing an mbedtls_md_context_t, the
entire context is zeroized in the end, hence if the
underlying digest's free() function is zeroization,
it can be omitted.
This commit is contained in:
Hanno Becker 2019-09-05 13:02:57 +01:00
parent 64b0623cbb
commit 94f48e0052
1 changed files with 19 additions and 0 deletions
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19
include/mbedtls/md_internal.h
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@ -79,9 +79,21 @@ extern "C" {
//#define MBEDTLS_MD_INFO_SHA256
/* SHA-256 */
static inline void mbedtls_md_sha256_init_free_dummy( void* ctx )
{
/* Zero-initialization can be skipped. */
((void) ctx);
}
#define MBEDTLS_MD_INFO_SHA256_TYPE MBEDTLS_MD_SHA256
#define MBEDTLS_MD_INFO_SHA256_CTX_TYPE mbedtls_sha256_context
#if defined(MBEDTLS_MD_SINGLE_HASH)
/* mbedtls_md_sha256_init() only zeroizes, which is redundant
* because mbedtls_md_context is zeroized in mbedtls_md_init(),
* and the mbedtls_sha256_context is embedded in mbedtls_md_context_t. */
#define MBEDTLS_MD_INFO_SHA256_INIT_FUNC mbedtls_md_sha256_init_free_dummy
#else
#define MBEDTLS_MD_INFO_SHA256_INIT_FUNC mbedtls_sha256_init
#endif /* MBEDTLS_MD_SINGLE_HASH */
#define MBEDTLS_MD_INFO_SHA256_NAME "SHA256"
#define MBEDTLS_MD_INFO_SHA256_SIZE 32
#define MBEDTLS_MD_INFO_SHA256_BLOCKSIZE 64
@ -90,7 +102,14 @@ extern "C" {
#define MBEDTLS_MD_INFO_SHA256_FINISH_FUNC mbedtls_sha224_finish_wrap
#define MBEDTLS_MD_INFO_SHA256_DIGEST_FUNC mbedtls_sha256_wrap
#define MBEDTLS_MD_INFO_SHA256_ALLOC_FUNC mbedtls_sha224_ctx_alloc
#if defined(MBEDTLS_MD_SINGLE_HASH)
/* mbedtls_md_sha256_free() only zeroizes, which is redundant
* because mbedtls_md_context is zeroized in mbedtls_md_init(),
* and the mbedtls_sha256_context is embedded in mbedtls_md_context_t. */
#define MBEDTLS_MD_INFO_SHA256_FREE_FUNC mbedtls_md_sha256_init_free_dummy
#else
#define MBEDTLS_MD_INFO_SHA256_FREE_FUNC mbedtls_sha224_ctx_free
#endif /* MBEDTLS_MD_SINGLE_HASH */
#define MBEDTLS_MD_INFO_SHA256_CLONE_FUNC mbedtls_sha224_clone_wrap
#define MBEDTLS_MD_INFO_SHA256_PROCESS_FUNC mbedtls_sha224_process_wrap