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.
All sample and test programs had a definition of mbedtls_param_failed.
This was necessary because we wanted to be able to build them in a
configuration with MBEDTLS_CHECK_PARAMS set but without a definition
of MBEDTLS_PARAM_FAILED. Now that we activate the sample definition of
MBEDTLS_PARAM_FAILED in config.h when testing with
MBEDTLS_CHECK_PARAMS set, this boilerplate code is no longer needed.
The previous prototype gave warnings are the strings produced by #cond and
__FILE__ are const, so we shouldn't implicitly cast them to non-const.
While at it modifying most example programs:
- include the header that has the function declaration, so that the definition
can be checked to match by the compiler
- fix whitespace
- make it work even if PLATFORM_C is not defined:
- CHECK_PARAMS is not documented as depending on PLATFORM_C and there is
no reason why it should
- so, remove the corresponding #if defined in each program...
- and add missing #defines for mbedtls_exit when needed
The result has been tested (make all test with -Werror) with the following
configurations:
- full with CHECK_PARAMS with PLATFORM_C
- full with CHECK_PARAMS without PLATFORM_C
- full without CHECK_PARAMS without PLATFORM_C
- full without CHECK_PARAMS with PLATFORM_C
Additionally, it has been manually tested that adding
mbedtls_aes_init( NULL );
near the normal call to mbedtls_aes_init() in programs/aes/aescrypt2.c has the
expected effect when running the program.
The sample programs require an additional handler function of
mbedtls_param_failed() to handle any failed parameter validation checks enabled
by the MBEDTLS_CHECK_PARAMS config.h option.
This commit replaces multiple `memset()` calls in the example
programs aes/aescrypt2.c and aes/crypt_and_hash.c by calls to
the reliable zeroization function `mbedtls_zeroize()`.
While not a security issue because the code is in the example
programs, it's bad practice and should be fixed.
The AES sample application programs/aes/crypt_and_hash could miss
zeroizing the stack-based key buffer in case of an error during
operation. This commit fixes this and also clears all command line
arguments (one of which might be the key) before exit.
* Fix crypt_and_hash to support decrypting GCM encrypted files
* Fix documentation in crypt_and_hash for the generic case
* Remove unused lastn from crypt_and_hash
lastn is not used with the cipher layer as it already provides padding
and understanding of length of the original data.
Note from future self: actually md_init_ctx will be re-introduced with the
same signature later, and a new function with the additional argument will be
added.
