mbedtls/ChangeLog.d/check-return.txt

Bugfix
   * Failures of alternative implementations of AES or DES single-block
     functions enabled with MBEDTLS_AES_ENCRYPT_ALT, MBEDTLS_AES_DECRYPT_ALT,
     MBEDTLS_DES_CRYPT_ECB_ALT or MBEDTLS_DES3_CRYPT_ECB_ALT were ignored.
     This does not concern the implementation provided with Mbed TLS,
     where this function cannot fail, or full-module replacements with
     MBEDTLS_AES_ALT or MBEDTLS_DES_ALT. Reported by Armelle Duboc in #1092.

Features
   * Warn if errors from certain functions are ignored. This is currently
     supported on GCC-like compilers and on MSVC and can be configured through
     the macro MBEDTLS_CHECK_RETURN. The warnings are always enabled
     (where supported) for critical functions where ignoring the return
     value is almost always a bug. Enable the new configuration option
     MBEDTLS_CHECK_RETURN_WARNING to get warnings for other functions. This
     is currently implemented in the AES and DES modules, and will be extended
     to other modules in the future.
Catch failures of AES or DES operations Declare all AES and DES functions that return int as needing to have their result checked, and do check the result in our code. A DES or AES block operation can fail in alternative implementations of mbedtls_internal_aes_encrypt() (under MBEDTLS_AES_ENCRYPT_ALT), mbedtls_internal_aes_decrypt() (under MBEDTLS_AES_DECRYPT_ALT), mbedtls_des_crypt_ecb() (under MBEDTLS_DES_CRYPT_ECB_ALT), mbedtls_des3_crypt_ecb() (under MBEDTLS_DES3_CRYPT_ECB_ALT). A failure can happen if the accelerator peripheral is in a bad state. Several block modes were not catching the error. This commit does the following code changes, grouped together to avoid having an intermediate commit where the build fails: * Add MBEDTLS_CHECK_RETURN to all functions returning int in aes.h and des.h. * Fix all places where this causes a GCC warning, indicating that our code was not properly checking the result of an AES operation: * In library code: on failure, goto exit and return ret. * In pkey programs: goto exit. * In the benchmark program: exit (not ideal since there's no error message, but it's what the code currently does for failures). * In test code: TEST_ASSERT. * Changelog entry. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com> 2021-07-07 21:08:28 +02:00			`Bugfix`
			`* Failures of alternative implementations of AES or DES single-block`
			`functions enabled with MBEDTLS_AES_ENCRYPT_ALT, MBEDTLS_AES_DECRYPT_ALT,`
			`MBEDTLS_DES_CRYPT_ECB_ALT or MBEDTLS_DES3_CRYPT_ECB_ALT were ignored.`
			`This does not concern the implementation provided with Mbed TLS,`
			`where this function cannot fail, or full-module replacements with`
			`MBEDTLS_AES_ALT or MBEDTLS_DES_ALT. Reported by Armelle Duboc in #1092.`

New configuration option MBEDTLS_CHECK_RETURN_WARNING MBEDTLS_CHECK_RETURN_TYPICAL defaults off, but is enabled if MBEDTLS_CHECK_RETURN_WARNING is enabled at compile time. (MBEDTLS_CHECK_RETURN_CRITICAL is always enabled.) The default is off so that a plausible program that builds with one version of Mbed TLS in the default configuration will still build under the next version. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com> 2021-09-23 18:07:36 +02:00			`Features`
			`* Warn if errors from certain functions are ignored. This is currently`
			`supported on GCC-like compilers and on MSVC and can be configured through`
			`the macro MBEDTLS_CHECK_RETURN. The warnings are always enabled`
			`(where supported) for critical functions where ignoring the return`
			`value is almost always a bug. Enable the new configuration option`
			`MBEDTLS_CHECK_RETURN_WARNING to get warnings for other functions. This`
			`is currently implemented in the AES and DES modules, and will be extended`
			`to other modules in the future.`