Dear Mbed TLS contributors, We are using mbedtls v4 for X.509 certificate verification on a 32 bit microcontroller. The device has an RTC chip and we use its time for mbedtls by defining MBEDTLS_PLATFORM_TIME_ALT. This is working so far.
The compiler provides <time.h>, with time_t being a signed 32 bit type. I would like to stop mbedtls from using the date and time functions of <time.h> and change mbedtls_time_t to unsigned 32 bit to avoid the year 2038 problem (when signed 32 bit time_t will overflow). To do this, I defined #define MBEDTLS_PLATFORM_TIME_TYPE_MACRO unsigned long
I also changed the custom time function (MBEDTLS_PLATFORM_TIME_ALT) to return unsigned values and I defined MBEDTLS_PLATFORM_GMTIME_R_ALT and provided a custom mbedtls_platform_gmtime_r() that accepts unsigned values.
When I build mbedtls with these settings, I get an error from tf_psa_crypto_check_config.h:
#if defined(MBEDTLS_PLATFORM_TIME_TYPE_MACRO) &&\ ( defined(MBEDTLS_PLATFORM_STD_TIME) ||\ defined(MBEDTLS_PLATFORM_TIME_ALT) ) #error "MBEDTLS_PLATFORM_TIME_TYPE_MACRO and MBEDTLS_PLATFORM_STD_TIME/MBEDTLS_PLATFORM_TIME_ALT cannot be defined simultaneously" #endif
I wonder if this check is actually necessary or maybe a mistake? Actually, I expected the opposite, i.e.
#if defined(MBEDTLS_PLATFORM_TIME_TYPE_MACRO) &&\ !( defined(MBEDTLS_PLATFORM_STD_TIME) ||\ defined(MBEDTLS_PLATFORM_TIME_ALT) ) #error "Must provide alternate time() function compatible with type defined by MBEDTLS_PLATFORM_TIME_TYPE_MACRO" #endif
Could somebody please explain why MBEDTLS_PLATFORM_TIME_TYPE_MACRO can't be used with MBEDTLS_PLATFORM_TIME_ALT? Can/Should I comment out the #error? I tried that and the library compiles without errors, and the software using the library also compiles without errors, but I have not yet checked, if it actually works.
Best regards, Ralf Huber KION Supply Chain Solutions
Linde Material Handling GmbH, Sitz der Gesellschaft: Aschaffenburg, Registergericht: Aschaffenburg HRB9963, Ust-IdNr. DE814809128, Gesch?ftsf?hrung: Andreas Krinninger (Vorsitzender), Dr. Karoline Jung-Senssfelder, Ulrike Just, Dr. Frank Schepp, Vorsitzende des Aufsichtsrats: Valeria Gargiulo
Hello,
I agree that this looks like a mistake. The various platform interfaces are subtly different, and I suspect that this was inspired by a similar check for a different interface that doesn't apply here. This is not tested (I think we have no tests for custom platform types).
Can you please submit a patch?
mbed-tls@lists.trustedfirmware.org
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Gilles Peskine -
Huber, Ralf