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>
This commit is contained in:
Gilles Peskine 2021-09-23 18:07:36 +02:00
parent e568ebade1
commit 8472a10594
3 changed files with 38 additions and 5 deletions

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@ -6,7 +6,12 @@ Bugfix
where this function cannot fail, or full-module replacements with
MBEDTLS_AES_ALT or MBEDTLS_DES_ALT. Reported by Armelle Duboc in #1092.
Changes
* Warn if errors from AES or DES functions are ignored. This is currently
supported on GCC-like compilers and on MSVC and can be configured by
setting MBEDTLS_CHECK_RETURN in config.h.
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.

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@ -616,6 +616,29 @@
*/
//#define MBEDTLS_CAMELLIA_SMALL_MEMORY
/**
* \def MBEDTLS_CHECK_RETURN_WARNING
*
* If this macro is defined, emit a compile-time warning if application code
* calls a function without checking its return value, but the return value
* should generally be checked in portable applications.
*
* This is only supported on platforms where #MBEDTLS_CHECK_RETURN is
* implemented. Otherwise this option has no effect.
*
* Uncomment to get warnings on using fallible functions without checking
* their return value.
*
* \note This feature is a work in progress.
* Warnings will be added to more functions in the future.
*
* \note A few functions are considered critical, and ignoring the return
* value of these functions will trigger a warning even if this
* macro is not defined. To completely disable return value check
* warnings, define #MBEDTLS_CHECK_RETURN with an empty expansion.
*/
//#define MBEDTLS_CHECK_RETURN_WARNING
/**
* \def MBEDTLS_CIPHER_MODE_CBC
*

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@ -173,7 +173,8 @@ MBEDTLS_DEPRECATED typedef int mbedtls_deprecated_numeric_constant_t;
* This macro appearing at the beginning of the declaration of a function
* indicates that its return value should be generally be checked in portable
* applications. Omitting the check will result in a compile-time warning if
* #MBEDTLS_CHECK_RETURN is implemented for the compiler in use.
* #MBEDTLS_CHECK_RETURN is implemented for the compiler in use and
* #MBEDTLS_CHECK_RETURN_WARNING is enabled in the compile-time configuration.
*
* \note The use of this macro is a work in progress.
* This macro will be added to more functions in the future.
@ -181,7 +182,11 @@ MBEDTLS_DEPRECATED typedef int mbedtls_deprecated_numeric_constant_t;
* an error code (as \c int in the \c mbedtls_xxx API or
* as ::psa_status_t in the \c psa_xxx API).
*/
#if defined(MBEDTLS_CHECK_RETURN_WARNING)
#define MBEDTLS_CHECK_RETURN_TYPICAL MBEDTLS_CHECK_RETURN
#else
#define MBEDTLS_CHECK_RETURN_TYPICAL
#endif
/** Benign-failure function
*