Add macro for error code addition
Adds a macro (`MBEDTLS_ERR_ADD`) to add error codes together and check that the
result will not be corrupted. This additional check is only enabled during
testing when `MBEDTLS_TEST_HOOKS` is defined.
Also includes a reference usage example in `rsa.c` where two high-level error
codes could be incorrectly added together under the right conditions. This now
ensures that when this error occurs during testing it will be correctly
reported.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/library/rsa.c b/library/rsa.c
index fea76bf..f4bec46 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1085,7 +1085,7 @@
mbedtls_mpi_free( &I );
if( ret != 0 && ret >= -0x007f )
- return( MBEDTLS_ERR_RSA_PRIVATE_FAILED + ret );
+ return( MBEDTLS_ERR_ADD( MBEDTLS_ERR_RSA_PRIVATE_FAILED, ret ) );
return( ret );
}