Switch legacy cipher to constant-time invalid padding reporting
In internal `get_padding` functions, report whether the padding was invalid
through a separate output parameter, rather than the return code. Take
advantage of this to have `mbedtls_cipher_finish_padded()` be the easy path
that just passes the `invalid_padding` through. Make
`mbedtls_cipher_finish()` a wrapper around `mbedtls_cipher_finish_padded()`
that converts the invalid-padding output into an error code.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/cipher_invasive.h b/library/cipher_invasive.h
index 702f8f7..e82a0a7 100644
--- a/library/cipher_invasive.h
+++ b/library/cipher_invasive.h
@@ -20,7 +20,8 @@
MBEDTLS_STATIC_TESTABLE int mbedtls_get_pkcs_padding(unsigned char *input,
size_t input_len,
- size_t *data_len);
+ size_t *data_len,
+ size_t *invalid_padding);
#endif