Re: [PATCH v3] crypt32: Implement CNG_RSA_PUBLIC_KEY_BLOB encoding/decoding

[Hans Leidekker]

On Thu, 2021-07-08 at 14:25 +0200, Hans Leidekker wrote:
> > -
> >            /* CNG_RSA_PUBLIC_KEY_BLOB always stores the exponent and modulus
> > -
> >             * in big-endian format, so we need to convert from the native
> > -
> >             * endianness
> > -
> >             */
> > -
> >            CRYPT_memcpy_be((BYTE *)pvStructInfo + sizeof(BCRYPT_RSAKEY_BLOB),
> > -
> >             (BYTE *)&decodedKey->pubexp, sizeof(DWORD));
> > -
> >            CRYPT_memcpy_be((BYTE *)pvStructInfo + sizeof(BCRYPT_RSAKEY_BLOB) +
> > -
> >             sizeof(DWORD), decodedKey->modulus.pbData,
> > -
> >             decodedKey->modulus.cbData);
>
> Exponent and modulus are handled as a byte arrays so native endianess
> is not relevant there. They should be reversed unconditionally here as
> well as in the encoder and the tests.

Though in the test you use a DWORD for the exponent, so you would need
to reverse that depending on host endianness, or you could store it as
a byte array.