Re: [PATCH v2][RESEND] X.509: unpack RSA signatureValue field from BIT STRING
From: Maciej S. Szmigiero
Date: Sat Jun 02 2018 - 15:12:23 EST
On 19.05.2018 14:23, Maciej S. Szmigiero wrote:
> The signatureValue field of a X.509 certificate is encoded as a BIT STRING.
> For RSA signatures this BIT STRING is of so-called primitive subtype, which
> contains a u8 prefix indicating a count of unused bits in the encoding.
>
> We have to strip this prefix from signature data, just as we already do for
> key data in x509_extract_key_data() function.
>
> This wasn't noticed earlier because this prefix byte is zero for RSA key
> sizes divisible by 8. Since BIT STRING is a big-endian encoding adding zero
> prefixes has no bearing on its value.
>
> The signature length, however was incorrect, which is a problem for RSA
> implementations that need it to be exactly correct (like AMD CCP).
Any progress here?
This simple patch has already been submitted 3 times in last 3+ months...