linux-kernel - Re: [PATCH v2][RESEND] X.509: unpack RSA signatureValue field from BIT STRING

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Date:   Wed, 20 Jun 2018 14:24:54 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Tom Lendacky <thomas.lendacky@....com>,
        Gary Hook <gary.hook@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        james.morris@...rosoft.com, "Serge E. Hallyn" <serge@...lyn.com>,
        keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2][RESEND] X.509: unpack RSA signatureValue field from
 BIT STRING

On 02.06.2018 21:12, Maciej S. Szmigiero wrote:
> 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...
> 

A friendly ping here.

@AMD people:
Without this patch, in-kernel X.509 certificate verification is broken
on AMD CCP RSA implementation.

For example, loading wireless regulatory database gives the following
errors:
> [   21.310361] cfg80211: Problem loading in-kernel X.509 certificate (-22)
> [   21.351717] cfg80211: loaded regulatory.db is malformed or signature is missing/invalid

Kernel modules signature verification probably has similar problem, too.

That's why it would be nice if you could ack this patch, please.

Maciej