[PATCH libgcrypt] Disable CPU speculation-related misfeatures

[Falko Strenzke]

Hi Guido,

is it possible to provide references to publications for the problem 
that you aim to solve?

Best regards,
Falko

Am 26.05.25 um 19:11 schrieb Guido Trentalancia via Gcrypt-devel:
> The vulnerabilities being tackled by the patch proposed here are
> hardware vulnerabilities that exist in the CPU.
>
> They were introduced with branch-prediction and other speculative-
> execution CPU optimizations.
>
> Because, once exploited, they materialize in Information Disclosure
> (data leaks), cryptographic software is the most affected class of
> software, because cryptographic keys or encrypted data can be leaked.
>
> Unfortunately not all of such hardware vulnerabilities can be tackled
> by a CPU microcode update, some of them need to be tackled in software:
> this is what this patch aims to do (software-based mitigation of
> hardware vulnerabilities).
>
> An equivalent patch has been already proposed for the gnupg application
> and another one might be proposed for the gnutls library.
>
> In fact, only tackling libgcrypt is not enough, because cryptographic
> applications such as gnupg also handle the cryptographic keys (e.g.
> passphrases) and the sensitive data to be encrypted: these are then
> passed to the libgcrypt cryptographic functions for actual encryption
> and decryption.
>
> The "pros" of this patch are that it avoids the risk of leaking
> cryptographic keys or decrypted data on CPUs that are affected by those
> vulnerabilities.
>
> The "cons" of this patch are decreased execution speed: this is not
> normally noticeable to the user.
>
> I hope this helps.
>
> On Mon, 26/05/2025 at 16.53 +0200, Werner Koch wrote:
>> On Sun, 25 May 2025 17:25, Guido Trentalancia said:
>>> Disable CPU speculation-related misfeatures which are in
>>> fact vulnerabilities causing data leaks:
>> Please see my comments on gnupg-devel.
>>
>>
>> Shalom-Salam,
>>
>>     Werner
>>
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