Re: Need some clarification about CRYPTO_AHASH_ALG_BLOCK_ONLY

[Paul Louvel]

Hello,

I forgot to include the maintainers in the initial e-mail.

Additional link to the source code :
https://elixir.bootlin.com/linux/v7.0-rc1/source/crypto/ahash.c#L467

Thank you,
Paul.

On 3/20/26 10:42 AM, Paul Louvel wrote:
> Hello,
>
> I have stumbled across a flag defined in include/crypto/internal/hash.h : 
> CRYPTO_AHASH_ALG_BLOCK_ONLY.
> To get more information about what exact behavior this flag do, I read the 
> crypto_ahash_update function.
> From the looks of it, it seems that the API will call the tfm update if there 
> is enough bytes (and by enough I mean at least a block size), from the 
> internal buffer and the incoming ahash_request.
> In this case, I find the BLOCK_ONLY naming a bit of a misnomer, since it only 
> guarantee you than req->nbytes will be at least a block size.
> I initially though that the API would only give a request that are a multiple 
> of the block size.
>
> This flag, among others, are relatively recent.
> I think adding documentation about these flags would be a great idea.
>
> Regards,
> Paul.
--
Paul Louvel, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com