Re: feature request for coreutils: b2sum

[Samuel Neves]

Hi,

This is indeed a bug, but I'm not too fond of that fix, as it slightly alters 
the semantics of the final() function. `outlen` goes from being the size of the 
output buffer---which may be larger than the hash size---to being exactly, and 
prescriptively, the hash output size.

The bug's root cause is the fact that `blake2x_init_param` sets the output size 
`S->outlen` from the `digest_length` parameter, but in this case the output 
length is meant to be `BLAKE2X_OUT_BYTES`, i.e., the `inner_length` field in 
the parameter block.

https://github.com/BLAKE2/BLAKE2/blob/master/ref/blake2b-ref.c#L92

But the `blake2xp_init_leaf` misses this, and the digest length is used there 
instead:

https://github.com/BLAKE2/BLAKE2/blob/master/ref/blake2bp-ref.c#L30-L46

So the fix should make sure the `blake2xp_init_leaf` sets the correct output 
length for those nodes. What the cleanest way to achieve this is I am not sure 
yet, I'll think some more about it.

Best regards,
Samuel Neves

On 10/31/2016 05:05 AM, Pádraig Brady wrote:
> I've got this fairly well integrated with coreutils,
> and will present a patch perhaps tomorrow.
>
> In testing I hit a bug in the reference implementation,
> where I was getting random values for:
>
>   b2sum -a blake2bp -l8 /dev/null
>
> I've fixed that up locally with this patch:
>
>   https://github.com/BLAKE2/BLAKE2/pull/36
>
> thanks,
> Pádraig.