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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Emil Renner Berthing <kernel@esmil.dk>,
	Ard Biesheuvel <ardb@kernel.org>, stable <stable@vger.kernel.org>
Subject: Re: [PATCH URGENT crypto] crypto: arm64/chacha - correctly walk through blocks
Date: Wed, 18 Mar 2020 19:33:18 -0600	[thread overview]
Message-ID: <CAHmME9otcAe7H4Anan8Tv1KreTZtwt4XXEPMG--x2Ljr0M+o1Q@mail.gmail.com> (raw)
In-Reply-To: <20200319002359.GF2334@sol.localdomain>

Hey Eric,

On Wed, Mar 18, 2020 at 6:24 PM Eric Biggers <ebiggers@kernel.org> wrote:
> Thanks for fixing this!  We definitely should get this fix to Linus for 5.6.
> But I don't think your description of this bug dating back to 2018 is accurate,
> because this bug only affects the new library interface to ChaCha20 which was
> added in v5.5.  In the "regular" crypto API case, the "walksize" is set to
> '5 * CHACHA_BLOCK_SIZE', and chacha_doneon() is guaranteed to be called with a
> multiple of '5 * CHACHA_BLOCK_SIZE' except at the end.  Thus the code worked
> fine with the regular crypto API.

Ahhh, that seems correct.

> > +             state[12] += round_up(l, CHACHA_BLOCK_SIZE) / CHACHA_BLOCK_SIZE;
>
> Use DIV_ROUND_UP(l, CHACHA_BLOCK_SIZE)?

Duh, oops, thanks. Will send a v2 in a few minutes.

By the way, I took a brief look at the other implementations
accessible from lib/crypto and I didn't see the same issue over there.
But I wouldn't mind an extra pair of eyes, if you want to give it a
quick look too.

Jason

  parent reply	other threads:[~2020-03-19  1:33 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 23:45 Jason A. Donenfeld
2020-03-19  0:23 ` Eric Biggers
2020-03-19  0:30   ` Eric Biggers
2020-03-19  1:33   ` Jason A. Donenfeld [this message]
2020-03-19  2:27     ` [PATCH URGENT crypto v2] " Jason A. Donenfeld
2020-03-19  3:25       ` Eric Biggers
2020-03-19  4:25         ` Jason A. Donenfeld
2020-03-19  4:36           ` Jason A. Donenfeld
2020-03-19 19:03       ` Eric Biggers
2020-03-20  3:48       ` Herbert Xu
2020-03-20  4:01         ` Jason A. Donenfeld

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