From: Herbert Xu <herbert@gondor.apana.org.au>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Stephan Mueller <smueller@chronox.de>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Eric Biggers <ebiggers@kernel.org>
Subject: Re: [v2 PATCH 0/3] crypto: skcipher - Add support for no chaining and partial chaining
Date: Mon, 15 Jun 2020 17:30:24 +1000 [thread overview]
Message-ID: <20200615073024.GA27015@gondor.apana.org.au> (raw)
In-Reply-To: <CAMj1kXGg25JL7WCrspMwB1PVPX6vx-rOCesg08a_Fy26_ET7Sg@mail.gmail.com>
On Fri, Jun 12, 2020 at 06:10:57PM +0200, Ard Biesheuvel wrote:
>
> First of all, the default fcsize for all existing XTS implementations
> should be -1 as well, given that chaining is currently not supported
> at all at the sckipher interface layer for any of them (due to the
> fact that the IV gets encrypted with a different key at the start of
Sure. I was just too lazy to actually set the -1 everywhere. I'll
try to do that before I repost again.
> the operation). This also means it is going to be rather tricky to
> implement for h/w accelerated XTS implementations, and it seems to me
> that the only way to deal with this is to decrypt the IV in software
> before chaining the next operation, which is rather horrid and needs
> to be implemented by all of them.
I don't think we should support chaining for XTS at all so I don't
see why we need to worry about the hardware accelerated XTS code.
> Given that
>
> a) this is wholly an AF_ALG issue, as there are no in-kernel users
> currently suffering from this afaik,
> b) using AF_ALG to get access to software implementations is rather
> pointless in general, given that userspace can simply issue the same
> instructions directly
> c) fixing all XTS and CTS implementation on all arches and all
> accelerators is not a small task
>
> wouldn't it be better to special case XTS and CBC-CTS in
> algif_skcipher instead, rather than polluting the skipcher API this
> way?
As I said we need to be able to differentiate between the ones
that can chain vs. the ones that can't. Putting this knowledge
directly into algif_skcipher is just too horrid.
The alternative is to add this marker into the algorithms. My
point was that if you're going to do that you might as well go
a step further and allow cts to chain as it is so straightforward.
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2020-06-15 7:30 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 19:02 [RFC/RFT PATCH 0/2] crypto: add CTS output IVs for arm64 and testmgr Ard Biesheuvel
2020-05-19 19:02 ` [RFC/RFT PATCH 1/2] crypto: arm64/aes - align output IV with generic CBC-CTS driver Ard Biesheuvel
2020-05-19 19:02 ` [RFC/RFT PATCH 2/2] crypto: testmgr - add output IVs for AES-CBC with ciphertext stealing Ard Biesheuvel
2020-05-19 19:04 ` [RFC/RFT PATCH 0/2] crypto: add CTS output IVs for arm64 and testmgr Ard Biesheuvel
2020-05-20 6:03 ` Stephan Mueller
2020-05-20 6:40 ` Ard Biesheuvel
2020-05-20 6:47 ` Stephan Mueller
2020-05-20 6:54 ` Ard Biesheuvel
2020-05-20 7:01 ` Stephan Mueller
2020-05-20 7:09 ` Ard Biesheuvel
2020-05-21 13:01 ` Gilad Ben-Yossef
2020-05-21 13:23 ` Ard Biesheuvel
2020-05-23 18:52 ` Stephan Müller
2020-05-23 22:40 ` Ard Biesheuvel
2020-05-28 7:33 ` Herbert Xu
2020-05-28 8:33 ` Ard Biesheuvel
2020-05-29 8:05 ` Herbert Xu
2020-05-29 8:20 ` Ard Biesheuvel
2020-05-29 11:51 ` Herbert Xu
2020-05-29 12:00 ` Ard Biesheuvel
2020-05-29 12:02 ` Herbert Xu
2020-05-29 13:10 ` Ard Biesheuvel
2020-05-29 13:19 ` Herbert Xu
2020-05-29 13:41 ` Ard Biesheuvel
2020-05-29 13:42 ` Herbert Xu
2020-06-12 12:06 ` [PATCH 0/3] crypto: skcipher - Add support for no chaining and partial chaining Herbert Xu
2020-06-12 12:07 ` [PATCH 1/3] crypto: skcipher - Add final chunk size field for chaining Herbert Xu
2020-06-12 12:15 ` Stephan Mueller
2020-06-12 12:16 ` Herbert Xu
2020-06-12 12:21 ` [v2 PATCH 0/3] crypto: skcipher - Add support for no chaining and partial chaining Herbert Xu
2020-06-12 12:21 ` [v2 PATCH 1/3] crypto: skcipher - Add final chunk size field for chaining Herbert Xu
2020-06-12 12:21 ` [v2 PATCH 2/3] crypto: algif_skcipher - Add support for fcsize Herbert Xu
2020-06-12 12:21 ` [v2 PATCH 3/3] crypto: cts - Add support for chaining Herbert Xu
2020-06-12 16:10 ` [v2 PATCH 0/3] crypto: skcipher - Add support for no chaining and partial chaining Ard Biesheuvel
2020-06-15 7:30 ` Herbert Xu [this message]
2020-06-15 7:50 ` Ard Biesheuvel
2020-06-15 18:50 ` Eric Biggers
2020-06-15 23:18 ` Ard Biesheuvel
2020-06-16 11:04 ` Herbert Xu
2020-06-16 16:53 ` Eric Biggers
2020-06-12 12:07 ` [PATCH 2/3] crypto: algif_skcipher - Add support for fcsize Herbert Xu
2020-06-12 12:07 ` [PATCH 3/3] crypto: cts - Add support for chaining Herbert Xu
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