From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Stephan Mueller <smueller@chronox.de>
Cc: David Gstir <david@sigma-star.at>, Theodore Ts'o <tytso@mit.edu>,
Eric Biggers <ebiggers@google.com>,
Martin Willi <martin@strongswan.org>,
Eric Biggers <ebiggers3@gmail.com>,
Michael Halcrow <mhalcrow@google.com>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
linux-f2fs-devel@lists.sourceforge.net,
linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
linux-ext4@vger.kernel.org, Paul Crowley <paulcrowley@google.com>
Subject: Re: [PATCH] fscrypt: add support for ChaCha20 contents encryption
Date: Fri, 8 Dec 2017 10:27:07 +0000 [thread overview]
Message-ID: <CAKv+Gu-5htHxD3gOLWdSNabfiHD=_ssdZLsdksv3FJ_ueK=XEQ@mail.gmail.com> (raw)
In-Reply-To: <6974144.ZTrPlmK77A@tauon.chronox.de>
On 8 December 2017 at 10:14, Stephan Mueller <smueller@chronox.de> wrote:
> Am Freitag, 8. Dezember 2017, 11:06:31 CET schrieb Ard Biesheuvel:
>
> Hi Ard,
>
>>
>> Given how it is not uncommon for counters to be used as IV, this is a
>> fundamental flaw that could rear its head in other places as well, so
>> I propose we fix this one way (fix the current code) or the other
>> (deprecate the current code and create a new chacha20-rfc7539
>> blockcipher that uses a 96-bit IV and sets the counter to 0)
>
> Instead of having a complete new implementation of the ChaCha20 cipher, what
> about using a specific IV generator for which the kernel crypto API has
> already support (see crypto/seqiv.c for example)?
>
> I.e. we have the current ChaCha20 cipher, but use some "rfc7539iv(chacha20)"
> cipher mode where that rfc7539iv is the mentioned IV generator that turns the
> given IV (sector number?) into the proper IV for ChaCha20.
>
To be honest, I don't fully understand how the IV generators work.
seqiv is implemented as an AEAD not as a skcipher, and we'd need to
wrap chacha20 in something that is usable as a skcipher.
In any case, it does make sense to address this by wrapping chacha20
in something generic, rather than having to extend all
implementations.
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WARNING: multiple messages have this Message-ID (diff)
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Stephan Mueller <smueller@chronox.de>
Cc: Eric Biggers <ebiggers3@gmail.com>,
linux-fscrypt@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Michael Halcrow <mhalcrow@google.com>,
Paul Crowley <paulcrowley@google.com>,
Martin Willi <martin@strongswan.org>,
David Gstir <david@sigma-star.at>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH] fscrypt: add support for ChaCha20 contents encryption
Date: Fri, 8 Dec 2017 10:27:07 +0000 [thread overview]
Message-ID: <CAKv+Gu-5htHxD3gOLWdSNabfiHD=_ssdZLsdksv3FJ_ueK=XEQ@mail.gmail.com> (raw)
In-Reply-To: <6974144.ZTrPlmK77A@tauon.chronox.de>
On 8 December 2017 at 10:14, Stephan Mueller <smueller@chronox.de> wrote:
> Am Freitag, 8. Dezember 2017, 11:06:31 CET schrieb Ard Biesheuvel:
>
> Hi Ard,
>
>>
>> Given how it is not uncommon for counters to be used as IV, this is a
>> fundamental flaw that could rear its head in other places as well, so
>> I propose we fix this one way (fix the current code) or the other
>> (deprecate the current code and create a new chacha20-rfc7539
>> blockcipher that uses a 96-bit IV and sets the counter to 0)
>
> Instead of having a complete new implementation of the ChaCha20 cipher, what
> about using a specific IV generator for which the kernel crypto API has
> already support (see crypto/seqiv.c for example)?
>
> I.e. we have the current ChaCha20 cipher, but use some "rfc7539iv(chacha20)"
> cipher mode where that rfc7539iv is the mentioned IV generator that turns the
> given IV (sector number?) into the proper IV for ChaCha20.
>
To be honest, I don't fully understand how the IV generators work.
seqiv is implemented as an AEAD not as a skcipher, and we'd need to
wrap chacha20 in something that is usable as a skcipher.
In any case, it does make sense to address this by wrapping chacha20
in something generic, rather than having to extend all
implementations.
next prev parent reply other threads:[~2017-12-08 10:27 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-08 1:38 [PATCH] fscrypt: add support for ChaCha20 contents encryption Eric Biggers
2017-12-08 2:51 ` Jason A. Donenfeld
2017-12-08 7:20 ` Ard Biesheuvel
2017-12-08 21:42 ` Eric Biggers
2017-12-09 15:40 ` Geo Kozey
2017-12-10 19:05 ` Eric Biggers
2017-12-11 16:11 ` David Gstir
2017-12-08 9:11 ` Ard Biesheuvel
2017-12-08 9:11 ` Ard Biesheuvel
2017-12-08 10:06 ` Ard Biesheuvel
2017-12-08 10:06 ` Ard Biesheuvel
2017-12-08 10:14 ` Stephan Mueller
2017-12-08 10:27 ` Ard Biesheuvel [this message]
2017-12-08 10:27 ` Ard Biesheuvel
2017-12-09 0:48 ` Jeffrey Walton
2017-12-10 18:59 ` Eric Biggers
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