IPSec hmac(sha256) truncation bits length

IPSec hmac(sha256) truncation bits length

[Nicolae Rosia]

Hello,

I'm trying to understand why icv_truncbits is set to 96 for
hmac(sha256) in xfrm_algo.c because
RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.
Am I looking in the wrong place?

[1] https://tools.ietf.org/html/rfc4868#section-2.6

Best regards,
Nicolae Rosia

Re: IPSec hmac(sha256) truncation bits length

[Nicolae Rosia]

+ CC net, James Morris

On Wed, Mar 4, 2015 at 7:13 PM, Nicolae Rosia <nicolae.rosia@gmail.com> wrote:
> Hello,
>
> I'm trying to understand why icv_truncbits is set to 96 for
> hmac(sha256) in xfrm_algo.c because
> RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.
> Am I looking in the wrong place?
>
> [1] https://tools.ietf.org/html/rfc4868#section-2.6
>
> Best regards,
> Nicolae Rosia

Re: IPSec hmac(sha256) truncation bits length

[Andreas Steffen]

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Hi Nicolae,

up to the Linux 2.6.32 kernel the SHA256 hash was erroneously truncated
to 96 bits. With Linux 2.6.33 the correct truncation to 128 bits
was introduce as well as the SHA384_192 and SHA512_256 data integrity
algorithms. If you want to apply the correct SHA2 truncation, use
XFRMA_ALG_AUTH_TRUNC instead of XFRMA_ALG_AUTH.

Best regards

Andreas

On 03/04/2015 06:13 PM, Nicolae Rosia wrote:
> Hello,
> 
> I'm trying to understand why icv_truncbits is set to 96 for
> hmac(sha256) in xfrm_algo.c because
> RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.
> Am I looking in the wrong place?
> 
> [1] https://tools.ietf.org/html/rfc4868#section-2.6
> 
> Best regards,
> Nicolae Rosia
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-- 
======================================================================
Andreas Steffen                         andreas.steffen@strongswan.org
strongSwan - the Open Source VPN Solution!          www.strongswan.org
Institute for Internet Technologies and Applications
University of Applied Sciences Rapperswil
CH-8640 Rapperswil (Switzerland)
===========================================================[ITA-HSR]==


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Re: IPSec hmac(sha256) truncation bits length

[Kim Phillips]

On Wed, 4 Mar 2015 20:28:26 +0200
Nicolae Rosia <nicolae.rosia@gmail.com> wrote:

> On Wed, Mar 4, 2015 at 7:13 PM, Nicolae Rosia <nicolae.rosia@gmail.com> wrote:
> > I'm trying to understand why icv_truncbits is set to 96 for
> > hmac(sha256) in xfrm_algo.c because
> > RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.

See http://comments.gmane.org/gmane.linux.kernel.cryptoapi/6767

Kim

Re: IPSec hmac(sha256) truncation bits length

[Nicolae Rosia]

Thank you, Andreas and Kim.

Best regards,
Nicolae Rosia

On Wed, Mar 4, 2015 at 8:38 PM, Kim Phillips <kim.phillips@freescale.com> wrote:
> On Wed, 4 Mar 2015 20:28:26 +0200
> Nicolae Rosia <nicolae.rosia@gmail.com> wrote:
>
>> On Wed, Mar 4, 2015 at 7:13 PM, Nicolae Rosia <nicolae.rosia@gmail.com> wrote:
>> > I'm trying to understand why icv_truncbits is set to 96 for
>> > hmac(sha256) in xfrm_algo.c because
>> > RFC4868 [1] says that the truncation length for HMAC-SHA256 should be 128.
>
> See http://comments.gmane.org/gmane.linux.kernel.cryptoapi/6767
>
> Kim