Re: [dpdk-stable] [dpdk-dev] [PATCH] cryptodev: fix SHA-1 digest enum comment

["Dybkowski, AdamX" <adamx.dybkowski@intel.com>]

> -----Original Message-----
> From: Anoob Joseph <anoobj@marvell.com>
> Sent: Tuesday, 19 May, 2020 11:40
> To: Dybkowski, AdamX <adamx.dybkowski@intel.com>; dev@dpdk.org;
> Trahe, Fiona <fiona.trahe@intel.com>; akhil.goyal@nxp.com
> Cc: stable@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] cryptodev: fix SHA-1 digest enum comment
> 
> Hi Adam,
> 
> Please see inline.
> 
> Thanks,
> Anoob
> 
> > -----Original Message-----
> > From: Dybkowski, AdamX <adamx.dybkowski@intel.com>
> > Sent: Tuesday, May 19, 2020 3:01 PM
> > To: Anoob Joseph <anoobj@marvell.com>; dev@dpdk.org; Trahe, Fiona
> > <fiona.trahe@intel.com>; akhil.goyal@nxp.com
> > Cc: stable@dpdk.org
> > Subject: [EXT] RE: [dpdk-dev] [PATCH] cryptodev: fix SHA-1 digest enum
> > comment
> >
> > External Email
> >
> > ----------------------------------------------------------------------
> > Hi.
> > My answer below.
> >
> > Adam
> >
> > > -----Original Message-----
> > > From: Anoob Joseph <anoobj@marvell.com>
> > > Sent: Tuesday, 19 May, 2020 07:54
> > > To: Dybkowski, AdamX <adamx.dybkowski@intel.com>; dev@dpdk.org;
> > > Trahe, Fiona <fiona.trahe@intel.com>; akhil.goyal@nxp.com
> > > Cc: stable@dpdk.org
> > > Subject: RE: [dpdk-dev] [PATCH] cryptodev: fix SHA-1 digest enum
> > > comment
> > >
> > > Hi Adam, Akhil,
> > >
> > > Please see inline.
> > >
> > > Thanks,
> > > Anoob
> > >
> > > > -----Original Message-----
> > > > From: dev <dev-bounces@dpdk.org> On Behalf Of Adam Dybkowski
> > > > Sent: Monday, May 18, 2020 7:54 PM
> > > > To: dev@dpdk.org; fiona.trahe@intel.com; akhil.goyal@nxp.com
> > > > Cc: Adam Dybkowski <adamx.dybkowski@intel.com>; stable@dpdk.org
> > > > Subject: [dpdk-dev] [PATCH] cryptodev: fix SHA-1 digest enum
> > > > comment
> > > >
> > > > This patch fixes improper SHA-1 digest size in the enum comment.
> > > >
> > > > Fixes: 1bd407fac80b ("cryptodev: extract symmetric operations")
> > > > Cc: stable@dpdk.org
> > > >
> > > > Signed-off-by: Adam Dybkowski <adamx.dybkowski@intel.com>
> > > > ---
> > > >  lib/librte_cryptodev/rte_crypto_sym.h | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/lib/librte_cryptodev/rte_crypto_sym.h
> > > > b/lib/librte_cryptodev/rte_crypto_sym.h
> > > > index d9585ecd6..9cea4e5f0 100644
> > > > --- a/lib/librte_cryptodev/rte_crypto_sym.h
> > > > +++ b/lib/librte_cryptodev/rte_crypto_sym.h
> > > > @@ -269,9 +269,9 @@ enum rte_crypto_auth_algorithm {
> > > >  	/**< HMAC using MD5 algorithm */
> > > >
> > > >  	RTE_CRYPTO_AUTH_SHA1,
> > > > -	/**< 128 bit SHA algorithm. */
> > > > +	/**< 160 bit SHA algorithm. */
> > > >  	RTE_CRYPTO_AUTH_SHA1_HMAC,
> > > > -	/**< HMAC using 128 bit SHA algorithm. */
> > > > +	/**< HMAC using 160 bit SHA algorithm. */
> > >
> > > [Anoob] This raises one interesting question. Is HMAC-SHA-1-96
> > > (https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org
> > > _h
> > >
> >
> tml_rfc2404&d=DwIFAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=jPfB8rwwviRSxyL
> Ws2
> > n6B-
> >
> WYLn1v9SyTMrT5EQqh2TU&m=pgqB2BfFosCF_7l1SdoodgXcipf7G1ofht68ZK
> Mt
> > oW0&s=hxzUN2QfRJGaR7NQ7VKGm5oQvOZez6Z70mqOyg7gKTY&e= )
> treated as a
> > separate algorithm or is it a digest size variant of
> > RTE_CRYPTO_AUTH_SHA1_HMAC? I assume the later.
> >
> > [Adam] DPDK doesn't have separate enums for such variations. According
> > to RFC 2104, chapter "5. Truncated output", the calculation of
> > HMAC-SHA-1-96 is done using ordinary HMAC-SHA-1, but the calculation
> > result is then truncated to 96 bits, or any other digest size provided in auth
> xform.
> 
> [Anoob] So it is allowed to support digest sizes 12 & 20, right? Can you
> update the above comment in that case?

[Adam] This depends on a particular PMD and its capabilities so we cannot write here in this public header file. For example, have a look in the capabilities structure of QAT PMD:

	{	/* SHA1 */						\
		.op = RTE_CRYPTO_OP_TYPE_SYMMETRIC,			\
		{.sym = {						\
			.xform_type = RTE_CRYPTO_SYM_XFORM_AUTH,	\
			{.auth = {					\
				.algo = RTE_CRYPTO_AUTH_SHA1,		\
				.block_size = 64,			\
				.key_size = {				\
					.min = 0,			\
					.max = 0,			\
					.increment = 0			\
				},					\
				.digest_size = {			\
					.min = 1,			\
					.max = 20,			\
					.increment = 1			\
				},					\
				.iv_size = { 0 }			\
			}, }						\
		}, }							\
	},								\

It shows QAT PMD is able to truncate the output digest to any size from 1 to 20 bytes (160 bits).

This can be different in other PMDs, for example OpenSSL and CCP PMDs allow only 20-byte digests here while Marvell MVSAM allows 12-20 bytes.

Adam