linux-kernel - Re: [PATCH v2] DRBG: fix maximum value checks on 32 bit systems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 26 Aug 2014 16:43:43 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Stephan Mueller <smueller@...onox.de>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] DRBG: fix maximum value checks on 32 bit systems

On Tue, Aug 26, 2014 at 10:29:45AM +0200, Stephan Mueller wrote:
> The maximum values for additional input string or generated blocks is
> larger than 1<<32. To ensure a sensible value on 32 bit systems, return
> SIZE_MAX on 32 bit systems. This value is lower than the maximum
> allowed values defined in SP800-90A. The standard allow lower maximum
> values, but not larger values.
> 
> SIZE_MAX - 1 is used for drbg_max_addtl to allow
> drbg_healthcheck_sanity to check the enforcement of the variable
> without wrapping.

This is really ugly but OK.  However, I'm not sure how the sanity
check ever worked.  It would appear that the drbg_generate call in
drbg_healthcheck_sanity should always fail because you explicitly
set addtl->len to drbg_max_addtl + 1, which should trigger the
"DRBG: additional information string too long" error, no?

Obviously it's working for you but I'd like to understand why
it's working and whether it'll continue to work.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/