[dm-devel] [PATCH] crypto/mcryptd: Check mcryptd algorithm compatability

[Herbert Xu]

On Fri, Dec 02, 2016 at 04:15:21PM -0800, Tim Chen wrote:
> Algorithms not compatible with mcryptd could be spawned by mcryptd
> with a direct crypto_alloc_tfm invocation using a "mcryptd(alg)"
> name construct.  This causes mcryptd to crash the kernel if
> "alg" is incompatible and not intended to be used with mcryptd.
> 
> A flag CRYPTO_ALG_MCRYPT is being added to mcryptd compatible
> algorithms' cra_flags. The compatability is checked when mcryptd spawn
> off an algorithm.
> 
> Link: http://marc.info/?l=linux-crypto-vger&m=148063683310477&w=2
> Cc: stable at vger.kernel.org
> Reported-by: Mikulas Patocka <mpatocka at redhat.com>
> Tested-by: Megha Dey <megha.dey at linux.intel.com>
> Signed-off-by: Tim Chen <tim.c.chen at linux.intel.com>

Tim, I think we should instead make mcryptd refuse to generate
a non-internal algorithm.  This way the user would not be able
to access it at all since they can only request for non-internal
algorithms.

Basically you want to check at the start of mcryptd_create_hash
that the INTERNAL bit is set on both the type and mask as returned
by crypto_get_attr_type.

Thanks,
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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