linux-kernel - Re: [PATCH v2] crypto: des3_ede: permit weak keys unless REQ_WEAK

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Message-ID: <493942D9.6030807@redhat.com>
Date:	Fri, 05 Dec 2008 10:03:53 -0500
From:	Jarod Wilson <jarod@...hat.com>
To:	linux-crypto@...r.kernel.org
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	Neil Horman <nhorman@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] crypto: des3_ede: permit weak keys unless REQ_WEAK_KEY
 set

Jarod Wilson wrote:
> While its a slightly insane to bypass the key1 == key2 ||
> key2 == key3 check in triple-des, since it reduces it to the
> same strength as des, some folks do need to do this from time
> to time for backwards compatibility with des.
> 
> My own case is FIPS CAVS test vectors. Many triple-des test
> vectors use a single key, replicated 3x. In order to get the
> expected results, des3_ede_setkey() needs to honor the weak
> key flag.
> 
> Also adds a warning when a weak key is rejected, otherwise,
> you silently get back a bogus result.
> 
> Signed-off-by: Jarod Wilson <jarod@...hat.com>

v2: make CRYPTO_TFM_REQ_WEAK_KEY flag usage consistent w/rest of crypto 
subsystem, per comments from Herbert in Red Hat bugzilla #474394.

---
  crypto/des_generic.c |    3 ++-
  1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/crypto/des_generic.c b/crypto/des_generic.c
index 5d0e458..9002073 100644
--- a/crypto/des_generic.c
+++ b/crypto/des_generic.c
@@ -868,7 +868,8 @@ static int des3_ede_setkey(struct crypto_tfm *tfm, 
const u8 *key,
  	u32 *flags = &tfm->crt_flags;

  	if (unlikely(!((K[0] ^ K[2]) | (K[1] ^ K[3])) ||
-		     !((K[2] ^ K[4]) | (K[3] ^ K[5]))))
+		     !((K[2] ^ K[4]) | (K[3] ^ K[5]))) &&
+		     (*flags & CRYPTO_TFM_REQ_WEAK_KEY))
  	{
  		*flags |= CRYPTO_TFM_RES_BAD_KEY_SCHED;
  		return -EINVAL;


-- 
Jarod Wilson
jarod@...hat.com
--
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