netdev - [PATCH 1/3] sha512: make it work, undo percpu message schedule

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Message-ID: <20120114182737.GB4207@p183.telecom.by>
Date:	Sat, 14 Jan 2012 21:27:37 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	linux-crypto@...r.kernel.org, netdev@...r.kernel.org,
	ken@...elabs.ch, Steffen Klassert <steffen.klassert@...unet.com>,
	Eric Dumazet <eric.dumazet@...il.com>, security@...nel.org
Subject: [PATCH 1/3] sha512: make it work, undo percpu message schedule

commit f9e2bca6c22d75a289a349f869701214d63b5060
aka "crypto: sha512 - Move message schedule W[80] to static percpu area"
created global message schedule area.

If sha512_update will ever be entered twice, hash will be silently
calculated incorrectly.

Probably the easiest way to notice incorrect hashes being calculated is
to run 2 ping floods over AH with hmac(sha512):

	#!/usr/sbin/setkey -f
	flush;
	spdflush;
	add IP1 IP2 ah 25 -A hmac-sha512 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000025;
	add IP2 IP1 ah 52 -A hmac-sha512 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000052;
	spdadd IP1 IP2 any -P out ipsec ah/transport//require;
	spdadd IP2 IP1 any -P in  ipsec ah/transport//require;

XfrmInStateProtoError will start ticking with -EBADMSG being returned
from ah_input(). This never happens with, say, hmac(sha1).

With patch applied (on BOTH sides), XfrmInStateProtoError does not tick
with multiple bidirectional ping flood streams like it doesn't tick
with SHA-1.

After this patch sha512_transform() will start using ~750 bytes of stack on x86_64.
This is OK for simple loads, for something more heavy, stack reduction will be done
separatedly.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
Cc: stable@...r.kernel.org
---

 crypto/sha512_generic.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

--- a/crypto/sha512_generic.c
+++ b/crypto/sha512_generic.c
@@ -21,8 +21,6 @@
 #include <linux/percpu.h>
 #include <asm/byteorder.h>
 
-static DEFINE_PER_CPU(u64[80], msg_schedule);
-
 static inline u64 Ch(u64 x, u64 y, u64 z)
 {
         return z ^ (x & (y ^ z));
@@ -89,7 +87,7 @@ sha512_transform(u64 *state, const u8 *input)
 	u64 a, b, c, d, e, f, g, h, t1, t2;
 
 	int i;
-	u64 *W = get_cpu_var(msg_schedule);
+	u64 W[80];
 
 	/* load the input */
         for (i = 0; i < 16; i++)
@@ -128,8 +126,6 @@ sha512_transform(u64 *state, const u8 *input)
 
 	/* erase our data */
 	a = b = c = d = e = f = g = h = t1 = t2 = 0;
-	memset(W, 0, sizeof(__get_cpu_var(msg_schedule)));
-	put_cpu_var(msg_schedule);
 }
 
 static int
--
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