Re: [CRYPTO]: Miscompiling sha256.c by gcc 3.2.3 and arch pentium3,4

[James Morris]

On Fri, 30 Jan 2004, Jakub Jelinek wrote:

> The problematic line in sha256.c is:
> static void sha256_final(void* ctx, u8 *out)
> {
> ...
> 	const u8 padding[64] = { 0x80, };
> 
> where if you are unlucky, scheduler will with various different GCC versions
> on various architectures reorder instructions so that store of 0x80 into the
> struct is before clearing of the 64 bytes.
> 
> On the other side, doing this in sha256.c seems quite inefficient, IMHO much
> better would be to have there static u8 padding[64] = { 0x80 };
> because that will not mean clearing 64 bytes and writing another one on top
> of it every time the routine is executed.

Proposed patch below.  I think sha512 would have been ok, but might as 
well make them the same.

R Chan, please test and let us know if it fixes the problem for you.


- James
-- 
James Morris
<jmorris@xxxxxxxxxx>

diff -urN -X dontdiff linux-2.6.2-rc2-mm2.o/crypto/sha256.c linux-2.6.2-rc2-mm2.w/crypto/sha256.c
--- linux-2.6.2-rc2-mm2.o/crypto/sha256.c	2003-09-27 20:50:15.000000000 -0400
+++ linux-2.6.2-rc2-mm2.w/crypto/sha256.c	2004-01-30 11:27:26.465531792 -0500
@@ -295,7 +295,7 @@
 	u8 bits[8];
 	unsigned int index, pad_len, t;
 	int i, j;
-	const u8 padding[64] = { 0x80, };
+	static u8 padding[64] = { 0x80, };
 
 	/* Save number of bits */
 	t = sctx->count[0];
diff -urN -X dontdiff linux-2.6.2-rc2-mm2.o/crypto/sha512.c linux-2.6.2-rc2-mm2.w/crypto/sha512.c
--- linux-2.6.2-rc2-mm2.o/crypto/sha512.c	2003-09-27 20:51:04.000000000 -0400
+++ linux-2.6.2-rc2-mm2.w/crypto/sha512.c	2004-01-30 11:32:16.182488120 -0500
@@ -249,7 +249,7 @@
 {
         struct sha512_ctx *sctx = ctx;
 	
-        const static u8 padding[128] = { 0x80, };
+        static u8 padding[128] = { 0x80, };
 
         u32 t;
 	u64 t2;

-
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