[PATCH] crypto: x86/poly1305 - Clear key material from stack in SSE2 variant

[PATCH] crypto: x86/poly1305 - Clear key material from stack in SSE2 variant

[Tommi Hirvola]

1-block SSE2 variant of poly1305 stores variables s1..s4 containing key
material on the stack. This commit adds missing zeroing of the stack
memory. Benchmarks show negligible performance hit (tested on i7-3770).

Signed-off-by: Tommi Hirvola <tommi@hirvola.fi>
---
Similarly, poly1305_blocks() in crypto/poly1305_generic.c stores s1..s4
as well as r0..r4 to local variables which may be stored in the stack by
the compiler. Fixing that is less trivial and left for another patch.

Tests were run with poly1305_simd_blocks() patched to call only 1-block
SSE2 poly1305 function.
---
 arch/x86/crypto/poly1305-sse2-x86_64.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/crypto/poly1305-sse2-x86_64.S b/arch/x86/crypto/poly1305-sse2-x86_64.S
index c88c670cb5fc..e6add74d78a5 100644
--- a/arch/x86/crypto/poly1305-sse2-x86_64.S
+++ b/arch/x86/crypto/poly1305-sse2-x86_64.S
@@ -272,6 +272,10 @@ ENTRY(poly1305_block_sse2)
 	dec		%rcx
 	jnz		.Ldoblock
 
+	# Zeroing of key material
+	mov		%rcx,0x00(%rsp)
+	mov		%rcx,0x08(%rsp)
+
 	add		$0x10,%rsp
 	pop		%r12
 	pop		%rbx
-- 
2.20.1

Re: [PATCH] crypto: x86/poly1305 - Clear key material from stack in SSE2 variant

[Herbert Xu]

On Tue, Feb 19, 2019 at 05:45:54PM +0200, Tommi Hirvola wrote:
> 1-block SSE2 variant of poly1305 stores variables s1..s4 containing key
> material on the stack. This commit adds missing zeroing of the stack
> memory. Benchmarks show negligible performance hit (tested on i7-3770).
> 
> Signed-off-by: Tommi Hirvola <tommi@hirvola.fi>
> ---
> Similarly, poly1305_blocks() in crypto/poly1305_generic.c stores s1..s4
> as well as r0..r4 to local variables which may be stored in the stack by
> the compiler. Fixing that is less trivial and left for another patch.
> 
> Tests were run with poly1305_simd_blocks() patched to call only 1-block
> SSE2 poly1305 function.
> ---
>  arch/x86/crypto/poly1305-sse2-x86_64.S | 4 ++++
>  1 file changed, 4 insertions(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt