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From: Tommi Hirvola <tommi@hirvola.fi>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>, linux-crypto@vger.kernel.org
Subject: [PATCH] crypto: x86/poly1305 - Clear key material from stack in SSE2 variant
Date: Tue, 19 Feb 2019 17:45:54 +0200	[thread overview]
Message-ID: <20190219154554.GA3009@hirvola.fi> (raw)

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


             reply	other threads:[~2019-02-19 15:52 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-19 15:45 Tommi Hirvola [this message]
2019-02-28  6:29 ` [PATCH] crypto: x86/poly1305 - Clear key material from stack in SSE2 variant Herbert Xu

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