linux-kernel - [PATCH URGENT crypto] crypto: arm64/chacha

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Date:   Wed, 18 Mar 2020 17:45:18 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        gregkh@...uxfoundation.org, herbert@...dor.apana.org.au
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Ard Biesheuvel <ardb@...nel.org>, stable@...r.kernel.org
Subject: [PATCH URGENT crypto] crypto: arm64/chacha - correctly walk through blocks

Prior, passing in chunks of 2, 3, or 4, followed by any additional
chunks would result in the chacha state counter getting out of sync,
resulting in incorrect encryption/decryption, which is a pretty nasty
crypto vuln, dating back to 2018. WireGuard users never experienced this
prior, because we have always, out of tree, used a different crypto
library, until the recent Frankenzinc addition. This commit fixes the
issue by advancing the pointers and state counter by the actual size
processed.

Fixes: f2ca1cbd0fb5 ("crypto: arm64/chacha - optimize for arbitrary length inputs")
Reported-and-tested-by: Emil Renner Berthing <kernel@...il.dk>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: stable@...r.kernel.org
---
 arch/arm64/crypto/chacha-neon-glue.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/crypto/chacha-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
index c1f9660d104c..debb1de0d3dd 100644
--- a/arch/arm64/crypto/chacha-neon-glue.c
+++ b/arch/arm64/crypto/chacha-neon-glue.c
@@ -55,10 +55,10 @@ static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
 			break;
 		}
 		chacha_4block_xor_neon(state, dst, src, nrounds, l);
-		bytes -= CHACHA_BLOCK_SIZE * 5;
-		src += CHACHA_BLOCK_SIZE * 5;
-		dst += CHACHA_BLOCK_SIZE * 5;
-		state[12] += 5;
+		bytes -= l;
+		src += l;
+		dst += l;
+		state[12] += round_up(l, CHACHA_BLOCK_SIZE) / CHACHA_BLOCK_SIZE;
 	}
 }
 
-- 
2.25.1