linux-kernel - [PATCH URGENT crypto v2] crypto: arm64/chacha

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Message-Id: <20200319022732.166085-1-Jason@zx2c4.com>
Date:   Wed, 18 Mar 2020 20:27:32 -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 v2] 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: "why do images look weird on webpages?" 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. It also fixes up a bug in the (optional,
costly) stride test that prevented it from running on arm64.

Fixes: b3aad5bad26a ("crypto: arm64/chacha - expose arm64 ChaCha routine as library function")
Reported-and-tested-by: Emil Renner Berthing <kernel@...il.dk>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: stable@...r.kernel.org # v5.5+
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 arch/arm64/crypto/chacha-neon-glue.c   |  8 ++++----
 lib/crypto/chacha20poly1305-selftest.c | 11 ++++++++---
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/crypto/chacha-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
index c1f9660d104c..37ca3e889848 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] += DIV_ROUND_UP(l, CHACHA_BLOCK_SIZE);
 	}
 }
 
diff --git a/lib/crypto/chacha20poly1305-selftest.c b/lib/crypto/chacha20poly1305-selftest.c
index c391a91364e9..fa43deda2660 100644
--- a/lib/crypto/chacha20poly1305-selftest.c
+++ b/lib/crypto/chacha20poly1305-selftest.c
@@ -9028,10 +9028,15 @@ bool __init chacha20poly1305_selftest(void)
 	     && total_len <= 1 << 10; ++total_len) {
 		for (i = 0; i <= total_len; ++i) {
 			for (j = i; j <= total_len; ++j) {
+				k = 0;
 				sg_init_table(sg_src, 3);
-				sg_set_buf(&sg_src[0], input, i);
-				sg_set_buf(&sg_src[1], input + i, j - i);
-				sg_set_buf(&sg_src[2], input + j, total_len - j);
+				if (i)
+					sg_set_buf(&sg_src[k++], input, i);
+				if (j - i)
+					sg_set_buf(&sg_src[k++], input + i, j - i);
+				if (total_len - j)
+					sg_set_buf(&sg_src[k++], input + j, total_len - j);
+				sg_init_marker(sg_src, k);
 				memset(computed_output, 0, total_len);
 				memset(input, 0, total_len);
 
-- 
2.25.1