From e29adedfc5faea67603e9205c5af88974b1f7a4f Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Wed, 16 Jan 2019 15:29:19 +0100
Subject: [PATCH] sys/crypto/aes: avoid UB by explicit unsigned integer
promotion
---
sys/crypto/aes.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/sys/crypto/aes.c b/sys/crypto/aes.c
index c8809640c7..2eccf01699 100644
--- a/sys/crypto/aes.c
+++ b/sys/crypto/aes.c
@@ -471,7 +471,12 @@ static const u32 Td0[256] = {
#define Td1(n) ((Td0[n] >> 8) | (Td0[n] << 24))
#define Td2(n) ((Td0[n] >> 16) | (Td0[n] << 16))
#define Td3(n) ((Td0[n] >> 24) | (Td0[n] << 8))
- #define Td4(n) (Td4[n] | (Td4[n] << 8) | (Td4[n] << 16) | (Td4[n] << 24))
+
+ /* helper to prevent the u8 to be promoted to signed int, which would turn
+ * left shift by 24 into undefined behaviour */
+ #define Td4u(n) ((u32)Td4[n])
+
+ #define Td4(n) (Td4u(n) | (Td4u(n) << 8) | (Td4u(n) << 16) | (Td4u(n) << 24))
static const u8 Td4[256] = {
0x52U, 0x09U, 0x6aU, 0xd5U, 0x30U, 0x36U, 0xa5U, 0x38U,
--
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