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sys/crypto/aes: avoid UB by explicit unsigned integer promotion

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This commit is contained in:
Kaspar Schleiser 2019-01-16 15:29:19 +01:00
parent e65a017f19
commit e29adedfc5
1 changed files with 6 additions and 1 deletions
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7
sys/crypto/aes.c
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@ -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,