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Fix unaligned access in curve25519

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Use only the safe conversion from uint8_t to uint32_t.
Actually, the ARM gcc-compiler is good enough to detect this pattern.
This commit is contained in:
Jochen Hoenicke 2018-06-22 00:33:26 +02:00 committed by Pavol Rusnak
parent c26867d6f2
commit f586155d80
1 changed files with 10 additions and 23 deletions
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33
ed25519-donna/curve25519-donna-32bit.c
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@ -403,34 +403,21 @@ void curve25519_square_times(bignum25519 out, const bignum25519 in, int count) {
/* Take a little-endian, 32-byte number and expand it into polynomial form */
void curve25519_expand(bignum25519 out, const unsigned char in[32]) {
const union { uint8_t b[2]; uint16_t s; } endian_check = {{1,0}};
uint32_t x0,x1,x2,x3,x4,x5,x6,x7;
if (endian_check.s == 1) {
/* Take care, this only works when in is aligned */
x0 = *(uint32_t *)(in + 0);
x1 = *(uint32_t *)(in + 4);
x2 = *(uint32_t *)(in + 8);
x3 = *(uint32_t *)(in + 12);
x4 = *(uint32_t *)(in + 16);
x5 = *(uint32_t *)(in + 20);
x6 = *(uint32_t *)(in + 24);
x7 = *(uint32_t *)(in + 28);
} else {
#define F(s) \
#define F(s) \
((((uint32_t)in[s + 0]) ) | \
(((uint32_t)in[s + 1]) << 8) | \
(((uint32_t)in[s + 2]) << 16) | \
(((uint32_t)in[s + 3]) << 24))
x0 = F(0);
x1 = F(4);
x2 = F(8);
x3 = F(12);
x4 = F(16);
x5 = F(20);
x6 = F(24);
x7 = F(28);
#undef F
}
x0 = F(0);
x1 = F(4);
x2 = F(8);
x3 = F(12);
x4 = F(16);
x5 = F(20);
x6 = F(24);
x7 = F(28);
#undef F
out[0] = ( x0 ) & reduce_mask_26;
out[1] = ((((uint64_t)x1 << 32) | x0) >> 26) & reduce_mask_25;