yuzu/mbedtls
1
0
Fork 0
mirror of https://github.com/yuzu-emu/mbedtls.git synced 2025-01-25 19:51:12 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fix undefined order of volatile access

Browse source 
Found by the IAR compiler.

While at it, make 'diff' non-volatile in uECC_check_curve_integrity(), as
there is no good reason to make it volatile, and making it volatile only
increases the code size and the burden of defining access ordering.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-12-05 15:30:09 +01:00
parent 83d7881cec
commit 645896e0ea
1 changed files with 12 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
tinycrypt/ecc.c
View file

@ -153,15 +153,20 @@ static int uECC_check_curve_integrity(void)
0x76, 0x0a, 0xe2, 0xbc, 0xce, 0x2a, 0xa2, 0xc6, 0x76, 0x0a, 0xe2, 0xbc, 0xce, 0x2a, 0xa2, 0xc6,
0x38, 0xf2, 0x19, 0x1d, 0x76, 0x72, 0x93, 0x49, 0x38, 0xf2, 0x19, 0x1d, 0x76, 0x72, 0x93, 0x49,
}; };
volatile unsigned char diff = 0; unsigned char diff = 0;
unsigned char tmp1, tmp2;
volatile unsigned i; volatile unsigned i;
if (uECC_compute_param_sha256(computed) != UECC_SUCCESS) { if (uECC_compute_param_sha256(computed) != UECC_SUCCESS) {
return UECC_FAILURE; return UECC_FAILURE;
} }
for (i = 0; i < 32; i++) for (i = 0; i < 32; i++) {
diff |= computed[i] ^ reference[i]; /* make sure the order of volatile accesses is well-defined */
tmp1 = computed[i];
tmp2 = reference[i];
diff |= tmp1 ^ tmp2;
}
/* i should be 32 */ /* i should be 32 */
mbedtls_platform_enforce_volatile_reads(); mbedtls_platform_enforce_volatile_reads();
@ -282,10 +287,13 @@ uECC_word_t uECC_vli_equal(const uECC_word_t *left, const uECC_word_t *right)
{ {
uECC_word_t diff = 0; uECC_word_t diff = 0;
uECC_word_t tmp1, tmp2;
volatile int i; volatile int i;
for (i = NUM_ECC_WORDS - 1; i >= 0; --i) { for (i = NUM_ECC_WORDS - 1; i >= 0; --i) {
diff |= (left[i] ^ right[i]); tmp1 = left[i];
tmp2 = right[i];
diff |= (tmp1 ^ tmp2);
} }
/* i should be -1 now */ /* i should be -1 now */