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MP int: fix word range check in mp_is_bit_set()

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Sean Parkinson
2021-03-08 15:45:04 +10:00
parent b6130513e3
commit 419b426a1b
1 changed files with 9 additions and 3 deletions
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12
wolfcrypt/src/integer.c
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@@ -1449,10 +1449,16 @@ int mp_set (mp_int * a, mp_digit b)
/* check if a bit is set */
int mp_is_bit_set (mp_int *a, mp_digit b)
{
if ((mp_digit)a->used < b/DIGIT_BIT)
return 0;
int i = (int)(b / DIGIT_BIT); /* word index */
int s = b % DIGIT_BIT; /* bit index */
return (int)((a->dp[b/DIGIT_BIT] >> b%DIGIT_BIT) & (mp_digit)1);
if (a->used <= i) {
/* no words avaialable at that bit count */
return 0;
}
/* get word and shift bit to check down to index 0 */
return (int)((a->dp[i] >> s) & (mp_digit)1);
}
/* c = a mod b, 0 <= c < b */