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Merge pull request #4971 from SparkiDev/fp_div2_mod_ct_oob

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TFM fp_div_2_ct: rework to avoid overflow
This commit is contained in:
David Garske
2022-03-21 09:11:41 -07:00
committed by GitHub
parent 8bf14ba1d3 aa14607a6f
commit c213c725d7
1 changed files with 4 additions and 2 deletions
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6
wolfcrypt/src/tfm.c
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@ -894,11 +894,13 @@ int fp_div_2_mod_ct(fp_int *a, fp_int *b, fp_int *c)
c->dp[i] = (fp_digit)w;
w >>= DIGIT_BIT;
}
c->dp[i] = (fp_digit)w;
for (i = 0; i < b->used-1; i++) {
c->dp[i] = (c->dp[i] >> 1) | (c->dp[i+1] << (DIGIT_BIT - 1));
}
c->dp[i] = (c->dp[i] >> 1) | ((fp_digit)w << (DIGIT_BIT - 1));
c->used = i + 1;
c->sign = FP_ZPOS;
fp_clamp(c);
fp_div_2(c, c);
return FP_OKAY;
}