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Fix possible underflow in BlowfishKeyProvider.LenBigNum() #20042

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Merged
merged 1 commit into from
Jul 27, 2025
Merged

Fix possible underflow in BlowfishKeyProvider.LenBigNum() #20042

merged 1 commit into from
Jul 27, 2025

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@atlimit8
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@atlimit8 atlimit8 commented May 20, 2022

I found this possible underflow while reviewing #20020. It was originally while ((i >= 0) && (n[i] == 0)) i--; where i >= 0 was always true since i is a uint.

To see the difference try

var n = new uint[] { 0, 0, 8, 1, 0, 0 };
var i = 2U - 1;
while (i < uint.MaxValue && n[i] == 0) i--;

versus

var n = new uint[] { 0, 0, 8, 1, 0, 0 };
var i = 2U - 1;
while (n[i] == 0) i--;

abcdefg30
abcdefg30 reviewed May 20, 2022
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@atlimit8 atlimit8 force-pushed the BlowfishKeyProvider-no-wrap-around branch from 8f491f6 to bbd6c45 Compare May 8, 2025 01:18
Mailaender
Mailaender approved these changes Jul 27, 2025
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The underflow should lead to an IndexOutOfRangeException later on in BlowfishKeyProvider which has never been reported in the wild. I still think that this additional guard is useful.

@Mailaender Mailaender merged commit c56d2c1 into OpenRA:bleed Jul 27, 2025
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Mailaender commented Jul 27, 2025

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@atlimit8 @Mailaender @abcdefg30 @anvilvapre