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dnsdist: Fix signedness issue in isEDNSOptionInOpt() #8158

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@rgacogne rgacogne commented Aug 5, 2019

Short description

Interpreting the value as signed could result in a large value being considered negative. After the addition it would be stored into an unsigned value and thus become positive again, but the result of the addition would be wrong.
This means that we could fail to locate some EDNS options whose codes are too large and, while it's extremely unlikely to happen, we could get only a partial content for some very large options.

Reported by Brian Sullivan on the mailing-list 1.

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I have:

  • read the CONTRIBUTING.md document
  • compiled this code
  • tested this code
  • included documentation (including possible behaviour changes)
  • documented the code
  • added or modified regression test(s)
  • added or modified unit test(s)
@rgacogne rgacogne added this to the dnsdist-1.4.0 milestone Aug 5, 2019
@rgacogne rgacogne merged commit bf599d8 into PowerDNS:master Aug 5, 2019
26 of 27 checks passed
@rgacogne rgacogne deleted the dnsdist-is-edns-option-in-signedness branch Aug 5, 2019
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