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Re: [quicwg/base-drafts] Correct overflow checks on packet number decoding algorithm (#3188)

Antoine Delignat-Lavaud <notifications@github.com> Tue, 05 November 2019 14:50 UTC

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Date: Tue, 05 Nov 2019 12:39:45 +0000
From: Antoine Delignat-Lavaud <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Correct overflow checks on packet number decoding algorithm (#3188)
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ad-l commented on this pull request.



> @@ -6057,12 +6057,15 @@ DecodePacketNumber(largest_pn, truncated_pn, pn_nbits):
    // The following code calculates a candidate value and
    // makes sure it's within the packet number window.
    candidate_pn = (expected_pn & ~pn_mask) | truncated_pn
-   if candidate_pn <= expected_pn - pn_hwin:
+   // Note the extra check for overflow when candidate_pn
+   // is near MAX_PACKET_NUMBER
+   if candidate_pn <= expected_pn - pn_hwin and
+      candidate_pn + pn_win < 1 << 62:

Yes, agreed

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