29 lines
1.4 KiB
Diff
29 lines
1.4 KiB
Diff
From 2db25de Phoenix HEAD (2026-03-27)
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Subject: [PATCH phoenix-0001] Fix CWE-407: store event_intercepts as MapSet for O(1) dispatch lookup
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The fastlane tuple stores event_intercepts as a plain list (the result of
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channel.__intercepts__(), which returns @phoenix_intercepts — a list).
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In dispatch/3, `event in event_intercepts` is called once per subscriber per
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broadcast. With N subscribers and K intercepted events this is O(N*K) list
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scans. Storing as MapSet at subscribe time makes the per-dispatch check O(1).
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No change to the `event in event_intercepts` expression is needed — Elixir's
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`in` operator dispatches to Enumerable.member?/2, which for MapSet is O(1).
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CWE-407: Algorithmic Complexity (Inefficient Algorithmic Complexity)
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---
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lib/phoenix/channel/server.ex | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/lib/phoenix/channel/server.ex b/lib/phoenix/channel/server.ex
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index xxxxxxx..yyyyyyy 100644
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--- a/lib/phoenix/channel/server.ex
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+++ b/lib/phoenix/channel/server.ex
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@@ -440,7 +440,7 @@ defmodule Phoenix.Channel.Server do
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Process.monitor(transport_pid)
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- fastlane = {:fastlane, transport_pid, serializer, channel.__intercepts__()}
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+ fastlane = {:fastlane, transport_pid, serializer, MapSet.new(channel.__intercepts__())}
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PubSub.subscribe(pubsub_server, topic, metadata: fastlane)
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{:noreply, %{socket | joined: true}}
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