Resolve request headers by presence rather than truthiness - #140
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The `server.HTTP_*` parameter source read an arbitrary header with a truthiness check, so a header present with an empty value resolved to nothing at all — indistinguishable from a header that was never sent. A rule authored as a presence check against a header therefore matched every non-empty value and silently missed the empty one, which is the worst kind of gap: the rule reports as active protection while one spelling of the input walks past it. Resolve the generic `HTTP_*` branch by presence instead, reading only own properties so an inherited name like `constructor` cannot masquerade as a header that every request carries. The named cases (host, origin, referer, user-agent, content-type, content-length) keep value semantics deliberately: they feed matchers for which an empty string and an absent header already mean the same thing, and handing those an empty string instead of nothing would change comparisons that are working correctly. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Handles header presence accurately with clear logic and thorough tests. 🎯 Quality: 100% Elite · 📦 Size: Small 📈 This month: Your 67th PR — above team average · Averaging Excellent |
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iv1310
approved these changes
Aug 18, 2026
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What
server.HTTP_*resolved an arbitrary request header with a truthiness check, so a header present with an empty value resolved to nothing — indistinguishable from a header that was never sent.That makes a presence-based header rule quietly incomplete. It matches every non-empty value and misses the empty one, which is the failure mode worth caring about: the rule reports as active protection while one spelling of the input walks past it. Presence checks exist precisely for inputs where no value pattern is safe to depend on, so "present but empty" is exactly the case they must not lose.
Change
The generic
HTTP_*branch now resolves by presence, reading only own properties so an inherited name (constructor) cannot masquerade as a header every request carries.The named cases — host, origin, referer, user-agent, content-type, content-length — keep value semantics on purpose. They feed matchers for which an empty string and an absent header already mean the same thing, and handing those
''instead of nothing would change comparisons that behave correctly today.Tests
Three resolver cases: an empty header value resolves to
['']; an absent header still resolves to[]; and an inherited property name resolves to[]on an empty headers object.Full suite green (1013 tests) — nothing depended on the old behaviour.
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