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fix(resource): refuse a request with more than one Authorization header - #513
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VerifyRequestFromHTTP read the Authorization header with Header.Get, which silently takes the first of several, and net/http doesn't reject repeats. A proxy or gateway in front that acts on another one (the last, or a merged value) would then disagree with the resource server about which credential the request carried. It already refused more than one DPoP header, and the client's backchannel notification endpoint refuses repeated Authorization headers. VerifyRequestFromHTTP now marks such a request, and Verify refuses it with a 400 invalid_request. The Authorization field's doc tells an adapter that fills the struct itself to refuse repeats first. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Summary
This fixes the pre-release security review's L2.
resource.VerifyRequestFromHTTP(#504, unreleased) usedr.Header.Get("Authorization"), which silently takes the first of several headers, andnet/httpdoesn't reject repeats. If a proxy, gateway or WAF in front acts on a different one (the last, or a merged value), it and the resource server disagree about which credential the request carried.It was also inconsistent with existing behaviour:
Authorizationheaders (client/backchannel_notification.go).Fix:
VerifyRequestFromHTTPmarks a request with more than oneAuthorizationheader, using an unexported field onVerifyRequest, so the struct's public shape doesn't change.Verifyrefuses a marked request with a 400invalid_request("multiple Authorization headers are not permitted"). The refusal comes after the method and URL checks, before the scheme is parsed.Authorizationfield's doc now says the header isn't a list (RFC 9110 §5.3). An adapter filling the struct itself must refuse repeats first rather than pass one on.It isn't breaking: one header behaves as before.
Tests
TestVerifyRefusesRepeatedAuthorization: throughVerifyRequestFromHTTPandVerify, one header verifies, and two headers (DPoP …+Bearer other) give a 400invalid_request*resource.Error.go test -race ./resource/... ./serverresource/...passes.🤖 Generated with Claude Code