ares_parse: handle ADMD-less Authentication-Results headers#192
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thegushi wants to merge 1 commit into
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ares_parse: handle ADMD-less Authentication-Results headers#192thegushi wants to merge 1 commit into
thegushi wants to merge 1 commit into
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Office 365 generates Authentication-Results headers that omit the authserv-id (ADMD), jumping straight to method=result tokens. This is non-compliant with RFC 8601 but common enough in practice that the hard parse failure causes log noise and downstream ARC chain issues. When state 1 encounters '=' instead of ';' or a version digit, the accumulated host token is actually a method name. Recover by leaving ares_host empty and continuing from the result value. See trusteddomainproject/OpenDKIM#73
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Summary
Office 365 generates
Authentication-Resultsheaders that omit the authserv-id (ADMD), jumping straight tomethod=resulttokens:RFC 8601 requires the authserv-id before the semicolon, so these are technically non-compliant. However they are common enough in practice that the current hard parse failure causes log noise on every O365-originated message and can interfere with ARC chain construction.
Fix
In state 1 of
ares_parse(), when=is seen instead of;or a version digit, the token we read as authserv-id is actually the first method name. The fix recovers gracefully:ares_hostis left empty (signalling no authserv-id present), the token is slotted as the method, and parsing continues from the result value.The same fix has been applied to OpenDKIM (trusteddomainproject/OpenDKIM#372, with a
make checkintegration test) and OpenDMARC (trusteddomainproject/OpenDMARC#329).Test plan
Authentication-Results: spf=pass smtp.mailfrom=example.comparses without error,ares_hostis empty, method isspf, result ispassAuthentication-Results: compauth=pass reason=000parses without error, method isunknown