Three findings from the review of the per-target request headers
feature, plus the follow-up they raised about the inbound headers
the same delivery path forwards.
One rule now governs every header a delivery carries on someone
else's behalf: a redirect hop that leaves the origin the target
names carries none of them. That covers the operator's configured
headers and the inbound event headers forwarded from the sender
alike. net/http withholds only Authorization and Cookie across a
host change, so an operator's X-Api-Key or a sender's
X-Hub-Signature would otherwise follow a 302 to a host nobody
configured. Redirects are still followed — refusing them would
break every destination that legitimately redirects and would
record the 3xx as the delivery's result — but a hop to another
host, another port, or down from https to http drops the lot. The
shared SSRF-safe transport is kept on that client, so each hop is
still dialled through the private-IP guard.
The set to strip is not a name list. applyRequestHeaders now
returns the canonical names of everything it applied on the
sender's or operator's behalf, and the redirect policy strips
exactly that, so a header added to the forward set is covered
without a second edit. Content-Type and User-Agent are the
delivery path's own and always travel; a 307 preserves the body
across hosts and it has to stay typed.
The origin comparison no longer collapses two IPv6 origins into
one. Hostname() unwraps a literal's brackets, so re-appending the
port with a bare colon rendered https://[2001:db8::1]:8080 and
https://[2001:db8::1:8080] identically — a different address on a
different port passing as the same origin. The port is joined with
net.JoinHostPort, and both spellings are in TestSameDeliveryOrigin.
The ten-hop cap gains a regression test. Installing a CheckRedirect
is precisely what discards net/http's own limit, so a
self-redirecting destination is driven through the policy and
asserted to stop after exactly ten requests with the sentinel
surfacing to the caller.
Trailer joins the reserved names. net/http strips it from the
request it writes, so a configured one was accepted, stored, and
provably never sent.
The invalid-header-name error no longer quotes the text before the
first colon. That text is only a name if it parses as one; when it
does not, a pasted value whose own colon split the line put half a
token into a 400 body. TestParseTargetHeaders_ErrorsNeverQuoteAValue
asserted this invariant while only exercising the after-the-colon
case, and now covers the before-the-colon one.
README documents the http target's config keys, the 300-second
timeout ceiling, the reserved-header list and the redirect
behaviour as one rule over both header classes, including that the
drop is per hop rather than permanent: net/http re-copies the
initial request's headers each hop, so a chain returning to the
configured origin carries them again, exactly as it treats
Authorization. The edit form's hint gains Trailer and the redirect
note.
Closes#243
