fix(http): refuse the free-instance hatch on a listener anyone can reach - #645
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jmrplens wants to merge 3 commits into
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fix(http): refuse the free-instance hatch on a listener anyone can reach#645jmrplens wants to merge 3 commits into
jmrplens wants to merge 3 commits into
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`--allow-any-gitlab-url` publishes no instance and lets the `GITLAB-URL` header name any host, which is the request forgery of GHSA-fcj2-hj27-hj26 opted into: this server makes the request, with the token that caller supplied, and hands the response back to them. That is defensible only when the caller can only be the operator, and the flag's own warning said as much in a sentence nobody enforced. On a wildcard bind, which is exactly what the container CMD does, the hatch was reachable from the whole network and the server started anyway. `--http-addr` must now bind a loopback address or a unix socket for the hatch to be accepted. A socket qualifies for a stronger reason than a port does: it resolves to a file rather than a name, so no remote peer can reach it at all, and `--http-socket-mode` decides which local principals may. A container binding `0.0.0.0` and published on host loopback is host-local in fact and is refused anyway, since nothing inside the process distinguishes it from the same container published on every interface. Such a deployment names its instance, which is what every other container deployment does; the docs say so where they used to say the hatch merely warned. The built-in help offered `--allow-any-gitlab-url --http-addr=:8080` as an example, which no longer starts, and the TLS guide showed a command with no `--gitlab-url` at all, which has not started since the allow-list landed. Both are corrected. The refusal names the address it judged: an operator reading "reachable from the network" without seeing which address the server looked at has to guess what to change. The e2e module covers the wildcard bind on the real binary, because every other test there binds `127.0.0.1` and would stay green while this hole reopened.
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📝 WalkthroughWalkthroughThe HTTP server now refuses ChangesHost-local escape hatch enforcement
Priority: ⬆️ High Estimated code review effort: 3 (Moderate) | ~20 minutes Severity of issue fixed: High Merge Risk: 🟡 Moderate · up to The new listener restriction can be bypassed when localhost resolves to a reachable interface, potentially exposing the unrestricted GitLab URL path as an SSRF proxy. Resolve this before merge by requiring literal loopback addresses or validating the bound listener address. Sequence Diagram(s)sequenceDiagram
participant HTTPConfig
participant requireInstanceAllowList
participant listenerIsHostLocal
participant ServerStartup
HTTPConfig->>requireInstanceAllowList: provide --allow-any-gitlab-url and --http-addr
requireInstanceAllowList->>listenerIsHostLocal: classify listener address
listenerIsHostLocal-->>requireInstanceAllowList: host-local or reachable
requireInstanceAllowList->>ServerStartup: return startup error or allow startup
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Description checkExplanation The description clearly explains the security issue, startup restriction, affected addresses, documentation changes, and regression test. However, it does not follow the required template and omits the Related Issue, Type of Change, Changes Made, How to Test, Breaking Changes / Migration Notes, Checklist, and Screenshots / Logs sections. Resolution Add the required template sections. Provide an issue reference or state why none applies, select the change type, list the key changes, add reproducible test steps and test results, state migration notes as N/A if applicable, complete the code quality, testing, documentation, and security checklist items, and include logs or state that they are not applicable.
✨ Finishing Touches 💡 1🛠️ Fix failing CI checks 💡
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🧪 Generate unit tests (beta)
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Inline comments:
In `@cmd/server/main.go`:
- Line 967: Update listenerIsHostLocal and its isLoopbackHost validation to
reject the hostname “localhost” and accept only literal loopback IP addresses,
or validate the bound listener’s resolved address before serving; preserve
unrestricted-listener behavior only for addresses confirmed as loopback.
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📒 Files selected for processing (12)
CLAUDE.mdREADME.mdSECURITY.mdcmd/server/main.gocmd/server/main_test.godocs/guides/http-server-mode.mddocs/reference/cli.mddocs/reference/configuration.mdsite/src/content/docs/es/configuration.mdxsite/src/content/docs/es/install/docker.mdxsite/src/content/docs/operations/http-server.mdxtest/e2e/http/gate_test.go
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`localhost` is loopback by convention and not by rule. A host whose /etc/hosts maps it to a routable interface binds there, so accepting the name would open the request-forgery proxy this precondition exists to keep shut, on a listener anyone on the network can reach, under a spelling that reads local. A literal is already the answer and is judged as one. A name is resolved, every address it resolves to has to be loopback, and a name that resolves to none is refused: this decides whether to serve a caller's chosen host with that caller's token, so not knowing is a no. net.Listen resolves the same string a moment later, which is what makes this the question the bind will answer rather than a second opinion about it. The resolver is a variable so the test can answer for a name without depending on the machine's /etc/hosts, which is the only way to pin the case that matters: a name resolving off the machine. Reported by CodeRabbit on the pull request.
The SSE helper returned the first data frame of the stream and every caller then asserted a substring on it. The stream is shared with whatever else the server has to say, so which message arrives first is a race no test can win. It lost on a macOS runner. A listen that had been granted was read as one that had been refused, because notifications/resources/list_changed reached the frame first and the acknowledgement came second, and the assertion that fired says "the refused listen left watchers behind" about a server that had done nothing wrong. That is the worst shape a flake can take: it names a real invariant and accuses the product of breaking it. The helper now takes what the caller is waiting for and returns the first frame carrying it, so the race disappears rather than being retried. It still never reads to EOF, since a listen holds its stream open for the life of the subscription. When the frame never comes, the failure prints every message the stream did send, which is the diagnosis. Two of the three call sites were only latently affected; the fix is at the helper because all three ask the same kind of question.
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--allow-any-gitlab-urlpublishes no instance and lets theGITLAB-URLheader name any host. That is the request forgery this repository's HTTP mode was refused permission to do by default, opted into deliberately: the server makes the request, with whatever token the caller supplied, and hands the response back to them.It is defensible in exactly one shape, the single-user local deployment where the caller can only be the operator. The flag said so, in a warning that read "do not run this on a listener anyone else can reach", and then started anyway. On a wildcard bind, which is what the container
CMDdoes, the hatch was an SSRF proxy for the whole network.So the sentence is now a precondition.
--http-addrmust bind a loopback address or a unix socket for the hatch to be accepted; anything else is refused at startup, naming the address it judged. A socket qualifies for a stronger reason than a port does: it resolves to a file rather than a name, so no remote peer can reach it at all, and--http-socket-modedecides which local principals may.One case is refused that is host-local in fact: a container binding
0.0.0.0and published with-p 127.0.0.1:8080:8080. Nothing inside the process distinguishes it from the same container published on every interface, and I would rather refuse that than accept the wildcard bind for everyone. Such a deployment names its instance, which is what every other container deployment in the docs already does.Two documentation examples were already broken and are corrected here. The built-in help offered
--allow-any-gitlab-url --http-addr=:8080, which this change stops accepting. The TLS section of the HTTP guide showed a command with no--gitlab-urlat all, which has not started since the instance allow-list landed.The regression lives in the e2e module rather than only in the unit test, because the address the binary judges is the one it parsed off its own command line, and every other test in that module binds
127.0.0.1and would stay green while this hole reopened.