Docker credential helper: emit not-found error on stdout#2059
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The docker credential-helper protocol requires the "credentials not found in native keychain" sentinel on stdout; clients (docker/podman) match it there to recognise "no stored credential". Writing it to stderr left stdout empty, so podman treated the exit 1 as a fatal "error getting credentials" and aborted login on podman workers using the credential helper. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
matt-richardson
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APErebus
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Jul 3, 2026
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Summary
The
docker-credential-octopus(the credential helper added in #1981) wrote its"credentials not found in native keychain" error message to stderr.
The docker credential-helper protocol actually requires it on stdout - clients such as
podman match that exact string to recognise the "no stored credential yet" case.
When using podman (via the
podman-dockershim), podman probes the helperwith
getatlogintime. With the error message on stderr & stdout empty,podman treated the exit-1 as a fatal error.
Relates to OctopusDeploy/Issues#10128.
Results
This PR moves the error message to stdout, matching the reference
docker-credential-helpersServebehaviour.Testing: this has been verified to work on podman 4.9.3, but AFAICT, requires podman 4.x (based on the v4.0.0 tag referenced here). This does not work on podman 3.4.4 (the version referenced in the issue above).
Server change
No — helper output stream only, no server-side change required.