docs: self-signed certificate / internal CA handling for GitHub Enterprise#1050
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…Hub Enterprise Adds an advanced-usage section explaining the 'self signed certificate in certificate chain' error seen on GitHub Enterprise Server and behind TLS-inspecting proxies. Recommends the secure fix of trusting the internal CA via NODE_EXTRA_CA_CERTS (or the OS trust store on self-hosted runners), with a GitHub Enterprise callout, and warns against disabling TLS verification since the JDK download has no checksum fallback. Refs #640 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Adds documentation to help GitHub Enterprise Server (GHES) and corporate-proxy users resolve self signed certificate in certificate chain errors safely when actions/setup-java downloads JDK metadata/archives, steering users toward trusting the internal CA instead of disabling TLS verification.
Changes:
- Adds a new “Self-signed certificates and internal CAs (GitHub Enterprise)” section explaining cause, secure remediation, and security implications.
- Adds two workflow YAML examples showing how to provide an internal CA bundle via
NODE_EXTRA_CA_CERTS. - Adds a matching table-of-contents entry.
Show a summary per file
| File | Description |
|---|---|
| docs/advanced-usage.md | Adds GHES/internal-CA guidance and examples for resolving self-signed certificate chain errors securely. |
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- Files reviewed: 1/1 changed files
- Comments generated: 2
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| - name: Trust the internal CA | ||
| run: echo "NODE_EXTRA_CA_CERTS=/etc/ssl/certs/internal-ca.pem" >> "$GITHUB_ENV" | ||
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| - uses: actions/setup-java@v5 | ||
| with: |
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| - name: Write and trust the internal CA | ||
| run: | | ||
| echo "${{ secrets.INTERNAL_CA_PEM }}" > "${RUNNER_TEMP}/internal-ca.pem" | ||
| echo "NODE_EXTRA_CA_CERTS=${RUNNER_TEMP}/internal-ca.pem" >> "$GITHUB_ENV" | ||
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| - uses: actions/setup-java@v5 |
This was referenced Jun 23, 2026
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What
Adds a new "Self-signed certificates and internal CAs (GitHub Enterprise)" section to
docs/advanced-usage.md.Why
Users on GitHub Enterprise Server, or behind a TLS-inspecting corporate proxy, hit
Error: self signed certificate in certificate chainwhensetup-javadownloads JDK metadata and archives. There was no documentation explaining the cause or the secure way to resolve it, which leads people toward unsafe workarounds like disabling TLS verification.What the new section covers
self signed certificate in certificate chain) and its root cause: an internal/self-signed CA not present in the runner's trust store.NODE_EXTRA_CA_CERTS(Node honors it, and so do@actions/http-clientand@actions/tool-cache), with two YAML examples — CA already on the runner, and CA written from a secret.NODE_TLS_REJECT_UNAUTHORIZED=0): the JDK download has no checksum/signature fallback, so TLS is the only integrity guarantee and disabling it opens a MITM / supply-chain path.Also adds a matching table-of-contents entry.
Notes
dist/changes.prettier --checkpasses on the edited file.Refs #640