fix: reliable GitLab commit verification when the CLI runs through Dagger

[javirln]

Summary

Makes GitLab commit author verification work when the CLI runs through the Chainloop Dagger module on a self-managed GitLab server.

• Deterministic runner discovery. Runners are discovered in a fixed order, with the Dagger runner first. The Dagger module passes the parent GitLab CI context to the CLI container, so the Dagger and GitLab runners both matched, and the selected runner changed from run to run (since fix: return early in DiscoverRunner on first match #2871). When the GitLab runner was selected, attestation init failed on missing GitLab variables.
• GitLab API token. Commit verification sends GITLAB_TOKEN (read_api scope) as PRIVATE-TOKEN. The GitLab commit signature API does not accept job tokens, so commits of private and internal projects could not be verified.
• Correct 404 handling. Only a 404 Signature Not Found response marks a commit as unsigned. 404 Project Not Found and 404 Commit Not Found now give an unavailable status with the GitLab message, instead of "Commit is not signed".
• GitLab-signed commits. Signatures with the verified_system status, which GitLab creates for web UI and merge commits, are reported as verified.
• Signature algorithm. The signature.algorithm annotation of the git head subject falls back to the type of the commit signature when the platform does not report it.
• Visible failure reason. The reason of an unavailable verification is logged as a warning.
• Dagger module options. init accepts --gitlab-token, and --gitlab-ca for self-managed GitLab servers that use a certificate from a private CA.
• CLI image. The scratch-based CLI image now has a writable /tmp, which the PR/MR metadata collector needs.

Refs PFM-7635

AI disclosure

This change was developed with assistance from Claude Code.

[chainloop-platform]

PR validation — ✅ 3 passing

Status	Policy	Material	Messages
✅ Passed	pr-min-approvals	pr-info	-
✅ Passed	pr-description-required	pr-info	-
✅ Passed	pr-user-story-linked	pr-info	-

_{View attestation ↗}

AI Session Checks — 🟢 90% · ✅ 0 failing

Avg score	Sessions	Failing policies	Attribution	Files	Lines	Total Duration
🟢 90%	1	✅ 0	100% AI / 0% Human	15	+629 / -33	5h54m38s

🟢 90% — 100% AI — ✅ All policies passing

Oct 7, 2026 14:09 UTC · 5h54m38s · $81.65 · 1.1k in / 723.6k out · claude-code 2.1.292 (claude-opus-5-5)

_{View session details ↗}

Change Summary

• Makes runner discovery deterministic for Dagger and GitLab overlap and improves GitLab commit verification handling.
• Adds renderer fallback for signature.algorithm, Dagger GitLab token/CA options, and a writable /tmp in the CLI image.
• Covers the changes with new unit tests, golden updates, and a local end-to-end repro.

AI Session Overall Score

🟢 90% — Verified root-cause fix, with only planning weaker than the task breadth.

AI Session Analysis Breakdown

🟢 95% · solution-quality

🟢 The AI used probes and mutation checks instead of masking the bug. · High Impact

🟢 94% · verification

🟢 The AI added failing tests for the core fixes and reran them green. · High Impact

🟢 92% · alignment

No notes.

🟢 88% · scope-discipline

🟢 The later platform /tmp fix was split into a separate PR. · High Impact

🟢 88% · user-trust-signal

No notes.

🟡 72% · context-and-planning

🟠 The session tackled a broad multi-file fix without a visible plan or TODO. · Medium Severity

💡 Before editing across repo layers, write a short plan naming files, risks, and checks.

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File Attribution

████████████████████ 100% AI / 0% Human

Status	Attribution	File	Lines
created	ai	pkg/attestation/crafter/runners/commitverification/gitlab_test.go	+210 / -0
created	ai	pkg/attestation/crafter/runner_test.go	+158 / -0
modified	ai	pkg/attestation/crafter/runners/commitverification/gitlab.go	+77 / -7
modified	ai	pkg/attestation/renderer/chainloop/v02_test.go	+69 / -0
modified	ai	pkg/attestation/crafter/runner.go	+31 / -3
modified	ai	extras/dagger/main.go	+25 / -2
modified	ai	extras/dagger/README.md	+21 / -0
modified	ai	pkg/attestation/renderer/chainloop/v02.go	+11 / -3
modified	ai	pkg/attestation/crafter/runners/daggerpipeline.go	+5 / -5
modified	ai	pkg/attestation/crafter/runners/gitlabpipeline.go	+5 / -5
modified	ai	pkg/attestation/crafter/crafter.go	+7 / -2
modified	ai	pkg/attestation/crafter/runners/commitverification/github.go	+3 / -3
modified	ai	app/cli/Dockerfile.goreleaser	+3 / -1
modified	ai	pkg/attestation/renderer/chainloop/testdata/attestation.output-2.v0.2.json	+2 / -1
modified	ai	pkg/attestation/renderer/chainloop/testdata/attestation.output-2.v2.json	+2 / -1

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Policies (4)

Status	Policy	Material	Messages
✅ Passed	ai-config-ai-agents-allowed	ai-coding-session-38d0eb	-
✅ Passed	ai-config-no-dangerous-commands	ai-coding-session-38d0eb	-
✅ Passed	ai-config-no-secrets	ai-coding-session-38d0eb	-
✅ Passed	ai-config-mcp-servers-allowed	ai-coding-session-38d0eb	-

Security Checks — ✅ 6 passing

✅ secret-scan

Status	Policy	Messages
✅ Passed	secrets-detection	-

✅ sast-scan

Status	Policy	Messages
✅ Passed	owasp-top10-2025	-
✅ Passed	sast	-
✅ Passed	cwe-top25	-
✅ Passed	cwe-top26-40-cusp	-

✅ iac-scan

Status	Policy	Messages
✅ Passed	iac-misconfiguration	-

Scans not applied (2)

Scan	Reason
vulnerability-scan	no manifest/lockfile changed
github-actions-scan	no workflow files changed

_{View attestation ↗}

Security context

This change touches code with 4 recorded security-fix advisories. These are pointers to what past fixes established, not findings in this diff, and they never fail the check.

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