ci: add semgrep scan on PRs to main

[neeythann]

Adds a GitHub Actions workflow that runs a free/OSS Semgrep scan (no Semgrep AppSec Platform token required) on every pull request targeting main, including re-runs when new commits are pushed to an open PR.

• Runs in the official semgrep/semgrep container, so no install step
• semgrep scan --config p/golang --config p/secrets --error — Go ruleset + secrets detection, fails the job on findings

Summary by CodeRabbit

• Chores
  • Added automated security scanning for pull requests targeting the main branch.
  • Scans now check Go code and potential secrets, reporting detected issues as workflow errors.

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e5e5c509-83ac-4c00-868b-d8ff0b7aa417

📥 Commits

Reviewing files that changed from the base of the PR and between 23df795 and f2b6d37.

📒 Files selected for processing (2)

• .github/workflows/semgrep.yml
• pkg/deploy/hostname.go

📝 Walkthrough

Walkthrough

Adds a GitHub Actions workflow that runs Semgrep in a container for pull requests targeting main, scanning with Go and secrets rules and failing on detected errors.

Changes

Semgrep CI workflow

Layer / File(s)	Summary
Configure Semgrep pull request scanning .github/workflows/semgrep.yml	Triggers on pull requests to main, grants read-only contents access, checks out the repository, and runs Semgrep with p/golang, p/secrets, and --error.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the new CI workflow that runs Semgrep scans on pull requests targeting main.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/semgrep-pr-scan

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (2)

.github/workflows/semgrep.yml (2)

15-25: 🩺 Stability & Availability | 🔵 Trivial | ⚡ Quick win

Consider adding a job/step timeout.

No timeout-minutes is set, so a hung Semgrep scan could block the job indefinitely and consume runner minutes.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/workflows/semgrep.yml around lines 15 - 25, Add a finite
timeout-minutes setting to the semgrep job containing the “Run Semgrep” step,
using a value appropriate for the scan so hung executions terminate and do not
run indefinitely.

---

21-22: 🔒 Security & Privacy | 🔵 Trivial | ⚡ Quick win

Disable credential persistence on checkout.

actions/checkout@v4 persists the GitHub token in the local git config by default (flagged by zizmor as artipacked), which is unnecessary here since the job only needs to read the code for scanning.

🔒️ Proposed fix

       - name: Checkout
         uses: actions/checkout@v4
+        with:
+          persist-credentials: false

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/workflows/semgrep.yml around lines 21 - 22, Update the
actions/checkout@v4 step in the workflow to disable credential persistence by
configuring persist-credentials as false, while leaving the checkout behavior
unchanged for the scanning job.

Source: Linters/SAST tools

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In @.github/workflows/semgrep.yml:
- Around line 18-19: Pin the container image used by the workflow to a specific
Semgrep version tag or immutable digest instead of the floating semgrep/semgrep
latest image. Update the container configuration while preserving the existing
Semgrep workflow behavior.

---

Nitpick comments:
In @.github/workflows/semgrep.yml:
- Around line 15-25: Add a finite timeout-minutes setting to the semgrep job
containing the “Run Semgrep” step, using a value appropriate for the scan so
hung executions terminate and do not run indefinitely.
- Around line 21-22: Update the actions/checkout@v4 step in the workflow to
disable credential persistence by configuring persist-credentials as false,
while leaving the checkout behavior unchanged for the scanning job.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: cd5f7e46-bf37-4377-99f4-c6cde3e2f1c9

📥 Commits

Reviewing files that changed from the base of the PR and between c588761 and 23df795.

📒 Files selected for processing (1)

• .github/workflows/semgrep.yml