Let’s go through this from a security architecture perspective, and identify:

Potential risks

Mitigation strategies

Recommendations specific to Guix in air-gapped, classified use

🛡️ Security Risks in an Air-Gapped Guix Workflow
1. Supply Chain Attacks via Source Code
Even though you're building from source, the upstream source code (tarballs, Git repos) may be maliciously modified.

Guix uses cryptographic hash verification, but only against what is declared in the Guix package definition — not against independent trust anchors.

✅ Mitigations:

Use guix build --source with hash-locked package definitions (content-addressed derivations).

Use reproducible builds and determinism checks (e.g., compare build outputs across trusted builders).

Consider maintaining a private mirror of trusted source code, and pin hash checks yourself.

Use content scanning tools (e.g., static analyzers) on all .tar.gz and Git checkouts.

2. Compromise via Channel Updates
Your Guix package definitions come from Git channels (e.g., guix.git, or your own).

If your channel is compromised, malicious package definitions could be delivered.

✅ Mitigations:

Use a pinned commit hash in your channels.scm.

Verify the channel commit with signed Git commits or tags (Guix supports this).

Host your own internal Guix channel for critical environments — control what definitions are trusted.

Use guix time-machine to avoid rolling updates.

3. Media Transfer Risks (USB, SD cards)
USB drives used for transferring .nar files or source archives can be a vector for malware, even in an air-gapped setup.

✅ Mitigations:

Always format and scan USB media on a controlled, known-clean staging machine before inserting into classified systems.

Use write-once optical media (DVD-R) where appropriate for immutable transfer.

Prefer hash verification of transferred files (sha256sum sources.nar) using offline-known-good hashes.

4. Build Environment Leakage
If the build process writes temporary files or outputs data to places outside the Guix store, secrets or traces of sensitive data could leak or persist.

✅ Mitigations:

Use guix build inside a dedicated, minimal, reproducible system (e.g., a guix system vm).

Enable build sandboxing (enabled by default in Guix).

Disable networking in builders if not already (Guix does this by default, but confirm your configuration).

Consider full-disk encryption for the build system.

5. Tampered Nar Archives
.nar archives imported into your air-gapped server could be tampered with in transit.

✅ Mitigations:

Sign the archive on the export side and verify the signature on the import side.

Use GPG or minisign for signing hashes.

Maintain a hash whitelist of approved .nar files on the classified system.

Store all .nar imports in a sealed append-only log for auditing.

✅ High-Security Recommendations for Guix in Classified Environments

Concern	Recommendation
Source authenticity	Use fixed-output derivations with pinned hashes
Package definition trust	Host internal Guix channel; pin commit hashes
Archive integrity	Sign .nar files and verify signatures
Reproducibility	Use multiple offline builders to cross-check outputs
Logging	Keep an audit trail of all imports and builds
Isolation	Build in virtual machines or system containers with no network
Transfer media	Sanitize USBs or use write-once optical media
User separation	Separate users for import, build, audit, and deployment tasks
🔐 Final Thoughts
Guix offers an excellent foundation for secure, reproducible software environments.

But air-gapped security is about the whole process, not just the tooling.

You should treat the Guix channel, source transport, build environment, and auditability as a single trusted pipeline.