SysAdmin
4444dc11f3
Vendors Kicksecure derivative-maker as a pinned submodule (18.1.7.4), adds the wrapper + verify + diagnose scripts, the pinned builder image, and the reproducibility-gated Gitea Actions workflow. Base flavour only — no hardening overlay (that's M1.2). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
117 lines
5.4 KiB
Markdown
117 lines
5.4 KiB
Markdown
# SilverMetal Linux — reproducible ISO build pipeline
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**Milestone**: Phase 1 / M1.1 — *Kicksecure fork builds reproducibly*.
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**Exit criterion**: two clean builds of the same commit produce a byte-identical SHA256.
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This directory holds everything that turns a SilverMetal commit into a SilverMetal Linux ISO. M1.1 ships only the *base* (un-hardened) Kicksecure derivative. Hardening overlay, kernel swap, AppArmor profiles, etc. land in M1.2+ and **must not** be added here in the M1.1 PR.
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## Layout
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```
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linux/build/
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├── README.md (this file)
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├── derivative-maker/ git submodule -> Kicksecure/derivative-maker
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├── config/
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│ ├── silvermetal-base.conf derivative selection + branding
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│ ├── snapshot-pin.env pinned snapshot.debian.org timestamp
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│ └── source-date-epoch.env optional SOURCE_DATE_EPOCH override
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├── docker/
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│ └── Dockerfile.builder pinned debian:bookworm-slim builder image
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└── scripts/
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├── build.sh wrapper: container run -> derivative-maker
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├── verify-reproducibility.sh build twice, compare SHA256
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└── diagnose-divergence.sh diffoscope on mismatch
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```
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## How reproducibility is achieved
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The same levers any deterministic Debian build relies on, stacked together:
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| Lever | Where it lives |
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|----------------------------------------|-----------------------------------------------|
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| Pinned `snapshot.debian.org` mirror | `config/snapshot-pin.env` |
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| `SOURCE_DATE_EPOCH` from commit time | `scripts/build.sh` (auto) |
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| Pinned builder image (by digest) | `docker/Dockerfile.builder` + `BUILDER_IMAGE` |
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| Deterministic `mksquashfs` flags | `MKSQUASHFS_OPTIONS` in base conf |
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| Pinned upstream toolchain | `derivative-maker/` submodule |
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| `LC_ALL=C.UTF-8`, `TZ=UTC` | `scripts/build.sh` |
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`diffoscope` is the *diagnostic* tool used by `diagnose-divergence.sh`; the gate itself is plain `sha256sum`.
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## Reproduce a release locally
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> Procedure mirrors `docs/trust-model.md` § *Reproducible builds*.
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Prerequisites: a Linux host (or WSL2) with Docker, ~30 GB free disk, ~8 GB RAM.
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```bash
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# 1. Clone the repo at the release tag.
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git clone --recurse-submodules https://git.silverlabs.uk/SilverLABS/SilverMetal.git
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cd SilverMetal
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git checkout v1.1.0 # whichever release you want to verify
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# 2. Build twice and compare. ~60-90 minutes per build.
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linux/build/scripts/verify-reproducibility.sh
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# 3. Compare against the published release.
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sha256sum -c <(curl -fsSL https://git.silverlabs.uk/SilverLABS/SilverMetal/releases/download/v1.1.0/SHA256SUMS)
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```
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Mismatch with the published artefact = supply-chain anomaly. Report channel: `security@silverlabs.uk`.
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## Build once (no reproducibility check)
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```bash
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linux/build/scripts/build.sh
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# Output lands in linux/build/output/<short-sha>/
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```
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The wrapper requires `BUILDER_IMAGE` to be pinned by digest. Local dev that hasn't built and pushed an image yet should override:
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```bash
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BUILDER_IMAGE=docker-registry:5000/silvermetal-builder@sha256:<digest> \
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linux/build/scripts/build.sh
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```
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## Gitea Actions
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The CI workflow (`.gitea/workflows/build-iso-linux.yaml`) is the authority for "did this commit build reproducibly?". It:
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1. Checks out the commit with submodules.
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2. Runs `build.sh` twice in `${GITHUB_WORKSPACE}/build-{a,b}`.
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3. Fails the run if the two ISO SHA256s differ, and uploads a `diffoscope` report as an artefact.
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4. On a tag push, attaches the verified ISO + `SHA256SUMS` + `BUILD_INFO` to a Gitea release.
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### Self-hosted runner setup
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The workflow runs on `runs-on: silvermetal-builder`, a self-hosted, privileged-capable Gitea Actions runner. Create it before merging the workflow:
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1. Provision a Debian 12 VM on the cluster with ≥ 8 vCPU, ≥ 16 GB RAM, ≥ 100 GB disk.
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2. Install Docker (`apt install docker.io`); ensure the runner user can run `docker run --privileged`.
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3. Register `act_runner` against `git.silverlabs.uk` with label `silvermetal-builder`.
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4. Pre-pull the builder image so the first reproducibility run isn't a cold start:
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`docker pull docker-registry:5000/silvermetal-builder:latest`
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5. Cache the apt snapshot in a Docker volume to avoid throttling:
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`docker volume create silvermetal-apt-cache`
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The runner host name **must not** leak into ISO content. `LC_ALL=C.UTF-8` and a constant `TZ` in the wrapper guard against that, but spot-check with `diagnose-divergence.sh`.
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## Bumping pinned inputs
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Each of these is a deliberate, reviewed action — never automate:
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- **`derivative-maker` submodule** — bump in its own PR, with a verification log showing two clean builds match.
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- **`snapshot-pin.env`** — same procedure.
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- **Builder image (`Dockerfile.builder` digest)** — rebuild, push, update `BUILDER_IMAGE` in `build.sh`, run reproducibility check, commit all four together.
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## What this milestone is *not*
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- No hardening overlay (M1.2)
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- No SilverBrowser/SilverVPN/SilverSync/SilverChat integration (M1.6–1.9)
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- No installer branding (M1.5)
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- No update server (M1.10)
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- No SBOM publication (M1.11)
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- No signing ceremony / MOK / Secure Boot wiring (separate milestone)
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If a change to this directory expands its scope into one of those, push back — the M1.1 gate is intentionally narrow.
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