Harden the lint-guard shell scanner against silent evasions (closes #121)

The guard test's shell scanner was weaker than its commit message
claimed. Two holes are closed.

shellCode now treats `<<` as a here-document only when it is a real
redirection: outside single and double quotes, not past an unquoted
word-initial `#` that begins an inline comment, and followed by a
delimiter word. A `<<` inside a quoted string or an inline comment no
longer opens a phantom here-document that swallows the rest of the
file -- including the silent case where the fake terminator recurs
later as a line of its own -- and a here-document still open at end of
file is a loud error rather than a silent truncation.

assertLinterIsContainerised now cuts the joined line into the simple
commands the shell would run -- on `;`, `&&`, `||` and `|` -- and
requires the command that names the linter to begin with docker. So
`docker info; golangci-lint run` and `docker info || golangci-lint run`
are rejected, while script/lint-fix's `docker run ... golangci-lint`
still passes.

The scanner comment now names the inline-comment exception alongside
the quoted-string and arithmetic ones, and the inherent limits of a
text scan. Dockerfile.lint's citation is corrected from `lll` to
`revive`, the finding the recorded evidence actually named.

model: claude-opus-4-8

.gitea/workflows/check.yml

@@ -1,9 +1,9 @@
 name: check
 on:
   push:
-    branches: [main]
+    branches: [main, next]
   pull_request:
-    branches: [main]
+    branches: [main, next]
 jobs:
   check:
     runs-on: ubuntu-latest

ARCHITECTURE.md

@@ -366,11 +366,17 @@ bucket/
 │           └── {full-hash}          # Compressed+encrypted blob
 │
 └── metadata/
-    └── {snapshot-id}/
+    └── {remote-key}/
         ├── db.zst.age               # Encrypted binary SQLite database
         └── manifest.json.zst        # Blob list (for pruning/verification)
 ```
 
+The `{remote-key}` directory name is a one-way double SHA-256 hash of the human
+snapshot ID, so the human ID (hostname, snapshot name, timestamp) is never
+written to the store as a directory name. See
+[docs/REPOSTRUCTURE.md](docs/REPOSTRUCTURE.md#remote-key-derivation) for the
+derivation and a worked example.
+
 ## Thread Safety
 
 - `Packer`: Thread-safe via mutex. Multiple goroutines can call `AddChunk()`.

Dockerfile

@@ -1,23 +1,29 @@
-# Lint stage
+# This file has no lint stage, deliberately.
 #
-# This FROM line is the single source of truth for the linter version:
+# Linting lives in Dockerfile.lint, built by script/lint, and
-# script/lint parses the image reference out of it and runs that exact
+# script/cibuild builds both. A lint stage here would have to either
-# image, so a local `make lint` and CI use the same linter. Bump the
+# shell out to `make lint` -- which is now `docker build`, so
-# linter here (tag AND digest) and nowhere else.
+# docker-in-docker inside a BuildKit step with no daemon -- or call
+# golangci-lint directly, which would mean a second, independently
+# bumpable digest pin for the linter alongside the one in
+# Dockerfile.lint. Two pins for one tool is the drift that
+# https://git.eeqj.de/sneak/vaultik/issues/78 was filed over. See
+# https://git.eeqj.de/sneak/vaultik/issues/113 for the ruling.
 #
-# golangci/golangci-lint:v2.12.2-alpine, 2026-08-07
+# Consequence, stated rather than left to be discovered: script/docker
-FROM golangci/golangci-lint:v2.12.2-alpine@sha256:91b27804074a0bacea298707f016911e60cf0cdbc6c7bf5ccacb5f0606d18d60 AS lint
+# builds this file only and therefore does not lint. `make fmt-check`
+# and `make test` still run here, so what a green build of this file
+# means is "formatted, tested, and it compiles" -- the lint verdict
+# comes from script/lint or script/cibuild.
 
-RUN apk add --no-cache make build-base
+# Build stage
+# golang:1.26.1-alpine, 2026-03-17
+FROM golang:1.26.1-alpine@sha256:2389ebfa5b7f43eeafbd6be0c3700cc46690ef842ad962f6c5bd6be49ed82039 AS builder
 
-# The context signal for script/lint's native path. This stage runs
+ARG VERSION=dev
-# `make lint` with no docker daemon available, so it is the one place
+
-# that must run the golangci-lint on PATH directly. script/lint takes
+# Install build dependencies for CGO (mattn/go-sqlite3) and sqlite3 CLI (tests)
-# that path only when this is set AND the version matches the pin above;
+RUN apk add --no-cache make build-base sqlite
-# version equality alone would also admit a developer's locally
-# installed copy on a host, bypassing the digest pin (issue #80).
-# Nothing outside this stage sets it.
-ENV VAULTIK_LINT_IN_CONTAINER=1
 
 WORKDIR /src
 
@@ -28,7 +34,7 @@ RUN go mod download
 # Copy source code
 COPY . .
 
-# Run formatting check and linter.
+# Run the format check and the tests.
 #
 # CHECK_EPOCH must stay immediately above these RUNs. These layers are
 # keyed on its value, so they are cache-eligible only for a value
@@ -47,45 +53,15 @@ COPY . .
 # runs the checks and every one after it on an unchanged tree replays
 # these layers from cache, executes nothing, and still exits 0. Failed
 # steps are never cached, so the guard fails on EVERY invocation rather
-# than once -- a bare `docker build .` is now a loud error, not a quiet
+# than once -- a bare `docker build .` is a loud error, not a quiet
 # green. Do not give CHECK_EPOCH a default value; a default would
 # satisfy the guard with a constant and restore the hole.
 #
-# ARG scope is per-stage, so the builder stage declares its own.
 # Everything above this line (apk, go.mod, `go mod download`) is
 # deliberately outside the busted range and keeps caching.
 ARG CHECK_EPOCH
 RUN [ -n "$CHECK_EPOCH" ] || exit 1
 RUN echo "check epoch: ${CHECK_EPOCH}" && make fmt-check
-RUN echo "check epoch: ${CHECK_EPOCH}" && make lint
-
-# Build stage
-# golang:1.26.1-alpine, 2026-03-17
-FROM golang:1.26.1-alpine@sha256:2389ebfa5b7f43eeafbd6be0c3700cc46690ef842ad962f6c5bd6be49ed82039 AS builder
-
-# Depend on lint stage passing
-COPY --from=lint /src/go.sum /dev/null
-
-ARG VERSION=dev
-
-# Install build dependencies for CGO (mattn/go-sqlite3) and sqlite3 CLI (tests)
-RUN apk add --no-cache make build-base sqlite
-
-WORKDIR /src
-
-# Copy go mod files first for better layer caching
-COPY go.mod go.sum ./
-RUN go mod download
-
-# Copy source code
-COPY . .
-
-# Run tests. See the CHECK_EPOCH comment in the lint stage for the
-# mechanism; ARG scope is per-stage, so this stage needs its own
-# declaration, its own guard, and its own expansion, and they must stay
-# immediately above the check RUN.
-ARG CHECK_EPOCH
-RUN [ -n "$CHECK_EPOCH" ] || exit 1
 RUN echo "check epoch: ${CHECK_EPOCH}" && make test
 
 # Build (pure Go, no CGO required since we use modernc.org/sqlite)

Dockerfile.lint

@@ -0,0 +1,104 @@
+# Lint image.
+#
+# Every lint run in this repo happens inside this image, invoked through
+# script/lint, and linting is a BUILD STEP rather than a container
+# command: a successful build of this file IS a clean lint. That shape
+# also works where the docker daemon is remote and bind mounts are
+# impossible, which `docker run` against a mounted worktree does not.
+#
+# This FROM line is the single source of truth for the linter version in
+# this repo. Nothing else pins golangci-lint: the product Dockerfile has
+# no lint stage, deliberately, so there is no second digest to bump and
+# no pair of pins that can drift apart. Bump the tag AND the digest here
+# and nowhere else.
+#
+# Note for readers coming from REPO_POLICIES.md: that document still
+# describes the older pattern, a lint stage inside the product
+# Dockerfile wired up with `COPY --from=lint /src/go.sum /dev/null`.
+# That pattern is superseded here by the owner's ruling recorded in
+# https://git.eeqj.de/sneak/vaultik/issues/113 -- lint runs in its own
+# image, per run, with its own cache and its own lock, which is what
+# makes concurrent runs on one host safe. The policy text is org-wide
+# and is being amended separately; this file is what this repo does.
+#
+# golangci/golangci-lint:v2.12.2, 2026-08-10
+FROM golangci/golangci-lint:v2.12.2@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240
+
+WORKDIR /src
+
+# Copy the dependency manifests first so the module download layer stays
+# cached until they change. Everything above the ARG below is cacheable
+# on purpose; a cold module download on every lint would make the inner
+# loop unusable and buys nothing, because it is not what the gate is
+# asserting.
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+# Force the check layers to execute on every invocation.
+#
+# CHECK_EPOCH must stay immediately above the RUNs below. Those layers
+# are keyed on its value, so they are cache-eligible only for a value
+# already built against this same tree; script/lint and script/cibuild
+# each pass a fresh value on every invocation, which is what makes their
+# green mean the linter really ran. Without it, `docker build -f
+# Dockerfile.lint .` on an unchanged tree exits 0 in well under a second
+# having linted nothing.
+#
+# The value is expanded into each check command itself rather than left
+# to a bare declaration, so the cache miss does not depend on BuildKit's
+# unreferenced-ARG handling staying as it is. It also puts the epoch in
+# the build log, where a reader can see the layer was keyed fresh.
+#
+# The guard is what makes a build that omits --build-arg fail instead of
+# lie. An unset ARG is an empty string, and an empty string is a
+# perfectly stable cache key: without the guard the first such build
+# lints and every one after it on an unchanged tree replays this layer,
+# executes nothing, and still exits 0. Failed steps are never cached, so
+# the guard fails on EVERY invocation rather than once. Do not give
+# CHECK_EPOCH a default value; a default would satisfy the guard with a
+# constant and restore the hole.
+ARG CHECK_EPOCH
+RUN [ -n "$CHECK_EPOCH" ] || exit 1
+
+# Validate .golangci.yml before linting with it.
+#
+# This is not belt-and-braces; it closes a hole that `golangci-lint run`
+# leaves wide open. `run` rejects YAML it cannot PARSE, but it silently
+# IGNORES an unknown top-level KEY. Renaming `linters:` to `linterz:` --
+# one character -- discards `default: all`, the whole disable list and
+# every threshold, leaves only golangci-lint's small default linter set
+# running, and exits 0 reporting `0 issues.` on a tree the real config
+# fails. Demonstrated on this repo at this pin, recorded on
+# https://git.eeqj.de/sneak/vaultik/pulls/114: with a planted
+# over-length line, `script/lint` exits 1 naming the `revive` finding
+# with `linters:` and exits 0 with `linterz:`. A set-but-ineffective
+# config quietly falling back to defaults is precisely the false-green
+# class this gate exists to eliminate, so it must not sit in the gate's
+# own configuration.
+#
+# `config verify` catches it, and it does so OFFLINE at this pinned
+# version -- verified, not assumed. Under `docker run --network none`
+# against the pinned digest it exits 0 on this repo's config and exits 3
+# on the `linterz:` variant with `additional properties 'linterz' not
+# allowed`. An earlier revision of this file asserted the opposite, that
+# the schema is fetched over live HTTPS from an unpinned URL, and used
+# that to justify omitting this line. That claim was false at v2.12.2;
+# the schema is embedded. If a future bump reintroduces a network fetch
+# the failure is loud and this comment is where to record it.
+#
+# It is keyed on CHECK_EPOCH, like the lint run below, so it executes on
+# every invocation. Content-addressing alone would arguably be enough --
+# .golangci.yml arrives through `COPY . .`, so a cache hit here implies
+# a byte-identical config was validated when the layer really ran. That
+# argument is exactly the one that would also excuse caching the lint
+# layer, and this repo has ruled it insufficient: a cached check layer
+# checks nothing, and the cost of being wrong is silent. Forcing it costs
+# milliseconds and puts the epoch in the log, where a reader can see that
+# this validation ran rather than being replayed.
+RUN echo "check epoch: ${CHECK_EPOCH}" && \
+    golangci-lint config verify --config .golangci.yml
+
+RUN echo "check epoch: ${CHECK_EPOCH}" && \
+    golangci-lint run --config .golangci.yml ./...

Makefile

@@ -87,10 +87,10 @@ clean:
 	go clean
 
 # Install dependencies. The linter is deliberately not installed here:
-# script/lint runs the digest-pinned golangci-lint image declared by the
+# script/lint lints by building Dockerfile.lint, whose FROM line is the
-# Dockerfile's lint stage, which is the single source of truth for the
+# single source of truth for the linter version. A second, separately
-# linter version. A second, separately pinned copy on PATH could drift
+# pinned copy on PATH could drift from it and make a local `make lint`
-# from it and make a local `make lint` disagree with CI.
+# disagree with CI.
 deps:
 	go mod download
 

README.md

@@ -344,7 +344,7 @@ both are set.
 ├── blobs/
 │   └── <aa>/<bb>/<full_blob_hash>
 └── metadata/
-    └── <snapshot_id>/
+    └── <remote-key>/
         ├── db.zst.age          # Encrypted binary SQLite database
         └── manifest.json.zst   # Unencrypted blob list (for pruning)
 ```
@@ -355,8 +355,18 @@ both are set.
 * `manifest.json.zst` is an unencrypted compressed JSON blob list, enabling
   pruning without the private key
 
-Snapshot IDs follow the format `<hostname>_<snapshot-name>_<RFC3339-timestamp>`
+Snapshot IDs follow the human-readable format
-(e.g. `server1_home_2025-06-01T12:00:00Z`).
+`<hostname>_<snapshot-name>_<RFC3339-timestamp>` (e.g.
+`server1_home_2025-06-01T12:00:00Z`), but this ID is never written to the
+destination store in plaintext. Each snapshot's metadata directory is named
+with its `<remote-key>`, a one-way double SHA-256 hash of the ID, so a listing
+of the store reveals no hostname or snapshot name. The backup time is not
+hidden: manifest.json.zst carries a plaintext timestamp, and object
+modification times are visible at the storage layer regardless. For example,
+`server1_home_2025-06-01T12:00:00Z` is stored under
+`metadata/17f97bcde958748af076b926af59823943db59e80ce7170b40f124dfa28f64aa/`.
+See [docs/REPOSTRUCTURE.md](docs/REPOSTRUCTURE.md#remote-key-derivation) for the
+derivation.
 
 ### data flow
 
@@ -373,7 +383,7 @@ Snapshot IDs follow the format `<hostname>_<snapshot-name>_<RFC3339-timestamp>`
 
 **restore:**
 
-1. Download and decrypt `metadata/<snapshot_id>/db.zst.age`
+1. Download and decrypt `metadata/<remote-key>/db.zst.age`
 2. Open the binary SQLite database
 3. Query files (optionally filtered by paths)
 4. Download and decrypt required blobs
@@ -598,10 +608,11 @@ regardless of color setting (emoji are not color).
 
 * Go 1.26 or later
 * Docker, with a reachable daemon, to lint, check, or commit:
-  `script/lint` runs the digest-pinned `golangci-lint` image declared by
+  `script/lint` lints by building `Dockerfile.lint`, which runs the
-  the `Dockerfile` lint stage, and `make check` and the pre-commit hook
+  digest-pinned `golangci-lint` image as a build step, and `make check`
-  both run it. A `golangci-lint` installed on `PATH` is not a substitute
+  and the pre-commit hook both run it. A `golangci-lint` installed on
-  and is never used on a host, whatever its version.
+  `PATH` is not a substitute and is never used on a host, whatever its
+  version.
 * `sqlite3` CLI, which the test suite shells out to
 * S3-compatible object storage (or local filesystem, or rclone remote)
 
@@ -671,46 +682,71 @@ them. We provide:
   diverges from the 30s `REPO_POLICIES.md` mandates; the reasoning is in
   the comment in the script, and issue #101 proposes amending the policy
   text.
-* `script/lint` — run `golangci-lint run ./...` at the exact version CI
+* `script/lint` — lint by building `Dockerfile.lint`, which runs
-  uses, by running the digest-pinned `golangci-lint` image declared by
+  `golangci-lint run --config .golangci.yml ./...` as a build step
-  the `Dockerfile` lint stage (requires Docker; it fails loudly rather
+  inside the digest-pinned `golangci-lint` image, so a successful build
-  than falling back to a differently versioned `golangci-lint` on
+  *is* a clean lint. Nothing lints on the host, at any version, ever;
-  `PATH`). That `FROM` line is the single source of truth for the linter
+  the script requires Docker and fails loudly rather than falling back
-  version — bump it there and nowhere else.
+  to a `golangci-lint` on `PATH`. That `FROM` line is the single source
+  of truth for the linter version — bump it there and nowhere else.
+
+  It takes no arguments, because a build step has no command line to
+  pass flags to, and it passes a fresh `--build-arg CHECK_EPOCH` on
+  every invocation so the lint layer cannot be replayed from cache (see
+  `script/cibuild` below for what that mechanism defends against). To
+  watch the linter execute, run it as
+  `BUILDKIT_PROGRESS=plain script/lint` and check that the lint layer
+  says `RUN … golangci-lint` rather than `CACHED`.
+
+  One container per run means one lint cache and one `golangci-lint`
+  lock per run, both private to it and discarded with it, so concurrent
+  runs on one host cannot contaminate or block each other.
 * `script/lint-fix` — apply the linter's autofixes (rewrites files),
-  using the same pinned linter
+  using the same pinned image, parsed out of `Dockerfile.lint`. It
+  cannot be a build step, because fixes have to land in the worktree, so
+  it bind-mounts the tree into a `docker run` and therefore needs a
+  *local* daemon. It is a developer convenience and never a gate: no
+  gate reads its exit status. Run `make lint` afterwards to find out
+  whether the tree is clean.
 * `script/fmt` — format all code (writes)
 * `script/fmt-check` — check formatting (read-only)
 * `script/check` — run `script/test`, `script/lint`, and
-  `script/fmt-check`. This is authoritative *because* `script/lint` uses
+  `script/fmt-check`. This is authoritative *because* `script/lint`
-  the pinned linter: a local `make check` and CI cannot disagree about
+  builds `Dockerfile.lint`: a local `make check` and CI cannot disagree
-  lint findings.
+  about lint findings.
 * `script/docker` — build the Docker image tagged via
   `script/projectname`. Passes a fresh `--build-arg CHECK_EPOCH` for the
   same reason `script/cibuild` does, so a local image build cannot be
-  green on checks it replayed from cache.
+  green on checks it replayed from cache. It builds the *product* image
-* `script/cibuild` — CI entrypoint: `docker build` (the `Dockerfile`
+  only, and the product `Dockerfile` has no lint stage, so it does not
-  runs `make fmt-check` and `make lint` in its lint stage and `make
+  lint: a green here means formatted, tested, and it compiles.
-  test` in its builder stage). This is the full CI-equivalent gate — it
+* `script/cibuild` — CI entrypoint, and the full gate. Two builds, in
-  runs the checks in the same containers CI does, from a clean copy of
+  order: `Dockerfile.lint` (the linter, as a build step) and then
-  the tree, so it also catches anything that depends on host state. It
+  `Dockerfile` (`make fmt-check` and `make test` in its builder stage,
-  passes a fresh `--build-arg CHECK_EPOCH`, unique per invocation, which
+  then the product image). Either failing fails the script. It runs the
-  the `Dockerfile` declares immediately above the check `RUN`s in both
+  checks in the same containers CI does, from a clean copy of the tree,
-  stages and expands into each check command. Those layers are keyed on
+  so it also catches anything that depends on host state.
+  `.gitea/workflows/check.yml` runs it on every push to `main` and
+  `next` and on every pull request against either.
+
+  It passes a fresh `--build-arg CHECK_EPOCH` to each build, unique per
+  invocation, which both files declare immediately above their check
+  `RUN`s and expand into each check command. Those layers are keyed on
   that value, so a new value re-runs them even on a byte-identical tree,
   and a green from this script means the checks executed. Dependency and
   module layers sit above the `ARG` and still cache, so a build is not
   cold.
 
-  A build that supplies no `CHECK_EPOCH` — a bare `docker build .` —
+  A build that supplies no `CHECK_EPOCH` — a bare `docker build .` or
-  fails rather than lying. An unset `ARG` is an empty string and an
+  `docker build -f Dockerfile.lint .` — fails rather than lying. An
-  empty string is a stable cache key, so without a guard such a build
+  unset `ARG` is an empty string and an empty string is a stable cache
-  would serve all three check layers from cache, execute nothing, and
+  key, so without a guard such a build would serve every check layer
-  still exit 0. Each check stage therefore asserts the value is
+  from cache, execute nothing, and still exit 0. Each file therefore
-  non-empty before running anything, and because failed steps are never
+  asserts the value is non-empty before running anything, and because
-  cached that assertion fires on every invocation rather than once. Use
+  failed steps are never cached that assertion fires on every
-  `script/cibuild` (or `script/docker`, which passes the same arg); a
+  invocation rather than once. Use `script/lint`, `script/docker` or
-  bare `docker build .` is now a loud error.
+  `script/cibuild`, which pass the arg; a bare `docker build` is a loud
+  error.
 * `script/precommit` — pre-commit gate: `go mod tidy` + `go fmt` (must
   not change files), then `script/check`
 * `script/install-precommit` — install the git pre-commit hook that

TODO.md

@@ -25,6 +25,72 @@ release" is exactly the contradiction
 
 # Completed Steps
 
+- 2026-09-21: Made `.gitea/workflows/check.yml` run on pushes to `main`
+  and `next` and on pull requests against either, so unit PRs (whose
+  base is `next`) and `next` itself get a CI run instead of relying on a
+  local `make check`
+  ([issue #122](https://git.eeqj.de/sneak/vaultik/issues/122)).
+
+- 2026-08-10: Moved every lint run into its own container, as a build
+  step ([issue #113](https://git.eeqj.de/sneak/vaultik/issues/113)).
+  New root `Dockerfile.lint`, built by `script/lint`, runs
+  `golangci-lint run --config .golangci.yml ./...` as a `RUN`
+  instruction in the digest-pinned `golangci/golangci-lint` image: a
+  successful build of that file *is* a clean lint, and it works even
+  where the daemon is remote and bind mounts are impossible. That
+  `FROM` line is now the only pin of the linter version in the repo.
+
+  This supersedes the per-worktree cache isolation landed for
+  [issue #99](https://git.eeqj.de/sneak/vaultik/issues/99). Isolation
+  fixed cross-worktree contamination but not lock contention — two
+  concurrent runs with entirely separate cache directories still
+  collided. A container per run has its own cache and its own lock, so
+  the whole class is gone, and with it the per-worktree cache
+  machinery, the lock-retry loop, and `script/lint-audit`, which
+  existed to catch replayed findings from a cache that no longer
+  exists. The host lint path went too: no escape hatch, no
+  `VAULTIK_LINT_IN_CONTAINER`, no version detection. Nothing lints on
+  the host at any version.
+
+  A cached build lints nothing, so the same `CHECK_EPOCH` mechanism the
+  product `Dockerfile` already used is what makes the green mean
+  something: `ARG CHECK_EPOCH` with no default below the module layers,
+  a `RUN [ -n "$CHECK_EPOCH" ] || exit 1` guard, the value expanded
+  into each check command, and a fresh `$(date +%s%N)$$` per invocation
+  computed as a bare assignment. `cmd/vaultik/lintdocker_test.go`
+  parses both Dockerfiles and both scripts and fails if any part of
+  that is dropped, because every way of losing it is silent. Its
+  host-lint assertion is structural — no script runs `golangci-lint`
+  except through `docker` — rather than a search for the one retired
+  variable name, which nothing could ever reintroduce.
+
+  The product `Dockerfile` lost its lint stage rather than gaining a
+  second linter pin: `make lint` is now `docker build`, so the stage
+  would have been docker-in-docker with no daemon, and calling
+  `golangci-lint` directly there would have restored the two-pins drift
+  of [issue #78](https://git.eeqj.de/sneak/vaultik/issues/78).
+  `make fmt-check` moved beside `make test` in the builder stage, and
+  `script/cibuild` now builds `Dockerfile.lint` and then `Dockerfile`,
+  each with its own fresh epoch. Consequence, stated rather than left
+  to be found: `script/docker` builds the product image only and no
+  longer lints; the gates are `script/check` and `script/cibuild`.
+
+  `golangci-lint config verify` runs as its own epoch-keyed layer,
+  above the lint. `golangci-lint run` rejects a config it cannot parse
+  but silently ignores an unknown top-level *key*: renaming `linters:`
+  to `linterz:` discarded `default: all` and every threshold and still
+  exited 0 on a tree the real config fails. `config verify` catches
+  that, and it does so with the network off at this pin — checked under
+  `docker run --network none`, not assumed. An earlier revision omitted
+  it on the claim that it fetches its schema over live HTTPS; that
+  claim was false at v2.12.2.
+
+  `script/lint-fix` is kept, reimplemented as a
+  bind-mounted `docker run` against the image parsed out of
+  `Dockerfile.lint` — it cannot be a build step, because fixes have to
+  land in the worktree — and marked in its header as a developer
+  convenience that no gate reads.
+
 - 2026-08-09: Finished the `--json` stdout contract and gave `make build`
   a rule ([issue #108](https://git.eeqj.de/sneak/vaultik/issues/108),
   [issue #110](https://git.eeqj.de/sneak/vaultik/issues/110)). Two

cmd/vaultik/lintdocker_test.go

@@ -0,0 +1,689 @@
+package main_test
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// This file guards the shape of the lint gate. Every property asserted
+// here is one whose loss is SILENT: the build still exits 0, the gate
+// still looks green, and nothing was linted or tested.
+//
+// The gate is a build step. script/lint builds Dockerfile.lint, which
+// runs golangci-lint as a RUN instruction, so a successful build is a
+// clean lint. BuildKit will happily replay that RUN from cache on an
+// unchanged tree in well under a second, which is why the check layers
+// are keyed on a CHECK_EPOCH build arg that the calling script
+// regenerates per invocation, and why an empty value is a hard error
+// rather than a stable cache key.
+//
+// These are parses rather than invocations. Shelling out to docker from
+// the test suite would nest a build inside `make test`, which itself
+// runs inside a build in CI. The one property a parse cannot establish
+// -- that a real finding actually fails the build -- is verified by
+// hand against a deliberately broken tree, recorded on the pull
+// request.
+
+// The files under guard, relative to the repository root.
+const (
+	lintDockerfile    = "Dockerfile.lint"
+	productDockerfile = "Dockerfile"
+	lintScript        = "script/lint"
+	cibuildScript     = "script/cibuild"
+)
+
+// linterBinary is the linter's command name. Every occurrence of it in
+// executable shell in this repo must be inside a docker invocation; see
+// TestNoHostLintPathRemains.
+const linterBinary = "golangci-lint"
+
+// checkEpochARG is the declaration, with no default value. A default
+// would satisfy the non-empty guard with a constant, and a constant is
+// a stable cache key: the checks would be replayed from cache forever
+// after the first build.
+const checkEpochARG = "ARG CHECK_EPOCH"
+
+// checkEpochGuard is what turns a build that omits --build-arg into a
+// loud failure instead of a quiet green. Failed steps are never cached,
+// so it fires on every such invocation rather than once.
+const checkEpochGuard = `RUN [ -n "$CHECK_EPOCH" ] || exit 1`
+
+// freshEpoch is the epoch computation the calling scripts must use, as
+// a bare assignment on its own line. Inline in an argument, a failing
+// `date` would not abort under `set -eu`; CHECK_EPOCH would become the
+// empty string, and the guard above would be the only thing standing
+// between that and a permanently cached green. `$$` is required because
+// `date +%s` is second-granular and busybox silently drops `%N`, so
+// without the pid two concurrent runs in one second can collide.
+const freshEpoch = `epoch="$(date +%s%N)$$"`
+
+// TestLintDockerfilePinsTheLinterByDigest fails if the lint image stops
+// being pinned. An unpinned tag makes the gate's verdict depend on
+// whatever the registry currently serves under that name.
+func TestLintDockerfilePinsTheLinterByDigest(t *testing.T) {
+	t.Parallel()
+
+	from := ""
+
+	for _, instruction := range instructions(t, lintDockerfile) {
+		if strings.HasPrefix(instruction, "FROM ") {
+			from = instruction
+
+			break
+		}
+	}
+
+	require.NotEmpty(t, from, "%s declares no FROM", lintDockerfile)
+	assert.Contains(t, from, "golangci/golangci-lint",
+		"the lint image must be the golangci-lint image")
+	assert.Contains(t, from, "@sha256:",
+		"the lint image must be pinned by digest, not by tag alone")
+}
+
+// TestLintDockerfileCannotBeCachedGreen pins the whole cache-busting
+// mechanism in the file that lints: the declaration with no default,
+// the non-empty guard, and the value expanded into the lint command
+// itself rather than merely declared.
+func TestLintDockerfileCannotBeCachedGreen(t *testing.T) {
+	t.Parallel()
+
+	found := instructions(t, lintDockerfile)
+
+	argAt := indexOf(found, checkEpochARG)
+	require.GreaterOrEqual(t, argAt, 0,
+		"%s must declare `%s` with no default value",
+		lintDockerfile, checkEpochARG)
+
+	assert.GreaterOrEqual(t, indexOf(found, checkEpochGuard), argAt,
+		"%s must guard against an empty CHECK_EPOCH with `%s`",
+		lintDockerfile, checkEpochGuard)
+
+	assertEpochExpandedInto(t, found[argAt:], "golangci-lint run")
+
+	// Dependency layers must stay above the ARG, or every lint run
+	// re-downloads the module cache and the inner loop becomes
+	// unusable.
+	download := indexOf(found, "RUN go mod download")
+	require.GreaterOrEqual(t, download, 0,
+		"%s must download modules in their own layer", lintDockerfile)
+	assert.Less(t, download, argAt,
+		"`%s` must come after `go mod download` so dependency layers"+
+			" still cache", checkEpochARG)
+}
+
+// TestLintDockerfileVerifiesTheLinterConfig guards the validation of
+// .golangci.yml itself. `golangci-lint run` rejects a config it cannot
+// parse but silently IGNORES an unknown top-level key, so renaming
+// `linters:` to `linterz:` discards `default: all` and every threshold
+// and still exits 0 reporting no issues. `config verify` is what turns
+// that into a failure, and it has to run BEFORE the lint, or the lint
+// spends a minute reporting a verdict from a config already known to be
+// wrong.
+func TestLintDockerfileVerifiesTheLinterConfig(t *testing.T) {
+	t.Parallel()
+
+	found := instructions(t, lintDockerfile)
+	verify := linterBinary + " config verify"
+
+	verifyAt := indexContaining(found, verify)
+	require.GreaterOrEqual(t, verifyAt, 0,
+		"%s must run `%s --config .golangci.yml`: without it a typo'd"+
+			" top-level key in .golangci.yml is silently ignored and the"+
+			" gate passes with only the default linter set", lintDockerfile,
+		verify)
+
+	runAt := indexContaining(found, linterBinary+" run")
+	require.GreaterOrEqual(t, runAt, 0, "%s must lint", lintDockerfile)
+	assert.Less(t, verifyAt, runAt,
+		"%s must verify the config before linting with it", lintDockerfile)
+
+	// Keyed on the epoch like every other check layer, so it executes
+	// per invocation rather than being replayed. A cached validation
+	// validates nothing.
+	assertEpochExpandedInto(t, found, verify)
+}
+
+// TestProductDockerfileCannotBeCachedGreen holds the same line for the
+// checks that remain in the product image build.
+func TestProductDockerfileCannotBeCachedGreen(t *testing.T) {
+	t.Parallel()
+
+	found := instructions(t, productDockerfile)
+
+	argAt := indexOf(found, checkEpochARG)
+	require.GreaterOrEqual(t, argAt, 0,
+		"%s must declare `%s` with no default value",
+		productDockerfile, checkEpochARG)
+
+	assert.GreaterOrEqual(t, indexOf(found, checkEpochGuard), argAt,
+		"%s must guard against an empty CHECK_EPOCH", productDockerfile)
+
+	assertEpochExpandedInto(t, found[argAt:], "make fmt-check")
+	assertEpochExpandedInto(t, found[argAt:], "make test")
+}
+
+// TestProductDockerfileDoesNotLint records the split deliberately: the
+// linter lives in Dockerfile.lint and nowhere else, so there is exactly
+// one digest pinning it. A lint stage reintroduced here would either be
+// docker-in-docker (`make lint` is now `docker build`) or a second,
+// independently bumpable pin.
+func TestProductDockerfileDoesNotLint(t *testing.T) {
+	t.Parallel()
+
+	contents := readRepoFile(t, productDockerfile)
+
+	for _, forbidden := range []string{"golangci", "make lint"} {
+		assert.NotContains(t, instructionText(contents), forbidden,
+			"%s must not lint: the linter is pinned once, in %s",
+			productDockerfile, lintDockerfile)
+	}
+}
+
+// TestLintScriptBuildsTheLintDockerfileWithAFreshEpoch is the other
+// half of the mechanism. The Dockerfile's guard only rejects an EMPTY
+// epoch; a constant non-empty one would satisfy it and still be served
+// from cache forever.
+func TestLintScriptBuildsTheLintDockerfileWithAFreshEpoch(t *testing.T) {
+	t.Parallel()
+
+	script := readRepoFile(t, lintScript)
+
+	assertBareEpochAssignment(t, script, lintScript)
+	assert.Contains(t, script, `--build-arg CHECK_EPOCH="$epoch"`,
+		"%s must pass the fresh epoch to the build", lintScript)
+	assert.Contains(t, script, lintDockerfile,
+		"%s must build %s", lintScript, lintDockerfile)
+}
+
+// TestCibuildBuildsBothDockerfilesWithFreshEpochs guards the CI gate:
+// dropping either build silently removes a whole class of check from
+// CI while leaving it green.
+func TestCibuildBuildsBothDockerfilesWithFreshEpochs(t *testing.T) {
+	t.Parallel()
+
+	script := readRepoFile(t, cibuildScript)
+
+	assertBareEpochAssignment(t, script, cibuildScript)
+	assert.Equal(t, 2, strings.Count(script, freshEpoch),
+		"%s must compute a fresh epoch for each of its two builds",
+		cibuildScript)
+	assert.Equal(t, 2,
+		strings.Count(script, `--build-arg CHECK_EPOCH="$epoch"`),
+		"%s must pass a fresh epoch to both builds", cibuildScript)
+	assert.Contains(t, script, "-f Dockerfile.lint",
+		"%s must build %s", cibuildScript, lintDockerfile)
+}
+
+// TestNoHostLintPathRemains fails if any escape hatch to a host linter
+// comes back. The owner's ruling is that every lint run happens inside
+// a container; a PATH binary that happens to match the pinned version
+// is a different build reached by a different code path, and admitting
+// it is what lets a local pass disagree with CI.
+//
+// This asserts the PROPERTY -- no script invokes the linter except
+// through docker -- rather than the absence of any particular variable
+// name. An earlier version of this test looked only for the literal
+// VAULTIK_LINT_IN_CONTAINER, the name of the hatch that was removed
+// alongside it, so nothing could ever trip it again: a hatch under any
+// other name left it passing. A structural test that passes on a broken
+// tree is worse than no test, because it is what a later reader trusts
+// instead of re-deriving the invariant.
+//
+// script/lint-fix is not exempted. It is the one script that runs the
+// linter as a container rather than as a build step, but it still runs
+// it in one, so the same property holds of it.
+func TestNoHostLintPathRemains(t *testing.T) {
+	t.Parallel()
+
+	root := repoRoot(t)
+
+	entries, err := os.ReadDir(filepath.Join(root, "script"))
+	require.NoError(t, err)
+	require.NotEmpty(t, entries, "no scripts found to scan")
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+
+		name := filepath.Join("script", entry.Name())
+
+		lines, err := shellCode(readRepoFile(t, name))
+		require.NoError(t, err, "scanning %s", name)
+
+		for _, line := range lines {
+			assertLinterIsContainerised(t, name, line)
+		}
+	}
+}
+
+// assertLinterIsContainerised fails unless every command that names the
+// linter on this joined line is a docker command. Merely mentioning
+// docker somewhere on the line is not enough; see linterRunsInDocker.
+func assertLinterIsContainerised(t *testing.T, name, line string) {
+	t.Helper()
+
+	assert.True(t, linterRunsInDocker(line),
+		"%s runs %s outside a container; every command that names the"+
+			" linter must begin with docker (line: %s)", name, linterBinary,
+		line)
+}
+
+// linterRunsInDocker reports whether the linter, wherever it appears on
+// this joined shell line, is only ever the argument of a docker command.
+// The line is cut into the simple commands the shell would run -- on
+// `;`, `&&`, `||` and `|` -- and every command that names the linter
+// must begin with `docker`. This is what distinguishes the one
+// legitimate invocation, script/lint-fix's `docker run ... golangci-lint
+// run ...`, from evasions like `docker info; golangci-lint run` or
+// `docker info || golangci-lint run`, where the linter sits in a command
+// of its own that docker does not introduce.
+func linterRunsInDocker(line string) bool {
+	for _, command := range splitShellCommands(line) {
+		if !strings.Contains(command, linterBinary) {
+			continue
+		}
+
+		if !strings.HasPrefix(strings.TrimSpace(command), "docker") {
+			return false
+		}
+	}
+
+	return true
+}
+
+// splitShellCommands breaks a joined shell line into the separate simple
+// commands the shell would run, cutting at the `;`, `&&`, `||` and `|`
+// operators (`||` before `|`, so the two-character operator is not split
+// twice). It is deliberately blind to quoting and to `$(...)`: no line
+// under guard puts one of these operators inside a string, and a scan
+// that tried to account for that would be the kind of half-parser this
+// file avoids.
+func splitShellCommands(line string) []string {
+	for _, op := range []string{"&&", "||", "|", ";"} {
+		line = strings.ReplaceAll(line, op, "\n")
+	}
+
+	return strings.Split(line, "\n")
+}
+
+// TestShellCodeSeesCodeAndNotProse keeps the scanner above honest. It
+// has to ignore comments and here-document bodies, because script/lint
+// and script/bootstrap both NAME golangci-lint in prose -- in comments,
+// and in the error text they print -- precisely to say that the host
+// binary is never used. A scanner that went blind, by over-eager
+// stripping or by failing to join continuation lines, would make
+// TestNoHostLintPathRemains pass on everything.
+func TestShellCodeSeesCodeAndNotProse(t *testing.T) {
+	t.Parallel()
+
+	// A `<<` inside quotes is not a here-document, so the code after it
+	// is still scanned; a real `<<EOF` opens one and its body is dropped.
+	script := strings.Join([]string{
+		"#!/bin/sh",
+		"# a comment naming golangci-lint",
+		"cat >&2 <<EOF",
+		"prose naming golangci-lint, printed not executed",
+		"EOF",
+		`echo "a left shift << is not a here-document"`,
+		"docker run --rm \\",
+		"    \"$image\" \\",
+		"    golangci-lint run ./...",
+	}, "\n")
+
+	lines, err := shellCode(script)
+	require.NoError(t, err)
+	assert.Equal(t,
+		[]string{
+			"cat >&2 <<EOF",
+			`echo "a left shift << is not a here-document"`,
+			`docker run --rm "$image" golangci-lint run ./...`,
+		},
+		lines)
+
+	// A `<<` inside an inline comment is not a here-document either: an
+	// unquoted, word-initial `#` begins a comment that runs to end of
+	// line, so the `<< STOP` is prose. The code that follows is still
+	// scanned -- here, a host golangci-lint that TestNoHostLintPathRemains
+	// must then see rather than have swallowed. The fake terminator even
+	// recurs later as a line of its own; a phantom here-document would
+	// swallow everything up to it silently, past the end-of-file error
+	// that only catches a terminator which never recurs.
+	inlineComment := strings.Join([]string{
+		": # housekeeping marker << STOP",
+		"golangci-lint run --config .golangci.yml ./...",
+		"STOP",
+	}, "\n")
+
+	lines, err = shellCode(inlineComment)
+	require.NoError(t, err)
+	assert.Equal(t,
+		[]string{
+			": # housekeeping marker << STOP",
+			"golangci-lint run --config .golangci.yml ./...",
+			"STOP",
+		},
+		lines)
+
+	// A here-document still open at end of file must be a loud error,
+	// not a silent truncation of everything the scanner has yet to see.
+	unterminated := strings.Join([]string{
+		"cat <<EOF",
+		"body line naming golangci-lint, no terminator follows",
+	}, "\n")
+
+	_, err = shellCode(unterminated)
+	require.Error(t, err)
+}
+
+// TestLinterCommandMustBeginWithDocker pins the property that a mention
+// of docker somewhere on the line is not enough: the command that
+// actually runs the linter has to be a docker command. The two evasions
+// from the issue place the linter in a command of its own, joined to a
+// harmless docker command by `;` or `||`; both must be rejected. The
+// containerised invocation script/lint-fix writes -- docker run with the
+// linter as its argument -- must still be accepted.
+func TestLinterCommandMustBeginWithDocker(t *testing.T) {
+	t.Parallel()
+
+	rejected := []string{
+		"docker info >/dev/null; golangci-lint run ./...",
+		"docker info || golangci-lint run ./...",
+		"docker build . && golangci-lint run ./... | tee log",
+	}
+	for _, line := range rejected {
+		assert.False(t, linterRunsInDocker(line),
+			"a linter command docker does not introduce must be rejected: %s",
+			line)
+	}
+
+	accepted := []string{
+		`docker run --rm "$image" golangci-lint run ./...`,
+		`docker run --rm --user x --volume "$ROOT:/src" img golangci-lint run --fix ./...`,
+	}
+	for _, line := range accepted {
+		assert.True(t, linterRunsInDocker(line),
+			"a docker-introduced linter command must be accepted: %s", line)
+	}
+}
+
+// assertEpochExpandedInto fails unless some instruction runs the named
+// command with the epoch expanded into it. Expansion, not mere
+// declaration: an ARG that no instruction references is not guaranteed
+// to key the layer, and the expansion also puts the value in the build
+// log where a reader can see the layer was keyed fresh.
+func assertEpochExpandedInto(t *testing.T, found []string, command string) {
+	t.Helper()
+
+	for _, instruction := range found {
+		if !strings.HasPrefix(instruction, "RUN ") {
+			continue
+		}
+
+		if strings.Contains(instruction, command) &&
+			strings.Contains(instruction, "${CHECK_EPOCH}") {
+			return
+		}
+	}
+
+	assert.Fail(t, "no epoch-keyed layer runs the command",
+		"`%s` must run in a layer that expands ${CHECK_EPOCH}, or it"+
+			" will be replayed from cache without executing", command)
+}
+
+// assertBareEpochAssignment fails unless the script computes the epoch
+// as a bare assignment on its own line.
+func assertBareEpochAssignment(t *testing.T, script, name string) {
+	t.Helper()
+
+	for line := range strings.SplitSeq(script, "\n") {
+		if strings.TrimSpace(line) == freshEpoch {
+			return
+		}
+	}
+
+	assert.Fail(t, "no bare epoch assignment",
+		"%s must compute `%s` as a bare assignment on its own line, so"+
+			" `set -e` catches a failing date instead of quietly"+
+			" building with an empty epoch", name, freshEpoch)
+}
+
+// instructions returns the Dockerfile's instructions, one per element,
+// with comments and blank lines dropped and continuation lines joined,
+// so a multi-line RUN is one string.
+func instructions(t *testing.T, name string) []string {
+	t.Helper()
+
+	return strings.Split(instructionText(readRepoFile(t, name)), "\n")
+}
+
+// instructionText is instructions' parse, before splitting: it is also
+// what a "must not contain" assertion should look at, so that a word
+// appearing only in a comment is not mistaken for behaviour.
+func instructionText(contents string) string {
+	var (
+		out         []string
+		continued   string
+		isContinued bool
+	)
+
+	for line := range strings.SplitSeq(contents, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if !isContinued && (trimmed == "" || strings.HasPrefix(trimmed, "#")) {
+			continue
+		}
+
+		isContinued = strings.HasSuffix(trimmed, `\`)
+		continued += strings.TrimSuffix(trimmed, `\`)
+
+		if isContinued {
+			continue
+		}
+
+		out = append(out, strings.Join(strings.Fields(continued), " "))
+		continued = ""
+	}
+
+	return strings.Join(out, "\n")
+}
+
+// indexOf returns the position of the first instruction equal to, or
+// beginning with, want; -1 if there is none.
+func indexOf(found []string, want string) int {
+	for i, instruction := range found {
+		if instruction == want || strings.HasPrefix(instruction, want+" ") {
+			return i
+		}
+	}
+
+	return -1
+}
+
+// indexContaining returns the position of the first instruction
+// containing want; -1 if there is none.
+func indexContaining(found []string, want string) int {
+	for i, instruction := range found {
+		if strings.Contains(instruction, want) {
+			return i
+		}
+	}
+
+	return -1
+}
+
+// shellCode returns a POSIX shell script's executable lines: comments
+// dropped, here-document bodies dropped, and backslash continuations
+// joined so a multi-line command is a single string. Whitespace is
+// collapsed, as it is for Dockerfile instructions. A here-document left
+// open at end of file is an error rather than a silent truncation of
+// everything after its opener.
+//
+// Both exclusions are load-bearing rather than tidiness. The scripts
+// name golangci-lint in prose to state that the host binary is never
+// used, and joining continuations is what lets the one legitimate
+// container invocation -- script/lint-fix's `docker run`, whose linter
+// command sits several lines below the word `docker` -- be recognised
+// as containerised.
+//
+// This is a text scan, not a shell: it cannot see a linter name
+// assembled at runtime, one split across a continuation, a script in a
+// subdirectory of script/, or anything in the Makefile.
+func shellCode(contents string) ([]string, error) {
+	var (
+		out       []string
+		joined    string
+		terminate string
+	)
+
+	for line := range strings.SplitSeq(contents, "\n") {
+		trimmed := strings.TrimSpace(line)
+
+		if terminate != "" {
+			if trimmed == terminate {
+				terminate = ""
+			}
+
+			continue
+		}
+
+		if joined == "" && (trimmed == "" || strings.HasPrefix(trimmed, "#")) {
+			continue
+		}
+
+		joined += strings.TrimSuffix(trimmed, `\`) + " "
+		if strings.HasSuffix(trimmed, `\`) {
+			continue
+		}
+
+		joined = strings.Join(strings.Fields(joined), " ")
+		terminate = heredocTerminator(joined)
+
+		out = append(out, joined)
+		joined = ""
+	}
+
+	if terminate != "" {
+		return nil, fmt.Errorf("%w: terminator %q", errUnterminatedHeredoc,
+			terminate)
+	}
+
+	return out, nil
+}
+
+// errUnterminatedHeredoc is what shellCode returns when a here-document
+// is still open at end of file. Its callers require its absence, so an
+// unterminated body -- which would otherwise be swallowed silently --
+// fails the guard loudly.
+var errUnterminatedHeredoc = errors.New(
+	"here-document opened but never closed before end of file")
+
+// heredocTerminator returns the delimiter word of the here-document the
+// command opens, or "" if it opens none. A `<<` only opens one when it
+// is a real redirection: outside single and double quotes, not in an
+// inline comment, and followed by a delimiter word. A `<<` inside a
+// quoted string, past an unquoted word-initial `#` (which begins a
+// comment that runs to end of line), or in an arithmetic left shift
+// like `$((x << 2))`, is not a here-document; the first two are cases
+// this guards, the last appears in no script here. Only the first
+// opener on a line is recognised; nothing in script/ opens two.
+func heredocTerminator(line string) string {
+	var quote byte // 0 when outside quotes, else '\'' or '"'
+
+	for i := 0; i+1 < len(line); i++ {
+		c := line[i]
+
+		switch {
+		case quote != 0:
+			if c == quote {
+				quote = 0
+			}
+		case c == '\'' || c == '"':
+			quote = c
+		case c == '#' && (i == 0 || line[i-1] == ' '):
+			// A word-initial `#` starts a comment; the rest of the
+			// line, `<<` included, is prose, not a redirection.
+			return ""
+		case c == '<' && line[i+1] == '<':
+			return heredocWord(line[i+2:])
+		}
+	}
+
+	return ""
+}
+
+// heredocWord extracts the delimiter that follows `<<` or `<<-`: it drops
+// an optional `-`, skips blanks, then reads the delimiter -- quoted or
+// bare -- and returns it with quotes removed. `<<-'EOF'` and `<< EOF`
+// both yield "EOF". It returns "" when no word follows, so a bare `<<`
+// opens nothing.
+func heredocWord(after string) string {
+	after = strings.TrimLeft(strings.TrimPrefix(after, "-"), " \t")
+
+	var (
+		word  strings.Builder
+		quote byte
+	)
+
+	for i := range len(after) {
+		c := after[i]
+
+		switch {
+		case quote != 0:
+			if c == quote {
+				quote = 0
+			} else {
+				word.WriteByte(c)
+			}
+		case c == '\'' || c == '"':
+			quote = c
+		case c == ' ' || c == '\t':
+			return word.String()
+		default:
+			word.WriteByte(c)
+		}
+	}
+
+	return word.String()
+}
+
+// readRepoFile reads a file by its path relative to the repository
+// root.
+func readRepoFile(t *testing.T, name string) string {
+	t.Helper()
+
+	//nolint:gosec // G304: the path is a constant relative to this repo
+	contents, err := os.ReadFile(filepath.Join(repoRoot(t), name))
+	require.NoError(t, err)
+
+	return string(contents)
+}
+
+// repoRoot returns the repository root. The test binary runs with its
+// package directory as the working directory, so the root is found by
+// walking up until the module file appears.
+func repoRoot(t *testing.T) string {
+	t.Helper()
+
+	dir, err := os.Getwd()
+	require.NoError(t, err)
+
+	for {
+		_, err = os.Stat(filepath.Join(dir, "go.mod"))
+		if err == nil {
+			return dir
+		}
+
+		parent := filepath.Dir(dir)
+		require.NotEqual(t, dir, parent,
+			"walked to the filesystem root without finding a go.mod")
+
+		dir = parent
+	}
+}

cmd/vaultik/makefile_test.go

@@ -1,8 +1,6 @@
 package main_test
 
 import (
-	"os"
-	"path/filepath"
 	"regexp"
 	"slices"
 	"strings"
@@ -87,27 +85,11 @@ func TestBuildTargetBuildsTheBinary(t *testing.T) {
 }
 
 // readMakefile returns the contents of the repository's Makefile. The
-// test binary runs with its package directory as the working directory,
+// root is located by the shared walk in lintdocker_test.go.
-// so the root is found by walking up until the Makefile appears.
 func readMakefile(t *testing.T) string {
 	t.Helper()
 
-	dir, err := os.Getwd()
+	return readRepoFile(t, "Makefile")
-	require.NoError(t, err)
-
-	for {
-		//nolint:gosec // G304: the path is this test's own directory walk
-		contents, err := os.ReadFile(filepath.Join(dir, "Makefile"))
-		if err == nil {
-			return string(contents)
-		}
-
-		parent := filepath.Dir(dir)
-		require.NotEqual(t, dir, parent,
-			"walked to the filesystem root without finding a Makefile")
-
-		dir = parent
-	}
 }
 
 // phonyTargets returns every name declared phony, across all .PHONY

docs/DATAMODEL.md

@@ -194,8 +194,10 @@ After a snapshot is completed:
 2. Clean temporary database to contain only current snapshot data
 3. Export to SQL dump using sqlite3
 4. Compress with zstd and encrypt with age
-5. Upload to S3 as `metadata/{snapshot-id}/db.zst.age`
+5. Upload to S3 as `metadata/{remote-key}/db.zst.age`
-6. Generate blob manifest and upload as `metadata/{snapshot-id}/manifest.json.zst`
+6. Generate blob manifest and upload as `metadata/{remote-key}/manifest.json.zst`
+
+The `{remote-key}` directory name is a one-way hash of the human snapshot ID, so the ID is never written to the store in plaintext; see [REPOSTRUCTURE.md](REPOSTRUCTURE.md#remote-key-derivation).
 
 ### 4. Restore Process
 

docs/REPOSTRUCTURE.md

@@ -17,11 +17,13 @@ Vaultik stores all backup data in an S3-compatible object store. The repository
 │       └── <hash[2:4]>/
 │           └── <full-hash>
 └── metadata/
-    └── <snapshot-id>/
+    └── <remote-key>/
         ├── db.zst.age
         └── manifest.json.zst
 ```
 
+The metadata subdirectory is named with the **remote key**, a one-way hash of the snapshot ID, not with the human-readable snapshot ID itself. See [Remote Key Derivation](#remote-key-derivation).
+
 ## Blobs Directory (`blobs/`)
 
 ### Structure
@@ -40,9 +42,11 @@ Blobs contain the actual file data from backups and must be encrypted for securi
 
 ## Metadata Directory (`metadata/`)
 
-Each snapshot has its own subdirectory named with the snapshot ID.
+Each snapshot has its own subdirectory. The directory is **not** named with the human-readable snapshot ID; it is named with the remote key — a one-way hash of that ID. The human ID is never written to the destination store as a directory name (see [Remote Key Derivation](#remote-key-derivation)).
 
 ### Snapshot ID Format
+
+The human-readable snapshot ID is used in CLI arguments, log lines, and the local database. It is not written to the destination store.
 - **Format**: `<hostname>_<snapshot-name>_<RFC3339>` (or `<hostname>_<RFC3339>` if no
   name was specified)
 - **Example**: `laptop_home_2024-01-15T14:30:52Z`
@@ -51,6 +55,19 @@ Each snapshot has its own subdirectory named with the snapshot ID.
   - Snapshot name from the configured `snapshots:` map (optional)
   - RFC3339 UTC timestamp
 
+This ID reveals the hostname, the configured snapshot name, and the backup time, so it is never used as the on-disk directory name — the remote key is used instead.
+
+### Remote Key Derivation
+
+The remote key is `hex(SHA256(SHA256("vaultik|" + snapshot-id)))`: a double SHA-256 over the snapshot ID, with a `vaultik|` domain-separation prefix. The result is a 64-character hex string with no structure a remote observer can reverse. Implemented in `internal/snapshot/remotekey.go`.
+
+Worked example:
+- Snapshot ID: `server1_home_2025-06-01T12:00:00Z`
+- Remote key: `17f97bcde958748af076b926af59823943db59e80ce7170b40f124dfa28f64aa`
+- Directory: `metadata/17f97bcde958748af076b926af59823943db59e80ce7170b40f124dfa28f64aa/`
+
+Because the hash is one-way, a listing of the destination store reveals neither the hostname nor the snapshot name of any backup. The same remote key is stored in the manifest's `snapshot_id` field.
+
 ### Files in Each Snapshot Directory
 
 #### `db.zst.age` - Encrypted Database
@@ -68,16 +85,17 @@ Each snapshot has its own subdirectory named with the snapshot ID.
 - **Structure**:
 ```json
 {
-  "snapshot_id": "laptop_home_2024-01-15T14:30:52Z",
+  "snapshot_id": "17f97bcde958748af076b926af59823943db59e80ce7170b40f124dfa28f64aa",
-  "timestamp": "2024-01-15T14:30:52Z",
+  "timestamp": "2025-06-01T12:00:00Z",
   "blob_count": 42,
+  "total_compressed_size": 1048576,
   "blobs": [
-    "cafebabe1234567890abcdef1234567890abcdef1234567890abcdef12345678",
+    { "hash": "cafebabe1234567890abcdef1234567890abcdef1234567890abcdef12345678", "compressed_size": 24576 },
-    "deadbeef1234567890abcdef1234567890abcdef1234567890abcdef12345678",
+    { "hash": "deadbeef1234567890abcdef1234567890abcdef1234567890abcdef12345678", "compressed_size": 32768 }
-    ...
   ]
 }
 ```
+`snapshot_id` is the remote key (a hash), not the human ID; `timestamp` is written in the clear.
 
 ### Why Manifest is Unencrypted
 The manifest must be readable without the private key to enable:
@@ -86,7 +104,7 @@ The manifest must be readable without the private key to enable:
 3. **Verification** - Checking blob existence without decryption
 4. **Cross-snapshot deduplication analysis** - Finding shared blobs between snapshots
 
-The manifest only contains blob hashes, not file names or any other sensitive information.
+The manifest contains the remote key, the backup timestamp, the blob count and total compressed size, and each blob's hash and compressed size. It contains no file names, paths, or other decrypted metadata.
 
 ## Security Considerations
 
@@ -96,19 +114,21 @@ The manifest only contains blob hashes, not file names or any other sensitive in
 - **File-to-chunk mappings** (in db.zst.age)
 
 ### What's Not Encrypted
-- **Blob hashes** (in manifest.json.zst)
+- **The remote key** — directory names and the manifest `snapshot_id`, a one-way hash of the snapshot ID (see [Remote Key Derivation](#remote-key-derivation))
-- **Snapshot IDs** (directory names)
+- **The backup timestamp** (in manifest.json.zst)
-- **Blob count per snapshot** (in manifest.json.zst)
+- **Blob hashes and their compressed sizes** (in manifest.json.zst)
+- **Blob count and total compressed size per snapshot** (in manifest.json.zst)
 
 ### Privacy Implications
-From the unencrypted data, an observer can determine:
+From the unencrypted data, an observer of the destination store can determine:
-- When backups were taken (from snapshot IDs)
+- **When each backup was taken** — not from the directory name, which is a one-way hash, but from the plaintext `timestamp` field in manifest.json.zst, which is published in the clear
-- Which hostname created backups (from snapshot IDs)
+- How many blobs each snapshot references, and the total compressed size
-- How many blobs each snapshot references
+- The compressed size of each blob, and which blobs are shared between snapshots (deduplication patterns)
-- Which blobs are shared between snapshots (deduplication patterns)
+
-- The size of each encrypted blob
+Together these give an observer a timing-and-size profile of every snapshot. This is an accepted, documented property of the format, not a defect: the manifest is unencrypted so that pruning can run without the private key, and the timing channel could not be closed by encrypting it anyway — object creation times and per-object sizes stay visible at the storage layer on both `s3://` and `file://` destinations regardless.
 
 An observer cannot determine:
+- The hostname or snapshot name of any backup (the directory name and the manifest `snapshot_id` are one-way hashes of the human ID)
 - File names or paths
 - File contents
 - File permissions or ownership

internal/cli/config.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"os"
@@ -24,6 +25,11 @@ const configSetArgs = 2
 // parent config dirs (e.g. ~/.config) are conventionally traversable.
 const configDirMode = 0o755
 
+// configYAMLIndent matches the 2-space indentation of defaultConfigTemplate,
+// so `config set` writes the file back with the same indentation rather than
+// yaml.Marshal's 4-space default.
+const configYAMLIndent = 2
+
 var (
 	errConfigExists     = errors.New("config file already exists")
 	errEmptyConfig      = errors.New("empty config file")
@@ -381,7 +387,7 @@ Examples:
 				return err
 			}
 
-			out, err := yaml.Marshal(root)
+			out, err := marshalConfigYAML(root)
 			if err != nil {
 				return fmt.Errorf("marshaling config: %w", err)
 			}
@@ -405,6 +411,29 @@ Examples:
 	}
 }
 
+// marshalConfigYAML renders a config document tree with 2-space indentation,
+// matching defaultConfigTemplate. yaml.Marshal defaults to 4 spaces, which
+// would reindent the whole file on the first `config set` despite the promise
+// to preserve formatting.
+func marshalConfigYAML(root *yaml.Node) ([]byte, error) {
+	var buf bytes.Buffer
+
+	enc := yaml.NewEncoder(&buf)
+	enc.SetIndent(configYAMLIndent)
+
+	err := enc.Encode(root)
+	if err != nil {
+		return nil, err
+	}
+
+	err = enc.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
 // loadYAMLFile parses a YAML file into a yaml.Node document tree,
 // which preserves comments and ordering for round-tripping.
 func loadYAMLFile(path string) (*yaml.Node, error) {

internal/cli/config_test.go

@@ -188,6 +188,47 @@ func TestYAMLPathSet(t *testing.T) {
 	}
 }
 
+// TestConfigSetPreservesFormatting asserts the `config set` write path
+// (marshalConfigYAML) round-trips a 2-space-indented file without reindenting
+// it to yaml.Marshal's 4-space default, and keeps comments.
+func TestConfigSetPreservesFormatting(t *testing.T) {
+	t.Parallel()
+
+	root := parseTestYAML(t)
+
+	err := yamlPathSet(root, splitPath("s3.bucket"), "newbucket")
+	if err != nil {
+		t.Fatalf("set s3.bucket: %v", err)
+	}
+
+	out, err := marshalConfigYAML(root)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+
+	text := string(out)
+
+	for _, want := range []string{"# top comment", "# inline comment"} {
+		if !contains(text, want) {
+			t.Errorf("round-tripped YAML dropped comment %q:\n%s", want, text)
+		}
+	}
+
+	// Nested map keys stay at 2-space indent; the bug reindented them to 4.
+	if !contains(text, "\n  bucket: newbucket") {
+		t.Errorf("expected 2-space indent for s3.bucket, got:\n%s", text)
+	}
+
+	if contains(text, "\n    bucket:") {
+		t.Errorf("s3.bucket reindented to 4 spaces:\n%s", text)
+	}
+
+	// Sequence items under a key also stay at 2 spaces.
+	if !contains(text, "\n  - age1aaa") {
+		t.Errorf("expected 2-space indent for sequence item, got:\n%s", text)
+	}
+}
+
 func splitPath(s string) []string {
 	return strings.Split(s, ".")
 }

internal/cli/snapshot.go

@@ -135,7 +135,7 @@ specifying a path using --config or by setting VAULTIK_CONFIG to a path.`,
 	}
 
 	cmd.Flags().BoolVar(&opts.Cron, "cron", false,
-		"Run in cron mode (silent unless error)")
+		"Run in cron mode (silent unless warning or error)")
 	cmd.Flags().BoolVar(&opts.Prune, "prune", false,
 		"After backup, drop older snapshots of the same name and remove "+
 			"orphaned blobs")

internal/cli/vaultik_snapshot_types.go

@@ -1,12 +0,0 @@
-package cli
-
-import "time"
-
-// SnapshotInfo represents snapshot information for listing
-//
-//nolint:tagliatelle // snake_case is the established output format
-type SnapshotInfo struct {
-	ID             string    `json:"id"`
-	Timestamp      time.Time `json:"timestamp"`
-	CompressedSize int64     `json:"compressed_size"`
-}

internal/models/models.go

@@ -1,67 +0,0 @@
-// Package models defines shared value types describing files, chunks,
-// blobs, and snapshots as they move through the backup pipeline.
-package models
-
-import (
-	"time"
-)
-
-// FileInfo represents a file in the backup system
-type FileInfo struct {
-	Path  string
-	MTime time.Time
-	Size  int64
-}
-
-// ChunkInfo represents a content-addressed chunk
-type ChunkInfo struct {
-	Hash   string // SHA256 hash
-	Size   int64
-	Offset int64 // Offset within source file
-}
-
-// ChunkRef represents a reference to a chunk in a blob or file
-type ChunkRef struct {
-	ChunkHash string
-	Offset    int64
-	Length    int64
-}
-
-// BlobInfo represents an encrypted blob containing multiple chunks
-type BlobInfo struct {
-	Hash       string // SHA256 hash of the blob content (content-addressable)
-	CreatedAt  time.Time
-	Size       int64
-	ChunkCount int
-}
-
-// Snapshot represents a backup snapshot
-type Snapshot struct {
-	ID           string // ISO8601 timestamp
-	Hostname     string
-	Version      string
-	CreatedAt    time.Time
-	FileCount    int64
-	ChunkCount   int64
-	BlobCount    int64
-	TotalSize    int64
-	MetadataSize int64
-}
-
-// SnapshotMetadata contains the full metadata for a snapshot
-type SnapshotMetadata struct {
-	Snapshot   *Snapshot
-	Files      map[string]*FileInfo
-	Chunks     map[string]*ChunkInfo
-	Blobs      map[string]*BlobInfo
-	FileChunks map[string][]*ChunkRef // path -> chunks
-	BlobChunks map[string][]*ChunkRef // blob hash -> chunks
-}
-
-// Chunk represents a data chunk for processing
-type Chunk struct {
-	Data   []byte
-	Hash   string
-	Offset int64
-	Length int64
-}

internal/models/models_test.go

@@ -1,58 +0,0 @@
-package models_test
-
-import (
-	"testing"
-	"time"
-
-	"sneak.berlin/go/vaultik/internal/models"
-)
-
-// TestModelsCompilation ensures all model types can be instantiated
-func TestModelsCompilation(t *testing.T) {
-	t.Parallel()
-
-	// This test primarily serves as a compilation test
-	// to ensure all types are properly defined
-
-	// Test FileInfo
-	fi := &models.FileInfo{
-		Path:  "/test/file.txt",
-		MTime: time.Now(),
-		Size:  1024,
-	}
-	if fi.Path != "/test/file.txt" {
-		t.Errorf("FileInfo.Path not set correctly")
-	}
-
-	// Test ChunkInfo
-	ci := &models.ChunkInfo{
-		Hash:   "abc123",
-		Size:   512,
-		Offset: 0,
-	}
-	if ci.Hash != "abc123" {
-		t.Errorf("ChunkInfo.Hash not set correctly")
-	}
-
-	// Test BlobInfo
-	bi := &models.BlobInfo{
-		Hash:       "blob123",
-		CreatedAt:  time.Now(),
-		Size:       1024,
-		ChunkCount: 2,
-	}
-	if bi.Hash != "blob123" {
-		t.Errorf("BlobInfo.Hash not set correctly")
-	}
-
-	// Test Snapshot
-	s := &models.Snapshot{
-		ID:        "2024-01-01T00:00:00Z",
-		Hostname:  "test-host",
-		Version:   "1.0.0",
-		CreatedAt: time.Now(),
-	}
-	if s.ID != "2024-01-01T00:00:00Z" {
-		t.Errorf("Snapshot.ID not set correctly")
-	}
-}

internal/snapshot/remotekey.go

@@ -22,8 +22,9 @@ const remoteKeyPrefix = "vaultik|"
 //
 //   - the "metadata/<remote-key>/..." subdirectory on the storage
 //     backend so a directory listing of the bucket / file:// dest
-//     doesn't reveal hostnames, configured snapshot names, or backup
+//     doesn't reveal hostnames or configured snapshot names. (The
-//     timestamps;
+//     backup time is not hidden: the manifest.json.zst inside that
+//     directory carries a plaintext RFC3339 timestamp.)
 //   - the `snapshot_id` field of the unencrypted manifest.json.zst
 //     for the same reason;
 //   - any code path that needs to translate a known local snapshot ID

internal/snapshot/snapshot.go

@@ -840,8 +840,10 @@ func (sm *SnapshotManager) generateBlobManifest(
 	}
 
 	// Create manifest. SnapshotID in the unencrypted manifest is the
-	// double-SHA256 remote key, not the human ID, so the public bytes
+	// double-SHA256 remote key (see RemoteSnapshotKey), not the human ID,
-	// don't reveal hostname/snapshot-name/timestamp metadata.
+	// so neither this field nor the directory name reveals the hostname or
+	// snapshot name. Timestamp below is written in the clear, so the backup
+	// time is observable to anyone who can read the manifest.
 	manifest := &Manifest{
 		SnapshotID:          RemoteSnapshotKey(snapshotID),
 		Timestamp:           time.Now().UTC().Format(time.RFC3339),

script/bootstrap

@@ -48,11 +48,12 @@ missing() {
     ! command -v "$1" >/dev/null 2>&1
 }
 
-# Docker is a hard requirement, not a nice-to-have: script/lint runs the
+# Docker is a hard requirement, not a nice-to-have: script/lint lints by
-# digest-pinned golangci-lint image from the Dockerfile's lint stage, and
+# building Dockerfile.lint, whose digest-pinned golangci-lint image is
-# script/check and script/precommit both run script/lint. A bootstrap
+# the only place the linter runs, and script/check and script/precommit
-# that prints "bootstrap complete" on a machine where `make check` cannot
+# both run script/lint. A bootstrap that prints "bootstrap complete" on a
-# run is a false success, so this fails instead.
+# machine where `make check` cannot run is a false success, so this fails
+# instead.
 #
 # Installing docker from here was considered and rejected: it needs root,
 # a running daemon, and on macOS a GUI cask, so an attempt would itself
@@ -79,13 +80,15 @@ bootstrap: FAILED - $reason.
 
 Docker is required to develop this repo. Without it these do not work:
 
-  script/lint      runs the digest-pinned golangci-lint image declared
+  script/lint      builds Dockerfile.lint, which runs the linter as a
-                   by the Dockerfile's lint stage, which is the single
+                   build step in a digest-pinned golangci-lint image.
-                   source of truth for the linter version
+                   That FROM line is the single source of truth for the
+                   linter version
   script/check     runs script/lint
   script/precommit runs script/check, so commits are blocked by the
                    pre-commit hook installed by script/setup
-  script/cibuild   builds the Dockerfile, which is what CI runs
+  script/cibuild   builds Dockerfile.lint and Dockerfile, which is what
+                   CI runs
 
 Install docker (and start the daemon, checking DOCKER_HOST and your
 group membership), then re-run script/bootstrap. golangci-lint on PATH
@@ -104,12 +107,12 @@ main() {
     # Go toolchain
     if missing go; then pkg_install go golang go go; fi
 
-    # golangci-lint is deliberately NOT installed: script/lint runs the
+    # golangci-lint is deliberately NOT installed: script/lint lints by
-    # digest-pinned golangci-lint image from the Dockerfile's lint stage,
+    # building Dockerfile.lint, whose digest-pinned image is the only
-    # so whatever a package manager happens to ship would only be a
+    # place the linter runs, so whatever a package manager happens to
-    # shadow of the pinned version that could drift from CI. script/lint
+    # ship would only be a shadow of the pinned version that could drift
-    # will not use a PATH binary on a host at any version, so installing
+    # from CI. Nothing on the host is ever used as a linter, at any
-    # one here would buy nothing.
+    # version, so installing one here would buy nothing.
 
     # sqlite3 CLI: the test suite shells out to it (VACUUM).
     if missing sqlite3; then pkg_install sqlite sqlite3 sqlite sqlite; fi

script/cibuild

@@ -1,22 +1,31 @@
 #!/bin/sh
-# script/cibuild: run the CI build. The Dockerfile does not run
+# script/cibuild: run the CI build. This is the full gate, and it is two
-# script/check; it runs `make fmt-check` and `make lint` in its lint
+# builds, in this order:
-# stage and `make test` in its builder stage. A successful build
+#
-# implies those three passed, provided they actually ran -- which is
+#   Dockerfile.lint  the linter, as a build step (a clean build IS a
-# what the CHECK_EPOCH below is for.
+#                    clean lint)
-# Generic: needs no adaptation. The Gitea workflow runs this on push.
+#   Dockerfile       `make fmt-check` and `make test` in the builder
+#                    stage, then the product image
+#
+# Either one failing fails this script. Note what follows from the
+# split: script/docker builds only the product image and so no longer
+# lints -- this script and script/check (which runs script/lint) are the
+# things that decide whether the tree is clean.
+#
+# Generic apart from the two Dockerfiles: the Gitea workflow runs this
+# on push.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    # The Dockerfile's check layers are keyed on CHECK_EPOCH, so a
+    # Both Dockerfiles key their check layers on CHECK_EPOCH, so a fresh
-    # fresh value here is what forces them to re-run: without it an
+    # value is what forces those layers to re-run: without it an
     # unchanged tree replays them from cache, the checks never execute,
-    # and the build still exits 0. The ARG sits immediately above the
+    # and the build still exits 0. Each ARG sits immediately above the
-    # check RUNs, so dependency and module layers still cache. The
+    # check RUNs, so dependency and module layers still cache. Both
-    # Dockerfile also refuses to build at all when CHECK_EPOCH is empty,
+    # Dockerfiles also refuse to build at all when CHECK_EPOCH is empty,
     # so a missing value fails loudly here rather than passing quietly.
     #
     # The value must be unique per invocation, not per second. `date +%s`
@@ -35,6 +44,18 @@ main() {
     # script exists to prevent -- so the guard would disarm itself and
     # still exit 0. As a bare assignment, `set -e` catches a failing
     # `date` and no build starts.
+    #
+    # A separate value per build, because they are separate builds: one
+    # `date` shared between them would still be fresh, but reusing it
+    # invites the two to be collapsed into a single value that is
+    # computed somewhere else and passed in.
+    epoch="$(date +%s%N)$$"
+    # cacheonly for the lint build: its verdict is the exit status and
+    # the image is never run, so exporting it is pure cost. See
+    # script/lint.
+    docker build --output=type=cacheonly \
+        --build-arg CHECK_EPOCH="$epoch" -f Dockerfile.lint .
+
     epoch="$(date +%s%N)$$"
     docker build --build-arg CHECK_EPOCH="$epoch" .
 }

script/docker

@@ -2,6 +2,13 @@
 # script/docker: build the Docker image tagged with the project name.
 # Identical in all repos; the tag comes from script/projectname.
 # Generic: needs no adaptation.
+#
+# This builds the PRODUCT image only, and the product Dockerfile has no
+# lint stage: linting lives in Dockerfile.lint and is run by
+# script/lint. So a green here means `make fmt-check` and `make test`
+# passed and the image built -- it says nothing about lint. The gates
+# are script/check (which runs script/lint) and script/cibuild (which
+# builds both files).
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"

script/lint

@@ -1,110 +1,42 @@
 #!/bin/sh
 # script/lint: run the linter.
 #
-# The linter always runs at the version pinned by the Dockerfile's lint
+# The linter runs inside the image built by Dockerfile.lint, and it runs
-# stage, so a local run and a CI run of the same tree cannot disagree.
+# there as a BUILD STEP: a successful build of that file IS a clean
-# That FROM line (image tag plus digest) is the single source of truth
+# lint. Nothing lints on the host, at any version, ever. That FROM line
-# for the linter version in this repo: bump it there and nothing else
+# is the single source of truth for the linter version in this repo, so
-# needs editing.
+# a local run and a CI run of the same tree cannot disagree.
 #
-# Normally that means running the pinned image with docker. The one
+# One container per run means one lint cache and one golangci-lint lock
-# exception is running INSIDE that image: the Dockerfile's lint stage
+# per run, both private to that run and thrown away with it. That is
-# runs `make lint`, and there is no docker daemon in there. That stage
+# what makes concurrent runs on a shared host safe, and it is why this
-# sets VAULTIK_LINT_IN_CONTAINER=1, and only when that variable is set
+# script no longer carries per-worktree cache directories, a lock-retry
-# is a golangci-lint on PATH used directly - and then only if its
+# loop, or an output audit: there is no shared state left for them to
-# version is exactly the pin. Version equality alone is deliberately NOT
+# defend (issue https://git.eeqj.de/sneak/vaultik/issues/113).
-# enough: it also matches a developer's locally installed copy of the
-# same version, which is a different build with a different Go
-# toolchain, reached by a different code path, and it would bypass the
-# digest pin this script exists to enforce. /.dockerenv was considered
-# as the context signal and rejected: dockerd creates it for `docker
-# run`, but it is not reliably present during a BuildKit `docker build`,
-# which is exactly the case the exception exists for.
 #
-# The linter's output is checked before it is believed: every run is
+# To watch the linter execute, set BUILDKIT_PROGRESS=plain, which docker
-# audited by script/lint-audit for findings that cannot belong to this
+# honours directly:
-# tree, and a run refused by golangci-lint's cross-process lock is
-# retried rather than reported as a verdict. See the lock-retry loop in
-# main and the header of script/lint-audit.
 #
-# Extra arguments are passed through to `golangci-lint run`, before
+#   BUILDKIT_PROGRESS=plain script/lint
-# `./...` (see script/lint-fix).
+#
+# The check layers -- `golangci-lint config verify` and then
+# `golangci-lint run` -- must appear as executing rather than CACHED on
+# every run; see the CHECK_EPOCH comment in Dockerfile.lint.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-DOCKERFILE="$ROOT/Dockerfile"
+DOCKERFILE="$ROOT/Dockerfile.lint"
-
-# golangci-lint takes a cross-process lock and refuses to start while
-# another instance holds it. That refusal is not a lint result, and
-# exiting non-zero on it is indistinguishable to a caller from real
-# findings - so it is retried rather than reported. Bounded, because a
-# lock that is never released must fail rather than hang.
-LOCK_MESSAGE="parallel golangci-lint is running"
-LOCK_ATTEMPTS=6
-LOCK_SLEEP=15
-
-# The image reference of the Dockerfile's lint stage, tag and digest
-# included, e.g.
-# golangci/golangci-lint:v2.12.2-alpine@sha256:91b2...
-lint_image() {
-    awk '$1 == "FROM" && $3 == "AS" && $4 == "lint" { print $2; exit }' \
-        "$DOCKERFILE"
-}
-
-# The bare version that image reference pins, e.g. 2.12.2
-pinned_version() {
-    lint_image | sed -e 's/@.*//' -e 's/.*://' -e 's/^v//' -e 's/-.*//'
-}
-
-# The version of the golangci-lint on PATH, if any, e.g. 2.12.2
-#
-# `version --short` prints the bare version and is the interface meant
-# for this (checked against 2.10.1 and 2.12.2). The banner scrape below
-# it is a fallback for a release where --short is absent or silent; the
-# banner's exact wording is not a stable interface, which is why it is
-# no longer the primary parse.
-installed_version() {
-    command -v golangci-lint >/dev/null 2>&1 || return 0
-
-    short="$(golangci-lint version --short 2>/dev/null |
-        tr -d '[:space:]' | sed -e 's/^v//')"
-    case "$short" in
-        *[0-9].[0-9]*.[0-9]*)
-            echo "$short"
-            return 0
-            ;;
-    esac
-
-    golangci-lint version 2>/dev/null | awk '
-        {
-            for (i = 1; i <= NF; i++) {
-                if ($i ~ /^[0-9]+\.[0-9]+\.[0-9]+$/) {
-                    print $i
-                    exit
-                }
-            }
-        }'
-}
-
-# True inside the Dockerfile's lint stage, which sets this. Nothing else
-# sets it: setting it by hand on a host is an explicit, visible decision
-# to lint with an unpinned binary, not something reached by accident.
-in_lint_container() {
-    [ "${VAULTIK_LINT_IN_CONTAINER:-}" = "1" ]
-}
 
 require_docker() {
-    image="$1"
     if ! command -v docker >/dev/null 2>&1; then
         cat >&2 <<EOF
 lint: docker is required to run the pinned linter.
 
-  pinned image: $image
+  lint image declared by: $DOCKERFILE
 
 Install docker. Linting with any other golangci-lint is not supported:
-it is what lets a local run pass while CI fails. An installed
+it is what lets a local run pass while CI fails. A golangci-lint on
-golangci-lint on PATH is not used, whatever its version; only the lint
+PATH is never used, whatever its version.
-stage of the Dockerfile itself runs the linter natively.
 EOF
         exit 1
     fi
@@ -113,7 +45,7 @@ EOF
 lint: the docker daemon is not reachable, so the pinned linter cannot
 run.
 
-  pinned image: $image
+  lint image declared by: $DOCKERFILE
 
 Start the daemon (and check DOCKER_HOST / your group membership). This
 script will not fall back to a different linter version or to an
@@ -123,213 +55,54 @@ EOF
     fi
 }
 
-# Where the per-worktree caches live.
+usage() {
-cache_home() {
+    cat >&2 <<EOF
-    echo "${XDG_CACHE_HOME:-${HOME:-/tmp}/.cache}/vaultik-lint"
+usage: $(basename "$0")
-}
 
-# A short, stable digest of this worktree's path.
+script/lint takes no arguments. The linter runs as a build step, so
-path_digest() {
+there is no command line to pass flags to; anything accepted here would
-    if command -v sha256sum >/dev/null 2>&1; then
+have to be silently dropped. To apply autofixes, use script/lint-fix,
-        printf '%s' "$ROOT" | sha256sum | cut -c1-12
+which runs the same pinned image as a container for exactly this
-    elif command -v shasum >/dev/null 2>&1; then
+reason.
-        printf '%s' "$ROOT" | shasum -a 256 | cut -c1-12
+EOF
-    else
+    exit 2
-        printf '%s' "$ROOT" | cksum | tr -cd '0-9' | cut -c1-12
-    fi
-}
-
-# Caches for the containerized linter, private to THIS worktree.
-#
-# Keeping them out of the repo and persisting them between runs is what
-# keeps the inner loop fast: a warm run costs about the same as a native
-# one plus container startup. Keeping them keyed on the worktree path is
-# what keeps them correct. One shared cache for the whole repo was the
-# defect in issue #99: two worktrees of this repo have identical file
-# contents, so their cache keys collide, and golangci-lint replays the
-# stored results - including the file paths recorded when they were
-# produced. That silently reports one worktree's findings, or one
-# worktree's clean bill of health, for another.
-cache_dir() {
-    slug="$(printf '%s' "$(basename "$ROOT")" | tr -c 'A-Za-z0-9._-' '-')"
-    echo "$(cache_home)/$slug-$(path_digest)"
-}
-
-# One cache per worktree means throwaway worktrees would otherwise leave
-# caches behind forever. Each cache records the worktree it belongs to,
-# and any cache whose worktree no longer exists is collected here, so
-# growth is bounded by the number of worktrees that actually exist. The
-# whole tree also sits under XDG_CACHE_HOME (~/.cache by default), so it
-# is disposable by definition: `rm -rf "${XDG_CACHE_HOME:-~/.cache}/vaultik-lint"`
-# costs nothing but the next run's cold cache.
-prune_dead_caches() {
-    home="$(cache_home)"
-    if [ ! -d "$home" ]; then
-        return 0
-    fi
-    for dir in "$home"/*; do
-        if [ ! -f "$dir/worktree" ]; then
-            continue
-        fi
-        owner="$(cat "$dir/worktree")"
-        if [ -z "$owner" ]; then
-            continue
-        fi
-        if [ ! -d "$owner" ]; then
-            # The Go module cache inside is deliberately read-only, and
-            # rm(1) cannot unlink a file out of a directory it may not
-            # write, so the tree has to be made writable first. And
-            # failing to tidy up is a housekeeping problem, never a
-            # reason to fail a lint: without the fallback below, `set
-            # -e` turns a stale cache that will not delete into a lint
-            # error, which is a gate failing for a reason that has
-            # nothing to do with the code. (Observed, not theorised.)
-            chmod -R u+w "$dir" 2>/dev/null || true
-            if ! rm -rf "$dir" 2>/dev/null; then
-                # Restore the marker on a partial removal: an
-                # unmarked leftover would be skipped by every future
-                # run and never collected.
-                mkdir -p "$dir" 2>/dev/null || true
-                echo "$owner" >"$dir/worktree" 2>/dev/null || true
-                echo "lint: could not remove stale cache $dir" >&2
-            fi
-        fi
-    done
-}
-
-prepare_cache() {
-    cache="$1"
-    mkdir -p "$cache/go-build" "$cache/go-mod" "$cache/golangci-lint"
-    echo "$ROOT" >"$cache/worktree"
-}
-
-# Run the linter, wherever it is that this script is allowed to run it.
-run_linter() {
-    if in_lint_container; then
-        golangci-lint run "$@" ./...
-        return $?
-    fi
-
-    docker run --rm \
-        --user "$(id -u):$(id -g)" \
-        --env HOME=/tmp \
-        --env GOFLAGS=-buildvcs=false \
-        --env GOCACHE=/cache/go-build \
-        --env GOMODCACHE=/cache/go-mod \
-        --env GOLANGCI_LINT_CACHE=/cache/golangci-lint \
-        --volume "$ROOT:/src" \
-        --volume "$CACHE:/cache" \
-        --workdir /src \
-        "$IMAGE" \
-        golangci-lint run "$@" ./...
-}
-
-# Run the linter, streaming its combined output while also capturing it,
-# and hand back its exit status. The output has to be inspected before
-# it is believed, which is why this script no longer just execs the
-# linter. `tee` would swallow the status, so it is smuggled out through
-# a file: there is no pipefail in POSIX sh.
-run_capture() {
-    capture="$1"
-    shift
-    rm -f "$capture.status"
-    {
-        rc=0
-        # `set -e` is in force inside this subshell too, so the status
-        # has to be caught here: an unguarded non-zero exit (which is
-        # what "the linter found something" looks like) would abort the
-        # subshell before the status was ever written.
-        run_linter "$@" 2>&1 || rc=$?
-        echo "$rc" >"$capture.status"
-    } | tee "$capture"
-
-    if [ ! -s "$capture.status" ]; then
-        echo "lint: the linter did not report an exit status" >&2
-        exit 1
-    fi
-    read -r captured_status <"$capture.status"
-    rm -f "$capture.status"
-    return "$captured_status"
-}
-
-# Reject output that cannot describe this tree. See script/lint-audit
-# for what that means and why: in short, a finding citing a file that is
-# not here means the result being reported was produced somewhere else,
-# and a PASS built out of another checkout's analysis is silent (issue
-# #99). The audit therefore runs on clean output as well.
-audit_output() {
-    capture="$1"
-    if ! "$ROOT/script/lint-audit" "$capture"; then
-        if [ -n "$CACHE" ]; then
-            echo "  this tree's lint cache: $CACHE" >&2
-        fi
-        exit 1
-    fi
 }
 
 main() {
+    [ "$#" -eq 0 ] || usage
+
     cd "$ROOT"
+    require_docker
 
-    IMAGE="$(lint_image)"
+    # A fresh epoch per invocation is what forces the check layers to
-    if [ -z "$IMAGE" ]; then
+    # execute; the layers above the ARG in Dockerfile.lint still cache,
-        echo "lint: no lint stage found in $DOCKERFILE" >&2
+    # so a run is not cold. The value must be unique per invocation, not
-        exit 1
+    # per second: `date +%s` is second-granular, so two concurrent
-    fi
+    # invocations in the same second would get identical epochs and the
+    # later one could be served from cache -- the false green in
+    # miniature. `%N` alone does not fix it either, because busybox
+    # silently drops %N, exits 0, and hands back second granularity with
+    # no warning. `$$` is what makes this correct regardless, since
+    # concurrent invocations have different pids.
+    #
+    # Assign it on its own line rather than inline in the argument.
+    # Under `set -eu` a command substitution that fails inside an
+    # argument does NOT abort the script: CHECK_EPOCH would become an
+    # empty string, an empty string is a constant, and a constant epoch
+    # is exactly the cached-lint false green this guards against. As a
+    # bare assignment, `set -e` catches a failing `date` and no build
+    # starts.
+    epoch="$(date +%s%N)$$"
 
-    CACHE=""
+    # cacheonly: the lint verdict is the build's exit status, and the
-    if in_lint_container; then
+    # image it would otherwise produce is never run. Exporting it costs
-        # No docker daemon in here, so there is no fallback: a mismatch
+    # most of the wall time of a warm run and leaves a dangling image
-        # is a hard error rather than a quiet substitution.
+    # behind on every invocation, on a host that may be running many.
-        installed="$(installed_version)"
+    docker build \
-        pinned="$(pinned_version)"
+        --output=type=cacheonly \
-        if [ -z "$installed" ] || [ "$installed" != "$pinned" ]; then
+        --build-arg CHECK_EPOCH="$epoch" \
-            cat >&2 <<EOF
+        -f "$DOCKERFILE" \
-lint: VAULTIK_LINT_IN_CONTAINER is set, so this is expected to be
+        "$ROOT"
-running inside the Dockerfile's pinned lint image, but the golangci-lint
-on PATH does not match the pin.
-
-  pinned:    $pinned ($IMAGE)
-  installed: ${installed:-<none>}
-EOF
-            exit 1
-        fi
-    else
-        require_docker "$IMAGE"
-        prune_dead_caches
-        CACHE="$(cache_dir)"
-        prepare_cache "$CACHE"
-    fi
-
-    capture="$(mktemp "${TMPDIR:-/tmp}/vaultik-lint.XXXXXX")"
-    trap 'rm -f "$capture" "$capture.status"' EXIT HUP INT TERM
-
-    attempt=1
-    while :; do
-        status=0
-        run_capture "$capture" "$@" || status=$?
-
-        if grep -Fq "$LOCK_MESSAGE" "$capture"; then
-            if [ "$attempt" -lt "$LOCK_ATTEMPTS" ]; then
-                echo "lint: another golangci-lint holds the lock;" \
-                    "retrying in ${LOCK_SLEEP}s" \
-                    "(attempt $attempt of $LOCK_ATTEMPTS)" >&2
-                sleep "$LOCK_SLEEP"
-                attempt=$((attempt + 1))
-                continue
-            fi
-            cat >&2 <<EOF
-
-lint: gave up after $LOCK_ATTEMPTS attempts, each blocked by another
-golangci-lint holding the cross-process lock. This is NOT a lint
-verdict: the tree was never analysed. Re-run when the other run has
-finished.
-EOF
-            exit 1
-        fi
-
-        audit_output "$capture"
-        exit "$status"
-    done
 }
 
 main "$@"

script/lint-audit

@@ -1,113 +0,0 @@
-#!/bin/sh
-# script/lint-audit: audit a captured golangci-lint run for output that
-# cannot describe this tree. Called by script/lint on every run; usable
-# on its own against any saved lint output.
-#
-#   script/lint-audit <capture-file>
-#
-# Exits 0 when every finding cites a file in this tree, 1 when any does
-# not. It NEVER certifies that a lint run passed - it has no idea
-# whether the run found issues, and does not look. It only rejects
-# output that is impossible for this tree, which is a different and much
-# weaker claim. Do not use it as a gate; use script/lint.
-#
-# Why this exists (issue #99): golangci-lint caches analysis results,
-# and a cache shared between two checkouts of this repo can serve one
-# checkout's stored findings for another, file paths included. The
-# failure is symmetric and only one direction is loud - a clean tree
-# failed by a dirty sibling gets investigated, while a dirty tree passed
-# by a clean sibling is silent. This turns the silent direction into a
-# hard error, which is why it runs on clean output too.
-#
-# The primary fix is that script/lint now keys its cache on the worktree
-# path so the collision cannot happen. This is the backstop, because a
-# backstop that only runs when we already believe things are fine is
-# worth more than one more assumption.
-set -eu
-
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-
-# Where script/lint bind-mounts the tree inside the pinned image. A
-# containerized run that prints absolute paths (`--path-mode abs`)
-# prints them under this, so they are this tree's files under another
-# name. Note the consequence, and why the cache key rather than this
-# check is the real fix: two containerized runs of different checkouts
-# both call themselves /src, so contamination between two container
-# runs is not distinguishable by path alone.
-CONTAINER_ROOT="/src"
-
-usage() {
-    echo "usage: $(basename "$0") <capture-file>" >&2
-    exit 2
-}
-
-# Every path cited by a finding that is not a file in this tree.
-#
-# The linter runs with the tree root as its working directory, so a
-# legitimate finding cites either a relative path that resolves inside
-# the tree or an absolute path under the root. A path that escapes
-# (absolute and elsewhere, or with a `..` component) or that names a
-# file which is not here describes something this run did not analyse.
-foreign_paths() {
-    capture="$1"
-    awk -F: '$1 ~ /\.go$/ && $2 ~ /^[0-9]+$/ { print $1 }' "$capture" |
-        sort -u |
-        while IFS= read -r path; do
-            case "$path" in
-                "$ROOT"/*)
-                    path="${path#"$ROOT"/}"
-                    ;;
-                "$CONTAINER_ROOT"/*)
-                    path="${path#"$CONTAINER_ROOT"/}"
-                    ;;
-                /*)
-                    printf '%s\n' "$path"
-                    continue
-                    ;;
-                ../* | */../*)
-                    printf '%s\n' "$path"
-                    continue
-                    ;;
-            esac
-            if [ ! -e "$ROOT/$path" ]; then
-                printf '%s\n' "$path"
-            fi
-        done
-}
-
-main() {
-    [ "$#" -eq 1 ] || usage
-    capture="$1"
-    if [ ! -f "$capture" ]; then
-        echo "lint-audit: no such capture file: $capture" >&2
-        exit 2
-    fi
-
-    foreign="$(foreign_paths "$capture")"
-    if [ -z "$foreign" ]; then
-        exit 0
-    fi
-
-    cat >&2 <<EOF
-
-lint: REJECTED - the linter reported findings for files that are not in
-this tree, so its output does not describe the tree that was linted.
-This result is void, whichever way it went: a pass here would be a pass
-earned by analysing someone else's code.
-
-  tree: $ROOT
-
-Paths reported that are not in this tree:
-EOF
-    printf '%s\n' "$foreign" | sed -e 's/^/  /' >&2
-    cat >&2 <<EOF
-
-This is the signature of analysis replayed from a cache belonging to
-another checkout (issue #99). Clear this tree's lint cache and re-run:
-
-  rm -rf "\${XDG_CACHE_HOME:-\$HOME/.cache}/vaultik-lint"
-EOF
-    exit 1
-}
-
-main "$@"

script/lint-fix

@@ -1,18 +1,54 @@
 #!/bin/sh
 # script/lint-fix: run the linter's autofixer. Rewrites files in place
 # for every finding the enabled linters know how to fix; findings
-# without an autofix are reported but left alone (exit status is
+# without an autofix are reported but left alone.
-# nonzero while any remain).
 #
-# Delegates to script/lint so the autofixer is the same pinned linter
+# THIS IS A DEVELOPER CONVENIENCE AND NEVER A GATE. Nothing in
-# version that script/lint and CI use - fixes written by a different
+# script/check, script/precommit or script/cibuild calls it, and no gate
-# version are not necessarily fixes for the version that gates.
+# reads its exit status. The gate is script/lint, which builds
+# Dockerfile.lint; run that afterwards to find out whether the tree is
+# actually clean.
+#
+# Unlike script/lint this cannot be a build step: a build step writes
+# into an image, and fixes have to land in the worktree. So it runs the
+# same pinned image as a container with the tree bind-mounted, which
+# means it needs a LOCAL docker daemon -- a remote daemon has no access
+# to these files, and this script will appear to do nothing there. The
+# image reference is parsed out of Dockerfile.lint's FROM line, so the
+# autofixer is always the same version as the linter that gates; fixes
+# written by a different version are not necessarily fixes for the
+# version that decides.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+DOCKERFILE="$ROOT/Dockerfile.lint"
+
+# The image reference from Dockerfile.lint, tag and digest included.
+lint_image() {
+    awk '$1 == "FROM" { print $2; exit }' "$DOCKERFILE"
+}
 
 main() {
-    exec "$SCRIPT_DIR/lint" --fix "$@"
+    cd "$ROOT"
+
+    image="$(lint_image)"
+    if [ -z "$image" ]; then
+        echo "lint-fix: no FROM line found in $DOCKERFILE" >&2
+        exit 1
+    fi
+
+    # Run as the invoking user so the rewritten files stay owned by
+    # them. HOME is set because the Go and golangci-lint caches default
+    # under it and that user has no home inside the container; those
+    # caches are per-container and discarded with it.
+    docker run --rm \
+        --user "$(id -u):$(id -g)" \
+        --env HOME=/tmp \
+        --env GOFLAGS=-buildvcs=false \
+        --volume "$ROOT:/src" \
+        --workdir /src \
+        "$image" \
+        golangci-lint run --config .golangci.yml --fix "$@" ./...
 }
 
 main "$@"

test-config.yml

@@ -1,27 +0,0 @@
-# Vaultik test configuration
-hostname: test-host
-index_path: /tmp/vaultik-test/index.db
-source_dirs:
-  - /tmp/vaultik-test/source
-
-# S3 configuration
-s3:
-  endpoint: http://localhost:19000  # gofakes3 test endpoint
-  bucket: test-bucket
-  prefix: test-
-  access_key_id: test-key
-  secret_access_key: test-secret
-  region: us-east-1
-
-# Chunking configuration
-chunk_size: 65536  # 64KB average chunk size
-min_chunk_size: 32768  # 32KB minimum
-max_chunk_size: 131072  # 128KB maximum
-blob_size: 1048576  # 1MB blobs for testing
-
-# Compression
-compression_level: 3
-
-# Encryption
-# age_recipients:
-#   - age1qyqszqgpqyqszqgpqyqszqgpqyqszqgpqyqszqgpqyqszqgpqyqs3mw88h

test/integration-config.yml

@@ -1,24 +0,0 @@
-age_recipients:
-  - age1278m9q7dp3chsh2dcy82qk27v047zywyvtxwnj4cvt0z65jw6a7q5dqhfj  # sneak's long term age key
-  - age1ezrjmfpwsc95svdg0y54mums3zevgzu0x0ecq2f7tp8a05gl0sjq9q9wjg  # insecure integration test key
-source_dirs:
-  - /tmp/vaultik-test-source
-exclude:
-  - '*.log'
-  - '*.tmp'
-  - '.git'
-  - 'node_modules'
-s3:
-  endpoint: http://ber1app1.local:3900/
-  bucket: vaultik-integration-test
-  prefix: test-host/
-  access_key_id: GKbc8e6d35fdf50847f155aca5
-  secret_access_key: 217046bee47c050301e3cc13e3cba1a8a943cf5f37f8c7979c349c5254441d18
-  region: us-east-1
-  use_ssl: false
-  part_size: 5242880  # 5MB
-index_path: /tmp/vaultik-integration-test.sqlite
-chunk_size: 10MB
-blob_size_limit: 10GB
-compression_level: 3
-hostname: test-host