Add a read-only Settings page for the loaded configuration (closes #402)

The page at /settings, behind the login and linked from the
navigation bar, lists every field of the configuration the server
started with: each by its environment variable name, with the
README's description and the value in effect. METRICS_PASSWORD and
SENTRY_DSN show only as set or not set; their values never reach the
template. The handlers now take the loaded Config from the dependency
graph.

Model: opus-5-5

.dockerignore

@@ -3,10 +3,8 @@
 # stage of the Dockerfile.
 .git/
 bin/
-# Third-party browser assets are fetched and hash-verified inside the build by
-# script/fetch-assets. Excluding any host copy keeps a developer's working tree
-# from supplying the bytes that get shipped. The script and its
-# static/vendor.sha256 manifest stay in the context.
+# Extracted from 3p/ by `make assets` inside the build; a host copy is not
+# needed. The tarball in 3p/ must stay in the context.
 static/js/alpine.min.js
 *.md
 LICENSE

.gitignore

@@ -46,7 +46,6 @@ temp/
 # CI cache barrier, written into the build context by the check workflow
 .ci-fingerprint
 
-# Third-party browser assets, fetched and hash-verified by
-# script/fetch-assets against static/vendor.sha256. Not committed:
-# REPO_POLICIES.md forbids minified bundles in version control.
-/static/js/alpine.min.js 
+# Alpine.js, extracted by `make assets` from its tarball in 3p/, which is
+# what is committed.
+/static/js/alpine.min.js

Dockerfile

@@ -51,15 +51,8 @@ RUN go mod download
 # the lint stage above.
 COPY . .
 
-# Fetch the third-party browser assets the UI serves. They are not committed
-# (REPO_POLICIES.md forbids minified bundles in version control) and
-# .dockerignore keeps any host copy out of the build context, so this step is
-# the only way they enter the image. Each download is checked against a
-# hardcoded sha256 and the build fails on mismatch; make test re-checks the
-# hashes against the bytes go:embed actually put in the binary.
-RUN script/fetch-assets
-
-# Run tests and build
+# Run tests and build. Both first run script/assets, which extracts Alpine.js
+# from its tarball in 3p/.
 RUN make test
 
 # Version stamped into the binary. .dockerignore excludes .git/, so
@@ -67,8 +60,8 @@ RUN make test
 # host and passes it in. The default is what a bare `docker build .`
 # with no --build-arg gets, and it names no tag the tree may not be at.
 #
-# Declared here, below the test and asset steps, so a changed version
-# does not invalidate their cached layers.
+# Declared here, below the test step, so a changed version does not
+# invalidate its cached layer.
 ARG VERSION=unknown
 
 RUN make build VERSION="$VERSION"

Makefile

@@ -28,7 +28,7 @@ setup:
 	@script/setup
 
 assets:
-	@script/fetch-assets
+	@script/assets
 
 test:
 	@script/test
@@ -45,13 +45,13 @@ fmt-check:
 check:
 	@script/check
 
-build:
+build: assets
 	go build -ldflags '$(strip -X main.version=$(VERSION) $(GO_LDFLAGS))' -o bin/webhooker ./cmd/webhooker
 
 run: build
 	./bin/webhooker
 
-dev:
+dev: assets
 	go run ./cmd/webhooker
 
 deps:

README.md

@@ -21,9 +21,6 @@ before deploying one.
 - Go 1.26.1+ (the version in `go.mod`)
 - Docker (for linting, for the test stage of the CI gate, and for
   containerized deployment)
-- `curl`, used by `script/fetch-assets` to download the third-party
-  browser assets, which are not committed (`make bootstrap` installs
-  it if missing)
 
 golangci-lint is not a prerequisite and must not be installed on the
 host: `script/bootstrap` does not install it, and `make lint` runs the
@@ -36,9 +33,7 @@ digest-pinned linter image via `Dockerfile.lint`.
 git clone https://git.eeqj.de/sneak/webhooker.git
 cd webhooker
 
-# Install Go dependencies and the third-party browser assets.
-# `make deps` alone is not enough: it only runs go mod download/tidy,
-# and the checks below need the fetched assets.
+# Install the Go toolchain if missing, and the Go dependencies
 make bootstrap
 
 # Run all checks (test, lint, format check)
@@ -58,7 +53,7 @@ make docker
 ```bash
 make bootstrap  # Install all dependencies (idempotent)
 make setup      # Bootstrap + install git pre-commit hook
-make assets     # Fetch + verify third-party browser assets
+make assets     # Extract Alpine.js from 3p/ (test, check, build, dev run it)
 make fmt        # Format code (gofmt + goimports)
 make fmt-check  # Fail if gofmt would change anything (writes nothing)
 make lint       # Run golangci-lint in Docker (Dockerfile.lint)
@@ -150,6 +145,11 @@ TTY detection, and security headers are always applied.
 | `TRUSTED_PROXIES`       | CIDRs whose forwarded headers are trusted (unset: all clients behind a proxy share one rate-limit bucket; a correct login password is never throttled either way) | `""` (none) |
 | `ALLOWED_EGRESS_CIDRS`  | CIDRs that delivery targets may reach despite the SSRF blocklist. Read [Allowing egress to your own network](#allowing-egress-to-your-own-network) before setting it | `""` (none) |
 
+The Settings page of the web UI (`/settings`, behind the login) lists
+every one of these with the value the running server loaded. It is
+read-only, and it shows `METRICS_PASSWORD` and `SENTRY_DSN` only as
+set or not set, never their values.
+
 #### Allowing egress to your own network
 
 By default every delivery target must resolve to a public address. The
@@ -1221,14 +1221,15 @@ This repository adheres to the
 standard: normalized scripts in `script/` are the entrypoints for the
 development workflow. Ten of the Makefile's seventeen targets are thin
 shims that call them; `build`, `run`, `dev`, `deps`, `clean`, `css` and
-`version` are inline commands with no script behind them, though
-`build` and `version` both take their value from `script/version`.
+`version` are inline commands with no script behind them, though `build`,
+`run` and `dev` first run `script/assets`, and `build` and `version` both
+take their value from `script/version`.
 
-`make check` needs the third-party browser assets in `static/`, which
-are not committed, so run `make bootstrap` (or just `make assets`) once
-after cloning. Without them the tests fail with a message naming that
-remedy. `make check` does not fetch them itself because it must not
-change any files in the repo.
+`script/test`, `make build` and `make dev` each run `script/assets`
+first, which writes the ignored `static/js/alpine.min.js` (see
+[Third-party browser assets](#third-party-browser-assets)), so
+`make test`, `make check` and the pre-commit hook work on a fresh clone
+without a separate step.
 
 We provide:
 
@@ -1236,8 +1237,8 @@ We provide:
 - `script/setup` — make a fresh clone ready for development
   (bootstrap, then install-precommit)
 - `script/projectname` — output the project name ("webhooker")
-- `script/fetch-assets` — download the third-party browser assets into
-  `static/`, verifying each against its pinned sha256
+- `script/assets` — extract Alpine.js from its tarball in `3p/` (see
+  [Third-party browser assets](#third-party-browser-assets))
 - `script/test` — run the test suite
 - `script/lint` — run golangci-lint in Docker (see Linting below)
 - `script/fmt` — format all code (writes)
@@ -1259,24 +1260,25 @@ We provide:
 
 ## Third-party browser assets
 
-The web UI serves one third-party script, Alpine.js. It is **not** committed:
-a minified bundle in the tree is unreviewable, and `REPO_POLICIES.md` bars
-both committed build artifacts and unpinned external references.
+The web UI serves one third-party script, Alpine.js. Its npm package tarball
+is committed as `3p/alpinejs-3.14.9.tgz`, byte for byte as the npm registry
+publishes it. It is a dependency, not this repo's build output, so
+`REPO_POLICIES.md`'s rule against committed build artifacts does not apply.
+The directory is `3p/` rather than `vendor/` because Go treats a root
+`vendor/` directory as its module vendor directory.
 
-Instead `script/fetch-assets` downloads it from a pinned URL, checks the
-download against a hardcoded sha256, and installs it under `static/`. The
-sha256 of every installed asset is recorded in `static/vendor.sha256`, and
-`static/vendor_test.go` re-hashes the bytes `go:embed` put in the binary
-against that manifest — so the pin is enforced on what actually ships, not
-merely written down. Any mismatch fails the build.
+`script/assets` (`make assets`) extracts the browser build,
+`package/dist/cdn.min.js`, from the tarball to `static/js/alpine.min.js`,
+where `go:embed` picks it up. `script/test`, `make build` and `make dev` run
+it first, and the Dockerfile builds through `make test` and `make build`, so
+nothing downloads Alpine.js. The extracted file is not committed, and
+`.dockerignore` keeps any host copy out of the build context.
 
-`make bootstrap` runs the fetch for local development, and the Dockerfile
-runs it in the build stage; `.gitignore` and `.dockerignore` keep the
-artifact out of both the repo and the build context.
-
-To move to a new version: update the version, URL, and tarball sha256 in
-`script/fetch-assets` and the asset sha256 in `static/vendor.sha256`, then
-run `make assets && make check`.
+To move to a new version: download
+`https://registry.npmjs.org/alpinejs/-/alpinejs-<version>.tgz`, check it
+against the `dist.integrity` hash listed at
+`https://registry.npmjs.org/alpinejs/<version>`, replace the tarball in `3p/`
+with it, update its file name in `script/assets`, and run `make check`.
 
 ## Rationale
 
@@ -1439,7 +1441,7 @@ A registered user of the webhooker service.
 | Field      | Type     | Description |
 | ---------- | -------- | ----------- |
 | `id`       | UUID     | Primary key |
-| `username` | string   | Unique login name |
+| `username` | string   | Unique login name, at most 1024 bytes so that it fits in the session cookie |
 | `password` | string   | Argon2id hash (never exposed via API) |
 
 **Relations:** Has many Webhooks. Has many APIKeys.
@@ -2379,14 +2381,14 @@ Removing either cap fails 14 subtests.
 
 `internal/middleware/logbound_test.go` and
 `internal/handlers/logbound_test.go` drive 8 KB of client-chosen text
-at each of these — 1 KB at `invalid password`, whose accounts are
-shared with the successful-login line, where a username past 4 KB
-overflows the session cookie and answers 500 before that line is
-written — through both handlers, and through seven fills: plain text
-as the baseline, and then the quotation mark, backslash, tab, newline,
-C0 control and astral non-printable, six characters the wider of the
-two handlers spends more on than the client spent sending them. Every
-case holds each line to the 2,560-byte ceiling. That per-line ceiling
+at each of these — just under 1 KB at `invalid password`, whose
+accounts are shared with the successful-login line and so must stay
+within the 1024-byte username limit — through both handlers, and
+through seven fills: plain text as the baseline, and then the
+quotation mark, backslash, tab, newline, C0 control and astral
+non-printable, six characters the wider of the two handlers spends
+more on than the client spent sending them. Every case holds each
+line to the 2,560-byte ceiling. That per-line ceiling
 is what the figure above states, and every row establishes it.
 
 Three of the sites go further and bound the whole flood's output — the
@@ -2705,6 +2707,7 @@ abuse limit later; they are tracked as future work.
 | ------ | ------------------------ | ----------- |
 | `GET`  | `/user/{username}`       | User profile page |
 | `POST` | `/user/{username}/password` | Change the user's password (5 per minute per bucket, then `429`; `503` if no verification slot frees up within 5s, or immediately if 16 requests are already queued for one) |
+| `GET`  | `/settings`              | Read-only list of the configuration the server is running with; `METRICS_PASSWORD` and `SENTRY_DSN` show only as set or not set |
 | `GET`  | `/sources`               | List user's webhooks |
 | `GET`  | `/sources/new`           | Create webhook form |
 | `POST` | `/sources/new`           | Create webhook submission |
@@ -2755,6 +2758,8 @@ imports. The entry point is `cmd/webhooker/main.go`.
 
 ```
 webhooker/
+├── 3p/
+│   └── alpinejs-3.14.9.tgz    # Alpine.js npm package, extracted by make assets
 ├── cmd/webhooker/
 │   └── main.go               # Entry point: subcommand dispatch; no args locks DATA_DIR and wires fx
 ├── internal/
@@ -2815,6 +2820,7 @@ webhooker/
 │   │   ├── healthcheck.go     # Health check handler
 │   │   ├── index.go           # Index page handler
 │   │   ├── profile.go         # User profile handler
+│   │   ├── settings.go        # Read-only Settings page handler
 │   │   ├── source_management.go  # Webhook CRUD handlers
 │   │   └── webhook.go         # Webhook receiver handler
 │   ├── healthcheck/
@@ -2848,8 +2854,7 @@ webhooker/
 │   ├── css/tailwind.css       # Generated stylesheet the pages load
 │   ├── css/style.css          # Older hand-written stylesheet, no longer loaded
 │   ├── js/app.js              # Progressive-enhancement copy-to-clipboard
-│   ├── js/alpine.min.js       # Alpine.js, fetched by script/fetch-assets, not committed
-│   └── vendor.sha256          # Pinned hashes the fetched assets are verified against
+│   └── js/alpine.min.js       # Alpine.js, extracted from 3p/ by make assets, not committed
 ├── templates/                 # Go HTML templates (base, login, sources, etc.)
 ├── script/                    # Scripts to Rule Them All entrypoints
 ├── Dockerfile                 # Three stages: lint, test+build, Alpine runtime
@@ -3161,14 +3166,14 @@ version is fixed independently of the compiler's:
    `make fmt-check`, then `golangci-lint config verify` and
    `golangci-lint run`, both with `--network=none`.
 2. **Builder stage** (`golang:1.26.1-bookworm`) — depends on the lint
-   stage passing (it copies a file from it), runs `script/fetch-assets`
-   to download and verify the third-party browser assets, then runs
-   `make test` and `make build`, and finally rebuilds the binary with
-   `CGO_ENABLED=1` and static linking so it runs on musl. Both builds
-   go through `make build`, the relink adding its `-extldflags` via
-   `GO_LDFLAGS`, so neither can drop the `-X` that stamps the version.
-   The version arrives as the `VERSION` build arg, since the context
-   has no `.git` (see [Version stamping](#version-stamping)).
+   stage passing (it copies a file from it), runs `make test` and
+   `make build` (both extract Alpine.js from `3p/` first), and finally
+   rebuilds the binary with `CGO_ENABLED=1` and static linking so it
+   runs on musl. Both builds go through `make build`, the relink adding
+   its `-extldflags` via `GO_LDFLAGS`, so neither can drop the `-X` that
+   stamps the version. The version arrives as the `VERSION` build arg,
+   since the context has no `.git` (see
+   [Version stamping](#version-stamping)).
 3. **Runtime stage** (`alpine:3.21`) — copies the static binary and
    `deploy/docker-entrypoint.sh`, creates the `/var/lib/webhooker`
    directory for all SQLite databases, exposes port 8080, and includes

internal/database/model_user.go

@@ -1,13 +1,58 @@
 package database
 
+import (
+	"errors"
+	"fmt"
+
+	"gorm.io/gorm"
+)
+
+// MaxUsernameBytes is the longest username, in bytes, that a user may
+// have. The same number appears in the check constraint on
+// User.Username, because a struct tag cannot reference a constant.
+//
+// A login stores the username in the session cookie, and both
+// securecookie and browsers refuse a cookie value past about 4096
+// bytes. That value is the session base64-encoded twice, so it holds
+// 4096 × 3/4 × 3/4 = 2304 bytes of session, and the signature,
+// timestamp and the session's other values take about 270 of those: a
+// username longer than about 2030 bytes can never log in. The limit is
+// about half that, so the session can carry more values later without
+// locking out an account whose username is already at the limit.
+const MaxUsernameBytes = 1024
+
+// ErrUsernameTooLong is returned when a user is saved with a username
+// longer than MaxUsernameBytes.
+var ErrUsernameTooLong = errors.New("username is too long")
+
 // User represents a user of the webhooker service
+//
+//nolint:lll // a struct tag cannot wrap
 type User struct {
 	BaseModel
 
-	Username string `gorm:"uniqueIndex;not null" json:"username"`
-	Password string `gorm:"not null"             json:"-"` // Argon2 hashed
+	Username string `gorm:"uniqueIndex;not null;check:length(CAST(username AS BLOB)) <= 1024" json:"username"`
+	Password string `gorm:"not null"                                                          json:"-"` // Argon2 hashed
 
 	// Relations
 	Webhooks []Webhook `json:"webhooks,omitempty"`
 	APIKeys  []APIKey  `json:"apiKeys,omitempty"`
 }
+
+// BeforeSave rejects a username longer than MaxUsernameBytes when a whole
+// User is created or saved, so those calls get ErrUsernameTooLong rather
+// than the database's constraint error. A column update such as
+// Update("username", ...) is caught only by the check constraint, as is
+// any path that writes the table without this model.
+func (u *User) BeforeSave(_ *gorm.DB) error {
+	if len(u.Username) > MaxUsernameBytes {
+		return fmt.Errorf(
+			"%w: %d bytes, limit is %d",
+			ErrUsernameTooLong,
+			len(u.Username),
+			MaxUsernameBytes,
+		)
+	}
+
+	return nil
+}

internal/database/model_user_test.go

@@ -0,0 +1,65 @@
+package database_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// usernameAtLimit is exactly MaxUsernameBytes long, built from a
+// two-byte character. A check that counted characters rather than bytes
+// would see half the length and let the one-byte-longer name through.
+func usernameAtLimit() string {
+	return strings.Repeat("é", database.MaxUsernameBytes/2)
+}
+
+func TestUserCreate_RejectsOverlongUsername(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	err := db.Create(&database.User{
+		Username: usernameAtLimit() + "x",
+		Password: "hash",
+	}).Error
+
+	require.ErrorIs(t, err, database.ErrUsernameTooLong)
+}
+
+func TestUserCreate_AcceptsUsernameAtLimit(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	require.NoError(t, db.Create(&database.User{
+		Username: usernameAtLimit(),
+		Password: "hash",
+	}).Error)
+}
+
+// TestUsersTable_EnforcesUsernameLimitWithoutTheModel inserts with raw
+// SQL, as a path that bypassed User.BeforeSave would, so only the
+// table's check constraint stands between it and an over-long
+// username. Accepting the name at the limit and refusing the next byte
+// also pins the constraint's number to MaxUsernameBytes.
+func TestUsersTable_EnforcesUsernameLimitWithoutTheModel(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	insert := "INSERT INTO users (id, username, password) VALUES (?, ?, ?)"
+
+	require.NoError(t, db.Exec(
+		insert, uuid.New().String(), usernameAtLimit(), "hash",
+	).Error)
+
+	err := db.Exec(
+		insert, uuid.New().String(), usernameAtLimit()+"x", "hash",
+	).Error
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "CHECK constraint failed")
+}

internal/handlers/auth_test.go

@@ -453,3 +453,33 @@ func TestLogin_SuccessCreatesSession(t *testing.T) {
 		"the issued cookie must carry an authenticated session",
 	)
 }
+
+// TestLogin_UsernameAtLimitCanLogIn shows that a username of exactly
+// database.MaxUsernameBytes still fits in the session cookie. Past
+// what the cookie can carry, a correct login answers 500.
+func TestLogin_UsernameAtLimitCanLogIn(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h  *handlers.Handlers
+		db *database.Database
+	)
+
+	app := newTestApp(t, &h, &db)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	username := strings.Repeat("a", database.MaxUsernameBytes)
+
+	hash, err := database.HashPassword(operatorPassword)
+	require.NoError(t, err)
+	require.NoError(t, db.DB().Create(&database.User{
+		Username: username,
+		Password: hash,
+	}).Error)
+
+	w := submitLogin(h, sharedProxyPeer, username, operatorPassword)
+
+	assert.Equal(t, http.StatusSeeOther, w.Code)
+}

internal/handlers/handlers.go

@@ -13,6 +13,7 @@ import (
 	"sync/atomic"
 
 	"go.uber.org/fx"
+	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
 	"sneak.berlin/go/webhooker/internal/globals"
@@ -53,6 +54,7 @@ type HandlersParams struct {
 
 	Logger       *logger.Logger
 	Globals      *globals.Globals
+	Config       *config.Config
 	Database     *database.Database
 	WebhookDBMgr *database.WebhookDBManager
 	Healthcheck  *healthcheck.Healthcheck
@@ -129,6 +131,7 @@ func New(
 	s.templates = map[string]*template.Template{
 		"login.html":         parsePageTemplate("login.html"),
 		"profile.html":       parsePageTemplate("profile.html"),
+		"settings.html":      parsePageTemplate("settings.html"),
 		"sources_list.html":  parsePageTemplate("sources_list.html"),
 		"sources_new.html":   parsePageTemplate("sources_new.html"),
 		"source_detail.html": parsePageTemplate("source_detail.html"),

internal/handlers/handlers_test.go

@@ -83,16 +83,25 @@ func newTestApp(
 ) *fxtest.App {
 	t.Helper()
 
+	return newTestAppWithConfig(
+		t, &config.Config{DataDir: t.TempDir()}, targets...,
+	)
+}
+
+// newTestAppWithConfig is newTestApp over a caller-supplied Config.
+func newTestAppWithConfig(
+	t *testing.T,
+	cfg *config.Config,
+	targets ...any,
+) *fxtest.App {
+	t.Helper()
+
 	return fxtest.New(
 		t,
 		fx.Provide(
 			globals.New,
 			logger.New,
-			func() *config.Config {
-				return &config.Config{
-					DataDir: t.TempDir(),
-				}
-			},
+			func() *config.Config { return cfg },
 			database.New,
 			database.NewWebhookDBManager,
 			healthcheck.New,

internal/handlers/logbound_test.go

@@ -339,11 +339,9 @@ const storedUserPassword = "correct-horse-battery-staple"
 // storedFillBytes is the raw length of the client-chosen value in
 // those accounts' usernames. It is well past the 512-byte field
 // budget, so the line is still truncated, but short enough that the
-// session cookie a successful login writes stays inside
-// securecookie's 4 KB limit: the cookie is written BEFORE the
-// "user logged in" line, so an 8 KB username answers 500 and never
-// reaches it.
-const storedFillBytes = 1024
+// whole username, markers and fill name included, stays within
+// database.MaxUsernameBytes.
+const storedFillBytes = 960
 
 // storedFill builds a username fill of storedFillBytes raw bytes out
 // of repetitions of ch, with both markers at its far end.

internal/handlers/settings.go

@@ -0,0 +1,130 @@
+package handlers
+
+import (
+	"net/http"
+	"net/netip"
+	"strconv"
+	"strings"
+
+	"sneak.berlin/go/webhooker/internal/config"
+)
+
+// notSet is what the Settings page shows for a value that is empty.
+const notSet = "not set"
+
+// settingRow is one line of the Settings page: an environment
+// variable, what it controls, and the value the server loaded for it.
+type settingRow struct {
+	Name        string
+	Description string
+	Value       string
+}
+
+// HandleSettings returns a handler for the read-only Settings page,
+// which lists the configuration the server started with.
+func (h *Handlers) HandleSettings() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		h.renderTemplate(w, r, "settings.html", map[string]any{
+			"Settings": settingRows(h.params.Config),
+		})
+	}
+}
+
+// settingRows lists every field of cfg under the environment variable
+// it is read from, in the order of the README's configuration table.
+// METRICS_PASSWORD and SENTRY_DSN are credentials, so their values
+// never reach the page: only whether they are set.
+func settingRows(cfg *config.Config) []settingRow {
+	metricsUsername := cfg.MetricsUsername
+	if metricsUsername == "" {
+		metricsUsername = notSet
+	}
+
+	return []settingRow{
+		{"WEBHOOKER_ENVIRONMENT", "dev or prod", cfg.Environment},
+		{"PORT", "HTTP listen port", strconv.Itoa(cfg.Port)},
+		{
+			"BIND_ADDRESS",
+			"IP address the HTTP listener binds",
+			cfg.BindAddress,
+		},
+		{
+			"DATA_DIR",
+			"Directory for all SQLite databases",
+			cfg.DataDir,
+		},
+		{
+			"DEBUG",
+			"Enable debug logging",
+			strconv.FormatBool(cfg.Debug),
+		},
+		{
+			"MAINTENANCE_MODE",
+			"Report maintenanceMode: true in the healthcheck JSON. " +
+				"It does not change how any request is served",
+			strconv.FormatBool(cfg.MaintenanceMode),
+		},
+		{
+			"METRICS_USERNAME",
+			"Basic auth username for /metrics",
+			metricsUsername,
+		},
+		{
+			"METRICS_PASSWORD",
+			"Basic auth password for /metrics",
+			setOrNotSet(cfg.MetricsPassword),
+		},
+		{
+			"SENTRY_DSN",
+			"Error reporting DSN. Unset leaves error reporting off",
+			setOrNotSet(cfg.SentryDSN),
+		},
+		{
+			"RETENTION_SWEEP_INTERVAL",
+			"How often the retention reaper and archive sweeper run",
+			cfg.RetentionSweepInterval.String(),
+		},
+		{
+			"SESSION_IDLE_TIMEOUT",
+			"Idle session timeout. Zero or negative disables idle " +
+				"expiry",
+			cfg.SessionIdleTimeout.String(),
+		},
+		{
+			"RECEIVER_RATE_LIMIT",
+			"Receiver requests per minute per IP per entrypoint " +
+				"(10x that per IP across the route)",
+			strconv.Itoa(cfg.ReceiverRateLimit),
+		},
+		{
+			"TRUSTED_PROXIES",
+			"CIDRs whose forwarded headers are trusted",
+			cidrList(cfg.TrustedProxies),
+		},
+		{
+			"ALLOWED_EGRESS_CIDRS",
+			"CIDRs that delivery targets may reach despite the " +
+				"SSRF blocklist",
+			cidrList(cfg.AllowedEgressCIDRs),
+		},
+	}
+}
+
+// setOrNotSet is how the Settings page shows a credential: whether it
+// has a value, never the value itself.
+func setOrNotSet(value string) string {
+	if value == "" {
+		return notSet
+	}
+
+	return "set"
+}
+
+// cidrList renders a CIDR list setting for the Settings page.
+func cidrList(prefixes []netip.Prefix) string {
+	if len(prefixes) == 0 {
+		return "none"
+	}
+
+	return strings.Join(config.PrefixStrings(prefixes), ", ")
+}

internal/handlers/settings_test.go

@@ -0,0 +1,130 @@
+package handlers_test
+
+import (
+	"context"
+	"html"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"regexp"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/config"
+	"sneak.berlin/go/webhooker/internal/handlers"
+	"sneak.berlin/go/webhooker/internal/session"
+)
+
+// settingsShown renders the Settings page over cfg as a logged-in user
+// and returns the value it shows for each variable name, plus the
+// whole page.
+func settingsShown(
+	t *testing.T, cfg *config.Config,
+) (map[string]string, string) {
+	t.Helper()
+
+	var h *handlers.Handlers
+
+	var sess *session.Session
+
+	app := newTestAppWithConfig(t, cfg, &h, &sess)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	req := httptest.NewRequestWithContext(
+		context.Background(), http.MethodGet, "/settings", nil,
+	)
+	for _, c := range authenticatedCookies(t, sess, "id", "admin") {
+		req.AddCookie(c)
+	}
+
+	w := httptest.NewRecorder()
+	h.HandleSettings().ServeHTTP(w, req)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	body := w.Body.String()
+
+	row := regexp.MustCompile(
+		`<code[^>]*>([A-Z_]+)</code>\s*<code[^>]*>([^<]*)</code>`,
+	)
+
+	shown := map[string]string{}
+	for _, match := range row.FindAllStringSubmatch(body, -1) {
+		shown[match[1]] = html.UnescapeString(match[2])
+	}
+
+	return shown, body
+}
+
+func TestSettingsPageShowsLoadedConfiguration(t *testing.T) {
+	t.Parallel()
+
+	const (
+		metricsPassword = "metrics-password-1f9a"
+		sentryKey       = "dsnkey7c2e"
+		sentryDSN       = "https://" + sentryKey + "@errors.example.com/42"
+	)
+
+	cfg := &config.Config{
+		DataDir:                t.TempDir(),
+		Debug:                  true,
+		MaintenanceMode:        true,
+		Environment:            config.EnvironmentDev,
+		MetricsUsername:        "scraper",
+		MetricsPassword:        metricsPassword,
+		Port:                   9123,
+		SentryDSN:              sentryDSN,
+		BindAddress:            "192.0.2.10",
+		RetentionSweepInterval: 17 * time.Minute,
+		SessionIdleTimeout:     3 * time.Hour,
+		ReceiverRateLimit:      77,
+		TrustedProxies: []netip.Prefix{
+			netip.MustParsePrefix("10.1.0.0/16"),
+		},
+		AllowedEgressCIDRs: []netip.Prefix{
+			netip.MustParsePrefix("192.168.5.0/24"),
+			netip.MustParsePrefix("fd00::/8"),
+		},
+	}
+
+	shown, body := settingsShown(t, cfg)
+
+	assert.Equal(t, map[string]string{
+		"WEBHOOKER_ENVIRONMENT":    "dev",
+		"PORT":                     "9123",
+		"BIND_ADDRESS":             "192.0.2.10",
+		"DATA_DIR":                 cfg.DataDir,
+		"DEBUG":                    "true",
+		"MAINTENANCE_MODE":         "true",
+		"METRICS_USERNAME":         "scraper",
+		"METRICS_PASSWORD":         "set",
+		"SENTRY_DSN":               "set",
+		"RETENTION_SWEEP_INTERVAL": "17m0s",
+		"SESSION_IDLE_TIMEOUT":     "3h0m0s",
+		"RECEIVER_RATE_LIMIT":      "77",
+		"TRUSTED_PROXIES":          "10.1.0.0/16",
+		"ALLOWED_EGRESS_CIDRS":     "192.168.5.0/24, fd00::/8",
+	}, shown)
+
+	assert.NotContains(t, body, metricsPassword)
+	assert.NotContains(t, body, sentryKey)
+	assert.Contains(
+		t, body, `href="/settings"`,
+		"the navigation bar links to the page",
+	)
+}
+
+func TestSettingsPageShowsUnsetValues(t *testing.T) {
+	t.Parallel()
+
+	shown, _ := settingsShown(t, &config.Config{DataDir: t.TempDir()})
+
+	assert.Equal(t, "not set", shown["METRICS_USERNAME"])
+	assert.Equal(t, "not set", shown["METRICS_PASSWORD"])
+	assert.Equal(t, "not set", shown["SENTRY_DSN"])
+	assert.Equal(t, "none", shown["TRUSTED_PROXIES"])
+	assert.Equal(t, "none", shown["ALLOWED_EGRESS_CIDRS"])
+}

internal/server/routes.go

@@ -141,6 +141,7 @@ func (s *Server) setupRoutes() {
 
 	s.setupPageRoutes()
 	s.setupUserRoutes()
+	s.setupSettingsRoutes()
 	s.setupSourceRoutes()
 	s.setupWebhookRoutes()
 }
@@ -181,6 +182,21 @@ func (s *Server) setupUserRoutes() {
 	})
 }
 
+// setupSettingsRoutes serves the Settings page. It is GET only:
+// configuration comes from the environment and nothing here changes
+// it.
+func (s *Server) setupSettingsRoutes() {
+	s.router.Route("/settings", func(r chi.Router) {
+		// MaxBodySize precedes CSRF and RequireAuth deliberately;
+		// see maxFormBodySize for why, and for what it costs.
+		r.Use(s.mw.MaxBodySize(maxFormBodySize))
+		r.Use(s.mw.CSRF())
+		r.Use(s.mw.NoCache())
+		r.Use(s.mw.RequireAuth())
+		r.Get("/", s.h.HandleSettings())
+	})
+}
+
 func (s *Server) setupSourceRoutes() {
 	s.router.Route("/sources", func(r chi.Router) {
 		// MaxBodySize precedes CSRF and RequireAuth deliberately;

internal/server/settings_test.go

@@ -0,0 +1,22 @@
+package server_test
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSettingsPageIsBehindLogin(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	w := env.get("/settings", nil)
+	assert.Equal(t, http.StatusSeeOther, w.Code)
+	assert.Equal(t, "/pages/login", w.Header().Get("Location"))
+
+	w = env.get("/settings", env.authCookies(t, "id", "admin"))
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "WEBHOOKER_ENVIRONMENT")
+}

internal/server/static_assets_test.go

@@ -13,9 +13,9 @@ import (
 
 // TestBaseTemplateScriptsAreServed walks every /s/ script the base
 // template loads on each page and fetches it through the real router.
-// Alpine.js is fetched at build time rather than committed, so nothing
-// in the repo guarantees it is present: this is the check that the page
-// still gets the JavaScript it asks for.
+// Alpine.js is extracted from its tarball in 3p/ at build time, so the
+// file is not in the tree: this is the check that the page still gets
+// the JavaScript it asks for.
 func TestBaseTemplateScriptsAreServed(t *testing.T) {
 	t.Parallel()
 

script/assets

@@ -0,0 +1,16 @@
+#!/bin/sh
+# script/assets: extract Alpine.js from its npm package tarball, committed
+# in 3p/, to static/js/alpine.min.js, where go:embed reads it. The
+# extracted file is not committed. script/test, make build and make dev run
+# this first.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    tar -xzOf 3p/alpinejs-3.14.9.tgz package/dist/cdn.min.js \
+        >static/js/alpine.min.js
+}
+
+main "$@"

script/bootstrap

@@ -4,9 +4,7 @@
 # installed tools are skipped. Base tooling comes from nix, apt, brew,
 # or apk (detected in that order); assumes NOTHING is present (not git,
 # make, or go). golangci-lint is deliberately not installed: linting runs
-# only in docker, via script/lint and Dockerfile.lint. Finishes by running
-# script/fetch-assets, which installs the hash-pinned third-party browser
-# assets the repo does not commit.
+# only in docker, via script/lint and Dockerfile.lint.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
@@ -69,11 +67,6 @@ main() {
 
     go mod download
 
-    # Third-party browser assets are not committed; fetch and verify them
-    # so a fresh clone can build and test.
-    if missing curl; then pkg_install curl curl curl curl; fi
-    "$ROOT/script/fetch-assets"
-
     echo "bootstrap complete"
 }
 

script/check

@@ -1,6 +1,7 @@
 #!/bin/sh
 # script/check: run all checks (test, lint, fmt-check). Our own
-# extension to scripts-to-rule-them-all. Must not modify any files.
+# extension to scripts-to-rule-them-all.
+# Writes only the ignored static/js/alpine.min.js, through script/test.
 # Generic: usually needs no adaptation.
 set -eu
 

script/fetch-assets

@@ -1,104 +0,0 @@
-#!/bin/sh
-# script/fetch-assets: download the third-party browser assets the web UI
-# ships and install them under static/. Minified bundles are not committed
-# (REPO_POLICIES.md: no build artifacts in version control), so the build
-# fetches them here. Every download is verified against a hardcoded sha256
-# before it is installed, and any mismatch aborts. Idempotent: an asset
-# already present with its pinned hash is left alone.
-set -eu
-
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-
-# The sha256 of each installed asset lives in static/vendor.sha256, in
-# sha256sum(1) format, with paths relative to static/. That file is the
-# single source of truth: this script verifies against it, and
-# static/vendor_test.go asserts the bytes embedded into the binary match
-# it, so the hash cannot rot into a value nothing checks.
-MANIFEST="static/vendor.sha256"
-
-# Alpine.js 3.14.9, 2026-08-17. Fetched from registry.npmjs.org, the
-# publisher of record; the jsDelivr and unpkg copies are mirrors of this
-# same tarball. dist/cdn.min.js is the browser build Alpine publishes for
-# a <script> tag.
-ALPINE_VERSION="3.14.9"
-ALPINE_URL="https://registry.npmjs.org/alpinejs/-/alpinejs-${ALPINE_VERSION}.tgz"
-# sha256 of alpinejs-3.14.9.tgz
-ALPINE_TARBALL_SHA256="97dad7c0c81e659cfc8e7700055da9770f8186187cb9a8a76efb57e00d5ce52a"
-ALPINE_MEMBER="package/dist/cdn.min.js"
-ALPINE_DEST="js/alpine.min.js"
-
-sha256_of() {
-    if command -v sha256sum >/dev/null 2>&1; then
-        sha256sum "$1" | cut -d' ' -f1
-    else
-        shasum -a 256 "$1" | cut -d' ' -f1
-    fi
-}
-
-# expected_sha256 <path-relative-to-static>
-expected_sha256() {
-    awk -v want="$1" '$2 == want { print $1; found = 1 }
-        END { if (!found) exit 1 }' "$ROOT/$MANIFEST"
-}
-
-# verify <file> <expected-sha256> <what>
-verify() {
-    actual="$(sha256_of "$1")"
-    if [ "$actual" != "$2" ]; then
-        echo "fetch-assets: sha256 mismatch for $3" >&2
-        echo "  expected: $2" >&2
-        echo "  actual:   $actual" >&2
-        exit 1
-    fi
-}
-
-# up_to_date <path-relative-to-static> <expected-sha256>
-up_to_date() {
-    [ -f "$ROOT/static/$1" ] || return 1
-    [ "$(sha256_of "$ROOT/static/$1")" = "$2" ]
-}
-
-fetch_alpine() {
-    want="$(expected_sha256 "$ALPINE_DEST")"
-
-    if up_to_date "$ALPINE_DEST" "$want"; then
-        echo "fetch-assets: static/$ALPINE_DEST already at $want"
-        return 0
-    fi
-
-    echo "fetch-assets: fetching Alpine.js $ALPINE_VERSION from $ALPINE_URL"
-    tmp="$(mktemp -d)"
-    trap 'rm -rf "$tmp"' EXIT INT TERM
-    curl -fsSL -o "$tmp/alpine.tgz" "$ALPINE_URL"
-    verify "$tmp/alpine.tgz" "$ALPINE_TARBALL_SHA256" "alpinejs-${ALPINE_VERSION}.tgz"
-    tar -xzOf "$tmp/alpine.tgz" "$ALPINE_MEMBER" >"$tmp/alpine.min.js"
-    verify "$tmp/alpine.min.js" "$want" "$ALPINE_MEMBER from alpinejs-${ALPINE_VERSION}.tgz"
-
-    mkdir -p "$(dirname "$ROOT/static/$ALPINE_DEST")"
-    cp "$tmp/alpine.min.js" "$ROOT/static/$ALPINE_DEST"
-    rm -rf "$tmp"
-    trap - EXIT INT TERM
-    echo "fetch-assets: installed static/$ALPINE_DEST ($want)"
-}
-
-# Re-check every manifest entry against what is now on disk, so an entry
-# no script installs fails loudly instead of passing silently.
-verify_manifest() {
-    while read -r want path; do
-        case "$want" in '' | '#'*) continue ;; esac
-        if [ ! -f "$ROOT/static/$path" ]; then
-            echo "fetch-assets: $MANIFEST lists static/$path, which is missing" >&2
-            exit 1
-        fi
-        verify "$ROOT/static/$path" "$want" "static/$path"
-    done <"$ROOT/$MANIFEST"
-}
-
-main() {
-    cd "$ROOT"
-    fetch_alpine
-    verify_manifest
-    echo "fetch-assets: all assets in $MANIFEST verified"
-}
-
-main "$@"

script/test

@@ -28,6 +28,7 @@ ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
+    "$ROOT/script/assets"
     go test -v -race -timeout 90s ./...
 }
 

static/vendor.sha256

@@ -1 +0,0 @@
-3ed1eed252488921df65e363d6715deb04d7f92aaedb9e52199fdf73cb1e0ad3  js/alpine.min.js

static/vendor_test.go

@@ -1,92 +0,0 @@
-package static_test
-
-import (
-	"bufio"
-	"crypto/sha256"
-	"encoding/hex"
-	"os"
-	"strings"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-
-	"sneak.berlin/go/webhooker/static"
-)
-
-const manifestPath = "vendor.sha256"
-
-// fetchHint is appended to every failure here: the assets the manifest
-// covers are fetched by the build, not committed, so a fresh clone that
-// has not run script/fetch-assets fails this test and should be told why.
-const fetchHint = "run `script/fetch-assets` (or `make assets`) to install " +
-	"the pinned third-party assets"
-
-// TestVendoredAssetsMatchManifest asserts that every asset listed in
-// static/vendor.sha256 is embedded in the binary with exactly the pinned
-// bytes. script/fetch-assets verifies the same hashes at download time;
-// this test verifies them again on what actually ships, so a build that
-// skipped, cached, or subverted the fetch cannot produce a binary serving
-// unpinned third-party JavaScript.
-func TestVendoredAssetsMatchManifest(t *testing.T) {
-	t.Parallel()
-
-	entries := readManifest(t)
-	require.NotEmpty(t, entries, "%s lists no assets", manifestPath)
-
-	for path, want := range entries {
-		t.Run(path, func(t *testing.T) {
-			t.Parallel()
-
-			data, err := static.Static.ReadFile(path)
-			require.NoErrorf(
-				t, err,
-				"%s is listed in %s but is not embedded; %s",
-				path, manifestPath, fetchHint,
-			)
-
-			sum := sha256.Sum256(data)
-			got := hex.EncodeToString(sum[:])
-			require.Equalf(
-				t, want, got,
-				"embedded %s does not match its pinned sha256 in %s; %s",
-				path, manifestPath, fetchHint,
-			)
-		})
-	}
-}
-
-// readManifest parses static/vendor.sha256, which is in sha256sum(1)
-// format with paths relative to static/.
-func readManifest(t *testing.T) map[string]string {
-	t.Helper()
-
-	f, err := os.Open(manifestPath)
-	require.NoError(t, err, "opening %s", manifestPath)
-
-	defer func() { require.NoError(t, f.Close()) }()
-
-	entries := make(map[string]string)
-	scanner := bufio.NewScanner(f)
-
-	for scanner.Scan() {
-		line := strings.TrimSpace(scanner.Text())
-		if line == "" || strings.HasPrefix(line, "#") {
-			continue
-		}
-
-		fields := strings.Fields(line)
-		require.Lenf(
-			t, fields, 2,
-			"%s: malformed entry %q, want \"<sha256>  <path>\"",
-			manifestPath, line,
-		)
-
-		sum, path := fields[0], fields[1]
-		require.Lenf(t, sum, 64, "%s: %q is not a sha256", manifestPath, sum)
-		entries[path] = sum
-	}
-
-	require.NoError(t, scanner.Err(), "reading %s", manifestPath)
-
-	return entries
-}

templates/navbar.html

@@ -17,6 +17,7 @@
         <div class="hidden md:flex items-center gap-4">
             {{if .User}}
             <a href="/sources" class="btn-text">Webhooks</a>
+            <a href="/settings" class="btn-text">Settings</a>
             <a href="/user/{{.User.Username}}" class="btn-text">
                 <svg class="w-5 h-5 mr-1" fill="currentColor" viewBox="0 0 16 16">
                     <path d="M11 6a3 3 0 1 1-6 0 3 3 0 0 1 6 0z"/>
@@ -39,6 +40,7 @@
         <div class="flex flex-col gap-2">
             {{if .User}}
             <a href="/sources" class="btn-text w-full text-left">Webhooks</a>
+            <a href="/settings" class="btn-text w-full text-left">Settings</a>
             <a href="/user/{{.User.Username}}" class="btn-text w-full text-left">Profile</a>
             <form method="POST" action="/pages/logout">
                 <input type="hidden" name="csrf_token" value="{{.CSRFToken}}">

templates/settings.html

@@ -0,0 +1,24 @@
+{{template "base" .}}
+
+{{define "title"}}Settings - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-6xl mx-auto px-6 py-8">
+    <h1 class="text-2xl font-medium text-gray-900">Settings</h1>
+    <p class="text-sm text-gray-500 mt-1 mb-6">The configuration this server started with. It is set in the server's environment and cannot be changed here.</p>
+
+    <div class="card">
+        <div class="divide-y divide-gray-100">
+            {{range .Settings}}
+            <div class="p-4">
+                <div class="flex justify-between items-start gap-4">
+                    <code class="text-sm font-medium text-gray-900">{{.Name}}</code>
+                    <code class="text-sm text-gray-900 break-all">{{.Value}}</code>
+                </div>
+                <p class="text-sm text-gray-500 mt-1">{{.Description}}</p>
+            </div>
+            {{end}}
+        </div>
+    </div>
+</div>
+{{end}}