4d9a26498e
Paste a secret, get a link, send it. The first person to open it and press
Reveal sees the secret; the link dies at that moment. The recipient needs a
browser and nothing else — no account, no client, no installed tooling.
The server cannot read what it stores. AES-256-GCM happens in the browser and
the key lives in the URL fragment, which browsers never transmit, so hushd
holds ciphertext and no key material. That is a property of where the key sits
rather than a promise about our conduct, which is why there is deliberately no
endpoint accepting a plaintext secret and no server-side-encryption fallback:
two guarantees behind one URL would be worse than one honest guarantee.
Three decisions carry the design:
* GET /s/{id} touches NO storage, not even to check existence. Slack, Teams,
WhatsApp, iMessage and Outlook Safe Links all fetch a URL before a human
sees it, so destroying on GET would destroy most secrets in transit and the
recipient's "already used" would be indistinguishable from interception.
Only POST /reveal consumes. Bot user-agent detection is an arms race;
removing the side effect from GET is not. Pinned by
TestGettingTheRevealPageNeverConsumesTheSecret.
* Destruction is one Redis GETDEL, which is atomic. GET-then-DEL has a window
where two simultaneous readers both win, and for a one-time secret that
window is the product. The store contract demands atomicity and the same
concurrency test runs against both implementations.
* Missing, already-revealed, expired and evicted are ONE indistinguishable
410. Separating them would confirm to a prober that a given link was real.
The secret id IS the capability, so secret.ID is a struct whose every
accidental path — %v, %s, String(), slog, json.Marshal — emits a redacted
handle or refuses, and the raw value needs an explicit Value(). The first
version tried to prevent leaks by implementing no String() at all; its own test
caught that Go's fmt prints unexported fields anyway, so forbidding the method
had removed the control rather than the leak.
Operationally: structured JSON on stdout in the fleet's wire format, which
Vector already collects with no annotation; six hush_* metrics on the chassis
registry with no id, IP or path in any label; five alert rules wired into
vmalert. The public Ingress enumerates /, /s/ and /api/ so /metrics, /healthz
and /readyz share the port but are unreachable from the internet — no
basic-auth middleware to maintain and get wrong.
Dependencies are vendored because go-chassis is private: the Woodpecker test
step and the in-cluster Kaniko build both run -mod=vendor with GOPROXY=off and
hold no git credential.
cmd/hush-mcp is a stdio MCP server doing the same client-side crypto locally,
so using hush from an agent preserves the same guarantee as using it from a
browser.
51 lines
1.5 KiB
Go
51 lines
1.5 KiB
Go
package chassis
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import (
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"context"
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"net/http"
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)
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// CheckFunc reports whether a dependency is usable right now. It MUST honor the
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// passed ctx deadline and return a non-nil error (with no secrets) when unhealthy.
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type CheckFunc func(ctx context.Context) error
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type namedCheck struct {
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name string
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fn CheckFunc
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}
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// handleLive is the k8s liveness probe: 200 while the process runs. It does NOT
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// check dependencies and stays 200 during drain — a flapping dep or an
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// in-progress shutdown must never trigger a restart, only LB removal.
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func (a *App) handleLive(c *Context) error {
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return c.OK(map[string]any{"status": "ok"})
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}
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// handleReady is the k8s readiness probe. It returns 503 the moment shutdown
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// begins (two-phase drain: the LB pulls the pod before connections close), and
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// otherwise 200 only when every registered dependency check passes.
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func (a *App) handleReady(c *Context) error {
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if a.draining.Load() {
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return c.JSON(http.StatusServiceUnavailable, map[string]any{"status": "draining"})
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}
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ctx, cancel := context.WithTimeout(c.Context(), a.cfg.ReadyTimeout)
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defer cancel()
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checks := make(map[string]string, len(a.checks))
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ok := true
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for _, ch := range a.checks {
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if err := ch.fn(ctx); err != nil {
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checks[ch.name] = "error: " + err.Error()
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ok = false
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continue
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}
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checks[ch.name] = "ok"
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}
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status, code := "ok", http.StatusOK
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if !ok {
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status, code = "unready", http.StatusServiceUnavailable
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}
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return c.JSON(code, map[string]any{"status": status, "checks": checks})
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}
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