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.
68 lines
2.5 KiB
Go
68 lines
2.5 KiB
Go
package chassis
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import (
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"net/http"
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"strconv"
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"time"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/collectors"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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)
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// metrics holds the RED HTTP collectors on a private registry (no global state,
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// so tests and multiple apps never collide). The route label is the matched
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// ServeMux pattern — bounded cardinality, never the raw path.
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type metrics struct {
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reg *prometheus.Registry
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reqs *prometheus.CounterVec
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dur *prometheus.HistogramVec
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inflight prometheus.Gauge
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}
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// newMetrics builds the RED collectors and registers them alongside any
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// service-owned collectors (Config.Collectors) on the same private registry —
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// so /metrics is one scrape and a domain gauge cannot be lost to a second
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// endpoint nobody remembers to scrape.
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func newMetrics(service string, extra ...prometheus.Collector) *metrics {
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reg := prometheus.NewRegistry()
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labels := prometheus.Labels{"service": service}
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m := &metrics{
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reg: reg,
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reqs: prometheus.NewCounterVec(prometheus.CounterOpts{
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Name: "http_requests_total", Help: "Total HTTP requests.", ConstLabels: labels,
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}, []string{"method", "route", "status"}),
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dur: prometheus.NewHistogramVec(prometheus.HistogramOpts{
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Name: "http_request_duration_seconds", Help: "HTTP request latency.",
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Buckets: prometheus.DefBuckets, ConstLabels: labels,
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}, []string{"method", "route"}),
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inflight: prometheus.NewGauge(prometheus.GaugeOpts{
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Name: "http_requests_in_flight", Help: "In-flight HTTP requests.", ConstLabels: labels,
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}),
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}
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reg.MustRegister(m.reqs, m.dur, m.inflight,
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collectors.NewGoCollector(),
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collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}))
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for _, c := range extra {
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reg.MustRegister(c)
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}
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return m
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}
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func (m *metrics) observe(method, route string, status int, d time.Duration) {
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m.countOnly(method, route, status)
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m.dur.WithLabelValues(method, route).Observe(d.Seconds())
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}
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// countOnly records a request without timing it. For responses whose elapsed
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// time is not a latency — an event stream ends when the operator closes the
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// tab, and putting that in the histogram makes every latency alert lie.
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func (m *metrics) countOnly(method, route string, status int) {
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m.reqs.WithLabelValues(method, route, strconv.Itoa(status)).Inc()
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}
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// handler serves the Prometheus exposition for the metrics agent to scrape.
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func (m *metrics) handler() http.Handler {
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return promhttp.HandlerFor(m.reg, promhttp.HandlerOpts{Registry: m.reg})
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}
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