jx12n 4d9a26498e hush: one-time secret links the server cannot read

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.

2026-09-03 00:08:38 -06:00

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atomic

Simple wrappers for primitive types to enforce atomic access.

Installation

$ go get -u go.uber.org/atomic@v1

Legacy Import Path

As of v1.5.0, the import path go.uber.org/atomic is the only supported way of using this package. If you are using Go modules, this package will fail to compile with the legacy import path path github.com/uber-go/atomic.

We recommend migrating your code to the new import path but if you're unable to do so, or if your dependencies are still using the old import path, you will have to add a replace directive to your go.mod file downgrading the legacy import path to an older version.

replace github.com/uber-go/atomic => github.com/uber-go/atomic v1.4.0

You can do so automatically by running the following command.

$ go mod edit -replace github.com/uber-go/atomic=github.com/uber-go/atomic@v1.4.0

Usage

The standard library's sync/atomic is powerful, but it's easy to forget which variables must be accessed atomically. go.uber.org/atomic preserves all the functionality of the standard library, but wraps the primitive types to provide a safer, more convenient API.

var atom atomic.Uint32
atom.Store(42)
atom.Sub(2)
atom.CAS(40, 11)

See the documentation for a complete API specification.

Development Status

Stable.

Released under the MIT License.

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