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.
119 lines
3.6 KiB
HTML
119 lines
3.6 KiB
HTML
{{define "content"}}
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<h1>hush<span>.</span></h1>
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<p class="lede">Paste a secret. Get a link that works once.</p>
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<div id="form">
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<label for="secret">Secret</label>
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<textarea id="secret" autofocus autocomplete="off" spellcheck="false"
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placeholder="API key, password, connection string…"></textarea>
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<div class="row">
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<div>
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<label for="ttl">Expires after</label>
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<select id="ttl">
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<option value="900">15 minutes</option>
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<option value="3600">1 hour</option>
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<option value="86400" selected>24 hours</option>
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<option value="259200">3 days</option>
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<option value="604800">7 days</option>
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</select>
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</div>
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</div>
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<button id="go">Create link</button>
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<p class="note" id="msg"></p>
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</div>
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<div id="result" class="hide">
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<label>Your one-time link</label>
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<div class="out" id="link"></div>
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<div class="row">
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<button id="copy">Copy link</button>
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<button id="again" class="secondary">Create another</button>
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</div>
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<p class="note warn">
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This is shown once and is not recoverable — hush cannot rebuild it, because
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the key it contains was never sent to the server. Copy it now.
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</p>
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</div>
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{{end}}
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{{define "script"}}
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<script>
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const $ = (id) => document.getElementById(id);
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const MAX = {{.MaxCiphertextBytes}};
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async function create() {
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const text = $("secret").value;
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if (!text) { return fail("Nothing to send."); }
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$("go").disabled = true;
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$("msg").className = "note";
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$("msg").textContent = "Encrypting…";
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let sealed;
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try {
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sealed = await seal(text);
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} catch (e) {
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return fail("Encryption failed in this browser: " + e.message);
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}
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// Check the size of the CIPHERTEXT, which is what the server caps, so the
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// message names the same number the server would reject on.
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if (sealed.ciphertext.length > MAX) {
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return fail("Too large: " + sealed.ciphertext.length + " > " + MAX + " bytes encrypted.");
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}
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let res, body;
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try {
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res = await fetch("/api/secrets", {
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method: "POST",
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headers: { "Content-Type": "application/json" },
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body: JSON.stringify({ ciphertext: sealed.ciphertext, ttl_seconds: Number($("ttl").value) }),
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});
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body = await res.json();
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} catch (e) {
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return fail("Could not reach hush: " + e.message);
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}
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if (!res.ok) {
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return fail(body && body.error ? body.error.message : "Server refused the secret (" + res.status + ").");
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}
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// The key goes in the fragment and ONLY in the fragment. Assembling the URL
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// here — not on the server — is what keeps the key client-side.
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const url = location.origin + "/s/" + body.id + "#" + sealed.key;
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$("link").textContent = url;
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$("form").classList.add("hide");
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$("result").classList.remove("hide");
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$("copy").focus();
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}
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function fail(m) {
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$("go").disabled = false;
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$("msg").className = "note err";
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$("msg").textContent = m;
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}
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$("go").addEventListener("click", create);
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$("secret").addEventListener("keydown", (e) => {
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if ((e.metaKey || e.ctrlKey) && e.key === "Enter") create();
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});
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$("copy").addEventListener("click", async () => {
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try {
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await navigator.clipboard.writeText($("link").textContent);
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$("copy").textContent = "Copied";
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setTimeout(() => ($("copy").textContent = "Copy link"), 1500);
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} catch {
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// Clipboard needs a permission this browser withheld; selecting the text
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// is a working fallback rather than a dead button.
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const r = document.createRange();
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r.selectNodeContents($("link"));
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getSelection().removeAllRanges();
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getSelection().addRange(r);
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$("copy").textContent = "Selected — press copy";
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}
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});
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$("again").addEventListener("click", () => location.assign("/"));
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</script>
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{{end}}
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