hush/internal/web/templates/create.html
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

119 lines
3.6 KiB
HTML

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