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.
77 lines
1.6 KiB
Go
77 lines
1.6 KiB
Go
//go:build (!amd64 && !arm64) || appengine || !gc || purego
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// +build !amd64,!arm64 appengine !gc purego
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package xxhash
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// Sum64 computes the 64-bit xxHash digest of b with a zero seed.
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func Sum64(b []byte) uint64 {
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// A simpler version would be
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// d := New()
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// d.Write(b)
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// return d.Sum64()
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// but this is faster, particularly for small inputs.
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n := len(b)
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var h uint64
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if n >= 32 {
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v1 := primes[0] + prime2
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v2 := prime2
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v3 := uint64(0)
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v4 := -primes[0]
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for len(b) >= 32 {
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v1 = round(v1, u64(b[0:8:len(b)]))
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v2 = round(v2, u64(b[8:16:len(b)]))
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v3 = round(v3, u64(b[16:24:len(b)]))
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v4 = round(v4, u64(b[24:32:len(b)]))
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b = b[32:len(b):len(b)]
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}
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h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
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h = mergeRound(h, v1)
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h = mergeRound(h, v2)
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h = mergeRound(h, v3)
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h = mergeRound(h, v4)
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} else {
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h = prime5
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}
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h += uint64(n)
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for ; len(b) >= 8; b = b[8:] {
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k1 := round(0, u64(b[:8]))
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h ^= k1
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h = rol27(h)*prime1 + prime4
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}
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if len(b) >= 4 {
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h ^= uint64(u32(b[:4])) * prime1
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h = rol23(h)*prime2 + prime3
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b = b[4:]
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}
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for ; len(b) > 0; b = b[1:] {
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h ^= uint64(b[0]) * prime5
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h = rol11(h) * prime1
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}
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h ^= h >> 33
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h *= prime2
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h ^= h >> 29
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h *= prime3
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h ^= h >> 32
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return h
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}
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func writeBlocks(d *Digest, b []byte) int {
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v1, v2, v3, v4 := d.v1, d.v2, d.v3, d.v4
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n := len(b)
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for len(b) >= 32 {
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v1 = round(v1, u64(b[0:8:len(b)]))
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v2 = round(v2, u64(b[8:16:len(b)]))
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v3 = round(v3, u64(b[16:24:len(b)]))
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v4 = round(v4, u64(b[24:32:len(b)]))
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b = b[32:len(b):len(b)]
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}
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d.v1, d.v2, d.v3, d.v4 = v1, v2, v3, v4
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return n - len(b)
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}
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