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.
75 lines
1.6 KiB
Go
75 lines
1.6 KiB
Go
package redis
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import (
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"context"
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)
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// ScanIterator is used to incrementally iterate over a collection of elements.
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type ScanIterator struct {
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cmd *ScanCmd
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pos int
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}
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// Err returns the last iterator error, if any.
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func (it *ScanIterator) Err() error {
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return it.cmd.Err()
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}
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// Next advances the cursor and returns true if more values can be read.
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func (it *ScanIterator) Next(ctx context.Context) bool {
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// Instantly return on errors.
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if it.cmd.Err() != nil {
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return false
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}
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// Advance cursor, check if we are still within range.
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if it.pos < len(it.cmd.page) {
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it.pos++
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return true
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}
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for {
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// Return if there is no more data to fetch.
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if it.cmd.cursor == 0 {
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return false
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}
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// Fetch next page.
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switch it.cmd.args[0] {
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case "scan", "qscan":
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it.cmd.args[1] = it.cmd.cursor
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default:
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it.cmd.args[2] = it.cmd.cursor
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}
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err := it.cmd.process(ctx, it.cmd)
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if err != nil {
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return false
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}
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// Await the fetch before reading page/cursor: on the deferred
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// autopipeline face process() only enqueues, and reading the raw
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// fields of a not-yet-executed command would spin re-issuing SCANs
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// with a stale cursor forever. Err() blocks until executed there and
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// is a no-op read everywhere else.
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if err := it.cmd.Err(); err != nil {
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return false
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}
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it.pos = 1
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// Redis can occasionally return empty page.
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if len(it.cmd.page) > 0 {
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return true
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}
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}
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}
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// Val returns the key/field at the current cursor position.
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func (it *ScanIterator) Val() string {
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var v string
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if it.cmd.Err() == nil && it.pos > 0 && it.pos <= len(it.cmd.page) {
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v = it.cmd.page[it.pos-1]
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}
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return v
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}
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