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.
118 lines
2.9 KiB
Go
118 lines
2.9 KiB
Go
// Copyright The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package procfs
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import (
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"fmt"
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"net"
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"os"
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"strconv"
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"strings"
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)
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// Learned from include/uapi/linux/if_arp.h.
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const (
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// Completed entry (ha valid).
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ATFComplete = 0x02
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// Permanent entry.
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ATFPermanent = 0x04
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// Publish entry.
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ATFPublish = 0x08
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// Has requested trailers.
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ATFUseTrailers = 0x10
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// Obsoleted: Want to use a netmask (only for proxy entries).
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ATFNetmask = 0x20
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// Don't answer this addresses.
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ATFDontPublish = 0x40
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)
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// ARPEntry contains a single row of the columnar data represented in
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// /proc/net/arp.
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type ARPEntry struct {
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// IP address
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IPAddr net.IP
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// MAC address
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HWAddr net.HardwareAddr
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// Name of the device
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Device string
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// Flags
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Flags byte
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}
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// GatherARPEntries retrieves all the ARP entries, parse the relevant columns,
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// and then return a slice of ARPEntry's.
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func (fs FS) GatherARPEntries() ([]ARPEntry, error) {
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data, err := os.ReadFile(fs.proc.Path("net/arp"))
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if err != nil {
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return nil, fmt.Errorf("%w: error reading arp %s: %w", ErrFileRead, fs.proc.Path("net/arp"), err)
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}
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return parseARPEntries(data)
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}
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func parseARPEntries(data []byte) ([]ARPEntry, error) {
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lines := strings.Split(string(data), "\n")
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entries := make([]ARPEntry, 0)
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var err error
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const (
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expectedDataWidth = 6
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expectedHeaderWidth = 9
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)
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for _, line := range lines {
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columns := strings.Fields(line)
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width := len(columns)
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switch width {
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case expectedHeaderWidth, 0:
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continue
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case expectedDataWidth:
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entry, err := parseARPEntry(columns)
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if err != nil {
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return []ARPEntry{}, fmt.Errorf("%w: Failed to parse ARP entry: %v: %w", ErrFileParse, entry, err)
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}
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entries = append(entries, entry)
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default:
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return []ARPEntry{}, fmt.Errorf("%w: %d columns found, but expected %d: %w", ErrFileParse, width, expectedDataWidth, err)
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}
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}
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return entries, err
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}
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func parseARPEntry(columns []string) (ARPEntry, error) {
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entry := ARPEntry{Device: columns[5]}
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ip := net.ParseIP(columns[0])
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entry.IPAddr = ip
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if mac, err := net.ParseMAC(columns[3]); err == nil {
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entry.HWAddr = mac
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} else {
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return ARPEntry{}, err
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}
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if flags, err := strconv.ParseUint(columns[2], 0, 8); err == nil {
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entry.Flags = byte(flags)
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} else {
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return ARPEntry{}, err
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}
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return entry, nil
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}
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// IsComplete returns true if ARP entry is marked with complete flag.
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func (entry *ARPEntry) IsComplete() bool {
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return entry.Flags&ATFComplete != 0
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}
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