hush/vendor/github.com/prometheus/procfs/net_xfrm.go
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

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// Copyright The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package procfs
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
// XfrmStat models the contents of /proc/net/xfrm_stat.
type XfrmStat struct {
// All errors which are not matched by other
XfrmInError int
// No buffer is left
XfrmInBufferError int
// Header Error
XfrmInHdrError int
// No state found
// i.e. either inbound SPI, address, or IPSEC protocol at SA is wrong
XfrmInNoStates int
// Transformation protocol specific error
// e.g. SA Key is wrong
XfrmInStateProtoError int
// Transformation mode specific error
XfrmInStateModeError int
// Sequence error
// e.g. sequence number is out of window
XfrmInStateSeqError int
// State is expired
XfrmInStateExpired int
// State has mismatch option
// e.g. UDP encapsulation type is mismatched
XfrmInStateMismatch int
// State is invalid
XfrmInStateInvalid int
// No matching template for states
// e.g. Inbound SAs are correct but SP rule is wrong
XfrmInTmplMismatch int
// No policy is found for states
// e.g. Inbound SAs are correct but no SP is found
XfrmInNoPols int
// Policy discards
XfrmInPolBlock int
// Policy error
XfrmInPolError int
// All errors which are not matched by others
XfrmOutError int
// Bundle generation error
XfrmOutBundleGenError int
// Bundle check error
XfrmOutBundleCheckError int
// No state was found
XfrmOutNoStates int
// Transformation protocol specific error
XfrmOutStateProtoError int
// Transportation mode specific error
XfrmOutStateModeError int
// Sequence error
// i.e sequence number overflow
XfrmOutStateSeqError int
// State is expired
XfrmOutStateExpired int
// Policy discads
XfrmOutPolBlock int
// Policy is dead
XfrmOutPolDead int
// Policy Error
XfrmOutPolError int
// Forward routing of a packet is not allowed
XfrmFwdHdrError int
// State is invalid, perhaps expired
XfrmOutStateInvalid int
// State hasnt been fully acquired before use
XfrmAcquireError int
}
// NewXfrmStat reads the xfrm_stat statistics.
func NewXfrmStat() (XfrmStat, error) {
fs, err := NewFS(DefaultMountPoint)
if err != nil {
return XfrmStat{}, err
}
return fs.NewXfrmStat()
}
// NewXfrmStat reads the xfrm_stat statistics from the 'proc' filesystem.
func (fs FS) NewXfrmStat() (XfrmStat, error) {
file, err := os.Open(fs.proc.Path("net/xfrm_stat"))
if err != nil {
return XfrmStat{}, err
}
defer file.Close()
var (
x = XfrmStat{}
s = bufio.NewScanner(file)
)
for s.Scan() {
fields := strings.Fields(s.Text())
if len(fields) != 2 {
return XfrmStat{}, fmt.Errorf("%w: %q line %q", ErrFileParse, file.Name(), s.Text())
}
name := fields[0]
value, err := strconv.Atoi(fields[1])
if err != nil {
return XfrmStat{}, err
}
switch name {
case "XfrmInError":
x.XfrmInError = value
case "XfrmInBufferError":
x.XfrmInBufferError = value
case "XfrmInHdrError":
x.XfrmInHdrError = value
case "XfrmInNoStates":
x.XfrmInNoStates = value
case "XfrmInStateProtoError":
x.XfrmInStateProtoError = value
case "XfrmInStateModeError":
x.XfrmInStateModeError = value
case "XfrmInStateSeqError":
x.XfrmInStateSeqError = value
case "XfrmInStateExpired":
x.XfrmInStateExpired = value
case "XfrmInStateInvalid":
x.XfrmInStateInvalid = value
case "XfrmInTmplMismatch":
x.XfrmInTmplMismatch = value
case "XfrmInNoPols":
x.XfrmInNoPols = value
case "XfrmInPolBlock":
x.XfrmInPolBlock = value
case "XfrmInPolError":
x.XfrmInPolError = value
case "XfrmOutError":
x.XfrmOutError = value
case "XfrmInStateMismatch":
x.XfrmInStateMismatch = value
case "XfrmOutBundleGenError":
x.XfrmOutBundleGenError = value
case "XfrmOutBundleCheckError":
x.XfrmOutBundleCheckError = value
case "XfrmOutNoStates":
x.XfrmOutNoStates = value
case "XfrmOutStateProtoError":
x.XfrmOutStateProtoError = value
case "XfrmOutStateModeError":
x.XfrmOutStateModeError = value
case "XfrmOutStateSeqError":
x.XfrmOutStateSeqError = value
case "XfrmOutStateExpired":
x.XfrmOutStateExpired = value
case "XfrmOutPolBlock":
x.XfrmOutPolBlock = value
case "XfrmOutPolDead":
x.XfrmOutPolDead = value
case "XfrmOutPolError":
x.XfrmOutPolError = value
case "XfrmFwdHdrError":
x.XfrmFwdHdrError = value
case "XfrmOutStateInvalid":
x.XfrmOutStateInvalid = value
case "XfrmAcquireError":
x.XfrmAcquireError = value
}
}
return x, s.Err()
}