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kaetzchen.go
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kaetzchen.go
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// kaetzchen.go - Katzenpost provider auto-responder agents.
// Copyright (C) 2018 Yawning Angel and David Stainton
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// Package kaetzchen implements support for provider side auto-responder
// agents.
package kaetzchen
import (
"errors"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/hashcloak/Meson/server/config"
"github.com/hashcloak/Meson/server/internal/constants"
"github.com/hashcloak/Meson/server/internal/glue"
"github.com/hashcloak/Meson/server/internal/packet"
"github.com/katzenpost/core/monotime"
sConstants "github.com/katzenpost/core/sphinx/constants"
"github.com/katzenpost/core/worker"
"github.com/prometheus/client_golang/prometheus"
"golang.org/x/text/secure/precis"
"gopkg.in/eapache/channels.v1"
"gopkg.in/op/go-logging.v1"
)
// ParameterEndpoint is the mandatory Parameter key indicationg the
// Kaetzchen's endpoint.
const ParameterEndpoint = "endpoint"
// ErrNoResponse is the error returned from OnMessage() when there is no
// response to be sent (rather than an empty response).
var ErrNoResponse = errors.New("kaetzchen: message has no response")
// Parameters is the map describing each Kaetzchen's parameters to
// be published in the Provider's descriptor.
type Parameters map[string]interface{}
// Kaetzchen is the interface implemented by each auto-responder agent.
type Kaetzchen interface {
// Capability returns the agent's functionality for publication in
// the Provider's descriptor.
Capability() string
// Parameters returns the agent's paramenters for publication in
// the Provider's descriptor.
Parameters() Parameters
// OnRequest is the method that is called when the Provider receives
// a request designed for a particular agent. The caller will handle
// extracting the payload component of the message.
//
// Implementations MUST:
//
// * Be thread (go routine) safe.
//
// * Return ErrNoResponse if there is no response to be sent. A nil
// byte slice and nil error will result in a response with a 0 byte
// payload being sent.
//
// * NOT assume payload will be valid past the call to OnMessage.
// Any contents that need to be preserved, MUST be copied out,
// except if it is only used as a part of the response body.
OnRequest(id uint64, payload []byte, hasSURB bool) ([]byte, error)
// Halt cleans up the agent prior to de-registration and teardown.
Halt()
}
// BuiltInCtorFn is the constructor type for a built-in Kaetzchen.
type BuiltInCtorFn func(*config.Kaetzchen, glue.Glue) (Kaetzchen, error)
// BuiltInCtors are the constructors for all built-in Kaetzchen.
var BuiltInCtors = map[string]BuiltInCtorFn{
LoopCapability: NewLoop,
keyserverCapability: NewKeyserver,
}
type KaetzchenWorker struct {
sync.Mutex
worker.Worker
glue glue.Glue
log *logging.Logger
ch *channels.InfiniteChannel
kaetzchen map[[sConstants.RecipientIDLength]byte]Kaetzchen
dropCounter uint64
}
var (
packetsDropped = prometheus.NewCounter(
prometheus.CounterOpts{
Namespace: constants.Namespace,
Name: "dropped_packets_total",
Subsystem: constants.KaetzchenSubsystem,
Help: "Number of dropped packets",
},
)
kaetzchenRequests = prometheus.NewCounter(
prometheus.CounterOpts{
Namespace: constants.Namespace,
Name: "requests_total",
Subsystem: constants.KaetzchenSubsystem,
Help: "Number of Kaetzchen requests",
},
)
kaetzchenRequestsDuration = prometheus.NewSummary(
prometheus.SummaryOpts{
Namespace: constants.Namespace,
Name: "requests_duration_seconds",
Subsystem: constants.KaetzchenSubsystem,
Help: "Duration of a kaetzchen request in seconds",
},
)
kaetzchenRequestsDropped = prometheus.NewCounter(
prometheus.CounterOpts{
Namespace: constants.Namespace,
Name: "dropped_requests_total",
Subsystem: constants.KaetzchenSubsystem,
Help: "Number of total dropped kaetzchen requests",
},
)
kaetzchenRequestsFailed = prometheus.NewCounter(
prometheus.CounterOpts{
Namespace: constants.Namespace,
Name: "failed_requests_total",
Subsystem: constants.KaetzchenSubsystem,
Help: "Number of total failed kaetzchen requests",
},
)
kaetzchenRequestsTimer *prometheus.Timer
)
func init() {
prometheus.MustRegister(packetsDropped)
prometheus.MustRegister(kaetzchenRequests)
prometheus.MustRegister(kaetzchenRequestsDropped)
prometheus.MustRegister(kaetzchenRequestsFailed)
prometheus.MustRegister(kaetzchenRequestsDuration)
}
func (k *KaetzchenWorker) IsKaetzchen(recipient [sConstants.RecipientIDLength]byte) bool {
_, ok := k.kaetzchen[recipient]
return ok
}
func (k *KaetzchenWorker) registerKaetzchen(service Kaetzchen) error {
capa := service.Capability()
params := service.Parameters()
if params == nil {
return fmt.Errorf("provider: Kaetzchen: '%v' provided no parameters", capa)
}
// Sanitize the endpoint.
var ep string
if v, ok := params[ParameterEndpoint]; !ok {
return fmt.Errorf("provider: Kaetzchen: '%v' provided no endpoint", capa)
} else if ep, ok = v.(string); !ok {
return fmt.Errorf("provider: Kaetzchen: '%v' invalid endpoint type: %T", capa, v)
} else if epNorm, err := precis.UsernameCaseMapped.String(ep); err != nil {
return fmt.Errorf("provider: Kaetzchen: '%v' invalid endpoint: %v", capa, err)
} else if epNorm != ep {
return fmt.Errorf("provider: Kaetzchen: '%v' invalid endpoint, not normalized", capa)
}
rawEp := []byte(ep)
if len(rawEp) == 0 || len(rawEp) > sConstants.RecipientIDLength {
return fmt.Errorf("provider: Kaetzchen: '%v' invalid endpoint, length out of bounds", capa)
}
// Register it in the map by endpoint.
var epKey [sConstants.RecipientIDLength]byte
copy(epKey[:], rawEp)
if _, ok := k.kaetzchen[epKey]; ok {
return fmt.Errorf("provider: Kaetzchen: '%v' endpoint '%v' already registered", capa, ep)
}
k.kaetzchen[epKey] = service
k.log.Noticef("Registered Kaetzchen: '%v' -> '%v'.", ep, capa)
return nil
}
func (k *KaetzchenWorker) OnKaetzchen(pkt *packet.Packet) {
k.ch.In() <- pkt
}
func (k *KaetzchenWorker) getDropCounter() uint64 {
return atomic.LoadUint64(&k.dropCounter)
}
func (k *KaetzchenWorker) incrementDropCounter() uint64 {
return atomic.AddUint64(&k.dropCounter, uint64(1))
}
func (k *KaetzchenWorker) worker() {
// Kaetzchen delay is our max dwell time.
maxDwell := time.Duration(k.glue.Config().Debug.KaetzchenDelay) * time.Millisecond
defer k.log.Debugf("Halting Kaetzchen internal worker.")
ch := k.ch.Out()
for {
var pkt *packet.Packet
select {
case <-k.HaltCh():
k.log.Debugf("Terminating gracefully.")
return
case e := <-ch:
pkt = e.(*packet.Packet)
if dwellTime := monotime.Now() - pkt.DispatchAt; dwellTime > maxDwell {
count := k.incrementDropCounter()
k.log.Debugf("Dropping packet: %v (Spend %v in queue), total drops %d", pkt.ID, dwellTime, count)
packetsDropped.Inc()
pkt.Dispose()
continue
}
}
k.processKaetzchen(pkt)
}
}
func (k *KaetzchenWorker) processKaetzchen(pkt *packet.Packet) {
k.Lock()
kaetzchenRequestsTimer = prometheus.NewTimer(kaetzchenRequestsDuration)
k.Unlock()
defer pkt.Dispose()
ct, surb, err := packet.ParseForwardPacket(pkt)
if err != nil {
k.log.Debugf("Dropping Kaetzchen request: %v (%v)", pkt.ID, err)
k.incrementDropCounter()
kaetzchenRequestsDropped.Add(float64(k.getDropCounter()))
return
}
var resp []byte
dst, ok := k.kaetzchen[pkt.Recipient.ID]
if ok {
resp, err = dst.OnRequest(pkt.ID, ct, surb != nil)
}
switch {
case err == nil:
case err == ErrNoResponse:
k.log.Debugf("Processed Kaetzchen request: %v (No response)", pkt.ID)
kaetzchenRequests.Inc()
return
default:
k.log.Debugf("Failed to handle Kaetzchen request: %v (%v)", pkt.ID, err)
kaetzchenRequestsFailed.Inc()
return
}
// Iff there is a SURB, generate a SURB-Reply and schedule.
if surb != nil {
// Prepend the response header.
resp = append([]byte{0x01, 0x00}, resp...)
respPkt, err := packet.NewPacketFromSURB(pkt, surb, resp)
if err != nil {
k.log.Debugf("Failed to generate SURB-Reply: %v (%v)", pkt.ID, err)
return
}
k.log.Debugf("Handing off newly generated SURB-Reply: %v (Src:%v)", respPkt.ID, pkt.ID)
k.glue.Scheduler().OnPacket(respPkt)
} else if resp != nil {
// This is silly and I'm not sure why anyone will do this, but
// there's nothing that can be done at this point, the Kaetzchen
// implementation should have caught this.
k.log.Debugf("Kaetzchen message: %v (Has reply but no SURB)", pkt.ID)
}
kaetzchenRequestsTimer.ObserveDuration()
}
func (k *KaetzchenWorker) KaetzchenForPKI() map[string]map[string]interface{} {
if len(k.kaetzchen) == 0 {
return nil
}
m := make(map[string]map[string]interface{})
for _, v := range k.kaetzchen {
m[v.Capability()] = v.Parameters()
}
return m
}
func New(glue glue.Glue) (*KaetzchenWorker, error) {
kaetzchenWorker := KaetzchenWorker{
glue: glue,
log: glue.LogBackend().GetLogger("kaetzchen_worker"),
ch: channels.NewInfiniteChannel(),
kaetzchen: make(map[[sConstants.RecipientIDLength]byte]Kaetzchen),
}
// Initialize the internal Kaetzchen.
capaMap := make(map[string]bool)
for _, v := range glue.Config().Provider.Kaetzchen {
capa := v.Capability
if v.Disable {
kaetzchenWorker.log.Noticef("Skipping disabled Kaetzchen: '%v'.", capa)
continue
}
ctor, ok := BuiltInCtors[capa]
if !ok {
return nil, fmt.Errorf("provider: Kaetzchen: Unsupported capability: '%v'", capa)
}
k, err := ctor(v, glue)
if err != nil {
return nil, err
}
if err = kaetzchenWorker.registerKaetzchen(k); err != nil {
return nil, err
}
if capaMap[capa] {
return nil, fmt.Errorf("provider: Kaetzchen '%v' registered more than once", capa)
}
capaMap[capa] = true
}
// Start the workers.
for i := 0; i < glue.Config().Debug.NumKaetzchenWorkers; i++ {
kaetzchenWorker.log.Noticef("Starting Kaetzchen worker: %d", i)
kaetzchenWorker.Go(kaetzchenWorker.worker)
}
return &kaetzchenWorker, nil
}