kms.go

// This package kms implements a simplistic key managment system (kms) for
// Quantum Key Distribution Networks (QKDN) which is a simple emulated KMS. x
// It relies on the emulated quantum link out of the quantumlayer package

package kms

import (
	"crypto/rand"
	"log"
	"math/big"
	"sync"
	"time"

	"code.fbi.h-da.de/m.stiemerling/proto-kms/quantumlayer"
	"github.com/google/uuid"
)

type Qkdnkms interface {
	AddQuantumElement() *QuantumElement
	GlobalKeyHandler(time.Duration) error
	AddPeer(kmsPeerSocket string)
	RemovePeer(kmsPeerSocket string)
}

type qlElementId uint64
type qlElementLinkID int

// The general emulated KMS
type eKMS struct {
	kmsName         string
	kmsUUID         uuid.UUID
	qleMapMutex     sync.Mutex
	QuantumElements map[qlElementId]*QuantumElement
	KmsPeers        map[string]*kmsPeer
}

// Will keep information about the quantum elements that this eKMS is talking to
// This actually constitutes a quantum element with only a single link
type QuantumElement struct {
	qlID               qlElementId
	QuantumElementLink *quantumlayer.QuantumlayerEmuPRNG // contains information about the quantum links
	//key stores go here
	keyStoreLocal  *kmsKeyStore // the keys this local entity has produced and are ready to use
	keyStoreRemote *kmsKeyStore // the keys th remote entity (peer) has produced and are ready to use
}

func NeweKMS(kmsName string, kmsUUID uuid.UUID) (newekms *eKMS) {

	return &eKMS{
		kmsName:         kmsName,
		kmsUUID:         kmsUUID,
		QuantumElements: make(map[qlElementId]*QuantumElement),
	}
}

func (kms *eKMS) AddQuantumElement(kmsUDPAddrr string) *QuantumElement {

	//Get an emulated Quantumlayer
	ql := quantumlayer.NewQuantumlayerEmuPRNG()
	ql.PowerOn(kmsUDPAddrr)

	ksl := kmsKeyStore{
		keyStore: make(map[string]kmsKSElement),
	}
	ksr := kmsKeyStore{
		keyStore: make(map[string]kmsKSElement),
	}

	qle := QuantumElement{
		QuantumElementLink: ql,
		keyStoreLocal:      &ksl,
		keyStoreRemote:     &ksr,
	}

	// generate a ID for this quantum element that is unique locally
	var randError error
	qle.qlID, randError = kms.GenerateNewQleID()
	if randError != nil {
		log.Fatalf("GenerateNewQleID: %s", randError)
		return nil
	}

	kms.QuantumElements[qle.qlID] = &qle

	return &qle
}

func (kms *eKMS) GlobalKeyHandler(waitTime time.Duration) error {

	// periodically walk through QuantumElements and retrieve their
	// - local key bulk buffer
	// - remote key bulk buffer
	// feed this into the corresponding key buffers of the kmss
	for {
		for currentQE := range kms.QuantumElements {
			log.Printf("%s GlobalKeyHandler reading...\n", kms.kmsName)

			bulkKeysLocal, err := kms.QuantumElements[currentQE].QuantumElementLink.GetKeyBatchLocal()
			if err != nil {
				log.Printf("%s failed to retrieve local bulkkeys with error %s", kms.kmsName, err)
			} else {
				// process bulkKeysLocal
				log.Printf("%s produced %d bytes of key locally", kms.kmsName, bulkKeysLocal.BulkKeyLength)
				kms.QuantumElements[currentQE].keyStoreLocal.KeyChopper256Bit(&bulkKeysLocal)

			}

			bulkKeysRemote, err := kms.QuantumElements[currentQE].QuantumElementLink.GetKeyBatchPeer()
			if err != nil {
				log.Printf("%s failed to retrieve remote bulkkeys with error %s", kms.kmsName, err)
			} else {
				// process bulkKeysRemote
				log.Printf("%s received %d bytes of key from remote peer", kms.kmsName, bulkKeysRemote.BulkKeyLength)
				kms.QuantumElements[currentQE].keyStoreRemote.KeyChopper256Bit(&bulkKeysRemote)
			}
		}
		time.Sleep(waitTime)
	}
}

// This has a design flaw, as the generated ID is returned to the calling function and used there.
// However, when being used a potential other caller might received the same qlElementId
// TODO/XXX: This would be collision and must be eventually avoided
func (kms *eKMS) GenerateNewQleID() (qlElementId, error) {
	for { // this needs a condiction to stop!
		bigRand, randError := rand.Int(rand.Reader, big.NewInt(100000))
		if randError != nil {
			return 0, randError
		}

		propopsedQlElementID := qlElementId(bigRand.Uint64())

		// check if ID is already taken
		if kms.QuantumElements[propopsedQlElementID] == nil {
			return propopsedQlElementID, nil
		}
		//keep going....
	}
}