fabric-samples/asset-transfer-basic/application-gateway-go/internal/grpc/connect.go

package grpc

import (
	"crypto/x509"
	"fmt"
	"os"
	"path"
	"time"

	"github.com/hyperledger/fabric-gateway/pkg/client"
	"github.com/hyperledger/fabric-gateway/pkg/hash"
	"github.com/hyperledger/fabric-gateway/pkg/identity"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
)

const (
	rootPath     = "/root/go/src/github.com/BennielAllan/fabric-samples"
	mspID        = "Org1MSP"
	cryptoPath   = rootPath + "/test-network/organizations/peerOrganizations/org1.example.com"
	certPath     = cryptoPath + "/users/User1@org1.example.com/msp/signcerts"
	keyPath      = cryptoPath + "/users/User1@org1.example.com/msp/keystore"
	tlsCertPath  = cryptoPath + "/peers/peer0.org1.example.com/tls/ca.crt"
	peerEndpoint = "dns:///localhost:7051"
	gatewayPeer  = "peer0.org1.example.com"
)

var (
	ClientConnection *grpc.ClientConn
	GateWay          *client.Gateway
	Contract         *client.Contract
)

func InitGWConnect() {
	// The gRPC client connection should be shared by all Gateway connections to this endpoint
	ClientConnection = newGrpcConnection()

	id := newIdentity()
	sign := newSign()

	// Create a Gateway connection for a specific client identity
	var err error
	GateWay, err = client.Connect(
		id,
		client.WithSign(sign),
		client.WithHash(hash.SHA256),
		client.WithClientConnection(ClientConnection),
		// Default timeouts for different gRPC calls
		client.WithEvaluateTimeout(5*time.Second),
		client.WithEndorseTimeout(15*time.Second),
		client.WithSubmitTimeout(5*time.Second),
		client.WithCommitStatusTimeout(1*time.Minute),
	)
	if err != nil {
		panic(err)
	}
	// ./network.sh deployCC -ccn ledger -ccp /root/go/src/github.com/BennielAllan/fabric-samples/asset-transfer-ledger-queries/chaincode-go/ -ccl go
	// Override default values for chaincode and channel name as they may differ in testing contexts.
	chaincodeName := "ledger"
	if ccname := os.Getenv("CHAINCODE_NAME"); ccname != "" {
		chaincodeName = ccname
	}

	channelName := "mychannel"
	if cname := os.Getenv("CHANNEL_NAME"); cname != "" {
		channelName = cname
	}

	network := GateWay.GetNetwork(channelName)
	Contract = network.GetContract(chaincodeName)
}

func CloseGWConnect() {
	GateWay.Close()
	ClientConnection.Close()
}

// newGrpcConnection creates a gRPC connection to the Gateway server.
func newGrpcConnection() *grpc.ClientConn {
	certificatePEM, err := os.ReadFile(tlsCertPath)
	if err != nil {
		panic(fmt.Errorf("failed to read TLS certifcate file: %w", err))
	}

	certificate, err := identity.CertificateFromPEM(certificatePEM)
	if err != nil {
		panic(err)
	}

	certPool := x509.NewCertPool()
	certPool.AddCert(certificate)
	transportCredentials := credentials.NewClientTLSFromCert(certPool, gatewayPeer)

	connection, err := grpc.NewClient(peerEndpoint, grpc.WithTransportCredentials(transportCredentials))
	if err != nil {
		panic(fmt.Errorf("failed to create gRPC connection: %w", err))
	}

	return connection
}

// newIdentity creates a client identity for this Gateway connection using an X.509 certificate.
func newIdentity() *identity.X509Identity {
	certificatePEM, err := readFirstFile(certPath)
	if err != nil {
		panic(fmt.Errorf("failed to read certificate file: %w", err))
	}

	certificate, err := identity.CertificateFromPEM(certificatePEM)
	if err != nil {
		panic(err)
	}

	id, err := identity.NewX509Identity(mspID, certificate)
	if err != nil {
		panic(err)
	}

	return id
}

// newSign creates a function that generates a digital signature from a message digest using a private key.
func newSign() identity.Sign {
	privateKeyPEM, err := readFirstFile(keyPath)
	if err != nil {
		panic(fmt.Errorf("failed to read private key file: %w", err))
	}

	privateKey, err := identity.PrivateKeyFromPEM(privateKeyPEM)
	if err != nil {
		panic(err)
	}

	sign, err := identity.NewPrivateKeySign(privateKey)
	if err != nil {
		panic(err)
	}

	return sign
}

func readFirstFile(dirPath string) ([]byte, error) {
	dir, err := os.Open(dirPath)
	if err != nil {
		return nil, err
	}

	fileNames, err := dir.Readdirnames(1)
	if err != nil {
		return nil, err
	}

	return os.ReadFile(path.Join(dirPath, fileNames[0]))
}