[FAB-7674] use buffers instead of temporary files

GenerateCertificatesOrPanic was using temporary files when a simple
buffer is sufficient. This resulted in untracked files getting left
behind when tests failed.

Change-Id: I2bdcafde387509a00563315ddd11eccbb7e95584
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>

gossip/comm/crypto.go

@@ -13,39 +13,21 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/pem"
-	"fmt"
 	"math/big"
-	"os"
 
 	"github.com/hyperledger/fabric/common/util"
-	gutil "github.com/hyperledger/fabric/gossip/util"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/peer"
 )
 
-func writeFile(filename string, keyType string, data []byte) error {
-	f, err := os.Create(filename)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-	return pem.Encode(f, &pem.Block{Type: keyType, Bytes: data})
-}
-
 // GenerateCertificatesOrPanic generates a a random pair of public and private keys
 // and return TLS certificate
 func GenerateCertificatesOrPanic() tls.Certificate {
-	privKeyFile := fmt.Sprintf("key.%d.priv", gutil.RandomUInt64())
-	certKeyFile := fmt.Sprintf("cert.%d.pub", gutil.RandomUInt64())
-
-	defer os.Remove(privKeyFile)
-	defer os.Remove(certKeyFile)
 	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	if err != nil {
 		panic(err)
 	}
-
 	sn, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
 	if err != nil {
 		panic(err)
@@ -59,19 +41,13 @@ func GenerateCertificatesOrPanic() tls.Certificate {
 	if err != nil {
 		panic(err)
 	}
-	err = writeFile(certKeyFile, "CERTIFICATE", rawBytes)
-	if err != nil {
-		panic(err)
-	}
 	privBytes, err := x509.MarshalECPrivateKey(privateKey)
 	if err != nil {
 		panic(err)
 	}
-	err = writeFile(privKeyFile, "EC PRIVATE KEY", privBytes)
-	if err != nil {
-		panic(err)
-	}
-	cert, err := tls.LoadX509KeyPair(certKeyFile, privKeyFile)
+	encodedCert := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: rawBytes})
+	encodedKey := pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: privBytes})
+	cert, err := tls.X509KeyPair(encodedCert, encodedKey)
 	if err != nil {
 		panic(err)
 	}