correctly handle errors when creating a new gQUIC key exchange

internal/handshake/crypto_setup_server.go

@@ -19,7 +19,7 @@ import (
 type QuicCryptoKeyDerivationFunction func(forwardSecure bool, sharedSecret, nonces []byte, connID protocol.ConnectionID, chlo []byte, scfg []byte, cert []byte, divNonce []byte, pers protocol.Perspective) (crypto.AEAD, error)
 
 // KeyExchangeFunction is used to make a new KEX
-type KeyExchangeFunction func() crypto.KeyExchange
+type KeyExchangeFunction func() (crypto.KeyExchange, error)
 
 // The CryptoSetupServer handles all things crypto for the Session
 type cryptoSetupServer struct {
@@ -405,7 +405,10 @@ func (h *cryptoSetupServer) handleCHLO(sni string, data []byte, cryptoData map[T
 	var fsNonce bytes.Buffer
 	fsNonce.Write(clientNonce)
 	fsNonce.Write(serverNonce)
-	ephermalKex := h.keyExchange()
+	ephermalKex, err := h.keyExchange()
+	if err != nil {
+		return nil, err
+	}
 	ephermalSharedSecret, err := ephermalKex.CalculateSharedKey(cryptoData[TagPUBS])
 	if err != nil {
 		return nil, err

internal/handshake/crypto_setup_server_test.go

@@ -179,7 +179,7 @@ var _ = Describe("Server Crypto Setup", func() {
 		sourceAddrValid = true
 		cs.acceptSTKCallback = func(_ net.Addr, _ *Cookie) bool { return sourceAddrValid }
 		cs.keyDerivation = mockQuicCryptoKeyDerivation
-		cs.keyExchange = func() crypto.KeyExchange { return &mockKEX{ephermal: true} }
+		cs.keyExchange = func() (crypto.KeyExchange, error) { return &mockKEX{ephermal: true}, nil }
 		cs.nullAEAD = mockcrypto.NewMockAEAD(mockCtrl)
 		cs.cryptoStream = stream
 	})

internal/handshake/ephermal_cache.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/lucas-clemente/quic-go/internal/crypto"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
-	"github.com/lucas-clemente/quic-go/internal/utils"
 )
 
 var (
@@ -24,13 +23,13 @@ var (
 // used for all connections for 60 seconds is negligible. Thus we can amortise
 // the Diffie-Hellman key generation at the server over all the connections in a
 // small time span.
-func getEphermalKEX() (res crypto.KeyExchange) {
+func getEphermalKEX() (crypto.KeyExchange, error) {
 	kexMutex.RLock()
-	res = kexCurrent
+	res := kexCurrent
 	t := kexCurrentTime
 	kexMutex.RUnlock()
 	if res != nil && time.Since(t) < kexLifetime {
-		return res
+		return res, nil
 	}
 
 	kexMutex.Lock()
@@ -39,12 +38,11 @@ func getEphermalKEX() (res crypto.KeyExchange) {
 	if kexCurrent == nil || time.Since(kexCurrentTime) > kexLifetime {
 		kex, err := crypto.NewCurve25519KEX()
 		if err != nil {
-			utils.Errorf("could not set KEX: %s", err.Error())
-			return kexCurrent
+			return nil, err
 		}
 		kexCurrent = kex
 		kexCurrentTime = time.Now()
-		return kexCurrent
+		return kexCurrent, nil
 	}
-	return kexCurrent
+	return kexCurrent, nil
 }

internal/handshake/ephermal_cache_test.go

@@ -3,7 +3,6 @@ package handshake
 import (
 	"time"
 
-	"github.com/lucas-clemente/quic-go/internal/crypto"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -11,9 +10,11 @@ import (
 
 var _ = Describe("Ephermal KEX", func() {
 	It("has a consistent KEX", func() {
-		kex1 := getEphermalKEX()
+		kex1, err := getEphermalKEX()
+		Expect(err).ToNot(HaveOccurred())
 		Expect(kex1).ToNot(BeNil())
-		kex2 := getEphermalKEX()
+		kex2, err := getEphermalKEX()
+		Expect(err).ToNot(HaveOccurred())
 		Expect(kex2).ToNot(BeNil())
 		Expect(kex1).To(Equal(kex2))
 	})
@@ -23,8 +24,12 @@ var _ = Describe("Ephermal KEX", func() {
 		defer func() {
 			kexLifetime = protocol.EphermalKeyLifetime
 		}()
-		kex := getEphermalKEX()
+		kex, err := getEphermalKEX()
+		Expect(err).ToNot(HaveOccurred())
 		Expect(kex).ToNot(BeNil())
-		Eventually(func() crypto.KeyExchange { return getEphermalKEX() }).ShouldNot(Equal(kex))
+		time.Sleep(kexLifetime)
+		kex2, err := getEphermalKEX()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(kex2).ToNot(Equal(kex))
 	})
 })