don't panic 🤓

fixes #93

handshake/crypto_setup.go

@@ -16,7 +16,7 @@ import (
 type KeyDerivationFunction func(forwardSecure bool, sharedSecret, nonces []byte, connID protocol.ConnectionID, chlo []byte, scfg []byte, cert []byte) (crypto.AEAD, error)
 
 // KeyExchangeFunction is used to make a new KEX
-type KeyExchangeFunction func() crypto.KeyExchange
+type KeyExchangeFunction func() (crypto.KeyExchange, error)
 
 // The CryptoSetup handles all things crypto for the Session
 type CryptoSetup struct {
@@ -44,10 +44,10 @@ type CryptoSetup struct {
 var _ crypto.AEAD = &CryptoSetup{}
 
 // NewCryptoSetup creates a new CryptoSetup instance
-func NewCryptoSetup(connID protocol.ConnectionID, version protocol.VersionNumber, scfg *ServerConfig, cryptoStream utils.Stream, connectionParametersManager *ConnectionParametersManager, aeadChanged chan struct{}) *CryptoSetup {
+func NewCryptoSetup(connID protocol.ConnectionID, version protocol.VersionNumber, scfg *ServerConfig, cryptoStream utils.Stream, connectionParametersManager *ConnectionParametersManager, aeadChanged chan struct{}) (*CryptoSetup, error) {
 	nonce := make([]byte, 32)
 	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
-		panic(err)
+		return nil, err
 	}
 	return &CryptoSetup{
 		connID:                      connID,
@@ -59,7 +59,7 @@ func NewCryptoSetup(connID protocol.ConnectionID, version protocol.VersionNumber
 		cryptoStream:                cryptoStream,
 		connectionParametersManager: connectionParametersManager,
 		aeadChanged:                 aeadChanged,
-	}
+	}, nil
 }
 
 // HandleCryptoStream reads and writes messages on the crypto stream
@@ -219,7 +219,10 @@ func (h *CryptoSetup) handleCHLO(sni string, data []byte, cryptoData map[Tag][]b
 	}
 
 	// Generate a new curve instance to derive the forward secure key
-	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

handshake/crypto_setup_test.go

@@ -104,16 +104,19 @@ var _ = Describe("Crypto setup", func() {
 	)
 
 	BeforeEach(func() {
+		var err error
 		aeadChanged = make(chan struct{}, 1)
 		stream = &mockStream{}
 		kex = &mockKEX{}
 		signer = &mockSigner{}
-		scfg = NewServerConfig(kex, signer)
+		scfg, err = NewServerConfig(kex, signer)
+		Expect(err).NotTo(HaveOccurred())
 		v := protocol.SupportedVersions[len(protocol.SupportedVersions)-1]
 		cpm = NewConnectionParamatersManager()
-		cs = NewCryptoSetup(protocol.ConnectionID(42), v, scfg, stream, cpm, aeadChanged)
+		cs, err = NewCryptoSetup(protocol.ConnectionID(42), v, scfg, stream, cpm, aeadChanged)
+		Expect(err).NotTo(HaveOccurred())
 		cs.keyDerivation = mockKeyDerivation
-		cs.keyExchange = func() crypto.KeyExchange { return &mockKEX{ephermal: true} }
+		cs.keyExchange = func() (crypto.KeyExchange, error) { return &mockKEX{ephermal: true}, nil }
 	})
 
 	It("has a nonce", func() {

handshake/server_config.go

@@ -16,17 +16,17 @@ type ServerConfig struct {
 }
 
 // NewServerConfig creates a new server config
-func NewServerConfig(kex crypto.KeyExchange, signer crypto.Signer) *ServerConfig {
+func NewServerConfig(kex crypto.KeyExchange, signer crypto.Signer) (*ServerConfig, error) {
 	id := make([]byte, 16)
 	_, err := io.ReadFull(rand.Reader, id)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 	return &ServerConfig{
 		kex:    kex,
 		signer: signer,
 		ID:     id,
-	}
+	}, nil
 }
 
 // Get the server config binary representation

handshake/server_config_test.go

@@ -16,8 +16,11 @@ var _ = Describe("ServerConfig", func() {
 	)
 
 	BeforeEach(func() {
-		kex = crypto.NewCurve25519KEX()
-		scfg = NewServerConfig(kex, nil)
+		var err error
+		kex, err = crypto.NewCurve25519KEX()
+		Expect(err).NotTo(HaveOccurred())
+		scfg, err = NewServerConfig(kex, nil)
+		Expect(err).NotTo(HaveOccurred())
 	})
 
 	It("gets the proper binary representation", func() {