Minor refactors to remove unnecessary function

.gitignore

@@ -2,3 +2,5 @@ corpus/
 suppressions/
 crashers/
 *.zip
+.idea/
+build/

internal/client/TLS.go

@@ -13,14 +13,14 @@ type clientHelloFields struct {
 	random         []byte
 	sessionId      []byte
 	x25519KeyShare []byte
-	sni            []byte
+	serverName     string
 }
 
 type browser interface {
 	composeClientHello(clientHelloFields) []byte
 }
 
-func makeServerName(serverName string) []byte {
+func generateSNI(serverName string) []byte {
 	serverNameListLength := make([]byte, 2)
 	binary.BigEndian.PutUint16(serverNameListLength, uint16(len(serverName)+3))
 	serverNameType := []byte{0x00} // host_name
@@ -45,16 +45,6 @@ func addExtRec(typ []byte, data []byte) []byte {
 	return ret
 }
 
-func genStegClientHello(ai authenticationPayload, serverName string) (ret clientHelloFields) {
-	// random is marshalled ephemeral pub key 32 bytes
-	// The authentication ciphertext and its tag are then distributed among SessionId and X25519KeyShare
-	ret.random = ai.randPubKey[:]
-	ret.sessionId = ai.ciphertextWithTag[0:32]
-	ret.x25519KeyShare = ai.ciphertextWithTag[32:64]
-	ret.sni = makeServerName(serverName)
-	return
-}
-
 type DirectTLS struct {
 	*common.TLSConn
 	browser browser
@@ -64,7 +54,16 @@ type DirectTLS struct {
 // if the server proceed with Cloak authentication
 func (tls *DirectTLS) Handshake(rawConn net.Conn, authInfo AuthInfo) (sessionKey [32]byte, err error) {
 	payload, sharedSecret := makeAuthenticationPayload(authInfo)
-	chOnly := tls.browser.composeClientHello(genStegClientHello(payload, authInfo.MockDomain))
+
+	// random is marshalled ephemeral pub key 32 bytes
+	// The authentication ciphertext and its tag are then distributed among SessionId and X25519KeyShare
+	fields := clientHelloFields{
+		random:         payload.randPubKey[:],
+		sessionId:      payload.ciphertextWithTag[0:32],
+		x25519KeyShare: payload.ciphertextWithTag[32:64],
+		serverName:     authInfo.MockDomain,
+	}
+	chOnly := tls.browser.composeClientHello(fields)
 	chWithRecordLayer := common.AddRecordLayer(chOnly, common.Handshake, common.VersionTLS11)
 	_, err = rawConn.Write(chWithRecordLayer)
 	if err != nil {

internal/client/TLS_test.go

@@ -33,6 +33,6 @@ func TestMakeServerName(t *testing.T) {
 	}
 
 	for _, p := range pairs {
-		assert.Equal(t, p.target, makeServerName(p.serverName))
+		assert.Equal(t, p.target, generateSNI(p.serverName))
 	}
 }

internal/client/chrome.go

@@ -21,7 +21,7 @@ func makeGREASE() []byte {
 	return doubleGREASE
 }
 
-func (c *Chrome) composeExtensions(sni []byte, keyShare []byte) []byte {
+func (c *Chrome) composeExtensions(serverName string, keyShare []byte) []byte {
 
 	makeSupportedGroups := func() []byte {
 		suppGroupListLen := []byte{0x00, 0x08}
@@ -48,7 +48,7 @@ func (c *Chrome) composeExtensions(sni []byte, keyShare []byte) []byte {
 
 	var ext [17][]byte
 	ext[0] = addExtRec(makeGREASE(), nil)                           // First GREASE
-	ext[1] = addExtRec([]byte{0x00, 0x00}, sni)                   // server name indication
+	ext[1] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
 	ext[2] = addExtRec([]byte{0x00, 0x17}, nil)                     // extended_master_secret
 	ext[3] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})            // renegotiation_info
 	ext[4] = addExtRec([]byte{0x00, 0x0a}, makeSupportedGroups())   // supported groups
@@ -87,12 +87,12 @@ func (c *Chrome) composeClientHello(hd clientHelloFields) (ch []byte) {
 	clientHello[3] = hd.random                // random
 	clientHello[4] = []byte{0x20}             // session id length 32
 	clientHello[5] = hd.sessionId             // session id
-	clientHello[6] = []byte{0x00, 0x20}       // cipher suites length 34
+	clientHello[6] = []byte{0x00, 0x20}       // cipher suites length 32
 	cipherSuites, _ := hex.DecodeString("130113021303c02bc02fc02cc030cca9cca8c013c014009c009d002f0035")
 	clientHello[7] = append(makeGREASE(), cipherSuites...) // cipher suites
 	clientHello[8] = []byte{0x01}                          // compression methods length 1
 	clientHello[9] = []byte{0x00}                          // compression methods
-	clientHello[11] = c.composeExtensions(hd.sni, hd.x25519KeyShare)
+	clientHello[11] = c.composeExtensions(hd.serverName, hd.x25519KeyShare)
 	clientHello[10] = []byte{0x00, 0x00} // extensions length 403
 	binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
 	var ret []byte

internal/client/chrome_test.go

@@ -30,9 +30,7 @@ func TestComposeExtension(t *testing.T) {
 	serverName := "github.com"
 	keyShare, _ := hex.DecodeString("690f074f5c01756982269b66d58c90c47dc0f281d654c7b2c16f63c9033f5604")
 
-	sni := makeServerName(serverName)
+	result := (&Chrome{}).composeExtensions(serverName, keyShare)
-
-	result := (&Chrome{}).composeExtensions(sni, keyShare)
 	target, _ := hex.DecodeString("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")
 	for p := 0; p < len(result); p++ {
 		if result[p] != target[p] {

internal/client/firefox.go

@@ -10,7 +10,7 @@ import (
 
 type Firefox struct{}
 
-func (f *Firefox) composeExtensions(SNI []byte, keyShare []byte) []byte {
+func (f *Firefox) composeExtensions(serverName string, keyShare []byte) []byte {
 	composeKeyShare := func(hidden []byte) []byte {
 		ret := make([]byte, 107)
 		ret[0], ret[1] = 0x00, 0x69 // length 105
@@ -24,7 +24,7 @@ func (f *Firefox) composeExtensions(SNI []byte, keyShare []byte) []byte {
 	}
 	// extension length is always 399, and server name length is variable
 	var ext [12][]byte
-	ext[0] = addExtRec([]byte{0x00, 0x00}, SNI)          // server name indication
+	ext[0] = addExtRec([]byte{0x00, 0x00}, generateSNI(serverName)) // server name indication
 	ext[1] = addExtRec([]byte{0x00, 0x17}, nil)                     // extended_master_secret
 	ext[2] = addExtRec([]byte{0xff, 0x01}, []byte{0x00})            // renegotiation_info
 	suppGroup, _ := hex.DecodeString("000c001d00170018001901000101")
@@ -63,7 +63,7 @@ func (f *Firefox) composeClientHello(hd clientHelloFields) (ch []byte) {
 	clientHello[8] = []byte{0x01} // compression methods length 1
 	clientHello[9] = []byte{0x00} // compression methods
 
-	clientHello[11] = f.composeExtensions(hd.sni, hd.x25519KeyShare)
+	clientHello[11] = f.composeExtensions(hd.serverName, hd.x25519KeyShare)
 	clientHello[10] = []byte{0x00, 0x00} // extensions length
 	binary.BigEndian.PutUint16(clientHello[10], uint16(len(clientHello[11])))
 

internal/client/firefox_test.go

@@ -11,8 +11,8 @@ func TestComposeExtensions(t *testing.T) {
 
 	serverName := "consent.google.com"
 	keyShare, _ := hex.DecodeString("8d8ea1b80430b7710b65f0d89b0144a5eeb218709ce6613d4fc8bfb117657c15")
-	sni := makeServerName(serverName)
+
-	result := (&Firefox{}).composeExtensions(sni, keyShare)
+	result := (&Firefox{}).composeExtensions(serverName, keyShare)
 	// skip random secp256r1
 	if !bytes.Equal(result[:133], target[:133]) || !bytes.Equal(result[198:], target[198:]) {
 		t.Errorf("got %x", result)