mirror of
https://github.com/cbeuw/Cloak.git
synced 2024-11-11 13:11:03 +00:00
104 lines
3.0 KiB
Go
104 lines
3.0 KiB
Go
package client
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import (
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"crypto/rand"
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"encoding/binary"
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"github.com/cbeuw/Cloak/internal/util"
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"net"
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log "github.com/sirupsen/logrus"
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)
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type clientHelloFields struct {
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random []byte
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sessionId []byte
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x25519KeyShare []byte
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sni []byte
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}
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type browser interface {
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composeClientHello(clientHelloFields) []byte
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}
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func makeServerName(serverName string) []byte {
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serverNameListLength := make([]byte, 2)
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binary.BigEndian.PutUint16(serverNameListLength, uint16(len(serverName)+3))
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serverNameType := []byte{0x00} // host_name
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serverNameLength := make([]byte, 2)
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binary.BigEndian.PutUint16(serverNameLength, uint16(len(serverName)))
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ret := make([]byte, 2+1+2+len(serverName))
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copy(ret[0:2], serverNameListLength)
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copy(ret[2:3], serverNameType)
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copy(ret[3:5], serverNameLength)
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copy(ret[5:], serverName)
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return ret
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}
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// addExtensionRecord, add type, length to extension data
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func addExtRec(typ []byte, data []byte) []byte {
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length := make([]byte, 2)
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binary.BigEndian.PutUint16(length, uint16(len(data)))
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ret := make([]byte, 2+2+len(data))
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copy(ret[0:2], typ)
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copy(ret[2:4], length)
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copy(ret[4:], data)
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return ret
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}
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func unmarshalAuthenticationInfo(ai authenticationPayload, serverName string) (ret clientHelloFields) {
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// random is marshalled ephemeral pub key 32 bytes
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// The authentication ciphertext and its tag are then distributed among SessionId and X25519KeyShare
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ret.random = ai.randPubKey[:]
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ret.sessionId = ai.ciphertextWithTag[0:32]
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ret.x25519KeyShare = ai.ciphertextWithTag[32:64]
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ret.sni = makeServerName(serverName)
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return
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}
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type DirectTLS struct {
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Transport
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}
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func (DirectTLS) HasRecordLayer() bool { return true }
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func (DirectTLS) UnitReadFunc() func(net.Conn, []byte) (int, error) { return util.ReadTLS }
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// PrepareConnection handles the TLS handshake for a given conn and returns the sessionKey
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// if the server proceed with Cloak authentication
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func (DirectTLS) PrepareConnection(sta *State, conn net.Conn) (preparedConn net.Conn, sessionKey []byte, err error) {
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preparedConn = conn
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payload, sharedSecret := makeAuthenticationPayload(sta, rand.Reader)
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chOnly := sta.browser.composeClientHello(unmarshalAuthenticationInfo(payload, sta.ServerName))
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chWithRecordLayer := util.AddRecordLayer(chOnly, []byte{0x16}, []byte{0x03, 0x01})
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_, err = preparedConn.Write(chWithRecordLayer)
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if err != nil {
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return
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}
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log.Trace("client hello sent successfully")
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buf := make([]byte, 1024)
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log.Trace("waiting for ServerHello")
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_, err = util.ReadTLS(preparedConn, buf)
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if err != nil {
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return
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}
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encrypted := append(buf[11:43], buf[89:121]...)
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nonce := encrypted[0:12]
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ciphertextWithTag := encrypted[12:60]
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sessionKey, err = util.AESGCMDecrypt(nonce, sharedSecret, ciphertextWithTag)
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if err != nil {
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return
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}
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for i := 0; i < 2; i++ {
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// ChangeCipherSpec and EncryptedCert (in the format of application data)
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_, err = util.ReadTLS(preparedConn, buf)
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if err != nil {
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return
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}
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}
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return preparedConn, sessionKey, nil
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}
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