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104 lines
2.6 KiB
Go
104 lines
2.6 KiB
Go
package server
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import (
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"bufio"
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"bytes"
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"crypto"
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"encoding/base64"
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"errors"
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"fmt"
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"io"
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"net"
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"net/http"
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"github.com/cbeuw/Cloak/internal/common"
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"github.com/cbeuw/Cloak/internal/ecdh"
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)
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type WebSocket struct{}
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func (WebSocket) String() string { return "WebSocket" }
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func (WebSocket) processFirstPacket(reqPacket []byte, privateKey crypto.PrivateKey) (fragments authFragments, respond Responder, err error) {
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var req *http.Request
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req, err = http.ReadRequest(bufio.NewReader(bytes.NewBuffer(reqPacket)))
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if err != nil {
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err = fmt.Errorf("failed to parse first HTTP GET: %v", err)
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return
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}
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var hiddenData []byte
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hiddenData, err = base64.StdEncoding.DecodeString(req.Header.Get("hidden"))
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fragments, err = WebSocket{}.unmarshalHidden(hiddenData, privateKey)
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if err != nil {
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err = fmt.Errorf("failed to unmarshal hidden data from WS into authFragments: %v", err)
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return
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}
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respond = WebSocket{}.makeResponder(reqPacket, fragments.sharedSecret)
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return
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}
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func (WebSocket) makeResponder(reqPacket []byte, sharedSecret [32]byte) Responder {
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respond := func(originalConn net.Conn, sessionKey [32]byte, randSource io.Reader) (preparedConn net.Conn, err error) {
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handler := newWsHandshakeHandler()
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// For an explanation of the following 3 lines, see the comments in websocketAux.go
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http.Serve(newWsAcceptor(originalConn, reqPacket), handler)
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<-handler.finished
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preparedConn = handler.conn
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nonce := make([]byte, 12)
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common.RandRead(randSource, nonce)
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// reply: [12 bytes nonce][32 bytes encrypted session key][16 bytes authentication tag]
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encryptedKey, err := common.AESGCMEncrypt(nonce, sharedSecret[:], sessionKey[:]) // 32 + 16 = 48 bytes
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if err != nil {
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err = fmt.Errorf("failed to encrypt reply: %v", err)
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return
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}
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reply := append(nonce, encryptedKey...)
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_, err = preparedConn.Write(reply)
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if err != nil {
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err = fmt.Errorf("failed to write reply: %v", err)
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preparedConn.Close()
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return
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}
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return
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}
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return respond
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}
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var ErrBadGET = errors.New("non (or malformed) HTTP GET")
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func (WebSocket) unmarshalHidden(hidden []byte, staticPv crypto.PrivateKey) (fragments authFragments, err error) {
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if len(hidden) < 96 {
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err = ErrBadGET
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return
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}
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copy(fragments.randPubKey[:], hidden[0:32])
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ephPub, ok := ecdh.Unmarshal(fragments.randPubKey[:])
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if !ok {
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err = ErrInvalidPubKey
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return
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}
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var sharedSecret []byte
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sharedSecret, err = ecdh.GenerateSharedSecret(staticPv, ephPub)
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if err != nil {
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return
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}
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copy(fragments.sharedSecret[:], sharedSecret)
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if len(hidden[32:]) != 64 {
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err = fmt.Errorf("%v: %v", ErrCiphertextLength, len(hidden[32:]))
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return
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}
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copy(fragments.ciphertextWithTag[:], hidden[32:])
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return
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}
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