[tor-commits] [goptlib/master] Replace the SOCKS4a listener with a SOCKS5 listener.

dcf at torproject.org dcf at torproject.org
Mon May 2 07:21:43 UTC 2016


commit 93bcaf4c7d5b8e3dc29142ca50f96197639c38cf
Author: Yawning Angel <yawning at schwanenlied.me>
Date:   Fri Apr 3 10:23:44 2015 +0000

    Replace the SOCKS4a listener with a SOCKS5 listener.
    
    The change is designed to be transparent to calling code and implements
    enough of RFC1928/RFC1929 such that pluggable transports can be written.
    
    Notable incompatibilities/limitations:
     * GSSAPI authentication is not supported.
     * BND.ADDR/BND.PORT in responses is always "0.0.0.0:0" instead of the
       bound address/port of the outgoing socket.
     * RFC1929 Username/Password authentication is setup exclusively for
       pluggable transport arguments.
     * The BIND and UDP ASSOCIATE commands are not supported.
---
 pt.go         |   5 +-
 socks.go      | 386 +++++++++++++++++++++++++++++++++++++-------
 socks_test.go | 510 +++++++++++++++++++++++++++++++++++++++++-----------------
 3 files changed, 685 insertions(+), 216 deletions(-)

diff --git a/pt.go b/pt.go
index d2e7dc1..45cf67f 100644
--- a/pt.go
+++ b/pt.go
@@ -119,10 +119,11 @@
 // Extended ORPort Authentication:
 // https://gitweb.torproject.org/torspec.git/tree/proposals/217-ext-orport-auth.txt.
 //
-// The package implements a SOCKS4a server sufficient for a Tor client transport
+// The package implements a SOCKS5 server sufficient for a Tor client transport
 // plugin.
 //
-// http://ftp.icm.edu.pl/packages/socks/socks4/SOCKS4.protocol
+// https://www.ietf.org/rfc/rfc1928.txt
+// https://www.ietf.org/rfc/rfc1929.txt
 package pt
 
 import (
diff --git a/socks.go b/socks.go
index 6ad6542..e4488e8 100644
--- a/socks.go
+++ b/socks.go
@@ -9,11 +9,40 @@ import (
 )
 
 const (
-	socksVersion         = 0x04
-	socksCmdConnect      = 0x01
-	socksResponseVersion = 0x00
-	socksRequestGranted  = 0x5a
-	socksRequestRejected = 0x5b
+	socksVersion = 0x05
+
+	socksAuthNoneRequired        = 0x00
+	socksAuthUsernamePassword    = 0x02
+	socksAuthNoAcceptableMethods = 0xff
+
+	socksCmdConnect = 0x01
+	socksRsv        = 0x00
+
+	socksAtypeV4         = 0x01
+	socksAtypeDomainName = 0x03
+	socksAtypeV6         = 0x04
+
+	socksAuthRFC1929Ver     = 0x01
+	socksAuthRFC1929Success = 0x00
+	socksAuthRFC1929Fail    = 0x01
+
+	socksRepSucceeded = 0x00
+	// "general SOCKS server failure"
+	SocksRepGeneralFailure = 0x01
+	// "connection not allowed by ruleset"
+	SocksRepConnectionNotAllowed = 0x02
+	// "Network unreachable"
+	SocksRepNetworkUnreachable = 0x03
+	// "Host unreachable"
+	SocksRepHostUnreachable = 0x04
+	// "Connection refused"
+	SocksRepConnectionRefused = 0x05
+	// "TTL expired"
+	SocksRepTTLExpired = 0x06
+	// "Command not supported"
+	SocksRepCommandNotSupported = 0x07
+	// "Address type not supported"
+	SocksRepAddressNotSupported = 0x08
 )
 
 // Put a sanity timeout on how long we wait for a SOCKS request.
@@ -25,6 +54,8 @@ type SocksRequest struct {
 	Target string
 	// The userid string sent by the client.
 	Username string
+	// The password string sent by the client.
+	Password string
 	// The parsed contents of Username as a key–value mapping.
 	Args Args
 }
@@ -36,15 +67,23 @@ type SocksConn struct {
 }
 
 // Send a message to the proxy client that access to the given address is
-// granted. If the IP field inside addr is not an IPv4 address, the IP portion
-// of the response will be four zero bytes.
+// granted. Addr is ignored, and "0.0.0.0:0" is always sent back for
+// BND.ADDR/BND.PORT in the SOCKS response.
 func (conn *SocksConn) Grant(addr *net.TCPAddr) error {
-	return sendSocks4aResponseGranted(conn, addr)
+	return sendSocks5ResponseGranted(conn)
 }
 
-// Send a message to the proxy client that access was rejected or failed.
+// Send a message to the proxy client that access was rejected or failed.  This
+// sends back a "General Failure" error code.  RejectReason should be used if
+// more specific error reporting is desired.
 func (conn *SocksConn) Reject() error {
-	return sendSocks4aResponseRejected(conn)
+	return conn.RejectReason(SocksRepGeneralFailure)
+}
+
+// Send a message to the proxy client that access was rejected, with the
+// specific error code indicating the reason behind the rejection.
+func (conn *SocksConn) RejectReason(reason byte) error {
+	return sendSocks5ResponseRejected(conn, reason)
 }
 
 // SocksListener wraps a net.Listener in order to read a SOCKS request on Accept.
@@ -138,7 +177,7 @@ func (ln *SocksListener) AcceptSocks() (*SocksConn, error) {
 	if err != nil {
 		return nil, err
 	}
-	conn.Req, err = readSocks4aConnect(conn)
+	conn.Req, err = socks5Handshake(conn)
 	if err != nil {
 		conn.Close()
 		return nil, err
@@ -150,58 +189,251 @@ func (ln *SocksListener) AcceptSocks() (*SocksConn, error) {
 	return conn, nil
 }
 
-// Returns "socks4", suitable to be included in a call to Cmethod.
+// Returns "socks5", suitable to be included in a call to Cmethod.
 func (ln *SocksListener) Version() string {
-	return "socks4"
+	return "socks5"
 }
 
-// Read a SOCKS4a connect request. Returns a SocksRequest.
-func readSocks4aConnect(s io.Reader) (req SocksRequest, err error) {
-	r := bufio.NewReader(s)
+// socks5handshake conducts the SOCKS5 handshake up to the point where the
+// client command is read and the proxy must open the outgoing connection.
+// Returns a SocksRequest.
+func socks5Handshake(s io.ReadWriter) (req SocksRequest, err error) {
+	rw := bufio.NewReadWriter(bufio.NewReader(s), bufio.NewWriter(s))
 
-	var h [8]byte
-	_, err = io.ReadFull(r, h[:])
-	if err != nil {
+	// Negotiate the authentication method.
+	var method byte
+	if method, err = socksNegotiateAuth(rw); err != nil {
 		return
 	}
-	if h[0] != socksVersion {
-		err = fmt.Errorf("SOCKS header had version 0x%02x, not 0x%02x", h[0], socksVersion)
+
+	// Authenticate the client.
+	if err = socksAuthenticate(rw, method, &req); err != nil {
 		return
 	}
-	if h[1] != socksCmdConnect {
-		err = fmt.Errorf("SOCKS header had command 0x%02x, not 0x%02x", h[1], socksCmdConnect)
+
+	// Read the command.
+	err = socksReadCommand(rw, &req)
+	return
+}
+
+// socksNegotiateAuth negotiates the authentication method and returns the
+// selected method as a byte.  On negotiation failures an error is returned.
+func socksNegotiateAuth(rw *bufio.ReadWriter) (method byte, err error) {
+	// Validate the version.
+	if err = socksReadByteVerify(rw, "version", socksVersion); err != nil {
 		return
 	}
 
-	var usernameBytes []byte
-	usernameBytes, err = r.ReadBytes('\x00')
-	if err != nil {
+	// Read the number of methods.
+	var nmethods byte
+	if nmethods, err = socksReadByte(rw); err != nil {
 		return
 	}
-	req.Username = string(usernameBytes[:len(usernameBytes)-1])
 
-	req.Args, err = parseClientParameters(req.Username)
-	if err != nil {
+	// Read the methods.
+	var methods []byte
+	if methods, err = socksReadBytes(rw, int(nmethods)); err != nil {
 		return
 	}
 
-	var port int
-	var host string
+	// Pick the most "suitable" method.
+	method = socksAuthNoAcceptableMethods
+	for _, m := range methods {
+		switch m {
+		case socksAuthNoneRequired:
+			// Pick Username/Password over None if the client happens to
+			// send both.
+			if method == socksAuthNoAcceptableMethods {
+				method = m
+			}
+
+		case socksAuthUsernamePassword:
+			method = m
+		}
+	}
+
+	// Send the negotiated method.
+	var msg [2]byte
+	msg[0] = socksVersion
+	msg[1] = method
+	if _, err = rw.Writer.Write(msg[:]); err != nil {
+		return
+	}
+
+	if err = socksFlushBuffers(rw); err != nil {
+		return
+	}
+	return
+}
+
+// socksAuthenticate authenticates the client via the chosen authentication
+// mechanism.
+func socksAuthenticate(rw *bufio.ReadWriter, method byte, req *SocksRequest) (err error) {
+	switch method {
+	case socksAuthNoneRequired:
+		// Straight into reading the connect.
 
-	port = int(h[2])<<8 | int(h[3])<<0
-	if h[4] == 0 && h[5] == 0 && h[6] == 0 && h[7] != 0 {
-		var hostBytes []byte
-		hostBytes, err = r.ReadBytes('\x00')
-		if err != nil {
+	case socksAuthUsernamePassword:
+		if err = socksAuthRFC1929(rw, req); err != nil {
 			return
 		}
-		host = string(hostBytes[:len(hostBytes)-1])
+
+	case socksAuthNoAcceptableMethods:
+		err = fmt.Errorf("SOCKS method select had no compatible methods")
+		return
+
+	default:
+		err = fmt.Errorf("SOCKS method select picked a unsupported method 0x%02x", method)
+		return
+	}
+
+	if err = socksFlushBuffers(rw); err != nil {
+		return
+	}
+	return
+}
+
+// socksAuthRFC1929 authenticates the client via RFC 1929 username/password
+// auth.  As a design decision any valid username/password is accepted as this
+// field is primarily used as an out-of-band argument passing mechanism for
+// pluggable transports.
+func socksAuthRFC1929(rw *bufio.ReadWriter, req *SocksRequest) (err error) {
+	sendErrResp := func() {
+		// Swallow the write/flush error here, we are going to close the
+		// connection and the original failure is more useful.
+		resp := []byte{socksAuthRFC1929Ver, socksAuthRFC1929Fail}
+		rw.Write(resp[:])
+		socksFlushBuffers(rw)
+	}
+
+	// Validate the fixed parts of the command message.
+	if err = socksReadByteVerify(rw, "auth version", socksAuthRFC1929Ver); err != nil {
+		sendErrResp()
+		return
+	}
+
+	// Read the username.
+	var ulen byte
+	if ulen, err = socksReadByte(rw); err != nil {
+		return
+	}
+	if ulen < 1 {
+		sendErrResp()
+		err = fmt.Errorf("RFC1929 username with 0 length")
+		return
+	}
+	var uname []byte
+	if uname, err = socksReadBytes(rw, int(ulen)); err != nil {
+		return
+	}
+	req.Username = string(uname)
+
+	// Read the password.
+	var plen byte
+	if plen, err = socksReadByte(rw); err != nil {
+		return
+	}
+	if plen < 1 {
+		sendErrResp()
+		err = fmt.Errorf("RFC1929 password with 0 length")
+		return
+	}
+	var passwd []byte
+	if passwd, err = socksReadBytes(rw, int(plen)); err != nil {
+		return
+	}
+	if !(plen == 1 && passwd[0] == 0x00) {
+		// tor will set the password to 'NUL' if there are no arguments.
+		req.Password = string(passwd)
+	}
+
+	// Mash the username/password together and parse it as a pluggable
+	// transport argument string.
+	if req.Args, err = parseClientParameters(req.Username + req.Password); err != nil {
+		sendErrResp()
 	} else {
-		host = net.IPv4(h[4], h[5], h[6], h[7]).String()
+		resp := []byte{socksAuthRFC1929Ver, socksAuthRFC1929Success}
+		_, err = rw.Write(resp[:])
+	}
+	return
+}
+
+// socksReadCommand reads a SOCKS5 client command and parses out the relevant
+// fields into a SocksRequest.  Only CMD_CONNECT is supported.
+func socksReadCommand(rw *bufio.ReadWriter, req *SocksRequest) (err error) {
+	sendErrResp := func(reason byte) {
+		// Swallow errors that occur when writing/flushing the response,
+		// connection will be closed anyway.
+		sendSocks5ResponseRejected(rw, reason)
+		socksFlushBuffers(rw)
+	}
+
+	// Validate the fixed parts of the command message.
+	if err = socksReadByteVerify(rw, "version", socksVersion); err != nil {
+		sendErrResp(SocksRepGeneralFailure)
+		return
+	}
+	if err = socksReadByteVerify(rw, "command", socksCmdConnect); err != nil {
+		sendErrResp(SocksRepCommandNotSupported)
+		return
+	}
+	if err = socksReadByteVerify(rw, "reserved", socksRsv); err != nil {
+		sendErrResp(SocksRepGeneralFailure)
+		return
+	}
+
+	// Read the destination address/port.
+	// XXX: This should probably eventually send socks 5 error messages instead
+	// of rudely closing connections on invalid addresses.
+	var atype byte
+	if atype, err = socksReadByte(rw); err != nil {
+		return
+	}
+	var host string
+	switch atype {
+	case socksAtypeV4:
+		var addr []byte
+		if addr, err = socksReadBytes(rw, net.IPv4len); err != nil {
+			return
+		}
+		host = net.IPv4(addr[0], addr[1], addr[2], addr[3]).String()
+
+	case socksAtypeDomainName:
+		var alen byte
+		if alen, err = socksReadByte(rw); err != nil {
+			return
+		}
+		if alen == 0 {
+			err = fmt.Errorf("SOCKS request had domain name with 0 length")
+			return
+		}
+		var addr []byte
+		if addr, err = socksReadBytes(rw, int(alen)); err != nil {
+			return
+		}
+		host = string(addr)
+
+	case socksAtypeV6:
+		var rawAddr []byte
+		if rawAddr, err = socksReadBytes(rw, net.IPv6len); err != nil {
+			return
+		}
+		addr := make(net.IP, net.IPv6len)
+		copy(addr[:], rawAddr[:])
+		host = fmt.Sprintf("[%s]", addr.String())
+
+	default:
+		sendErrResp(SocksRepAddressNotSupported)
+		err = fmt.Errorf("SOCKS request had unsupported address type 0x%02x", atype)
+		return
 	}
+	var rawPort []byte
+	if rawPort, err = socksReadBytes(rw, 2); err != nil {
+		return
+	}
+	port := int(rawPort[0])<<8 | int(rawPort[1])<<0
 
-	if r.Buffered() != 0 {
-		err = fmt.Errorf("%d bytes left after SOCKS header", r.Buffered())
+	if err = socksFlushBuffers(rw); err != nil {
 		return
 	}
 
@@ -209,34 +441,64 @@ func readSocks4aConnect(s io.Reader) (req SocksRequest, err error) {
 	return
 }
 
-// Send a SOCKS4a response with the given code and address. If the IP field
-// inside addr is not an IPv4 address, the IP portion of the response will be
-// four zero bytes.
-func sendSocks4aResponse(w io.Writer, code byte, addr *net.TCPAddr) error {
-	var resp [8]byte
-	resp[0] = socksResponseVersion
+// Send a SOCKS5 response with the given code. BND.ADDR/BND.PORT is always the
+// IPv4 address/port "0.0.0.0:0".
+func sendSocks5Response(w io.Writer, code byte) error {
+	resp := make([]byte, 4+4+2)
+	resp[0] = socksVersion
 	resp[1] = code
-	resp[2] = byte((addr.Port >> 8) & 0xff)
-	resp[3] = byte((addr.Port >> 0) & 0xff)
-	ipv4 := addr.IP.To4()
-	if ipv4 != nil {
-		resp[4] = ipv4[0]
-		resp[5] = ipv4[1]
-		resp[6] = ipv4[2]
-		resp[7] = ipv4[3]
-	}
+	resp[2] = socksRsv
+	resp[3] = socksAtypeV4
+
+	// BND.ADDR/BND.PORT should be the address and port that the outgoing
+	// connection is bound to on the proxy, but Tor does not use this
+	// information, so all zeroes are sent.
+
 	_, err := w.Write(resp[:])
 	return err
 }
 
-var emptyAddr = net.TCPAddr{IP: net.IPv4(0, 0, 0, 0), Port: 0}
+// Send a SOCKS5 response code 0x00.
+func sendSocks5ResponseGranted(w io.Writer) error {
+	return sendSocks5Response(w, socksRepSucceeded)
+}
 
-// Send a SOCKS4a response code 0x5a.
-func sendSocks4aResponseGranted(w io.Writer, addr *net.TCPAddr) error {
-	return sendSocks4aResponse(w, socksRequestGranted, addr)
+// Send a SOCKS5 response with the provided failure reason.
+func sendSocks5ResponseRejected(w io.Writer, reason byte) error {
+	return sendSocks5Response(w, reason)
 }
 
-// Send a SOCKS4a response code 0x5b (with an all-zero address).
-func sendSocks4aResponseRejected(w io.Writer) error {
-	return sendSocks4aResponse(w, socksRequestRejected, &emptyAddr)
+func socksFlushBuffers(rw *bufio.ReadWriter) error {
+	if err := rw.Writer.Flush(); err != nil {
+		return err
+	}
+	if rw.Reader.Buffered() > 0 {
+		return fmt.Errorf("%d bytes left after SOCKS message", rw.Reader.Buffered())
+	}
+	return nil
+}
+
+func socksReadByte(rw *bufio.ReadWriter) (byte, error) {
+	return rw.Reader.ReadByte()
+}
+
+func socksReadBytes(rw *bufio.ReadWriter, n int) ([]byte, error) {
+	ret := make([]byte, n)
+	if _, err := io.ReadFull(rw.Reader, ret); err != nil {
+		return nil, err
+	}
+	return ret, nil
 }
+
+func socksReadByteVerify(rw *bufio.ReadWriter, descr string, expected byte) error {
+	val, err := socksReadByte(rw)
+	if err != nil {
+		return err
+	}
+	if val != expected {
+		return fmt.Errorf("SOCKS message field %s was 0x%02x, not 0x%02x", descr, val, expected)
+	}
+	return nil
+}
+
+var _ net.Listener = (*SocksListener)(nil)
diff --git a/socks_test.go b/socks_test.go
index 18d141a..aa27d4c 100644
--- a/socks_test.go
+++ b/socks_test.go
@@ -1,162 +1,368 @@
 package pt
 
 import (
+	"bufio"
 	"bytes"
+	"encoding/hex"
+	"io"
 	"net"
 	"testing"
 )
 
-func TestReadSocks4aConnect(t *testing.T) {
-	badTests := [...][]byte{
-		[]byte(""),
-		// missing userid
-		[]byte("\x04\x01\x12\x34\x01\x02\x03\x04"),
-		// missing \x00 after userid
-		[]byte("\x04\x01\x12\x34\x01\x02\x03\x04key=value"),
-		// missing hostname
-		[]byte("\x04\x01\x12\x34\x00\x00\x00\x01key=value\x00"),
-		// missing \x00 after hostname
-		[]byte("\x04\x01\x12\x34\x00\x00\x00\x01key=value\x00hostname"),
-		// bad name–value mapping
-		[]byte("\x04\x01\x12\x34\x00\x00\x00\x01userid\x00hostname\x00"),
-		// bad version number
-		[]byte("\x03\x01\x12\x34\x01\x02\x03\x04\x00"),
-		// BIND request
-		[]byte("\x04\x02\x12\x34\x01\x02\x03\x04\x00"),
-		// SOCKS5
-		[]byte("\x05\x01\x00"),
-	}
-	ipTests := [...]struct {
-		input  []byte
-		addr   net.TCPAddr
-		userid string
-	}{
-		{
-			[]byte("\x04\x01\x12\x34\x01\x02\x03\x04key=value\x00"),
-			net.TCPAddr{IP: net.ParseIP("1.2.3.4"), Port: 0x1234},
-			"key=value",
-		},
-		{
-			[]byte("\x04\x01\x12\x34\x01\x02\x03\x04\x00"),
-			net.TCPAddr{IP: net.ParseIP("1.2.3.4"), Port: 0x1234},
-			"",
-		},
-	}
-	hostnameTests := [...]struct {
-		input  []byte
-		target string
-		userid string
-	}{
-		{
-			[]byte("\x04\x01\x12\x34\x00\x00\x00\x01key=value\x00hostname\x00"),
-			"hostname:4660",
-			"key=value",
-		},
-		{
-			[]byte("\x04\x01\x12\x34\x00\x00\x00\x01\x00hostname\x00"),
-			"hostname:4660",
-			"",
-		},
-		{
-			[]byte("\x04\x01\x12\x34\x00\x00\x00\x01key=value\x00\x00"),
-			":4660",
-			"key=value",
-		},
-		{
-			[]byte("\x04\x01\x12\x34\x00\x00\x00\x01\x00\x00"),
-			":4660",
-			"",
-		},
-	}
-
-	for _, input := range badTests {
-		var buf bytes.Buffer
-		buf.Write(input)
-		_, err := readSocks4aConnect(&buf)
-		if err == nil {
-			t.Errorf("%q unexpectedly succeeded", input)
-		}
-	}
-
-	for _, test := range ipTests {
-		var buf bytes.Buffer
-		buf.Write(test.input)
-		req, err := readSocks4aConnect(&buf)
-		if err != nil {
-			t.Errorf("%q unexpectedly returned an error: %s", test.input, err)
-		}
-		addr, err := net.ResolveTCPAddr("tcp", req.Target)
-		if err != nil {
-			t.Errorf("%q → target %q: cannot resolve: %s", test.input,
-				req.Target, err)
-		}
-		if !tcpAddrsEqual(addr, &test.addr) {
-			t.Errorf("%q → address %s (expected %s)", test.input,
-				req.Target, test.addr.String())
-		}
-		if req.Username != test.userid {
-			t.Errorf("%q → username %q (expected %q)", test.input,
-				req.Username, test.userid)
-		}
-		if req.Args == nil {
-			t.Errorf("%q → unexpected nil Args from username %q", test.input, req.Username)
-		}
-	}
-
-	for _, test := range hostnameTests {
-		var buf bytes.Buffer
-		buf.Write(test.input)
-		req, err := readSocks4aConnect(&buf)
-		if err != nil {
-			t.Errorf("%q unexpectedly returned an error: %s", test.input, err)
-		}
-		if req.Target != test.target {
-			t.Errorf("%q → target %q (expected %q)", test.input,
-				req.Target, test.target)
-		}
-		if req.Username != test.userid {
-			t.Errorf("%q → username %q (expected %q)", test.input,
-				req.Username, test.userid)
-		}
-		if req.Args == nil {
-			t.Errorf("%q → unexpected nil Args from username %q", test.input, req.Username)
-		}
-	}
-}
-
-func TestSendSocks4aResponse(t *testing.T) {
-	tests := [...]struct {
-		code     byte
-		addr     net.TCPAddr
-		expected []byte
-	}{
-		{
-			socksRequestGranted,
-			net.TCPAddr{IP: net.ParseIP("1.2.3.4"), Port: 0x1234},
-			[]byte("\x00\x5a\x12\x34\x01\x02\x03\x04"),
-		},
-		{
-			socksRequestRejected,
-			net.TCPAddr{IP: net.ParseIP("1:2::3:4"), Port: 0x1234},
-			[]byte("\x00\x5b\x12\x34\x00\x00\x00\x00"),
-		},
-	}
-
-	for _, test := range tests {
-		var buf bytes.Buffer
-		err := sendSocks4aResponse(&buf, test.code, &test.addr)
-		if err != nil {
-			t.Errorf("0x%02x %s unexpectedly returned an error: %s", test.code, &test.addr, err)
-		}
-		p := make([]byte, 1024)
-		n, err := buf.Read(p)
-		if err != nil {
-			t.Fatal(err)
-		}
-		output := p[:n]
-		if !bytes.Equal(output, test.expected) {
-			t.Errorf("0x%02x %s → %v (expected %v)",
-				test.code, &test.addr, output, test.expected)
-		}
+// testReadWriter is a bytes.Buffer backed io.ReadWriter used for testing.  The
+// Read and Write routines are to be used by the component being tested.  Data
+// can be written to and read back via the writeHex and readHex routines.
+type testReadWriter struct {
+	readBuf  bytes.Buffer
+	writeBuf bytes.Buffer
+}
+
+func (c *testReadWriter) Read(buf []byte) (n int, err error) {
+	return c.readBuf.Read(buf)
+}
+
+func (c *testReadWriter) Write(buf []byte) (n int, err error) {
+	return c.writeBuf.Write(buf)
+}
+
+func (c *testReadWriter) writeHex(str string) (n int, err error) {
+	var buf []byte
+	if buf, err = hex.DecodeString(str); err != nil {
+		return
+	}
+	return c.readBuf.Write(buf)
+}
+
+func (c *testReadWriter) readHex() string {
+	return hex.EncodeToString(c.writeBuf.Bytes())
+}
+
+func (c *testReadWriter) toBufio() *bufio.ReadWriter {
+	return bufio.NewReadWriter(bufio.NewReader(c), bufio.NewWriter(c))
+}
+
+func (c *testReadWriter) reset() {
+	c.readBuf.Reset()
+	c.writeBuf.Reset()
+}
+
+// TestAuthInvalidVersion tests auth negotiation with an invalid version.
+func TestAuthInvalidVersion(t *testing.T) {
+	c := new(testReadWriter)
+
+	// VER = 03, NMETHODS = 01, METHODS = [00]
+	c.writeHex("030100")
+	if _, err := socksNegotiateAuth(c.toBufio()); err == nil {
+		t.Error("socksNegotiateAuth(InvalidVersion) succeded")
+	}
+}
+
+// TestAuthInvalidNMethods tests auth negotiaton with no methods.
+func TestAuthInvalidNMethods(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 00
+	c.writeHex("0500")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(No Methods) failed:", err)
+	}
+	if method != socksAuthNoAcceptableMethods {
+		t.Error("socksNegotiateAuth(No Methods) picked unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "05ff" {
+		t.Error("socksNegotiateAuth(No Methods) invalid response:", msg)
+	}
+}
+
+// TestAuthNoneRequired tests auth negotiaton with NO AUTHENTICATION REQUIRED.
+func TestAuthNoneRequired(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 01, METHODS = [00]
+	c.writeHex("050100")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(None) failed:", err)
+	}
+	if method != socksAuthNoneRequired {
+		t.Error("socksNegotiateAuth(None) unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "0500" {
+		t.Error("socksNegotiateAuth(None) invalid response:", msg)
+	}
+}
+
+// TestAuthUsernamePassword tests auth negotiation with USERNAME/PASSWORD.
+func TestAuthUsernamePassword(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 01, METHODS = [02]
+	c.writeHex("050102")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(UsernamePassword) failed:", err)
+	}
+	if method != socksAuthUsernamePassword {
+		t.Error("socksNegotiateAuth(UsernamePassword) unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "0502" {
+		t.Error("socksNegotiateAuth(UsernamePassword) invalid response:", msg)
 	}
 }
+
+// TestAuthBoth tests auth negotiation containing both NO AUTHENTICATION
+// REQUIRED and USERNAME/PASSWORD.
+func TestAuthBoth(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 02, METHODS = [00, 02]
+	c.writeHex("05020002")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(Both) failed:", err)
+	}
+	if method != socksAuthUsernamePassword {
+		t.Error("socksNegotiateAuth(Both) unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "0502" {
+		t.Error("socksNegotiateAuth(Both) invalid response:", msg)
+	}
+}
+
+// TestAuthUnsupported tests auth negotiation with a unsupported method.
+func TestAuthUnsupported(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 01, METHODS = [01] (GSSAPI)
+	c.writeHex("050101")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(Unknown) failed:", err)
+	}
+	if method != socksAuthNoAcceptableMethods {
+		t.Error("socksNegotiateAuth(Unknown) picked unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "05ff" {
+		t.Error("socksNegotiateAuth(Unknown) invalid response:", msg)
+	}
+}
+
+// TestAuthUnsupported2 tests auth negotiation with supported and unsupported
+// methods.
+func TestAuthUnsupported2(t *testing.T) {
+	c := new(testReadWriter)
+	var err error
+	var method byte
+
+	// VER = 05, NMETHODS = 03, METHODS = [00,01,02]
+	c.writeHex("0503000102")
+	if method, err = socksNegotiateAuth(c.toBufio()); err != nil {
+		t.Error("socksNegotiateAuth(Unknown2) failed:", err)
+	}
+	if method != socksAuthUsernamePassword {
+		t.Error("socksNegotiateAuth(Unknown2) picked unexpected method:", method)
+	}
+	if msg := c.readHex(); msg != "0502" {
+		t.Error("socksNegotiateAuth(Unknown2) invalid response:", msg)
+	}
+}
+
+// TestRFC1929InvalidVersion tests RFC1929 auth with an invalid version.
+func TestRFC1929InvalidVersion(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 03, ULEN = 5, UNAME = "ABCDE", PLEN = 5, PASSWD = "abcde"
+	c.writeHex("03054142434445056162636465")
+	if err := socksAuthenticate(c.toBufio(), socksAuthUsernamePassword, &req); err == nil {
+		t.Error("socksAuthenticate(InvalidVersion) succeded")
+	}
+	if msg := c.readHex(); msg != "0101" {
+		t.Error("socksAuthenticate(InvalidVersion) invalid response:", msg)
+	}
+}
+
+// TestRFC1929InvalidUlen tests RFC1929 auth with an invalid ULEN.
+func TestRFC1929InvalidUlen(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 01, ULEN = 0, UNAME = "", PLEN = 5, PASSWD = "abcde"
+	c.writeHex("0100056162636465")
+	if err := socksAuthenticate(c.toBufio(), socksAuthUsernamePassword, &req); err == nil {
+		t.Error("socksAuthenticate(InvalidUlen) succeded")
+	}
+	if msg := c.readHex(); msg != "0101" {
+		t.Error("socksAuthenticate(InvalidUlen) invalid response:", msg)
+	}
+}
+
+// TestRFC1929InvalidPlen tests RFC1929 auth with an invalid PLEN.
+func TestRFC1929InvalidPlen(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 01, ULEN = 5, UNAME = "ABCDE", PLEN = 0, PASSWD = ""
+	c.writeHex("0105414243444500")
+	if err := socksAuthenticate(c.toBufio(), socksAuthUsernamePassword, &req); err == nil {
+		t.Error("socksAuthenticate(InvalidPlen) succeded")
+	}
+	if msg := c.readHex(); msg != "0101" {
+		t.Error("socksAuthenticate(InvalidPlen) invalid response:", msg)
+	}
+}
+
+// TestRFC1929InvalidArgs tests RFC1929 auth with invalid pt args.
+func TestRFC1929InvalidPTArgs(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 01, ULEN = 5, UNAME = "ABCDE", PLEN = 5, PASSWD = "abcde"
+	c.writeHex("01054142434445056162636465")
+	if err := socksAuthenticate(c.toBufio(), socksAuthUsernamePassword, &req); err == nil {
+		t.Error("socksAuthenticate(InvalidArgs) succeded")
+	}
+	if msg := c.readHex(); msg != "0101" {
+		t.Error("socksAuthenticate(InvalidArgs) invalid response:", msg)
+	}
+}
+
+// TestRFC1929Success tests RFC1929 auth with valid pt args.
+func TestRFC1929Success(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 01, ULEN = 9, UNAME = "key=value", PLEN = 1, PASSWD = "\0"
+	c.writeHex("01096b65793d76616c75650100")
+	if err := socksAuthenticate(c.toBufio(), socksAuthUsernamePassword, &req); err != nil {
+		t.Error("socksAuthenticate(Success) failed:", err)
+	}
+	if msg := c.readHex(); msg != "0100" {
+		t.Error("socksAuthenticate(Success) invalid response:", msg)
+	}
+	v, ok := req.Args.Get("key")
+	if v != "value" || !ok {
+		t.Error("RFC1929 k,v parse failure:", v)
+	}
+}
+
+// TestRequestInvalidHdr tests SOCKS5 requests with invalid VER/CMD/RSV/ATYPE
+func TestRequestInvalidHdr(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 03, CMD = 01, RSV = 00, ATYPE = 01, DST.ADDR = 127.0.0.1, DST.PORT = 9050
+	c.writeHex("030100017f000001235a")
+	if err := socksReadCommand(c.toBufio(), &req); err == nil {
+		t.Error("socksReadCommand(InvalidVer) succeded")
+	}
+	if msg := c.readHex(); msg != "05010001000000000000" {
+		t.Error("socksReadCommand(InvalidVer) invalid response:", msg)
+	}
+	c.reset()
+
+	// VER = 05, CMD = 05, RSV = 00, ATYPE = 01, DST.ADDR = 127.0.0.1, DST.PORT = 9050
+	c.writeHex("050500017f000001235a")
+	if err := socksReadCommand(c.toBufio(), &req); err == nil {
+		t.Error("socksReadCommand(InvalidCmd) succeded")
+	}
+	if msg := c.readHex(); msg != "05070001000000000000" {
+		t.Error("socksReadCommand(InvalidCmd) invalid response:", msg)
+	}
+	c.reset()
+
+	// VER = 05, CMD = 01, RSV = 30, ATYPE = 01, DST.ADDR = 127.0.0.1, DST.PORT = 9050
+	c.writeHex("050130017f000001235a")
+	if err := socksReadCommand(c.toBufio(), &req); err == nil {
+		t.Error("socksReadCommand(InvalidRsv) succeded")
+	}
+	if msg := c.readHex(); msg != "05010001000000000000" {
+		t.Error("socksReadCommand(InvalidRsv) invalid response:", msg)
+	}
+	c.reset()
+
+	// VER = 05, CMD = 01, RSV = 01, ATYPE = 05, DST.ADDR = 127.0.0.1, DST.PORT = 9050
+	c.writeHex("050100057f000001235a")
+	if err := socksReadCommand(c.toBufio(), &req); err == nil {
+		t.Error("socksReadCommand(InvalidAtype) succeded")
+	}
+	if msg := c.readHex(); msg != "05080001000000000000" {
+		t.Error("socksAuthenticate(InvalidAtype) invalid response:", msg)
+	}
+	c.reset()
+}
+
+// TestRequestIPv4 tests IPv4 SOCKS5 requests.
+func TestRequestIPv4(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 05, CMD = 01, RSV = 00, ATYPE = 01, DST.ADDR = 127.0.0.1, DST.PORT = 9050
+	c.writeHex("050100017f000001235a")
+	if err := socksReadCommand(c.toBufio(), &req); err != nil {
+		t.Error("socksReadCommand(IPv4) failed:", err)
+	}
+	addr, err := net.ResolveTCPAddr("tcp", req.Target)
+	if err != nil {
+		t.Error("net.ResolveTCPAddr failed:", err)
+	}
+	if !tcpAddrsEqual(addr, &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 9050}) {
+		t.Error("Unexpected target:", addr)
+	}
+}
+
+// TestRequestIPv6 tests IPv4 SOCKS5 requests.
+func TestRequestIPv6(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 05, CMD = 01, RSV = 00, ATYPE = 04, DST.ADDR = 0102:0304:0506:0708:090a:0b0c:0d0e:0f10, DST.PORT = 9050
+	c.writeHex("050100040102030405060708090a0b0c0d0e0f10235a")
+	if err := socksReadCommand(c.toBufio(), &req); err != nil {
+		t.Error("socksReadCommand(IPv6) failed:", err)
+	}
+	addr, err := net.ResolveTCPAddr("tcp", req.Target)
+	if err != nil {
+		t.Error("net.ResolveTCPAddr failed:", err)
+	}
+	if !tcpAddrsEqual(addr, &net.TCPAddr{IP: net.ParseIP("0102:0304:0506:0708:090a:0b0c:0d0e:0f10"), Port: 9050}) {
+		t.Error("Unexpected target:", addr)
+	}
+}
+
+// TestRequestFQDN tests FQDN (DOMAINNAME) SOCKS5 requests.
+func TestRequestFQDN(t *testing.T) {
+	c := new(testReadWriter)
+	var req SocksRequest
+
+	// VER = 05, CMD = 01, RSV = 00, ATYPE = 04, DST.ADDR = example.com, DST.PORT = 9050
+	c.writeHex("050100030b6578616d706c652e636f6d235a")
+	if err := socksReadCommand(c.toBufio(), &req); err != nil {
+		t.Error("socksReadCommand(FQDN) failed:", err)
+	}
+	if req.Target != "example.com:9050" {
+		t.Error("Unexpected target:", req.Target)
+	}
+}
+
+// TestResponseNil tests nil address SOCKS5 responses.
+func TestResponseNil(t *testing.T) {
+	c := new(testReadWriter)
+
+	b := c.toBufio()
+	if err := sendSocks5ResponseGranted(b); err != nil {
+		t.Error("sendSocks5ResponseGranted() failed:", err)
+	}
+	b.Flush()
+	if msg := c.readHex(); msg != "05000001000000000000" {
+		t.Error("sendSocks5ResponseGranted(nil) invalid response:", msg)
+	}
+}
+
+var _ io.ReadWriter = (*testReadWriter)(nil)





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