支持socks5代理

go.mod

@@ -6,7 +6,6 @@ require gogo v0.0.0
 
 require (
 	github.com/andybalholm/brotli v1.0.4 // indirect
-	github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5 // indirect
 	github.com/bmizerany/pq v0.0.0-20131128184720-da2b95e392c1 // indirect
 	github.com/deckarep/golang-set/v2 v2.6.0 // indirect
 	github.com/gaukas/godicttls v0.0.3 // indirect

go.sum

@@ -1,7 +1,5 @@
 github.com/andybalholm/brotli v1.0.4 h1:V7DdXeJtZscaqfNuAdSRuRFzuiKlHSC/Zh3zl9qY3JY=
 github.com/andybalholm/brotli v1.0.4/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
-github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5 h1:0CwZNZbxp69SHPdPJAN/hZIm0C4OItdklCFmMRWYpio=
-github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5/go.mod h1:wHh0iHkYZB8zMSxRWpUBQtwG5a7fFgvEO+odwuTv2gs=
 github.com/bmizerany/pq v0.0.0-20131128184720-da2b95e392c1 h1:1clOQIolnXGoH1SUo8ZPgdfOWFp/6i8NuRerrVL/TAc=
 github.com/bmizerany/pq v0.0.0-20131128184720-da2b95e392c1/go.mod h1:YR6v6TjYGQnPky7rSf5U+AiQ4+EHIVmFYbhHUPo5L2U=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=

proxy/socks5.go

@@ -3,7 +3,7 @@ package proxy
 import (
 	"log"
 
-	"github.com/armon/go-socks5"
+	"goodlink/socks5"
 )
 
 func ListenSocks5(addr string) {

socks5/.gitignore

@@ -0,0 +1,22 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe

socks5/auth.go

@@ -0,0 +1,151 @@
+package socks5
+
+import (
+	"fmt"
+	"io"
+)
+
+const (
+	NoAuth          = uint8(0)
+	noAcceptable    = uint8(255)
+	UserPassAuth    = uint8(2)
+	userAuthVersion = uint8(1)
+	authSuccess     = uint8(0)
+	authFailure     = uint8(1)
+)
+
+var (
+	UserAuthFailed  = fmt.Errorf("User authentication failed")
+	NoSupportedAuth = fmt.Errorf("No supported authentication mechanism")
+)
+
+// A Request encapsulates authentication state provided
+// during negotiation
+type AuthContext struct {
+	// Provided auth method
+	Method uint8
+	// Payload provided during negotiation.
+	// Keys depend on the used auth method.
+	// For UserPassauth contains Username
+	Payload map[string]string
+}
+
+type Authenticator interface {
+	Authenticate(reader io.Reader, writer io.Writer) (*AuthContext, error)
+	GetCode() uint8
+}
+
+// NoAuthAuthenticator is used to handle the "No Authentication" mode
+type NoAuthAuthenticator struct{}
+
+func (a NoAuthAuthenticator) GetCode() uint8 {
+	return NoAuth
+}
+
+func (a NoAuthAuthenticator) Authenticate(reader io.Reader, writer io.Writer) (*AuthContext, error) {
+	_, err := writer.Write([]byte{socks5Version, NoAuth})
+	return &AuthContext{NoAuth, nil}, err
+}
+
+// UserPassAuthenticator is used to handle username/password based
+// authentication
+type UserPassAuthenticator struct {
+	Credentials CredentialStore
+}
+
+func (a UserPassAuthenticator) GetCode() uint8 {
+	return UserPassAuth
+}
+
+func (a UserPassAuthenticator) Authenticate(reader io.Reader, writer io.Writer) (*AuthContext, error) {
+	// Tell the client to use user/pass auth
+	if _, err := writer.Write([]byte{socks5Version, UserPassAuth}); err != nil {
+		return nil, err
+	}
+
+	// Get the version and username length
+	header := []byte{0, 0}
+	if _, err := io.ReadAtLeast(reader, header, 2); err != nil {
+		return nil, err
+	}
+
+	// Ensure we are compatible
+	if header[0] != userAuthVersion {
+		return nil, fmt.Errorf("Unsupported auth version: %v", header[0])
+	}
+
+	// Get the user name
+	userLen := int(header[1])
+	user := make([]byte, userLen)
+	if _, err := io.ReadAtLeast(reader, user, userLen); err != nil {
+		return nil, err
+	}
+
+	// Get the password length
+	if _, err := reader.Read(header[:1]); err != nil {
+		return nil, err
+	}
+
+	// Get the password
+	passLen := int(header[0])
+	pass := make([]byte, passLen)
+	if _, err := io.ReadAtLeast(reader, pass, passLen); err != nil {
+		return nil, err
+	}
+
+	// Verify the password
+	if a.Credentials.Valid(string(user), string(pass)) {
+		if _, err := writer.Write([]byte{userAuthVersion, authSuccess}); err != nil {
+			return nil, err
+		}
+	} else {
+		if _, err := writer.Write([]byte{userAuthVersion, authFailure}); err != nil {
+			return nil, err
+		}
+		return nil, UserAuthFailed
+	}
+
+	// Done
+	return &AuthContext{UserPassAuth, map[string]string{"Username": string(user)}}, nil
+}
+
+// authenticate is used to handle connection authentication
+func (s *Server) authenticate(conn io.Writer, bufConn io.Reader) (*AuthContext, error) {
+	// Get the methods
+	methods, err := readMethods(bufConn)
+	if err != nil {
+		return nil, fmt.Errorf("Failed to get auth methods: %v", err)
+	}
+
+	// Select a usable method
+	for _, method := range methods {
+		cator, found := s.authMethods[method]
+		if found {
+			return cator.Authenticate(bufConn, conn)
+		}
+	}
+
+	// No usable method found
+	return nil, noAcceptableAuth(conn)
+}
+
+// noAcceptableAuth is used to handle when we have no eligible
+// authentication mechanism
+func noAcceptableAuth(conn io.Writer) error {
+	conn.Write([]byte{socks5Version, noAcceptable})
+	return NoSupportedAuth
+}
+
+// readMethods is used to read the number of methods
+// and proceeding auth methods
+func readMethods(r io.Reader) ([]byte, error) {
+	header := []byte{0}
+	if _, err := r.Read(header); err != nil {
+		return nil, err
+	}
+
+	numMethods := int(header[0])
+	methods := make([]byte, numMethods)
+	_, err := io.ReadAtLeast(r, methods, numMethods)
+	return methods, err
+}

socks5/auth_test.go

@@ -0,0 +1,119 @@
+package socks5
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestNoAuth(t *testing.T) {
+	req := bytes.NewBuffer(nil)
+	req.Write([]byte{1, NoAuth})
+	var resp bytes.Buffer
+
+	s, _ := New(&Config{})
+	ctx, err := s.authenticate(&resp, req)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if ctx.Method != NoAuth {
+		t.Fatal("Invalid Context Method")
+	}
+
+	out := resp.Bytes()
+	if !bytes.Equal(out, []byte{socks5Version, NoAuth}) {
+		t.Fatalf("bad: %v", out)
+	}
+}
+
+func TestPasswordAuth_Valid(t *testing.T) {
+	req := bytes.NewBuffer(nil)
+	req.Write([]byte{2, NoAuth, UserPassAuth})
+	req.Write([]byte{1, 3, 'f', 'o', 'o', 3, 'b', 'a', 'r'})
+	var resp bytes.Buffer
+
+	cred := StaticCredentials{
+		"foo": "bar",
+	}
+
+	cator := UserPassAuthenticator{Credentials: cred}
+
+	s, _ := New(&Config{AuthMethods: []Authenticator{cator}})
+
+	ctx, err := s.authenticate(&resp, req)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if ctx.Method != UserPassAuth {
+		t.Fatal("Invalid Context Method")
+	}
+
+	val, ok := ctx.Payload["Username"]
+	if !ok {
+		t.Fatal("Missing key Username in auth context's payload")
+	}
+
+	if val != "foo" {
+		t.Fatal("Invalid Username in auth context's payload")
+	}
+
+	out := resp.Bytes()
+	if !bytes.Equal(out, []byte{socks5Version, UserPassAuth, 1, authSuccess}) {
+		t.Fatalf("bad: %v", out)
+	}
+}
+
+func TestPasswordAuth_Invalid(t *testing.T) {
+	req := bytes.NewBuffer(nil)
+	req.Write([]byte{2, NoAuth, UserPassAuth})
+	req.Write([]byte{1, 3, 'f', 'o', 'o', 3, 'b', 'a', 'z'})
+	var resp bytes.Buffer
+
+	cred := StaticCredentials{
+		"foo": "bar",
+	}
+	cator := UserPassAuthenticator{Credentials: cred}
+	s, _ := New(&Config{AuthMethods: []Authenticator{cator}})
+
+	ctx, err := s.authenticate(&resp, req)
+	if err != UserAuthFailed {
+		t.Fatalf("err: %v", err)
+	}
+
+	if ctx != nil {
+		t.Fatal("Invalid Context Method")
+	}
+
+	out := resp.Bytes()
+	if !bytes.Equal(out, []byte{socks5Version, UserPassAuth, 1, authFailure}) {
+		t.Fatalf("bad: %v", out)
+	}
+}
+
+func TestNoSupportedAuth(t *testing.T) {
+	req := bytes.NewBuffer(nil)
+	req.Write([]byte{1, NoAuth})
+	var resp bytes.Buffer
+
+	cred := StaticCredentials{
+		"foo": "bar",
+	}
+	cator := UserPassAuthenticator{Credentials: cred}
+
+	s, _ := New(&Config{AuthMethods: []Authenticator{cator}})
+
+	ctx, err := s.authenticate(&resp, req)
+	if err != NoSupportedAuth {
+		t.Fatalf("err: %v", err)
+	}
+
+	if ctx != nil {
+		t.Fatal("Invalid Context Method")
+	}
+
+	out := resp.Bytes()
+	if !bytes.Equal(out, []byte{socks5Version, noAcceptable}) {
+		t.Fatalf("bad: %v", out)
+	}
+}

socks5/credentials.go

@@ -0,0 +1,17 @@
+package socks5
+
+// CredentialStore is used to support user/pass authentication
+type CredentialStore interface {
+	Valid(user, password string) bool
+}
+
+// StaticCredentials enables using a map directly as a credential store
+type StaticCredentials map[string]string
+
+func (s StaticCredentials) Valid(user, password string) bool {
+	pass, ok := s[user]
+	if !ok {
+		return false
+	}
+	return password == pass
+}

socks5/credentials_test.go

@@ -0,0 +1,24 @@
+package socks5
+
+import (
+	"testing"
+)
+
+func TestStaticCredentials(t *testing.T) {
+	creds := StaticCredentials{
+		"foo": "bar",
+		"baz": "",
+	}
+
+	if !creds.Valid("foo", "bar") {
+		t.Fatalf("expect valid")
+	}
+
+	if !creds.Valid("baz", "") {
+		t.Fatalf("expect valid")
+	}
+
+	if creds.Valid("foo", "") {
+		t.Fatalf("expect invalid")
+	}
+}

socks5/request.go

@@ -0,0 +1,364 @@
+package socks5
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+
+	"golang.org/x/net/context"
+)
+
+const (
+	ConnectCommand   = uint8(1)
+	BindCommand      = uint8(2)
+	AssociateCommand = uint8(3)
+	ipv4Address      = uint8(1)
+	fqdnAddress      = uint8(3)
+	ipv6Address      = uint8(4)
+)
+
+const (
+	successReply uint8 = iota
+	serverFailure
+	ruleFailure
+	networkUnreachable
+	hostUnreachable
+	connectionRefused
+	ttlExpired
+	commandNotSupported
+	addrTypeNotSupported
+)
+
+var (
+	unrecognizedAddrType = fmt.Errorf("Unrecognized address type")
+)
+
+// AddressRewriter is used to rewrite a destination transparently
+type AddressRewriter interface {
+	Rewrite(ctx context.Context, request *Request) (context.Context, *AddrSpec)
+}
+
+// AddrSpec is used to return the target AddrSpec
+// which may be specified as IPv4, IPv6, or a FQDN
+type AddrSpec struct {
+	FQDN string
+	IP   net.IP
+	Port int
+}
+
+func (a *AddrSpec) String() string {
+	if a.FQDN != "" {
+		return fmt.Sprintf("%s (%s):%d", a.FQDN, a.IP, a.Port)
+	}
+	return fmt.Sprintf("%s:%d", a.IP, a.Port)
+}
+
+// Address returns a string suitable to dial; prefer returning IP-based
+// address, fallback to FQDN
+func (a AddrSpec) Address() string {
+	if 0 != len(a.IP) {
+		return net.JoinHostPort(a.IP.String(), strconv.Itoa(a.Port))
+	}
+	return net.JoinHostPort(a.FQDN, strconv.Itoa(a.Port))
+}
+
+// A Request represents request received by a server
+type Request struct {
+	// Protocol version
+	Version uint8
+	// Requested command
+	Command uint8
+	// AuthContext provided during negotiation
+	AuthContext *AuthContext
+	// AddrSpec of the the network that sent the request
+	RemoteAddr *AddrSpec
+	// AddrSpec of the desired destination
+	DestAddr *AddrSpec
+	// AddrSpec of the actual destination (might be affected by rewrite)
+	realDestAddr *AddrSpec
+	bufConn      io.Reader
+}
+
+type conn interface {
+	Write([]byte) (int, error)
+	RemoteAddr() net.Addr
+}
+
+// NewRequest creates a new Request from the tcp connection
+func NewRequest(bufConn io.Reader) (*Request, error) {
+	// Read the version byte
+	header := []byte{0, 0, 0}
+	if _, err := io.ReadAtLeast(bufConn, header, 3); err != nil {
+		return nil, fmt.Errorf("Failed to get command version: %v", err)
+	}
+
+	// Ensure we are compatible
+	if header[0] != socks5Version {
+		return nil, fmt.Errorf("Unsupported command version: %v", header[0])
+	}
+
+	// Read in the destination address
+	dest, err := readAddrSpec(bufConn)
+	if err != nil {
+		return nil, err
+	}
+
+	request := &Request{
+		Version:  socks5Version,
+		Command:  header[1],
+		DestAddr: dest,
+		bufConn:  bufConn,
+	}
+
+	return request, nil
+}
+
+// handleRequest is used for request processing after authentication
+func (s *Server) handleRequest(req *Request, conn conn) error {
+	ctx := context.Background()
+
+	// Resolve the address if we have a FQDN
+	dest := req.DestAddr
+	if dest.FQDN != "" {
+		ctx_, addr, err := s.config.Resolver.Resolve(ctx, dest.FQDN)
+		if err != nil {
+			if err := sendReply(conn, hostUnreachable, nil); err != nil {
+				return fmt.Errorf("Failed to send reply: %v", err)
+			}
+			return fmt.Errorf("Failed to resolve destination '%v': %v", dest.FQDN, err)
+		}
+		ctx = ctx_
+		dest.IP = addr
+	}
+
+	// Apply any address rewrites
+	req.realDestAddr = req.DestAddr
+	if s.config.Rewriter != nil {
+		ctx, req.realDestAddr = s.config.Rewriter.Rewrite(ctx, req)
+	}
+
+	// Switch on the command
+	switch req.Command {
+	case ConnectCommand:
+		return s.handleConnect(ctx, conn, req)
+	case BindCommand:
+		return s.handleBind(ctx, conn, req)
+	case AssociateCommand:
+		return s.handleAssociate(ctx, conn, req)
+	default:
+		if err := sendReply(conn, commandNotSupported, nil); err != nil {
+			return fmt.Errorf("Failed to send reply: %v", err)
+		}
+		return fmt.Errorf("Unsupported command: %v", req.Command)
+	}
+}
+
+// handleConnect is used to handle a connect command
+func (s *Server) handleConnect(ctx context.Context, conn conn, req *Request) error {
+	// Check if this is allowed
+	if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
+		if err := sendReply(conn, ruleFailure, nil); err != nil {
+			return fmt.Errorf("Failed to send reply: %v", err)
+		}
+		return fmt.Errorf("Connect to %v blocked by rules", req.DestAddr)
+	} else {
+		ctx = ctx_
+	}
+
+	// Attempt to connect
+	dial := s.config.Dial
+	if dial == nil {
+		dial = func(ctx context.Context, net_, addr string) (net.Conn, error) {
+			return net.Dial(net_, addr)
+		}
+	}
+	target, err := dial(ctx, "tcp", req.realDestAddr.Address())
+	if err != nil {
+		msg := err.Error()
+		resp := hostUnreachable
+		if strings.Contains(msg, "refused") {
+			resp = connectionRefused
+		} else if strings.Contains(msg, "network is unreachable") {
+			resp = networkUnreachable
+		}
+		if err := sendReply(conn, resp, nil); err != nil {
+			return fmt.Errorf("Failed to send reply: %v", err)
+		}
+		return fmt.Errorf("Connect to %v failed: %v", req.DestAddr, err)
+	}
+	defer target.Close()
+
+	// Send success
+	local := target.LocalAddr().(*net.TCPAddr)
+	bind := AddrSpec{IP: local.IP, Port: local.Port}
+	if err := sendReply(conn, successReply, &bind); err != nil {
+		return fmt.Errorf("Failed to send reply: %v", err)
+	}
+
+	// Start proxying
+	errCh := make(chan error, 2)
+	go proxy(target, req.bufConn, errCh)
+	go proxy(conn, target, errCh)
+
+	// Wait
+	for i := 0; i < 2; i++ {
+		e := <-errCh
+		if e != nil {
+			// return from this function closes target (and conn).
+			return e
+		}
+	}
+	return nil
+}
+
+// handleBind is used to handle a connect command
+func (s *Server) handleBind(ctx context.Context, conn conn, req *Request) error {
+	// Check if this is allowed
+	if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
+		if err := sendReply(conn, ruleFailure, nil); err != nil {
+			return fmt.Errorf("Failed to send reply: %v", err)
+		}
+		return fmt.Errorf("Bind to %v blocked by rules", req.DestAddr)
+	} else {
+		ctx = ctx_
+	}
+
+	// TODO: Support bind
+	if err := sendReply(conn, commandNotSupported, nil); err != nil {
+		return fmt.Errorf("Failed to send reply: %v", err)
+	}
+	return nil
+}
+
+// handleAssociate is used to handle a connect command
+func (s *Server) handleAssociate(ctx context.Context, conn conn, req *Request) error {
+	// Check if this is allowed
+	if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
+		if err := sendReply(conn, ruleFailure, nil); err != nil {
+			return fmt.Errorf("Failed to send reply: %v", err)
+		}
+		return fmt.Errorf("Associate to %v blocked by rules", req.DestAddr)
+	} else {
+		ctx = ctx_
+	}
+
+	// TODO: Support associate
+	if err := sendReply(conn, commandNotSupported, nil); err != nil {
+		return fmt.Errorf("Failed to send reply: %v", err)
+	}
+	return nil
+}
+
+// readAddrSpec is used to read AddrSpec.
+// Expects an address type byte, follwed by the address and port
+func readAddrSpec(r io.Reader) (*AddrSpec, error) {
+	d := &AddrSpec{}
+
+	// Get the address type
+	addrType := []byte{0}
+	if _, err := r.Read(addrType); err != nil {
+		return nil, err
+	}
+
+	// Handle on a per type basis
+	switch addrType[0] {
+	case ipv4Address:
+		addr := make([]byte, 4)
+		if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
+			return nil, err
+		}
+		d.IP = net.IP(addr)
+
+	case ipv6Address:
+		addr := make([]byte, 16)
+		if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
+			return nil, err
+		}
+		d.IP = net.IP(addr)
+
+	case fqdnAddress:
+		if _, err := r.Read(addrType); err != nil {
+			return nil, err
+		}
+		addrLen := int(addrType[0])
+		fqdn := make([]byte, addrLen)
+		if _, err := io.ReadAtLeast(r, fqdn, addrLen); err != nil {
+			return nil, err
+		}
+		d.FQDN = string(fqdn)
+
+	default:
+		return nil, unrecognizedAddrType
+	}
+
+	// Read the port
+	port := []byte{0, 0}
+	if _, err := io.ReadAtLeast(r, port, 2); err != nil {
+		return nil, err
+	}
+	d.Port = (int(port[0]) << 8) | int(port[1])
+
+	return d, nil
+}
+
+// sendReply is used to send a reply message
+func sendReply(w io.Writer, resp uint8, addr *AddrSpec) error {
+	// Format the address
+	var addrType uint8
+	var addrBody []byte
+	var addrPort uint16
+	switch {
+	case addr == nil:
+		addrType = ipv4Address
+		addrBody = []byte{0, 0, 0, 0}
+		addrPort = 0
+
+	case addr.FQDN != "":
+		addrType = fqdnAddress
+		addrBody = append([]byte{byte(len(addr.FQDN))}, addr.FQDN...)
+		addrPort = uint16(addr.Port)
+
+	case addr.IP.To4() != nil:
+		addrType = ipv4Address
+		addrBody = []byte(addr.IP.To4())
+		addrPort = uint16(addr.Port)
+
+	case addr.IP.To16() != nil:
+		addrType = ipv6Address
+		addrBody = []byte(addr.IP.To16())
+		addrPort = uint16(addr.Port)
+
+	default:
+		return fmt.Errorf("Failed to format address: %v", addr)
+	}
+
+	// Format the message
+	msg := make([]byte, 6+len(addrBody))
+	msg[0] = socks5Version
+	msg[1] = resp
+	msg[2] = 0 // Reserved
+	msg[3] = addrType
+	copy(msg[4:], addrBody)
+	msg[4+len(addrBody)] = byte(addrPort >> 8)
+	msg[4+len(addrBody)+1] = byte(addrPort & 0xff)
+
+	// Send the message
+	_, err := w.Write(msg)
+	return err
+}
+
+type closeWriter interface {
+	CloseWrite() error
+}
+
+// proxy is used to suffle data from src to destination, and sends errors
+// down a dedicated channel
+func proxy(dst io.Writer, src io.Reader, errCh chan error) {
+	_, err := io.Copy(dst, src)
+	if tcpConn, ok := dst.(closeWriter); ok {
+		tcpConn.CloseWrite()
+	}
+	errCh <- err
+}

socks5/request_test.go

@@ -0,0 +1,169 @@
+package socks5
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"log"
+	"net"
+	"os"
+	"strings"
+	"testing"
+)
+
+type MockConn struct {
+	buf bytes.Buffer
+}
+
+func (m *MockConn) Write(b []byte) (int, error) {
+	return m.buf.Write(b)
+}
+
+func (m *MockConn) RemoteAddr() net.Addr {
+	return &net.TCPAddr{IP: []byte{127, 0, 0, 1}, Port: 65432}
+}
+
+func TestRequest_Connect(t *testing.T) {
+	// Create a local listener
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	go func() {
+		conn, err := l.Accept()
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		defer conn.Close()
+
+		buf := make([]byte, 4)
+		if _, err := io.ReadAtLeast(conn, buf, 4); err != nil {
+			t.Fatalf("err: %v", err)
+		}
+
+		if !bytes.Equal(buf, []byte("ping")) {
+			t.Fatalf("bad: %v", buf)
+		}
+		conn.Write([]byte("pong"))
+	}()
+	lAddr := l.Addr().(*net.TCPAddr)
+
+	// Make server
+	s := &Server{config: &Config{
+		Rules:    PermitAll(),
+		Resolver: DNSResolver{},
+		Logger:   log.New(os.Stdout, "", log.LstdFlags),
+	}}
+
+	// Create the connect request
+	buf := bytes.NewBuffer(nil)
+	buf.Write([]byte{5, 1, 0, 1, 127, 0, 0, 1})
+
+	port := []byte{0, 0}
+	binary.BigEndian.PutUint16(port, uint16(lAddr.Port))
+	buf.Write(port)
+
+	// Send a ping
+	buf.Write([]byte("ping"))
+
+	// Handle the request
+	resp := &MockConn{}
+	req, err := NewRequest(buf)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if err := s.handleRequest(req, resp); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Verify response
+	out := resp.buf.Bytes()
+	expected := []byte{
+		5,
+		0,
+		0,
+		1,
+		127, 0, 0, 1,
+		0, 0,
+		'p', 'o', 'n', 'g',
+	}
+
+	// Ignore the port for both
+	out[8] = 0
+	out[9] = 0
+
+	if !bytes.Equal(out, expected) {
+		t.Fatalf("bad: %v %v", out, expected)
+	}
+}
+
+func TestRequest_Connect_RuleFail(t *testing.T) {
+	// Create a local listener
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	go func() {
+		conn, err := l.Accept()
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		defer conn.Close()
+
+		buf := make([]byte, 4)
+		if _, err := io.ReadAtLeast(conn, buf, 4); err != nil {
+			t.Fatalf("err: %v", err)
+		}
+
+		if !bytes.Equal(buf, []byte("ping")) {
+			t.Fatalf("bad: %v", buf)
+		}
+		conn.Write([]byte("pong"))
+	}()
+	lAddr := l.Addr().(*net.TCPAddr)
+
+	// Make server
+	s := &Server{config: &Config{
+		Rules:    PermitNone(),
+		Resolver: DNSResolver{},
+		Logger:   log.New(os.Stdout, "", log.LstdFlags),
+	}}
+
+	// Create the connect request
+	buf := bytes.NewBuffer(nil)
+	buf.Write([]byte{5, 1, 0, 1, 127, 0, 0, 1})
+
+	port := []byte{0, 0}
+	binary.BigEndian.PutUint16(port, uint16(lAddr.Port))
+	buf.Write(port)
+
+	// Send a ping
+	buf.Write([]byte("ping"))
+
+	// Handle the request
+	resp := &MockConn{}
+	req, err := NewRequest(buf)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if err := s.handleRequest(req, resp); !strings.Contains(err.Error(), "blocked by rules") {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Verify response
+	out := resp.buf.Bytes()
+	expected := []byte{
+		5,
+		2,
+		0,
+		1,
+		0, 0, 0, 0,
+		0, 0,
+	}
+
+	if !bytes.Equal(out, expected) {
+		t.Fatalf("bad: %v %v", out, expected)
+	}
+}

socks5/resolver.go

@@ -0,0 +1,23 @@
+package socks5
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+// NameResolver is used to implement custom name resolution
+type NameResolver interface {
+	Resolve(ctx context.Context, name string) (context.Context, net.IP, error)
+}
+
+// DNSResolver uses the system DNS to resolve host names
+type DNSResolver struct{}
+
+func (d DNSResolver) Resolve(ctx context.Context, name string) (context.Context, net.IP, error) {
+	addr, err := net.ResolveIPAddr("ip", name)
+	if err != nil {
+		return ctx, nil, err
+	}
+	return ctx, addr.IP, err
+}

socks5/resolver_test.go

@@ -0,0 +1,21 @@
+package socks5
+
+import (
+	"testing"
+
+	"golang.org/x/net/context"
+)
+
+func TestDNSResolver(t *testing.T) {
+	d := DNSResolver{}
+	ctx := context.Background()
+
+	_, addr, err := d.Resolve(ctx, "localhost")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if !addr.IsLoopback() {
+		t.Fatalf("expected loopback")
+	}
+}

socks5/ruleset.go

@@ -0,0 +1,41 @@
+package socks5
+
+import (
+	"golang.org/x/net/context"
+)
+
+// RuleSet is used to provide custom rules to allow or prohibit actions
+type RuleSet interface {
+	Allow(ctx context.Context, req *Request) (context.Context, bool)
+}
+
+// PermitAll returns a RuleSet which allows all types of connections
+func PermitAll() RuleSet {
+	return &PermitCommand{true, true, true}
+}
+
+// PermitNone returns a RuleSet which disallows all types of connections
+func PermitNone() RuleSet {
+	return &PermitCommand{false, false, false}
+}
+
+// PermitCommand is an implementation of the RuleSet which
+// enables filtering supported commands
+type PermitCommand struct {
+	EnableConnect   bool
+	EnableBind      bool
+	EnableAssociate bool
+}
+
+func (p *PermitCommand) Allow(ctx context.Context, req *Request) (context.Context, bool) {
+	switch req.Command {
+	case ConnectCommand:
+		return ctx, p.EnableConnect
+	case BindCommand:
+		return ctx, p.EnableBind
+	case AssociateCommand:
+		return ctx, p.EnableAssociate
+	}
+
+	return ctx, false
+}

socks5/ruleset_test.go

@@ -0,0 +1,24 @@
+package socks5
+
+import (
+	"testing"
+
+	"golang.org/x/net/context"
+)
+
+func TestPermitCommand(t *testing.T) {
+	ctx := context.Background()
+	r := &PermitCommand{true, false, false}
+
+	if _, ok := r.Allow(ctx, &Request{Command: ConnectCommand}); !ok {
+		t.Fatalf("expect connect")
+	}
+
+	if _, ok := r.Allow(ctx, &Request{Command: BindCommand}); ok {
+		t.Fatalf("do not expect bind")
+	}
+
+	if _, ok := r.Allow(ctx, &Request{Command: AssociateCommand}); ok {
+		t.Fatalf("do not expect associate")
+	}
+}

socks5/socks5.go

@@ -0,0 +1,169 @@
+package socks5
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"os"
+
+	"golang.org/x/net/context"
+)
+
+const (
+	socks5Version = uint8(5)
+)
+
+// Config is used to setup and configure a Server
+type Config struct {
+	// AuthMethods can be provided to implement custom authentication
+	// By default, "auth-less" mode is enabled.
+	// For password-based auth use UserPassAuthenticator.
+	AuthMethods []Authenticator
+
+	// If provided, username/password authentication is enabled,
+	// by appending a UserPassAuthenticator to AuthMethods. If not provided,
+	// and AUthMethods is nil, then "auth-less" mode is enabled.
+	Credentials CredentialStore
+
+	// Resolver can be provided to do custom name resolution.
+	// Defaults to DNSResolver if not provided.
+	Resolver NameResolver
+
+	// Rules is provided to enable custom logic around permitting
+	// various commands. If not provided, PermitAll is used.
+	Rules RuleSet
+
+	// Rewriter can be used to transparently rewrite addresses.
+	// This is invoked before the RuleSet is invoked.
+	// Defaults to NoRewrite.
+	Rewriter AddressRewriter
+
+	// BindIP is used for bind or udp associate
+	BindIP net.IP
+
+	// Logger can be used to provide a custom log target.
+	// Defaults to stdout.
+	Logger *log.Logger
+
+	// Optional function for dialing out
+	Dial func(ctx context.Context, network, addr string) (net.Conn, error)
+}
+
+// Server is reponsible for accepting connections and handling
+// the details of the SOCKS5 protocol
+type Server struct {
+	config      *Config
+	authMethods map[uint8]Authenticator
+}
+
+// New creates a new Server and potentially returns an error
+func New(conf *Config) (*Server, error) {
+	// Ensure we have at least one authentication method enabled
+	if len(conf.AuthMethods) == 0 {
+		if conf.Credentials != nil {
+			conf.AuthMethods = []Authenticator{&UserPassAuthenticator{conf.Credentials}}
+		} else {
+			conf.AuthMethods = []Authenticator{&NoAuthAuthenticator{}}
+		}
+	}
+
+	// Ensure we have a DNS resolver
+	if conf.Resolver == nil {
+		conf.Resolver = DNSResolver{}
+	}
+
+	// Ensure we have a rule set
+	if conf.Rules == nil {
+		conf.Rules = PermitAll()
+	}
+
+	// Ensure we have a log target
+	if conf.Logger == nil {
+		conf.Logger = log.New(os.Stdout, "", log.LstdFlags)
+	}
+
+	server := &Server{
+		config: conf,
+	}
+
+	server.authMethods = make(map[uint8]Authenticator)
+
+	for _, a := range conf.AuthMethods {
+		server.authMethods[a.GetCode()] = a
+	}
+
+	return server, nil
+}
+
+// ListenAndServe is used to create a listener and serve on it
+func (s *Server) ListenAndServe(network, addr string) error {
+	l, err := net.Listen(network, addr)
+	if err != nil {
+		return err
+	}
+	return s.Serve(l)
+}
+
+// Serve is used to serve connections from a listener
+func (s *Server) Serve(l net.Listener) error {
+	for {
+		conn, err := l.Accept()
+		if err != nil {
+			return err
+		}
+		go s.ServeConn(conn)
+	}
+	return nil
+}
+
+// ServeConn is used to serve a single connection.
+func (s *Server) ServeConn(conn net.Conn) error {
+	defer conn.Close()
+	bufConn := bufio.NewReader(conn)
+
+	// Read the version byte
+	version := []byte{0}
+	if _, err := bufConn.Read(version); err != nil {
+		s.config.Logger.Printf("[ERR] socks: Failed to get version byte: %v", err)
+		return err
+	}
+
+	// Ensure we are compatible
+	if version[0] != socks5Version {
+		err := fmt.Errorf("Unsupported SOCKS version: %v", version)
+		s.config.Logger.Printf("[ERR] socks: %v", err)
+		return err
+	}
+
+	// Authenticate the connection
+	authContext, err := s.authenticate(conn, bufConn)
+	if err != nil {
+		err = fmt.Errorf("Failed to authenticate: %v", err)
+		s.config.Logger.Printf("[ERR] socks: %v", err)
+		return err
+	}
+
+	request, err := NewRequest(bufConn)
+	if err != nil {
+		if err == unrecognizedAddrType {
+			if err := sendReply(conn, addrTypeNotSupported, nil); err != nil {
+				return fmt.Errorf("Failed to send reply: %v", err)
+			}
+		}
+		return fmt.Errorf("Failed to read destination address: %v", err)
+	}
+	request.AuthContext = authContext
+	if client, ok := conn.RemoteAddr().(*net.TCPAddr); ok {
+		request.RemoteAddr = &AddrSpec{IP: client.IP, Port: client.Port}
+	}
+
+	// Process the client request
+	if err := s.handleRequest(request, conn); err != nil {
+		err = fmt.Errorf("Failed to handle request: %v", err)
+		s.config.Logger.Printf("[ERR] socks: %v", err)
+		return err
+	}
+
+	return nil
+}

socks5/socks5_test.go

@@ -0,0 +1,110 @@
+package socks5
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"log"
+	"net"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestSOCKS5_Connect(t *testing.T) {
+	// Create a local listener
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	go func() {
+		conn, err := l.Accept()
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		defer conn.Close()
+
+		buf := make([]byte, 4)
+		if _, err := io.ReadAtLeast(conn, buf, 4); err != nil {
+			t.Fatalf("err: %v", err)
+		}
+
+		if !bytes.Equal(buf, []byte("ping")) {
+			t.Fatalf("bad: %v", buf)
+		}
+		conn.Write([]byte("pong"))
+	}()
+	lAddr := l.Addr().(*net.TCPAddr)
+
+	// Create a socks server
+	creds := StaticCredentials{
+		"foo": "bar",
+	}
+	cator := UserPassAuthenticator{Credentials: creds}
+	conf := &Config{
+		AuthMethods: []Authenticator{cator},
+		Logger:      log.New(os.Stdout, "", log.LstdFlags),
+	}
+	serv, err := New(conf)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Start listening
+	go func() {
+		if err := serv.ListenAndServe("tcp", "127.0.0.1:12365"); err != nil {
+			t.Fatalf("err: %v", err)
+		}
+	}()
+	time.Sleep(10 * time.Millisecond)
+
+	// Get a local conn
+	conn, err := net.Dial("tcp", "127.0.0.1:12365")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Connect, auth and connec to local
+	req := bytes.NewBuffer(nil)
+	req.Write([]byte{5})
+	req.Write([]byte{2, NoAuth, UserPassAuth})
+	req.Write([]byte{1, 3, 'f', 'o', 'o', 3, 'b', 'a', 'r'})
+	req.Write([]byte{5, 1, 0, 1, 127, 0, 0, 1})
+
+	port := []byte{0, 0}
+	binary.BigEndian.PutUint16(port, uint16(lAddr.Port))
+	req.Write(port)
+
+	// Send a ping
+	req.Write([]byte("ping"))
+
+	// Send all the bytes
+	conn.Write(req.Bytes())
+
+	// Verify response
+	expected := []byte{
+		socks5Version, UserPassAuth,
+		1, authSuccess,
+		5,
+		0,
+		0,
+		1,
+		127, 0, 0, 1,
+		0, 0,
+		'p', 'o', 'n', 'g',
+	}
+	out := make([]byte, len(expected))
+
+	conn.SetDeadline(time.Now().Add(time.Second))
+	if _, err := io.ReadAtLeast(conn, out, len(out)); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Ignore the port
+	out[12] = 0
+	out[13] = 0
+
+	if !bytes.Equal(out, expected) {
+		t.Fatalf("bad: %v", out)
+	}
+}