AUTH-2394 added socks5 proxy

socks/request.go

@@ -0,0 +1,195 @@
+package socks
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+)
+
+const (
+	// version
+	socks5Version = uint8(5)
+
+	// commands https://tools.ietf.org/html/rfc1928#section-4
+	connectCommand   = uint8(1)
+	bindCommand      = uint8(2)
+	associateCommand = uint8(3)
+
+	// address types
+	ipv4Address = uint8(1)
+	fqdnAddress = uint8(3)
+	ipv6Address = uint8(4)
+)
+
+// https://tools.ietf.org/html/rfc1928#section-6
+const (
+	successReply uint8 = iota
+	serverFailure
+	ruleFailure
+	networkUnreachable
+	hostUnreachable
+	connectionRefused
+	ttlExpired
+	commandNotSupported
+	addrTypeNotSupported
+)
+
+// AddrSpec is used to return the target IPv4, IPv6, or a FQDN
+type AddrSpec struct {
+	FQDN string
+	IP   net.IP
+	Port int
+}
+
+// String gives a host version of the Address
+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 len(a.IP) != 0 {
+		return net.JoinHostPort(a.IP.String(), strconv.Itoa(a.Port))
+	}
+	return net.JoinHostPort(a.FQDN, strconv.Itoa(a.Port))
+}
+
+// Request is a SOCKS5 command with supporting field of the connection
+type Request struct {
+	// Protocol version
+	Version uint8
+	// Requested command
+	Command uint8
+	// AddrSpec of the destination
+	DestAddr *AddrSpec
+	// reading from the connection
+	bufConn io.Reader
+}
+
+// NewRequest creates a new request from the connection data stream
+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 compatibility
+	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
+	}
+
+	return &Request{
+		Version:  socks5Version,
+		Command:  header[1],
+		DestAddr: dest,
+		bufConn:  bufConn,
+	}, nil
+}
+
+func sendReply(w io.Writer, resp uint8, addr *AddrSpec) error {
+	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
+}
+
+// readAddrSpec is used to read AddrSpec.
+// Expects an address type byte, followed 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, fmt.Errorf("Unrecognized address type")
+	}
+
+	// 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
+}