From 5c369f00d46d94207e853e9af6f5eee2b96b3987 Mon Sep 17 00:00:00 2001
From: Armon Dadgar <armon.dadgar@gmail.com>
Date: Thu, 23 Jan 2014 11:28:30 -0800
Subject: [PATCH] Adding base socks server

---
 socks5.go | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 socks5.go

diff --git a/socks5.go b/socks5.go
new file mode 100644
index 0000000..a6a6932
--- /dev/null
+++ b/socks5.go
@@ -0,0 +1,108 @@
+package socks5
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+)
+
+const (
+	socks5Version = uint8(5)
+)
+
+// Config is used to setup and configure a Server
+type Config struct {
+	// If provided, username/password authentication is enabled
+	// otherwise, non-authenticated mode is allowed
+	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
+}
+
+// Server is reponsible for accepting connections and handling
+// the details of the SOCKS5 protocol
+type Server struct {
+	config *Config
+}
+
+// New creates a new Server and potentially returns an error
+func New(conf *Config) (*Server, error) {
+	// 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()
+	}
+
+	server := &Server{
+		config: conf,
+	}
+	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 {
+		log.Printf("[ERR] 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)
+		log.Printf("[ERR] %v", err)
+		return err
+	}
+
+	// Authenticate the connection
+	if err := s.authenticate(conn, bufConn); err != nil {
+		err = fmt.Errorf("Failed to authenticate: %v", err)
+		log.Printf("[ERR] %v", err)
+		return err
+	}
+
+	// Process the client request
+	if err := s.handleRequest(conn, bufConn); err != nil {
+		err = fmt.Errorf("Failed to handle request: %v", err)
+		log.Printf("[ERR] %v", err)
+		return err
+	}
+
+	return nil
+}