Initial commit

.gitlab-ci.yml

+stages:
+  - build
+
+build:
+  stage: build
+  image: "ai/build:stretch"
+  script:
+    - env DEBIAN_FRONTEND=noninteractive apt-get -qy install golang
+    - mkdir build/git.autistici.org/ai3
+    - ln -s $PWD build/git.autistici.org/ai3/float-debug-proxy
+    - env GOPATH=$PWD/build go build -o float-debug-proxy git.autistici.org/ai3/float-debug-proxy
+  artifacts:
+    paths:
+      - float-debug-proxy
+  only:
+    - master

README.md

+float-debug-proxy
+===
+
+A SOCKS5 proxy server for testing environments.
+
+This tool solves a very specific problem: when using
+[float](https://git.autistici.org/ai3/float) test environments, we'd
+like to use a browser to debug the services, but the browser needs its
+own testing environment, using the DNS provided by the test
+environment itself. At the same time, we would like to do this without
+any changes to the user environment (such as manually creating entries
+in /etc/hosts, for instance), because they pose an unreasonable burden
+on the user.
+
+One way to achieve this with low friction is to use a proxy running on
+the test environment itself, so that by simply pointing the browser at
+it would get you the "internal" view. SSH can easily do this by
+running its own SOCKS proxy, for example, but then we run into another
+issue: ssh uses the system resolver, and if we point
+*/etc/resolv.conf* at the test environment authoritative DNS servers,
+we break the test environment isolation and make it harder to run
+environments with "real" domains (if there is any overlap with the CI
+domains, for instance, Ansible will break). That's how we get to the
+tool you're looking at right now: a simple SOCKS5 proxy, that can be
+pointed at a specific DNS resolver, ignoring the system
+/etc/resolv.conf. It will run on a test environment frontend node,
+without any authentication (these are non-public hosts). You can then
+run a test browser session with:
+
+    $BROWSER --user-data-dir /tmp/test --proxy-server=socks5://$IP:9051
+
+(with suitable values of $BROWSER and $IP).

proxy.go

+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"log"
+	"net"
+
+	"github.com/armon/go-socks5"
+	"github.com/miekg/dns"
+)
+
+var (
+	addr       = flag.String("addr", ":9051", "`addr`ess to listen on")
+	resolverIP = flag.String("resolver", "127.0.0.1", "IP `addr`ess of the DNS resolver to use")
+)
+
+// IPv4-only resolver (for now).
+type resolver struct {
+	addr string
+}
+
+func (r *resolver) Resolve(ctx context.Context, name string) (context.Context, net.IP, error) {
+	m := new(dns.Msg)
+	m.SetQuestion(dns.Fqdn(name), dns.TypeA)
+	m.RecursionDesired = true
+
+	in, err := dns.Exchange(m, r.addr)
+	if err != nil {
+		return ctx, nil, err
+	}
+	for _, rec := range in.Answer {
+		if a, ok := rec.(*dns.A); ok {
+			return ctx, a.A, nil
+		}
+	}
+	return ctx, nil, errors.New("not found")
+}
+
+func main() {
+	log.SetFlags(0)
+	flag.Parse()
+
+	config := socks5.Config{
+		Resolver: &resolver{*resolverIP + ":53"},
+	}
+	server, err := socks5.New(&config)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if err := server.ListenAndServe("tcp", *addr); err != nil {
+		log.Fatal(err)
+	}
+}

vendor/github.com/armon/go-socks5/LICENSE

+The MIT License (MIT)
+
+Copyright (c) 2014 Armon Dadgar
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

vendor/github.com/armon/go-socks5/README.md

+go-socks5 [![Build Status](https://travis-ci.org/armon/go-socks5.png)](https://travis-ci.org/armon/go-socks5)
+=========
+
+Provides the `socks5` package that implements a [SOCKS5 server](http://en.wikipedia.org/wiki/SOCKS).
+SOCKS (Secure Sockets) is used to route traffic between a client and server through
+an intermediate proxy layer. This can be used to bypass firewalls or NATs.
+
+Feature
+=======
+
+The package has the following features:
+* "No Auth" mode
+* User/Password authentication
+* Support for the CONNECT command
+* Rules to do granular filtering of commands
+* Custom DNS resolution
+* Unit tests
+
+TODO
+====
+
+The package still needs the following:
+* Support for the BIND command
+* Support for the ASSOCIATE command
+
+
+Example
+=======
+
+Below is a simple example of usage
+
+```go
+// Create a SOCKS5 server
+conf := &socks5.Config{}
+server, err := socks5.New(conf)
+if err != nil {
+  panic(err)
+}
+
+// Create SOCKS5 proxy on localhost port 8000
+if err := server.ListenAndServe("tcp", "127.0.0.1:8000"); err != nil {
+  panic(err)
+}
+```
+

vendor/github.com/armon/go-socks5/auth.go

+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
+}

vendor/github.com/armon/go-socks5/credentials.go

+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
+}

vendor/github.com/armon/go-socks5/request.go

+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)