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main.go
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main.go
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package main
import (
"flag"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/http"
"net/http/httputil"
"net/url"
"os"
"os/user"
"strings"
"sync"
"time"
"golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
)
func currentUser() *user.User {
u, err := user.Current()
if err != nil {
panic(err)
}
return u
}
func defaultUsername() string {
u := currentUser()
name := u.Username
index := strings.Index(name, "\\")
if index != -1 {
name = name[index+1:]
}
return name
}
func defaultKeyFile() string {
return currentUser().HomeDir + "/.ssh/id_rsa"
}
func loadKeyFile(filename string) (key ssh.Signer, err error) {
data, err := ioutil.ReadFile(filename)
if err != nil {
return
}
key, err = ssh.ParsePrivateKey(data)
if err != nil {
return
}
return
}
func ensurePort(host string, defaultPort int) string {
cindex := strings.Index(host, ":")
if cindex == -1 {
return fmt.Sprintf("%s:%d", host, defaultPort)
}
return host
}
func extractHost(url *url.URL) string {
host := url.Host
cindex := strings.Index(host, ":")
if cindex != -1 {
host = host[:cindex]
}
return host
}
func extractHostPort(url *url.URL, defaultPort int) string {
hostport := url.Host
cindex := strings.Index(hostport, ":")
if cindex == -1 {
hostport = fmt.Sprintf("%s:%d", hostport, defaultPort)
}
return hostport
}
type SecureReverseProxy struct {
host string
config *config
sshConfig *ssh.ClientConfig
remoteAvailable *sync.Cond
remote *ssh.Client
proxy httputil.ReverseProxy
direct httputil.ReverseProxy
}
func (p *SecureReverseProxy) getActions(url *url.URL) configActions {
host := extractHost(url)
if p.config != nil {
for _, c := range p.config.cases {
if c.mask.MatchString(host) {
return c.actions
}
}
}
return actionNone
}
func NewSecureReverseProxy(host string, config *config, sshConfig *ssh.ClientConfig) *SecureReverseProxy {
p := &SecureReverseProxy{}
p.host = host
p.config = config
p.sshConfig = sshConfig
p.remoteAvailable = sync.NewCond(&sync.Mutex{})
p.proxy.Director = func(req *http.Request) {}
p.proxy.Transport = &http.Transport{
Proxy: nil,
Dial: p.dial,
}
p.direct.Director = func(req *http.Request) {}
go p.reconnectLoop()
return p
}
func (p *SecureReverseProxy) reconnectLoop() {
p.remoteAvailable.L.Lock()
defer p.remoteAvailable.L.Unlock()
for {
log.Printf("Connecting to %s...", p.host)
remote, err := ssh.Dial("tcp", p.host, p.sshConfig)
if err != nil {
log.Printf("Connect failed: %s", err)
time.Sleep(5 * time.Second)
continue
}
err = p.connected(remote)
if err != nil {
log.Printf("Disconnected: %s", err)
}
remote.Close()
}
}
func (p *SecureReverseProxy) connected(remote *ssh.Client) error {
p.remote = remote
defer func() {
p.remote = nil
}()
p.remoteAvailable.Broadcast()
p.remoteAvailable.L.Unlock()
defer p.remoteAvailable.L.Lock()
log.Printf("Connected to %s\n", remote.ServerVersion())
stop := make(chan struct{})
defer close(stop)
go p.keepalive(remote, stop)
return remote.Wait()
}
func (p *SecureReverseProxy) keepalive(remote *ssh.Client, stop <-chan struct{}) {
t := time.NewTicker(30 * time.Second)
defer t.Stop()
for {
select {
case <-stop:
return
case <-t.C:
// just try to connect somewhere once in a while, error is not important
c, err := remote.Dial("tcp", "127.255.255.42:0")
if err == nil {
c.Close()
}
}
}
}
func (p *SecureReverseProxy) waitForRemote() *ssh.Client {
p.remoteAvailable.L.Lock()
defer p.remoteAvailable.L.Unlock()
for p.remote == nil {
p.remoteAvailable.Wait()
}
return p.remote
}
func (p *SecureReverseProxy) dial(n, addr string) (net.Conn, error) {
remote := p.waitForRemote()
c, err := remote.Dial(n, addr)
if err != nil {
log.Printf("CONNECT %s: %s", addr, err)
}
return c, err
}
func isNormalError(err error) bool {
if err == io.EOF {
return true
}
if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
return true
}
return false
}
func (p *SecureReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
if req.Host == "localhost" || strings.HasPrefix(req.Host, "localhost:") {
rw.WriteHeader(200)
io.WriteString(rw, "TODO: console")
return
}
var url string
var origurl string
actions := p.getActions(req.URL)
redirect := false
if req.Method == "CONNECT" {
origurl = extractHostPort(req.URL, 443)
} else {
origurl = req.URL.String()
if req.URL.Scheme == "http" && actions&actionForceHTTPS != 0 {
if req.Method == "GET" || req.Method == "HEAD" {
redirect = true
}
req.URL.Scheme = "https"
url = req.URL.String()
}
}
if len(url) == 0 {
url = origurl
}
prefix := ""
if actions&actionDirect != 0 {
prefix = "(direct) "
}
suffix := ""
if actions&actionBlock != 0 {
suffix = " (blocked)"
}
log.Printf("%s%s %s%s", prefix, req.Method, origurl, suffix)
if actions&actionBlock != 0 {
rw.WriteHeader(503)
io.WriteString(rw, "Server blocked")
return
}
if redirect {
rw.Header().Set("Location", url)
rw.WriteHeader(307)
if req.Method == "GET" {
io.WriteString(rw, url)
}
return
}
if req.Method == "CONNECT" {
rwh, ok := rw.(http.Hijacker)
if !ok {
rw.WriteHeader(503)
io.WriteString(rw, "Cannot hijack connection for the CONNECT method")
return
}
dial := p.dial
if actions&actionDirect != 0 {
dial = net.Dial
}
remote, err := dial("tcp", url)
if err != nil {
rw.WriteHeader(503)
io.WriteString(rw, "CONNECT failed: "+err.Error())
log.Printf("%s %s: %s", req.Method, url, err)
return
}
defer remote.Close()
local, b, err := rwh.Hijack()
if err != nil {
rw.WriteHeader(503)
io.WriteString(rw, "HIJACK failed: "+err.Error())
return
}
defer local.Close()
io.WriteString(b, "HTTP/1.1 200 OK\r\n\r\n")
b.Flush() // this is the last write into b
// write side runs it its own goroutine
go func() {
defer local.Close()
defer remote.Close()
var buffer [65536]byte
done := false
for !done {
n, err := remote.Read(buffer[:])
if n > 0 {
_, werr := local.Write(buffer[:n])
if werr != nil {
if !isNormalError(werr) {
//log.Printf("%s: local write: %s", url, werr)
}
done = true
}
}
if err != nil {
if !isNormalError(err) {
//log.Printf("%s: remote read: %s", url, err)
}
done = true
}
}
}()
// read side runs here, first we grab what we have in in b
var buffer [65536]byte
done := false
for !done {
n, err := b.Read(buffer[:])
if n > 0 {
_, werr := remote.Write(buffer[:n])
if werr != nil {
if !isNormalError(werr) {
//log.Printf("%s: remote write: %s", url, werr)
}
done = true
}
}
if err != nil {
if !isNormalError(err) {
//log.Printf("%s: local read: %s", url, err)
}
done = true
}
}
return
}
if actions&actionDirect != 0 {
p.direct.ServeHTTP(rw, req)
} else {
p.proxy.ServeHTTP(rw, req)
}
}
func (p *SecureReverseProxy) ListenAndServe(addr string) error {
return http.ListenAndServe(addr, p)
}
func main() {
var host string
var keyFile string
var configFile string = "config.txt"
var listenAddr string = "127.0.0.1:8080"
flag.StringVar(&host, "host", host, "ssh hostname")
flag.StringVar(&keyFile, "key", keyFile, "ssh key file")
flag.StringVar(&configFile, "config", configFile, "proxy config file")
flag.StringVar(&listenAddr, "listen", listenAddr, "proxy listen address")
flag.Parse()
if host == "" {
flag.Usage()
return
}
host = ensurePort(host, 22)
// Determine which auth methods we can use
var authMethods []ssh.AuthMethod
if authsock := os.Getenv("SSH_AUTH_SOCK"); authsock != "" {
// Connect to local ssh agent
var conn net.Conn
var err error
if authsock[0] == '/' || authsock[0] == '@' {
conn, err = net.Dial("unix", authsock)
} else {
conn, err = net.Dial("tcp", authsock)
}
if err != nil {
log.Fatal(err)
}
defer conn.Close()
client := agent.NewClient(conn)
authMethods = append(authMethods, ssh.PublicKeysCallback(client.Signers))
}
if len(authMethods) == 0 && keyFile == "" {
// Use default key when there's no agent
keyFile = defaultKeyFile()
}
if keyFile != "" {
// Key file must not have a password
key, err := loadKeyFile(keyFile)
if err != nil {
log.Fatal(err)
}
authMethods = append(authMethods, ssh.PublicKeys(key))
}
if len(authMethods) == 0 {
log.Fatal("No authentication methods specified")
}
config, err := loadConfigFile(configFile)
if err != nil {
log.Fatal(err)
}
sshConfig := &ssh.ClientConfig{
User: defaultUsername(),
Auth: authMethods,
Timeout: 30 * time.Second,
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}
p := NewSecureReverseProxy(host, config, sshConfig)
err = p.ListenAndServe(listenAddr)
if err != nil {
log.Fatal(err)
}
}