go-libtor - Self-contained Tor from Go

Thego-libtorproject is a self-contained, fully statically linked Tor library for Go. It consists of an elaborate suite of Go/CGO wrappers around the original C/C++ Tor library and its dependencies (zlib,libeventandopenssl).

Library	Version	Commit
zlib	1.2.11	cacf7f1d4e3d44d871b605da3b647f07d718623f
libevent	2.2.0-alpha-dev	d433f847334fff9da8e13e2dc7fdf5c0997b20b0
openssl	1.1.1-stable	46dc0bca6cd623c42489c57e62c69cf568335664
tor	0.3.5.14-dev	1693b6151e1369ce0938761cac95e7a0a524f5f3

The library is currently supported on:

• Linuxamd64,386,arm64andarm;both withlibcandmusl.
• Androidamd64,386,arm64andarm;specifically viagomobile.

Installation (GOPATH)

The goal of this library is to be a self-contained Tor package for Go. As such, it plays nice with the usualgo getworkflow. That said, building Tor and all its dependencies locally can take quite a while, so it's recommended to rungo getin verbose mode.

$ go get -u -v -x github.com/ipsn/go-libtor

You'll also need thebinebindings to interface with the library:

go get -u github.com/cretz/bine/tor

Installation (Go modules)

This library is compatible with Go modules. All you should need is to importgithub.com/ipsn/go-libtorand wait out the build. We suggest runninggo build -v -xthe first time after adding thego-libtordependency to avoid frustration, otherwise Go will build the 1000+ C files without any progress report.

Usage

Thego-libtorproject does not contain a full Go API to interface Tor with, rather only the smallest building block to start up an embedded instance. The reason is because there is already a solid Go project out there (github.com/cretz/bine) which focuses on interfacing.

Using both projects in combination however is straightforward:

packagemain

import(
"context"
"fmt"
"log"
"net/http"
"os"
"time"

"github.com/cretz/bine/tor"
"github.com/ipsn/go-libtor"
)

funcmain() {
// Start tor with some defaults + elevated verbosity
fmt.Println("Starting and registering onion service, please wait a bit...")
t,err:=tor.Start(nil,&tor.StartConf{ProcessCreator:libtor.Creator,DebugWriter:os.Stderr})
iferr!=nil{
log.Panicf("Failed to start tor: %v",err)
}
defert.Close()

// Wait at most a few minutes to publish the service
ctx,cancel:=context.WithTimeout(context.Background(),3*time.Minute)
defercancel()

// Create an onion service to listen on any port but show as 80
onion,err:=t.Listen(ctx,&tor.ListenConf{RemotePorts:[]int{80}})
iferr!=nil{
log.Panicf("Failed to create onion service: %v",err)
}
deferonion.Close()

fmt.Printf("Please open a Tor capable browser and navigate to http://%v.onion\n",onion.ID)

// Run a Hello-World HTTP service until terminated
http.HandleFunc("/",func(whttp.ResponseWriter,r*http.Request) {
fmt.Fprintf(w,"Hello, Tor!")
})
http.Serve(onion,nil)
}

The above code will:

• Start up a new Tor process from within your statically linked binary
• Register a new anonymous onion TCP endpoint for remote clients
• Start an HTTP server using the Tor network as its transport layer

$ go run main.go

Starting and registering onion service, please wait a bit...
[...]
Enabling network before waiting for publication
[...]
Waiting for publication
[...]
Please open a Tor capable browser and navigate to http://s7t3iy76h54cjacg.onion

Well, that was easy. With a few lines of Go code we've created a hidden TCP service inside the Tor network. The browser used to test the server with above wasBrave,which among others has built in experimental support for Tor.

Mobile devices

The advantage ofgo-libtorstarts to show when building to more exotic platforms, since it's composed of simple CGO Go files. As it doesn't require custom build steps or tooling, it plays nice with the Go ecosystem,gomobileincluded:

Let's see how much effort would it be to deploy onto Android:

packagedemo

import(
"context"
"fmt"
"log"
"net/http"
"os"
"time"

"github.com/cretz/bine/tor"
"github.com/ipsn/go-libtor"
)

// Run starts up an embedded Tor process, starts a hidden onion service on a new
// goroutine and returns the onion address. We're cheating here and not caring
// about actually cleaning up after ourselves.
funcRun(datadirstring)string{
// Start tor with some defaults + elevated verbosity
fmt.Println("Starting and registering onion service, please wait a bit...")
t,err:=tor.Start(nil,&tor.StartConf{ProcessCreator:libtor.Creator,DebugWriter:os.Stderr,DataDir:datadir})
iferr!=nil{
log.Panicf("Failed to start tor: %v",err)
}
// Wait at most a few minutes to publish the service
ctx,cancel:=context.WithTimeout(context.Background(),3*time.Minute)
defercancel()

// Create an onion service to listen on any port but show as 80
onion,err:=t.Listen(ctx,&tor.ListenConf{RemotePorts:[]int{80}})
iferr!=nil{
log.Panicf("Failed to create onion service: %v",err)
}
fmt.Printf("Please open a Tor capable browser and navigate to http://%v.onion\n",onion.ID)

// Run a Hello-World HTTP service until terminated
http.HandleFunc("/",func(whttp.ResponseWriter,r*http.Request) {
fmt.Fprintf(w,"Hello, Tor! This is Android!!!")
})
gohttp.Serve(onion,nil)

returnfmt.Sprintf("http://%v.onion",onion.ID)
}

The above code does approximately the same thing as the one before, just in its own package with a trivial API since we want to make an Android archive, not an entire.apk.We can invokegomobileto bind it:

$ gomobile bind -v -x.
[...many logs, much wow...]
$ ls -al demo*
-rw-r--r-- 1 karalabe 38976071 Jul 19 18:46 demo.aar
-rw-r--r-- 1 karalabe 6162 Jul 19 18:46 demo-sources.jar
$ unzip -l demo.aar
Archive: demo.aar
Length Date Time Name
--------- ---------- ----- ----
143 1980-00-00 00:00 AndroidManifest.xml
25 1980-00-00 00:00 proguard.txt
11044 1980-00-00 00:00 classes.jar
26102356 1980-00-00 00:00 jni/armeabi-v7a/libgojni.so
27085856 1980-00-00 00:00 jni/arm64-v8a/libgojni.so
26327236 1980-00-00 00:00 jni/x86/libgojni.so
27757968 1980-00-00 00:00 jni/x86_64/libgojni.so
0 1980-00-00 00:00 R.txt
0 1980-00-00 00:00 res/
--------- -------
107284628 9 files

Explaining how to load an.aarinto an Android project is beyond the scope of this article, but you can load the archive with Android Studio as a module and edit your Gradle build config to add it as a dependency. An overly crude app would just start the server and drop the onion URL into an Android label:

That's actually it! We've managed to get a Tor hidden service running from an Android phone and access it from another device through the Tor network, all through 40 lines of Go- and 3 lines of Java code.

Credits

This repository is maintained by Péter Szilágyi (@karalabe), but authorship of all code contained inside belongs to the individual upstream projects.

License

3-Clause BSD.