README
¶
gomitmproxy
This is a customizable HTTP proxy with TLS interception support. It was created as a part of AdGuard Home. However, it can be used for different purposes so we decided to make it a separate project.
Features
- HTTP proxy
- HTTP over TLS (HTTPS) proxy
- Proxy authorization
- TLS termination
How to use gomitmproxy
Simple HTTP proxy
package main
import (
"log"
"net"
"os"
"os/signal"
"syscall"
"github.com/AdguardTeam/gomitmproxy"
)
func main() {
proxy := gomitmproxy.NewProxy(gomitmproxy.Config{
ListenAddr: &net.TCPAddr{
IP: net.IPv4(0, 0, 0, 0),
Port: 8080,
},
})
err := proxy.Start()
if err != nil {
log.Fatal(err)
}
signalChannel := make(chan os.Signal, 1)
signal.Notify(signalChannel, syscall.SIGINT, syscall.SIGTERM)
<-signalChannel
// Clean up
proxy.Close()
}
Modifying requests and responses
You can modify requests and responses using OnRequest and OnResponse handlers.
The example below will block requests to example.net and add a short comment to
the end of every HTML response.
proxy := gomitmproxy.NewProxy(gomitmproxy.Config{
ListenAddr: &net.TCPAddr{
IP: net.IPv4(0, 0, 0, 0),
Port: 8080,
},
OnRequest: func(session *gomitmproxy.Session) (request *http.Request, response *http.Response) {
req := session.Request()
log.Printf("onRequest: %s %s", req.Method, req.URL.String())
if req.URL.Host == "example.net" {
body := strings.NewReader("<html><body><h1>Replaced response</h1></body></html>")
res := gomitmproxy.NewResponse(http.StatusOK, body, req)
res.Header.Set("Content-Type", "text/html")
// Use session props to pass the information about request being blocked
session.SetProp("blocked", true)
return nil, res
}
return nil, nil
},
OnResponse: func(session *gomitmproxy.Session) *http.Response {
log.Printf("onResponse: %s", session.Request().URL.String())
if _, ok := session.GetProp("blocked"); ok {
log.Printf("onResponse: was blocked")
}
res := session.Response()
req := session.Request()
if strings.Index(res.Header.Get("Content-Type"), "text/html") != 0 {
// Do nothing with non-HTML responses
return nil
}
b, err := proxyutil.ReadDecompressedBody(res)
// Close the original body
_ = res.Body.Close()
if err != nil {
return proxyutil.NewErrorResponse(req, err)
}
// Use latin1 before modifying the body
// Using this 1-byte encoding will let us preserve all original characters
// regardless of what exactly is the encoding
body, err := proxyutil.DecodeLatin1(bytes.NewReader(b))
if err != nil {
return proxyutil.NewErrorResponse(session.Request(), err)
}
// Modifying the original body
modifiedBody, err := proxyutil.EncodeLatin1(body + "<!-- EDITED -->")
if err != nil {
return proxyutil.NewErrorResponse(session.Request(), err)
}
res.Body = ioutil.NopCloser(bytes.NewReader(modifiedBody))
res.Header.Del("Content-Encoding")
res.ContentLength = int64(len(modifiedBody))
return res
},
})
Proxy authorization
If you want to protect your proxy with Basic authentication, set Username and Password
fields in the proxy configuration.
proxy := gomitmproxy.NewProxy(gomitmproxy.Config{
ListenAddr: &net.TCPAddr{
IP: net.IPv4(0, 0, 0, 0),
Port: 8080,
},
Username: "user",
Password: "pass",
})
HTTP over TLS (HTTPS) proxy
If you want to protect yourself from eavesdropping on your traffic to proxy, you can configure
it to work over a TLS tunnel. This is really simple to do, just set a *tls.Config instance
in your proxy configuration.
tlsConfig := &tls.Config{
Certificates: []tls.Certificate{*proxyCert},
}
proxy := gomitmproxy.NewProxy(gomitmproxy.Config{
ListenAddr: addr,
TLSConfig: tlsConfig,
})
TLS interception
If you want to do TLS termination, you first need to prepare a self-signed certificate
that will be used as a certificates authority. Use the following openssl commands to do this.
openssl genrsa -out demo.key 2048
openssl req -new -x509 -key demo.key -out demo.crt
Now you can use it to initialize MITMConfig:
tlsCert, err := tls.LoadX509KeyPair("demo.crt", "demo.key")
if err != nil {
log.Fatal(err)
}
privateKey := tlsCert.PrivateKey.(*rsa.PrivateKey)
x509c, err := x509.ParseCertificate(tlsCert.Certificate[0])
if err != nil {
log.Fatal(err)
}
mitmConfig, err := mitm.NewConfig(x509c, privateKey, nil)
if err != nil {
log.Fatal(err)
}
mitmConfig.SetValidity(time.Hour * 24 * 7) // generate certs valid for 7 days
mitmConfig.SetOrganization("gomitmproxy") // cert organization
Please note that you can set MITMExceptions to a list of hostnames,
which will be excluded from TLS interception.
proxy := gomitmproxy.NewProxy(gomitmproxy.Config{
ListenAddr: &net.TCPAddr{
IP: net.IPv4(0, 0, 0, 0),
Port: 3333,
},
MITMConfig: mitmConfig,
MITMExceptions: []string{"example.com"},
})
If you configure the APIHost, you'll be able to download the CA certificate
from http://[APIHost]/cert.crt when the proxy is configured.
// Navigate to http://gomitmproxy/cert.crt to download the CA certificate
proxy.APIHost = "gomitmproxy"
Custom certs storage
By default, gomitmproxy uses an in-memory map-based storage for the certificates,
generated while doing TLS interception. It is often necessary to use a different kind
of certificates storage. If this is your case, you can supply your own implementation
of the CertsStorage interface.
// CustomCertsStorage - an example of a custom cert storage
type CustomCertsStorage struct {
certsCache map[string]*tls.Certificate // cache with the generated certificates
}
// Get gets the certificate from the storage
func (c *CustomCertsStorage) Get(key string) (*tls.Certificate, bool) {
v, ok := c.certsCache[key]
return v, ok
}
// Set saves the certificate to the storage
func (c *CustomCertsStorage) Set(key string, cert *tls.Certificate) {
c.certsCache[key] = cert
}
Then pass it to the NewConfig function.
mitmConfig, err := mitm.NewConfig(x509c, privateKey, &CustomCertsStorage{
certsCache: map[string]*tls.Certificate{}},
)
Notable alternatives
- martian - an awesome debugging proxy with TLS interception support.
- goproxy - also supports TLS interception and requests.
TODO
- Basic HTTP proxy without MITM
- Proxy
- Expose APIs for the library users
- How-to doc
- Travis configuration
- Proxy-Authorization
- WebSockets support (see this)
-
certsCache-- allow custom implementations - Support HTTP CONNECT over TLS
- Test plain HTTP requests inside HTTP CONNECT
- Test memory leaks
- Editing response body in a callback
- Handle unknown content-encoding values
- Handle CONNECT to APIHost properly (without trying to actually connect anywhere)
- Allow hijacking connections (!)
- Unit tests
- Check & fix TODOs
- MITM
- Basic MITM
- MITM exceptions
- Handle invalid server certificates properly (not just reset connections)
- Pass the most important tests on badssl.com/dashboard
- Handle certificate authentication
- Allow configuring minimum supported TLS version
- OCSP check (see example)
- (?) HPKP (see example)
- (?) CT logs (see example)
- (?) CRLSets (see example)
Documentation
¶
Overview ¶
Package gomitmproxy implements a configurable mitm proxy wring purely in go.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Config ¶
type Config struct {
ListenAddr *net.TCPAddr // Address to listen to
// TLSConfig is a config to use for the HTTP over TLS proxy
// If not set, gomitmproxy will work as a simple plain HTTP proxy
TLSConfig *tls.Config
// Username for Proxy-Authorization
Username string
// Password for Proxy-Authorization
Password string
MITMConfig *mitm.Config // If not nil, MITM is enabled for the proxy
MITMExceptions []string // A list of hostnames for which MITM will be disabled
// APIHost is a name of the gomitmproxy API
// If it is set to "", there will be no API
// Here are the methods exposed:
// 1. apihost/cert.crt -- serves the authority cert (if MITMConfig is configured)
APIHost string
//
OnConnect func(session *Session, proto string, addr string) net.Conn
// OnRequest is called when the request has been just received,
// but has not been sent to the remote server.
//
// At this stage, it is possible to do the following things:
// 1. Modify or even replace the request
// 2. Supply an HTTP response to be written to the client
//
// Return nil instead of *http.Request or *http.Response to keep
// the original request / response
//
// Note that even if you supply your own HTTP response here,
// the OnResponse handler will be called anyway!
OnRequest func(session *Session) (*http.Request, *http.Response)
// OnResponse is called when the response has been just received,
// but has not been sent to the local client.
//
// At this stage you can either keep the original response,
// or you can replace it with a new one.
OnResponse func(session *Session) *http.Response
// OnError is called if there's an issue with retrieving
// the response from the remote server.
OnError func(session *Session, err error)
}
Config is the configuration of the Proxy
type Context ¶
type Context struct {
// contains filtered or unexported fields
}
Context contains all the necessary information about the connection that is currently processing by the proxy
func (*Context) SetDeadline ¶
SetDeadline sets the read and write deadlines associated with the connection. See net.Conn.SetDeadline for more details.
The difference is that our contexts can be nested, so we search for the topmost parent context recursively and call SetDeadline for its connection only as this is the real underlying network connection.
type Proxy ¶
type Proxy struct {
Config // Proxy configuration
// contains filtered or unexported fields
}
Proxy is a structure with the proxy server configuration and current state
func (*Proxy) Close ¶
func (p *Proxy) Close()
Close sets the proxy to the closing state so it stops receiving new connections, finishes processing any inflight requests, and closes existing connections without reading anymore requests from them.
type Session ¶
type Session struct {
// contains filtered or unexported fields
}
Session contains all the necessary information about the request-response pair that is currently being processed
func (*Session) RemoteAddr ¶
RemoteAddr returns this session's remote address
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
examples
|
|
|
Package mitm implements methods for working with certificates and TLS configurations that are used for mitming connections.
|
Package mitm implements methods for working with certificates and TLS configurations that are used for mitming connections. |
|
Package proxyutil contains different utility methods that will be helpful to gomitmproxy users
|
Package proxyutil contains different utility methods that will be helpful to gomitmproxy users |