initial commit

Author: Marcel Gebhardt

LICENSE

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+MIT License
+
+Copyright (c) 2018 Marcel Gebhardt
+
+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.

README.md

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+# go-ntlm-proxy-auth
+
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![GoDoc](https://godoc.org/github.com/Codehardt/go-ntlm-proxy-auth?status.svg)](https://godoc.org/github.com/Codehardt/go-ntlm-proxy-auth)
+
+With this package, you can connect to http/https servers protected by an NTLM proxy in Golang.
+
+## Example
+
+```golang
+// create a dialer
+dialer := &net.Dialer{
+    Timeout:   30 * time.Second,
+    KeepAlive: 30 * time.Second,
+}
+
+// wrap dial context with NTLM
+ntlmDialContext := ntlm.WrapDialContext(dialer.DialContext, "proxyAddr", "user", "password", "domain")
+
+// create a http(s) client
+client := &http.Client{
+    Transport: &http.Transport{
+        Proxy: nil, // !!! IMPORTANT, do not set proxy here !!!
+        Dial: dialer.Dial,
+        DialContext: ntlmDialContext,
+        // TLSClientConfig: ...
+    },
+}
+```

debug.go

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+package ntlm
+
+var debugf = func(format string, a ...interface{}) {} // discard debug
+
+// SetDebugf sets a debugf function for debug output
+func SetDebugf(f func(format string, a ...interface{})) {
+	debugf = f
+}

ntlm.go

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+package ntlm
+
+import (
+	"bufio"
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+
+	ntlmssp "github.com/Azure/go-ntlmssp"
+)
+
+// DialContext is the DialContext function that should be wrapped with a
+// NTLM Authentication.
+//
+// Example for DialContext:
+//
+// dialContext := (&net.Dialer{KeepAlive: 30*time.Second, Timeout: 30*time.Second}).DialContext
+type DialContext func(ctx context.Context, network, addr string) (net.Conn, error)
+
+// WrapDialContext wraps a DialContext with an NTLM Authentication to a proxy.
+func WrapDialContext(dialContext DialContext, proxyAddress, proxyUsername, proxyPassword, proxyDomain string) DialContext {
+	return func(ctx context.Context, network, addr string) (net.Conn, error) {
+		conn, err := dialContext(ctx, network, proxyAddress)
+		if err != nil {
+			debugf("ntlm> Could not call dial context with proxy: %s", err)
+			return conn, err
+		}
+		// NTLM Step 1: Send Negotiate Message
+		negotiateMessage, err := ntlmssp.NewNegotiateMessage(proxyDomain, "")
+		if err != nil {
+			debugf("ntlm> Could not negotiate domain '%s': %s", proxyDomain, err)
+			return conn, err
+		}
+		debugf("ntlm> NTLM negotiate message: '%s'", base64.StdEncoding.EncodeToString(negotiateMessage))
+		header := make(http.Header)
+		header.Set("Proxy-Authorization", fmt.Sprintf("NTLM %s", base64.StdEncoding.EncodeToString(negotiateMessage)))
+		connect := &http.Request{
+			Method: "CONNECT",
+			URL:    &url.URL{Opaque: addr},
+			Host:   addr,
+			Header: header,
+		}
+		if err := connect.Write(conn); err != nil {
+			debugf("ntlm> Could not write negotiate message to proxy: %s", err)
+			return conn, err
+		}
+		debugf("ntlm> Successfully sent negotiate message to proxy")
+		// NTLM Step 2: Receive Challenge Message
+		br := bufio.NewReader(conn)
+		resp, err := http.ReadResponse(br, connect)
+		if err != nil {
+			debugf("ntlm> Could not read response from proxy: %s", err)
+			return conn, err
+		}
+		_, err = ioutil.ReadAll(resp.Body)
+		if err != nil {
+			debugf("ntlm> Could not read response body from proxy: %s", err)
+			return conn, err
+		}
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusProxyAuthRequired {
+			debugf("ntlm> Expected %d as return status, got: %d", http.StatusProxyAuthRequired, resp.StatusCode)
+			return conn, errors.New(http.StatusText(resp.StatusCode))
+		}
+		challenge := strings.Split(resp.Header.Get("Proxy-Authenticate"), " ")
+		if len(challenge) < 2 {
+			debugf("ntlm> The proxy did not return an NTLM challenge, got: '%s'", resp.Header.Get("Proxy-Authenticate"))
+			return conn, errors.New("no NTLM challenge received")
+		}
+		debugf("ntlm> NTLM challenge: '%s'", challenge[1])
+		challengeMessage, err := base64.StdEncoding.DecodeString(challenge[1])
+		if err != nil {
+			debugf("ntlm> Could not base64 decode the NTLM challenge: %s", err)
+			return conn, err
+		}
+		// NTLM Step 3: Send Authorization Message
+		debugf("ntlm> Processing NTLM challenge with username '%s' and password with length %d", proxyUsername, len(proxyPassword))
+		authenticateMessage, err := ntlmssp.ProcessChallenge(challengeMessage, proxyUsername, proxyPassword)
+		if err != nil {
+			debugf("ntlm> Could not process the NTLM challenge: %s", err)
+			return conn, err
+		}
+		debugf("ntlm> NTLM authorization: '%s'", base64.StdEncoding.EncodeToString(authenticateMessage))
+		header.Set("Proxy-Authorization", fmt.Sprintf("NTLM %s", base64.StdEncoding.EncodeToString(authenticateMessage)))
+		connect = &http.Request{
+			Method: "CONNECT",
+			URL:    &url.URL{Opaque: addr},
+			Host:   addr,
+			Header: header,
+		}
+		if err := connect.Write(conn); err != nil {
+			debugf("ntlm> Could not write authorization to proxy: %s", err)
+			return conn, err
+		}
+		resp, err = http.ReadResponse(br, connect)
+		if err != nil {
+			debugf("ntlm> Could not read response from proxy: %s", err)
+			return conn, err
+		}
+		_, err = ioutil.ReadAll(resp.Body)
+		if err != nil {
+			debugf("ntlm> Could not read response body from proxy: %s", err)
+			return conn, err
+		}
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			debugf("ntlm> Expected %d as return status, got: %d", http.StatusOK, resp.StatusCode)
+			return conn, errors.New(http.StatusText(resp.StatusCode))
+		}
+		// Succussfully authorized with NTLM
+		debugf("ntlm> Successfully injected NTLM to connection")
+		return conn, nil
+	}
+}