oauth2_proxy/oauthproxy.go

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package main
import (
"bytes"
"encoding/base64"
"errors"
"fmt"
"io/ioutil"
"log"
"net/http"
"net/http/httputil"
"net/url"
"strings"
"time"
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"github.com/bitly/go-simplejson"
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)
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const pingPath = "/ping"
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const signInPath = "/oauth2/sign_in"
const oauthStartPath = "/oauth2/start"
const oauthCallbackPath = "/oauth2/callback"
type OauthProxy struct {
CookieSeed string
CookieKey string
Validator func(string) bool
redirectUrl *url.URL // the url to receive requests at
oauthRedemptionUrl *url.URL // endpoint to redeem the code
oauthLoginUrl *url.URL // to redirect the user to
oauthScope string
clientID string
clientSecret string
SignInMessage string
HtpasswdFile *HtpasswdFile
serveMux *http.ServeMux
}
func NewOauthProxy(proxyUrls []*url.URL, clientID string, clientSecret string, validator func(string) bool) *OauthProxy {
login, _ := url.Parse("https://accounts.google.com/o/oauth2/auth")
redeem, _ := url.Parse("https://accounts.google.com/o/oauth2/token")
serveMux := http.NewServeMux()
for _, u := range proxyUrls {
path := u.Path
u.Path = ""
log.Printf("mapping %s => %s", path, u)
serveMux.Handle(path, httputil.NewSingleHostReverseProxy(u))
}
return &OauthProxy{
CookieKey: "_oauthproxy",
CookieSeed: *cookieSecret,
Validator: validator,
clientID: clientID,
clientSecret: clientSecret,
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oauthScope: "profile email",
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oauthRedemptionUrl: redeem,
oauthLoginUrl: login,
serveMux: serveMux,
}
}
func (p *OauthProxy) SetRedirectUrl(redirectUrl *url.URL) {
redirectUrl.Path = oauthCallbackPath
p.redirectUrl = redirectUrl
}
func (p *OauthProxy) GetLoginURL(redirectUrl string) string {
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params := url.Values{}
params.Add("redirect_uri", p.redirectUrl.String())
params.Add("approval_prompt", "force")
params.Add("scope", p.oauthScope)
params.Add("client_id", p.clientID)
params.Add("response_type", "code")
if strings.HasPrefix(redirectUrl, "/") {
params.Add("state", redirectUrl)
}
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return fmt.Sprintf("%s?%s", p.oauthLoginUrl, params.Encode())
}
func apiRequest(req *http.Request) (*simplejson.Json, error) {
httpclient := &http.Client{}
resp, err := httpclient.Do(req)
if err != nil {
return nil, err
}
body, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
return nil, err
}
if resp.StatusCode != 200 {
log.Printf("got response code %d - %s", resp.StatusCode, body)
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return nil, errors.New("api request returned non 200 status code")
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}
data, err := simplejson.NewJson(body)
if err != nil {
return nil, err
}
return data, nil
}
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func (p *OauthProxy) redeemCode(code string) (string, string, error) {
if code == "" {
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return "", "", errors.New("missing code")
}
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params := url.Values{}
params.Add("redirect_uri", p.redirectUrl.String())
params.Add("client_id", p.clientID)
params.Add("client_secret", p.clientSecret)
params.Add("code", code)
params.Add("grant_type", "authorization_code")
req, err := http.NewRequest("POST", p.oauthRedemptionUrl.String(), bytes.NewBufferString(params.Encode()))
if err != nil {
log.Printf("failed building request %s", err.Error())
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return "", "", err
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}
req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
json, err := apiRequest(req)
if err != nil {
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log.Printf("failed making request %s", err)
return "", "", err
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}
access_token, err := json.Get("access_token").String()
if err != nil {
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return "", "", err
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}
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idToken, err := json.Get("id_token").String()
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if err != nil {
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return "", "", err
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}
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// id_token is a base64 encode ID token payload
// https://developers.google.com/accounts/docs/OAuth2Login#obtainuserinfo
jwt := strings.Split(idToken, ".")
b, err := jwtDecodeSegment(jwt[1])
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if err != nil {
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return "", "", err
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}
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data, err := simplejson.NewJson(b)
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if err != nil {
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return "", "", err
}
email, err := data.Get("email").String()
if err != nil {
return "", "", err
}
return access_token, email, nil
}
func jwtDecodeSegment(seg string) ([]byte, error) {
if l := len(seg) % 4; l > 0 {
seg += strings.Repeat("=", 4-l)
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}
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return base64.URLEncoding.DecodeString(seg)
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}
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func (p *OauthProxy) ClearCookie(rw http.ResponseWriter, req *http.Request) {
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domain := strings.Split(req.Host, ":")[0]
if *cookieDomain != "" && strings.HasSuffix(domain, *cookieDomain) {
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domain = *cookieDomain
}
cookie := &http.Cookie{
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Name: p.CookieKey,
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Value: "",
Path: "/",
Domain: domain,
Expires: time.Now().Add(time.Duration(1) * time.Hour * -1),
HttpOnly: true,
}
http.SetCookie(rw, cookie)
}
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func (p *OauthProxy) SetCookie(rw http.ResponseWriter, req *http.Request, val string) {
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domain := strings.Split(req.Host, ":")[0] // strip the port (if any)
if *cookieDomain != "" && strings.HasSuffix(domain, *cookieDomain) {
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domain = *cookieDomain
}
cookie := &http.Cookie{
Name: p.CookieKey,
Value: signedCookieValue(p.CookieSeed, p.CookieKey, val),
Path: "/",
Domain: domain,
Expires: time.Now().Add(time.Duration(168) * time.Hour), // 7 days
HttpOnly: true,
// Secure: req. ... ? set if X-Scheme: https ?
}
http.SetCookie(rw, cookie)
}
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func (p *OauthProxy) PingPage(rw http.ResponseWriter) {
rw.WriteHeader(http.StatusOK)
fmt.Fprintf(rw, "pong")
}
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func (p *OauthProxy) ErrorPage(rw http.ResponseWriter, code int, title string, message string) {
log.Printf("ErrorPage %d %s %s", code, title, message)
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rw.WriteHeader(code)
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templates := getTemplates()
t := struct {
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Title string
Message string
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}{
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Title: fmt.Sprintf("%d %s", code, title),
Message: message,
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}
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templates.ExecuteTemplate(rw, "error.html", t)
}
func (p *OauthProxy) SignInPage(rw http.ResponseWriter, req *http.Request, code int) {
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p.ClearCookie(rw, req)
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rw.WriteHeader(code)
templates := getTemplates()
t := struct {
SignInMessage string
Htpasswd bool
Redirect string
}{
SignInMessage: p.SignInMessage,
Htpasswd: p.HtpasswdFile != nil,
Redirect: req.URL.RequestURI(),
}
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templates.ExecuteTemplate(rw, "sign_in.html", t)
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}
func (p *OauthProxy) ManualSignIn(rw http.ResponseWriter, req *http.Request) (string, bool) {
if req.Method != "POST" || p.HtpasswdFile == nil {
return "", false
}
user := req.FormValue("username")
passwd := req.FormValue("password")
if user == "" {
return "", false
}
// check auth
if p.HtpasswdFile.Validate(user, passwd) {
log.Printf("authenticated %s via manual sign in", user)
return user, true
}
return "", false
}
func (p *OauthProxy) GetRedirect(req *http.Request) (string, error) {
err := req.ParseForm()
if err != nil {
return "", err
}
redirect := req.FormValue("rd")
if redirect == "" {
redirect = "/"
}
return redirect, err
}
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func (p *OauthProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
// check if this is a redirect back at the end of oauth
remoteIP := req.Header.Get("X-Real-IP")
if remoteIP == "" {
remoteIP = req.RemoteAddr
}
log.Printf("%s %s %s", remoteIP, req.Method, req.URL.Path)
var ok bool
var user string
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if req.URL.Path == pingPath {
p.PingPage(rw)
return
}
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if req.URL.Path == signInPath {
redirect, err := p.GetRedirect(req)
if err != nil {
p.ErrorPage(rw, 500, "Internal Error", err.Error())
return
}
user, ok = p.ManualSignIn(rw, req)
if ok {
p.SetCookie(rw, req, user)
http.Redirect(rw, req, redirect, 302)
} else {
p.SignInPage(rw, req, 200)
}
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return
}
if req.URL.Path == oauthStartPath {
redirect, err := p.GetRedirect(req)
if err != nil {
p.ErrorPage(rw, 500, "Internal Error", err.Error())
return
}
http.Redirect(rw, req, p.GetLoginURL(redirect), 302)
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return
}
if req.URL.Path == oauthCallbackPath {
// finish the oauth cycle
err := req.ParseForm()
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if err != nil {
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p.ErrorPage(rw, 500, "Internal Error", err.Error())
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return
}
errorString := req.Form.Get("error")
if errorString != "" {
p.ErrorPage(rw, 403, "Permission Denied", errorString)
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return
}
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_, email, err := p.redeemCode(req.Form.Get("code"))
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if err != nil {
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log.Printf("error redeeming code %s", err)
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p.ErrorPage(rw, 500, "Internal Error", err.Error())
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return
}
redirect := req.Form.Get("state")
if redirect == "" {
redirect = "/"
}
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// set cookie, or deny
if p.Validator(email) {
log.Printf("authenticating %s completed", email)
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p.SetCookie(rw, req, email)
http.Redirect(rw, req, redirect, 302)
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return
} else {
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p.ErrorPage(rw, 403, "Permission Denied", "Invalid Account")
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return
}
}
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if !ok {
cookie, err := req.Cookie(p.CookieKey)
if err == nil {
var email string
email, ok = validateCookie(cookie, p.CookieSeed)
user = strings.Split(email, "@")[0]
}
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}
if !ok {
user, ok = p.CheckBasicAuth(req)
// if we want to promote basic auth requests to cookie'd requests, we could do that here
// not sure that would be ideal in all circumstances though
// if ok {
// p.SetCookie(rw, req, user)
// }
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}
if !ok {
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log.Printf("invalid cookie")
p.SignInPage(rw, req, 403)
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return
}
// At this point, the user is authenticated. proxy normally
if *passBasicAuth {
req.SetBasicAuth(user, "")
req.Header["X-Forwarded-User"] = []string{user}
}
p.serveMux.ServeHTTP(rw, req)
}
func (p *OauthProxy) CheckBasicAuth(req *http.Request) (string, bool) {
if p.HtpasswdFile == nil {
return "", false
}
s := strings.SplitN(req.Header.Get("Authorization"), " ", 2)
if len(s) != 2 || s[0] != "Basic" {
return "", false
}
b, err := base64.StdEncoding.DecodeString(s[1])
if err != nil {
return "", false
}
pair := strings.SplitN(string(b), ":", 2)
if len(pair) != 2 {
return "", false
}
if p.HtpasswdFile.Validate(pair[0], pair[1]) {
log.Printf("authenticated %s via basic auth", pair[0])
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return pair[0], true
}
return "", false
}