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"
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"regexp"
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"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 {
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CookieSeed string
CookieKey string
CookieDomain string
CookieHttpsOnly bool
CookieHttpOnly bool
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CookieExpire time.Duration
Validator func(string) bool
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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
DisplayHtpasswdForm bool
serveMux *http.ServeMux
PassBasicAuth bool
skipAuthRegex []string
compiledRegex []*regexp.Regexp
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}
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func NewOauthProxy(opts *Options, validator func(string) bool) *OauthProxy {
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login, _ := url.Parse("https://accounts.google.com/o/oauth2/auth")
redeem, _ := url.Parse("https://accounts.google.com/o/oauth2/token")
serveMux := http.NewServeMux()
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for _, u := range opts.proxyUrls {
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path := u.Path
u.Path = ""
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log.Printf("mapping path %q => upstream %q", path, u)
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serveMux.Handle(path, httputil.NewSingleHostReverseProxy(u))
}
for _, u := range opts.CompiledRegex {
log.Printf("compiled skip-auth-regex => %q", u)
}
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redirectUrl := opts.redirectUrl
redirectUrl.Path = oauthCallbackPath
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log.Printf("OauthProxy configured for %s", opts.ClientID)
domain := opts.CookieDomain
if domain == "" {
domain = "<default>"
}
log.Printf("Cookie settings: https_only: %v httponly: %v expiry: %s domain:%s", opts.CookieHttpsOnly, opts.CookieHttpOnly, opts.CookieExpire, domain)
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return &OauthProxy{
CookieKey: "_oauthproxy",
CookieSeed: opts.CookieSecret,
CookieDomain: opts.CookieDomain,
CookieHttpsOnly: opts.CookieHttpsOnly,
CookieHttpOnly: opts.CookieHttpOnly,
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CookieExpire: opts.CookieExpire,
Validator: validator,
clientID: opts.ClientID,
clientSecret: opts.ClientSecret,
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oauthScope: "profile email",
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oauthRedemptionUrl: redeem,
oauthLoginUrl: login,
serveMux: serveMux,
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redirectUrl: redirectUrl,
skipAuthRegex: opts.SkipAuthRegex,
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compiledRegex: opts.CompiledRegex,
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PassBasicAuth: opts.PassBasicAuth,
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}
}
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
}
func (p *OauthProxy) displayCustomLoginForm() bool {
return p.HtpasswdFile != nil && p.DisplayHtpasswdForm
}
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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]
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if p.CookieDomain != "" && strings.HasSuffix(domain, p.CookieDomain) {
domain = p.CookieDomain
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}
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: p.CookieHttpOnly,
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}
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)
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if p.CookieDomain != "" && strings.HasSuffix(domain, p.CookieDomain) {
domain = p.CookieDomain
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}
cookie := &http.Cookie{
Name: p.CookieKey,
Value: signedCookieValue(p.CookieSeed, p.CookieKey, val),
Path: "/",
Domain: domain,
HttpOnly: p.CookieHttpOnly,
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Secure: p.CookieHttpsOnly,
Expires: time.Now().Add(p.CookieExpire),
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}
http.SetCookie(rw, cookie)
}
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func (p *OauthProxy) PingPage(rw http.ResponseWriter) {
rw.WriteHeader(http.StatusOK)
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fmt.Fprintf(rw, "OK")
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}
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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
CustomLogin bool
Redirect string
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Version string
}{
SignInMessage: p.SignInMessage,
CustomLogin: p.displayCustomLoginForm(),
Redirect: req.URL.RequestURI(),
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Version: VERSION,
}
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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
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remoteAddr := req.RemoteAddr
if req.Header.Get("X-Real-IP") != "" {
remoteAddr += fmt.Sprintf(" (%q)", req.Header.Get("X-Real-IP"))
}
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log.Printf("%s %s %s", remoteAddr, req.Method, req.URL.RequestURI())
var ok bool
var user string
var email string
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if req.URL.Path == pingPath {
p.PingPage(rw)
return
}
for _, u := range p.compiledRegex {
match := u.MatchString(req.URL.Path)
if match {
p.serveMux.ServeHTTP(rw, req)
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("%s error redeeming code %s", remoteAddr, 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) {
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log.Printf("%s authenticating %s completed", remoteAddr, 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 {
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("%s - invalid cookie session", remoteAddr)
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p.SignInPage(rw, req, 403)
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return
}
// At this point, the user is authenticated. proxy normally
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if p.PassBasicAuth {
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req.SetBasicAuth(user, "")
req.Header["X-Forwarded-User"] = []string{user}
req.Header["X-Forwarded-Email"] = []string{email}
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}
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
}