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authentik/outpost/pkg/proxy/proxy.go

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package proxy
import (
b64 "encoding/base64"
"encoding/json"
"errors"
"fmt"
"html/template"
"net/http"
"net/url"
"regexp"
"strings"
"time"
"github.com/coreos/go-oidc"
"github.com/justinas/alice"
ipapi "github.com/oauth2-proxy/oauth2-proxy/pkg/apis/ip"
"github.com/oauth2-proxy/oauth2-proxy/pkg/apis/options"
sessionsapi "github.com/oauth2-proxy/oauth2-proxy/pkg/apis/sessions"
"github.com/oauth2-proxy/oauth2-proxy/pkg/middleware"
"github.com/oauth2-proxy/oauth2-proxy/pkg/sessions"
"github.com/oauth2-proxy/oauth2-proxy/pkg/upstream"
"github.com/oauth2-proxy/oauth2-proxy/providers"
"goauthentik.io/outpost/pkg/models"
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log "github.com/sirupsen/logrus"
)
const (
httpScheme = "http"
httpsScheme = "https"
applicationJSON = "application/json"
)
var (
// ErrNeedsLogin means the user should be redirected to the login page
ErrNeedsLogin = errors.New("redirect to login page")
// Used to check final redirects are not susceptible to open redirects.
// Matches //, /\ and both of these with whitespace in between (eg / / or / \).
invalidRedirectRegex = regexp.MustCompile(`[/\\](?:[\s\v]*|\.{1,2})[/\\]`)
)
// OAuthProxy is the main authentication proxy
type OAuthProxy struct {
CookieSeed string
CookieName string
CSRFCookieName string
CookieDomains []string
CookiePath string
CookieSecure bool
CookieHTTPOnly bool
CookieExpire time.Duration
CookieRefresh time.Duration
CookieSameSite string
RobotsPath string
SignInPath string
SignOutPath string
OAuthStartPath string
OAuthCallbackPath string
AuthOnlyPath string
UserInfoPath string
redirectURL *url.URL // the url to receive requests at
whitelistDomains []string
provider providers.Provider
sessionStore sessionsapi.SessionStore
ProxyPrefix string
serveMux http.Handler
SetXAuthRequest bool
SetBasicAuth bool
PassUserHeaders bool
BasicAuthUserAttribute string
BasicAuthPasswordAttribute string
PassAccessToken bool
SetAuthorization bool
PassAuthorization bool
PreferEmailToUser bool
skipAuthRegex []string
skipAuthPreflight bool
skipAuthStripHeaders bool
mainJwtBearerVerifier *oidc.IDTokenVerifier
extraJwtBearerVerifiers []*oidc.IDTokenVerifier
compiledRegex []*regexp.Regexp
templates *template.Template
realClientIPParser ipapi.RealClientIPParser
sessionChain alice.Chain
logger *log.Entry
}
// NewOAuthProxy creates a new instance of OAuthProxy from the options provided
func NewOAuthProxy(opts *options.Options, provider *models.ProxyOutpostConfig) (*OAuthProxy, error) {
logger := log.WithField("logger", "authentik.outpost.proxy").WithField("provider", provider.Name)
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sessionStore, err := sessions.NewSessionStore(&opts.Session, &opts.Cookie)
if err != nil {
return nil, fmt.Errorf("error initialising session store: %v", err)
}
templates := getTemplates()
proxyErrorHandler := upstream.NewProxyErrorHandler(templates.Lookup("error.html"), opts.ProxyPrefix)
upstreamProxy, err := upstream.NewProxy(opts.UpstreamServers, opts.GetSignatureData(), proxyErrorHandler)
if err != nil {
return nil, fmt.Errorf("error initialising upstream proxy: %v", err)
}
for _, u := range opts.GetCompiledRegex() {
logger.Printf("compiled skip-auth-regex => %q", u)
}
redirectURL := opts.GetRedirectURL()
if redirectURL.Path == "" {
redirectURL.Path = fmt.Sprintf("%s/callback", opts.ProxyPrefix)
}
logger.Printf("proxy instance configured for Client ID: %s", opts.ClientID)
sessionChain := buildSessionChain(opts, sessionStore)
return &OAuthProxy{
CookieName: opts.Cookie.Name,
CSRFCookieName: fmt.Sprintf("%v_%v", opts.Cookie.Name, "csrf"),
CookieSeed: opts.Cookie.Secret,
CookieDomains: opts.Cookie.Domains,
CookiePath: opts.Cookie.Path,
CookieSecure: opts.Cookie.Secure,
CookieHTTPOnly: opts.Cookie.HTTPOnly,
CookieExpire: opts.Cookie.Expire,
CookieRefresh: opts.Cookie.Refresh,
CookieSameSite: opts.Cookie.SameSite,
RobotsPath: "/robots.txt",
SignInPath: fmt.Sprintf("%s/sign_in", opts.ProxyPrefix),
SignOutPath: fmt.Sprintf("%s/sign_out", opts.ProxyPrefix),
OAuthStartPath: fmt.Sprintf("%s/start", opts.ProxyPrefix),
OAuthCallbackPath: fmt.Sprintf("%s/callback", opts.ProxyPrefix),
AuthOnlyPath: fmt.Sprintf("%s/auth", opts.ProxyPrefix),
UserInfoPath: fmt.Sprintf("%s/userinfo", opts.ProxyPrefix),
ProxyPrefix: opts.ProxyPrefix,
provider: opts.GetProvider(),
sessionStore: sessionStore,
serveMux: upstreamProxy,
redirectURL: redirectURL,
whitelistDomains: opts.WhitelistDomains,
skipAuthRegex: opts.SkipAuthRegex,
skipAuthPreflight: opts.SkipAuthPreflight,
skipAuthStripHeaders: opts.SkipAuthStripHeaders,
mainJwtBearerVerifier: opts.GetOIDCVerifier(),
extraJwtBearerVerifiers: opts.GetJWTBearerVerifiers(),
compiledRegex: opts.GetCompiledRegex(),
realClientIPParser: opts.GetRealClientIPParser(),
SetXAuthRequest: opts.SetXAuthRequest,
SetBasicAuth: opts.SetBasicAuth,
PassUserHeaders: opts.PassUserHeaders,
PassAccessToken: opts.PassAccessToken,
SetAuthorization: opts.SetAuthorization,
PassAuthorization: opts.PassAuthorization,
PreferEmailToUser: opts.PreferEmailToUser,
templates: templates,
sessionChain: sessionChain,
logger: logger,
}, nil
}
func buildSessionChain(opts *options.Options, sessionStore sessionsapi.SessionStore) alice.Chain {
chain := alice.New(middleware.NewScope())
chain = chain.Append(middleware.NewStoredSessionLoader(&middleware.StoredSessionLoaderOptions{
SessionStore: sessionStore,
RefreshPeriod: opts.Cookie.Refresh,
RefreshSessionIfNeeded: opts.GetProvider().RefreshSessionIfNeeded,
ValidateSessionState: opts.GetProvider().ValidateSessionState,
}))
return chain
}
// RobotsTxt disallows scraping pages from the OAuthProxy
func (p *OAuthProxy) RobotsTxt(rw http.ResponseWriter) {
_, err := fmt.Fprintf(rw, "User-agent: *\nDisallow: /")
if err != nil {
p.logger.Printf("Error writing robots.txt: %v", err)
p.ErrorPage(rw, http.StatusInternalServerError, "Internal Server Error", err.Error())
return
}
rw.WriteHeader(http.StatusOK)
}
// ErrorPage writes an error response
func (p *OAuthProxy) ErrorPage(rw http.ResponseWriter, code int, title string, message string) {
rw.WriteHeader(code)
t := struct {
Title string
Message string
ProxyPrefix string
}{
Title: fmt.Sprintf("%d %s", code, title),
Message: message,
ProxyPrefix: p.ProxyPrefix,
}
err := p.templates.ExecuteTemplate(rw, "error.html", t)
if err != nil {
p.logger.Printf("Error rendering error.html template: %v", err)
http.Error(rw, "Internal Server Error", http.StatusInternalServerError)
}
}
// splitHostPort separates host and port. If the port is not valid, it returns
// the entire input as host, and it doesn't check the validity of the host.
// Unlike net.SplitHostPort, but per RFC 3986, it requires ports to be numeric.
// *** taken from net/url, modified validOptionalPort() to accept ":*"
func splitHostPort(hostport string) (host, port string) {
host = hostport
colon := strings.LastIndexByte(host, ':')
if colon != -1 && validOptionalPort(host[colon:]) {
host, port = host[:colon], host[colon+1:]
}
if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
host = host[1 : len(host)-1]
}
return
}
// validOptionalPort reports whether port is either an empty string
// or matches /^:\d*$/
// *** taken from net/url, modified to accept ":*"
func validOptionalPort(port string) bool {
if port == "" || port == ":*" {
return true
}
if port[0] != ':' {
return false
}
for _, b := range port[1:] {
if b < '0' || b > '9' {
return false
}
}
return true
}
// See https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching?hl=en
var noCacheHeaders = map[string]string{
"Expires": time.Unix(0, 0).Format(time.RFC1123),
"Cache-Control": "no-cache, no-store, must-revalidate, max-age=0",
"X-Accel-Expires": "0", // https://www.nginx.com/resources/wiki/start/topics/examples/x-accel/
}
// prepareNoCache prepares headers for preventing browser caching.
func prepareNoCache(w http.ResponseWriter) {
// Set NoCache headers
for k, v := range noCacheHeaders {
w.Header().Set(k, v)
}
}
func (p *OAuthProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
if req.URL.Path != p.AuthOnlyPath && strings.HasPrefix(req.URL.Path, p.ProxyPrefix) {
prepareNoCache(rw)
}
switch path := req.URL.Path; {
case path == p.RobotsPath:
p.RobotsTxt(rw)
case p.IsWhitelistedRequest(req):
p.SkipAuthProxy(rw, req)
case path == p.SignInPath:
p.OAuthStart(rw, req)
case path == p.SignOutPath:
p.SignOut(rw, req)
case path == p.OAuthStartPath:
p.OAuthStart(rw, req)
case path == p.OAuthCallbackPath:
p.OAuthCallback(rw, req)
case path == p.AuthOnlyPath:
p.AuthenticateOnly(rw, req)
case path == p.UserInfoPath:
p.UserInfo(rw, req)
default:
p.Proxy(rw, req)
}
}
//UserInfo endpoint outputs session email and preferred username in JSON format
func (p *OAuthProxy) UserInfo(rw http.ResponseWriter, req *http.Request) {
session, err := p.getAuthenticatedSession(rw, req)
if err != nil {
http.Error(rw, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
return
}
userInfo := struct {
Email string `json:"email"`
PreferredUsername string `json:"preferredUsername,omitempty"`
}{
Email: session.Email,
PreferredUsername: session.PreferredUsername,
}
rw.Header().Set("Content-Type", "application/json")
rw.WriteHeader(http.StatusOK)
err = json.NewEncoder(rw).Encode(userInfo)
if err != nil {
p.logger.Printf("Error encoding user info: %v", err)
p.ErrorPage(rw, http.StatusInternalServerError, "Internal Server Error", err.Error())
}
}
// SignOut sends a response to clear the authentication cookie
func (p *OAuthProxy) SignOut(rw http.ResponseWriter, req *http.Request) {
redirect, err := p.GetRedirect(req)
if err != nil {
p.logger.Errorf("Error obtaining redirect: %v", err)
p.ErrorPage(rw, http.StatusInternalServerError, "Internal Server Error", err.Error())
return
}
err = p.ClearSessionCookie(rw, req)
if err != nil {
p.logger.Errorf("Error clearing session cookie: %v", err)
p.ErrorPage(rw, http.StatusInternalServerError, "Internal Server Error", err.Error())
return
}
http.Redirect(rw, req, redirect, http.StatusFound)
}
// AuthenticateOnly checks whether the user is currently logged in
func (p *OAuthProxy) AuthenticateOnly(rw http.ResponseWriter, req *http.Request) {
session, err := p.getAuthenticatedSession(rw, req)
if err != nil {
http.Error(rw, "unauthorized request", http.StatusUnauthorized)
return
}
// we are authenticated
p.addHeadersForProxying(rw, req, session)
rw.WriteHeader(http.StatusAccepted)
}
// SkipAuthProxy proxies whitelisted requests and skips authentication
func (p *OAuthProxy) SkipAuthProxy(rw http.ResponseWriter, req *http.Request) {
if p.skipAuthStripHeaders {
p.stripAuthHeaders(req)
}
p.serveMux.ServeHTTP(rw, req)
}
// Proxy proxies the user request if the user is authenticated else it prompts
// them to authenticate
func (p *OAuthProxy) Proxy(rw http.ResponseWriter, req *http.Request) {
session, err := p.getAuthenticatedSession(rw, req)
switch err {
case nil:
// we are authenticated
p.addHeadersForProxying(rw, req, session)
p.serveMux.ServeHTTP(rw, req)
case ErrNeedsLogin:
// we need to send the user to a login screen
if isAjax(req) {
// no point redirecting an AJAX request
p.ErrorJSON(rw, http.StatusUnauthorized)
return
}
p.OAuthStart(rw, req)
default:
// unknown error
p.logger.Errorf("Unexpected internal error: %v", err)
p.ErrorPage(rw, http.StatusInternalServerError,
"Internal Error", "Internal Error")
}
}
// getAuthenticatedSession checks whether a user is authenticated and returns a session object and nil error if so
// Returns nil, ErrNeedsLogin if user needs to login.
// Set-Cookie headers may be set on the response as a side-effect of calling this method.
func (p *OAuthProxy) getAuthenticatedSession(rw http.ResponseWriter, req *http.Request) (*sessionsapi.SessionState, error) {
var session *sessionsapi.SessionState
getSession := p.sessionChain.Then(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
session = middleware.GetRequestScope(req).Session
}))
getSession.ServeHTTP(rw, req)
if session == nil {
return nil, ErrNeedsLogin
}
return session, nil
}
// addHeadersForProxying adds the appropriate headers the request / response for proxying
func (p *OAuthProxy) addHeadersForProxying(rw http.ResponseWriter, req *http.Request, session *sessionsapi.SessionState) {
req.Header["X-Forwarded-User"] = []string{session.User}
if session.Email != "" {
req.Header["X-Forwarded-Email"] = []string{session.Email}
}
if session.PreferredUsername != "" {
req.Header["X-Forwarded-Preferred-Username"] = []string{session.PreferredUsername}
req.Header["X-Auth-Username"] = []string{session.PreferredUsername}
} else {
req.Header.Del("X-Forwarded-Preferred-Username")
req.Header.Del("X-Auth-Username")
}
claims := Claims{}
err := claims.FromIDToken(session.IDToken)
if err != nil {
log.WithError(err).Warning("Failed to parse IDToken")
}
userAttributes := claims.Proxy.UserAttributes
// Attempt to set basic auth based on user's attributes
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if p.SetBasicAuth {
var ok bool
var password string
if password, ok = userAttributes[p.BasicAuthPasswordAttribute].(string); !ok {
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password = ""
}
// Check if we should use email or a custom attribute as username
var username string
if username, ok = userAttributes[p.BasicAuthUserAttribute].(string); !ok {
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username = session.Email
}
authVal := b64.StdEncoding.EncodeToString([]byte(username + ":" + password))
req.Header["Authorization"] = []string{fmt.Sprintf("Basic %s", authVal)}
}
rw.Header().Set("GAP-Auth", session.PreferredUsername)
// Check if user has additional headers set that we should sent
if additionalHeaders, ok := userAttributes["additionalHeaders"].(map[string]string); ok {
if additionalHeaders == nil {
return
}
for key, value := range additionalHeaders {
req.Header.Set(key, value)
}
}
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}
// stripAuthHeaders removes Auth headers for whitelisted routes from skipAuthRegex
func (p *OAuthProxy) stripAuthHeaders(req *http.Request) {
if p.PassUserHeaders {
req.Header.Del("X-Forwarded-User")
req.Header.Del("X-Forwarded-Email")
req.Header.Del("X-Forwarded-Preferred-Username")
}
if p.PassAccessToken {
req.Header.Del("X-Forwarded-Access-Token")
}
if p.PassAuthorization {
req.Header.Del("Authorization")
}
}
// isAjax checks if a request is an ajax request
func isAjax(req *http.Request) bool {
acceptValues := req.Header.Values("Accept")
const ajaxReq = applicationJSON
for _, v := range acceptValues {
if v == ajaxReq {
return true
}
}
return false
}
// ErrorJSON returns the error code with an application/json mime type
func (p *OAuthProxy) ErrorJSON(rw http.ResponseWriter, code int) {
rw.Header().Set("Content-Type", applicationJSON)
rw.WriteHeader(code)
}