handlers.go

/*
Copyright 2015 All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net"

	"net/http"
	"net/http/pprof"
	"net/url"
	"path"
	"strings"
	"time"

	"github.com/coreos/go-oidc/oidc"
	"golang.org/x/oauth2"

	"github.com/go-chi/chi"
	"go.uber.org/zap"
)

// getRedirectionURL returns the redirectionURL for the oauth flow
func (r *oauthProxy) getRedirectionURL(w http.ResponseWriter, req *http.Request) string {
	var redirect string
	switch r.config.RedirectionURL {
	case "":
		// need to determine the scheme, cx.Request.URL.Scheme doesn't have it, best way is to default
		// and then check for TLS
		scheme := unsecureScheme
		if req.TLS != nil {
			scheme = secureScheme
		}
		// @QUESTION: should I use the X-Forwarded-<header>?? ..
		redirect = fmt.Sprintf("%s://%s",
			defaultTo(req.Header.Get("X-Forwarded-Proto"), scheme),
			defaultTo(req.Header.Get("X-Forwarded-Host"), req.Host))
	default:
		redirect = r.config.RedirectionURL
	}

	state, _ := req.Cookie(requestStateCookie)
	if state != nil && req.URL.Query().Get("state") != state.Value {
		r.log.Error("state parameter mismatch")
		w.WriteHeader(http.StatusForbidden)
		return ""
	}
	return fmt.Sprintf("%s%s", redirect, r.config.WithOAuthURI("callback"))
}

// oauthAuthorizationHandler is responsible for performing the redirection to oauth provider
func (r *oauthProxy) oauthAuthorizationHandler(w http.ResponseWriter, req *http.Request) {
	if r.config.SkipTokenVerification {
		w.WriteHeader(http.StatusNotAcceptable)
		return
	}
	conf := r.newOAuth2Config(r.getRedirectionURL(w, req))

	// step: set the access type of the session
	accessType := oauth2.AccessTypeOnline
	if containedIn("offline", r.config.Scopes) {
		accessType = oauth2.AccessTypeOffline
	}

	authURL := conf.AuthCodeURL(req.URL.Query().Get("state"), accessType)
	r.log.Debug("incoming authorization request from client address",
		zap.Any("access_type", accessType),
		zap.String("auth_url", authURL),
		zap.String("client_ip", req.RemoteAddr))

	// step: if we have a custom sign in page, lets display that
	if r.config.hasCustomSignInPage() {
		model := make(map[string]string)
		model["redirect"] = authURL
		w.WriteHeader(http.StatusOK)
		_ = r.Render(w, path.Base(r.config.SignInPage), mergeMaps(model, r.config.Tags))

		return
	}

	r.redirectToURL(authURL, w, req, http.StatusSeeOther)
}

// oauthCallbackHandler is responsible for handling the response from oauth service
func (r *oauthProxy) oauthCallbackHandler(w http.ResponseWriter, req *http.Request) {
	if r.config.SkipTokenVerification {
		w.WriteHeader(http.StatusNotAcceptable)
		return
	}
	// step: ensure we have a authorization code
	code := req.URL.Query().Get("code")
	if code == "" {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	conf := r.newOAuth2Config(r.getRedirectionURL(w, req))

	resp, err := exchangeAuthenticationCode(conf, code)
	if err != nil {
		r.log.Error("unable to exchange code for access token", zap.Error(err))
		r.accessForbidden(w, req)
		return
	}

	// Flow: once we exchange the authorization code we parse the ID Token; we then check for an access token,
	// if an access token is present and we can decode it, we use that as the session token, otherwise we default
	// to the ID Token.
	rawIDToken, ok := resp.Extra("id_token").(string)
	if !ok {
		r.log.Error("unable to obtain id token", zap.Error(err))
		r.accessForbidden(w, req)
		return
	}

	token, identity, err := parseToken(rawIDToken)
	if err != nil {
		r.log.Error("unable to parse id token for identity", zap.Error(err))
		r.accessForbidden(w, req)
		return
	}

	access, id, err := parseToken(resp.AccessToken)
	if err == nil {
		token = access
		identity = id
	} else {
		r.log.Warn("unable to parse the access token, using id token only", zap.Error(err))
	}

	// step: check the access token is valid
	if err = verifyToken(r.client, token); err != nil {
		r.log.Error("unable to verify the id token", zap.Error(err))
		r.accessForbidden(w, req)
		return
	}
	accessToken := token.Encode()

	// step: are we encrypting the access token?
	if r.config.EnableEncryptedToken || r.config.ForceEncryptedCookie {
		if accessToken, err = encodeText(accessToken, r.config.EncryptionKey); err != nil {
			r.log.Error("unable to encode the access token", zap.Error(err))
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
	}

	r.log.Info("issuing access token for user",
		zap.String("email", identity.Email),
		zap.String("expires", identity.ExpiresAt.Format(time.RFC3339)),
		zap.String("duration", time.Until(identity.ExpiresAt).String()))

	// @metric a token has been issued
	oauthTokensMetric.WithLabelValues("issued").Inc()

	// step: does the response have a refresh token and we do NOT ignore refresh tokens?
	if r.config.EnableRefreshTokens && resp.RefreshToken != "" {
		var encrypted string
		encrypted, err = encodeText(resp.RefreshToken, r.config.EncryptionKey)
		if err != nil {
			r.log.Error("failed to encrypt the refresh token", zap.Error(err))
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		// drop in the access token - cookie expiration = access token
		r.dropAccessTokenCookie(req, w, accessToken, r.getAccessCookieExpiration(resp.RefreshToken))

		var expiration time.Duration
		// notes: not all idp refresh tokens are readable, google for example, so we attempt to decode into
		// a jwt and if possible extract the expiration, else we default to 10 days
		var ident *oidc.Identity

		if _, ident, err = parseToken(resp.RefreshToken); err != nil {
			expiration = 0
		} else {
			expiration = time.Until(ident.ExpiresAt)
		}

		switch r.useStore() {
		case true:
			if err = r.StoreRefreshToken(token, encrypted, expiration); err != nil {
				r.log.Warn("failed to save the refresh token in the store", zap.Error(err))
			}
		default:
			r.dropRefreshTokenCookie(req, w, encrypted, expiration)
		}
	} else {
		r.dropAccessTokenCookie(req, w, accessToken, time.Until(identity.ExpiresAt))
	}

	// step: decode the request variable
	redirectURI := "/"
	if req.URL.Query().Get("state") != "" {
		if encodedRequestURI, _ := req.Cookie(requestURICookie); encodedRequestURI != nil {
			decoded, _ := base64.StdEncoding.DecodeString(encodedRequestURI.Value)
			redirectURI = string(decoded)
		}
	}

	r.redirectToURL(redirectURI, w, req, http.StatusSeeOther)
}

// loginHandler provide's a generic endpoint for clients to perform a user_credentials login to the provider
func (r *oauthProxy) loginHandler(w http.ResponseWriter, req *http.Request) {
	errorMsg, code, err := func() (string, int, error) {
		ctx := context.Background()

		if !r.config.EnableLoginHandler {
			return "attempt to login when login handler is disabled", http.StatusNotImplemented, errors.New("login handler disabled")
		}
		username := req.PostFormValue("username")
		password := req.PostFormValue("password")
		if username == "" || password == "" {
			return "request does not have both username and password", http.StatusBadRequest, errors.New("no credentials")
		}

		conf := r.newOAuth2Config(r.getRedirectionURL(w, req))

		start := time.Now()
		token, err := conf.PasswordCredentialsToken(ctx, username, password)

		if err != nil {
			if !token.Valid() {
				return "invalid user credentials provided", http.StatusUnauthorized, err
			}
			return "unable to request the access token via grant_type 'password'", http.StatusInternalServerError, err
		}
		// @metric observe the time taken for a login request
		oauthLatencyMetric.WithLabelValues("login").Observe(time.Since(start).Seconds())

		_, identity, err := parseToken(token.AccessToken)
		if err != nil {
			return "unable to decode the access token", http.StatusNotImplemented, err
		}

		r.dropAccessTokenCookie(req, w, token.AccessToken, time.Until(identity.ExpiresAt))

		// @metric a token has been issued
		oauthTokensMetric.WithLabelValues("login").Inc()

		w.Header().Set("Content-Type", "application/json")
		idToken, ok := token.Extra("id_token").(string)
		if !ok {
			return "", http.StatusInternalServerError, fmt.Errorf("token response does not contain an id_token")
		}
		expiresIn, ok := token.Extra("expires_in").(float64)
		if !ok {
			return "", http.StatusInternalServerError, fmt.Errorf("token response does not contain expires_in")
		}
		scope, _ := token.Extra("scope").(string)
		if err := json.NewEncoder(w).Encode(tokenResponse{
			IDToken:      idToken,
			AccessToken:  token.AccessToken,
			RefreshToken: token.RefreshToken,
			ExpiresIn:    expiresIn,
			Scope:        scope,
		}); err != nil {
			return "", http.StatusInternalServerError, err
		}

		return "", http.StatusOK, nil
	}()
	if err != nil {
		r.log.Error(errorMsg,
			zap.String("client_ip", req.RemoteAddr),
			zap.Error(err))

		w.WriteHeader(code)
	}
}

// emptyHandler is responsible for doing nothing
func emptyHandler(w http.ResponseWriter, req *http.Request) {}

// logoutHandler performs a logout
//  - if it's just a access token, the cookie is deleted
//  - if the user has a refresh token, the token is invalidated by the provider
//  - optionally, the user can be redirected by to a url
func (r *oauthProxy) logoutHandler(w http.ResponseWriter, req *http.Request) {
	// @check if the redirection is there
	var redirectURL string
	for k := range req.URL.Query() {
		if k == "redirect" {
			redirectURL = req.URL.Query().Get("redirect")
			if redirectURL == "" {
				// then we can default to redirection url
				redirectURL = strings.TrimSuffix(r.config.RedirectionURL, "/oauth/callback")
			}
		}
	}

	// @step: drop the access token
	user, err := r.getIdentity(req)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	// step: can either use the id token or the refresh token
	identityToken := user.token.Encode()
	//nolint:vetshadow
	if refresh, _, err := r.retrieveRefreshToken(req, user); err == nil {
		identityToken = refresh
	}
	r.clearAllCookies(req, w)

	// @metric increment the logout counter
	oauthTokensMetric.WithLabelValues("logout").Inc()

	// step: check if the user has a state session and if so revoke it
	if r.useStore() {
		go func() {
			if err = r.DeleteRefreshToken(user.token); err != nil {
				r.log.Error("unable to remove the refresh token from store", zap.Error(err))
			}
		}()
	}

	// set the default revocation url
	revokeDefault := ""
	if r.idp.EndSessionEndpoint != nil {
		revokeDefault = r.idp.EndSessionEndpoint.String()
	}
	revocationURL := defaultTo(r.config.RevocationEndpoint, revokeDefault)

	// @check if we should redirect to the provider
	if r.config.EnableLogoutRedirect {
		sendTo := fmt.Sprintf("%s/protocol/openid-connect/logout", strings.TrimSuffix(r.config.DiscoveryURL, "/.well-known/openid-configuration"))

		// @step: if no redirect uri is set
		if redirectURL == "" {
			// @step: we first check for a redirection-url and then host header
			if r.config.RedirectionURL != "" {
				redirectURL = r.config.RedirectionURL
			} else {
				redirectURL = getRequestHostURL(req)
			}
		}

		r.redirectToURL(fmt.Sprintf("%s?redirect_uri=%s", sendTo, url.QueryEscape(redirectURL)), w, req, http.StatusSeeOther)

		return
	}

	// step: do we have a revocation endpoint?
	if revocationURL != "" {
		client := &http.Client{Timeout: 5 * time.Second}
		if err != nil {
			r.log.Error("unable to retrieve the openid client", zap.Error(err))
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		// step: add the authentication headers
		encodedID := url.QueryEscape(r.config.ClientID)
		encodedSecret := url.QueryEscape(r.config.ClientSecret)

		// step: construct the url for revocation
		request, err := http.NewRequest(http.MethodPost, revocationURL, bytes.NewBufferString(fmt.Sprintf("refresh_token=%s", identityToken)))
		if err != nil {
			r.log.Error("unable to construct the revocation request", zap.Error(err))
			w.WriteHeader(http.StatusInternalServerError)
			return
		}

		// step: add the authentication headers and content-type
		request.SetBasicAuth(encodedID, encodedSecret)
		request.Header.Set("Content-Type", "application/x-www-form-urlencoded")

		start := time.Now()
		response, err := client.Do(request)
		if err != nil {
			r.log.Error("unable to post to revocation endpoint", zap.Error(err))
			return
		}
		oauthLatencyMetric.WithLabelValues("revocation").Observe(time.Since(start).Seconds())

		// step: check the response
		switch response.StatusCode {
		case http.StatusNoContent:
			r.log.Info("successfully logged out of the endpoint", zap.String("email", user.email))
		default:
			content, _ := ioutil.ReadAll(response.Body)
			r.log.Error("invalid response from revocation endpoint",
				zap.Int("status", response.StatusCode),
				zap.String("response", fmt.Sprintf("%s", content)))
		}
		defer response.Body.Close()
	}
	// step: should we redirect the user
	if redirectURL != "" {
		r.redirectToURL(redirectURL, w, req, http.StatusSeeOther)
	}
}

// expirationHandler checks if the token has expired
func (r *oauthProxy) expirationHandler(w http.ResponseWriter, req *http.Request) {
	user, err := r.getIdentity(req)
	if err != nil {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	if user.isExpired() {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}
	w.WriteHeader(http.StatusOK)
}

// tokenHandler display access token to screen
func (r *oauthProxy) tokenHandler(w http.ResponseWriter, req *http.Request) {
	user, err := r.getIdentity(req)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_, _ = w.Write(user.token.Payload)
}

// healthHandler is a health check handler for the service
func (r *oauthProxy) healthHandler(w http.ResponseWriter, req *http.Request) {
	w.Header().Set(versionHeader, getVersion())
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte("OK\n"))
}

// debugHandler is responsible for providing the pprof
func (r *oauthProxy) debugHandler(w http.ResponseWriter, req *http.Request) {
	const symbolProfile = "symbol"
	name := chi.URLParam(req, "name")
	switch req.Method {
	case http.MethodGet:
		switch name {
		case "heap":
			fallthrough
		case "goroutine":
			fallthrough
		case "block":
			fallthrough
		case "threadcreate":
			pprof.Handler(name).ServeHTTP(w, req)
		case "cmdline":
			pprof.Cmdline(w, req)
		case "profile":
			pprof.Profile(w, req)
		case "trace":
			pprof.Trace(w, req)
		case symbolProfile:
			pprof.Symbol(w, req)
		default:
			w.WriteHeader(http.StatusNotFound)
		}
	case http.MethodPost:
		switch name {
		case symbolProfile:
			pprof.Symbol(w, req)
		default:
			w.WriteHeader(http.StatusNotFound)
		}
	}
}

// proxyMetricsHandler forwards the request into the prometheus handler
func (r *oauthProxy) proxyMetricsHandler(w http.ResponseWriter, req *http.Request) {
	if r.config.LocalhostMetrics {
		if !net.ParseIP(realIP(req)).IsLoopback() {
			r.accessForbidden(w, req)
			return
		}
	}
	r.metricsHandler.ServeHTTP(w, req)
}

// retrieveRefreshToken retrieves the refresh token from store or cookie
func (r *oauthProxy) retrieveRefreshToken(req *http.Request, user *userContext) (token, encrypted string, err error) {
	switch r.useStore() {
	case true:
		token, err = r.GetRefreshToken(user.token)
	default:
		token, err = r.getRefreshTokenFromCookie(req)
	}
	if err != nil {
		return
	}

	encrypted = token // returns encrypted, avoids encoding twice
	token, err = decodeText(token, r.config.EncryptionKey)
	return
}

func methodNotAllowHandlder(w http.ResponseWriter, req *http.Request) {
	w.WriteHeader(http.StatusMethodNotAllowed)
	_, _ = w.Write(nil)
}