From 2dfcccd241c915fc1991fd2d4be4665414ff5f9c Mon Sep 17 00:00:00 2001
From: Simon Gottschlag <simon@gottschlag.se>
Date: Wed, 6 Feb 2019 15:49:14 +0100
Subject: [PATCH] Add initial support for ADFS (#5)

---
 handlers/handlers.go   | 73 ++++++++++++++++++++++++++++++++++++++++++
 pkg/cfg/cfg.go         | 10 +++---
 pkg/structs/structs.go | 16 +++++++++
 3 files changed, 95 insertions(+), 4 deletions(-)

diff --git a/handlers/handlers.go b/handlers/handlers.go
index 475a035f..7ccc3a3e 100644
--- a/handlers/handlers.go
+++ b/handlers/handlers.go
@@ -10,6 +10,8 @@ import (
 	"io/ioutil"
 	"mime/multipart"
 	"net/http"
+	"net/url"
+	"strconv"
 	"strings"
 
 	log "github.com/Sirupsen/logrus"
@@ -424,6 +426,8 @@ func getUserInfo(r *http.Request, user *structs.User) error {
 	// indieauth sends the "me" setting in json back to the callback, so just pluck it from the callback
 	if cfg.GenOAuth.Provider == cfg.Providers.IndieAuth {
 		return getUserInfoFromIndieAuth(r, user)
+	} else if cfg.GenOAuth.Provider == cfg.Providers.ADFS {
+		return getUserInfoFromADFS(r, user)
 	}
 
 	providerToken, err := cfg.OAuthClient.Exchange(oauth2.NoContext, r.URL.Query().Get("code"))
@@ -569,6 +573,75 @@ func getUserInfoFromIndieAuth(r *http.Request, user *structs.User) error {
 	return nil
 }
 
+// More info: https://docs.microsoft.com/en-us/windows-server/identity/ad-fs/overview/ad-fs-scenarios-for-developers#supported-scenarios
+func getUserInfoFromADFS(r *http.Request, user *structs.User) error {
+	code := r.URL.Query().Get("code")
+	log.Errorf("code: %s", code)
+
+	formData := url.Values{}
+	formData.Set("code", code)
+	formData.Set("grant_type", "authorization_code")
+	formData.Set("resource", cfg.GenOAuth.RedirectURL)
+	formData.Set("client_id", cfg.GenOAuth.ClientID)
+	formData.Set("redirect_uri", cfg.GenOAuth.RedirectURL)
+	formData.Set("client_secret", cfg.GenOAuth.ClientSecret)
+
+	req, err := http.NewRequest("POST", cfg.GenOAuth.TokenURL, strings.NewReader(formData.Encode()))
+	if err != nil {
+		return err
+	}
+	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Add("Content-Length", strconv.Itoa(len(formData.Encode())))
+	req.Header.Set("Accept", "application/json")
+
+	// v := url.Values{}
+	// userinfo, err := client.PostForm(cfg.GenOAuth.UserInfoURL, v)
+
+	client := &http.Client{}
+	userinfo, err := client.Do(req)
+
+	if err != nil {
+		// http.Error(w, err.Error(), http.StatusBadRequest)
+		return err
+	}
+	defer userinfo.Body.Close()
+
+	body, _ := ioutil.ReadAll(userinfo.Body)
+
+	var tokenRes struct {
+		AccessToken string `json:"access_token"`
+		TokenType   string `json:"token_type"`
+		IDToken     string `json:"id_token"`
+		ExpiresIn   int64  `json:"expires_in"` // relative seconds from now
+	}
+
+	if err := json.Unmarshal(body, &tokenRes); err != nil {
+		log.Errorf("oauth2: cannot fetch token: %v", err)
+		return nil
+	}
+
+	s := strings.Split(tokenRes.IDToken, ".")
+	if len(s) < 2 {
+		log.Error("jws: invalid token received")
+		return nil
+	}
+
+	idToken, err := base64.RawURLEncoding.DecodeString(s[1])
+	if err != nil {
+		log.Error(err)
+		return nil
+	}
+
+	adfsUser := structs.ADFSUser{}
+	json.Unmarshal([]byte(idToken), &adfsUser)
+	log.Println("adfs adfsUser: ", adfsUser)
+
+	adfsUser.PrepareUserData()
+	user.Username = adfsUser.UPN
+	log.Debug(user)
+	return nil
+}
+
 // the standard error
 // this is captured by nginx, which converts the 401 into 302 to the login page
 func error401(w http.ResponseWriter, r *http.Request, ae AuthError) {
diff --git a/pkg/cfg/cfg.go b/pkg/cfg/cfg.go
index b8177053..cbb76b80 100644
--- a/pkg/cfg/cfg.go
+++ b/pkg/cfg/cfg.go
@@ -79,6 +79,7 @@ type OAuthProviders struct {
 	Google    string
 	GitHub    string
 	IndieAuth string
+	ADFS      string
 	OIDC      string
 }
 
@@ -113,6 +114,7 @@ var (
 		Google:    "google",
 		GitHub:    "github",
 		IndieAuth: "indieauth",
+		ADFS:      "adfs",
 		OIDC:      "oidc",
 	}
 
@@ -213,12 +215,12 @@ func Get(key string) string {
 	return viper.GetString(key)
 }
 
-// Get int value for key
+// GetInt int value for key
 func GetInt(key string) int {
 	return viper.GetInt(key)
 }
 
-// Get bool value for key
+// GetBool bool value for key
 func GetBool(key string) bool {
 	return viper.GetBool(key)
 }
@@ -246,8 +248,8 @@ func BasicTest() error {
 	case GenOAuth.Provider != Providers.Google && GenOAuth.AuthURL == "":
 		// everyone except IndieAuth and Google has an authURL
 		return errors.New("configuration error: oauth.auth_url not found")
-	case GenOAuth.Provider != Providers.Google && GenOAuth.Provider != Providers.IndieAuth && GenOAuth.UserInfoURL == "":
-		// everyone except IndieAuth and Google has an userInfoURL
+	case GenOAuth.Provider != Providers.Google && GenOAuth.Provider != Providers.IndieAuth && GenOAuth.Provider != Providers.ADFS && GenOAuth.UserInfoURL == "":
+		// everyone except IndieAuth, Google and ADFS has an userInfoURL
 		return errors.New("configuration error: oauth.user_info_url not found")
 	}
 
diff --git a/pkg/structs/structs.go b/pkg/structs/structs.go
index 62ab2481..af99ff65 100644
--- a/pkg/structs/structs.go
+++ b/pkg/structs/structs.go
@@ -47,6 +47,22 @@ func (u *GoogleUser) PrepareUserData() {
 	u.Username = u.Email
 }
 
+type ADFSUser struct {
+	User
+	Sub string `json:"sub"`
+	UPN string `json:"upn"`
+	// UniqueName string `json:"unique_name"`
+	// PwdExp     string `json:"pwd_exp"`
+	// SID        string `json:"sid"`
+	// Groups     string `json:"groups"`
+	// jwt.StandardClaims
+}
+
+// PrepareUserData implement PersonalData interface
+func (u *ADFSUser) PrepareUserData() {
+	u.Username = u.UPN
+}
+
 // GitHubUser is a retrieved and authentiacted user from GitHub.
 type GitHubUser struct {
 	User