feat: Adds login via twitter

server/handlers/oauth_callback.go

@@ -68,7 +68,7 @@ func OAuthCallbackHandler() gin.HandlerFunc {
 		case constants.AuthRecipeMethodApple:
 			user, err = processAppleUserInfo(code)
 		case constants.AuthRecipeMethodTwitter:
-			user, err = processTwitterUserInfo(code)
+			user, err = processTwitterUserInfo(code, sessionState)
 		default:
 			log.Info("Invalid oauth provider")
 			err = fmt.Errorf(`invalid oauth provider`)
@@ -567,8 +567,69 @@ func processAppleUserInfo(code string) (models.User, error) {
 	return user, err
 }
 
-func processTwitterUserInfo(code string) (models.User, error) {
+func processTwitterUserInfo(code, verifier string) (models.User, error) {
 	user := models.User{}
-	// TODO exchange code and get user information
+	oauth2Token, err := oauth.OAuthProviders.TwitterConfig.Exchange(oauth2.NoContext, code, oauth2.SetAuthURLParam("code_verifier", verifier))
+	if err != nil {
+		log.Debug("Failed to exchange code for token: ", err)
+		return user, fmt.Errorf("invalid twitter exchange code: %s", err.Error())
+	}
+
+	client := http.Client{}
+	req, err := http.NewRequest("GET", constants.TwitterUserInfoURL, nil)
+	if err != nil {
+		log.Debug("Failed to create Twitter user info request: ", err)
+		return user, fmt.Errorf("error creating Twitter user info request: %s", err.Error())
+	}
+	req.Header = http.Header{
+		"Authorization": []string{fmt.Sprintf("Bearer %s", oauth2Token.AccessToken)},
+	}
+
+	response, err := client.Do(req)
+	if err != nil {
+		log.Debug("Failed to request Twitter user info: ", err)
+		return user, err
+	}
+
+	defer response.Body.Close()
+	body, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		log.Debug("Failed to read Twitter user info response body: ", err)
+		return user, fmt.Errorf("failed to read Twitter response body: %s", err.Error())
+	}
+
+	if response.StatusCode >= 400 {
+		log.Debug("Failed to request Twitter user info: ", string(body))
+		return user, fmt.Errorf("failed to request Twitter user info: %s", string(body))
+	}
+
+	responseRawData := make(map[string]interface{})
+	json.Unmarshal(body, &responseRawData)
+
+	userRawData := responseRawData["data"].(map[string]interface{})
+
+	log.Info(userRawData)
+	// Twitter API does not return E-Mail adresses by default. For that case special privileges have
+	// to be granted on a per-App basis. See https://developer.twitter.com/en/docs/twitter-api/v1/accounts-and-users/manage-account-settings/api-reference/get-account-verify_credentials
+
+	// Currently Twitter API only provides the full name of a user. To fill givenName and familyName
+	// the full name will be split at the first whitespace. This approach will not be valid for all name combinations
+	nameArr := strings.SplitAfterN(userRawData["name"].(string), " ", 2)
+
+	firstName := nameArr[0]
+	lastName := ""
+	if len(nameArr) == 2 {
+		lastName = nameArr[1]
+	}
+	nickname := userRawData["username"].(string)
+	profilePicture := userRawData["profile_image_url"].(string)
+
+	user = models.User{
+		GivenName:  &firstName,
+		FamilyName: &lastName,
+		Picture:    &profilePicture,
+		Nickname:   &nickname,
+	}
+
 	return user, nil
 }

server/handlers/oauth_login.go

@@ -12,6 +12,7 @@ import (
 	"github.com/authorizerdev/authorizer/server/memorystore"
 	"github.com/authorizerdev/authorizer/server/oauth"
 	"github.com/authorizerdev/authorizer/server/parsers"
+	"github.com/authorizerdev/authorizer/server/utils"
 	"github.com/authorizerdev/authorizer/server/validators"
 )
 
@@ -175,7 +176,10 @@ func OAuthLoginHandler() gin.HandlerFunc {
 				isProviderConfigured = false
 				break
 			}
-			err := memorystore.Provider.SetState(oauthStateString, constants.AuthRecipeMethodTwitter)
+
+			verifier, challenge := utils.GenerateCodeChallenge()
+
+			err := memorystore.Provider.SetState(oauthStateString, verifier)
 			if err != nil {
 				log.Debug("Error setting state: ", err)
 				c.JSON(500, gin.H{
@@ -184,7 +188,7 @@ func OAuthLoginHandler() gin.HandlerFunc {
 				return
 			}
 			oauth.OAuthProviders.TwitterConfig.RedirectURL = hostname + "/oauth_callback/" + constants.AuthRecipeMethodTwitter
-			url := oauth.OAuthProviders.TwitterConfig.AuthCodeURL(oauthStateString)
+			url := oauth.OAuthProviders.TwitterConfig.AuthCodeURL(oauthStateString, oauth2.SetAuthURLParam("code_challenge", challenge), oauth2.SetAuthURLParam("code_challenge_method", "S256"))
 			c.Redirect(http.StatusTemporaryRedirect, url)
 		case constants.AuthRecipeMethodApple:
 			if oauth.OAuthProviders.AppleConfig == nil {