Add HOSTED_DOMAIN

README.md

@@ -12,6 +12,7 @@ as the Identity Provider.
 export CALLBACK_URL
 export CLIENT_ID
 export CLIENT_SECRET
+export HOSTED_DOMAIN
 ```
 
 ## License

main.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"strings"
 
 	"github.com/utilitywarehouse/go-operational/op"
 )
@@ -17,6 +18,7 @@ var (
 	clientID     = os.Getenv("CLIENT_ID")
 	clientSecret = os.Getenv("CLIENT_SECRET")
 	callbackURL  = os.Getenv("CALLBACK_URL")
+	expectedHostedDomain = os.Getenv("HOSTED_DOMAIN")
 )
 
 const oauthURL = "https://accounts.google.com/o/oauth2/auth?redirect_uri=%s&response_type=code&client_id=%s&scope=openid+email+profile&approval_prompt=force&access_type=offline"
@@ -34,6 +36,10 @@ type UserInfo struct {
 	Email string `json:"email"`
 }
 
+type HostedDomain struct {
+	HostedDomain string `json:"hd"`
+}
+
 type TokenResponse struct {
 	AccessToken  string `json:"access_token"`
 	RefreshToken string `json:"refresh_token"`
@@ -99,6 +105,34 @@ func getUserEmail(accessToken string) (string, error) {
 	return ui.Email, nil
 }
 
+func getHostedDomain(accessToken string) (string, error) {
+	uri, _ := url.Parse(userInfoURL)
+	q := uri.Query()
+	q.Set("alt", "json")
+	q.Set("access_token", accessToken)
+	uri.RawQuery = q.Encode()
+	resp, err := http.Get(uri.String())
+	if err != nil {
+		return "", err
+	}
+	defer func() {
+		io.Copy(ioutil.Discard, resp.Body)
+		resp.Body.Close()
+	}()
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("Got: %d calling %s", resp.StatusCode, tokenURL)
+	}
+	if err != nil {
+		return "", err
+	}
+	hd := &HostedDomain{}
+	err = json.NewDecoder(resp.Body).Decode(hd)
+	if err != nil {
+		return "", err
+	}
+	return hd.HostedDomain, nil
+}
+
 func googleRedirect() http.Handler {
 	redirectURL := fmt.Sprintf(oauthURL, callbackURL, clientID)
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -122,6 +156,18 @@ func googleCallback() http.Handler {
 			w.WriteHeader(http.StatusInternalServerError)
 		}
 
+		hostedDomain, err := getHostedDomain(tokResponse.AccessToken)
+		if err != nil {
+			log.Printf("Error getting user hosted domain: %s\n", err)
+			w.WriteHeader(http.StatusInternalServerError)
+		}
+
+		if ! strings.EqualFold(hostedDomain, expectedHostedDomain) {
+			log.Printf("Error hosted domain does not match (was %s instead of %s)\n", hostedDomain, expectedHostedDomain)
+			http.Error(w, "Forbidden", 403)
+			return
+		}
+
 		kubectlCMD := fmt.Sprintf(kubectlCMDTemplate, email, clientID, clientSecret, tokResponse.IdToken, idpIssuerURL, tokResponse.RefreshToken)
 
 		w.WriteHeader(http.StatusOK)