google: Make state configurable in DefaultAuthorizationHandler

google/authhandler.go

@@ -6,18 +6,33 @@ package google
 
 import (
 	"fmt"
+
+	"github.com/google/uuid"
 )
 
-const DefaultState = "state"
+// RandomAuthorizationState generates a state via UUID generator.
+func RandomAuthorizationState() string {
+	return uuid.New().String()
+}
 
-// DefaultAuthorizationHandler is a commandline-based auth handler
+// DefaultAuthorizationHandler returns a command line auth handler
 // that prints the auth URL on the console and prompts the user to
 // authorize in the browser and paste the auth code back via stdin.
-// When using this auth handler, DefaultState must be used.
-func DefaultAuthorizationHandler(authCodeUrl string) (string, string, error) {
-	fmt.Printf("Go to the following link in your browser:\n\n   %s\n\n", authCodeUrl)
-	fmt.Println("Enter verification code: ")
+//
+// For convenience, this handler returns a pre-configured state
+// instead of asking the user to additionally paste the state from
+// the auth response. In order for this to work, the state
+// configured here should match the one in the oauth2 AuthTokenURL.
+func DefaultAuthorizationHandler(state string) AuthorizationHandler {
+	return func(authCodeURL string) (string, string, error) {
+		return defaultAuthorizationHandlerHelper(state, authCodeURL)
+	}
+}
+
+func defaultAuthorizationHandlerHelper(state string, authCodeURL string) (string, string, error) {
+	fmt.Printf("Go to the following link in your browser:\n\n   %s\n\n", authCodeURL)
+	fmt.Println("Enter authorization code: ")
 	var code string
 	fmt.Scanln(&code)
-	return code, DefaultState, nil
+	return code, state, nil
 }

google/google.go

@@ -220,13 +220,13 @@ type AuthorizationHandler func(string) (string, string, error)
 // An environment-specific AuthorizationHandler is used to obtain user consent.
 // Per OAuth protocol, a unique "state" string should be sent and verified
 // before token exchange to prevent CSRF attacks.
-func OAuthClientTokenSource(config oauth2.Config, ctx context.Context, authHandler AuthorizationHandler, state string) oauth2.TokenSource {
+func OAuthClientTokenSource(ctx context.Context, config *oauth2.Config, authHandler AuthorizationHandler, state string) oauth2.TokenSource {
 	return oauth2.ReuseTokenSource(nil, oauthClientSource{config: config, ctx: ctx, authHandler: authHandler, state: state})
 }
 
 type oauthClientSource struct {
-	config      oauth2.Config
 	ctx         context.Context
+	config      *oauth2.Config
 	authHandler AuthorizationHandler
 	state       string
 }