diff --git a/weed/iam/sts/sts_service.go b/weed/iam/sts/sts_service.go
index d706c50f2..213177ef2 100644
--- a/weed/iam/sts/sts_service.go
+++ b/weed/iam/sts/sts_service.go
@@ -10,10 +10,11 @@ import (
 
 // STSService provides Security Token Service functionality
 type STSService struct {
-	config       *STSConfig
-	initialized  bool
-	providers    map[string]providers.IdentityProvider
-	sessionStore SessionStore
+	config         *STSConfig
+	initialized    bool
+	providers      map[string]providers.IdentityProvider
+	sessionStore   SessionStore
+	tokenGenerator *TokenGenerator
 }
 
 // STSConfig holds STS service configuration
@@ -181,6 +182,9 @@ func (s *STSService) Initialize(config *STSConfig) error {
 	}
 	s.sessionStore = sessionStore
 
+	// Initialize token generator for JWT validation
+	s.tokenGenerator = NewTokenGenerator(config.SigningKey, config.Issuer)
+
 	s.initialized = true
 	return nil
 }
@@ -280,6 +284,13 @@ func (s *STSService) AssumeRoleWithWebIdentity(ctx context.Context, request *Ass
 		return nil, fmt.Errorf("failed to generate credentials: %w", err)
 	}
 
+	// Generate proper JWT session token using our TokenGenerator
+	jwtToken, err := s.tokenGenerator.GenerateSessionToken(sessionId, expiresAt)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate JWT session token: %w", err)
+	}
+	credentials.SessionToken = jwtToken
+
 	// 5. Create session information
 	session := &SessionInfo{
 		SessionId:   sessionId,
@@ -359,6 +370,13 @@ func (s *STSService) AssumeRoleWithCredentials(ctx context.Context, request *Ass
 		return nil, fmt.Errorf("failed to generate credentials: %w", err)
 	}
 
+	// Generate proper JWT session token using our TokenGenerator
+	jwtToken, err := s.tokenGenerator.GenerateSessionToken(sessionId, expiresAt)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate JWT session token: %w", err)
+	}
+	tempCredentials.SessionToken = jwtToken
+
 	// 6. Create session information
 	session := &SessionInfo{
 		SessionId:   sessionId,
@@ -399,25 +417,19 @@ func (s *STSService) ValidateSessionToken(ctx context.Context, sessionToken stri
 		return nil, fmt.Errorf("session token cannot be empty")
 	}
 
-	// For now, use the session token as session ID directly
-	// In a full implementation, this would:
-	// 1. Parse JWT session token
-	// 2. Verify signature and expiration
-	// 3. Extract session ID from claims
-
-	// Extract session ID (simplified - assuming token contains session ID directly)
-	sessionId := s.extractSessionIdFromToken(sessionToken)
-	if sessionId == "" {
-		return nil, fmt.Errorf("invalid session token format")
+	// Use token generator for proper JWT validation
+	claims, err := s.tokenGenerator.ValidateSessionToken(sessionToken)
+	if err != nil {
+		return nil, fmt.Errorf("invalid session token format: %w", err)
 	}
 
-	// Retrieve session from store
-	session, err := s.sessionStore.GetSession(ctx, sessionId)
+	// Retrieve session from store using session ID from claims
+	session, err := s.sessionStore.GetSession(ctx, claims.SessionId)
 	if err != nil {
 		return nil, fmt.Errorf("session validation failed: %w", err)
 	}
 
-	// Additional validation can be added here
+	// Additional validation - check expiration
 	if session.ExpiresAt.Before(time.Now()) {
 		return nil, fmt.Errorf("session has expired")
 	}
@@ -435,14 +447,14 @@ func (s *STSService) RevokeSession(ctx context.Context, sessionToken string) err
 		return fmt.Errorf("session token cannot be empty")
 	}
 
-	// Extract session ID from token
-	sessionId := s.extractSessionIdFromToken(sessionToken)
-	if sessionId == "" {
-		return fmt.Errorf("invalid session token format")
+	// Use token generator for proper JWT validation
+	claims, err := s.tokenGenerator.ValidateSessionToken(sessionToken)
+	if err != nil {
+		return fmt.Errorf("invalid session token format: %w", err)
 	}
 
-	// Remove session from store
-	err := s.sessionStore.RevokeSession(ctx, sessionId)
+	// Remove session from store using session ID from claims
+	err = s.sessionStore.RevokeSession(ctx, claims.SessionId)
 	if err != nil {
 		return fmt.Errorf("failed to revoke session: %w", err)
 	}