Special Publication 800-95 (Draft) Guide to Secure Web Services (DRAFT) Recommendations of the National Institute of Standards and Technology Anoop Singhal Theodore Winograd GUIDE TO SECURE WEB SERVICES (DRAFT) NIST Special Publication 800-95 Guide to Secure Web Services (Draft) (Draft) Recommendations of the National Institute of Standards and Technology Anoop Singhal Theodore Winograd C O M P U T E R S E C U R I T Y Computer Security Division Information Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-8930 September 2006 U.S. Department of Commerce Carlos M. Gutierrez, Secretary Technology Administration Robert Cresanti, Under Secretary of Commerce for Technology National Institute of Standards and Technology William A. Jeffrey, Director ii GUIDE TO SECURE WEB SERVICES (DRAFT) Reports on Computer Systems Technology The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the nation’s measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept implementations, and technical analysis to advance the development and productive use of information technology. ITL’s responsibilities include the development of technical, physical, administrative, and management standards and guidelines for the cost-effective security and privacy of sensitive unclassified information in Federal computer systems. This Special Publication 800-series reports on ITL’s research, guidance, and outreach efforts in computer security and its collaborative activities with industry, government, and academic organizations. National Institute of Standards and Technology Special Publication 800-95 (Draft) Natl. Inst. Stand. Technol. Spec. Publ. 800-95, 140 pages (September 2006) Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessa rily the best available for the purpose. iii GUIDE TO SECURE WEB SERVICES (DRAFT) Acknowledgements The authors, Anoop Singhal of the National Institute of Standards and Technology (NIST) and Theodore Winograd of Booz Allen Hamilton, wish to thank their colleagues who contributed technical content to this document, especially Holly Lynne McKinley, Patrick Holley, and Karen Goertzel of Booz Allen Hamilton. The authors would like to acknowledge Tim Grance, David Ferraiolo, and Karen Kent of NIST, and David Kleiner of Booz Allen Hamilton, for their keen and insightful assistance throughout the development of the document. Additional acknowledgements will be added to the final version of the publication. iv GUIDE TO SECURE WEB SERVICES (DRAFT) Table of Contents Executive Summary..............................................................................................................ES-1 1. Introduction ......................................................................................................................1-1 1.1 Authority...................................................................................................................1-1 1.2 Purpose and Scope .................................................................................................1-1 1.3 Audience ..................................................................................................................1-1 1.4 Document Structure .................................................................................................1-2 2. Background to Web Services and Their Relationship to Security ..............................2-1 2.1 Introducing Web Services ........................................................................................2-1 2.1.1 Web Service Messaging...............................................................................2-1 2.1.2 Web Service Discovery ................................................................................2-2 2.1.3 Web Portals ..................................................................................................2-3 2.1.4 Web Service Roles, Modes, and Properties.................................................2-3 2.1.5 Coordination: Orchestration and Choreography...........................................2-5 2.2 Elements of Security ................................................................................................2-6 2.3 Web Services Security Dimensions .........................................................................2-7 2.3.1 Secure Messaging........................................................................................2-7 2.3.2 Protecting Resources ...................................................................................2-8 2.3.3 Negotiation of Contracts ...............................................................................2-8 2.3.4 Trust Relationships.......................................................................................2-9 2.3.5 Properties of Secure Software for Web Services .......................................2-10 2.4 Meeting the Requirements for Securing Web Services .........................................2-11 2.4.1 Secure Web Service Standards Stack .......................................................2-11 2.4.2 Secure Web Services Standards................................................................2-13 2.4.3 Security Architecture/Reference Model for Web Services..........................2-14 2.5 Core Services ........................................................................................................2-15 2.6 Common Attacks against Web Services................................................................2-16 2.7 Web Services’ Interfaces with Network/Infrastructure Security Architectures........2-17 2.8 Summary................................................................................................................2-18 3. Web Service Security Functions and Related Technologies.......................................3-1 3.1 Service-to-Service Authentication............................................................................3-1 3.1.1 WS-Security for Authentication.....................................................................3-1 3.1.2 Security Concerns of WS-Security ...............................................................3-2 3.2 Establishing Trust between Services .......................................................................3-4 3.2.1 Federation of Trust .......................................................................................3-5 3.2.2 Trust Federation Frameworks ......................................................................3-5 3.3 Distributed Authorization and Access Management ................................................3-8 3.3.1 Authorization Models ....................................................................................3-8 3.3.2 Enforcing Least Privilege for Services........................................................3-12 3.3.3 XACML .......................................................................................................3-14 3.3.4 Role of XML Schema in Implementing Access Control ..............................3-17 3.3.5 Use of Specialized Security Metadata for Access Control .........................3-18 3.4 Confidentiality and Integrity of Service to Service Interchanges............................3-18 3.4.1 Transport Layer Confidentiality and Integrity: HTTPS ................................3-19 3.4.2 XML Confidentiality and Integrity................................................................3-19 3.4.3 SOAP Confidentiality and Integrity .............................................................3-21 v GUIDE TO SECURE WEB SERVICES (DRAFT) 3.4.4 Role of XML Gateways in Integrity Protection ............................................3-21 3.5 Accountability End-to-End throughout a Service Chain .........................................3-22 3.5.1 Audit in the SOA Environment....................................................................3-23 3.5.2 Non-Repudiation of Web Service Transactions..........................................3-23 3.6 Availability of Web Services...................................................................................3-24 3.6.1 Failover.......................................................................................................3-25 3.6.2 Quality of Service .......................................................................................3-26 3.6.3 Reliable Messaging ....................................................................................3-26 3.6.4 Handling Service Deadlock ........................................................................3-26 3.6.5 Service Recursion ......................................................................................3-27 3.7 Securing the Discovery Service: Secure Interfaces to UDDI and WSDL...............3-27 3.7.1 UDDI Structure ...........................................................................................3-28 3.7.2 UDDI Operations ........................................................................................3-28 3.7.3 Secure Access to the Registry ...................................................................3-29