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Exploring WAP Security Models and Architectures

Discover the security basics, wireless security, WTLS, SSL, and WAP security models. Learn about access control, WIM, WMLScript, and more. Understand the need for app-level security, bearer independence, and gateway security. Dive into WTLS goals, encryption methods, and operator-hosted gateway setups with or without PKI. Explore the advantages and disadvantages of static and dynamic gateway connections by content providers. Find key insights to secure gateways and prevent unauthorized access effectively.

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Exploring WAP Security Models and Architectures

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  1. A Survey of WAP Security Architecture Neil Daswani neil@yodlee.com

  2. Overview • Security Basics • Wireless Security • WTLS & SSL • WAP Security Models • WIM, WMLScript, Access Control • Summary • References Neil Daswani, neil@yodlee.com

  3. Security Basics • Security Goals • Authentication • Confidentiality • Integrity • Authorization • Non-Repudiation Neil Daswani, neil@yodlee.com

  4. Security Basics • Cryptography • Symmetric: 3DES, RC4, etc. • Asymmetric: RSA, ECC • Key Exchange • Digital Signature • Certificates • PKI Neil Daswani, neil@yodlee.com

  5. Wireless Security • Link Layer Security • GSM • CDMA • CDPD • Application Layer Security • WAP: WTLS, WML, WMLScript, & SSL • iMode: N/A • SMS: N/A Neil Daswani, neil@yodlee.com

  6. Need for App Level Security • Bearer Independence • Security out to Gateway • Advanced Security Goals (ie. Non-Repudiation) Neil Daswani, neil@yodlee.com

  7. Basic WAP Architecture WTLS SSL Web Server Internet Gateway Neil Daswani, neil@yodlee.com

  8. WTLS & SSL • WTLS Goals • Authentication: Asymmetric Key Crypto • Class 1: No Authentication • Class 2: Server Authentication • Class 3: Mutual Authentication • Privacy: Symmetric Key Crypto • Data Integrity: MACs Neil Daswani, neil@yodlee.com

  9. WTLS: Class 1 • No Authentication ClientHello -----------> ServerHello <----------- ServerHelloDone ClientKeyExchange ChangeCipherSpec Finished -----------> <----------- Finished Application Data <----------> Application Data Neil Daswani, neil@yodlee.com

  10. WTLS: Class 2 • Server-Authentication Only ClientHello -----------> ServerHello Certificate <----------- ServerHelloDone ClientKeyExchange ChangeCipherSpec Finished -----------> <----------- Finished Application Data <----------> Application Data 1. Verify Server Certificate 2. Establish Session Key Neil Daswani, neil@yodlee.com

  11. WTLS: Class 3 • Mutual-Authentication Client Hello -----------> ServerHello Certificate CertificateRequest <----------- ServerHelloDone Certificate ClientKeyExchange (only for RSA) CertificateVerify ChangeCipherSpec Finished -----------> <----------- Finished Application Data <----------> Application Data 1. Verify Server Certificate 2. Establish Session Key 3. Generate Signature Neil Daswani, neil@yodlee.com

  12. TLS/SSL vs. WTLS • WTLS supports ECC • WTLS over WDPTLS over TCP • Premaster secret is 20 bytes (vs. 48 in TLS/SSL) Neil Daswani, neil@yodlee.com

  13. WAP Security Models • Operator Hosts Gateway • Without PKI • With PKI • Content Provider Hosts Gateway • Static Gateway Connection • Dynamic Gateway Connection Neil Daswani, neil@yodlee.com

  14. Operator Hosts Gateway WTLS Class 1 or Encrypted HDTP SSL Web Server Internet WAP/HDTP Gateway • Without PKI Content Provider Operator Neil Daswani, neil@yodlee.com

  15. Operator Hosts Gateway • Without PKI: • Advantages • No extra work for Content Provider • No extra work for user • System only requires one logical gateway • Disadvantages • Content Provider must trust Operator (NDA) • Operator can control home deck • Operator can introduce advertising Neil Daswani, neil@yodlee.com

  16. Operator Hosts Gateway • With PKI Neil Daswani, neil@yodlee.com

  17. Operator Hosts Gateway • With PKI: • Advantages • Content providers does not need to trust Operator. • Disadvantages • PKI Infrastructure must be in place. Neil Daswani, neil@yodlee.com

  18. Content Provider Hosts Gateway • Static Gateway Connection WTLS Class 2 Content Provider WAP Gateway Web Server SSL Neil Daswani, neil@yodlee.com

  19. Content Provider Hosts Gateway • Static Gateway Connection • Advantages • Content Provider does not need to trust Operator • Content Provider can control home deck • OTA can be used to configure mobile terminal • Disadvantages • Mobile terminal may have limited number of gateway config sets (i.e., Nokia 7110 has 10) • Mobile Terminal needs to be configured. • OTA via WAP Push / SMS may not work with gateway / mobile terminal combination • Content Provider may have to pre-configure mobile terminals Neil Daswani, neil@yodlee.com

  20. Content Provider Hosts Gateway • Dynamic Gateway Connection WTLS Class 2 SSL Operator WAP Gateway Internet WAP Gateway Content Provider Web Server SSL Neil Daswani, neil@yodlee.com

  21. Content Provider Hosts Gateway • Dynamic Gateway Connection • Advantages • Content Provider does not need to trust Operator. • Content Provider does not need to worry about mobile terminal config • Disadvantages • Operator needs to trust Content Provider. • Not deployed yet. Neil Daswani, neil@yodlee.com

  22. Restricting Gateway Access • Consider the following attack: • Eve runs a “modified” WAP gateway • Eve fools a user into using her gateway • Now, Eve can eavesdrop on all of the users requests and responses! • To prevent this, check the gateway IP address in the HTTP request. Neil Daswani, neil@yodlee.com

  23. WIM: WAP Identity Module • WIM must be tamper-resistant • Stores Keys & Master Secrets • Computes crypto operations • “unwrapping master secret” • client signature in WTLS Handshake • key exchange (ECC WTLS Handshake) • Also: • Generates Keys • Stores Certificates (or their URLs) • CA & Root Certs • User Certs • Can be implemented with SIM Neil Daswani, neil@yodlee.com

  24. WMLScript Crypto API • Non-repudiation • signedString = Crypto.signText (stringToSign, options, keyIdType, keyId) • Uses a separate, distinct signing key • WIM can store signing key and compute signature Neil Daswani, neil@yodlee.com

  25. WML Access Control • WML Deck-Level Access Control<wml><head><access domain=“worldfaq.com” path = “/stats”></head><card>…</card></wml> • WMLScript Access Controluse access domain domain_name | path path_name | domain domain_name path path_name; • use access domain “worldfaq.com” path “/stats” Neil Daswani, neil@yodlee.com

  26. Summary • Gateway position & configuration allows for different trust models • Security at multiple levels • Link Layer (depends on bearer) • App Layer • Authentication, Confidentiality, and Integrity: WTLS • Authorization: App-dependent, or WML <access> and WMLScript use access pragma • Non-Repudiation: WML signText Neil Daswani, neil@yodlee.com

  27. References • C. Arehart, N. Chidambaram, S. Guruprasad, et. al. Professional WAP. Wrox Press, 2000. ISBN 1-861004-0-44 • D. Margrave, GSM Security and Encryption • WAP-100, Wireless Application Protocol Architecture Specification • WAP-191, Wireless Markup Language Specification • WAP-193, WMLScript Language Specification • WAP-199, Wireless Transport Layer Security Specification • WAP-198, Wireless Identity Module • WAP-161, WMLScript Crypto API Library • WAP-187, WAP Transport Layer E2E Security Specification • WAP-217, WAP Public Key Infrastructure Definition Neil Daswani, neil@yodlee.com

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