Internet Security – Where are we Heading?

1. Internet Security – Where are we Heading? Wolfgang Schneider GMD Darmstadt

2. Layered Approach to Security Application Security Public Key Infrastructure Network Security Operating System Security Physical Security

3. Types of Standards Framework/ Architecture High Level API Legal & Regulatory Protocols Low Level API Algorithms

4. IETF Security • Cornerstones: • IP layer VPNs (IPsec) • Secure web access (TLS) • Secure E-mail (S/MIME) • Public Key Infrastructure (PKIX) • Plus XMLSIG, OPGP, SSH, CAT, DNSSEC, ...

5. IPsec Overview • Adopted as Proposed Standards by the IETF: RFCs 2401-2412 (12/98) • IPv4 and IPv6 compatible formats • Authentication Header (AH) for (whole datagram) integrity and authenticity, and optional anti-replay • Encapsulating Security Payload (ESP) for modular confidentiality, authentication, integrity, and anti-replay • Separate security association negotiation and key management protocol: IKE

6. Mobile HOST HOST 6 ROUTER 2 HOST 8 ROUTER 1 C HOST 7 A HOST 1 HOST 3 C IPsec Path Options ROUTER 3 A B B B INTERNET A C A C A HOST 2 A B

7. IPsec Access Control • Security Policy Databases (SPDs) • Separate for inbound and outbound traffic for each interface • SPD entry specifies: • drop • bypass • IPsec (protocols & algorithms) • Traffic characterized by selectors: • source/destination IP addresses (also bit masks & ranges) • next protocol • source/destination ports • User or system ID (must map to other selectors in a security gateway) • In a host, mapping can be done at connection establishment • In a security gateway, mapping must be checked for each packet

8. IKE: Internet Key Exchange Protocol • IKE is the default key management protocol for IPSEC, based on three key management protocols: ISAKMP, Oakley, and SKEME • IKE encompasses algorithms for key establishment, SA parameter negotiation, identification & authentication • Variable number of messages exchanged, depending on mode (Main, Aggressive, Quick) • One IKE SA between a pair of IPsec implementations can support later user traffic SA establishment

9. What’s Next for IPsec? • Standard policy language? • Inter-domain policy negotiation • Security gateway discovery • Public key certificate syntax conventions • Routing for VPNs

10. Secure Sockets Layer (SSL) • Developed by Netscape to secure web browsing • Designed to be a “session layer” protocol over TCP -- individual session can span multiple TCP connections • Based on client-server (vs. peer) communication model • Aimed at being algorithm independent -- supports multiple encryption, authentication-integrity, and key exchange algorithms • Transport Layer Security (TLS) protocol in IETF (despite the misnomer!) is standards-based successor

11. SSL Security Services & Algorithms • Confidentiality • Block Cipher (RC2, DES, 3DES, Skipjack) • Stream Cipher (RC4) • Server Authentication • based on use of server X.509 certificate, roots in browsers • Client Authentication • optional, supported only if client certificates are available • Strict Message Sequencing • relies on TCP • Compression • optional, currently not generally implemented

12. Enhancements in TLS • SSL has been adopted and enhanced by IETF Transport Layer Security (TLS) Working Group into the TLS protocol • TLS v.1.0 is an enhancement of SSL v.3.0 • Major changes in TLS v1.0 • required algorithm support for DSA and D-H, RSA optional • use of HMAC vs. SSL-defined keyed MAC algorithm • modified key generation algorithm uses both MD5 and SHA-1 with HMAC as a pseudo-random function • use of both MD5 and SHA-1 in RSA signatures • more complete set of error alerts

13. TLS Summary • Status -- • SSL v.3.0 [11/96] is the current version • TLS 1.0 is a proposed standard, RFC 2246 • Popularity -- designed for securing HTTP, now used to protect multiple applications • Not architecturally appropriate? -- TCP/IP does not have a session layer but SSL was motivated by web-based transactions and time-to-market considerations • Basic Services -- server authentication, message encryption & integrity • Deployed algorithms -- RSA and RC4 • IESG Direction -- DSS signature, DH key generation, DES encryption to become default mechanisms

14. S/MIME Standards • S/MIME v2 (RFC 2312) • S/MIME v3 (RFC 2633) • Cryptographic Message Syntax (RFC 2630) • Certificate handling conventions (RFC 2312, 2632) • Enhanced services (RFC 2634)

15. Internet Message Protocol Layers Originator Recipient Host Host S/MIME Content S/MIME Content MIME MIME RFC 822 RFC 822 Mail Routing SMTP SMTP SMTP SMTP TCP Transport TCP Transport TCP Transport TCP Transport IP Network Service IP Network Service IP Network Service IP Network Service IP Network Service Router Mail Relay Host

16. What Are S/MIME Messages? • Combinations of two separately defined formats • (1) MIME entities • (2) Cryptographic Message Syntax (CMS) objects • S/MIME entity formats • one for enveloped (i.e., encrypted) – provides confidentiality and key distribution services • two for signed– each provides integrity and data origin authentication services • nested combinations of signed and encrypted formats • may nest in any order to any “reasonable” depth • multiple nesting is used to construct S/MIME Enhanced Security Services (details later)

17. S/MIME Version 2 • RFC 2311 – S/MIME Version 2 Message Specification, which is based on . . . • RFC 2315 – PKCS #7: Cryptographic Message Syntax Version 1.5 • Public-Key Cryptography Standards (PKCS): specifications begun in 1991 by RSA Laboratories and other industry and academic participants • PKCS #7: a general syntax for data that may have cryptography applied to it, e.g., digital signatures • defines a “digital envelope for a recipient” :(1) data encrypted in a content encryption key (CEK)(2) CEK encrypted in a second key, known to the recipient

18. S/MIME Version 3 • RFC 2633 – S/MIME Version 3 Message Specification, which is based on . . . • RFC 2630 – Cryptographic Message Syntax • enhancements to PKCS #7 • adds attribute certificates, key agreement methods • adds encapsulation syntax for data protection • adds multiple, nested encapsulations • S/MIME uses three of the CMS data types • enveloped data • signed data • just plaindata • S/MIME adds signed and unsigned attributes

19. S/MIME Enhanced Security Services • Optional features provide functionality similarto the SDNS Message Security Protocol • signed receipts • security labels • secure mailing lists • These features interact • Mail List Agents (MLAs) enforce access controls based on security labels • MLAs can override the message originator’s requests for signed receipts

20. The BGP Security Problem • BGP is the critical infrastructure for Internet, inter-domain routing • Benign configuration errors have wreaked havoc for portions of the Internet address space • The current system is highly vulnerable to human errors, as well as a wide range of attacks • At best, BGP uses point-to-point keyed MAC, with no automated key management • Most published BGP security proposals have been pedagogic, not detailed, not deployable • Solutions must take into account Internet topology, size, update rates, ...

21. BGP Security Requirements • Verification of address space “ownership” • Authentication of Autonomous Systems (AS) • Router authentication and authorization (relative to an AS) • Route and address advertisement authorization • Route withdrawal authorization • Integrity and authenticity of all BGP traffic on the wire • Timeliness of BGP traffic

22. Securing UPDATE messages • A secure UPDATE consists of an UPDATE message with a new, optional, transitive path attribute for route authorization • This attribute consists of a signed sequence of route attestations, nominally terminating in an address space attestation • This attribute is structured to support both route aggregation and AS sets • Validation of the attribute verifies that the route was authorized by each AS along the path and by the ultimate address space owner

23. Distributing Certificates, CRLs, & AAs • Putting certificates & CRLs in UPDATEs would be redundant and make UPDATEs too big • Same is true for address attestations • Solution: use servers for these data items • replicate for redundancy & scalability • locate at NAPs for direct (non-routed) access • download options: • whole certificate/AA/CRL databases • queries for specific certificates/AAs/CRLs • To minimize processing & storage overhead, NOCs should validate certificates & AAs, and send processed extracts to routers

24. S-BGP Summary • The transmission and processing costs of S-BGP are not significant • The proposed distribution mechanisms for certificates, CRLs, and AAs is viable • Storage overhead exceeds the capacity of existing routers, but adding adequate storage is feasible, especially for ISP BGP speakers • Testing and deployment issues • Cisco handling of optional, transitive path attributes • Intra-domain distribution of S-BGP attribute • But deployment poses a chicken and egg problem!

25. PKIX • Certificate & CRL syntax and processing (RFC 2459) • CMP - Certificate Management Protocols (RFC 2510) • OCSP - Online Certificate Status Protocol (RFC 2560) • CRMF – Cert Request Message Format (RFC 2511) • Certification policies & practices (RFC 2527-informational)

26. More PKIX • LDAPv2 Schema & Operational Protocols (RFC 2587 & 2559) • HTTP/FTP Ops (RFC 2585) • CMC – Cert Management Messages (RFC xxxx) • Qualified Certificates (RFC xxxx) • Time stamping, notarization, ...

27. Still PKIX • PKIX is now the basis of most major PKI developments and deployments • PKIX has still open interoperability issues • ISOish growth, very complex and generic • Various PKIX profiles • Very slow deployment

28. Architecture? • The IETF has many security area WGs and some other WGs are addressing security issues • But, they lack a consistent, comprehensive architecture, e.g., many protocols overlap in functionality!

29. The future?