Wolfgang Schneider

Internet Security – Where are we Heading?

GMD Darmstadt

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Layered Approach to Security

Application Security

Network Security

Physical Security

Operating System Security

Public Key Infrastructure

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Types of Standards

Framework/Architecture

High Level API

Protocols

Low Level API

Algorithms

Legal &Regulatory

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IETF Security

Cornerstones:Cornerstones: IP layer VPNs (IPsec)IP layer VPNs (IPsec) Secure web access (TLS)Secure web access (TLS) Secure E-mail (S/MIME)Secure E-mail (S/MIME) Public Key Infrastructure (PKIX)Public Key Infrastructure (PKIX)

Plus XMLSIG, OPGP, SSH, CAT, DNSSEC, ...Plus XMLSIG, OPGP, SSH, CAT, DNSSEC, ...

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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

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HOST 2B

HOST 8

HOST 6MobileHOST

IPsec Path Options

AHOST 1 HOST 3

C

C HOST 7A

B

ROUTER 1C

INTERNET

C

A

ROUTER 2A

A

A ROUTER 3

BB

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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

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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

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What’s Next for IPsec?

Standard policy language? Inter-domain policy negotiation Security gateway discovery Public key certificate syntax conventions Routing for VPNs

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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

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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

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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

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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

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S/MIME Standards

S/MIME v2 (RFC 2312)S/MIME v2 (RFC 2312) S/MIME v3 (RFC 2633)S/MIME v3 (RFC 2633) Cryptographic Message Syntax (RFC 2630)Cryptographic Message Syntax (RFC 2630) Certificate handling conventions (RFC 2312, Certificate handling conventions (RFC 2312,

2632)2632) Enhanced services (RFC 2634)Enhanced services (RFC 2634)

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HostHost

Originator

Router Mail Relay Host

Recipient

IPNetworkService

TCPTransport

RFC 822

IPNetworkService

MIME

SMTP

S/MIMEContent

RFC 822

MIME

TCPTransport

IPNetworkService

SMTP

S/MIMEContent

Mail RoutingSMTP SMTP

TCPTransport

IPNetworkService

TCPTransport

IPNetworkService

Internet Message Protocol Layers

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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)

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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

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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 plain data

S/MIME adds signed and unsigned attributes

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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

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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, ...

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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

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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

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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

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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!

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PKIX

Certificate & CRL syntax and processing (RFC 2459)Certificate & CRL syntax and processing (RFC 2459) CMP - Certificate Management Protocols (RFC 2510)CMP - Certificate Management Protocols (RFC 2510) OCSP - Online Certificate Status Protocol (RFC OCSP - Online Certificate Status Protocol (RFC

2560)2560) CRMF – Cert Request Message Format (RFC 2511)CRMF – Cert Request Message Format (RFC 2511) Certification policies & practices (RFC 2527-Certification policies & practices (RFC 2527-

informational)informational)

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More PKIX

LDAPv2 Schema & Operational Protocols LDAPv2 Schema & Operational Protocols (RFC 2587 & 2559)(RFC 2587 & 2559)

HTTP/FTP Ops (RFC 2585)HTTP/FTP Ops (RFC 2585) CMC – Cert Management Messages (RFC CMC – Cert Management Messages (RFC

xxxx)xxxx) Qualified Certificates (RFC xxxx)Qualified Certificates (RFC xxxx) Time stamping, notarization, ...Time stamping, notarization, ...

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Still PKIX

PKIX is now the basis of most major PKI PKIX is now the basis of most major PKI developments and deploymentsdevelopments and deployments

PKIX has still open interoperability issuesPKIX has still open interoperability issues ISOish growth, very complex and genericISOish growth, very complex and generic Various PKIX profilesVarious PKIX profiles Very slow deploymentVery slow deployment

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Architecture?

The IETF has many security area WGs and The IETF has many security area WGs and some other WGs are addressing security some other WGs are addressing security issuesissues

But, they lack a consistent, comprehensive But, they lack a consistent, comprehensive architecture, e.g., many protocols overlap in architecture, e.g., many protocols overlap in functionality!functionality!

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The future?