t 110 455 network application frameworks and xml summary and conclusions 27 04 2005 sasu tarkoma
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T-110.455 Network Application Frameworks and XML Summary and Conclusions 27.04.2005 Sasu Tarkoma. Topics Covered. Distributed systems security Multi-addressing: Mobility and multi-homing Building applications with XML Distributed objects Role of directory services

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topics covered
Topics Covered
  • Distributed systems security
  • Multi-addressing: Mobility and multi-homing
  • Building applications with XML
    • Distributed objects
    • Role of directory services
    • Mobile and wireless applications
    • XML-based presentation and RPC
  • Scalability and performance issues
lecture outline
Lecture Outline

Note: starts 16.00

interconnections

Objects

Interconnections
  • Interconnections applicable on many levels
    • Network-level operation
      • DNS, overlay lookup, IPsec
    • Application-level operation
      • UDDI, SSL, WS-Security

Network

Security

Directories

naming addressing and routing
Naming, Addressing, and Routing

How to identify and name a node?

Frequent updates?

One or two new name spaces?

NAMING

unicast: to a specific node

broadcast: to all nodes

multicast: to a subset of nodes

anycast: to any one in some subset (IPv6)

ROUTING

ADDRESSING

How to route information to the node’s address? NAT traversal?

Overlay vs. network routing

Where is the node located?

Differences (IPv4/IPv6)

Multi-addressing?

tcp ip network stack
TCP/IP Network Stack

All applications (FTP, Telnet,

HTTP, Overlays)

Application Layer

host-to-host transport

reliability, congestion control,

flow control

Transport Layer (TCP/UDP)

host-to-host connectivity

routing, addressing

HOST-TO-HOST

Link layer: local data transfer,

encoding, framing, error correction

Physical: transmission of signals

Networking Layer (IP)

Underlying network (link layer)

routing vs mobility
Routing vs. mobility
  • Topology data aggregation is necessary
    • Cannot track all hosts in the world
    • IP addresses determined by topology
      • Network gives the routing prefix
  • Mobile hosts must change their IP addresses
    • Causes sockets / connections to break
  • How to communicate address changes?
  • Goal of a mobility protocol
    • Transport and applications do not see address changes
networks mobility

MH

AP

NAT

GPRS/UMTS

Access network

Public Switched Data Network

NAT

Router

Router

BS

BS

Backbone LAN

MAN

Ad hoc

MH

MH

R

R

R

R

Router

Router

Networks: Mobility

R

rendezvous
Rendezvous
  • How to find the moving end-point?
    • Tackling double jump
      • What if both hosts move at the same time?
      • Requires a rendezvous point
  • Mobility management is needed!
    • Initial rendezvous
    • Can be based on directories
    • Requires fast updates to directories
      • Does not work well for DNS
slide11

Process

Transport

IP Layer

Link Layer

Identity/Locator split

  • New name space for IDs
    • Maybe based on DNS
    • Maybe a separate namespace
    • Maybe IP addresses are used for location
    • Good for hiding IP versions
  • Communication end-points (sockets) bound to identifiers

identifier

ID Layer

locator

host identity protocol
Host Identity Protocol
  • New cryptographic namespace
  • Connection endpoints mapped to 128 bit host identity tags (hashes of public keys)
  • Mapping at HIP layer
  • 4-phase Base Exchange with cryptographic puzzle for DoS prevention
  • IPSec for network-level security
upper layer view
Upper layer view
  • IP connectivity problematic today
    • Broken by firewalls, NATs, mobility
    • Two versions of IP: IPv4 and IPv6
  • HIP has a potential remedy
    • Restores end-to-end connectivity (NAT traversal possible but may require changes / tunnelling)
    • Adds opportunistic security
    • Handles mobility and multi-homing
    • Requires DHT based overlay (currently missing)
  • Where is the network state?
    • Routers know addresses
      • Like today
    • DHT knows HITs / SIDs
      • Lease based storage
    • Middleboxes know SPIs
      • Soft state
lessons to learn
Lessons to learn
  • Hierarchical routing likely to stay
    • Addresses carry topological information
    • Efficient and well established
  • Applications face changing connectivity
    • QoS varies
    • periods of non-connectivity
  • Identifiers and locators likely to split
  • Mobility management is needed
  • Probably changes in directory services
    • Overlays have been proposed
summary
Summary
  • Topology based routing is necessary
  • Mobility causes address changes
  • Address changes must be signalled end-to-end
  • Mobility management needed
    • Initial rendezvous: maybe a directory service
    • Double jump problem: rendezvous needed
  • Many engineering trade-offs
layered model revisited
Layered-model revisited

Finding, meta-data, invoking, syncing, mobility. Web Services

DNS names

Object API

XML presentation

Presentation

Firewall bypass

IP addresses

Congestion control

End-to-end

Routing

Routing paths

overlay networks
Overlay Networks
  • Origin in Peer-to-Peer (P2P)
  • Builds upon Distributed Hash Tables (DHTs)
  • Easy to deploy
    • No changes to routers or TCP/IP stack
    • Typically on application layer
  • Overlay properties
    • Resilience
    • Fault-tolerance
    • Scalability
slide19

Upper layers

DNS names, custom

identifiers

Overlay

Overlay addresses

Congestion

IP addresses

End-to-end

Routing

Routing paths

some dht applications
Some DHT applications
  • File sharing
  • Web caching
  • Censor-resistant data storage
  • Event notification
  • Naming systems
  • Query and indexing
  • Communication primitives
  • Backup storage
  • Web archive
applications for dhts
Applications for DHTs
  • DHTs are used as a basic building block for an application-level infrastructure
    • Internet Indirection Infrastructure (i3)
      • New forwarding infrastructure based on Chord
    • DOA (Delegation Oriented Architecture)
      • New naming and addressing infrastructure based on overlays
summary1
Summary
  • Mobility and multi-homing require directories
    • Scalability, low-latency updates
  • Overlay networks have been proposed
    • Searching, storing, routing, notification,..
    • Lookup (Chord, Tapestry, Pastry), coordination primitives (i3), middlebox support (DOA)
    • Logarithmic scalability, decentralised,…
  • Host/identity split and overlays for directories seem good candidates for solving many of the issues with mobility and multi-homing
middleware1
Middleware
  • Widely used and popular term
  • Fuzzy term
  • One definition
    • “A set of service elements above the operating system and the communications stack”
  • Second definition
    • “Software that provides a programming model above the basic building blocks of processes and message passing” (Colouris, Dollimore, Kindberg, 2001)
why middleware
Why Middleware?
  • Application development is complex and time-consuming
    • Should every developer code their own protocols for directories, transactions, ..?
    • How to cope with heterogeneous environments?
      • Networks, operating systems, hardware, programming languages
  • Middleware is needed
    • To cut down development time
      • Rapid application development
    • Simplify the development of applications
    • Support heterogeneous environments and mask differences in OS/languages/hardware
middleware cont
Middleware cont.
  • Middleware services include
    • directory, trading, brokering
    • remote invocation (RPC) facilities
    • transactions
    • persistent repositories
    • location and failure transparency
    • messaging
    • Security
  • Network stack (transport and below) is not part of middleware
transparencies
Transparencies
  • Location transparency
    • RPC and RMI used without knowledge of the location of the invoked procedure / object
  • transport protocol transparency
    • RPC may be implemented using any transport protocol
  • transparency of OS and hardware
    • RPC/RMI uses external data representation
    • Presentation is important
    • XML is becoming increasingly important
  • transparency of programming languages
    • language independent definition of procedures: CORBA IDL
network application framework
Network Application Framework
  • Network Application Framework is middleware
  • Contains services for distributed applications
  • Middleware as a term is fuzzier and larger
  • In this course, we focus on network application frameworks and XML
    • objects (discovery, representation)
    • directories (overlays,..)
    • network
    • security
examples
Examples
  • Middleware
    • CORBA
    • Message-oriented Middleware
    • Event Systems & tuple spaces
    • Java Message Service
    • Java 2 Enterprise Edition (J2EE)
    • .NET
  • Mobile middleware
    • WAE
    • J2ME
    • Wireless CORBA
    • FUEGO
mobile middleware i
Mobile Middleware I
  • Middleware is typically designed and implemented for fixed-network hosts
    • High bandwidth, low latency, reliable communication
    • Persistent storage and sufficient computing power
    • No mobility
  • Mobile environment requires new solutions
    • Existing middleware services do not scale
    • Previous lectures: mobility is challenging
    • Small devices / embedded systems pose totally different challenges
mobile middleware ii
Mobile Middleware II
  • Goals for middleware:
    • fault-tolerance, adaptability, heterogeneity,scalability, resource sharing
  • Mobile middleware
    • dynamically changing context
    • decoupled
      • events, tuple spaces
    • Basic solution for wireless
      • Use a proxy
summary2
Summary
  • Middleware
    • for application development and deployment
    • for supporting heterogeneous environments
    • Main communication paradigms: RPC/RMI, asynchronous events (publish/subscribe)
    • J2EE, CORBA, ..
  • Mobile middleware
    • Desktop middleware not usable on small, mobile devices
    • Special solutions are needed
    • J2ME, Wireless CORBA, ..
a basic web service

XML

XML

A Basic Web Service

Computer A

Language: C++

OS: W2000

Computer B

Language: Java

OS: Linux

Independent of

language, OS, network

protocols

standardization
Standardization
  • W3C Web Services
    • XML Protocol Working Group
      • SOAP
    • Web Services Addressing Working Group
    • Web Services Choreography Working Group
    • Web Services Description Working Group
      • WSDL
  • OASIS
    • E-business standards, UDDI
  • WS-I (Web Service Interoperability Org.)
    • Binding profiles,..
web service architecture
Web Service Architecture
  • The three major roles in web services
    • Service provider
      • Provider of the WS
    • Service Requestor
      • Any consumer / client
    • Service Registry
      • logically centralized directory of services
  • A protocol stack is needed to support these roles
web services protocol stack
Web Services Protocol Stack
  • Message Transport
    • Responsible for transporting messages
    • HTTP, BEEP
  • XML Messaging
    • Responsible for encoding messages in common XML format
    • XML-RPC, SOAP
  • Service Description
    • Responsible for describing an interface to a specific web service
    • WSDL
  • Service discovery
    • Responsible for service discovery and search
    • UDDI
ws protocol stack
WS Protocol Stack

Discovery: UDDI

Description: WSDL

XML Messaging: SOAP, XML-RPC, XML

Transport: HTTP, FTP, BEEP, SMTP, JMS

wsdl with java

WS requester

Business partner

or other system

SOAP RQ

SOAP RQ

Bind

Publish

Services

JAXR

SOAP RQ

WSDL document

WSDL with Java

2. Look up WS

UDDI

4. Call WS

firewall

1. WSDL is

published

to UDDI

3. Retrieve WSDL

description

JAXR=Java API for XML Registries

what is wsdl
What is WSDL?
  • WSDL: Web Service Description Language
  • An XML language used to describe and locate web services
    • location of web service
    • methods that are available
    • data type information and XML messages
  • Commonly used to describe SOAP-based services
  • W3C standard (work in progress)
    • Initial input: WSDL 1.1 as W3C Note
    • Current version 2.0 (last call)
    • Some differences between 1.1 and 2.0
  • WSDL 1.1 in WS-I Basic Profile 1.0 and 1.1.
wsdl overview
WSDL Overview

<definitions>: ROOT WSDL element

<types>: The data types that are used

<message>: What messages are transmitted?

<portType>: The supported operations

<binding>: The binding to concrete protocols

<service>: Reference to actual location

putting it together
Putting it together

Source: http://msdn.microsoft.com/

soap message structure

SOAP Envelope

SOAP Header

Header block

Header block

SOAP Body

Message Body

SOAP Message Structure

Optional header contains blocks of information regarding how to process the message:

    • Routing and delivery settings
    • Authentication/authorization assertions
    • Transaction contexts
  • Body is a mandatory element and contains the actual message to be delivered and processed (and fault information)
what is uddi
What is UDDI?
  • Universal Description Discovery and Integration
  • Industry-wide initiative supporting web services
  • Specifications
    • Schemas for service description
    • Schemas for business (service implementers) description
    • Developed on industry standards
      • Applies equally to XML and non-XML web services
  • Implementation
    • Public web service registry and development resources
    • SOAP-based programming protocol for registering and discovering Web services
      • XML schema for SOAP messages
      • a description of the API
  • UDDI does not directly specify how pricing, deadlines, etc. are handled/matched
    • Advanced discovery via portals and marketplaces
need for xml security
Need for XML security
  • XML document can be encrypted using SSL or IPSec
    • this cannot handle the different parts of the document
    • documents may be routed hop-by-hop
    • different entities must process different parts of the document
  • SSL/TLS/IPSec provide message integrity and privacy only when the message is in transit
  • We also need to encrypt and authenticate the document in arbitrary sequences and to involve multiple parties
high level view to ws security
High-level view to WS security
  • Security is as strong as the weakest link
  • The options for an attacker are:
    • Attack the Web Service directly
      • Using ”unexpected” XML
    • Attack the Web Services platform
    • Attack a WS security tool
    • Attack the underlying operating system or network connection
application layer security
Application-layer Security
  • Identity-based security
    • Authentication and authorization information shared across security domains
  • Content-based security
    • Protecting against buffer overflow and CGI-like attacks
    • Must have knowledge about the applications to which these messages are directed
  • Accountability or non-repudation
    • Need message level security
    • Maintain integrity, archived audit trails
  • The standards and specifications mentioned earlier address these issues
standardization landscape
Standardization landscape
  • Who are specifying the basic standards?
  • Who are specifying the higher level standards?
  • Who is implementing the standards?
who are specifying the standards
Who are specifying the standards?
  • Joint IETF/W3C
    • XML Signature (www.w3.org/Signature)
  • W3C
    • XML Encryption (www.w3.org/Encryption/2001)
    • XML Key Management (XKMS) (www.w3.org/2001/XKMS)
  • OASIS
    • WS-Security
      • SOAP Message Security specification etc.
    • SAML: Security Assertion Markup Language
    • XACML: Extensible Access Control Markup language
    • Electronic Business XML (ebXML) (with UN/CEFACT)
  • Web Services Interoperability Organization (WS-I)
    • Basic security
standardization groups

W3C

OASIS

Standardization Groups

Extensible Rights Markup Language

XrML

Provisioning

XML Common Biometric Format (XCBF)

eXtensible Access Control Markup Language (XACML)

XML Key Management Specification

WS-Security

Biometrics

XML Encryption

XML Signature

XKMS

SAML

XACML

Security Assertion Markup language

basic xml security
Basic XML Security
  • XML Digital Signatures (XMLDSIG)
  • XML Encryption
  • XML Canonicalization
  • XML Key Management
digital signatures

Message

Digest

Message

Digest

SIGN

VERIFY

Signature

Pass/Fail

Private key

Public key

Asymmetric Key Pair

Digital Signatures

Need to know the message, digest, and algorithm (f.e. SHA1)

Message

xml digital signatures cont
XML Digital Signatures (cont.)

<Signature ID?>

<SignedInfo>

<CanonicalizationMethod/>

<SignatureMethod/>

(<Reference URI?>

(<Transforms>)?

<DigestMethod></DigestMethod>

<DigestValue></DigestValue>

</Reference>)+

</SignedInfo>

<Signaturevalue></Signaturevalue>

(<KeyInfo>)?

(<Object ID?>)*

</Signature>

encryption

Encrypt

Decrypt

Public key

Private key

Asymmetric Key Pair

Encryption
xml encryption
XML Encryption

<EncryptedData Id? Type? MimeType? Encoding?>

<EncryptionMethod/>?

<ds:KeyInfo>

<EncryptedKey>?

<AgreementMethod>?

<ds:Keyname>?

<ds:RetrievalMethod>?

<ds:*>?

</ds:KeyInfo>

<CipherData>

<CipherValue>?

<CipherReference URI?>?

</CipherData>

<EncryptionProperties>?

</EncryptedData>

why canonicalization is hard
Why Canonicalization is Hard
  • Exactly the same sequence of data bytes must be used for signing as for verifying
    • Problem of DTDs & Schemas
    • Problem of white space
    • Curse of namespaces
    • The usual:
      • Encodings & character sets (UTF-8,..)
      • Representations (<foo/>, <foo></foo>)
      • Reordering of attributes
xml key management xkms
XML Key Management (XKMS)
  • A Web Service that provides an interface to a PKI
    • Abstracts PKI certificates
    • Towards centralized PKI management (an enterprise resource vs. configured by end-clients)
  • Designed to manage the sharing of public keys
    • Managing includes verifying signatures
    • Also includes encrypting messages
  • XKMS takes complexity from the applications
  • Originally from
    • VeriSign, Microsoft, webMethods
  • XKMS 1.0
    • W3C Note 30 March 2001
  • XKMS 2.0
    • W3C Candidate Recommendation 5 April 2004
xml key management xkms1
XML Key Management (XKMS)
  • The XML Key Management Specification (XKMS) comprises two parts
    • the XML Key Information Service Specification (X-KISS), and
      • Retrieval of information about keys
    • the XML Key Registration Service Specification (X-KRSS).
      • Store of information about keys
  • Uses the SOAP 1.1 protocol for communication, XML Schema, WSDL 1.0
  • Based on XML Signatures
web services security requirements
Web Services Security Requirements
  • Access control to Web services
    • WS-Security, XML-Signature
    • SAML – Issuing and validation of SAML assertions
    • Digital certificate validation
  • Content-filtering XML
    • Filters based on data format (XSD)
    • Filters based on content (XPath)
    • Filters based on integrity (XML Signature)
functional point of view

XML

XML

Functional point of view

Management

Console

Design and

Deploy

Security

policies

ID Management

LDAP

PKI

Single Sign-On

Authorization

Authentication

Content Checking

Reporting

Activity

Alerting

Secure logging

Integrity

Validation

Routing

security contexts in web services
Security Contexts in Web Services
  • Remember Web Services goals:
    • Re-use existing services
    • Combine services from several domains
  • Security result: Must support several security domains
    • SOAP intermediaries
    • Reusing security tokens from one message in another message
ws security i
WS Security I
  • Web Services Security: SOAP Message Security 1.0 (Oasis Standard 2004)
  • End-to-End security
    • Headers are decrypted and processed as needed
  • Selective processing
    • Some parts are plain text
    • Some are encrypted
    • Some are signed
  • How does it work?
    • SOAP header carries security information (and other info as well)
ws security ii
WS Security II
  • Ability to send security tokens as part of a message, message integrity, and message confidentiality
  • Security model in terms of security tokens combined with digital signatures to protect and authenticate SOAP messages
  • An X.509 is an example of a signed security token endorsed by a CA.
  • When third party support is not available, receiver may choose to accept the claims in the token based on trust on the entity that sent the message.
slide66
SAML
  • SAML (Security Assertion Markup Language)
    • A XML-based framework (schemas) for the exchange of authentication and authorization information
    • A standard message exchange protocol
      • How you ask and receive information
  • Mainly for integration, up to relying parties to decide to what authentication authority to trust
  • Assertions can convey information about authentication acts performed by subjects, attributes of subjects, and authorization decisions about whether subjects are allowed to access certain resources
    • Authentication statements merely describe acts of authentication that happened previously
  • Specified by OASIS
saml in a nutshell
SAML in a nutshell
  • XML-based framework for exchanging security information
    • XML-encoded security assertions
    • XML-encoded request/response protocol
    • Rules on using assertions with standard transport and messaging frameworks
  • SAML & WS-Security allow a SOAP message to include information about the end-user’s authentication status
summary3
Summary
  • Security contexts
    • Security needed within and between contexts
    • XML validation, encryption, and authentication needed between security contexts!
  • WS security standard revisited
    • SOAP header carries security information (and other info as well)
    • Selective processing
  • SAML
    • Statements about authorization, authentication, attributes
    • SAML & WS-Security & XACML
  • Implementations available
slide70

With identity/locator split + overlays?

CONTROL

Upper layers

DNS names, custom

identifiers

Overlay

Overlay addresses

Host Identities

Congestion

ID Layer

IP addresses

IP addresses

End-to-end

DATA

Routing

Routing paths

Routing paths

slide71

”Theory”

”Practice”

”Future?”

WS Security

WS Security

WS Security

SOAP

H

I

P

C

TRL

SOAP

SOAP

HTTP?/sockets

HTTP/TLS/sockets

TCP

TCP

TCP4

TCP6

HIPsec

IP

IPv4

IPv6

IPv4

IPv6

important dates
Important Dates
  • Exam on Thursday 12.5. 12-15 in T1.
  • Deadline for the second assignment 15.5.
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