Routing Security Security Solutions CSE598K/CSE545 - Advanced - - PowerPoint PPT Presentation

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Routing Security Security Solutions CSE598K/CSE545 - Advanced - - PowerPoint PPT Presentation

Sep 23, 2022 135 likes •314 views

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Routing Security Security Solutions

CSE598K/CSE545 - Advanced Network Security

  • Prof. McDaniel - Spring 2008

1 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Solving BGP Security

  • Reality: most attempts at securing BGP have been at the

local level

  • Filtering
  • Securing BGP peering
  • Future: a number of complex protocols have been

proposed to solve some or all BGP security issue

  • S-BGP
  • soBGP
  • IRV
  • SPV
  • We will be looking at these solutions over the next

couple of lectures

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Filtering

  • Filtering just drops BGP message (typically

advertisements) as they are passed between ASes

  • Ingress filtering (as it is received)
  • Egress filtering (as it is sent)
  • Types of filtering
  • By prefix (e.g., bogon/martian list)
  • By path (e.g., customer advertisement of provider routes)
  • By policy (e.g., some “community” strings that represent

paths/policies that an AS does not want to support)

  • ISP ASes aggressively filter (the security mechanism)

3 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Protecting Peer Communication

  • Two routers exchanging BGP messages (in a BGP

session) need to secure communication.

  • Integrity
  • Confidentiality?
  • Authenticity
  • Non-repudability?
  • Note: This is often defined as a transport security issue,

where just secure point-to-point communication is necessary.

4

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

MD5

  • A simple solution (RFC 2385)
  • Share a private secret (e.g., password)
  • Compute an keyed message authentication code on each

TCP packet passed between the two routers

  • Check MAC upon receipt of each packet
  • You get
  • Integrity
  • Authenticity
  • Problem: this is manual configuration, which neither

scales to many routers or supports key maintenance

5 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Generalized TTL Security Mechanism

  • TCP time-to-live (RFC 3682)
  • At a packets origination, the TTL is set to the maximum

number of hops that the packet can traverse

  • TTL decremented at each hop
  • Packets are dropped when TTL goes to 0
  • This ensures that packets stuck in transient routing loops do not

congest the network

  • Idea: can we use the TTL to ensure that every packet

received can from peer (assuming one hop)?

  • Set TTL = 255 (Q: how about TTL=1?)
  • Receiver checks TTL on all packets, if not 254, then forged
  • Issue: how much does this really tell you?

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

HOP Integrity

  • HOP integrity protocols implement peering secure

communication that provides integrity/authentication

  • Diffie-Hellman style key negotiation, data integrity, data

authentication

  • Idea: provide public key based per hop security, the simple

constructions to enforce integrity constraints

  • Two protocols
  • Weak - just per hop integrity (MAC)
  • Strong - adds replay protection (sequence numbers)
  • Note: used to secure communication between a range
  • f peers via a per-hop security (limitation?)

7 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Smith/Garcia-Luna-Aceves

  • A (ad hoc?) suite of countermeasures
  • 1. Encrypt all messages between peers
  • 2. Add a message sequence number to all BGP messages
  • Protects against replayed or deleted messages
  • 3. Add a sequence number (or time-stamps) to UPDATES
  • 4. Add a PREDECESSOR path attribute
  • 5. Digitally sign all the UPDATEs
  • Note: this gets beyond the basic peer security, and

bleeds into the more general BGP security issues.

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Question?

  • What attacks do these measures prevent?
  • If yes, how?
  • Message replay
  • Route replay
  • Path forgery
  • Path modification
  • Forged route withdrawal
  • Prefix hijacking

9 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

IPsec

  • IPsec provides all of the basic guarantees needed to

implement router-to-router BGP security

  • Independent of intermediate connectivity
  • IKE/ISAKMP used to establish transient keys
  • Avoids cryptanalysis of long running keys
  • ESP/AH provide confidentiality, integrity, replay protection ...
  • Problems: this is just a start
  • Overheads can be expensive if not managed correctly
  • Backward compatibility
  • Key management

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Peering Summary

  • Reality: most of these schemes were hacks or stop-gap

measures until IPsec became widely available

  • Where secured at all, IPsec is generally used
  • AH/ESP w/out confidentiality is popular
  • Singly-homed customer/ISP peering is often not secured at all
  • Question: why is this reasonable?

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Integrity Confidentiality Replay Prevention DOS Prevention IPsec (ESP) yes yes yes yes IPsec (AH) yes no yes yes MD5 Integrity yes no yes no HOP Protocol yes no yes no GTSM no no no no Smith .et al. yes yes yes no

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Assignment #2

  • Each of you is to implement a client/server file transfer

application on OpenSSL in C.

  • The client will send files.
  • The server will receive files (on port 5005).
  • The client will send an initial transfer request, followed

by blocks of the file.

  • Startup: ./assignment2 [server] [filename] [block length]
  • Part 1: run over unsecured connection
  • Part 2: run over secured connection
  • Use your own certificates for client and server

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Assignment #2 (cont.)

  • Transfer request:
  • Transfer block:

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Field Data Type Length (bytes) Request Type (2) integer 1 Block number unsigned long 4 Block length char variable Field Data Type Length (bytes) Request Type (1) integer 1 Filename char 128 Filesize (bytes) unsigned long 4 Block length unsigned short 2

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

BGP Security Protocols

  • The big two, plus one (self-serving)
  • sBGP (Secure Border Gateway Protocol)
  • [Kent et al. 99]
  • soBGP (Secure Origin BGP)
  • [White et al. 03]
  • IRV (Internet Routing Validation)
  • [Goodell et al. 03]

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

sBGP

  • sBGP was the first leading candidate for routing

security, and highlighted much of IR security issues

  • Still under consideration, but somewhat limited
  • Model: Routing and origination announcements are signed
  • signatures are validated based on shared trust associations (CAs)
  • It all begins with the keys (really two parallel PKIs)
  • 1. Binding routers and organizations to ASes.
  • 2. Origin authentication PKI

15 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Organization PKI

  • Keys for routers, AS numbers
  • Route attestations - attestations to the transient state
  • f the network, e.g., the advertisements/routes
  • Keys used to create these advertisements
  • Router certificates need to ascertain validity of

instantaneous advertisements.

  • You need to prove association between the network

elements making statements and AS/organizations

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Route Attestations

  • Signing recursively: each advertisement signs

everything it receives, plus the last hop.

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AS3

AS 1

AS5 AS2 AS4

(4, (3, (2, 1)kAS2)kAS3)kAS4

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Address Attestations

  • Attestations of ownership and delegation very

similar to that observed in origin authentication

  • These are the “simple attestations”
  • For example, assume that organization A delegates prefix p

to organization B:

  • Note: (surprisingly) sBGP distributes with address

attestations out-of-band

  • Thus everyone is required to obtain and validate their own

copies of origin/ownership proving certificates.

  • As in OA, validate path to ICANN

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(p, B)kA

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

sBGP Issues

  • Single point of trust: is an authority that everyone will

trust to provide address/path certification?

  • Chinese Military vs. NSA?
  • Cost: validating signatures is very computationally

expensive

  • Can a router sustain the load?
  • Incremental deployability: requires changes to BGP

message formats

  • All implementations must change

19 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

soBGP

  • CISCO’s entry in the securing Internet routing rodeo
  • Viewed as the manufacturer approach to implementing

security within BGP

  • Released as a kind of refutation of sBGP, which was seen as too

expensive and unwieldy to be practical.

  • A more “open” model that allows providers to implement

security much more flexibly, i.e., within the confines of existing policy and infrastructure

  • Basic approach: network providers themselves act as a

joint authority, and issue certificates for all relevant routing data, e.g., policy, address management, paths.

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

soBGP Design Requirements

  • System should take advantage of operational

experience and existing Internet Architecture.

  • Implicit trust built into the Internet
  • IP address assignment and delegation system
  • Minimize impact to current implementations
  • f the BGP protocol
  • Minimum changes to existing protocol

formats.

  • Optimize memory and processing

requirements.

21 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

soBGP Design Requirements

  • Must not rely on a central authority of any type.
  • Distributed processing and trust
  • Must be incrementally deployable (it must provide

some level of security without the participation of every AS).

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Solution*

  • Verifies originator of a route is authorized to do so.
  • Verifies that the advertised AS_PATH represents a valid path

to the originator. (plausible path?)

  • BGP Security Message (extension to BGP) New BGP

Message used to carry security information

  • No changes to existing messages for backwards compatibility

and incremental deployment. (removal of messages?)

  • Leverages existing protocol and security mechanisms
  • Fixed additional scalability requirements Per-AS information

and route policies advertised once. (caching)

  • No additional information in UPDATES, resulting in

low processing impact. (well, sort of)

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*CISCO text in black, my text in red.

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Certificates

  • Databases of certificates that advertise and correlate

AS identity, prefix ownership and route policy.

  • Certificate types:
  • Entity Certificate = Used to establish (AS) identity
  • Authorization Certificate = Assigns/delegates IP addresses
  • Policy Certificate = Used to define per-AS or pre-prefix

policies and propagate AS interconnectivity topology map

  • Certificate exchanges/trust relations are not defined
  • Prior to or within routing exchanges
  • Uses Web-of-Trust model to validate certificates.

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

PolicyCerts

  • Pairwise signing: the topology database contains peering

attestations.

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(4, (3, (2, 1)kAS2)kAS3)kAS4

AS3

AS 1

AS5 AS2 AS4

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

AuthCert and EntityCert

  • AuthCerts define the delegation of address space
  • Operates in essentially the same way as sBGP/OA
  • Some looked at OA in soBGP and looked to learn

the correct address assignment by viewing history

  • Kinda intrusion detection for address usage (open

problem)

  • EntityCerts identifies who/what router is

associated with which AS.

  • Again note: which of these certs you believe is up

to you (its a web of trust, caveat emptor)

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

Path Authentication vs. Path Plausibility

  • Is Path Authentication stronger than Path Plausibility?
  • “Since each AS in sBGP is authentication a relationship

between itself and its predecessor and successor ASes, the set of acceptable AS paths in sBGP is a subset of the set paths acceptable under SoBGP”

  • Argue for (and explain why or why not):
  • Q1: Is Path Lengthening in soBGP but not sBGP?
  • Q2: Is Path Shortening possible in sBGP but not soBGP?

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AS3

AS 1

AS5 AS2 AS4

(4, (3, (2, 1)kAS2)kAS3)kAS4

(4, (3, (2, 1)kAS2)kAS3)kAS4

CSE598K/CSE545 - Advanced Network Security - McDaniel Page

soBGP Issues

  • “Soft” security: the guarantees

provided are limited

  • E.g., plausible, not actual secure paths
  • Nebulus trust: not clear under what

conditions or trust model a certificate was created

  • Signatures in web of trust have unclear

semantics

  • Assumes transitive trust

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

IRV

  • Intended to solve BGP without changing any of existing

routing infrastructure

  • [Goodell et al. 2003]
  • Idea: validate all information by actively querying

databases of policy, address, and path information provided by

  • Post-facto verification - receive and optimistically accept

routing information

  • AS-centralized verification - an IRV service exists outside the

domain of the AS, provides validation information in real time to all routers (win--no per router cost)

29 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

IRV Operation

  • ASes provide a well-known IRV server from which any

external party can query for the validity of information

  • Authenticated responses provide assurance that

advertisements are correct

30 AS2 AS3 AS1

BGP Router

IRV IRV IRV

I R V Q u e r y

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CSE598K/CSE545 - Advanced Network Security - McDaniel Page

IRV Issues

  • DOS opportunities - IRV can get flooded with requests

by malicious party

  • Under normal operation following, for example, a table reset.
  • Offline operation - when the network fails, little ability

to return system to stable state

  • Possible solutions:
  • Peering repositories
  • Shadow control network

31 CSE598K/CSE545 - Advanced Network Security - McDaniel Page

BGP Security

  • Now: After a decade of work, we are not much closer

to a global security solution that we started with

  • Problems are often not technical ...
  • Cost of building routers
  • Backward compatibility
  • Incremental deployment
  • Future: we will move from a border filtering to more

and more cryptographically aided solutions.

  • Mining past advertisements and understanding “expected”

routing advertisements will also be key where crypto is not appropriate or feasible.

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