Origin Authentication in Interdomain Routing

1. Origin Authentication inInterdomain Routing William Aiello, John Ioannidis, and Patrick McDaniel Proceedings of 10th ACM Conference on Computer and Communications Security (CCS'03) Presenter: Lan Gao

2. What does the paper solve? • Problem • How do we ensure that addresses are associated with only those ASes that own them? • Origin Authentication • Provide a way to validate claims of address ownership in interdomain routing • Authenticate address usage • Defense against • Attacks by malicious entities • misconfigurations Presenter: Lan Gao

3. Overview • Background • Formalization • semantics of address delegation • Origin authentication proof systems • Modeling • address delegation graph • Evaluating resource costs Presenter: Lan Gao

4. Interdomain Routing • The Internet consists of many routing domains: • routing inside a domain is determined by an intradomain routing protocol • routing between domains is governed by an interdomain routing protocol • Intradomain and interdomain routing decisions are largely made independently • Reasons: • Scale • Administrative autonomy Presenter: Lan Gao

5. BGP (Border Gateway Protocol) • BGP: • the interdomain routing protocol used on the Internet • routing domains is called Autonomous Systems (ASes), e.g. AT&T. • ASes: • announce the prefixes that they own (IP address ranges, e.g. 12.1.1.0/24) to its neighboring ASes. • announce the prefixes that it learns from each of its neighbors to its other neighbors. Presenter: Lan Gao

6. Intra-AS and Inter-AS Routing: Example The route from A.d to B.b: intra-AS and inter-AS path segments. Source: Computer Networking: A Top-Down Approach Featuring the Internet Presenter: Lan Gao

7. Security Issues in Interdomain Routing • ASes are not authenticated • Paths are not authenticated • Addresses are not authenticated • What is addressed in the paper? • Validate an AS’s authority to advertise a prefix Presenter: Lan Gao

8. Origin Authentication • Goal: • Provide evidence (cryptographically strong authentication tags) of the relations between organizations, ASes, and prefixes. BGP Speakers Address Advertisements Validated Address Advertisements Evidence Presenter: Lan Gao

9. Address Delegation • The IPv4 address space is governed by IANA • IANA delegates parts of the global address space to organizations • Each organization may further • Delegate some or all of the received address space to any organization it desires • Assign its address space to the AS in which the addresses reside Presenter: Lan Gao

10. Address Delegation: Example • AT&T delegates 12.1.1.0/24 to ALPHA • AT&T assigns 12.0.0.0/8 to AS7018 • Longest prefix matching for 12.1.1.0/24 • Address announcements: ASes advertise the set of prefixes that they originate (prefix, ASN) Presenter: Lan Gao

11. Definition: Organization • ASN = { 1, 2, …, K }, where currently K = 216 • E.g. AS7018, AS29987 • S = { all BGP speaking organizations } • E.g. AT&T, ARIN, ALPHA, BETA • ASN(C) = { AS # currently assigned to C } • E.g. for C = ALPHA, ASN(C) = { AS29987 } • O = S  { IANA }  { other prefix registries } Presenter: Lan Gao

12. IPA = { 0, 1 }l, where l = 32/64 for IPv4/IPv6 Address Prefixes: x/j x is a j bit number, and j  [ 0, l ], e.g. 128/8 x/j = { xy | y is a (l-j) bit number } IPA = /0 Definition: Prefixes x/j x1/(j+1) x0/(j+1) Disjoint Union Superset subprefix & superprefix Presenter: Lan Gao

13. /0 0/1 1/1 00/2 01/2 10/2 11/2 00/32 11/32 Prefix Tree of IPA Presenter: Lan Gao

14. Definition: delegation policy • For a given prefix y/k and an organization C: • (C, y/k, n): C assigns y/k to an ASN n • (C, y/k, C’): C delegates y/k to C’ • (C, y/k, R): C declares y/k as RESERVED • (C, y/k, U): C’s delegation or assignment of y/k is UNAUTHENTICATED • C may perform zero, one, or more of the above options • The set of triples is C’s delegation policy for y/k Presenter: Lan Gao

15. Subtree Semantics • Definition: • a property of a prefix x/j implies the same property for all of the subprefixes of x/j • Consider the previous delegation policy: • Delegations, RESERVED and UNAUTHENTICATED declarations have subtree semantics • Assignments do not have subtree semantics Presenter: Lan Gao

16. Delegation Graphs • A directed graph G = (V, E) • V=O  ASN  R  U   • E={(x, y/k, z)} • Example: • V = { IANA, AT&T, … } • E = {(IANA,12.0.0.0/8,AT&T), … } • Definition: • Ownership Source • Assignment Edge • ASN-respecting Presenter: Lan Gao

17. Valid & Faithful • A directed path is valid for y/k if: • The ownership source is IANA • The path is monotonic • The path is acyclic • The ass edge is labelled y/k and is ASN-respecting • C’s delegation policy is faithful for y/k if there is at most one triple in the form: • (C, y/k, n) • (C, x/j, C’), (C, x/j, U), or (C, x/j, R), where x/j is a superprefix of y/k Presenter: Lan Gao

18. Verification of Origin Announcements • OAs are verified by Origin Authentication Tags (OATs): • A delegation path • A set of delegation attestation, one for each edge in the path • An ASN Ownership Proof Presenter: Lan Gao

19. Simple Delegation Attestation • A signature by C for a prefix x/j: • { ( C, x/j, FC(x/j) ) }C • A signed statement (by C’s key) binding the prefix (x/j) to an organization identifier (FC(x/j)) • The simple delegation attestation for D(C): { ( C, x1/j1, FC(x1/j1) ) }C, { ( C, x2/j2, FC(x2/j2) ) }C, …, { ( C, xs/js, FC(xs/js) ) }C Presenter: Lan Gao

20. The delegation path for 12.1.1.0/24 is: (IANA, AT&T, ALPHA, AS29987) The delegation attestation for the path are: [(IANA, 12.0.0.0/8, AT&T)]IANA, [(AT&T, 12.1.1.0/24, ALPHA)]AT&T, [(ALPHA, 12.1.1.0/24, AS29987)]ALPHA SDA: An Example Presenter: Lan Gao

21. Authenticated Delegation List • C creates a single list of all of its delegations and sign that list [ { ( C, x1/j1, FC(x1/j1) ) }, { ( C, x2/j2, FC(x2/j2) ) }, …, { ( C, xs/js, FC(xs/js) ) } ]C • If C delegates xi/ji to B • C signs all of the delegations it makes to everyone. • B advertises xi/ji and provides this attestation Presenter: Lan Gao

22. The delegation path for 12.1.1.0/24 is: (IANA, AT&T, ALPHA, AS29987) The delegation attestation for the path are: [(IANA, 12.0.0.0/8, AT&T), (IANA, 64.0.0.0/8, ARIN)]IANA, [(AT&T, 12.1.1.0/24, ALPHA), (AT&T, 64.1.0.0/16, AS7018), (AT&T, 12.0.0.0/8, AS7018)]AT&T, [(ALPHA, 12.1.1.0/24, AS29987)]ALPHA ADL: An Example Presenter: Lan Gao

23. AS Authenticated Delegation List • C breaks up the entire list into several lists and signs each of the smaller lists. • The list is splitted according to those prefixes: • delegated to the same organization or • assigned to the same AS number • If C delegates xi/ji to B • C signs all of the delegations it makes to B. • B advertises xi/ji and provides this attestation Presenter: Lan Gao

24. The delegation path for 12.0.0.0/8 is: (IANA, AT&T, AS7018) The delegation attestation for the path are: [(IANA, 12.0.0.0/8, AT&T)]IANA, [(AT&T, 64.1.0.0/16, AS7018), (AT&T, 12.0.0.0/8, AS7018)]AT&T AS ADL: An Example Presenter: Lan Gao

25. Authenticated Delegation Tree • C creates a Merkle hash tree: • The values of the leaves: ( C, x/j, FC(x/j) ) • The values of each internal node: H( L, R ) • If C delegates xi/ji to B • C only signs the root [h0]C • C provides the value of the children of all of the nodes on the path in the Merkel tree from the root to ( C, xi/ji, B ) • B advertises xi/ji and provides this attestation Presenter: Lan Gao

26. The delegation attestation for (C, x2/j2, B): {H(L12, R34)}C, H(L3, R4), (C, x1/j1, A) ADT: An Example H(L12, R34) H(L1, R2) H(L3, R4) (C, x1/j1, A) (C, x2/j2, B) (C, x3/j3, D) (C, x4/j4, E) Presenter: Lan Gao

27. User Dictionary Query Attestations Yes/No + Proof Directory Authenticated Delegation Dictionaries - 1 • The model for an authenticated dictionary • An Authenticated Dictionary for C: • Element: (C, y/k, FC(y/k)) • The search key: address prefixes • Data Structure: balanced 2-3 trees, with leaves sorted based on the search key Presenter: Lan Gao

28. x/j x0/(j+1) x1/(j+1) x00/(j+2) x01/(j+2) x10/(j+2) x11/(j+2) Authenticated Delegation Dictionaries - 2 • Prefix Tree rooted at x/j: • A total order of the prefixes: x/j < xy/(j+k) < z/j • The smallest element: x/j The largest element: x1l-j/l Presenter: Lan Gao

29. k0H(L123,R45) k1 k2H(L1,M2,R3) k3H(L4,R5) (C, x1/j1, A) (C, x2/j2, B) (C, x3/j3, D) (C, x4/j4, E) (C, x5/j5, F)) Authenticated Delegation Dictionaries - 3 • ADD for C: • The delegation attestation for (C, x2/j2, B): • The signed root: {k0H(L123, R45)}C • The value of the children of the nodes of the path: k3H(L4, R5), (C, x1/j1, A), (C, x3/j3, D) • The search tree path Presenter: Lan Gao

30. Approximating IP Address Delegation • Goal: • To understand how and by whom delegation occurs • Sources: IANA and BGP announcements • What do we learn? • Dense (16 orgs delegate 80% address space) • Stable (10-30% movement in 5 months) Presenter: Lan Gao

31. Approximation Example Presenter: Lan Gao

32. Delegation in the ApproximateDelegation Graph • The overwhelming number of delegations are being performed by a relatively few ASes/organizations Presenter: Lan Gao

33. Trace-Based Simulation • The OAsim simulator: • Models the operation of a single BGP speaker • Accepts timed BGP UPDATE streams • Computes bandwidth/computational costs • Implements four service designs • Dataset: • Obtained from RouteViews • A trace of BGP updates over a 24 hour period Presenter: Lan Gao

34. Computational Costs Presenter: Lan Gao

35. Bandwidth Costs Presenter: Lan Gao

36. Conclusions • OA is important in inter-domain routing • trace and validate the delegation of address usage • Formalization • semantics of address ads & proofs of delegation • Modeling • the current IPv4 address delegation: dense & static • Performance Evaluation • consolidate proofs by delegator to reduce costs Presenter: Lan Gao

37. Comments? Questions ? Presenter: Lan Gao