Michael Schapira*

*School of Computer Science and Engineering, Hebrew U

*Hebrew U’s Cybersecurity Research Center*Fraunhofer Project Center for Cybersecurity @

Hebrew U

(How) Can WeSecure Internet Routing?

2

• The Internet infrastructure is alarmingly insecure

• Designed without security in mind

• Security not even on the horizon (yet!)

3 stories, 1 theme

3

• Naming/addressing with the Domain Name System (DNS)– DNS = the Internet’s phone book– google.com = ?

• Routing with the Border Gateway Protocol (BGP)– BGP = the Internet’s google maps / Waze

• The Network Time Protocol (NTP)– NTP = the Internet’s global clock

3 stories, 1 theme

• The Internet is becoming ever-more important

• Yet, today’s Internet is surprisingly fragile– suboptimal, insecure, unpredictable, …

• And new challenges just keep piling up…

The Internet Only Just Works

Applications:

Internet infrastructure:

routing, congestion control, naming, …

(TCP/IP, BGP, DNS, OSPF, ECMP,…)

Technologies:

constant innovation

stagnant!

constant innovation

Why Only Just Works?

6

• Replace the Internet!– Throw cryptography at the problem– Top-down approach– BGPSEC, DNSSEC, …

• Security not even on the horizon because of– meager benefits in partial adoption– costly changes to network (e.g., new hardware)– much room for human error– …

Today’s Approach toSecuring the Internet

7

“The Bureau … is charged with improving the defense of national infrastructures critical to the continuation of normal life in the State of Israel and to protect them … from cyber attack” (INCB website)

“Douglas Maughan, cybersecurity research program manager for the DHS’s Science and Technology Directorate ... had little luck convincing ISPs and router vendors to take steps to secure BGP.” (“The Internet’s Biggest Security Hole”, WIRED 2008)

Can Israel be Secure?

8

• Unique opportunity– focus on nation-state security (INCB, BSI)– strong foundations (research, gov’t)

• But… a paradigm shift is needed

Yes We Can

9

3 (Sub-)ProjectsHermes

Securing Internet Routing with BGPDionysus

Securing Naming/Addressing with DNS

ChronosSecuring Network Time with NTP

10

• Internet routing as an example

• A very appropriate example…

This Talk

11

• Part I: Internet routing with BGP• Part II: BGP (in)security• Part III: Today’s approach is

failing• Part IV: How can BGP be made

secure?

(if time permits, I’ll also talk about anonymity on the Internet)

This Talk

• New approaches, new models (security measures, economic incentives, …)– empirical validation– see survey of 100 network operators

in [Gill-S-Goldberg, CCR 2012]

• Theoretical impossibility results…– even for simple models…

• Extensive experimental analysis– custom algorithms: optimized, parallelized– multiple sensitivity and robustness tests– see report on new algorithms and experimental framework in

[Gill-S-Goldberg, CCR 2012]

Tackling These Questions

13

Disclaimer

The views and opinions expressed in this presentation are those of the

presenter and do not necessarily reflect the official views or position

of the Hebrew University or any agency of the Israeli government.

Part I: Internet Routing with BGP

14

The Internet Ecosystem

Google

Verizon

Comcast

AT&T

Over 50,000 Autonomous Systems (ASes)

Range from small businesses and schools (e.g., HUJI) to large,

multinational, corporations (e.g., Google, Microsoft)

Inter-Net:A Network of Networks

AS-level topology– Nodes are Autonomous Systems (ASes)– Edges are links and business relationships

1

2

34

5

67

Client Web server

Autonomous Systems

• ASes sign bilateral long-term contracts.– How much traffic to carry – Which destinations to reach – How much money to pay

• Neighboring pairs of ASes typically have:– a customer-provider relationship, or– a peering relationship.

peer provider

customerpeer

The Commercial Internet

• More types of business relationships…

• Content providers (e.g., Google) can have their own backbone network

• Content Delivery Networks (CDNs)…

• Internet exchange points (IXPs)…

Real Life is More Complex…

Google

Verizon

Comcast

AT&T

• Interdomain: Between ASes– across different entities

• Intradomain: Within a single AS– all network devices belong to the same entity

Intradomain vs. Interdomain

Google

Verizon

Comcast

AT&T

• Interdomain routing establishes routes between ASes

• Currently handled by the Border Gateway Protocol (BGP)

Interdomain Routing with BGP

BGP ≠ Shortest-Path Routing!

Google

Verizon

Comcast

AT&T

I want to avoid routes through Comcast if

possible I won’t carry traffic between

AT&T and Verizon

I want a cheap route I want

short routes

BGP is Crucial!

• The glue that holds the Internet together

• A few anecdotes:– Almost 50% of VoIP disruptions are BGP-related!– Every year or so a serious BGP-related Internet

outage makes the news!– BGP is notoriously vulnerable to attacks…

AS 2

AS 4

AS 1 AS 3

AS 5

AS 1, IP addresses X

AS 1, IP addresses X

AS 4, AS 3, AS 1, IP addresses X

AS 2, AS 1, IP addresses X

IP Prefix

• The destination announces itself to its neighbors• Routes to the destination are built hop-by-hop as

reachability information propagates through the network• Route selection based on local routing policies

?

BGP Routing Overview

AS 3, AS 1, IP addresses X

$

Verizon

43284

UPC Init 7 AGZurich

20984 $

$

$ $

IP Prefix

customer

peer peer

provider

Routing Model (Gao-Rexford)

Verizon

43284

UPC Init 7 AGZurich

20984

UPC, Prefix UPC, Prefix

Init 7, UPC, Prefix

43284, Init 7, UPC, Prefix

Verizon, UPC, Prefix

IP Prefix

$ $

1) Prefer revenue generating routes2) Prefer shorter routes

Routing Model (Gao-Rexford)

Verizon

43284

UPC Init 7 AGZurich

20984

20984,Verizon, UPC, Prefix

IP Prefix

$ $

XLosing $$

UPC, Prefix UPC, Prefix

Init 7, UPC, Prefix

43284, Init 7, UPC, Prefix

Verizon, UPC, Prefix

1) Prefer revenue generating routes2) Prefer shorter routes3) Do not carry transit traffic for free

Routing Model (Gao-Rexford)

• Thm [Gao-Rexford]: In the Gao-

Rexford model, BGP dynamics are guaranteed to converge to a unique stable routing configuration.

BGP Routing Outcomes

Part II: BGP (In)Security

AS 2

AS 1

I’m YouTube

No, I’m YouTube!

30

Repeated attacks against major financial institutions and governments in Europe and

the US

An Anecdote

31

Rare Incident? Not Really!

• To disconnect victim from the Internet (large corporation, nation state, …)

• To be a man-in-the-middle(snoop on traffic, tamper with traffic, …)

• To impersonate the victim• To hide under someone else’s identity• To attack protocols/mechanisms that

utilize Internet routing (BitCoin, DNS, …)

• …

Why Do this?

Another AnecdoteFebruary 2008: Pakistan Telecom hijacks YouTube!

YouTubePakistan Telecom

The Internet

I’m YouTube:IP addresses: ****

What should have happened…

YouTubePakistan Telecom

Xdrop packets

I’m YouTube:IP addresses: ****

Another Anecdote

What did happen…

YouTubePakistan TelecomPakistanTelecom

No, I’m YouTube!IP addresses: ****

I’m YouTube:IP addresses: ****

Another Anecdote

The InternetAS 1 AS 666

My IP addresses are ***

No, my IP addresses are ***!

Attack: Hijacking IP Addresses

The InternetAS 1 AS 666

Attack: Manipulating the BGP Path

AS 1 is my neighbor

My IP addresses are ***

• The attacker needs– a router with a BGP session to an AS–… configured to originate the prefix

• This could happen because– a network operator makes configuration

mistake– an insider launches an attack– an outsider breaks into the router–… or a black market of BGP routers…

Who Can Launch Such an Attack?

Naïve attack: Announce the shortest path I can to all

neighbors

a

$m

Is the Naïve Attack Optimal?Can’t lie about my business

relationship with a, so I might as well announce the shortest path I can.

Naïve attack: Announce the shortest path I can to all

neighbors

a

$m

Sometimes longer paths

are better!

Thm: It is NP hard to find (or even well approximate) the optimal attack. So, our results underestimate damage.

Sometimes not announcing is

better!

Is the Naïve Attack Optimal?Can’t lie about my business

relationship with a, so I might as well announce the shortest path I can.

• The victim AS doesn’t necessarily see the problem

• May not cause loss of connectivity– e.g., if the bogus AS snoops and redirects

• Even if detected, how can such attacks be stopped?– a polite phone call?– the “wall metaphor” is not appropriate here

• How can this be rectified?

Attacks on BGP are Hard toDetect/Prevent

AS 1

AS 3

v AS 2

m

IP

v, Prefix v, Prefix

m

IP Prefix

v

m, Prefixm, Prefix

A secure database maps IP prefixes to owner ASes

Proposed Solution: The Resource Public Key

Infrastructure (RPKI)

AS 1

AS 3

v AS 2

m

IP

v, Prefix v, Prefix

m

IP Prefix

v

m, v, Prefixm, v, Prefix

Does RPKI Solve the Problem?

Public Key Signature: Anyone who knows v’s public key can verify that the message was sent by

v.

a1

a2

v a3

m

IP Prefix

a1: (v, IP addresses X)

a1: (v, IP addresses X)

m: (a1, v, IP addresses X)

BGPSEC to the Rescue!

Part III:Why Today’s Approach is Failing

• Goldberg-S-Hummon-Rexford, SIGCOMM 2010• Gill-S-Goldberg, CCR 2012• Lychev-S-Goldberg, SIGCOMM 2013• Gilad-Cohen-Herzberg-Schapira-Shulman, NDSS 2017

• Step 1: Create a secure DB (<6%)– RPKI: Organizations -> Internet addresses

• Step 2: Replace BGP (0%)– BGPsec

BGP Security is a Distant Dream

• RPKI: Resource Public Key Infrastructure• Intuition: a secure “phone book”• Maps IP addresses to ASes that own them.

(AS number, IP addresses)

RPKI Revisited

• RPKI: Resource Public Key Infrastructure• Intuition: a secure “phone book”• Maps IP prefixes to ASes that own them.• Very low adoption

RPKI Revisited

Discarding Bogus Routes with RPKI

AS 1

v, IP addresses: ****

m

IP addresses

v

m, IP addresses: ****

According to RPKI, m’s a

liar!

Our answers rely on a combination of

1. a survey network practitioners

2. extensive empirical analyses

50

Why is RPKI adoption so slow?

• Hypothesis I: technical and logistic barriers (e.g., inter-organizational dependencies)

• Hypothesis II: Insufficient value

51

Nope, most of the Internet could adopt tomorrow!(check out roalert.org! [Yossi Gilad, Daniel Davidovich])

Indeed. The chicken and egg problem…

(Almost) no one bothersto register its addresses into

RPKI(< 6%)

(Almost) no one usesRPKI to filter “bad” routes

(?)

Why is RPKI adoption so slow?

Route-Origin Validation (ROV): use the RPKI to discard route-advertisements from

unauthorized ASes

BGP Routers

RPKI cache

RPKI

Autonomous System

52

But how can we tell whether an AS employs RPKI-based filtering?

We gain empirical insights regarding ROV enforcement via RPKI-invalid BGP advertisements

We monitored BGP paths from multiple vantage points afforded by 44 Route Views sensors²

² http://www.routeviews.org/ 53

ROV Adoption Measurements

Measurements: Non-Filtering ASes

ASes that propagate invalid BGP advertisements do not perform filtering

*This presentation provides examples based on empirical data.

54

42926

1299

RVsenso

r

RVsenso

r

IP addresses Y

9121

1239 4637

15003 6416IP addresses

X AS 15003 and AS 42926 advertise in BGP the RPKI-invalid IP addresses X and Y

6939

Measurements: Non-Filtering ASes

ASes that propagate invalid BGP advertisements do not perform filtering

55

15003IP addresses

X

42926

1299

RVsenso

r

RVsenso

r

IP addresses Y

Route Views sensor observes “bad” route to XAS path: 4637, 6416, 15003

9121

6939

1239 4637

6416

Route Views sensor observes “bad” route to YAS path: 6939, 1299, 9121, 42926

Measurements: Non-Filtering ASes

ASes that propagate invalid BGP advertisements do not perform filtering

56

15003IP addresses

X

42926

1299

RVsenso

r

RVsenso

r

IP addresses Y

9121

6939

1239 4637

6416

ASes that don’t filter invalid advertisements colored red

Measurements: Filtering ASesSeek ASes that advertise both “good” & “invalid” routes.Conclude that an AS performs ROV if it discards “bad” advertisements, but relays “good” ones, from 3 origins

42926

1299

RVsenso

r

RVsenso

r

IP addresses Y

9121

6939

1239

IP addresses Y

AS 42926 announces another BGP advertisement forprefix Y

4637

57

15003IP addresses

X

6416

15003 6416

Measurements: Filtering ASes

42926

1299

RVsenso

r

RVsenso

r

IP addresses Y

Route Views sensor observes ``good’’ route to: YAS path: 4637, 1239, 9121, 42926

9121

6939

1239 4637

IP addresses Y

AS 42926 announces another BGP advertisement forprefix Y

58

IP addresses X

Seek ASes that advertise both “good” & “invalid” routes.Conclude that an AS performs ROV if it discards “bad” advertisements, but relays “good” ones, from 3 origins

15003 6416

Measurements: Filtering ASes

42926

1299

RVsens

or

RVsens

or

185.70.84.0/24

9121

6939

1239 4637

79.98.130.0/24

Conclude: AS 1239 receives adv. from AS 42926, but did not relay the invalid one(only non-red AS on legitimate adv. path)

42926

1299

RVsenso

r

RVsenso

r

9121

6939

1239 4637

59

Seek ASes that advertise both “good” & “invalid” routes.Conclude that an AS performs ROV if it discards “bad” advertisements, but relays “good” ones, from 3 origins

Measurements: ResultsOur measurement techniques provide a view of ROV enforcement amongst the ASes at the core of the Internet

– since ASes at the core are likely to be on the paths covered by the Rout Views sensors At least 80 of top 100

ISPs do not perform ROV

60

Survey ResultsAn anonymized survey of over 100 network operators and security practitioners• advertised in different mailing lists, including ‘closed’ lists• 80% of respondents are network operators/managers and most of the

others are security/networking consultants

Do you apply RPKI-based route-origin

validation?

61

• ~30% of information in RPKI is “incorrect” as a result of human error…

• RPKI-based filtering disconnects legitimate destinations! the very same “attack” RPKI aims to

prevent

• RPKI does not even always protect those in the system

Also, (Justified) Mistrust in RPKI!

Obstacles to Deployment:Human Error

Concern about mistakes in the RPKI also reflected in our survey results:

What are your main concerns regarding executing RPKI-based origin authentication in your network?

63

• We ran simulations to quantify security:– empirically-derived AS-level network from CAIDA

• Including inferred peering links [Giotsas et al., SIGCOMM’13]

– using the simulation framework in [Gill et al., CCR’12]

• We measured the attacker success rate– in terms of #ASes attracted – for different attack scenarios– for different ROV deployment scenarios– averaged over 1M randomly chosen attacker/victim pairs

64

Quantify Security in Partial Adoption

Quantify Security in Partial Adoption

Adoption by the top 100 ISPs makes a huge difference!

• Comparison between two scenarios:– today’s status, as reflected by our

measurements – all top 100 ISPs perform ROV

• Each other AS does ROV with fixed probability

65

Bottom line:

ROV enforcement by the top ISPs is both necessary and sufficient for substantial

security benefits from RPKI

66

Quantify Security in Partial Adoption

67

BGP RPKI (origin

authentication)

BGPSEC

S

4323,2828, FB, prefix

S

2828, FB, prefix

S

SP, 4323, 2828, FB, prefix

• In deployment• Crypto done offline

• In standardization• Crypto done online

What does (partially-deployed) BGPSEC offer over RPKI?(Or, is the juice worth the squeeze?)

Secu

rity

Ben

efits

(Ju

ice)

BGP and BGPSECcoexistence

Road to BGPSEC full-deployment is very tricky because introducing

security only partially introduces new vulnerabilities Not fully deployed BGPSEC provides only meagre benefits

over RPKI

Landscape of BGP Defenses

A

Sprint

2828

4323

DSiemens

IP addresses X

P/S

P/S

P/S

P/S

Should Sprint choose the long secure path ORthe short insecure one?

P/S

P/S

?Secure ASes must accept

legacy insecure routes

Depends on the interaction between BGPSEC and routing policies!

RPKI

A, DIP addresses X

What Happens in Partial BGPSEC Deployment?

S

4323,2828, D,

prefix

S

2828, D, prefix

S

SP, 4323, 2828, D, prefix

A

Sprint

2828

4323

DSiemens

69.63.176.0/24

P/S

P/S

P/S

P/S

Should Sprint choose the long secure path ORthe short insecure one?

Secure ASes must accept

legacy insecure routes

A, DIP addresses X

Before attack, Sprint has a legitimate secure routeDuring attack, Sprint downgrades to a bogus route

What Happens in Partial BGPSEC Deployment?

• BGPSEC in partial deployment introduces new vulnerabilities1. “protocol downgrade attacks”2. security not monotone!3. instabilities

• BGPSEC provides meagre benefits over RPKI even if over 50% of ASes adopt!– using our security measure

Is the Juice Worth the Squeeze?

Part IV:How Can We Secure BGP Routing

• Cohen-Gilad-Herzberg-Schapira, HotNets 2015• Cohen-Gilad-Herzberg-Schapira, SIGCOMM 2016• Cohen-Gilad-Herzberg-Schapira-Shulman, upcoming

Hermes:Securing Internet Routing (BGP)

Constraints on design space:• Easily deployable– No changes to routers– Software only

• Fully automated– No human errors

• Significant benefits in partial deployment

Wanted:A New Paradigm for BGP

Security

Hermes Components

• Automating RPKI certification with DISCO

• Path-end validationd

d IP addresses

certified

DISCO: IntuitionOrganization

alNetwork

AgentRouter

RegistrarC1C2

I own Internet (IP) addresses X

Prove it!

DISCO: Intuition

Organizational

Network

Organizational

Network

AgentRouter

AgentRouter

Registrar

Securing routing via insecure routing?

DISCO Certification Success Rate

r PO Days till Certification

PA 1000s Years till Certification

3 0.3 16.46 10-4 0.13

5 0.26 19.19 2.1*10-6 6.66

7 0.23 22.02 4.2*10-8 323

9 0.2 25.01 9*10-10 15,243

11 0.18 28.22 1.9*10-11 706,182

13 0.16 31.68 4.2*10-13 32,300,076

15 0.14 35.41 9.3*10-15 1,468,884,419

Path-End Validation

• An easily deployable alternative to BGPSEC

• Significant benefits in partial deployment

Path-End Validation• RPKI provides origin authentication• Path-end validation also authenticates the “last hop”

A radical departure from BGPSEC

dv

a

RPKI

Did d approve reaching it via

v?BGPSEC Design Choices and Summary of Supporting Discussions

draft-sriram-bgpsec-design-choices-08

AS 11.2.3.0/24

Router

AS 24.5.6.0/24

Router

The Internet

RPKI Repository

AS 10

AS 20

Path-End Validation

AS 11.2.3.0/24

Router

AS 2

Router

The Internet

RPKI Repository

AS 10

AS 20

1020

Path-End Validation

AS 11.2.3.0/24

Router

AS 2

Router

The Internet

RPKI Repository

AS 10

AS 20Path-end Records

ip as-path access-list as1 deny _[^(10|20)]_1_ip as-path access-list allow-all permit

Path-End Validation

Router Configuration

• Compatible with today’s routers• Only one rule per-AS

– An order of magnitude less rules than origin authentication with RPKI

The implementation can be found at: https://github.com/routingsec/pathend

AS 2

Router

ip as-path access-list as1 deny _[^(10|20)]_1_ip as-path access-list allow-all permit

Adopter

Legacy

Provider

Customer

Legend

• AS 666 wants to attract AS 3’s traffic to IP prefix 1.2.3.0/24, but…– It can’t lie about business relationship– It can’t announce that it owns the prefix or is

AS 1’s neighbor– It has to launch 2-hop attack: (666,2,1,prefix)

AS 3

Attacker,

AS 666

Victim, AS 1

1.2.3.0/24AS 2

4

4.5

3.5

MANY CLIENTS ARE JUST 1 AS-

HOP AWAY FROM CONTENT

Intuition for Path-End Validation

• Path-end validation is not restricted BGPSEC!– Offline vs. online– Keep message format and use today’s routers

• Important implications for security– AS 666 launches a next-AS attack against AS 1• Not prevented by BGPsec• Prevented by path-end validation

AS 3

Attacker,

AS 666

Victim, AS 1

1.2.3.0/24AS 2

Adopter

Legacy

Provider

Customer

Legend

Path-End Validation vs. BGPSEC

Simulation Framework• Empirically-derived AS-level network from CAIDA – Including inferred peering links

[Giotsas et al., SIGCOMM’13]

• Evaluate fraction of ASes an attacker can attract– Under different adoption scenarios– Under different attacks

• Using the simulation framework in [Gill et al., CCR’12]

Simulation Results

Simulation Results

Simulation Results

Benefits from Local Deployment

Impact of k-Hop Attacks

BGP(no authentication)

Origin authentication (RPKI)Path-end validation

2-hop validation

Additional Results• Large content providers are better

protected

• Path-end validation mitigates high profile incidents

• Security monotone– BGPsec is not [Lychev et al.,

SIGCOMM’13]

Summary• Today’s agenda for securing BGP routing

faces significant hurdles

• A new paradigm for securing Internet routing– Readily deployable– Effective under very partial deployment

Thanks!

Measuring and Mitigating AS-level Adversaries Against Tor

Rishab Nithyanand, Oleksii Starov, Adva Zair, Michael Schapira, and Phillipa Gill, NDSS 2016

95Source AS Destination AS

Anonymity on the Internet• Challenge: By observing Internet traffic

one can infer who is talking to whom– Meta data is the message!– Track communications over time…

• …behaviors, interests, activities• Tor aims to solve this

TorEntry Exit

Middle

Tor circuit is constructed out of three Tor routers/relays

Does not know source

Does not know destinationWhich user is visiting the site?

Internet routing dynamics make timing attacks easier than you’d

think!

Timing Attacks & Routing

97Source AS

AS1

AS2

AS3 AS4

AS5

Entry relay Exit relay

Destination AS

AS2

98

Method:• Use VPN to connect to 200 sites (100 popular, 100 likely censored)

through Tor• Examine AS-level paths between source and destination and chosen

entry/exit relays.

53% of sites have at least some content delivered over a vulnerable Tor circuit

How often does Tor pick a vulnerable path?

Solution: Astoria• Choose an entry/exit relay to avoid attackers

– Usually there is such an option• Otherwise, use a linear program to minimize damage

– Choose probabilistically to minimize the amount of data observed by an adversary over time

Additional considerations:• Path computations need to be done on the client• ASes may collude (e.g., sibling ASes, state-level actors)• Minimize performance impact

– Cannot pre-construct circuits as in vanilla Tor • Being a good network citizen: don’t overload popular

relays

99

100

Fraction of sites with content delivered over vulnerable circuits decreases from 53% to 8% with Astoria

Astoria: Results

101

What’s next?• Interview with cryptographer Tibor

Jager on TLS, attacks, and countermeasures

• An Interview with That One Privacy Guy- The Man Behind That One Privacy Site

• Interview with Researcher Thyla Van Der Merwe on TLS and Online Privacy