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Security Issues of SIP

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Master Thesis Electrical Engineering Thesis no: MEE10:74 June 2010 BLEKINGE INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING DEPARTMENT OF TELECOMMUNICATION SYSTEMS Security Issues of SIP MASTER‘S THESIS Name: Gulfam Asghar Email: [email protected] Name: Qanit Jawed Azmi Email: [email protected] Blekinge Institute of Technology School of Engineering Supervisor: (Doktorand) Mr. Karel De Vogeleer Examiner: Prof. Dr. Adrian Popes Table of Contents Abstract ........................................................................................... 5 Objectives ........................................................................................ 5 Acknowledgments ........................................................................... 5 1 Introduction .................................................................................. 6 1.1 Background .............................................................................. 6 1.2 Problem description .................................................................. 7 1.3 Scope of work ........................................................................... 9 1.4 Test Environment ..................................................................... 9 1.5 Outline .................................................................................... 10 2 Overview of SIP & Security Considerations ............................. 11 2.1 The Evolution Of SIP protocol ................................................ 11 2.2 Basics of SIP protocol ............................................................ 12 2.2.1 Definition ......................................................................................... 12 2.2.2 Basic functionality of a SIP based VOIP system ............................. 12 2.2.3 Overview of Operation (A Simple Call Setup Example) ............. 14 2.2.4 SIP Call with Proxy Servers ............................................................ 22 2.2.5 The SIP Registration Process ......................................................... 24 2.2.6 Instant Messaging with SIP ............................................................. 25 2.2.7 Message Transports in SIP ............................................................. 27 2.2.7.1 UDP Transport ............................................................................. 27 2.2.7.2 TCP Transport ............................................................................. 28 2.2.7.3 SCTP Transport .......................................................................... 30 2.3 Threats to SIP Security .......................................................... 31 2.3.1 Registration Hijacking .................................................................... 32 2.3.2 Impersonating a server .................................................................. 33 2.3.3 Message Tampering ...................................................................... 34 2 2.3.4 Session Tear Down ....................................................................... 36 2.3.5 Denial of Service (DoS) Attacks ..................................................... 37 3 SIP with Firewall/NAT Traversal ................................................ 39 3.1 Firewalls and Network Address Translators (NAT) ................. 39 3.1.1 Internet Firewalls ............................................................................. 40 3.1.1.1 Packet filtering Gateways ............................................................ 40 3.1.1.2 Circuit Level Gateways ................................................................ 43 3.1.1.3 Application Level Gateways ......................................................... 44 3.1.2 Network Address Translators (NAT) ................................................ 44 3.1.2.1 NAT Operation .............................................................................. 45 3.1.2.2 Basic NAT Traversal ..................................................................... 46 3.1.2.3 NAPT Traversal ............................................................................ 47 3.1.2.4 NAT behaviors and classifications ................................................ 48 3.1.2.4.1 Symmetric Binding ......................................................................49 3.1.2.4.2 Full-cone Binding .........................................................................49 3.1.2.4.3 Restricted-cone Binding ..............................................................49 3.1.2.4.4 Port-restricted-cone Binding ........................................................49 3.1.2.5 Conclusions related to NAT .......................................................... 50 3.2 NAT/Firewall Traversal with SIP: ISSUES .............................. 50 3.2.1 NAT Traversal with SIP signaling ................................................... 50 3.2.2 SIP related media with NAT traversal ............................................ 51 3.3 NAT/Firewall Traversal with SIP: SOLUTIONS ...................... 51 3.3.1 Symmetric response ...................................................................... 51 3.3.2 Connection Re-use ........................................................................ 52 3.3.3 Symmetric RTP .............................................................................. 52 3.3.4 Simple Traversal of UDP through NAT (STUN) ............................. 52 3.3.5 Traversal Using Relay NAT (TURN) .............................................. 52 3.3.6 Interactive Connectivity Establishment (ICE) ................................. 53 3 3.3.7 Application Layer Gateway (ALG) .................................................. 53 3.3.8 Middlebox/MlDCOM (Middlebox Communications Protocol) ......... 53 3.3.9 Universal Plug and Play (UPnP) .................................................... 54 3.3.10 Session Border Control (SBC) ..................................................... 54 4 Model test Scenario .................................................................... 56 4.1 Virtualization ........................................................................... 58 4.1.1 OS Level ........................................................................................... 58 4.1.2 Network Level ................................................................................... 60 4.2 Call Hijacking Demonstration .................................................. 63 4.2.1 Packet dumps collected via wireshark ............................................. 65 4.3 IPSec and Firewall Implementation ........................................ 68 4.3.1 Router R1-Karlskrona ..................................................................... 69 4.3.1.1 IPSec Tunnel ...................................................................... 69 4.3.1.2 Firewall based Access Control policies ............................... 70 4.3.2 Router R2-Ronneby ........................................................................ 73 4.3.2.1 IPSec Tunnel ..................................................................... 73 4.3.2.2 Firewall based Access Control policies ............................... 74 5 Summary & Conclusions ........................................................... 77 5.1 Summary ................................................................................ 77 5.2 Conclusions ............................................................................ 77 List of Figures ................................................................................ 79 References ..................................................................................... 81 Appendix ........................................................................................ 83 4 Abstract Voice over IP (VoIP) services based on Session Initiation Protocol (SIP) has gained much attention as compared to other protocols like H.323 or MGCP over the last decade. SIP is the most favorite signaling protocol for the current and future IP telephony services, and it‘s also becoming the real competitor for traditional telephony services. However, the open architecture of SIP results the provided services vulnerable to different types of security threats which are similar in nature to those currently existing on the Internet. For this reason, there is an obvious need to provide some kind of security mechanisms to SIP based VOIP implementations. In this research, we will discuss the security threats to SIP and will highlight the related open issues. Although there are many threats to SIP security but we will focus mainly on the session hijacking and DoS attacks. We will demonstrate these types of attacks by introducing a model/practical test environment. We will also analyze the effect and performance of some the proposed solutions that is the use of Network Address Translation (NAT), IPSec, Virtual Private Networks (VPNs) and Firewalls (IDS/IPS) with the help of a test scenario. Objectives The main objective of this master‘s thesis is to learn the security issues of SIP and their practical implications. The primary goal of this project is to present the SIP security issues and will analyze the performance of some proposed solutions i.e. NAT/firewall traversal. Acknowledgments We would like to thank our supervisor at the Blekinge Institute of Technology (Sweden), who has helped and guided us throughout this thesis work. Our everlasting gratitude and acknowledgements are for our parents for their moral support and encouragement throughout our study period at BTH. 5 1 Introduction 1.1 Background The Session Initiation protocol
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