VoIP Security* Professor Patrick McDaniel CSE545 - Advanced Network Security Spring 2011 *Thanks to Prof. Angelos Keromytis for materials for these lecture slides. CSE545 - Advanced Network Security - Professor McDaniel Page 1
Example of toll fraud attack • Break into company PBX ‣ use them to route calls of your customers ‣ this has actually happened http://www.theregister.co.uk/2006/06/08/voip_fraudsters_nabbed/ http://www.theregister.co.uk/2009/02/11/fugitive_voip_hacker_arrested/ “ Federal authorities yesterday arrested a Miami man who they said made more than $1 million in a hacking scheme involving the resale of Internet telephone service.” “In all, more than 15 Internet phone companies, including the one in Newark, were left having to pay as much as $300,000 each in connection fees for routing the phone traffic to other carriers without receiving any revenue for the calls, prosecutors said.” Systems and Internet Infrastructure Security Laboratory (SIIS) Page 2
What is VoIP/IMS? • Protocol(s) for voice communication over IP-based infrastructures ‣ use of the Internet itself is dependent on operator • Voice over IP: catch-all term for numerous kinds of media ‣ Generally applied to voice and conference oriented products and services, e.g., Skype • IP Multimedia Subsystem : industry standard for IP-based multimedia communications ‣ Video, ‣ Calendaring/scheduling ‣ File-sharing ‣ Collaborative editing, ... 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 3
VoIP in the marketplace • Basis for many products/services ‣ commercial: Vonage, 3, T -Mobile/UMA, T -Mobile@Home, ... ‣ free/semi-free: Skype, GTalk, MSN, Yahoo! IM, AIM, Gizmo, ... • Both enterprise- and consumer-oriented ‣ management simplification ‣ cost reduction • Various architectural models ‣ centralized vs. P2P ‣ open vs. closed Systems and Internet Infrastructure Security Laboratory (SIIS) Page 4
Useful Terms • codec - coder/decoder ‣ Program (not format) used to process media-specific data • SDP - session description protocol ‣ Standard for describing media session parameters Systems and Internet Infrastructure Security Laboratory (SIIS) Page 5
VoIP Protocols • Signaling • Dominant mechanisms ‣ Responsible for call setup and ‣ Session Initiation Protocol (SIP) management ‣ Unlicensed Mobile Access (UMA) ‣ Architectural and operational ‣ Others: Skype, Asterisk, GTalk/ components AIM ... • Principal/endpoint naming, IP ‣ Useful terms mapping, proxying, billing, ‣ codec - “coder/decoder” program access control, device (not format) used to process configuration/management, media-specific data customer support, QoS ‣ SDP - session description protocol is • Data transport a standard for describing media ‣ Codecs, transport protocols session parameters (typically RTP), QoS, content security signaling Systems and Internet Infrastructure Security Laboratory (SIIS) Page 6
Session Initiation Protocol (SIP) • IETF Standardized signaling for IMS ( among others ) ‣ Similar to HTTP ‣ Text-based ‣ Request/response structure ‣ Stateful - highly complex state machine ‣ TCP or UDP (port 5060) • Devices ‣ End-points (soft phones or hardware devices) ‣ Proxy servers (local services acting on behalf of phone) ‣ Registrars (local point to register with network) ‣ Redirect servers (redirects calls) ‣ Location server (VoIP HLR) Systems and Internet Infrastructure Security Laboratory (SIIS) Page 7
SIP Flow Systems and Internet Infrastructure Security Laboratory (SIIS) Page 8
SIP/RTP Call progress 1. Locate endpoint* [SIP] 2. Establish call [SIP] 3. Data Transfer [RTP] 4. Hangup [SIP] *not shown Systems and Internet Infrastructure Security Laboratory (SIIS) Page 9
Call forwarding Systems and Internet Infrastructure Security Laboratory (SIIS) Page 10
SIP Call Flow Systems and Internet Infrastructure Security Laboratory (SIIS) Page 11
Real-time Transport Protocol (RTP) • RTP is a pair of protocols designed to support applications with latency and jitter constraints ‣ Supports the tightly controlled delivery of stream data, ‣ E.g., require some hard or soft QoS (quality of service) • Protocols using ephemeral ports (1025-65535) ‣ RTCP (Real-Time Control Protocol) provides signaling between peers that measures and adjusts session to compensate for changing conditions ‣ RTP - the data channel that delivers the data • SDP sometimes used to describe the session requirements, as negotiated through SIP • Standards support a range of codecs, e.g., RFC 3016 .., Systems and Internet Infrastructure Security Laboratory (SIIS) Page 12
In reality... • Much “hidden” shared infrastructure ‣ DNS, web, NAT, TFTP , DHCP/PPPoE, Int/DiffServ, firewalls,... • Emergent properties ‣ example: web-based UI poisoning through SIP-field manipulation • Live aspect makes problems harder ‣ e.g., how can we filter voice spam based on content? 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 13
SIP Security • Largely the ad hoc application of existing general-purpose security mechanisms ‣ Authentication uses HTTP-style digest authentication ‣ TLS - when TCP is used ‣ S/MIME - used to encode/secure payloads ‣ IPsec - can be used to secure any protocols run over IP ‣ Secure Real-time Transport Protocol (SRTP) - crypto extensions to protect real-time sessions, e.g., encrypt the voice channel • Implication : security largely pushed on infrastructure Systems and Internet Infrastructure Security Laboratory (SIIS) Page 14
SIP authentication 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 15
Unlicensed Mobile Access (UMA) • Route GSM calls over the Internet (or a public network) ‣ (usually) transparent handover between GSM and UMA • Popular with cellphone providers ‣ T -Mobile USA, Orange France, ... • Benefits ‣ reduce need to install expensive cell towers / upgrade capacity ‣ reduce spectrum needs / utilization ‣ improve “reception” in difficult locations ‣ depending on billing, avoid roaming charges (think international!) • Not to be confused with pico-/micro-/femto-cells 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 16
UMA deployment Source: http://www.umatechnology.org/ 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 17
UMA details • Encapsulation of GSM/3G inside IP ‣ complete frame, minus the on-the-air crypto ‣ can transfer voice, IM and (in the future) video • Typically, devices are WiFi-supporting cellphones ‣ not strictly necessary, e.g., T -Mobile@Home in USA • GSM frames are not natively protected ‣ A5/2 is anyway weak (i.e., broken) 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 18
UMA Security • Handset-to-provider IPsec ‣ Strong crypto and integrity protection ‣ Key management (IKE, IKEv2) is a different story altogether ‣ Authentication done via EAP-SIM (based on shared secret) • The key management protocol (IKE/IKEv2) is complex ‣ Perhaps “too big” to be trusted ‣ More importantly, easy to misconfigure • not as big a problem in a tightly managed environments (cellphones) • but, UMA+smartphones spells trouble • Provider must interface internal network with Internet ‣ higher risk of compromise by external attackers ‣ large numbers of potentially malicious insiders Systems and Internet Infrastructure Security Laboratory (SIIS) Page 19
Threat in VoIP systems • Everyone thinks of the traditional C/I/A threats • Loss of communication confidentiality and privacy (C) ‣ traffic analysis, content privacy • Loss of communication integrity (I) ‣ impersonation (inbound, outgoing calls), modification of content, falsification of call records • Loss of communication availability (A) ‣ accidental or intentional denial of service (DoS) Systems and Internet Infrastructure Security Laboratory (SIIS) Page 20
Unique VoIP characteristics • Elaborate billing infrastructure in place • Users are used to paying for telephony services • Most charges are for relatively small amounts • Large number of charges per billing cycle ‣ unlikely that small unauthorized charge will be noticed or challenged • Phone infrastructure is “trusted” by average user ‣ perception carried over from PSTN ‣ not grounded on facts or experience Systems and Internet Infrastructure Security Laboratory (SIIS) Page 21
VoIP-Specific Threats and Risks • Theft of service , e.g., toll fraud, billing fraud • Social engineering , e.g., phishing/spear-phishing • Direct charge-back , e.g., immediate monetization • Risks ‣ Some in common with other types of systems (software vulnerabilities) ‣ Some are very specific to IMS (protocol vulnerabilities) ‣ Some are common, but are amplified by some IMS feature, e.g., large-scale phishing through impersonation or call hijacking • Q: are these substantially different than in cell networks? Systems and Internet Infrastructure Security Laboratory (SIIS) Page 22
VoIP/IMS risk vectors • Variety of risk vectors ‣ some in common with other types of systems • software vulnerabilities ‣ some are very specific to IMS • protocol vulnerabilities ‣ some are common, but are amplified by some IMS feature • large-scale phishing through impersonation or call hijacking 2 Systems and Internet Infrastructure Security Laboratory (SIIS) Page 23
Recommend
More recommend
