Security Threats and Security Requirements for the Access Node Control Protocol (ANCP) IETF 67 - ANCP WG November 5-10, 2006 draft-moustafa-ancp-security-threats-00.txt

Objective Investigating security threats that all ANCP nodes could encounter and developing a threat model at the ANCP level. Accordingly, security requirements for the ANCP are defined. Out of scope: –Security policy negotiation, including authentication and authorization to define per-subscriber policy at the AAA/policy server

System Overview and Threat Model | AAA | | Server | | | CPE |---| HGW |---| | | | | | | Access | | | | Internet | | Node | | NAS |---| | | (AN) | | | | | | CPE |---| HGW |---| | | | | | On-Path Attackers (active or passive) Off-Path Attackers (active or passive) Attackers can be either on-path or off-path : active or passive Threat Model: –Off-path adversary at the CPE or HGW –Off-path adversary on the Internet or a Regional Network –On-path adversary at the network elements between the AN and the NAS –Adversary taking control over the NAS –Adversary taking control over the AN

Attackers Objectives and Potential Attacks Attackers Objectives: –Attacking an individual entity Disrupt customer's communication Gain profit for the attacker –Attacking a portion of the access network Disrupt the network services Destruct the network functioning Intercepting subscribers-related data Potential Attacks: –Message Modification –Signaling Replay –Denial of Service –Traffic Analysis –Downgrading Attack –Man-in-the-Middle Attack –Network Snooping

Attacks Against Use Case 1: Dynamic Access Loop Attributes On-path attacks between the AN and the NAS during the Access Loop attributes transfer –Passive, learning the attributes Capturing information on clients' connection state Traffic analysis –Active, acting on the transferred attributes Man-in-the-middle attack causing faked attributes Messages' modification DoS: signaling replay Off-path attacks on the Internet affecting the Access Loop attributes sharing between the NAS and the policy server –Passive, gaining information of the Access Loop attributes shared with the policy server Eavesdropping Traffic Analysis –Active DoS on the communication links to the policy server Man-in-the-middle causing Access Loop configuration data retrieval from the policy server by illegitimate NAS

Attacks Against Use Case 2: Access Loop Configuration On-path Active Attacks –Downgrading attack during Access Loop configuration updates –DoS attack through replaying of the Configure Request message –Damaging clients' profile at ANs –Replaying old packets related to privileged client's profile Off-path Attacks –Passive adversary on the Internet through eavesdropping during the Access Loop configuration retrieval by the NAS from the policy server –Active adversary on the Internet threatening subscribers-related service data in the policy server

Attacks Against Use Case 3: Remote Connectivity Test On-path Active Attacks –Man-in-the-middle attack NAS triggering to the AN to carryout the test Subscriber Response Message transfer from the AN to the NAS Off-path Active Attacks –DoS attack, in case of ATM based Access Loop, through replaying the loopback cells generated by the AN –Message truncating leading to test failure assumption

Attacks Against Use Case 4: Multicast On-path Active Attacks –Signal truncating, damaging proxy functionality in the AN, aggregation node(s) or the NAS –DoS attack during the information exchange between the NAS and the AN on the subscriber's policy and the multicast traffic configuration –Man-in-the-middle attack during the multicast replication process

Security Requirements The protocol solution MUST offer authentication of the AN to the NAS The protocol solution MUST offer authentication of the NAS to the AN The protocol solution MUST allow authorization to take place at the NAS and at the AN The protocol solution MUST offer replay protection The protocol solution MUST provide data origin authentication The protocol solution SHOULD offer confidentiality protection The protocol solution MUST be robust against DoS attacks The protocol solution SHOULD provide mutual authentication between different communicating entities The protocol solution SHOULD distinguish the control messages from the data The protocol solution SHOULD provide privacy protection

Next Step Soliciting comments Progress the draft as a separate draft complementing the framework draft