[All Your Calls Are Still Belong to Us - How We Compromised the Cisco VoIP Crypto Ecosystem] presented at Hackito Ergo Sum 2012

by Enno Rey (ERNW GmbH), Daniel Mende (ERNW GmbH),

Tags: VOIP

Summary : Modern Enterprise VoIP solutions are complex beasts. They usually encompass application servers (e.g. for mailboxes and to provide CTI functions), infrastructure systems for authentication or crypto stuff and intelligent phones. In the end of the days the inherent complexity means that while traditional VoIP attacks (like re-directing, sniffing and reconstructing calls) might no longer work weve been able to severely compromise any enterprise VoIP environment weve pentested in the last twelve months. Based on a number of warstories, in this talk well first lay out the relevant attack vectors and the protocol or device level vulnerabilities enabling those. We will then focus on Ciscos Unified Communications solution that seemingly disposes of a mature, certificate based crypto framework protecting both the signaling and the media transport. Well, seemingly. When closely inspecting the relevant parts and messages, it turns out that at some point all the key material can be replaced by attacker chosen keys. Which effectively means that were down to cleartext-like attacks again Well publicly provide a detailed technical explanation of the underlying vulnerabilities, show a live demo sniffing calls in a presumably fully encrypted environment and of course present a tool automating a number of steps of the overall complex attack. A discussion of potential mitigating controls, both on a technical and on the provisioning process level, completes the talk.