If someone ask you a question. What is the enemy of cloud computing architecture? Yes, we believed that more details can be provided. For instance Distributed Denial Of Services, malware, virus, misconfiguration,…etc. But what do you think the influence of rootkit? Since Micro-segmentation architecture assists cloud computing services provider build their campus. From general point of view, system OS platform and application run on top of virtual environment are easy to manage. All system and users activities will be managed and monitored by hypervisor. What if unknown signature shell code attack to virtual machine? Is there any possibilities influence the neighbor system on same premises? Let’s do a quick review and then jump to discussion.
The fundamental of hypervisor
Bare-metal hypervisor
Provides partition isolation, reliability and higher security.It has no host OS layer to attack theoretically.The bare metal hypervisor base design products includes Oracle VM Server for SPARC, Oracle VM Server for x86, the Citrix XenServer, Microsoft Hyper-V and VMware ESX/ESXi.
Hosted hypervisor
Low cost, no additional drivers and ease of use and installation.The hosted hypervisor base design products includes VMware Workstation, VMware Player, VirtualBox, Parallels Desktop for Mac and QEMU.
Arm-based hypervisor
System virtualization for ARM is useful for mobile device and future ARM based server.Cell phones and Internet of Things are the arm-based hypervisor setup.
Types of Hypervisor – Informatic diagram:
This section we focus on bare metal hypervisor security outline. In the virtual machine world, linux system are everywhere. Even though the hypervisor is the linux based system or modified linux system built. The critical OS systems being relocated to Linux system platform last 5 years. Besides, the cell phones based on Linux OS become the main trend today. No matter it is Apple or Android, their core is the linux system. We relies on SSH connectivity today, it adopted by IT industry. A question might get in your mind, is it possible to re-engineer the SSH become a cyber weapon?Regarding to the cyber incident historical records, hacker start this idea earlier in 2015. We remember the XOR-DDOS attacks criteria , hackers cocktail the attack mechanism run in hybrid mode. Both SYN and DNS flood generated by the Xor.DDoS Malware. The attacker will send many SYN packs to victim host with multiple sources and launched on port 22 (ssh). Yes, the hacker take the popularity of SSH because it is a harmonized standards across the IT world.
Famous rootkit against linux environment
Phalanx: This rootkit uses /dev/mem/ interface to inject hostile code into kernel memory and hijack system calls. It has been designed for compromising the Linux 2.6 branch. Phanlanx design for harvest SSH keys and other credentials. Since Phalanx attack found on 2008 and file record by CERT. But this attack technology still valid today.
Phalanx characteristic:
Hooking lookup Tables, Code patching & Hooking CPU registers
Ebury SSH Rootkit: In February 2013, CERT-Bund started analyzing Ebury in depth and was able to identify thousands of systems around the world infected with the malware. Ebury is a SSH rootkit/backdoor trojan for Linux and Unix operating systems. The 1st attack phase is going to replacing SSH related binaries on a compromised hosts. The non genuine SSH program so called Ebury, the goal is going to steal SSH login credentials (username/password) from incoming and outgoing SSH connections. But taking about the privileges escalation feature, it was not included in Ebury feature. When it compared with Phalanx , Ebury is easy to detect.
What if hacker sojourn rootkit in kernel. Is there any possibilities influence the neighbor system on same premises?
The guest machine compromised, however hacker might have difficulties drill down to low level system area. For instance, bare-metal hypervisor contain good isolation level. Is there any possibility engage a ring-0-attack, that is running malicious call in memory level.
Is that no way? But hacker will spend time on harvesting in memory side
When running a virtual system, it has allocated virtual memory of the host system that serves as a physical memory for the guest system, and the same process of address translation goes on also within the guest system. This increases the cost of memory access since the address translation needs to be performed twice – once inside the guest system (using software-emulated shadow page table), and once inside the host system (using hardware page table). Whereby a memory management technology (Second Level Address Translation (SLAT)) was born, his duty is going to enhance the usage of memory resources in the virtual world.
About (Second Level Address Translation (SLAT)) inherent risk
SLAT schemes such as Intel’s Extended Page Tables (EPT) and AMD’s Nested Page Tables (NPT) as shown below diagram are used to manage the virtualized memory directly from the processor. Using a larger Translation Lookaside Buffer (TLB) with additional logic circuitry inside the processor, these schemes provide faster virtual machine memory management by eliminating the intermediary step between the virtual memory address (VA) and the physical memory address (PA).
Refer to above diagram, the TLB table has the option that indicates if the received data is from a virtual machine or the native machine. Also, if the data is generated by a virtual machine, then it is tagged with that specific VM’s Address Space Identifier (ASID). Using this tag, the TLB can keep track of entries from different virtual machines in the physical machine. This method provides a significant performance improvement in VM memory management but also introduces a security risk by giving direct memory access to the guest VMs.
Remark: Above inherent risk information details (security risk of SLAT) copy from technical article Fine grain Cross-VM Attacks on Xen and VMware are possible!
Gorka Irazoqui Apecechea, Mehmet Sinan Inci, Thomas Eisenbarth, Berk Sunar Worcester Polytechnic Institute {girazoki,msinci,teisenbarth,sunar}@wpi.edu
We stop here! It was too long and boring. I am afriad that reader might lose the interest, right? Will provide update soon!