Security and Privacy in Cloud Computing

1. Security and Privacy in Cloud Computing Ragib HasanUniversity of Alabama at BirminghamCS 491/691/791 Fall 2011 Lecture 4 08/25/2011

2. Mapping/topology Attacks • Lecture Goal • Learn about mapping attacks • Discuss different techniques and mitigation strategies • Analyze the practicality and impact • Reading: • Hey, You, Get Off of My Cloud: Exploring Information Leakage in Third-Party Compute Clouds, Ristenpart et al., CCS 2009 Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

3. Why Cloud Computing brings new threats? Traditional system security mostly means keeping bad guys out The attacker needs to either compromise the auth/access control system, or impersonate existing users Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

4. Why Cloud Computing brings new threats? But clouds allow co-tenancy : Multiple independent users share the same physical infrastructure So, an attacker can legitimately be in the same physical machine as the target Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

5. Challenges for the attacker How to find out where the target is located How to be co-located with the target in the same (physical) machine How to gather information about the target Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

6. Hey, You, Get Off of My Cloud: Exploring Information Leakage in Third-Party Compute Clouds, Ristenpart et al., CCS 2009 First work on cloud cartography Attack launched against commercially available “real” cloud (Amazon EC2) Claims up to 40% success in co-residence with target VM Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

7. Strategy Map the cloud infrastructure to find where the target is located Use various heuristics to determine co-residency of two VMs Launch probe VMs trying to be co-resident with target VMs Exploit cross-VM leakage to gather info about target Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

8. Threat model Attacker model • Cloud infrastructure provider is trustworthy • Cloud insiders are trustworthy • Attacker is a malicious third party who can legitimately use the cloud as a client Assets • Confidentiality aware services run on cloud • Availability of services run on cloud Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

9. Tools of the trade Nmap, hping, wget for network probing Amazon EC2’s own DNS to map dns names to IPs Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

10. Sidenote: EC2 configuration Dom0 is the first instance on the machine, connected to physical adapter All other instances route to external world via dom0 [Figures from Xen Wiki] EC2 uses Xen, with up to 8 instances per physical machine Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

11. EC2 allocation scheme • Users can choose • Region (US or Europe?) • Availability zone (i.e., data center) • Instance type (m1.small, c1.medium, m1.large, m1.xlarge, c1.xlarge) • VMs share physical hardware; each VM gets 2 IP addresses : an external, and an internal IP Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

12. Task 1: Mapping the cloud Different availability zones use different IP regions. Each instance has one internal IP and one external IP. Both are static. For example: External IP: 75.101.210.100 External Name: ec2-75-101-210-100.computer-1.amazonaws.com Internal IP: 10.252.146.52 Internal Name: domU-12-31-38-00-8D-C6.computer-1.internal Reverse engineering the VM placement schemes provides useful heuristics about EC2’s strategy Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

13. Task 1: Mapping the cloud • Clouds can be mapped via probing • External probing: The probe is outside the cloud • Internal probling: The probe is inside the cloud • Internal probing has to satisfy Amazon’s policies, external probing doesn’t Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

14. Task 1: Mapping the Cloud Finding: same instance type within the same zone= similar IP regions Reverse engineered mapping decision heuristic: All IPs from /16 are from same availability zone A /24 inherits any included sampled instance type. A /24 containing a Dom0 IP address only contains Dom0 IP address. All /24’s between two consecutive Dom0 /24’s inherit the former’s associated type. Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

15. Task #2: Determining co-residence • Co-residence: Check to determine if a given VM is placed in the same physical machine as another VM • Network based check: • Match Dom0 IP addresses, check packet RTT, close IP addresses (within 7, since each machine has 8 VMs at most) • Traceroute provides Dom0 of target • No false positives found during experiments Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

16. Task #2: Determining co-residence • How do we know the heuristics work? • Technique: Launch a disk based covert channel, such that only co-resident instances cane exchange data using it • E.g., one instance starts reading from random locations, causing longer disk read times for other co-located instances Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

17. Task #3: Making a probe VM co-resident with target VM Brute force scheme • Idea: figure out target’s availability zone and type • Launch many probe instances in the same area • Success rate: 8.4% Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

18. Task #3: Making a probe VM co-resident with target VM Smarter strategy: utilize locality • Idea: VM instances launched right after target are likely to be co-resident with the target • Paper claims 40% success rate Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

19. Task #3: Making a probe VM co-resident with target VM Window of opportunity is quite large, measured in days Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

20. Task #4: Gather leaked information Now that the VM is co-resident with target, what can it do? • Gather information via side channels • Perform DoS Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

21. Task 4.1: Gathering information If VM’s are separated and secure, the best the attacker can do is to gather information • Measure latency of cache loads • Use that to determine • Co-residence • Traffic rates • Keystroke timing Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

22. Mitigation strategies #1: Mapping Use a randomized scheme to allocate IP addresses Block some tools (nmap, traceroute) Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

23. Mitigation strategies #2: Co-residence checks Prevent traceroute (i.e., prevent identification of dom0) Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

24. Mitigation strategies #3: Co-location • Not allow co-residence at all • Beneficial for cloud user • Not efficient for cloud provider Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

25. Mitigation strategies #4: Information leakage Prevent cache load attacks? Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

26. Discussion How is the problem different from other attacks? What’s so special about clouds? Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

27. Discussion Cons • Are the side channels *really* effective? Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011

28. Further Reading Amazon downplays report highlighting vulnerabilities in its cloud service Hypothetical example described in report much harder to pull off in reality, company saysTechWorld, Oct 29, 2009. http://bit.ly/dvxEZp Ragib Hasan | UAB CIS | CS491/691/791 Fall 2011