VM Attacks: Security Analysis PDF

Let’s break down and address the questions systematically, providing clear and detailed explanations for each. a) With a buffer over ow in the webserver process, the attacker is able to get a shell on the target system. Under which user is the shell runn...

Let’s break down and address the questions systematically, providing clear and detailed explanations for each. a) With a buffer over ow in the webserver process, the attacker is able to get a shell on the target system. Under which user is the shell running? If this is not the root user, which additional steps are needed to become root? List both a speci c attack and the general class the attack represents. Answer: User Context of the Shell: ◦ The shell obtained through the buffer over ow will run under the same user as the webserver process. ◦ Most webservers run under a non-privileged user for security reasons (e.g., www- data, nobody, or a dedicated user). If Not Root: Steps to Elevate Privileges: ◦ Privilege Escalation Attack: ▪ The attacker would need to escalate privileges to root. This can be done using: ▪ Exploitation of Kernel Vulnerabilities: Exploit a vulnerability in the kernel or setuid binaries (e.g., dirty pipe, dirty cow). ▪ Miscon gured Permissions: Abuse miscon gured les or services with improper permissions (e.g., writable /etc/passwd or insecure sudo con gurations). ▪ Exploitation of Setuid Programs: Find and exploit setuid binaries to execute commands as root. ◦ General Class of Attack: ▪ This falls under Privilege Escalation Attacks, where the attacker gains higher-level access than the initial compromise. Speci c Example: CVE-2016-5195 (Dirty Cow): ◦ Exploit a race condition in the Linux kernel that allows privilege escalation to root. ◦ The attacker can modify les they should not have access to (e.g., changing their user privileges to root). b) The attackers now have root access to the VM hosting the webservices. We want to enter the hypervisor. Describe two attack classes we can use to attack the hypervisor, and give an example attack for every class. Answer: 1. Exploitation of Hypervisor Vulnerabilities: fi fi fi fi fi fl fl fi fi  ◦ Description: ▪ Attackers exploit bugs in the hypervisor software itself to gain control or access to the hypervisor. ▪ Vulnerabilities may include memory corruption, improper input validation, or privilege escalation bugs in the hypervisor. ◦ Example: ▪ CVE-2017-12137: A Xen hypervisor vulnerability where a malicious PV (paravirtualized) guest could escalate privileges to access or control the hypervisor. ▪ Attackers use crafted inputs to exploit memory corruption vulnerabilities in the Xen interface. 2. VM Escape: ◦ Description: ▪ The attacker uses aws in the hypervisor or shared virtual devices to "break out" of the VM's isolation and access the host system or hypervisor. ◦ Example: ▪ Exploiting the hypercall interface in Xen to trigger bugs in the hypervisor. ▪ For example, crafting malicious hypercalls that lead to improper memory access or execution in the hypervisor's context. c) Now that the attacker has control of the hypervisor, describe in detail how the attacker can locate the exact location of the signing key they are looking for. Answer: To locate the signing key without dumping all memory (32 GiB), the attacker must conduct a targeted memory search: 1. Analyze the Signing Process: ◦ Identify the VM responsible for signing operations by monitoring inter-VM communication or hypercalls. ◦ Locate the speci c process handling cryptographic operations. 2. Memory Region Targeting: ◦ Focus on Application-Speci c Memory: ▪ Search for processes in the VM that interact with cryptographic libraries like OpenSSL or GnuTLS. ◦ Use Key Patterns: ▪ Keys are often stored in standard formats: ▪ PEM Format: Look for base64 strings or -----BEGIN PRIVATE KEY-----. ▪ ASN.1 Encoding: Search for binary structures matching RSA or EC keys. 3. Utilize Memory Forensics Tools: ◦ Use tools like Volatility or Rekall to analyze memory dumps from the signing VM. ◦ Identify key buffers or regions used during signing operations. 4. Hypervisor-Assisted Monitoring: fi fl fi  ◦ Monitor the signing VM for cryptographic API calls or hypercalls to pinpoint when and where keys are loaded into memory. d) How can the attacker transfer the signing key out? List at least three possible ways, and indicate if this list is exhaustive. Answer: 1. Covert Network Channels: ◦ The attacker sends the signing key over the network using an encrypted or disguised communication channel (e.g., HTTPS, DNS tunneling). ◦ Detection Risk: Moderate, depending on the network monitoring tools in place. 2. Embed in Legitimate Traf c: ◦ Insert the signing key into seemingly legitimate traf c, such as log les or harmless- looking HTTP requests. ◦ Detection Risk: Low if disguised effectively. 3. Hypervisor Log Manipulation: ◦ Hide the signing key in the hypervisor logs or les shared between the VM and the hypervisor. ◦ Detection Risk: Low if logs are not closely monitored. 4. Local Ex ltration via USB: ◦ If physical access is possible, store the signing key on a USB drive or removable media. ◦ Detection Risk: High, as physical access may be noticed. Exhaustive? Not exhaustive. Other methods, such as steganography or using side channels (e.g., covert CPU cache timing), could also be employed. e) For each step above, think of protections that will counter this attack class. Answer: 1. Buffer Over ow Protection: ◦ Use modern compiler techniques like ASLR (Address Space Layout Randomization) and stack canaries. ◦ Implement input validation and bounds checking in webserver code. 2. Privilege Escalation Protection: ◦ Apply kernel updates to patch vulnerabilities. ◦ Limit sudo privileges and audit setuid binaries. 3. Hypervisor Protection: ◦ Keep hypervisor software updated to patch known vulnerabilities. ◦ Use strong access controls and logging to detect suspicious hypervisor activity. 4. Key Protection: fi fl fi fi fi fi  ◦ Use hardware security modules (HSMs) to store keys securely, preventing them from being stored in VM memory. 5. Data Ex ltration Prevention: ◦ Implement strict network monitoring (e.g., IDS/IPS) to detect unusual traf c patterns. ◦ Encrypt sensitive logs and monitor le access activity. f) Are there attack scenarios possible with fewer steps? Can these attack scenarios be mounted directly from the user account running the web services? Answer: 1. Fewer Steps: ◦ If the signing key is stored directly on the webserver VM, the attacker can compromise the webserver process and access the key without breaking out of the VM or targeting the hypervisor. 2. Direct Attack from User Account: ◦ If the webserver process has access to the signing key (e.g., stored in a local con guration le), the attacker could extract it immediately after exploiting the webserver without requiring root or hypervisor access. g) Suppose you were allowed to signi cantly alter the hosting setup. Can it be made more secure? Answer: Yes, the hosting setup can be made more secure by adopting the following: 1. Use Hardware Security Modules (HSMs): ◦ Store signing keys in dedicated HSMs, ensuring keys are never exposed in VM memory. 2. Isolate Critical Operations: ◦ Move signing operations to a dedicated, secure physical machine or a highly isolated VM that is not accessible from other VMs. 3. Zero Trust Network Architecture: ◦ Implement strict access controls and ensure all inter-VM communication is authenticated and encrypted. 4. Advanced Monitoring and Logging: ◦ Deploy advanced monitoring tools to detect anomalies in memory access or network traf c. Problems Solved: Key compromise becomes extremely dif cult. Even if a VM is compromised, the key is not accessible. fi fi fi fi fi fi fi fi Problems Not Solved: If the attacker gains direct physical access to the host system, they could still compromise the HSM or hypervisor. This detailed response addresses each question thoroughly while considering technical and practical aspects of attack scenarios and mitigations.