Cloud Computing Security Quiz

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Questions and Answers

What is the primary goal of maintaining confidentiality in cloud computing?

Encryption of data to prevent access by unauthorized parties (correct)

Monitoring data usage across the cloud environment

Ensuring data is available to all network users

Regularly backing up data to prevent loss

Which method is commonly used to ensure data integrity in cloud computing?

Implementing a digital signature or MAC (correct)

Data replication across multiple servers

Regularly deleting old data

Using encryption to protect data

What does the command 'clflush' do in the context of memory operations?

It modifies the contents of a memory location

It reads data from a specified memory address

It encrypts the data at the specified address

It clears the cache for a specified address (correct)

What effect does the instruction 'mfence' have in a code execution context?

It ensures memory writes are completed before continuing Signup and view all the answers

What does the instruction 'jmp code1a' signify in the provided code snippet?

It jumps to another location in the code for repeated execution Signup and view all the answers

What is considered a major concern regarding data in cloud computing?

Centralization of sensitive data Signup and view all the answers

Which aspect does NOT significantly contribute to vulnerabilities in cloud computing?

High trust in cloud providers Signup and view all the answers

What security measure is considered important at the application level in cloud security?

Authentication Signup and view all the answers

Which of the following poses a privacy threat for cloud providers?

Local laws such as the PATRIOT Act Signup and view all the answers

What is a significant risk associated with the horizontal co-location of resources in cloud computing?

Wider attack surface Signup and view all the answers

Why is it essential for cloud providers to be trustworthy?

They safeguard large amounts of sensitive data. Signup and view all the answers

What specific aspect should cloud computing security focus on?

Security implications unique to cloud systems Signup and view all the answers

Which type of security is critical for ensuring system integrity in cloud services?

Application-level security Signup and view all the answers

What is the purpose of the function process_request in the enclave construction?

To process an incoming message and return a response. Signup and view all the answers

Which statement about the enclave's contents is true?

The contents can be inspected while in untrusted memory. Signup and view all the answers

What is a critical issue that arises from using untrusted memory for enclave content?

There is a risk of tampering with the enclave's integrity. Signup and view all the answers

What happens if the verify_MAC function returns false in process_request?

Execution will terminate and return an error code. Signup and view all the answers

Which instruction is used to add contents to the enclave?

EADD Signup and view all the answers

What is the primary responsibility of dedicated security experts in cloud platforms?

To follow security updates and best practices Signup and view all the answers

What type of attacks can be conducted on cloud systems?

Remote attacks that exploit software vulnerabilities Signup and view all the answers

What is NOT a type of vulnerability commonly exploited in cloud computing?

Unintentional memory leaks in HTML Signup and view all the answers

What distinguishes the attack surface in cloud computing?

It includes the entire software stack, including BIOS and drivers Signup and view all the answers

What is the function of isolation provided by protected mode in modern operating systems?

To protect applications from OS tampering Signup and view all the answers

Which of the following represents a component of the trusted computing base (TCB) in cloud platforms?

All software and hardware components of the system Signup and view all the answers

Which example is classified as a direct hardware attack on cloud systems?

Spectre and Meltdown on Intel CPUs Signup and view all the answers

What is a significant limitation of protected mode regarding application security?

It allows malicious applications to exploit flaws to gain full privileges Signup and view all the answers

What is the primary encryption method used by CryptDB for efficient query processing?

Symmetric-key encryption Signup and view all the answers

What is a disadvantage of standard encryption methods like AES in database queries?

They prevent any type of query. Signup and view all the answers

In the context of CryptDB, what does the term 'indistinguishability' refer to?

It prevents known-plaintext attacks. Signup and view all the answers

What is the outcome of the randomization used in CryptDB's encryption approach?

The same plaintext values yield different ciphertexts. Signup and view all the answers

Which type of attack does the randomization in CryptDB aim to prevent?

Known-plaintext attack Signup and view all the answers

What query capability does deterministic encryption in CryptDB allow?

Equality search functionality Signup and view all the answers

Which of the following is NOT an encryption characteristic of CryptDB?

Uses solely fully homomorphic encryption Signup and view all the answers

What kind of trade-offs does CryptDB present when it comes to encryption methods?

Privacy versus expressiveness of queries Signup and view all the answers

What is the purpose of the function `verify_MAC` in the trusted code?

To ensure the integrity of the input message Signup and view all the answers

What will happen if the return value of `EENTER` is less than zero?

The system will log a corrupted message error Signup and view all the answers

Which function is responsible for decrypting the message before processing?

decrypt_msg Signup and view all the answers

In the main loop, what type of operation does `receive` perform on `request_buf`?

It populates the buffer with incoming requests Signup and view all the answers

What is the role of `send` in the enclave code?

To relay the response back to the requester Signup and view all the answers

Which part of the provided application is untrusted code?

The main function Signup and view all the answers

What does the `process_msg` function do?

Encrypts the output after processing Signup and view all the answers

What does the `EEXIT` function signify in the code?

It ends the enclave session successfully Signup and view all the answers

Study Notes

Course Information

Course Title: Cloud Computing
Course Code: LINFO2145
Lesson: 9 - Cloud Security
Instructor: Pr. Etienne Rivière
Contact: [email protected]

Announcements

Quiz 3: Lectures 5 and 6, results available after this lecture
Quiz 4: Lectures 7 and 8, available after this lecture, Due: Nov 27, 10:45
Reviews: Dec 4, 10:45

Lecture Objectives

Introduce security concerns from cloud computing
Overview of data and computation integrity protection in cloud
Describe new approaches for confidential data processing in the cloud

Introduction (1)

Cloud computing platforms and applications are tempting attack targets
Large amounts of data are stored centrally
Sensitive data is often publicly available, making it an attractive target for malicious activity
Limited control of software stacks, particularly in PaaS.
Multi-tenancy creates larger attack surfaces
Co-location of resources creates new attack opportunities.
Single point of failure within one service can affect other services

Introduction (2)

High trust required of cloud providers
Cloud providers need to comply with local privacy regulations (e.g. PATRIOT Act)
Security concerns are specific to cloud systems
Application-level and OS-level security practices remain important

Why is Cloud Security Important?

Major breaches like the Yahoo (1 billion accounts) and Dropbox (68 million) hacks, and the 2012 LinkedIn breach highlight the need for robust cloud security

The Provider Perspective

Cloud providers must protect their customers from malicious actors
Hypervisor-based isolation provides a limited security guarantee
One-way protection: the provider does not protect the customer from the provider

The Client Perspective

Cloud tenants must trust their providers, including personnel and software components
Ideally, clients would only trust their portion of the service

Multi-tenancy and Security

Resource sharing in virtualization creates new security threats
Hypervisors and VMs are vulnerable to attacks impacting all tenants
Access to the hypervisor gives access to all VM memory, including the kernel and page tables.
Dedicated security experts and best practices are important.

Protected Mode Not Sufficient

Protected mode (rings) is insufficient to prevent exploits
Malicious applications can exploit flaws, gaining full privileges and potentially compromising the operating system or other applications
Attack surface includes the entire software stack, comprising applications, OS, VMM, drivers, and BIOS

Example of Protection Rings in Microsoft Hypervisor

Depicts layers of isolation for different components within a hypervisor
Emphasizes the separation of different parts of the hypervisor

Attacking the Cloud

Attacks are performed by executing software on the victim's computer, including remote execution
Most attacks exploit vulnerabilities in software components, including exploitable memory safety vulnerabilities in C/C++
Malicious APIs target services and infrastructure management interfaces
Hardware vulnerabilities like Spectre and Meltdown, and RowHammer attacks are also possible

The Software Stack

Cloud platforms utilize enormous amounts of code that must be trusted
Examples of codebases include Linux, KVM, and OpenStack

Bugs are a Reality

More code generally means more bugs
Exploited vulnerabilities can lead to complete disclosure of sensitive data
Xen hypervisor and Linux kernel have a significant number of reported vulnerabilities (e.g., 184 for Xen, 721 for Linux kernel in a given time period)

Examples of Software Attacks

Control-flow hijacking: Goal is to execute arbitary code.
Code injection attacks: Overwriting addresses to inject code
Return-oriented programming: Stack corruption to execute existing instructions

Example: Heartbleed Bug

Serious vulnerability in OpenSSL
Widely used; targets web servers, email, chat, and VPNs
Buffer overrun in heartbeat message handling resulting in exposure of memory
Exploited to read server memory, including sensitive data like passwords, private keys, etc.

Other Examples

"All your clouds are belong to us" (2011): attacks targeting EC2 management APIs
Colocation attacks: targeting VMs on public clouds
Attacks at hypervisor, OS and CPU level
Exploit bugs to gain access to cached content from VMs, perform bus sniffing, obtain memory communication or perform cold boot attacks.

Hardware Attacks in the Cloud

Hardware based attacks may or may not require direct physical access to the host
With physical access, attacks include bus sniffing, and obtaining memory communication in DRAM
Cold boot attacks obtain memory values during power cycles using short-lived memory state

Remote Hardware Attacks: "Row Hammer"

Attacking physical memory to flip bits in neighboring memory
Can cause sandbox escapes and corrupted page tables

Goals: Security in the Cloud

Confidentiality: Protecting data from unauthorized access.
Integrity: Protecting data from unauthorized modification

Tools: Cryptographic Hash Function

Algorithm mapping arbitrary inputs into fixed-size outputs
Infeasible inversion. Collision resistant
More computationally intensive compared to generic hashes

Tools: Symmetric Cryptography

Shared secret key for encryption and decryption
Example: Advanced Encryption Standard (AES)

Tools: Symmetric Cryptography - MAC

Message authentication code (MAC)
Integrity and authenticity checking of messages
Key required to produce a MAC
Does not offer confidentiality

Tools: Asymmetric Cryptography

Each party has a public and private key pair
Public key used for encryption; private key for decryption
Example: Rivest-Shamir-Adleman (RSA)

Tools: Asymmetric Cryptography - MAC (Digital Signature)

Digital signature in asymmetric cryptography
Signed using the sender's private key, verified with public key
Ensures message integrity and authenticity

Ensuring Data Confidentiality

Data-at-rest protection: Encrypting data directly on disk (e.g., full-disk encryption and encrypted file systems)
Data-in-flight protection: Using end-to-end encryption mechanisms like TLS

Ensuring Data Confidentiality - TPM (Trusted Platform Module)

Hardware security chip
Generates and stores cryptographic keys
Provides remote attestation

Ensuring Data Confidentiality – In-use Data

Decrypting data before processing to maintain confidentiality in-use
Confidentiality required during computations in the cloud

Securing Data During Computation

Searchable data while protecting against security attacks on data distribution
Privacy-utility-performance tradeoff consideration when applying security measures

Tools

Software-Level Encryption
Specific and generic encryption mechanisms
Hardware support for trusted computing
Homomorphic encryption

Encrypted Data Processing - Homomorphic Encryption

Allows computation on encrypted data without decryption
Enables operations like addition and multiplication on encrypted data; maintains confidentiality throughout computation.
Example: Fully homomorphic encryption

Homomorphic Encryption - HELib

Open-source homomorphic encryption library developed by IBM
Designed to make homomorphic encryption more practical
Low-level routines (addition, multiplication, etc.)
Performance improvements but still requires significant resources, far from being practical in terms of computation time

Specific Encryption Schemes

Homomorphic encryption (generic but costly)
Specific schemes for targeted operations (e.g., exact match, nearest match, range, equality)
Example: CryptDB (encrypted SQL database)

CryptDB: Encrypted SQL Database

Proxy between the client and the database to handle query rewrites and data encryption/decryption.
Prevents exposure of sensitive data to the untrusted zone of the cloud environment (especially in servers or proxy)
Provides standard encryption (AES) but prevents from arbitrary query execution in non-trusted environment

CryptDB: Encryption Levels (1)

Random encryption (e.g., AES): No data query possible
Deterministic encryption (e.g., Pseudorandom permutation): Equality searches possible but maintains ciphertext integrity
Order-preserving encryption: Enables range queries

CryptDB Encryption Levels (2)

Summation homomorphic: Enables summation operations on encrypted data
Joins: Enables joins across encrypted data; encryption key may be different
Word Search: Limited full-word functionality but vulnerable with known frequency attacks

Onion Layers Encryption

Multi-level encryption layer structure
Security and privacy depend on how a specific level of encryption can be handled and how many levels of encryption an application requires

CryptDB Performance

Performance of CryptDB can vary depending on the workload and number of cores
Performance can be slower by an order of magnitude compared to non-encrypted databases due to the increased processing tasks from encryption/decryption
Additional proxy server cost

Towards Hardware Support

Software-based confidentiality or data protections have limited applicability and performance limitations
The trusted computing base traditionally encompasses hardware and software stack, but there is a need to reduce this trusted code base to allow application enclaves

Intel SGX

"Software Guard Extensions" in Intel CPUs (e.g. Skylake, Kaby Lake)
Provides hardware-level protection for code and data in untrusted environments
Platform owner considered malicious
Only the CPU chip and isolated enclave are considered trusted

Enclaves

Isolated memory regions (enclaves) for code and data
Enclave content is protected by the hardware (Memory Encryption Engine [MEE])
Plaintext secrets are prevented from being directly stored in main memory
Enclave memory accessible only by enclave code, protecting against privilege escalation attacks

Enclave Memory

Enclave memory is not accessible to other software
Enclaves can access memory within the process
Application can protect its secrets, reducing attack surface

Enclave Memory APIs

ECALLs are enclave interface functions, providing input to the enclave
OCALLs are enclave calls for returning results outside of the enclave

SGX Execution Model

Trusted execution environment within a process, with dedicated code and data
Controlled entry points
Confidentiality and integrity provisioned
Multiple threads support
Full access to application memory

Enclave Page Cache (EPC)

Physical memory region protected by the MEE
EPC holds enclave contents
Shared resource for all enclaves on the platform
Content encryption in DRAM; decryption when brought to CPU
Larger EPC sizes available in newer versions

SGX Limitations

Memory limit for enclaves
Security not absolute (vulnerabilities may exist)
Performance is generally impacted compared to other approaches (enclave entry/exit, paging are costly)
Legacy code, and application partitioning considerations

Conclusion

Cloud security requires both general security practices and new techniques specific to cloud architectures (e.g., attacks on colocated and trusted code)
Encryption of data in the cloud is beneficial
Trusted Execution Environments (HW support) offer a way to reduce the trusted code base and trust only the required application enclaves

References (1/2) and (2/2)

Includes a large list of academic papers which are relevant to cloud security practices

SGX Primer

Introduction to writing SGX applications

1. Define Interface

Enclave definition language (myenclave.edl) for function declarations
untrusted and trusted sections for separating function declarations

2. Write Code

Application (application.c) code and enclave (myenclave.c) code example (including main() and compute()) functions
Demonstrate the sgx_initialize_enclave and ecall_compute calls

3. Compile Code

Compilation of application.c, myenclave.c to generate myenclave.so and a.out
gcc, different compiler flags

4. Sign Code and Run

Signing myenclave.so using SGX specific tool (sgx_sign, private_key.pem)
Execution and results from the application

Studying That Suits You

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Description

Test your knowledge on key concepts of cloud computing security, including confidentiality, data integrity, and important memory operations. This quiz will challenge your understanding of essential commands and instructions in a cloud environment.