A Formal Approach for the Verification of AWS IAM Access Control Policies

Part 3: SecurityInternational audienceCloud computing offers elastic, scalable and on-demand network access to a shared pool of computing resources, such as storage, computation and others. Resources can be rapidly and elastically provisioned and the users pay for what they use. One of the major challenges in Cloud computing adoption is security and in this paper we address one important security aspect, the Cloud authorization. We have provided a formal Attribute Based Access Control (ABAC) model, that is based on Event-Calculus and is able to model and verify Amazon Web Services (AWS) Identity and Access Management (IAM) policies. The proposed approach is expressive and extensible. We have provided generic Event-Calculus modes and provided tool support to automatically convert JSON based IAM policies in Event-Calculus. We have also presented performance evaluation results on actual IAM policies to justify the scalability and practicality of the approach

Block public access: Trust safety verification of access control policies

© 2020 Owner/Author. Data stored in cloud services is highly sensitive and so access to it is controlled via policies written in domain-specific languages (DSLs). The expressiveness of these DSLs provides users flexibility to cover a wide variety of uses cases, however, unintended misconfigurations can lead to potential security issues. We introduce Block Public Access, a tool that formally verifies policies to ensure that they only allow access to trusted principals, i.e. that they prohibit access to the general public. To this end, we formalize the notion of Trust Safety that formally characterizes whether or not a policy allows unconstrained (public) access. Next, we present a method to compile the policy down to a logical formula whose unsatisfiability can be (1) checked by SMT and (2) ensures Trust Safety. The constructs of the policy DSLs render unsatisfiability checking PSPACE-complete, which precludes verifying the millions of requests per second seen at cloud scale. Hence, we present an approach that leverages the structure of the policy DSL to compute a much smaller residual policy that corresponds only to untrusted accesses. Our approach allows Block Public Access to, in the common case, syntactically verify Trust Safety without having to query the SMT solver. We have implemented Block Public Access and present an evaluation showing how the above optimization yields a low-latency policy verifier that the S3 team at AWS has integrated into their authorization system, where it is currently in production, analyzing millions of policies everyday to ensure that client buckets do not grant unintended public access

Stratified Abstraction of Access Control Policies

The shift to cloud-based APIs has made application security critically depend on understanding and reasoning about policies that regulate access to cloud resources. We present stratified predicate abstraction, a new approach that summarizes complex security policies into a compact set of positive and declarative statements that precisely state who has access to a resource. We have implemented stratified abstraction and deployed it as the engine powering AWS’s IAM Access Analyzer service, and hence, demonstrate how formal methods and SMT can be used for security policy explanation

Model Checking Access Control Policies: A Case Study using Google Cloud IAM

Authoring access control policies is challenging and prone to misconfigurations. Access control policies must be conflict-free. Hence, administrators should identify discrepancies between policy specifications and their intended function to avoid violating security principles. This paper aims to demonstrate how to formally verify access control policies. Model checking is used to verify access control properties against policies supported by an access control model. The authors consider Google's Cloud Identity and Access Management (IAM) as a case study and follow NIST's guidelines to verify access control policies automatically. Automated verification using model checking can serve as a valuable tool and assist administrators in assessing the correctness of access control policies. This enables checking violations against security principles and performing security assessments of policies for compliance purposes. The authors demonstrate how to define Google's IAM underlying role-based access control (RBAC) model, specify its supported policies, and formally verify a set of properties through three examples

Best practices in cloud-based Penetration Testing

This thesis addresses and defines best practices in cloud-based penetration testing. The aim of this thesis is to give guidance for penetration testers how cloud-based penetration testing differs from traditional penetration testing and how certain aspects are limited compared to traditional penetration testing. In addition, this thesis gives adequate level of knowledge to reader what are the most important topics to consider when organisation is ordering a penetration test of their cloud-based systems or applications. The focus on this thesis is the three major cloud service providers (Microsoft Azure, Amazon AWS, and Google Cloud Platform). The purpose of this research is to fill the gap in scientific literature about guidance for cloud-based penetration testing for testers and organisations ordering penetration testing. This thesis contains both theoretical and empirical methods. The result of this thesis is focused collection of best practices for penetration tester, who is conducting penetration testing for cloud-based systems. The lists consist of topics focused on planning and execution of penetration testing activities

Improving Cloud Governance by Increasing Observability

Rise in popularity of Cloud computing has introduced new challenges for IT-governance. The multitude of different services and possible configurations Cloud providers offer can make it hard to get a comprehensive overview of the environment. To successfully govern an organisations Cloud environment it is important to be able to easily make accurate and reliable observations of the environments state, security, and changes to the configurations. This thesis takes a look into the research literature to find out what kinds of risks have been identified in governing the Cloud environment and ways to mitigate them. One of the latest advancements in improving the Cloud governance is the introduction of automated formal reasoning tools for configuration analysis. One customer case where multiple vendors are building services on multiple cloud accounts is used as an example. Architecture for application, security, and audit log collection, indexing, and monitoring is described. Special attention is given to the identity and access management requirements. The thesis concludes with the assessment of the selected approach and tools and services used to implement it. Some alternative solutions, possible improvements, and further development to the implementation are considered

A comprehensive meta-analysis of cryptographic security mechanisms for cloud computing

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The concept of cloud computing offers measurable computational or information resources as a service over the Internet. The major motivation behind the cloud setup is economic benefits, because it assures the reduction in expenditure for operational and infrastructural purposes. To transform it into a reality there are some impediments and hurdles which are required to be tackled, most profound of which are security, privacy and reliability issues. As the user data is revealed to the cloud, it departs the protection-sphere of the data owner. However, this brings partly new security and privacy concerns. This work focuses on these issues related to various cloud services and deployment models by spotlighting their major challenges. While the classical cryptography is an ancient discipline, modern cryptography, which has been mostly developed in the last few decades, is the subject of study which needs to be implemented so as to ensure strong security and privacy mechanisms in today’s real-world scenarios. The technological solutions, short and long term research goals of the cloud security will be described and addressed using various classical cryptographic mechanisms as well as modern ones. This work explores the new directions in cloud computing security, while highlighting the correct selection of these fundamental technologies from cryptographic point of view

Proactive Security Auditing for Clouds

Cloud computing is emerging as a promising IT solution for enabling ubiquitous, convenient, and on-demand accesses to a shared pool of configurable computing resources. However, the widespread adoption of cloud is still being hindered by the lack of transparency and accountability, which has traditionally been ensured through security auditing techniques. Security auditing in the cloud poses many unique challenges in data collection and processing (e.g., data format inconsistency and lack of correlation due to the heterogeneity of cloud infrastructures), and in verification (e.g., prohibitive performance overhead due to the sheer scale of cloud infrastructures and need of runtime verification for the dynamic nature of cloud). To this extent, existing security auditing solutions can mainly be categorized into three types: retroactive, intercept-and-check and proactive. The retroactive auditing approach is the traditional auditing technique, which audits after the fact and cannot prevent irreversible damages (e.g., leakage of sensitive information and denial of service attacks). The intercept-and-check approach offers runtime auditing and performs all the auditing steps after the occurrence of a critical event (i.e., which may potentially violate a security property). However, this approach results significant delay in responding each critical event. On the other hand, the existing proactive approach requires the changes (in the cloud configurations) planned for the future in advance to verify its compliance; however, this approach is not practical, because the future change plan is not always available due to cloud’s dynamic and ad-hoc nature. In this thesis, we address all the above-mentioned limitations of the existing works by proposing a proactive security auditing system, which potentially can prevent irreversible damages, respond in significantly less time and offer a practical approach without requiring any future change plan. To this purpose, we conduct our work into three main phases. During the first phase, we propose a runtime security auditing system for the user-level of the cloud; where our proposed system audits wide range of security properties relevant to different authentication and authorization mechanisms, such as role-based access control (RBAC), attribute-based access control (ABAC) and single sign-on (SSO), and enhances the existing intercept-and-check solutions by adopting an incremental approach to improve the efficiency. In the second phase of our work, we propose a novel approach of proactive security auditing; which leverages the dependency relationship among cloud events and pre-computes the most expensive parts of the auditing process to keep the response time of the solution to a practical level. In our final phase, we utilize learning techniques to automatically capture these probabilistic dependency relationships, and propose an automated log processing approach to prepare the raw logs collected from cloud deployments for these learning methods to significantly enhance the practicality of our proactive security auditing system. Also, to demonstrate the applicability, scalability and efficiency of our proposed system, we integrate it to OpenStack, a major cloud platform, and evaluate it using both synthetic and real data. In summary, this thesis contributes towards enhancing security, efficiency and practicality of security auditing in the cloud environment

Least-Privilege Identity-Based Policies for Lambda Functions in Amazon Web Services (AWS)

We address least-privilege in a particular context of public cloud computing: identity-based policies for callback functions, called Lambda functions, in serverless applications of the Amazon Web Services (AWS) cloud provider. We argue that this is an important context in which to consider the fundamental security design principle of least-privilege, which states that every thread of execution should possess only those privileges it needs. We observe that poor documentation from AWS makes the task of devising least-privilege policies difficult for developers of such applications. We then describe our experimental approach to discovering least-privilege for a method call, and our observations, some of which are alarming, from running it against 171 methods across five different AWS services. We discuss also our assessment of two repositories, and two full-fledged serverless applications, all of which are publicly available, for least-privilege, and find that the vast majority of policies are over-privileged. We conclude with a few recommendations for developers of Lambda functions in AWS. Our work suggests that much work is needed, both from developers and providers, in securing cloud applications from the standpoint of least-privilege