Stealing the silver Lining from your cloud

This presentation, delivered as a Black Hat WebCast in 2021, provides a comprehensive overview of cloud security from an offensive perspective. Anant Shrivastava covers the current state of cloud adoption, the shared responsibility model, security tooling options, and then maps real-world cloud attack techniques to the MITRE ATT&CK framework — focusing on storage services, Azure blob exploitation, AWS Elastic Beanstalk SSRF chains, IAM privilege escalation via shadow admin accounts, and Cognito misconfigurations.

Key Topics Covered

Cloud Adoption Landscape:

• Cloud computing has become essential, accelerated by the shift to remote work in 2020
• Traditional data centers and physical network boundaries are aging concepts
• Organizations fall into two categories: cloud-native (startups, SaaS providers, cloud aggregators) and those migrating from existing infrastructure
• Five cloud migration strategies: Rehost (lift and shift), Refactor (modernize for IaaS), Rearchitect (monolith to microservices/containers), Rebuild (rewrite as cloud-native), and Replace (adopt SaaS alternatives)

Cloud Security Concerns:

• Cloud represents a paradigm shift where conventional security controls are insufficient
• Top concerns: misconfigurations (the biggest), insecure APIs and interfaces, unauthorized access via credential leakage, unintended public data exposure, and data loss/sovereignty issues (GDPR and similar)
• Reference to NotSoSecure’s security architecture review methodology for cloud-native environments

Shared Responsibility Matrix:

• Detailed breakdown across On-prem, IaaS, CaaS, PaaS, FaaS, and SaaS models
• Tenant always responsible for: client-side security, data protection (transit and cloud), and identity & access management
• Provider responsibilities increase from IaaS (virtualization and below) through to SaaS (everything except client-side, data, and IAM)
• Understanding where responsibilities shift is critical for identifying security gaps

Security Tooling in the Cloud:

• Native vendor tools: tightly coupled with providers for greater visibility, but limited in flexibility and transparency of internals
• Third-party tools: especially valuable for multi-cloud and hybrid environments, more flexibility in output customization but limited to externally exposed data
• Both categories needed for comprehensive coverage

Attack Techniques Mapped to MITRE ATT&CK:

• MITRE ATT&CK framework used to structure cloud attack methodology
• Enumeration phase covers discovery of cloud assets and services
• Storage accounts identified as the “lynchpin” of cloud existence — enumeration, attack, exploit, and post-exploit phases

AWS S3 and Azure Blob Storage Attacks:

• Statistics showing 2% of Amazon S3 public buckets lack write protection, exposing them to ransom attacks
• Azure blob storage enumeration and exploitation techniques
• Case study: leaked Azure Storage SAS URL exploitation — loading in Azure Storage Explorer, accessing source code of Azure Functions, planting and hiding backdoors

AWS Elastic Beanstalk Attack Chain:

• Starting from SSRF vulnerability on Beanstalk-hosted application
• Metadata harvesting for account ID, region, and security credentials
• Bucket name enumeration using predictable naming patterns from account ID and region
• Source code access via AWS S3 CLI, then CI/CD pipeline abuse to deploy backdoor shells
• Additional predictable naming patterns identified by Summit Route

IAM Privilege Escalation — Shadow Admins:

• Cloud shadow admins are accounts with permissions attackers can abuse for privilege escalation
• These accounts are typically overlooked because they are not members of privileged groups like Domain Admin
• Case study: AWS managed policy AmazonElasticTranscoderFullAccess included iam:PutRolePolicy permission, allowing inline policy attachment to any role — effectively granting root admin access
• AWS fixed this by creating replacement policy AmazonElasticTranscoder_FullAccess

AWS Cognito Misconfigurations:

• Cognito supports unauthenticated and authenticated credential types
• Building on Andres Riancho’s BlackHat 2019 research on unauthenticated credentials
• Extended research around authenticated credentials revealed ways to leverage hidden signup features to gain elevated access
• Reference: NotSoSecure’s “Hacking AWS Cognito Misconfigurations” research

Actionable Takeaways

1. Map your organization’s cloud deployment model (IaaS through SaaS) against the shared responsibility matrix to identify exactly which security controls are your responsibility versus the provider’s.
2. Combine native vendor security tools with third-party solutions for comprehensive coverage, especially in multi-cloud or hybrid environments where native tools lack cross-platform visibility.
3. Target cloud storage services early in engagements — they are the foundational dependency for nearly all other cloud services and frequently contain secrets, source code, and sensitive data.
4. Hunt for shadow admin accounts in AWS by auditing managed policies for dangerous permissions like iam:PutRolePolicy that enable privilege escalation without being members of obvious admin groups.
5. Test AWS Cognito configurations for both unauthenticated and authenticated credential abuse, including hidden signup features that may grant unexpected access levels.
6. Chain SSRF vulnerabilities with cloud metadata services and predictable resource naming patterns (Elastic Beanstalk, S3) to achieve full application compromise through CI/CD pipeline abuse.
7. Audit Azure SAS URLs for overly permissive access scopes and validate that leaked storage keys are not present in public repositories.