TL;DR - Key Insights

  • AWS environments are susceptible to privilege escalation through misconfigurations in IAM policies, Lambda functions, and EC2 metadata.
  • IAM roles and policies can unintentionally grant excessive permissions, leading to exploitation paths.
  • Lambda functions with inadequate permission boundaries may act as vectors for privilege upgrades.
  • EC2 instance metadata service can be exploited if improperly secured.
  • Implement principle of least privilege, enforce stringent IAM policies, and adopt security best practices for AWS Lambda and EC2 metadata to mitigate risks.

Introduction

Privilege escalation in AWS environments is a critical security challenge that arises from improper configurations and policy mismanagement. Attackers can exploit these misconfigurations to gain unauthorized access to AWS resources, leading to data breaches, service disruptions, and further lateral movements within the cloud infrastructure. This blog post delves into privilege escalation paths associated with three key AWS services: IAM, Lambda, and EC2 metadata. We will explore real-world scenarios, demonstrate potential exploits, and provide actionable defense recommendations.

IAM Misconfigurations and Privilege Escalation

Understanding IAM Policies

AWS Identity and Access Management (IAM) is a powerful service that allows you to control access to AWS resources. However, misconfigurations in IAM policies can create privilege escalation paths. IAM policies define permissions for users, groups, and roles, and any excessive or overly permissive policies can be exploited.

Exploitation Scenario

Consider an IAM policy with the following overly permissive configuration:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "iam:*",
      "Resource": "*"
    }
  ]
}

In this scenario, a user with this policy can perform any IAM action on any resource, which can be exploited to create new users, modify roles, or attach policies that grant higher privileges.

Real-World Example

A security researcher discovered that a developer had attached an AdministratorAccess policy to their personal user account during testing but forgot to remove it afterward. This misstep allowed the researcher, who had access to the developer's credentials, to escalate privileges and access sensitive resources.

Mitigation Strategies

  • Implement the principle of least privilege by defining specific actions and resources in IAM policies.
  • Regularly audit IAM policies using tools like AWS IAM Access Analyzer.
  • Enable AWS CloudTrail to monitor API calls and detect abnormal access patterns.

AWS Lambda Privilege Escalation

Overview of AWS Lambda

AWS Lambda is a serverless computing service that allows running code without provisioning or managing servers. While convenient, Lambda functions can introduce security vulnerabilities if permission boundaries are not properly defined.

Exploit Technique

An attacker can exploit Lambda functions with excessive permissions. For instance, a Lambda function with the following role configuration can lead to privilege escalation:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "s3:*",
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": "lambda:InvokeFunction",
      "Resource": "*"
    }
  ]
}

In this example, an attacker could use the function to invoke other functions with escalated privileges or access sensitive S3 data.

Real-World Exploit

A compromised Lambda function with excessive permissions was used by attackers to invoke other functions and create a cascade of privilege escalations across multiple AWS accounts.

Mitigation Strategies

  • Define precise IAM roles with limited permissions for Lambda functions.
  • Use Lambda permission boundaries to restrict actions that functions can perform.
  • Regularly review and update Lambda function configurations and associated roles.

Exploiting EC2 Metadata Service

EC2 Metadata Service Overview

The EC2 instance metadata service provides information about the instance, such as instance ID, security groups, and IAM roles. Improper access control can allow attackers to retrieve sensitive metadata and escalate privileges.

Attack Vector

Attackers can exploit scripts or applications running on EC2 instances that unintentionally expose access to metadata. For example, using a vulnerable web application running on an EC2 instance, an attacker can access the metadata service at http://169.254.169.254/latest/meta-data/.

Example Exploit

Using the following curl command, an attacker can retrieve instance metadata, including IAM role credentials:

curl http://169.254.169.254/latest/meta-data/iam/security-credentials/

This command returns sensitive information that can be used for privilege escalation.

Mitigation Strategies

  • Implement IAM roles for EC2 instances with the least privilege approach.
  • Restrict outbound network access from EC2 instances using security groups and network ACLs.
  • Use VPC endpoints and AWS Systems Manager to securely manage access to instance metadata.

Visualizing Privilege Escalation Paths

Understanding how these attacks unfold can be complex. Below is a mermaid diagram to illustrate potential privilege escalation paths in an AWS environment:

graph LR
    A[IAM User] -->|Excessive Permissions| B[IAM Role]
    B -->|Modify Policies| C[Lambda Function]
    C -->|Invoke Functions| D[Other AWS Services]
    A -->|Access Metadata| E[EC2 Instance]
    E -->|Retrieve Credentials| B

Defensive Recommendations

Implement Principle of Least Privilege

Ensure all IAM policies, roles, and permissions follow the principle of least privilege. Regularly review and update policies to minimize the risk of privilege escalation.

Regular Security Audits

Conduct regular security audits using AWS tools such as IAM Access Analyzer and AWS Trusted Advisor to identify and rectify misconfigurations.

Secure Lambda Functions

Define narrow permission boundaries for Lambda functions and use AWS Lambda's built-in security features to restrict unauthorized access.

Protect EC2 Metadata Service

Implement security controls around EC2 instance metadata access, including using IAM roles correctly and restricting network access.

Continuous Monitoring and Alerts

Use AWS CloudTrail and Amazon GuardDuty to monitor API calls and detect suspicious activities. Set up alerts for unauthorized access attempts or privilege escalation indicators.

By following these recommendations, you can significantly reduce the risk of privilege escalation in your AWS environment, ensuring robust security and protecting critical resources from potential threats.