LFI vulnerabilities occur when a web application includes a file based on user-supplied input without proper sanitization. For example:
php://filter/read=convert.base64-encode/resource=/root/.aws/credentials Let's break down this string piece by piece:
To bypass this and read the raw text of a file, attackers use the php://filter wrapper. By appending convert.base64-encode , the PHP engine encodes the target file's contents into a Base64 string before processing it. Because Base64 text cannot be executed as PHP code, the web server safely outputs the raw, encoded string directly to the attacker's browser. The attacker then decodes the string locally to read the plaintext file. 3. The Target: AWS Credentials File
The payload view.php?filter=read=convert.base64-encode/resource=/root/.aws/credentials is a potent reminder of how web-layer bugs can seamlessly transition into full cloud infrastructure takeovers. By modernizing your credential management via AWS IAM Roles and eliminating loose input controls within PHP code, you can nullify this entire class of cyber threats.
Preventing this type of attack requires robust input validation and server configuration. 1. Avoid Using User Input in File Inclusion LFI vulnerabilities occur when a web application includes
When a standard LFI vulnerability exists, requesting a .php or sensitive configuration file often causes the server to execute the code or fail silently due to syntax formatting.
: Ensure that even if a service account is compromised, its IAM policy restricts it only to the bare minimum actions required to function. 4. Detection and Monitoring
On Linux servers running AWS-managed applications or commands via the root user, this specific file contains plaintext AWS access keys: aws_access_key_id aws_secret_access_key aws_session_token (if temporary credentials are used) How the Attack Works
: Access to private Amazon S3 buckets, databases (RDS), or document stores. Because Base64 text cannot be executed as PHP
The web server user ( www-data or apache ) should not have read access to sensitive files, especially /root/ .
Title: Understanding the PHP Filter Exploit: -view-php-3A-2F-2Ffilter-2Fread-3Dconvert.base64 encode-2Fresource-3D-2Froot-2F.aws-2Fcredentials
Obtaining these credentials can allow an attacker to assume the root role, providing full access to AWS services, including S3 buckets, EC2 instances, and databases. Mitigation Strategies
If an attacker successfully extracts these strings, they gain programmatic access to the organization's AWS infrastructure. Depending on the Identity and Access Management (IAM) permissions tied to those keys, the attacker could: Exfiltrate proprietary databases or S3 buckets. Spin up unauthorized EC2 instances for crypto-mining. Delete entire cloud environments, acting as ransomware. From Identification to Mitigation The Target: AWS Credentials File The payload view
, by bypassing execution and outputting them in a machine-readable format. Payload Breakdown
: The specific filter chain instruction. It forces PHP to encode the targeted file's contents into Base64 text before rendering it to the screen.
If you're looking to implement a feature that allows you to read a file (in this case, AWS credentials) and encode its contents into base64, here's a basic PHP example: