Periodically audit your servers using automated tools to ensure no static AWS configuration files are lingering on production disks.
Some PHP or web applications allow including local files via parameters like ?page=home . If the application does not sanitize input, an attacker might try:
: Attackers can bypass firewalls to access internal metadata services (like the AWS Instance Metadata Service at 169.254.169.254 ). 3. Critical Prevention Measures
When you decode fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig , it translates into the local file path:
Sanitize and validate all user inputs in web applications. Never allow end-user inputs to directly dictate the backend's URL-fetching or file-retrieval mechanisms (e.g., disallowing the file:// scheme entirely). fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig
: A common function or parameter name in web applications used to retrieve content from a remote or local source.
The specific format provided is highly URL-encoded to bypass simple security filters: : : (Colon) 2F : / (Forward slash) file-3A-2F-2F-2F : Decodes to file:/// root-2F.aws-2Fconfig : Decodes to root/.aws/config Common Use Cases in Write-ups
: The path /root/.aws/config is a high-value target because it is the default location for AWS CLI configuration. Gaining access to this file can provide an attacker with the necessary context to move laterally within a cloud environment. Why This is Dangerous
The following example demonstrates how a poorly configured back-end script allows this type of file fetching exploit to succeed: Periodically audit your servers using automated tools to
: It reveals the naming conventions of specific roles (e.g., production-admin , db-backup-role ) configured on the machine.
Even without the credentials file, config can provide valuable information – default regions, named profiles, and sometimes hardcoded assume-role ARNs that can be used in further attacks.
# Vulnerable Python code import requests url = request.GET['url'] response = requests.get(url) # url = file:///root/.aws/config
# Lists buckets in the default region aws s3 ls : A common function or parameter name in
fetch-url-file:///root/aws/config
[default] region = us-east-1 output = json [profile production-admin] region = us-west-2 output = text Use code with caution.
If the file config is accessible, it often points to or includes the credentials file, which literally holds aws_access_key_id and aws_secret_access_key .