Understanding the AWS IMDSv2 Token Fetch Command: curl 169.254.169
The IP address is a link-local address used by AWS to provide the Instance Metadata Service (IMDS) . Every EC2 instance can query this address to retrieve information about itself—such as its instance ID, public IP, IAM role credentials, and security groups—without needing to call the AWS API externally. The Evolution: From IMDSv1 to IMDSv2
: You include that token in the header of all subsequent metadata requests. Breaking Down the Command curl-url-http-3A-2F-2F169.254.169.254-2Flatest-2Fapi-2Ftoken
The command curl -X PUT "http://169.254.169" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600" is a critical component of modern cloud security within Amazon Web Services (AWS). It represents the transition from the legacy Instance Metadata Service Version 1 (IMDSv1) to the more secure . What is 169.254.169.254?
: You must first perform a PUT request to /latest/api/token to generate a temporary session token. Understanding the AWS IMDSv2 Token Fetch Command: curl 169
: IMDSv2 requires a PUT request to ensure that simple GET-based SSRF vulnerabilities cannot trigger a token generation.
When you see the string curl-url-http-3A-2F-2F169.254.169.254-2Flatest-2Fapi-2Ftoken (which is a URL-encoded version of the path), it refers to this specific two-step process. Step 1: Generate the Token Breaking Down the Command The command curl -X
Once you have the $TOKEN , you can access the metadata safely:
The path http://169.254.169 is the gateway to secure instance management in AWS. If you are building or maintaining cloud infrastructure, ensuring your instances are configured to is a foundational security best practice that prevents credential theft via common web vulnerabilities.
: Defines how long the token is valid (in this case, 21,600 seconds or 6 hours). Step 2: Access Metadata