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IMDSv1 enabled

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Metadata

Id: terraform-aws-imdsv1-is-enabled

Provider: AWS

Platform: Terraform

Severity: High

Category: Best Practices

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Description

AWS Instance Metadata Service Version 1 (IMDSv1) is susceptible to Server-Side Request Forgery (SSRF) attacks, which can allow attackers to access instance metadata and potentially steal credentials or sensitive information from EC2 instances. IMDSv2 mitigates this risk by requiring session tokens for metadata requests, providing an additional layer of protection against SSRF vulnerabilities. To secure your infrastructure, set http_tokens to "required" in your AWS instance or launch template metadata options, as shown in the following example:

resource "aws_instance" "secure_example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "required"  // Secure configuration
  }
}

Compliant Code Examples

resource "aws_instance" "good_example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "required" # ✅ Secure
  }
}

resource "aws_launch_template" "good_example" {
  name_prefix   = "example"
  image_id      = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "required" # ✅ Secure
  }
}

Non-Compliant Code Examples

# Test case 2: aws_instance with incorrect http_tokens = "optional"
resource "aws_instance" "bad_example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "optional" # ❌ Should be "required"
  }
}

# Test case 3: aws_launch_template with incorrect http_tokens = "optional"
resource "aws_launch_template" "bad_example" {
  name_prefix   = "example"
  image_id      = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "optional" # ❌ Should be "required"
  }
}

# Test case 1: Missing metadata_options entirely (should trigger this resource to be flagged by security checks)
resource "aws_launch_template" "missing_metadata_options" {
  name_prefix   = "missing-metadata"
  image_id      = "ami-123456"
  instance_type = "t2.micro"
}

resource "aws_launch_template" "good_example" {
  name_prefix   = "secure"
  image_id      = "ami-123456"
  instance_type = "t2.micro"

  metadata_options {
    http_tokens = "required" # ✅ Correct value
  }
}