User data contains encoded private key

Docs > Datadog Security > Code Security > Infrastructure as Code (IaC) Security > IaC Security Rules > User data contains encoded private key

Metadata

Id: terraform-aws-user-data-contains-encoded-private-key

Provider: AWS

Platform: Terraform

Severity: High

Category: Encryption

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Provider Reference

Description

AWS Launch Configuration’s user_data_base64 field should never contain private keys, even if base64 encoded, as this encryption method can be easily reversed by attackers. When private keys are exposed in user data, they can be extracted from the instance metadata or discovered through AWS API calls, compromising the security of all systems using those credentials. Instead of embedding private keys directly in user data, as shown in the insecure example user_data_base64 = "LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpzb21lS2V5", use AWS secrets management services like AWS Secrets Manager or Systems Manager Parameter Store, or implement a secure alternative where private keys are safely retrieved during instance startup.

Compliant Code Examples

resource "aws_launch_configuration" "negative1" {
  image_id      = data.aws_ami.ubuntu.id
  instance_type = "m4.large"
  spot_price    = "0.001"

  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_launch_configuration" "negative2" {
  image_id      = data.aws_ami.ubuntu.id
  instance_type = "m4.large"
  spot_price    = "0.001"
  user_data_base64 = ""

  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_launch_configuration" "negative3" {
  image_id      = data.aws_ami.ubuntu.id
  instance_type = "m4.large"
  spot_price    = "0.001"
  user_data_base64 = "dGVzdA=="
  
  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_launch_configuration" "negative4" {
  image_id      = data.aws_ami.ubuntu.id
  instance_type = "m4.large"
  spot_price    = "0.001"
  user_data_base64 = null
  
  lifecycle {
    create_before_destroy = true
  }
}

module "asg" {
  source = "terraform-aws-modules/autoscaling/aws"
  version = "1.0.4"

  # Launch configuration
  lc_name = "example-lc"

  image_id        = "ami-ebd02392"
  instance_type   = "t2.micro"
  security_groups = ["sg-12345678"]

  ebs_block_device = [
    {
      device_name           = "/dev/xvdz"
      volume_type           = "gp2"
      volume_size           = "50"
      delete_on_termination = true
    },
  ]

  root_block_device = [
    {
      volume_size = "50"
      volume_type = "gp2"
    },
  ]

  # Auto scaling group
  asg_name                  = "example-asg"
  vpc_zone_identifier       = ["subnet-1235678", "subnet-87654321"]
  health_check_type         = "EC2"
  min_size                  = 0
  max_size                  = 1
  desired_capacity          = 1
  wait_for_capacity_timeout = 0

  tags = [
    {
      key                 = "Environment"
      value               = "dev"
      propagate_at_launch = true
    },
    {
      key                 = "Project"
      value               = "megasecret"
      propagate_at_launch = true
    },
  ]
}

module "asg" {
  source = "terraform-aws-modules/autoscaling/aws"
  version = "1.0.4"

  # Launch configuration
  lc_name = "example-lc"

  image_id        = "ami-ebd02392"
  instance_type   = "t2.micro"
  security_groups = ["sg-12345678"]
  user_data_base64 = ""

  ebs_block_device = [
    {
      device_name           = "/dev/xvdz"
      volume_type           = "gp2"
      volume_size           = "50"
      delete_on_termination = true
    },
  ]

  root_block_device = [
    {
      volume_size = "50"
      volume_type = "gp2"
    },
  ]

  # Auto scaling group
  asg_name                  = "example-asg"
  vpc_zone_identifier       = ["subnet-1235678", "subnet-87654321"]
  health_check_type         = "EC2"
  min_size                  = 0
  max_size                  = 1
  desired_capacity          = 1
  wait_for_capacity_timeout = 0

  tags = [
    {
      key                 = "Environment"
      value               = "dev"
      propagate_at_launch = true
    },
    {
      key                 = "Project"
      value               = "megasecret"
      propagate_at_launch = true
    },
  ]
}

Non-Compliant Code Examples

resource "aws_launch_configuration" "positive1" {
  image_id      = data.aws_ami.ubuntu.id
  instance_type = "m4.large"
  spot_price    = "0.001"
  user_data_base64 = "LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpzb21lS2V5" # someKey

  lifecycle {
    create_before_destroy = true
  }
}

module "positive2" {
  source = "terraform-aws-modules/autoscaling/aws"
  version = "1.0.4"

  # Launch configuration
  lc_name = "example-lc"

  image_id        = "ami-ebd02392"
  instance_type   = "t2.micro"
  security_groups = ["sg-12345678"]
  user_data_base64 = "LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpzb21lS2V5"

  ebs_block_device = [
    {
      device_name           = "/dev/xvdz"
      volume_type           = "gp2"
      volume_size           = "50"
      delete_on_termination = true
    },
  ]

  root_block_device = [
    {
      volume_size = "50"
      volume_type = "gp2"
    },
  ]

  # Auto scaling group
  asg_name                  = "example-asg"
  vpc_zone_identifier       = ["subnet-1235678", "subnet-87654321"]
  health_check_type         = "EC2"
  min_size                  = 0
  max_size                  = 1
  desired_capacity          = 1
  wait_for_capacity_timeout = 0

  tags = [
    {
      key                 = "Environment"
      value               = "dev"
      propagate_at_launch = true
    },
    {
      key                 = "Project"
      value               = "megasecret"
      propagate_at_launch = true
    },
  ]
}

module "positive3" {
  source = "terraform-aws-modules/autoscaling/aws"
  version = "1.0.4"

  # Launch configuration
  lc_name = "example-lc"

  image_id        = "ami-ebd02392"
  instance_type   = "t2.micro"
  security_groups = ["sg-12345678"]
  user_data_base64 = "LS0tLS1CRUdJTiBPUEVOU1NIIFBSSVZBVEUgS0VZIEJMT0NLLS0tLS0="

  ebs_block_device = [
    {
      device_name           = "/dev/xvdz"
      volume_type           = "gp2"
      volume_size           = "50"
      delete_on_termination = true
    },
  ]

  root_block_device = [
    {
      volume_size = "50"
      volume_type = "gp2"
    },
  ]

  # Auto scaling group
  asg_name                  = "example-asg"
  vpc_zone_identifier       = ["subnet-1235678", "subnet-87654321"]
  health_check_type         = "EC2"
  min_size                  = 0
  max_size                  = 1
  desired_capacity          = 1
  wait_for_capacity_timeout = 0

  tags = [
    {
      key                 = "Environment"
      value               = "dev"
      propagate_at_launch = true
    },
    {
      key                 = "Project"
      value               = "megasecret"
      propagate_at_launch = true
    },
  ]
}