EC2 instance using API keys

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Metadata

Id: 0b93729a-d882-4803-bdc3-ac429a21f158

Cloud Provider: AWS

Platform: Terraform

Severity: Low

Category: Access Control

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Description

EC2 instances should use IAM roles to be granted access to other AWS services. Storing AWS credentials directly in user data or on the instance, for example with environment variables such as AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY, as shown below, exposes sensitive credentials to anyone with access to the instance or the AWS console:

user_data = <<EOF
//!/bin/bash
apt-get install -y awscli
export AWS_ACCESS_KEY_ID=your_access_key_id_here
export AWS_SECRET_ACCESS_KEY=your_secret_access_key_here
EOF

This misconfiguration creates a significant security risk, as leaked credentials can be used by attackers to gain unauthorized access to AWS resources and potentially compromise the wider AWS environment. Instead, EC2 instances should be granted permissions using IAM roles via the iam_instance_profile attribute, which securely delivers temporary credentials to the instance and removes the need to manually manage or expose AWS keys.

Compliant Code Examples

provider "aws" {
  region = "us-east-1"
}

resource "aws_iam_role_policy_attachment" "test_attach" {
  roles      = [aws_iam_role.test_role.name]
  policy_arn = aws_iam_policy.test_policy.arn
}

resource "aws_iam_policy" "test_policy" {
  name = "test_policy"
  description = "test policy"
  path = "/"
  policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
      {
          "Action": [
              "s3:Get*",
              "s3:List*"
          ],
          "Effect": "Allow",
          "Resource": "*"
      }
  ]
}
EOF
}

resource "aws_iam_role" "test_role" {
  name = "test_role"
  path = "/"

  assume_role_policy = <<EOF
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": "sts:AssumeRole",
            "Principal": {
               "Service": "ec2.amazonaws.com"
            },
            "Effect": "Allow",
            "Sid": ""
        }
    ]
}
EOF
}

resource "aws_iam_instance_profile" "test_profile" {
  name = "test_profile"
  role = aws_iam_role.role.name
}

resource "aws_instance" "negative3" {
  ami           = "ami-005e54dee72cc1d00" # us-west-2
  instance_type = "t2.micro"

  tags = {
    Name = "test"
  }

  iam_instance_profile = aws_iam_instance_profile.test_profile.name

  credit_specification {
    cpu_credits = "unlimited"
  }

  user_data = <<-EOF
    #!/bin/bash
    apt-get update
  EOF
}

module "ec2_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 3.0"

  name = "single-instance"

  ami                    = "ami-ebd02392"
  instance_type          = "t2.micro"
  key_name               = "user1"
  monitoring             = true
  vpc_security_group_ids = ["sg-12345678"]
  subnet_id              = "subnet-eddcdzz4"

  tags = {
    Terraform   = "true"
    Environment = "dev"
  }
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_iam_role_policy_attachment" "test_attach" {
  roles      = [aws_iam_role.test_role.name]
  policy_arn = aws_iam_policy.test_policy.arn
}

resource "aws_iam_policy" "test_policy" {
  name = "test_policy"
  description = "test policy"
  path = "/"
  policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
      {
          "Action": [
              "s3:Get*",
              "s3:List*"
          ],
          "Effect": "Allow",
          "Resource": "*"
      }
  ]
}
EOF
}

resource "aws_iam_role" "test_role" {
  name = "test_role"
  path = "/"

  assume_role_policy = <<EOF
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": "sts:AssumeRole",
            "Principal": {
               "Service": "ec2.amazonaws.com"
            },
            "Effect": "Allow",
            "Sid": ""
        }
    ]
}
EOF
}

resource "aws_iam_instance_profile" "test_profile" {
  name = "test_profile"
  role = aws_iam_role.role.name
}

resource "aws_instance" "negative1" {
  ami           = "ami-005e54dee72cc1d00" # us-west-2
  instance_type = "t2.micro"

  tags = {
    Name = "test"
  }

  iam_instance_profile = aws_iam_instance_profile.test_profile.name

  credit_specification {
    cpu_credits = "unlimited"
  }
}

Non-Compliant Code Examples

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "positive6" {
  ami           = "ami-005e54dee72cc1d00" # us-west-2
  instance_type = "t2.micro"

  tags = {
    Name = "test"
  }

  user_data = <<EOT
#cloud-config
repo_update: true
repo_upgrade: all

packages:
 - awscli

runcmd:
 - [ sh, -c, "echo export AWS_ACCESS_KEY_ID=my-key-id >> ~/.bashrc" ]
 - [ sh, -c, "echo export AWS_SECRET_ACCESS_KEY=my-secret >> ~/.bashrc" ]
EOT

  credit_specification {
    cpu_credits = "unlimited"
  }
}

module "ec2_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 3.0"

  name = "single-instance"

  ami                    = "ami-ebd02392"
  instance_type          = "t2.micro"
  key_name               = "user1"
  monitoring             = true
  vpc_security_group_ids = ["sg-12345678"]
  subnet_id              = "subnet-eddcdzz4"

  user_data_base64 = var.init_aws_cli


  tags = {
    Terraform   = "true"
    Environment = "dev"
  }
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "positive2" {
  ami           = "ami-005e54dee72cc1d00" # us-west-2
  instance_type = "t2.micro"

  tags = {
    Name = "test"
  }

  user_data = <<EOT
#!/bin/bash
apt-get install -y awscli
cat << EOF > ~/.aws/config
[default]
aws_access_key_id = somekey
aws_secret_access_key = somesecret
EOF
EOT

  credit_specification {
    cpu_credits = "unlimited"
  }
}