Cloud metadata is a set of information about the infrastructure, services, and resources of a cloud environment, and it can be exposed by cloud service providers. If you’re using a cloud service provider, it’s essential to understand how to manage and secure cloud metadata as a crucial aspect of cloud security. While it is not usually considered as a sensitive target, attackers can utilize insecure it to identify potential attack vectors and obtain access to an organization’s cloud environment.

Continue reading to learn about the fundamentals of cloud metadata, including what it is, the security threats associated with it, and how to secure it.

What Is Cloud Metadata?

First, let’s define the “metadata”part. Metadata is data that describes other data in configuration settings or files that act as a structured reference.

Cloud metadata is simply information about the data in the cloud. Think of it as a label that tells you more about a resource’s attributes (such as its name, type, author, creation date, and so on). Essentially, it is information about the cloud environment, including virtual machines, storage, networks, and apps.

Cloud metadata is important because it assists cloud service providers in maintaining, organizing, and delivering services to clients. When you upload a file to a cloud storage provider such as Dropbox or Google Drive, the cloud service provider generates information that allows you to locate and access the file later.

However, it is important to note that this data is not confined to cloud storage providers. Some of the most popular services available today include AWS Instance Metadata Service (IMDS), Azure Instance Metadata Service, Google Compute Engine Metadata Server, and Oracle Cloud Infrastructure Metadata Service. These services provide information on virtual machines, containers, applications, APIs, and other cloud resources.

How Is Metadata Used by Cloud Providers?

When we talk about cloud computing, we are essentially talking about a virtual space where we can store our files and data. However, did you know that cloud metadata plays a crucial role in cloud computing as well? Cloud providers use metadata to make cloud computing easier and more efficient.

First of all, it’s important to understand that metadata is stored independently of the actual files in the cloud. In other words, it’s additional information that helps users to identify, categorize, and manage the files they’ve stored. Metadata services in the cloud can include information such as CPU usage, network configurations, hostnames, and events.

Cloud providers also use this metadata to track and manage cloud instances more effectively. By analyzing metadata, cloud providers can gain valuable insights into how users are interacting with the cloud, which can be used to optimize cloud infrastructure and improve the user experience.

Examples of Cloud Metadata Services

Just like any other cloud computing service, the type of cloud metadata service you use is dependent on the cloud service provider you use. Here are some examples from popular cloud providers.

AWS Instance Metadata Service (IMDS)

AWS IMDS is used to retrieve instance metadata for EC2 instances and their environment. It provides a RESTful API that can be used to provide information such as the instance ID, IP address, security groups, and more.

For example, you can use AWS IMDS to retrieve security group data associated with a certain instance by running a simple HTTP request via the CLI:

curl http://169.254.169.254/latest/meta-data/security-groups
Code language: Perl (perl)

After running this request, the metadata output may look like the following if, for example, the given EC2 instance has 3 security groups:

Sg-0123456789abcdef0,sg-abcdef0123456789, sg-0123456789abcde86
Code language: Perl (perl)

The above output shows the specific IDs associated with the EC2 instance. This can help cloud administrators gain insights into the security posture of their cloud resources and ensure that only authorized traffic is allowed in and out of their EC2 instances.

Azure Instance Metadata Service

Azure Instance Metadata Service provides a RESTful API that allows Azure virtual machines to retrieve metadata about themselves, including network configuration, operating system settings, IP address, hostname, subscription ID, and SSH public keys.

Google Compute Engine Metadata Server

Google Compute Engine Metadata Server provides metadata about Google Cloud virtual machines. The metadata provides information about the instance, such as the instance name, IP address, machine type, network interface, and disk information.

Oracle Cloud Infrastructure Metadata Service

Oracle Cloud Infrastructure Metadata Service provides metadata about instances in Oracle Cloud Infrastructure. The metadata includes information such as instance ID, compartment ID, availability domain, and more.

What Kind of Metadata Is Exposed by Cloud Service Providers?

While metadata can be incredibly useful for cloud providers, it can also be used maliciously by attackers. By gaining access to cloud metadata, attackers can gather sensitive information about users and their cloud environment, potentially enabling them to launch targeted attacks.

Cloud service providers expose metadata such as instance metadata, user data, and event metadata.

• Instance Metadata includes information about the virtual machine instance, such as the instance ID, type, hostname, security group, and network configuration. An example of instance metadata might look like this:

{   "accountId": "123456789012",   "architecture": "x86_64",   "availabilityZone": "us-west-2b",   "billingProducts": null,   "devpayProductCodes": null,   "imageId": "ami-0c55b159cbfafe1f0",   "instanceId": "i-01234567890abcdef",   "instanceType": "t2.micro",   "kernelId": null,   "pendingTime": "2016-11-19T16:32:11Z",   "privateIp": "192.0.2.10",   "ramdiskId": null,   "region": "us-west-2", … …   " } 

• Event metadata is data generated by the cloud infrastructure during an event (such as instance creation or deletion). It can be used to audit or diagnose the cloud infrastructure. For example, if you wanted to retrieve event metadata related to an instance maintenance schedule, you could run the following command in your AWS CLI:

 $ aws ec2 describe-instance-metadata --metadata /meta-data/events/maintenance/scheduled/ Code language: Perl (perl)

This would then retrieve a JSON file containing the event metadata on the EC2 instance:

    	{
      "scheduledEvents": [
        {
          "notBefore": "2023-05-06T00:00:00Z",
          "description": "AWS is performing maintenance on the underlying host...",
          "code": "system-reboot",
          "notAfter": "2023-05-07T00:00:00Z"
        }
      ]
    }
Code language: Perl (perl)

• User Data is information entered by the user during the instance creation process that can be used to personalize the instance and run scripts during the boot-up process.

How Attackers Are Using Cloud Metadata

Cloud metadata (including IP addresses, machine types, user account information, virtual machine names, etc.) may supply attackers with the information they need to carry out phishing, brute-force, and credential-stuffing attacks.

Attackers can then utilize the mined metadata to create social engineering attacks that trick people into providing sensitive information. Using this data, attackers can easily construct targeted attacks that result in data breaches and other cybersecurity issues.

Securing Cloud Metadata: Best Practices

Cloud metadata must be secured for two reasons: first, it contains critical information about the data stored in the cloud; second, metadata can be used to track and manage cloud-based resources. We can use several techniques to secure our cloud metadata, including encryption, access controls (restricting permissions/using policies), and watermarking.

Access Controls: Restricting Permissions/Using Policies

Access control techniques (like permission restrictions and policy implementation) are one way to secure your cloud metadata. This is where cloud administrators create policies that govern who has access to metadata and what they can do with it. Access controls can prevent unauthorized access to metadata, minimizing the risk of data breaches.

For example, if you were to restrict the instance metadata query to only the root user, you could alter the IMDS configuration file on your EC2 instance to look like this:

{
  "mode": "strict",
  "default-credential-duration-seconds": 60,
  "default-token-duration-seconds": 300,
  "default-role": "aws-ec2-instance_connect",
  "default-IAM-role": "aws-ec2-instance_connect",
  "iam-role-endpoint": "http://169.254.169.254/latest/meta-data/iam/security-credentials/",
  "logging": {
    "destination": "file",
    "path": "/var/log/amazon/ssm/amazon-ssm-agent.log"
  },
  "allowed-roles": [
    {
      "name": "root",
      "credential-duration-seconds": 900,
      "token-duration-seconds": 1800
    }
  ]
}
Code language: Perl (perl)

Using Encryption

By utilizing encryption, you can prevent unauthorized access to crucial information stored in metadata. Cloud metadata that has been encrypted can only be accessed by persons with the proper authorization and access keys. You can encrypt your cloud metadata in a number of ways, such as by employing AES or RSA encryption methods.

Metadata Watermarking

The third strategy you can use to protect cloud information is watermarking. By adding distinguishing identifiers, metadata can be watermarked so that you can track down the source of any breaches or leaks. Watermarking can help detect unauthorized access to metadata and provide cloud administrators with the resources they need to take the necessary action. This technique can discourage attackers from attempting to steal or exploit metadata because the metadata can be traced back to its source.

Conclusion

Cloud metadata is a crucial component of cloud computing since it contains critical information about the configuration and status of cloud resources. Although cloud data is valuable to both customers and cloud service providers, attackers can use it to gain unauthorized access to cloud services. As we discussed in this guide, businesses must protect their metadata with encryption, access controls, and watermarking to stay on top of cloud infrastructure security.