Which is More Secure for Infrastructure Automation?

Gartner describes infrastructure as code (IaC) as a key way to unlock the potential of the cloud. However, some companies encounter challenges in IaC adoption, especially when it comes to maintaining a secure posture. As adopters automate their infrastructure deployments, they often encounter security issues associated with misconfigurations, code vulnerabilities, configuration shifts, secret management, and access control.

Two of the leading tools used in IaC are Ansible and Terraform. They both have noteworthy security features, and each has its own security issues that DevOps teams need to pay attention to, but is one more secure than the other? 

Let’s evaluate these infrastructure automation tools from a cybersecurity perspective, to gain insights into which might be the better fit for your organization.

Ansible and Terraform Overview

Before going into a detailed security comparison of Ansible and Terraform, here’s a quick rundown of their key features. The two have similarities, but they also offer distinct functions with overlapping purposes in infrastructure automation.

Ansible is an open-source automation solution designed to simplify many complex IT tasks involved in infrastructure management, including provisioning, configuration, the deployment of applications, orchestration, as well as compliance enforcement. 

The market leader, Terraform was likewise open source until the summer of 2023, when it switched to a highly restrictive business license model. With IBM’s acquisition of Terraform’s parent company Hashicorp in 2024, there has been much speculation in the tech community regarding the future of the product, especially as the lion’s share of its developer ecosystem has moved on to OpenTofu.

Terraform is notable for being based on “declarative” language, which describes the intended state of the infrastructure, as opposed to Ansible, which works on an “imperative” basis, whereby the code indicates steps or commands.

With both tools’ support for multi-cloud and on-premises environments, Ansible and Terraform are highly suitable for DevOps workflows. There are major differences in their security models, though.

Ansible Security Pros and Cons

One of the strongest security features of Ansible is its agentless architecture, significantly minimizing the potential attack surface. Agents can be exploited to expose hardcoded credentials, take advantage of misconfigurations, and stage supply chain attacks through compromised modules, plugins, and templates.

Additionally, Ansible comes with standard security functions, particularly the encryption of secrets and access controls. The Ansible Vault encrypts passwords, API keys, and other sensitive data. Ansible has a role-based access control (RBAC) system that is baked into the Ansible Automation Platform, specifically the Ansible Tower. 

It also provides pre-built security compliance playbacks that ascertain the enforcement of security policies. However, Ansible still leaves the possibility open for security vulnerabilities in the following areas: the use of unencrypted credentials in playbooks, reliance on SSH for remote execution, and the risk of privilege escalation. 

When configured incorrectly, Ansible Vault has been known to expose credentials in plain text during execution, which can expose sensitive data in YAML files. Meanwhile, misconfigurations in Sudo privileges can make for privilege escalation risks, allowing unauthorized users to execute privileged commands.

Terraform Security Pros and Cons

Terraform addresses some of the security challenges in Ansible. In particular, its combination of immutable infrastructure and declarative language makes configuration inconsistency and drift less likely. This immutability enables reproducibility, which means the consistent enforcement of security policies and easier validation of security configurations.

When it comes to secret management, Terraform integrates natively with Hashicorp Vault, but it can also work with AWS Secrets Manager and other security solutions. It can manage secrets via “providers.” This means flexibility in managing sensitive data.

Terraform enforces the principle of least privilege with its Identity and Access Management (IAM) policies. It is designed to only provide the permission required to undertake a specific operation.

Moreover, Terraform now supports encryption for state files, a crucial component in infrastructure management. This file contains the details of the current state of a managed infrastructure, serving as a link between the infrastructure configuration and real-world resources. The problem with state file encryption, however, is that it is not automatic. If the state file is exposed without encryption, sensitive data such as API keys and credentials can be compromised. 

It is also worth noting that, unlike Ansible, Terraform lacks a native RBAC system. Its enforcement of access control is through external cloud provider policies. Additionally, managing dependencies can be quite complex with Terraform. It is crucial to properly define dependencies to avoid insecure configurations as well as the unintended deletion of resources.

Which Platform Is More Secure?

Both Ansible and Terraform offer strong security capabilities, but they have their respective limitations. Users can overcome these limitations by mastering proper configuration and enforcing security best practices. There is no definite answer as to which infrastructure automation tool is better from a security perspective.

Ansible is generally more suitable for secure configuration management in existing systems, as well as for compliance enforcement, because of its agentless execution and robust native RBAC. It is a good choice for handling legacy infrastructure management.

Meanwhile, Terraform has some key advantages for secure infrastructure provisioning because of its declarative language and immutability. It excels at provisioning new infrastructure built from scratch. Terraform is great at creating identical predictable environments, which makes it the preferred choice for those who repetitively set up development, testing, and production environments.

This is not to say that Ansible cannot be a good tool for scenarios where Terraform is deemed preferable and vice versa. They both offer a degree of flexibility, making them valid infrastructure automation solutions for various use cases. Ansible’s automation capabilities go beyond configuration management, while Terraform’s modular design enables code reuse and scalable infrastructure configurations.

Can Ansible and Terraform Be Used Together?

It is not necessary to only choose one between Ansible and Terraform – they can actually be used together in modern infrastructure management. Terraform handles the provisioning of the underlying infrastructure, while Ansible configures the operating system and the installation and deployment of applications. 

For example, your team might use Terraform to provision a set of EC2 instances on AWS, while preferring Ansible for the installation and configuration of a web server in the same set of EC2 instances.

Ansible and Terraform can be a great duo for infrastructure automation, as they complement each other’s strengths. They can be great tools for accelerating cloud-based development processes. However, if the goal is only to prevent configuration drift, Terraform alone is already enough. In the same vein, if the main concern is continuous compliance and software deployment, Ansible alone suffices.

In Conclusion

Ansible and Terraform are excellent tools for secure infrastructure automation. They can be used individually or together to maximize the benefits. Using both of them may not be cost-efficient, though. In deciding which one to use, it is important to carefully examine the operational goals and your DevOps team’s security workflows.

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