The Seven Sins: Security Smells in Infrastructure as Code Scripts

Reviewed by Brij Patel / 2021-11-23
Keywords: Devops, Infrastucture as code, Security Smell

Developers use infrastructure as code (IaC) scripts to provision servers and development environments. As with any code, they may unintentionally create security holes while writing these scripts. The purpose of Rahman2019 is to help them avoid doing this by analyzing real IaC scripts to identify security smells and developing a static analysis tool to identify occurrences.

The authors started by collecting 1726 Puppet scripts from 74 repositories belonging to Mozilla, OpenStack, and Wikimedia Commons. By performing a qualitative analysis on these scripts, the authors identified seven smells:

  • admin by default
  • empty password
  • hard-coded secret
  • invalid IP address binding
  • suspicious comment
  • use of HTTP without TLS
  • use of weak cryptography algorithms

They then built a tool called Security Linter for Infrastructure as Code Scripts (SLIC) to spot occurrence of these smell, which they then ran on 15,2322 IaC scripts collected from 293 open source repositories. To evaluate SLIC's accuracy, the authors constructed an oracle dataset consisting of 140 scripts which were manually checked for security smells by 28 graduate students working in pairs. Using this dataset, the average precision and recall of SLIC were both 0.99.

The authors acknowledge that other security smells may exist, and that because their dataset focused on Puppet (which uses a declarative language) it might not apply to IaC scripts written in imperative languages. Those caveats aside, their work shows clearly that IaC can be checked as effectively as any other kind of code.

Rahman2019 Akond Rahman, Chris Parnin, and Laurie Williams: "The Seven Sins: Security Smells in Infrastructure as Code Scripts". Proc. International Conference on Software Engineering (ICSE), 2019, 10.1109/icse.2019.00033.

Practitioners use infrastructure as code (IaC) scripts to provision servers and development environments. While developing IaC scripts, practitioners may inadvertently introduce security smells. Security smells are recurring coding patterns that are indicative of security weakness and can potentially lead to security breaches. The goal of this paper is to help practitioners avoid insecure coding practices while developing infrastructure as code (IaC) scripts through an empirical study of security smells in IaC scripts. We apply qualitative analysis on 1,726 IaC scripts to identify seven security smells. Next, we implement and validate a static analysis tool called Security Linter for Infrastructure as Code scripts (SLIC) to identify the occurrence of each smell in 15,232 IaC scripts collected from 293 open source repositories. We identify 21,201 occurrences of security smells that include 1,326 occurrences of hard-coded passwords. We submitted bug reports for 1,000 randomly-selected security smell occurrences. We obtain 212 responses to these bug reports, of which 148 occurrences were accepted by the development teams to be fixed. We observe security smells can have a long lifetime, e.g., a hard-coded secret can persist for as long as 98 months, with a median lifetime of 20 months.