Prevent atom DoS vulnerabilities by avoiding String.to_atom/1

[Kavignon]

Description

Atoms are not garbage-collected, which can lead to memory exhaustion if many unique atoms are created dynamically.
It poses a security risk, as an attacker could exploit this to crash the application via a denial-of-service (DoS) attack.
To mitigate this, we should enforce safer practices in the template and educate developers on the risks and alternatives. The String.to_atom/1 function can lead to atom DoS vulnerabilities when used with untrusted or dynamic input, as atoms are not garbage-collected and can exhaust the BEAM's atom table.

For more information, see the Paraxial.io blog: Atom DoS: Exploiting the BEAM's Atom Table.

Tasks

• Configure credo to warn developers about String.to_atom/1.
• Add a CI step to check for occurrences of String.to_atom/1
• Find a way to propose using String.to_existing_atom/1 instead of String.to_atom/1.
• The blog suggests using a predefined map or ETS for safe string-to-atom conversions. Incorporate this as a utility in the template.
• Document the risks and alternatives in the README