Use Safe Defaults for lxml Parsers

[pixeebot]

This codemod configures safe parameter values when initializing lxml.etree.XMLParser, lxml.etree.ETCompatXMLParser, lxml.etree.XMLTreeBuilder, or lxml.etree.XMLPullParser. If parameters resolve_entities, no_network, and dtd_validation are not set to safe values, your code may be vulnerable to entity expansion attacks and external entity (XXE) attacks.

Parameters no_network and dtd_validation have safe default values of True and False, respectively, so this codemod will set each to the default safe value if your code has assigned either to an unsafe value.

Parameter resolve_entities has an unsafe default value of True. This codemod will set resolve_entities=False if set to True or omitted.

The changes look as follows:

  import lxml.etree

- parser = lxml.etree.XMLParser()
- parser = lxml.etree.XMLParser(resolve_entities=True)
- parser = lxml.etree.XMLParser(resolve_entities=True, no_network=False, dtd_validation=True)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False, no_network=True, dtd_validation=False)

More reading

• https://lxml.de/apidoc/lxml.etree.html#lxml.etree.XMLParser
• https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing
• https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html

I have additional improvements ready for this repo! If you want to see them, leave the comment:

@pixeebot next

... and I will open a new PR right away!

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Feedback | Community | Docs | Codemod ID: pixee:python/safe-lxml-parser-defaults

[dryrunsecurity]

DryRun Security Summary

The pull request addresses a critical XML External Entity (XXE) Injection vulnerability by modifying the XML parser configuration to set resolve_entities=False, thereby preventing potential security risks associated with resolving external entities.

Expand for full summary

Summary:

The code change in this pull request addresses a critical security vulnerability by modifying the XML parser configuration to set resolve_entities=False instead of the previous resolve_entities=True. This change is a significant security improvement, as it mitigates the risk of XML External Entity (XXE) Injection attacks.

XXE Injection is a type of attack where an attacker can leverage the XML parser's ability to resolve external entities to read sensitive files, perform server-side request forgery (SSRF), or even execute arbitrary code on the server. By setting resolve_entities=False, the parser will no longer attempt to resolve external entities, effectively preventing this vulnerability from being exploited. This is a recommended security practice when parsing XML data to prevent XXE Injection attacks.

Overall, this code change demonstrates the developer's effort to enhance the application's security by addressing a critical security concern. The change is a positive step towards improving the overall security posture of the application.

Files Changed:

• insecure-app/app.py: The developer has modified the XML parser configuration to set resolve_entities=False instead of the previous resolve_entities=True. This change addresses a potential XML External Entity (XXE) Injection vulnerability by preventing the parser from resolving external entities, which could have been exploited by attackers to gain unauthorized access to sensitive information or perform other malicious actions.

Code Analysis

We ran 9 analyzers against 1 file and 0 analyzers had findings. 9 analyzers had no findings.

View PR in the DryRun Dashboard.

[pixeebot]

I'm confident in this change, but I'm not a maintainer of this project. Do you see any reason not to merge it?

If this change was not helpful, or you have suggestions for improvements, please let me know!

[pixeebot]

Just a friendly ping to remind you about this change. If there are concerns about it, we'd love to hear about them!