Python: Allow models-as-data sanitizers and convert 1 existing sanitizer

[owen-mc]

Note the commit "Fix implementation of barrierNode for barrier models" was needed to make the commit "Convert Flask path-injection sanitizer to MaD" work. I am not certain that it is the correct approach, so please review this carefully.

Also carefully review the MaD that I wrote, as I have no experience with MaD for dynamic languages.

There are two other sanitizers which seemed convertible, but only sanitize certain flow-states. We could in future extend the url-redirection kind string to make it possible to specify this. This would have a much greater benefit if the use of flow states for URL redirection is first implemented for all languages.

[Copilot]

Pull request overview

This PR enables models-as-data (MaD) sanitizers for Python security queries and converts the Flask path-injection sanitizer from CodeQL to a MaD model. The key change is fixing the barrierNode implementation to use asSink() instead of asSource(), which correctly identifies where data flows into sanitizing functions.

Changes:

• Fixed barrierNode implementation in ApiGraphModels.qll to use asSink() for proper barrier node identification
• Converted Flask send_from_directory filename sanitizer from CodeQL class to MaD YAML model
• Added SanitizerFromModel classes across 8 security query customization files to support MaD-defined sanitizers
• Added CredentialSanitizer class in HardcodedCredentials.ql to support credential-specific MaD sanitizers

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModels.qll	Fixed barrierNode to use asSink() instead of asSource() for correct identification of nodes where data flows into barriers
python/ql/lib/semmle/python/frameworks/Flask.qll	Removed FlaskSendFromDirectoryCallFilenameSanitizer class (converted to MaD)
python/ql/lib/semmle/python/frameworks/Flask.model.yml	Added MaD barrier model for Flask send_from_directory filename argument
python/ql/lib/semmle/python/security/dataflow/UrlRedirectCustomizations.qll	Clarified comment that SanitizerFromModel sanitizes all flow states
python/ql/lib/semmle/python/security/dataflow/UnsafeDeserializationCustomizations.qll	Added SanitizerFromModel class for unsafe-deserialization kind
python/ql/lib/semmle/python/security/dataflow/SqlInjectionCustomizations.qll	Added SanitizerFromModel class for sql-injection kind
python/ql/lib/semmle/python/security/dataflow/ReflectedXSSCustomizations.qll	Added SanitizerFromModel class for html-injection and js-injection kinds
python/ql/lib/semmle/python/security/dataflow/PathInjectionCustomizations.qll	Added SanitizerFromModel class for path-injection kind
python/ql/lib/semmle/python/security/dataflow/LogInjectionCustomizations.qll	Added SanitizerFromModel class for log-injection kind
python/ql/lib/semmle/python/security/dataflow/CommandInjectionCustomizations.qll	Added SanitizerFromModel class for command-injection kind
python/ql/lib/semmle/python/security/dataflow/CodeInjectionCustomizations.qll	Added SanitizerFromModel class for code-injection kind
python/ql/src/Security/CWE-798/HardcodedCredentials.ql	Added CredentialSanitizer class to support MaD barriers for credential sinks

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