fix: only count real boundary parameters in the multipart C-T header

[fzipi]

What

Multipart::count_boundary_params (src/request_body_processor/multipart.cc) now only counts an occurrence of boundary when it is a parameter name: at the start of the string or right after ; or whitespace, and followed by optional blanks and =.

Why

The old loop counted every boundary that had an = anywhere later in the string. With Firefox's default boundary and the charset parameter that Spring Cloud Gateway appends:

Content-Type: multipart/form-data;boundary=----geckoformboundary4a7acee3709293e183ef2932a147a331;charset=UTF-8

the boundary inside the value plus the = of charset=UTF-8 made the count 2, so the request body failed with Multipart: Multiple boundary parameters in C-T. and rule 200002 of the recommended configuration blocked it.

The other two callers (the "boundary value contains boundary=" check and the case-sensitivity check) keep their behaviour, since both look for boundary used as a parameter name.

Tests

New test/test-cases/regression/request-body-parser-multipart-boundary-count.json (registered in test/test-suite.in):

1. The reporter's header (word boundary inside the value, followed by charset) parses and the body rule fires → 403 (failed before: 400 from REQBODY_PROCESSOR_ERROR).
2. A value that starts with the word boundary, followed by charset → 403 (failed before: 400).
3. Two real boundary parameters are still rejected → 400 with Multiple boundary parameters in C-T.
4. Same with whitespace before the second = → still rejected.

Existing request-body-parser-multipart.json still passes. make check passes except the 9 pre-existing removeComments.json failures from the local submodule mismatch.

References

Fixes #3610

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Multipart requests now distinguish boundary parameters from text that merely contains “boundary,” reducing incorrect parameter counts.
  • Boundary parameters with whitespace before the equals sign are recognized correctly, and requests with multiple boundary parameters are identified as such.

[coderabbitai]

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ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 9767d67 and 3283c38.

📒 Files selected for processing: 2

• src/request_body_processor/multipart.cc
• test/test-cases/regression/request-body-parser-multipart-boundary-count.json

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📝 Walkthrough

The multipart parser now counts boundary only when it starts a parameter name and is followed, after optional whitespace, by =. Five regression cases cover boundary-like text in values and multiple boundary parameters.

Changes: Multipart boundary counting

Layer / File(s)	Summary
Boundary counting and regression coverage src/request_body_processor/multipart.cc, test/test-cases/regression/request-body-parser-multipart-boundary-count.json, test/test-suite.in	The counter recognizes boundary at the start of the header or after a semicolon or whitespace, with optional whitespace before =. Regression cases cover boundary-like text in values, charset parameters, duplicate boundary parameters, and whitespace before =. The test suite registers the new cases.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: airween

Merge Risk: ⚪ Minimal · up to 3283c

No unresolved issue was identified that would prevent merging after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: counting only valid boundary parameters in multipart Content-Type headers.
Linked Issues check		Issue #3610 requires the multipart parser to accept a Content-Type value where boundary occurs inside the boundary value and a later charset parameter contains =. The production change counts …
Out of Scope Changes check		The whole-PR diff contains one focused parser change, one focused regression test file, and its test-suite registration. The duplicate-parameter cases preserve required behavior and support issue #361…

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
Review comments at @src/request_body_processor/multipart.cc:
- Around line 1360-1363: Update the parameter whitespace scan in the counter
around param_start to match the whitespace accepted by Multipart::init,
including vertical tab, or make both parsing and counting reject it. Ensure
duplicate boundary parameters separated by that whitespace are counted
consistently.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 269bb553-c766-45ec-be5e-33f758e43192

📥 Commits

Reviewing files that changed from the base of the PR and between 48e561b and 9767d67.

📒 Files selected for processing (3)

• src/request_body_processor/multipart.cc
• test/test-cases/regression/request-body-parser-multipart-boundary-count.json
• test/test-suite.in

Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 4 remain after this review.

[fzipi]

Agreed: Multipart::init accepts any isspace() character between the parameter name and the =, so the counter now uses isspace() for both the character before boundary and the run before = (6dde795). Added case 5 with boundary=0000; boundary<VT>=1111, which was counted as one parameter before the change and is rejected again now.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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