fix: improve gzip request decompression middleware

[endigma]

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of compressed request bodies to ensure proper resource cleanup and prevent potential decompression attacks.
  • Adjusted middleware order to enforce request size limits after decompression, enhancing security for compressed requests.

• Tests

  • Added tests to verify that oversized plain and compressed request bodies are correctly rejected.
  • Refactored existing compression middleware tests for improved clarity and reliability.

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[coderabbitai]

"""

Walkthrough

The changes update middleware ordering to apply request size limiting after decompression, preventing decompression attacks. The compression middleware now closes the original request body properly and clears content length headers. Compression middleware tests are refactored for clarity and correctness, and new tests verify enforcement of request size limits, including for compressed requests.

Changes

Files/Groups	Change Summary
router/core/graph_server.go	Changed middleware order: request size limiting is now after decompression; updated related comment.
router/internal/middleware/compression.go	Closed original request body after gzip reader; added error logging on close failure; cleared content length.
router/internal/middleware/compression_test.go	Refactored tests: replaced http.NewRequest with httptest.NewRequest, changed buffer type, reordered imports.
router/internal/middleware/request_size_test.go	Added new tests for request size limiting and gzip decompression handling in middleware.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes
"""

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Reviewing files that changed from the base of the PR and between 91cd223 and 87c5bee.

📒 Files selected for processing (1)

• router/internal/middleware/compression.go (2 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• router/internal/middleware/compression.go

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[github-actions]

Router-nonroot image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-1dccca57cb10c0551bc39b74b9e3acdaa8f98709-nonroot

[Noroth]

I think this solution will not prevent scenarios with excessively large requests that could potentially cause the router to be oom killed in the worst case.

We could make use of something like

• https://pkg.go.dev/net/http#MaxBytesReader
• https://pkg.go.dev/io#LimitedReader

[endigma]

@coderabbitai review

[coderabbitai]

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Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[StarpTech]

I think this solution will not prevent scenarios with excessively large requests that could potentially cause the router to be oom killed in the worst case.

We have this already in place. @endigma is the order right?

[endigma]

I think this solution will not prevent scenarios with excessively large requests that could potentially cause the router to be oom killed in the worst case.

We have this already in place. @endigma is the order right?

I fixed the order in the PR, it now goes Limit(Decompress(r.Body)), so the limited reader wraps the gzip reader instead of vice versa

[StarpTech]

LGTM

[ysmolski]

LGTM, thank you @endigma for the patience and time.