crypto: fix build with OPENSSL_NO_ENGINE

[yselkowitz]

ENGINE was deprecated in openssl 3.0 (and disabled in RHEL 10), and completely removed in 4.0.

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Testing
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Documentation

• [N/A] Documentation required for this feature

Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Fixed compilation failures when OpenSSL is built without engine support enabled.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e4a9c845-6e4d-4814-89d7-e003bfa9cb65

📥 Commits

Reviewing files that changed from the base of the PR and between 1e69f37 and 0867fe5.

📒 Files selected for processing (3)

• include/fluent-bit/flb_crypto.h
• include/fluent-bit/flb_hash.h
• include/fluent-bit/flb_hmac.h

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📝 Walkthrough

Walkthrough

Three header files conditionally include OpenSSL's engine.h only when OPENSSL_NO_ENGINE is not defined, preventing compile errors in OpenSSL builds with engine support disabled.

Changes

OpenSSL Engine Include Guards

Layer / File(s)	Summary
Conditional Include Guards include/fluent-bit/flb_crypto.h, include/fluent-bit/flb_hash.h, include/fluent-bit/flb_hmac.h	OpenSSL engine.h includes wrapped in #ifndef OPENSSL_NO_ENGINE / #endif to prevent compilation failures when OpenSSL disables engine support.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Suggested labels

backport to v4.2.x

Suggested reviewers

• cosmo0920

Poem

🐰 Three headers stand in morning dew,
Guards now shield what engines do,
OpenSSL's dance, both on and off,
No more compilation scoff!
Hopping forward, clean and bright! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'crypto: fix build with OPENSSL_NO_ENGINE' directly and clearly describes the main objective of the changeset—making the build work when OPENSSL_NO_ENGINE is defined.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[cosmo0920]

It's really good to have. Nice work! 👍