fix(mysql): advertise CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA in server greeting

[renecannao]

Summary

• Advertise CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA (0x00200000) in the server greeting packet's extended_capabilities, making ProxySQL compatible with clients like Boost MySQL that require this capability flag before connecting.
• ProxySQL already correctly parses lenenc-encoded auth data from clients (MySQL_Protocol.cpp:1708); it just never advertised the flag, so strict clients refused to connect.
• Updated the existing test_greeting_capabilities-t baseline regression check to include the new flag.
• Added new test_plugin_auth_lenenc_client_data-t TAP test that exercises the full lenenc auth path end-to-end (server advertises flag, client negotiates it, query succeeds).

Context

Closes #4760

Testing

• Library and test binaries compile cleanly.
• lint_groups_json.py passes.
• check_groups.py --source shows no regressions (pre-existing mysqlx_admin_alias_resolution_unit-t missing from groups.json is unrelated).

Summary by CodeRabbit

• New Features

  • Server now advertises extended plugin authentication capabilities during the initial MySQL handshake, improving interoperability with modern MySQL clients.

• Tests

  • Added integration test validating server capability advertisement and client-side negotiation for enhanced authentication features during connection handshake, including multiple configuration scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 7b598f77-438c-43a5-bb1a-a78b930d019d

📥 Commits

Reviewing files that changed from the base of the PR and between 05d0268 and 325b3e4.

📒 Files selected for processing (4)

• lib/MySQL_Protocol.cpp
• test/tap/groups/groups.json
• test/tap/tests/test_greeting_capabilities-t.cpp
• test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp

📜 Recent review details

🧰 Additional context used

📓 Path-based instructions (3)

**/*.{cpp,h,hpp}

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.{cpp,h,hpp}: Class names must use PascalCase with protocol prefixes (MySQL_, PgSQL_, ProxySQL_)
Member variables must use snake_case naming convention
Constants and macros must use UPPER_SNAKE_CASE naming convention
Use conditional compilation via #ifdef PROXYSQL31, #ifdef PROXYSQL40, #ifdef PROXYSQLFFTO, #ifdef PROXYSQLTSDB, #ifdef PROXYSQLCLICKHOUSE for feature tier gating in core code

Files:

• test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp
• lib/MySQL_Protocol.cpp
• test/tap/tests/test_greeting_capabilities-t.cpp

test/tap/tests/{test_*,-t}.cpp

📄 CodeRabbit inference engine (CLAUDE.md)

Test files must follow the naming pattern test_*.cpp or *-t.cpp in test/tap/tests/

Files:

• test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp
• test/tap/tests/test_greeting_capabilities-t.cpp

test/tap/tests/*-t.cpp

📄 CodeRabbit inference engine (CLAUDE.md)

Test binaries are built via pattern rule in test/tap/tests/Makefile: make <testname>-t compiles <testname>-t.cpp into <testname>-t without requiring explicit Makefile targets

Files:

• test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp
• test/tap/tests/test_greeting_capabilities-t.cpp

🧠 Learnings (1)

📚 Learning: 2026-01-20T09:34:19.124Z

Learnt from: yuji-hatakeyama
Repo: sysown/proxysql PR: 5307
File: test/tap/tests/reg_test_5306-show_warnings_with_comment-t.cpp:39-48
Timestamp: 2026-01-20T09:34:19.124Z
Learning: In ProxySQL's TAP test suite, resource leaks (e.g., not calling mysql_close() on early return paths) are commonly tolerated because test processes are short-lived and OS frees resources on exit. This pattern applies to all C++ test files under test/tap/tests. When reviewing, recognize this as a project-wide test convention and focus on test correctness and isolation rather than insisting on fixing such leaks in these test files.

Applied to files:

• test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp
• test/tap/tests/test_greeting_capabilities-t.cpp

🔇 Additional comments (4)

lib/MySQL_Protocol.cpp (1)

1131-1137: LGTM — correct placement and no protocol behavior change.

CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA = 0x00200000 is bit 21, so it belongs exclusively in the upper word of the greeting. The lower-word memcpy at line 1108 copies only 2 bytes from server_capabilities (bits 0–15) and won't inadvertently broadcast this bit. The lenenc parsing path in PPHR_2() (line 1714) already existed and is keyed on vars1.capabilities (the client's flags), so there is no regression from server_capabilities not carrying this bit. The fix is purely advertisement-only, exactly as intended.

test/tap/tests/test_greeting_capabilities-t.cpp (1)

177-185: LGTM — baseline correctly updated to match the new greeting advertisement.

test/tap/groups/groups.json (1)

380-380: LGTM — properly inserted in alphabetical order with the correct -g3 target group set.

test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp (1)

59-131: LGTM — end-to-end test is well-structured.

Both the server-advertisement check (server_has_lenenc) and the client-negotiation check (client_has_lenenc) are intentional per the PR description, and the separate diag() lines (88–91) make it clear which side failed if the test ever breaks. Cleanup is consistent across all code paths.

---

📝 Walkthrough

Walkthrough

This PR adds support for advertising the CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA capability in the MySQL protocol handshake greeting. A new integration test validates the capability is properly advertised and negotiated, while baseline test expectations are updated accordingly.

Changes

Plugin Auth Capability Advertisement

Layer / File(s)	Summary
Core Implementation lib/MySQL_Protocol.cpp	extended_capabilities bitmask in generate_pkt_initial_handshake now includes CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA alongside existing CLIENT_PLUGIN_AUTH, CLIENT_SESSION_TRACKING, and CLIENT_REMEMBER_OPTIONS bits.
Test Infrastructure test/tap/groups/groups.json	New test group entry "test_plugin_auth_lenenc_client_data-t" is registered to execute against legacy-g3 and MySQL variant targets (matching other test suite patterns).
Test Baseline Update test/tap/tests/test_greeting_capabilities-t.cpp	BASELINE_PRESENT_CAPS is updated to require CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA in server greeting, so missing capability bits are reported as expected failures.
Integration Test test/tap/tests/test_plugin_auth_lenenc_client_data-t.cpp	New TAP test validates capability advertisement by toggling mysql-enable_client_deprecate_eof, connecting via MariaDB/MySQL C API, verifying both server_capabilities and client_flag bits are set, and executing a connectivity test query.

Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly Related Issues

• Cannot connect to ProxySQL with boost mysql. #4760: Boost MySQL connector fails to connect to ProxySQL due to missing CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA capability flag in server handshake—this PR directly addresses that by advertising the required capability.

Possibly Related PRs

• Add MySQL protocol ZSTD compression support #5458: Also modifies MySQL handshake capability advertisement in lib/MySQL_Protocol.cpp, adjusting which CLIENT_* bits are set during initial handshake.
• Fix regression: restore upper-word capabilities dropped from greeting #5623: Updates generate_pkt_initial_handshake to change extended capability bitmask and includes corresponding test modifications for capability-related validation.

Poem

🐰 A flag hops forth with quiet grace,
CLIENT_PLUGIN_AUTH_LENENC takes its place,
In handshakes warm and headers bright,
The Boost connector finds its light! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: advertising CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA in the server greeting, which aligns directly with all the file changes.
Linked Issues check	✅ Passed	The PR fully addresses issue #4760 by advertising CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA in server greeting, adding comprehensive tests, and validating the capability negotiation end-to-end.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to implementing the fix for issue #4760: capability advertisement in handshake, test coverage, and test configuration; no unrelated modifications.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/4760-lenenc-auth-v3.0

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Review rate limit: 7/8 reviews remaining, refill in 7 minutes and 30 seconds.}

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[gemini-code-assist]

Code Review

This pull request adds the CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA capability to the MySQL server greeting in lib/MySQL_Protocol.cpp, allowing ProxySQL to support length-encoded authentication data. The changes also include a new test suite and updates to existing test configurations. Feedback suggests adding a fallback definition for the new capability flag to ensure compatibility with older development headers and recommends adding a null check for query results in the test code to prevent potential crashes.

[gemini-code-assist]

To ensure compilation succeeds on systems with older MySQL/MariaDB development headers, consider adding a fallback definition for CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA at the top of this file, similar to what was done in lib/MySQL_Protocol.cpp and the new test file.

[gemini-code-assist]

It is safer to check if row[0] is not NULL before passing it to strcmp, even if the query is expected to return a value. This prevents potential crashes if the result set is unexpected.

	if (!row || row[0] == NULL || strcmp(row[0], "1") != 0) {

[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

See analysis details on SonarQube Cloud