[rusher]

Description

Follow-up to #1696 and #1825: adds the MariaDB parsec authentication plugin (MariaDB 11.6+).

This PR implement MariaDB parsec authentication (protocol documentation)

The client requests the extended salt with an empty packet, derives an Ed25519 key from the password with PBKDF2-HMAC-SHA512 (1024 << factor rounds, using the standard library's crypto/pbkdf2 and crypto/ed25519), and signs the server nonce followed by a random client nonce. MariaDB server fix the current iteration to 0 for now (so 1024 permutations) but implementation is design so it can be change in the futur with a cap at 10 (1,048,576 rounds) to bound the hashing cost.

Tests cover the full auth switch exchange on a mock connection with signature verification, malformed packets and the iteration limit, plus an integration test that creates a parsec user on the server. The integration test runs on the MariaDB 12.3 and 11.8 CI builds, which ship auth_parsec.so, and skips elsewhere.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

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• driver_test.go

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Walkthrough

The change adds MariaDB PARSEC authentication, preserves trailing NUL bytes in auth-switch challenges, and validates seed lengths in the caching SHA-2 and SHA-256 authentication paths.

Changes

Authentication flow

Layer / File(s)	Summary
Preserve auth-switch challenge bytes auth.go, auth_plugin.go, auth_plugin_test.go, auth_security_test.go, auth_test.go	Auth-switch parsing preserves a trailing NUL byte. The plugin contract and auth-switch tests reflect that the challenge is passed unchanged.
Validate scramble seed lengths auth_caching_sha2.go, auth_sha256.go	Both authentication paths reject seeds shorter than 20 bytes and use only the first 20 bytes when scrambling.
Implement and verify PARSEC authentication auth_parsec.go, auth_parsec_test.go, driver_test.go, CHANGELOG.md, README.md	The plugin requests extended salt, derives an Ed25519 key, and returns a client nonce and signature. Tests cover the exchange, malformed inputs, the maximum iteration factor, and MariaDB server authentication. The changelog and README list PARSEC.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant MariaDB
  participant Driver
  participant ParsecPlugin
  MariaDB->>Driver: Auth-switch request with server nonce
  Driver->>ParsecPlugin: InitAuth with unchanged nonce
  ParsecPlugin-->>Driver: Empty salt-request packet
  Driver->>MariaDB: Empty packet
  MariaDB-->>Driver: Extended salt packet
  Driver->>ParsecPlugin: ContinuationAuth with salt
  ParsecPlugin-->>Driver: Client nonce and signature
  Driver->>MariaDB: PARSEC response

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Suggested reviewers: methane

Merge Risk: ⚪ Minimal · up to 7ed37

The PARSEC authentication integration test now creates uniquely named accounts for the client's host and quotes the database name, so it should run safely against remote or shared servers. No merge-blocking risk remains.

Pre-merge checks · 4 · 1

Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 27.27% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks (4 passed)

Check name	Status	Explanation
Description check		The description clearly explains the addition of MariaDB parsec authentication, its protocol flow, supported versions, tests, and integration coverage.
Title check		The title clearly identifies the main change: adding MariaDB parsec authentication support.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[coveralls]

coverage: 85.755% (-0.06%) from 85.814% — rusher:parsec-auth into go-sql-driver:master

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Actionable comments posted: 3

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @driver_test.go:
- Line 3696: Update the account setup in the test that iterates over
"localhost", "127.0.0.1", and "::1" so it also matches clients connecting to a
remote MySQL server configured through MYSQL_TEST_ADDR. Add an account scoped to
the client host or use a suitably scoped wildcard, while preserving the existing
loopback accounts.
- Around line 3697-3698: Generate a unique account name for each test run
instead of hardcoding parsectest, and use that same name in the CREATE USER
statement, deferred DROP USER, and connection DSN to prevent test runs from
replacing or removing each other’s accounts.
- Line 3702: Update the GRANT statement passed to db.Exec to quote the
configured dbname as a MySQL identifier, escaping any backticks in its value
before adding the surrounding backticks; preserve the existing account handling.

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