fix: drain caching_sha2_password AuthMoreData+OK in switchAuth(), gua…

[JacobStephens2]

What this fixes

The binlog client can't complete its handshake against MySQL 8.4 when the account uses caching_sha2_password (the 8.x default). switchAuth() reads the auth-switch response but never drains the extra packets caching_sha2_password sends, so every later getResponse() is two packets ahead and the first read reaches Event::consume() as a malformed event, crashing with a TypeError on readInt32() / readUInt16() (PHP 8 strict types).

The handshake

On the fast-auth path - the account's password is already in the server's auth cache - the server answers the auth switch with an AuthMoreData packet (status byte 0x01) carrying fast_auth_success (0x03), then the OK packet. The old code drained neither, leaving the stream offset by two packets. Protocol reference: https://dev.mysql.com/doc/dev/mysql-server/latest/page_caching_sha2_authentication_exchanges.html

The change (2 files, +50/-1)

1. BinLogSocketConnect::switchAuth(): after sending the scrambled password, when the switched plugin is caching_sha2_password, drain the AuthMoreData packet and then the trailing OK. If the server instead asks for perform_full_authentication (0x04), throw a clear BinLogException rather than hang - full auth needs the password over TLS or a unix socket, which this client doesn't implement, so fast-auth requires the user already be cached server-side.
2. Event::consume(): skip any response shorter than the 20-byte event-header minimum (1 status byte + 19-byte header) instead of parsing a leftover OK packet as an event. Defense in depth for a misaligned stream.

Tests

1. tests/Unit/Event/EventConsumeShortPacketTest.php: feeds consume() three short responses (empty, a 7-byte OK packet, 19 bytes) and asserts it skips them and dispatches nothing. Without the guard all three error with a TypeError on readUInt16(). No MySQL needed.
2. tests/Integration/CachingSha2PasswordAuthTest.php: asserts the binlog handshake completes over caching_sha2_password on MySQL 8+ and reads a QueryDTO to confirm the stream is aligned. Skips below 8.0; exercised by the 8.0 and 8.4 CI legs.

Reproducing

Point the binlog client at MySQL 8.4 with a caching_sha2_password user whose password is already cached server-side (any prior successful login warms it). Before this change the handshake throws a TypeError; after it, the connection completes and events read normally. I've been running this in production against MySQL 8.4.

[JacobStephens2]

Hi @krowinski,

Following up on this one. I've added test coverage and filled in the description:

• tests/Unit/Event/EventConsumeShortPacketTest.php feeds consume() three short responses (empty, a 7-byte OK packet, 19 bytes) and asserts it skips them and dispatches nothing. Without the < 20-byte guard all three error with a TypeError on readUInt16(). Green locally, no MySQL needed.
• tests/Integration/CachingSha2PasswordAuthTest.php asserts the binlog handshake completes over caching_sha2_password on MySQL 8+, then reads a QueryDTO to confirm the stream is aligned. It runs on the 8.0 and 8.4 CI legs.

The description now walks the handshake, the two-packet drain, and how to reproduce. 2 files +50/-1 in the fix itself. Whenever you have a moment to review, I'd appreciate it.

Thanks, Jacob