*: support switch auth when change user

[xhebox]

Signed-off-by: xhe [email protected]

What problem does this PR solve?

Issue Number: close #38829

Problem Summary: Support switch auth request when changing user. This allows mismatch between client/server auth methods. And it gives a chance for proxy to change the correct salt.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

tiup --db.binpath ./tidb-server
./bin/tiproxy
mvn "-Dcom.mysql.jdbc.testsuite.url=jdbc:mysql://127.0.0.1:6000/test?user=root&password=&useSSL=false&useServerPrepStmts=true" '-Dtest=ConnectionRegressionTest#testBug19354014' test

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

support switch auth request for change user command

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CbcWestwolf
• dveeden

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[djshow832]

Can you add a UT in case someone breaks it in the future?

[dveeden]

/run-unit-test
/run-mysql-test

[dveeden]

Looks to match with https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_connection_phase.html#sect_protocol_connection_phase_com_change_user_auth

[djshow832]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 3fe723c

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! New failing [2] after this pr merged.
These new failed integration tests seem to be caused by the current PR, please try to fix these new failed integration tests, thanks!

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/common-test	🟥 failed 2, success 9, total 11	10 min	New failing
idc-jenkins-ci-tidb/integration-ddl-test	🟥 failed 1, success 5, total 6	4 min 41 sec	New failing
idc-jenkins-ci/integration-cdc-test	🟢 all 38 tests passed	22 min	Existing passed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	13 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 55 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 36 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 24 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 15 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 55 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed