MySQL Bugs: #115572: CancellationToken causes unhandled exception crash when in StartSSLAsync

Bug #115572	CancellationToken causes unhandled exception crash when in StartSSLAsync
Submitted:	12 Jul 2024 9:51	Modified:	25 Aug 10:01
Reporter:	Brent Alleweireldt	Email Updates:
Status:	Open	Impact on me:	None
Category:	Connector / NET	Severity:	S2 (Serious)
Version:	8.0.33	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	SSL, timeout, Unhandled exception

Description:
Discovered in 8.0.33 but still present in the latest version.

MySQL version 8.4
Connector version: 8.0.33-9.0.0
.Net framework: 4.8 (presumably also present in .Net 8.0)

The driver can throw an unhandled exception if the ConnectionTimeout expires during the AuthenticateAsClient part of the SSL initialization. This exception cannot be caught by the client and thus causes an application crash. (see detailed description below)

Expectations: Connector does not throw exceptions that cannot be handled.

Detailed description:
In Driver.cs->CreateAsync() a CancellationTokenSource (named connTimeoutSource) gets created that will be canceled after the connectionTimout has expired. The token from this connTimeoutSource is then linked to a general CancellationToken that is passed around during the connection-logic.

This token eventually ends up in Ssl.cs->StartSSLAsync(), right before starting the AuthenticateAsClientAsync() the Cancellationtoken gets used to register a callback that throws an IOException.

However if this token is cancelled by the timeout from the connTimeoutToken, This exception ends up on a timerthread and is not caught, leading to a crash of the application.

How to repeat:
Requires external tools to simulate properly.

1. Configure clumsy with the following settings
-Filter "tcp.DstPort == 3384 and tcp.PayloadLength >= 147" (basically TLS client hello)
- Enable drop on inbound/outbound with 100% chance
2. Connect a MySQL database with SSLMode=Preferred
3. Observe the unhandled exception.

Suggested fix:
Do not throw exceptions in the CancellationToken.Register function. Use other methods to properly detect if the timeout passed and throw the exception on the thread that called the Open().

Clumsy settings

Attachment: clumsy settings.png (image/png, text), 26.90 KiB.

Duplicate-ish (same flow, just different exceptions of https://bugs.mysql.com/bug.php?id=110789. Apologies.

Thank you for the feedback.

This bug is reproducible with version 9.4.0

The crash can be reproduced using the reproduction steps described in this bug report (using the clumsy tool)

Could you please verify if this was actually resolved in version 9.4.0?

Please let me know if I need to create a new bug report

Reopening this bug.

https://bugs.mysql.com/bug.php?id=118861 is marked as duplicate of this one

This bug is not a duplicate of https://bugs.mysql.com/bug.php?id=110789