TCP Proxy: Fix TLS passthrough for fragmented ClientHello.

[maxl99]

What this PR does / why we need it:

We need to read the entire length of the ClientHello packet in order to get the SNI field for proper tls passthrough.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• CVE Report (Scanner found CVE and adding report)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

fixes #11491
fixes #11424

How Has This Been Tested?

Tested with tldr_fail_test.py (modified to use tls1.2)
Without the patch:

With the patch, passthrough also works for a fragmented ClientHello.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added unit and/or e2e tests to cover my changes.
• All new and existing tests passed.

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[kvaps]

LGTM, tested this, works perfectly

[tao12345666333]

/ok-to-test

I will run the test suite first.

[Gacko]

/kind bug
/priority backlog
/hold

If this is a bug, could you please also add some tests to prevent future regression?

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[APPROVALNOTIFIER] This PR is NOT APPROVED

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[maxl99]

/kind bug /priority backlog /hold

If this is a bug, could you please also add some tests to prevent future regression?

I tried to implement an e2e test that sends a ClientHello with 2 packets (similar to the behaviour we see in the packet capture).
Sadly it seems to be a bit tricky because the test is also successful without the patch :(
I'm using net.Dial and Write. I also tried casting it to an net.TCPConn and setting things like SetWriteBuffer(0) and SetNoDelay(true).

[longwuyuan]

ssl-passthrough is targeted for deprecation.

I understand this is disruptive. But there is demand for real-client-ip and now this fragmented client-helo. Its also very clear that 2 PRs are in queue for addressing this.

But please consider that the requirement now is 2 folds. On one hand a developer of the project needs to evaluate not just the PRs here but also the impact of those changes on the design, security & stability of the controller.. Secondly the continued support/maintenance to sustain the TLS-Passthrough feature in its current go-proxy avatar, requires resources.

The project hit CVEs and and other sustaining related problems and faced acute shortage of resources for a extended length of time. So to avoid future impact to the security/stability of the controller, a decision was made to focus on the core functionality of the project. We are even deprecating several functioning useful popular features. Implementing the Gateway-API is the other focus besides shipping a secure-by-default controller.

Hence wait for other comments, but I would say not to expect much traction on this as the TLS-Passthrough feature itself may be deprecated sooner than later. I understand its the least desired scene but its the reality of changing times.

Users do obviously have the option to fork the project and implement desired changes there. regards.