Packet showing UDP data rather than OpenVPN data

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Joined: Thu Oct 03, 2019 12:09 pm

Packet showing UDP data rather than OpenVPN data

Post by EnderG » Thu Oct 03, 2019 12:29 pm

Hello everyone,

I've been working on this tunnel for almost 3 days now. Here's the rundown:

My client sends the initial P_CONTROL_HARD_RESET_CLIENT_V2 packet.
Normal procedure would be for the server to respond with a P_CONTROL_HARD_RESET_SERVER_V2.
Instead I get nothing. Did a bunch of research and changed settings, changed them back, tested again, etc.
Checked, double checked, triple checked the configs.
Ran a packet capture on the Firewall (pfSense) and found that the HARD_RESET was making it to the correct port, BUT instead of wireshark showing OpenVPN protocol inside the datagram it just shows 42 bytes of data. Did an offset by offset comparison to sent and received and it appears that the HMAC value somehow changed in transit.

The opcode/key_id of 0x38 is in the proper offset but after that the data is different.

Any ideas?

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