Modification of TCP packets about mitm_relay

[jrmdev]

Hi, Thank you for your comments.

In a MySQL packet. the first 3 bytes of the TCP payload represent the payload length. You will need to update this. Below is a screenshot of a MySQL query packet capture.

You can see that the Packet length field is specified in the first 3 bytes. The following byte ('\x00') is the packet number, and the next one ('\x03') indicates that it's a request. You can reuse those 2 bytes from the original request. Therefore you can rebuild the packet like this:

Length (3 bytes) + \x00 + \x03 + Payload

Here is some example code:

>>> import struct
>>> payload = 'Select "NEW_RESULT" from DUAL--'
>>> new_length = struct.pack('<Q', len(payload))[:3]
>>> modified_request = new_length + client_request[3:5] + payload
>>> modified_request
'\x1f\x00\x00\x00\x03Select "NEW_RESULT" from DUAL--'
>>> 

Hope this helps.

[alex4628]

Thank you for your informative reply! It all makes sense now.