feat: support service banner for TCP

[milinddethe15]

fixes #53

TCP handler can handle other target ports without need of seperate port handlers.

[glaslos]

Please add a README.md into the responses folder with a not where the responses are sourced from.

[milinddethe15]

Just to confirm:

1. Banner should be send intially, when connected
2. then read conn
3. and if read conn payload > max_tcp_payload: send random data and break?

[glaslos]

1 and 2 is correct. For 3, just read once, no need to read until max payload, that is just protection.

[milinddethe15]

what tool should I use to hit the target?
I tried telnet 127.0.0.1 4444 but banner wasn't received when connected.

[glaslos]

try netcat: nc

[milinddethe15]

I tried to test it and the banner isn't sent as soon as connected, but until attacker's payload. Is this how it should work?

[glaslos]

You need to send the banner before we peek the connection here

[milinddethe15]

Tested locally with TCP port 4444. works good.

[glaslos]

Have a look at the failing test.

[milinddethe15]

Tests are failing....
Looking into it.

[milinddethe15]

Test is getting timeout error.
I guess it is expecting user data when peeking the conn.
Before this PR changes, wasn't test peeking the conn?? Its confusing..

[glaslos]

I pushed a change to the main branch introducing the timeout on the buffered connection we use for peeking.
After peeking the connection, you have to use the bufConn, not the original conn. Also make sure you set an actual read deadline instead of SetReadDeadline(time.Time{})