Document `faradayio` Expected Serial Packet Formats

[kb1lqc]

This ticket with help @kb1lqd by providing a wiki-based documentation of the expected SLIP format packets being sent over the serial port from the TUN interface

Goals

• [x] Show normal ASCII and ASCII with escaped characters in a packet
• [x] Document an example IP packet

Wiki page with this documentation is: https://github.com/FaradayRF/faradayio/wiki/SLIP-Encoded-IP-Packets

[kb1lqc]

IP Packet sending "Hello, world!"

srcPacket = (IP(dst=destHost,
                    src=TUNMonitor._TUN._tun.addr) /
                 UDP(sport=9998,
                     dport=destPort) / "Hello, world!").__bytes__()

This results in a scapy.show() IP parse of:

tests/test_tun.py::test_tunSend ###[ IP ]###
  version   = 4
  ihl       = 5
  tos       = 0x0
  len       = 41
  id        = 1
  flags     = 
  frag      = 0
  ttl       = 64
  proto     = udp
  chksum    = 0x66c1
  src       = 10.0.0.1
  dst       = 10.0.0.2
  \options   \
###[ UDP ]###
     sport     = 9998
     dport     = 9999
     len       = 21
     chksum    = 0x5c58
###[ Raw ]###
        load      = 'Hello, world!'

Printing the hexlify value of this packet results in:

4500002900010000401166c10a0000010a000002270e270f00155c5848656c6c6f2c20776f726c6421

Printing the raw hex of this packet also results in:

E\x00\x00)\x00\x01\x00\x00@\x11f\xc1\n\x00\x00\x01\n\x00\x00\x02'\x0e'\x0f\x00\x15\\XHello, world!

This is NOT yet SLIP encoded.

[kb1lqc]

A SLIP encoded version of the IP packet sending "Hello, world!" looks like:

\xc0E\x00\x00)\x00\x01\x00\x00@\x11f\xc1\n\x00\x00\x01\n\x00\x00\x02'\x0e'\x0f\x00\x15\\XHello, world!\xc0

[kb1lqc]

Here's an example of an IP packet which contains a string with a SLIP escape character. SLIP is forced to escape the escape character within the string.

This string has \xdb which should escape in SLIP

When printed with scapy.show() we can see the following output:

###[ IP ]###
  version   = 4
  ihl       = 5
  tos       = 0x0
  len       = 73
  id        = 1
  flags     = 
  frag      = 0
  ttl       = 64
  proto     = udp
  chksum    = 0x66a1
  src       = 10.0.0.1
  dst       = 10.0.0.2
  \options   \
###[ UDP ]###
     sport     = 9998
     dport     = 9999
     len       = 53
     chksum    = 0xaade
###[ Raw ]###
        load      = b'This string has \xdb which should escape in SLIP'

Here is the hexlify format

4500004900010000401166a10a0000010a000002270e270f0035aade5468697320737472696e672068617320db2077686963682073686f756c642065736361706520696e20534c4950

The raw hex being sent is:

E\x00\x00I\x00\x01\x00\x00@\x11f\xa1\n\x00\x00\x01\n\x00\x00\x02'\x0e'\x0f\x005\xaa\xdeThis string has \xdb which should escape in SLIP

and finally the raw hex of the SLIP encoded IP packet

\xc0E\x00\x00I\x00\x01\x00\x00@\x11f\xa1\n\x00\x00\x01\n\x00\x00\x02'\x0e'\x0f\x005\xaa\xdeThis string has \xdb\xdd which should escape in SLIP\xc0

[kb1lqc]

Closing this ticket as basic documentation of the expected serial port SLIP protocol IP packets has been completed. See the wiki page I created to satisfy this issue ticket.

https://github.com/FaradayRF/faradayio/wiki/SLIP-Encoded-IP-Packets