takprotobuf

Python library to encode and decode Cursor-on-Target (CoT) messages using Protocol Buffers.

Usage

The library currently contains two basic functions. parseProto() decodes a protobuf and returns the contents of the message. xmlToProto() encodes XML to TAK protobuf. I'll be adding an additional functionton to encode a protobuf directly from a Python oject or class.

xmlToProto()

Given a string which contains either a CoT message in XML or the path to an XML file containing a CoT message, the function xmlToProto() will return a byte array containing the binary protobuf.

For example, if the string xml contained:

<?xml version='1.0' encoding='UTF-8' standalone='yes'?>
<event version='2.0' uid='aa0b0312-b5cd-4c2c-bbbc-9c4c70216261' type='a-f-G-E-V-C' time='2020-02-08T18:10:44.000Z' start='2020-02-08T18:10:44.000Z' stale='2020-02-08T18:11:11.000Z' how='h-e'><point lat='43.97957317' lon='-66.07737696' hae='26.767999' ce='9999999.0' le='9999999.0' /><detail><uid Droid='Eliopoli HQ'/><contact callsign='Eliopoli HQ' endpoint='192.168.1.10:4242:tcp'/><__group name='Yellow' role='HQ'/><status battery='100'/><takv platform='WinTAK-CIV' device='LENOVO 20QV0007US' os='Microsoft Windows 10 Home' version='1.10.0.137'/><track speed='0.00000000' course='0.00000000'/></detail></event>

You would call the xmlToProto() function with:

from takprotobuf import xmlToProto
xmlToProto(xml)

The function would return:

bytearray(b'\xbf\x01\xbf\x12\xff\x01\n\x0ba-f-G-E-V-C*$aa0b0312-b5cd-4c2c-bbbc-9c4c702162610\xa0\xa2\xc7\xb8\x82.8\xa0\xa2\xc7\xb8\x82.@\x98\xf5\xc8\xb8\x82.J\x03h-eQ3\x98T\xa7b\xfdE@Y}*~\xbe\xf3\x84P\xc0aW\\\x1c\x95\x9b\xc4:@i\x00\x00\x00\xe0\xcf\x12cAq\x00\x00\x00\xe0\xcf\x12cAz\x82\x01\x12$\n\x15192.168.1.10:4242:tcp\x12\x0bEliopoli HQ\x1a\x0c\n\x06Yellow\x12\x02HQ*\x02\x08d2F\n\x11LENOVO 20QV0007US\x12\nWinTAK-CIV\x1a\x19Microsoft Windows 10 Home"\n1.10.0.137:\x00')

parseProto()

Given a bytearray containing a TAK protobuf, parseProto() will return an instance of the protobuf class. You can then access the contents as an object.

If binary is a bytearray containing a TAK protobuf:

bytearray(b'\xbf\x01\xbf\x12\xff\x01\n\x0ba-f-G-E-V-C*$aa0b0312-b5cd-4c2c-bbbc-9c4c702162610\xa0\xa2\xc7\xb8\x82.8\xa0\xa2\xc7\xb8\x82.@\x98\xf5\xc8\xb8\x82.J\x03h-eQ3\x98T\xa7b\xfdE@Y}*~\xbe\xf3\x84P\xc0aW\\\x1c\x95\x9b\xc4:@i\x00\x00\x00\xe0\xcf\x12cAq\x00\x00\x00\xe0\xcf\x12cAz\x82\x01\x12$\n\x15192.168.1.10:4242:tcp\x12\x0bEliopoli HQ\x1a\x0c\n\x06Yellow\x12\x02HQ*\x02\x08d2F\n\x11LENOVO 20QV0007US\x12\nWinTAK-CIV\x1a\x19Microsoft Windows 10 Home"\n1.10.0.137:\x00')

You would call the parseProto() function with

from takprotobuf import parseProto
decoded = parseProto(binary)

The function reurns an object which contains the data from the protobuf. Individual attributes can be accessed by calling them directly, and a built-in method will return pretty-printed data if you call higher level elements.

For example:

from takprotobuf import parseProto
decoded = parseProto(binary)
print(decoded)

returns a human-readable representation of the object. By default, the attributes are laid out in the same hierarchy as TAK protocol, which is different from CoT XML. I'll be adding the option to return an object that is more similar to the way CoT XML is organized.

cotEvent {
  type: "a-f-G-E-V-C"
  uid: "aa0b0312-b5cd-4c2c-bbbc-9c4c70216261"
  sendTime: 1581203444000
  startTime: 1581203444000
  staleTime: 1581203471000
  how: "h-e"
  lat: 43.97957317
  lon: -66.07737696
  hae: 26.767999
  ce: 9999999.0
  le: 9999999.0
  detail {
    contact {
      endpoint: "192.168.1.10:4242:tcp"
      callsign: "Eliopoli HQ"
    }
    group {
      name: "Yellow"
      role: "HQ"
    }
    status {
      battery: 100
    }
    takv {
      device: "LENOVO 20QV0007US"
      platform: "WinTAK-CIV"
      os: "Microsoft Windows 10 Home"
      version: "1.10.0.137"
    }
    track {
    }
  }
}

TAK Protobuf Header Bytes

When TAK clients send UDP packets containing protobufs, there is a three byte header consisting of 0xbf 0x01 0xbf. The xmlToProto() function adds the header bytes for you, and the parseProto() functions expects them to be included in its input. This may change in the future, as I learn more about the TAK ecosystem.

To Do

• Clean up processing for the xmlDetail element
• Encode protobuf directly from Python object or class
• Exception handling

Credits

I couldn't have created this without all of the examples of CoT XML provided by the developers of FreeTAKServer at https://github.com/FreeTAKTeam/FreeTakServer/tree/master/docs/Example%20metrics/cot

Built using Protoc, the protobuf compiler https://github.com/protocolbuffers/protobuf

and the .proto files from the ATAK repository https://github.com/deptofdefense/AndroidTacticalAssaultKit-CIV/tree/master/commoncommo/core/impl/protobuf