Module: PWN::SDR::Decoder::POCSAG

Defined in:
lib/pwn/sdr/decoder/pocsag.rb

Overview

POCSAG (CCIR Radiopaging Code No. 1) decoder for pager networks.

Pipeline (identical shape to PWN::SDR::Decoder::Flex):

GQRX 48 kHz s16le UDP audio → sox → 22 050 Hz → multimon-ng.

multimon-ng emits lines of the form:

POCSAG1200: Address:  123456  Function: 3  Alpha:   FIRE ALARM ZONE 4
POCSAG512:  Address:  000042  Function: 0  Numeric: 5551234
POCSAG2400: Address:  987654  Function: 1  Skyper:  ...
POCSAG1200: Address:  123456  Function: 2  Alpha:   <partial><EOT>

Each line is parsed into { protocol, baud, address/capcode, function, function_desc, type, type_desc, message } and JSON-logged.

Constant Summary collapse

FUNCTION_DESC = 
{
  0 => 'Numeric (Tone/A)',
  1 => 'Tone only (B)',
  2 => 'Tone only (C)',
  3 => 'Alphanumeric (D)'
}.freeze
TYPE_DESC = 
{
  'Alpha' => 'Alphanumeric text (7-bit ASCII)',
  'Numeric' => 'Numeric-only (BCD)',
  'Skyper' => 'Skyper network encoded',
  'Tone' => 'Tone-only alert (no message body)'
}.freeze

Class Method Summary collapse

Class Method Details

.authors ⇒ Object

Author(s)

0day Inc. support@0dayinc.com



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# File 'lib/pwn/sdr/decoder/pocsag.rb', line 98

public_class_method def self.authors
  "AUTHOR(S):\n  0day Inc. <support@0dayinc.com>\n"
end

.decode(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::POCSAG.decode( freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq' )



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# File 'lib/pwn/sdr/decoder/pocsag.rb', line 39

public_class_method def self.decode(opts = {})
  freq_obj = opts[:freq_obj]

  # -e  hide empty messages
  # -u  heuristically prune unlikely decodes (cuts BCH false-positives)
  # -p  emit partially received messages (still useful intel)
  # -f alpha  force Alpha framing when function bits are ambiguous —
  #           mirrors the behaviour operators expect from Flex ALN.
  decode_cmd = 'multimon-ng -q -t raw -e -u -p -f alpha ' \
               '-a POCSAG512 -a POCSAG1200 -a POCSAG2400 -'

  PWN::SDR::Decoder::Base.run_pipeline(
    freq_obj: freq_obj,
    protocol: 'POCSAG',
    required_bins: %w[sox multimon-ng],
    decode_cmd: decode_cmd,
    line_match: /^POCSAG(?:512|1200|2400):/,
    parser: proc { |line| parse_line(line: line) }
  )
end

.help ⇒ Object

Display Usage for this Module



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# File 'lib/pwn/sdr/decoder/pocsag.rb', line 104

public_class_method def self.help
  puts "USAGE:
    #{self}.decode(
      freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq'
    )

    #{self}.parse_line(line: 'POCSAG1200: Address: 123456 Function: 3 Alpha: HELLO')

    #{self}.authors
  "
end

.parse_line(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::POCSAG.parse_line(line: 'POCSAG1200: Address: ...')



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# File 'lib/pwn/sdr/decoder/pocsag.rb', line 63

public_class_method def self.parse_line(opts = {})
  line = opts[:line].to_s
  out  = { protocol: 'POCSAG', raw_inspected: line.inspect }

  if (m = line.match(/^POCSAG(\d+):/))
    out[:baud] = m[1].to_i
  end
  if (m = line.match(/Address:\s*(\d+)/i))
    out[:address] = m[1].to_i
    out[:capcode] = m[1].rjust(7, '0')
  end
  if (m = line.match(/Function:\s*(\d+)/i))
    fn = m[1].to_i
    out[:function]      = fn
    out[:function_desc] = FUNCTION_DESC[fn] || 'Unknown'
  end
  if (m = line.match(/\b(Alpha|Numeric|Skyper|Tone):\s*(.*)$/i))
    type = m[1].capitalize
    out[:type]         = type
    out[:type_desc]    = TYPE_DESC[type] || 'Unknown'
    out[:type_payload] = m[2].to_s.gsub(/<[A-Z]{2,4}>/, '').strip
    out[:message]      = out[:type_payload]
  end

  bits = []
  bits << "POCSAG#{out[:baud]}" if out[:baud]
  bits << "RIC=#{out[:capcode]}" if out[:capcode]
  bits << "F#{out[:function]}(#{out[:function_desc]})" if out[:function]
  bits << "#{out[:type]}: #{out[:message]}" if out[:type]
  out[:summary] = bits.join(' ')
  out
end