Module: PWN::SDR::Decoder::GSM

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

Overview

GSM (2G) true-air BCCH/CCCH activity decoder.

Defined Under Namespace

Classes: DemodIQ

Constant Summary collapse

TSHARK_FIELDS = 
%w[
  frame.time gsmtap.arfcn gsmtap.chan_type gsm_a.imsi gsm_a.tmsi
  e212.mcc e212.mnc gsm_a.lac gsm_a.bssmap.cell_ci gsm_a.dtap.msg_rr_type
].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/gsm.rb', line 125

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



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# File 'lib/pwn/sdr/decoder/gsm.rb', line 72

public_class_method def self.decode(opts = {})
  freq_obj = opts[:freq_obj]
  rate = (opts[:sample_rate] || freq_obj[:iq_rate] || 1_000_000).to_i
  proto = 'GSM'
  extra = {}
  describe = proc { |b| { modulation: 'GMSK', symbol_rate: 270_833, tdma_frames: (b[:duration_ms] / 4.615).round, classification: (b[:duration_ms] / 4.615) > 10 ? 'BCCH/CCCH-continuous' : 'RACH/paging-burst' } }
  demod = DemodIQ.new(
    rate: rate, protocol: proto, modulation: 'GMSK',
    extra: { threshold: 5.0 }.merge(extra)
  )
  PWN::SDR::Decoder::Base.run_iq(
    freq_obj: freq_obj,
    protocol: proto,
    sample_rate: rate,
    source: opts[:source],
    file: opts[:file],
    demod: demod,
    threshold: 5.0,
    note: '270.833 kbit/s GMSK — true-air path streams I/Q from RTL-SDR/Pluto and characterises TDMA burst duty; full Viterbi/BCCH SI decode is layered on Liquid when available.',
    describe: describe
  )
end

.help ⇒ Object 



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# File 'lib/pwn/sdr/decoder/gsm.rb', line 129

public_class_method def self.help
  puts "USAGE (true-air I/Q via PWN::FFI + detector fallback):
    #{self}.decode(
      freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq',
      source:   'optional - :auto|:rtlsdr|:adalm_pluto|:file',
      file:     'optional - .cu8/.cs16 capture'
    )

    #{self}.authors
  "
end

.parse_line(opts = {}) ⇒ Object 



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# File 'lib/pwn/sdr/decoder/gsm.rb', line 100

public_class_method def self.parse_line(opts = {})
  line = opts[:line].to_s
  f = line.split('|', -1)
  out = {
    protocol: 'GSM', frame_time: f[0], arfcn: f[1], chan_type: f[2],
    imsi: f[3], tmsi: f[4], mcc: f[5], mnc: f[6], lac: f[7],
    cell_id: f[8], rr_msg_type: f[9]
  }.reject { |_, v| v.to_s.empty? }
  if out[:imsi].to_s.length.between?(14, 16)
    out[:imsi_mcc]  = out[:imsi][0, 3]
    out[:imsi_mnc]  = out[:imsi][3, 3]
    out[:imsi_msin] = out[:imsi][6..]
  end
  bits = []
  bits << "ARFCN=#{out[:arfcn]}" if out[:arfcn]
  bits << "MCC/MNC=#{out[:mcc]}/#{out[:mnc]}" if out[:mcc]
  bits << "LAC=#{out[:lac]} CI=#{out[:cell_id]}" if out[:lac]
  bits << "IMSI=#{out[:imsi]}" if out[:imsi]
  bits << "TMSI=#{out[:tmsi]}" if out[:tmsi]
  out[:summary] = "GSM #{bits.join(' ')}".strip
  out
end