| /* -*- c++ -*- */ |
| /* |
| * Copyright 2014 <+YOU OR YOUR COMPANY+>. |
| * |
| * This is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 3, or (at your option) |
| * any later version. |
| * |
| * This software is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this software; see the file COPYING. If not, write to |
| * the Free Software Foundation, Inc., 51 Franklin Street, |
| * Boston, MA 02110-1301, USA. |
| */ |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #include <gnuradio/io_signature.h> |
| #include <grgsm/gsmtap.h> |
| #include <grgsm/endian.h> |
| #include <numeric> |
| #include "decryption_impl.h" |
| |
| extern "C" { |
| #include <osmocom/gsm/a5.h> |
| } |
| |
| const uint32_t BURST_SIZE=148; |
| |
| namespace gr { |
| namespace gsm { |
| |
| decryption::sptr |
| decryption::make(const std::vector<uint8_t> & k_c, unsigned int a5_version) |
| { |
| return gnuradio::get_initial_sptr |
| (new decryption_impl(k_c, a5_version)); |
| } |
| |
| /* |
| * The private constructor |
| */ |
| decryption_impl::decryption_impl(const std::vector<uint8_t> & k_c, unsigned int a5_version) |
| : gr::block("decryption", |
| gr::io_signature::make(0, 0, 0), |
| gr::io_signature::make(0, 0, 0)), |
| d_k_c_valid(false) |
| { |
| set_k_c(k_c); |
| set_a5_version(a5_version); |
| validate_k_c(); |
| |
| // std::cout << "Be careful with decryption block - it wasn't tested yet!" << std::endl; |
| message_port_register_in(pmt::mp("bursts")); |
| set_msg_handler(pmt::mp("bursts"), boost::bind(&decryption_impl::decrypt, this, _1)); |
| message_port_register_out(pmt::mp("bursts")); |
| } |
| |
| /* |
| * Virtual destructor |
| */ |
| decryption_impl::~decryption_impl() |
| { |
| } |
| |
| void decryption_impl::set_k_c(const std::vector<uint8_t> & k_c) |
| { |
| d_k_c = k_c; |
| } |
| |
| void decryption_impl::set_a5_version(unsigned int a5_version) |
| { |
| d_a5_version = 1; |
| if (a5_version >= 1 && a5_version <= 4) |
| { |
| d_a5_version = a5_version; |
| } |
| } |
| |
| void decryption_impl::validate_k_c() |
| { |
| if (d_k_c.size() == 0) |
| { |
| d_k_c_valid = false; |
| return; |
| } |
| else if ((d_a5_version < 4 && d_k_c.size() != 8) || (d_a5_version == 4 && d_k_c.size() != 16)) |
| { |
| d_k_c_valid = false; |
| return; |
| } |
| else |
| { |
| for (int i=0; i<d_k_c.size(); i++) |
| { |
| if (d_k_c[i] != 0) |
| { |
| d_k_c_valid = true; |
| return; |
| } |
| } |
| } |
| } |
| |
| void decryption_impl::decrypt(pmt::pmt_t msg) |
| { |
| if (!d_k_c_valid) |
| { |
| message_port_pub(pmt::mp("bursts"), msg); |
| } |
| else |
| { |
| uint8_t decrypted_data[BURST_SIZE]; |
| uint8_t keystream[114]; |
| |
| pmt::pmt_t header_plus_burst = pmt::cdr(msg); |
| gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst); |
| uint8_t * burst_binary = (uint8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr); |
| |
| uint32_t frame_number = be32toh(header->frame_number); |
| bool uplink_burst = (be16toh(header->arfcn) & 0x4000) ? true : false; |
| |
| if(uplink_burst){ |
| //process uplink burst |
| osmo_a5(d_a5_version, &d_k_c[0], frame_number, NULL, keystream); |
| } else { |
| //process downlink burst |
| osmo_a5(d_a5_version, &d_k_c[0], frame_number, keystream, NULL); |
| } |
| /* guard bits */ |
| for (int i = 0; i < 3; i++) { |
| decrypted_data[i] = burst_binary[i]; |
| } |
| //encrypt first part of the burst |
| for (int i = 0; i < 57; i++) { |
| decrypted_data[i+3] = keystream[i] ^ burst_binary[i+3]; |
| } |
| /* stealing bits and midamble */ |
| for (int i = 60; i < 88; i++) { |
| decrypted_data[i] = burst_binary[i]; |
| } |
| //encrypt second part of the burst |
| for (int i = 0; i < 57; i++) { |
| decrypted_data[i+88] = keystream[i+57] ^ burst_binary[i+88]; |
| } |
| /* guard bits */ |
| for (int i = 145; i < 148; i++) { |
| decrypted_data[i] = burst_binary[i]; |
| } |
| uint8_t new_header_plus_burst[sizeof(gsmtap_hdr)+BURST_SIZE]; |
| memcpy(new_header_plus_burst, header, sizeof(gsmtap_hdr)); |
| memcpy(new_header_plus_burst+sizeof(gsmtap_hdr), decrypted_data, BURST_SIZE); |
| |
| pmt::pmt_t msg_binary_blob = pmt::make_blob(new_header_plus_burst, sizeof(gsmtap_hdr)+BURST_SIZE); |
| pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, msg_binary_blob); |
| |
| message_port_pub(pmt::mp("bursts"), msg_out); |
| } |
| return; |
| } |
| } /* namespace gsm */ |
| } /* namespace gr */ |