src/cipher.cpp

   1 /*
   2  *  anytun
   3  *
   4  *  The secure anycast tunneling protocol (satp) defines a protocol used
   5  *  for communication between any combination of unicast and anycast
   6  *  tunnel endpoints.  It has less protocol overhead than IPSec in Tunnel
   7  *  mode and allows tunneling of every ETHER TYPE protocol (e.g.
   8  *  ethernet, ip, arp ...). satp directly includes cryptography and
   9  *  message authentication based on the methodes used by SRTP.  It is
  10  *  intended to deliver a generic, scaleable and secure solution for
  11  *  tunneling and relaying of packets of any protocol.
  12  *
  13  *
  14  *  Copyright (C) 2007 anytun.org <satp@wirdorange.org>
  15  *
  16  *  This program is free software; you can redistribute it and/or modify
  17  *  it under the terms of the GNU General Public License version 2
  18  *  as published by the Free Software Foundation.
  19  *
  20  *  This program is distributed in the hope that it will be useful,
  21  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  *  GNU General Public License for more details.
  24  *
  25  *  You should have received a copy of the GNU General Public License
  26  *  along with this program (see the file COPYING included with this
  27  *  distribution); if not, write to the Free Software Foundation, Inc.,
  28  *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  29  */
  30
  31 #include <stdexcept>
  32 #include <iostream>
  33 #include <string>
  34 #include <cstdio>
  35 #include <gcrypt.h>
  36
  37 #include "cipher.h"
  38 #include "mpi.h"
  39 #include "log.h"
  40
  41
  42       // TODO: in should be const but does not work with getBuf() :(
  43 void Cipher::encrypt(PlainPacket & in, EncryptedPacket & out, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
  44 {
  45         u_int32_t len = cipher(in, in.getLength(), out.getPayload(), out.getPayloadLength(), seq_nr, sender_id, mux);
  46         out.setSenderId(sender_id);
  47         out.setSeqNr(seq_nr);
  48   out.setMux(mux);
  49         out.setPayloadLength(len);
  50 }
  51
  52       // TODO: in should be const but does not work with getBuf() :(
  53 void Cipher::decrypt(EncryptedPacket & in, PlainPacket & out)
  54 {
  55         u_int32_t len = decipher(in.getPayload() , in.getPayloadLength(), out, out.getLength(), in.getSeqNr(), in.getSenderId(), in.getMux());
  56         out.setLength(len);
  57 }
  58
  59
  60 //******* NullCipher *******
  61
  62 u_int32_t NullCipher::cipher(u_int8_t* in, u_int32_t ilen, u_int8_t* out, u_int32_t olen, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
  63 {
  64         std::memcpy(out, in, (ilen < olen) ? ilen : olen);
  65   return (ilen < olen) ? ilen : olen;
  66 }
  67
  68 u_int32_t NullCipher::decipher(u_int8_t* in, u_int32_t ilen, u_int8_t* out, u_int32_t olen, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
  69 {
  70         std::memcpy(out, in, (ilen < olen) ? ilen : olen);
  71   return (ilen < olen) ? ilen : olen;
  72 }
  73
  74
  75 //****** AesIcmCipher ******
  76
  77 AesIcmCipher::AesIcmCipher() : cipher_(NULL)
  78 {
  79       // TODO: hardcoded keysize
  80   gcry_error_t err = gcry_cipher_open( &cipher_, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CTR, 0 );
  81   if( err ) {
  82     char buf[STERROR_TEXT_MAX];
  83     buf[0] = 0;
  84     cLog.msg(Log::PRIO_CRIT) << "AesIcmCipher::AesIcmCipher: Failed to open cipher" << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
  85   }
  86 }
  87
  88
  89 AesIcmCipher::~AesIcmCipher()
  90 {
  91   if(cipher_)
  92     gcry_cipher_close( cipher_ );
  93 }
  94
  95 void AesIcmCipher::setKey(Buffer& key)
  96 {
  97   if(!cipher_)
  98     return;
  99
 100   gcry_error_t err = gcry_cipher_setkey( cipher_, key.getBuf(), key.getLength() );
 101   if( err ) {
 102     char buf[STERROR_TEXT_MAX];
 103     buf[0] = 0;
 104     cLog.msg(Log::PRIO_ERR) << "AesIcmCipher::setKey: Failed to set cipher key: " << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
 105   }
 106 }
 107
 108 void AesIcmCipher::setSalt(Buffer& salt)
 109 {
 110   salt_ = salt;
 111   if(!salt_[u_int32_t(0)])
 112     salt_[u_int32_t(0)] = 1; // TODO: this is a outstandingly ugly workaround
 113 }
 114
 115 u_int32_t AesIcmCipher::cipher(u_int8_t* in, u_int32_t ilen, u_int8_t* out, u_int32_t olen, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
 116 {
 117   calc(in, ilen, out, olen, seq_nr, sender_id, mux);
 118   return (ilen < olen) ? ilen : olen;
 119 }
 120
 121 u_int32_t AesIcmCipher::decipher(u_int8_t* in, u_int32_t ilen, u_int8_t* out, u_int32_t olen, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
 122 {
 123   calc(in, ilen, out, olen, seq_nr, sender_id, mux);
 124   return (ilen < olen) ? ilen : olen;
 125 }
 126
 127 void AesIcmCipher::calc(u_int8_t* in, u_int32_t ilen, u_int8_t* out, u_int32_t olen, seq_nr_t seq_nr, sender_id_t sender_id, mux_t mux)
 128 {
 129   if(!cipher_)
 130     return;
 131
 132   gcry_error_t err = gcry_cipher_reset( cipher_ );
 133   if( err ) {
 134     char buf[STERROR_TEXT_MAX];
 135     buf[0] = 0;
 136     cLog.msg(Log::PRIO_ERR) << "AesIcmCipher: Failed to reset cipher: " << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
 137     return;
 138   }
 139
 140   // set the IV ( = CTR)
 141   //==========================================================================
 142   //  //  where the 128-bit integer value IV SHALL be defined by the SSRC, the
 143   //  //  SRTP packet index i, and the SRTP session salting key k_s, as below.
 144   //  //
 145   //  //  IV = (k_s * 2^16) XOR (SSRC * 2^64) XOR (i * 2^16)
 146   //  //  sizeof(k_s) = 112 bit, random
 147
 148   Mpi ctr(128);                                                // TODO: hardcoded size
 149   Mpi salt(salt_.getBuf(), salt_.getLength());
 150   Mpi sid_mux(32);
 151   sid_mux = sender_id;
 152   Mpi mux_mpi(32);
 153   mux_mpi = mux;
 154   sid_mux = sid_mux ^ mux_mpi.mul2exp(16);
 155   Mpi seq(32);
 156   seq = seq_nr;
 157
 158   ctr = salt.mul2exp(16) ^ sid_mux.mul2exp(64) ^ seq.mul2exp(16);  // TODO: hardcoded size
 159
 160   size_t written;
 161   u_int8_t *ctr_buf = ctr.getNewBuf(&written);             // TODO: hardcoded size
 162   err = gcry_cipher_setctr( cipher_, ctr_buf, written );        // TODO: hardcoded size
 163   delete[] ctr_buf;
 164   if( err ) {
 165     char buf[STERROR_TEXT_MAX];
 166     buf[0] = 0;
 167     cLog.msg(Log::PRIO_ERR) << "AesIcmCipher: Failed to set cipher CTR: " << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
 168     return;
 169   }
 170
 171   err = gcry_cipher_encrypt( cipher_, out, olen, in, ilen );
 172   if( err ) {
 173     char buf[STERROR_TEXT_MAX];
 174     buf[0] = 0;
 175     cLog.msg(Log::PRIO_ERR) << "AesIcmCipher: Failed to generate cipher bitstream: " << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
 176     return;
 177   }
 178 }
 179