src/authAlgo.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) 2007-2008 Othmar Gsenger, Erwin Nindl,
  15  *                          Christian Pointner <satp@wirdorange.org>
  16  *
  17  *  This file is part of Anytun.
  18  *
  19  *  Anytun is free software: you can redistribute it and/or modify
  20  *  it under the terms of the GNU General Public License version 3 as
  21  *  published by the Free Software Foundation.
  22  *
  23  *  Anytun is distributed in the hope that it will be useful,
  24  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  25  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26  *  GNU General Public License for more details.
  27  *
  28  *  You should have received a copy of the GNU General Public License
  29  *  along with anytun.  If not, see <http://www.gnu.org/licenses/>.
  30  */
  31
  32 #include "authAlgo.h"
  33 #include "log.h"
  34 #include "buffer.h"
  35 #include "encryptedPacket.h"
  36
  37 #include <iostream>
  38
  39 #include <gcrypt.h>
  40
  41 //****** NullAuthAlgo ******
  42 void NullAuthAlgo::generate(EncryptedPacket& packet)
  43 {
  44 }
  45
  46 bool NullAuthAlgo::checkTag(EncryptedPacket& packet)
  47 {
  48   return true;
  49 }
  50
  51 u_int32_t NullAuthAlgo::getMaxLength()
  52 {
  53   return MAX_LENGTH_;
  54 }
  55
  56 //****** Sha1AuthAlgo ******
  57
  58 Sha1AuthAlgo::Sha1AuthAlgo() : ctx_(NULL)
  59 {
  60   gcry_error_t err = gcry_md_open( &ctx_, GCRY_MD_SHA1, GCRY_MD_FLAG_HMAC );
  61   if( err )
  62     cLog.msg(Log::PRIO_CRIT) << "Sha1AuthAlgo::Sha1AuthAlgo: Failed to open message digest algo";
  63 }
  64
  65 Sha1AuthAlgo::~Sha1AuthAlgo()
  66 {
  67   if(ctx_)
  68     gcry_md_close( ctx_ );
  69 }
  70
  71 void Sha1AuthAlgo::setKey(Buffer& key)
  72 {
  73   if(!ctx_)
  74     return;
  75
  76   gcry_error_t err = gcry_md_setkey( ctx_, key.getBuf(), key.getLength() );
  77   if( err ) {
  78     char buf[STERROR_TEXT_MAX];
  79     buf[0] = 0;
  80     cLog.msg(Log::PRIO_ERR) << "Sha1AuthAlgo::setKey: Failed to set cipher key: " << gpg_strerror_r(err, buf, STERROR_TEXT_MAX);
  81   }
  82 }
  83
  84 void Sha1AuthAlgo::generate(EncryptedPacket& packet)
  85 {
  86   if(!packet.getAuthTagLength())
  87     return;
  88
  89   gcry_md_reset( ctx_ );
  90
  91   gcry_md_write( ctx_, packet.getAuthenticatedPortion(), packet.getAuthenticatedPortionLength() );
  92   gcry_md_final( ctx_ );
  93
  94   u_int8_t* tag = packet.getAuthTag();
  95   if(packet.getAuthTagLength() > MAX_LENGTH_)
  96     std::memset(tag, 0, (packet.getAuthTagLength() - MAX_LENGTH_));
  97
  98   u_int8_t* hmac = gcry_md_read(ctx_, 0);
  99   u_int32_t length = (packet.getAuthTagLength() < MAX_LENGTH_) ? packet.getAuthTagLength() : MAX_LENGTH_;
 100   std::memcpy(&tag[packet.getAuthTagLength() - length], &hmac[MAX_LENGTH_ - length], length);
 101 }
 102
 103 bool Sha1AuthAlgo::checkTag(EncryptedPacket& packet)
 104 {
 105   if(!packet.getAuthTagLength())
 106     return true;
 107
 108   gcry_md_reset( ctx_ );
 109
 110   gcry_md_write( ctx_, packet.getAuthenticatedPortion(), packet.getAuthenticatedPortionLength() );
 111   gcry_md_final( ctx_ );
 112
 113   u_int8_t* tag = packet.getAuthTag();
 114   if(packet.getAuthTagLength() > MAX_LENGTH_)
 115     for(u_int32_t i=0; i < (packet.getAuthTagLength() - MAX_LENGTH_); ++i)
 116       if(tag[i]) return false;
 117
 118   u_int8_t* hmac = gcry_md_read(ctx_, 0);
 119   u_int32_t length = (packet.getAuthTagLength() < MAX_LENGTH_) ? packet.getAuthTagLength() : MAX_LENGTH_;
 120   if(std::memcmp(&tag[packet.getAuthTagLength() - length], &hmac[MAX_LENGTH_ - length], length))
 121     return false;
 122
 123   return true;
 124 }
 125
 126 u_int32_t Sha1AuthAlgo::getMaxLength()
 127 {
 128   return MAX_LENGTH_;
 129 }