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 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 "authAlgo.h"
  32 #include "log.h"
  33 #include "buffer.h"
  34 #include "encryptedPacket.h"
  35
  36 #include <iostream>
  37
  38 #include <gcrypt.h>
  39
  40 //****** NullAuthAlgo ******
  41 void NullAuthAlgo::generate(EncryptedPacket& packet)
  42 {
  43 }
  44
  45 bool NullAuthAlgo::checkTag(EncryptedPacket& packet)
  46 {
  47   return true;
  48 }
  49
  50 u_int32_t NullAuthAlgo::getMaxLength()
  51 {
  52   return MAX_LENGTH_;
  53 }
  54
  55 //****** Sha1AuthAlgo ******
  56
  57 Sha1AuthAlgo::Sha1AuthAlgo() : ctx_(NULL)
  58 {
  59   gcry_error_t err = gcry_md_open( &ctx_, GCRY_MD_SHA1, GCRY_MD_FLAG_HMAC );
  60   if( err )
  61     cLog.msg(Log::PRIO_CRIT) << "Sha1AuthAlgo::Sha1AuthAlgo: Failed to open message digest algo";
  62 }
  63
  64 Sha1AuthAlgo::~Sha1AuthAlgo()
  65 {
  66   if(ctx_)
  67     gcry_md_close( ctx_ );
  68 }
  69
  70 void Sha1AuthAlgo::setKey(Buffer& key)
  71 {
  72   if(!ctx_)
  73     return;
  74
  75   gcry_error_t err = gcry_md_setkey( ctx_, key.getBuf(), key.getLength() );
  76   if( err )
  77     cLog.msg(Log::PRIO_ERR) << "Sha1AuthAlgo::setKey: Failed to set cipher key: " << gpg_strerror( err );
  78 }
  79
  80 void Sha1AuthAlgo::generate(EncryptedPacket& packet)
  81 {
  82   if(!packet.getAuthTagLength())
  83     return;
  84
  85   gcry_md_reset( ctx_ );
  86
  87   gcry_md_write( ctx_, packet.getAuthenticatedPortion(), packet.getAuthenticatedPortionLength() );
  88   gcry_md_final( ctx_ );
  89
  90   u_int8_t* tag = packet.getAuthTag();
  91   if(packet.getAuthTagLength() > MAX_LENGTH_)
  92     std::memset(tag, 0, (packet.getAuthTagLength() - MAX_LENGTH_));
  93
  94   u_int8_t* hmac = gcry_md_read(ctx_, 0);
  95   u_int32_t length = (packet.getAuthTagLength() < MAX_LENGTH_) ? packet.getAuthTagLength() : MAX_LENGTH_;
  96   std::memcpy(&tag[packet.getAuthTagLength() - length], &hmac[MAX_LENGTH_ - length], length);
  97 }
  98
  99 bool Sha1AuthAlgo::checkTag(EncryptedPacket& packet)
 100 {
 101   if(!packet.getAuthTagLength())
 102     return true;
 103
 104   gcry_md_reset( ctx_ );
 105
 106   gcry_md_write( ctx_, packet.getAuthenticatedPortion(), packet.getAuthenticatedPortionLength() );
 107   gcry_md_final( ctx_ );
 108
 109   u_int8_t* tag = packet.getAuthTag();
 110   if(packet.getAuthTagLength() > MAX_LENGTH_)
 111     for(u_int32_t i=0; i < (packet.getAuthTagLength() - MAX_LENGTH_); ++i)
 112       if(tag[i]) return false;
 113
 114   u_int8_t* hmac = gcry_md_read(ctx_, 0);
 115   u_int32_t length = (packet.getAuthTagLength() < MAX_LENGTH_) ? packet.getAuthTagLength() : MAX_LENGTH_;
 116   if(std::memcmp(&tag[packet.getAuthTagLength() - length], &hmac[MAX_LENGTH_ - length], length))
 117     return false;
 118
 119   return true;
 120 }
 121
 122 u_int32_t Sha1AuthAlgo::getMaxLength()
 123 {
 124   return MAX_LENGTH_;
 125 }