added support for configurabel auth tag length

9 files changed, 77 insertions, 20 deletions

diff --git a/src/anytun.cpp b/src/anytun.cpp
index c19ceb5..99f1560 100644
--- a/src/anytun.cpp
+++ b/src/anytun.cpp
@@ -149,7 +149,7 @@ void sender(TunDevice* dev, PacketSource* src)
     std::auto_ptr<AuthAlgo> a(AuthAlgoFactory::create(gOpt.getAuthAlgo(), KD_OUTBOUND) );
     
     PlainPacket plain_packet(MAX_PACKET_LENGTH);
-    EncryptedPacket encrypted_packet(MAX_PACKET_LENGTH);
+    EncryptedPacket encrypted_packet(MAX_PACKET_LENGTH, gOpt.getAuthTagLength());
     
     u_int16_t mux = gOpt.getMux();
     PacketSourceEndpoint emptyEndpoint;
@@ -237,7 +237,7 @@ void receiver(TunDevice* dev, PacketSource* src)
     std::auto_ptr<Cipher> c(CipherFactory::create(gOpt.getCipher(), KD_INBOUND, gOpt.getAnytun02Compat()));
     std::auto_ptr<AuthAlgo> a(AuthAlgoFactory::create(gOpt.getAuthAlgo(), KD_INBOUND));
     
-    EncryptedPacket encrypted_packet(MAX_PACKET_LENGTH);
+    EncryptedPacket encrypted_packet(MAX_PACKET_LENGTH, gOpt.getAuthTagLength());
     PlainPacket plain_packet(MAX_PACKET_LENGTH);
     
     while(1) {
diff --git a/src/authAlgo.h b/src/authAlgo.h
index cca706d..c446853 100644
--- a/src/authAlgo.h
+++ b/src/authAlgo.h
@@ -75,6 +75,8 @@ class NullAuthAlgo : public AuthAlgo
 public:
   void generate(KeyDerivation& kd, EncryptedPacket& packet);
   bool checkTag(KeyDerivation& kd, EncryptedPacket& packet);
+
+  static const u_int32_t DIGEST_LENGTH = 0;
 };
 
 #ifndef NO_CRYPT
diff --git a/src/authAlgoFactory.cpp b/src/authAlgoFactory.cpp
index 8fa16fc..c284f34 100644
--- a/src/authAlgoFactory.cpp
+++ b/src/authAlgoFactory.cpp
@@ -38,13 +38,25 @@
 
 AuthAlgo* AuthAlgoFactory::create(std::string const& type, kd_dir_t dir)
 {
-  if( type == "null" )
+  if(type == "null")
     return new NullAuthAlgo();
 #ifndef NO_CRYPT
-  else if( type == "sha1" )
+  else if(type == "sha1")
     return new Sha1AuthAlgo(dir);
 #endif
   else
     throw std::invalid_argument("auth algo not available");
 }
 
+u_int32_t AuthAlgoFactory::getDigestLength(std::string const& type)
+{
+  if(type == "null")
+    return NullAuthAlgo::DIGEST_LENGTH;
+#ifndef NO_CRYPT
+  else if(type == "sha1")
+    return Sha1AuthAlgo::DIGEST_LENGTH;
+#endif
+  else
+    throw std::invalid_argument("auth algo not available");
+}
+
diff --git a/src/authAlgoFactory.h b/src/authAlgoFactory.h
index ee38248..2dca567 100644
--- a/src/authAlgoFactory.h
+++ b/src/authAlgoFactory.h
@@ -41,6 +41,7 @@ class AuthAlgoFactory
 {
 public:
   static AuthAlgo* create(std::string const& type, kd_dir_t dir);
+  static u_int32_t getDigestLength(std::string const& type);
 
 private:
   AuthAlgoFactory();
diff --git a/src/encryptedPacket.cpp b/src/encryptedPacket.cpp
index c18551c..a5aec86 100644
--- a/src/encryptedPacket.cpp
+++ b/src/encryptedPacket.cpp
@@ -39,8 +39,8 @@
 #include "log.h"
 #include "anytunError.h"
 
-EncryptedPacket::EncryptedPacket(u_int32_t payload_length, bool allow_realloc)
-  : Buffer(payload_length + sizeof(struct HeaderStruct), allow_realloc)
+EncryptedPacket::EncryptedPacket(u_int32_t payload_length, u_int32_t auth_tag_length, bool allow_realloc)
+  : Buffer(payload_length + sizeof(struct HeaderStruct), allow_realloc), auth_tag_length_(auth_tag_length)
 {
   header_ = reinterpret_cast<struct HeaderStruct*>(buf_);
   payload_ = buf_ + sizeof(struct HeaderStruct);
@@ -118,7 +118,7 @@ u_int32_t EncryptedPacket::getPayloadLength() const
   if(!auth_tag_)
     return (length_ > sizeof(struct HeaderStruct)) ? (length_ - sizeof(struct HeaderStruct)) : 0;
   
-  return (length_ > (sizeof(struct HeaderStruct) + AUTHTAG_SIZE)) ? (length_ - sizeof(struct HeaderStruct) - AUTHTAG_SIZE) : 0;
+  return (length_ > (sizeof(struct HeaderStruct) + auth_tag_length_)) ? (length_ - sizeof(struct HeaderStruct) - auth_tag_length_) : 0;
 }
 
 void EncryptedPacket::setPayloadLength(u_int32_t payload_length)
@@ -143,11 +143,11 @@ void EncryptedPacket::reinit()
   
   if(auth_tag_)
   {
-    if(length_ < (sizeof(struct HeaderStruct) + AUTHTAG_SIZE)) {
+    if(length_ < (sizeof(struct HeaderStruct) + auth_tag_length_)) {
       auth_tag_ = NULL;
       AnytunError::throwErr() << "auth-tag can't be enabled, buffer is too small"; 
     }
-    auth_tag_ = buf_ + length_ - AUTHTAG_SIZE;
+    auth_tag_ = buf_ + length_ - auth_tag_length_;
   }  
 }
 
@@ -169,7 +169,7 @@ u_int32_t EncryptedPacket::getAuthenticatedPortionLength()
   if(!auth_tag_)
     return length_;
   
-  return (length_ > AUTHTAG_SIZE) ? (length_ - AUTHTAG_SIZE) : 0;
+  return (length_ > auth_tag_length_) ? (length_ - auth_tag_length_) : 0;
 }
 
 void EncryptedPacket::withAuthTag(bool b)
@@ -179,10 +179,10 @@ void EncryptedPacket::withAuthTag(bool b)
   
   if(b)
   {
-    if(length_ < (sizeof(struct HeaderStruct) + AUTHTAG_SIZE))
+    if(length_ < (sizeof(struct HeaderStruct) + auth_tag_length_))
       AnytunError::throwErr() << "auth-tag can't be enabled, buffer is too small";
     
-    auth_tag_ = buf_ + length_ - AUTHTAG_SIZE;
+    auth_tag_ = buf_ + length_ - auth_tag_length_;
   }
   else
     auth_tag_ = NULL;
@@ -194,7 +194,7 @@ void EncryptedPacket::addAuthTag()
     return;
 
   auth_tag_ = buf_; // will be set to the correct value @ reinit
-  setLength(length_ + AUTHTAG_SIZE);
+  setLength(length_ + auth_tag_length_);
   if(auth_tag_ == buf_) // reinit was not called by setLength
     reinit();
 }
@@ -205,7 +205,7 @@ void EncryptedPacket::removeAuthTag()
     return;
 
   auth_tag_ = NULL;
-  setLength(length_ - AUTHTAG_SIZE);
+  setLength(length_ - auth_tag_length_);
 }
 
 u_int8_t* EncryptedPacket::getAuthTag()
@@ -216,7 +216,7 @@ u_int8_t* EncryptedPacket::getAuthTag()
 u_int32_t EncryptedPacket::getAuthTagLength()
 {
   if(auth_tag_)
-    return AUTHTAG_SIZE;
+    return auth_tag_length_;
 
   return 0;
 }
diff --git a/src/encryptedPacket.h b/src/encryptedPacket.h
index 4f64022..618fa44 100644
--- a/src/encryptedPacket.h
+++ b/src/encryptedPacket.h
@@ -45,7 +45,7 @@ public:
    * @param the length of the payload 
    * @param allow reallocation of buffer
    */
-  EncryptedPacket(u_int32_t payload_length, bool allow_realloc = false);
+  EncryptedPacket(u_int32_t payload_length, u_int32_t auth_tag_length, bool allow_realloc = false);
 
   /**
    * Packet destructor
@@ -152,7 +152,7 @@ private:
   struct HeaderStruct* header_;
 	u_int8_t * payload_;
   u_int8_t * auth_tag_;
-  static const u_int32_t AUTHTAG_SIZE = 10;  // TODO: hardcoded size
+  u_int32_t  auth_tag_length_;
 };
 
 #endif
diff --git a/src/man/anytun.8.txt b/src/man/anytun.8.txt
index 05a650c..fa30441 100644
--- a/src/man/anytun.8.txt
+++ b/src/man/anytun.8.txt
@@ -41,6 +41,7 @@ SYNOPSIS
 [ *-A|--salt* <master salt> ]
 [ *-c|--cipher* <cipher type> ]
 [ *-a|--auth-algo* <algo type> ]
+[ *-b|--auth-tag-length* <length> ]
 
 DESCRIPTION
 -----------
@@ -362,8 +363,14 @@ Possible values:
 * *null* - no message authentication
 * *sha1* - HMAC-SHA1, default value
 
-If HMAC-SHA1 is used, the packet length is increased by
-10 bytes. These 10 bytes contain the authentication data.
+If HMAC-SHA1 is used, the packet length is increased. The additional bytes 
+contain the authentication data. see *-b|--auth-tag-length* for more info.
+
+-b|--auth-tag-length <length>
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The number of bytes to use for the auth tag. This value defaults to 10 bytes 
+unless the *null* auth algo is used in which case it defaults to 0. 
 
 
 EXAMPLES
diff --git a/src/options.cpp b/src/options.cpp
index e58278a..94e3c44 100644
--- a/src/options.cpp
+++ b/src/options.cpp
@@ -38,6 +38,7 @@
 #include "datatypes.h"
 #include "options.h"
 #include "log.h"
+#include "authAlgoFactory.h"
 
 std::ostream& operator<<(std::ostream& stream, syntax_error const& error)
 {
@@ -181,10 +182,12 @@ Options::Options() : key_(u_int32_t(0)), salt_(u_int32_t(0))
 #ifndef NO_CRYPT
   cipher_ = "aes-ctr";
   auth_algo_ = "sha1";
+  auth_tag_length_ = 10;
   kd_prf_ = "aes-ctr";
 #else
   cipher_ = "null";
   auth_algo_ = "null";
+  auth_tag_length_ = 0;
   kd_prf_ = "null";
 #endif
   role_ = ROLE_LEFT;
@@ -412,6 +415,7 @@ bool Options::parse(int argc, char* argv[])
   #ifndef NO_CRYPT
     PARSE_SCALAR_PARAM("-c","--cipher", cipher_)
     PARSE_SCALAR_PARAM("-a","--auth-algo", auth_algo_)
+    PARSE_SCALAR_PARAM("-b","--auth-tag-length", auth_tag_length_)
   #endif
 
 #endif
@@ -443,6 +447,19 @@ void Options::parse_post()
     kd_prf_ = "null";
   if((cipher_ != "null" || auth_algo_ != "null") && kd_prf_ == "null")
     cLog.msg(Log::PRIO_WARNING) << "using NULL key derivation with encryption and or authentication enabled!";
+
+
+#if defined(ANYTUN_OPTIONS)
+  u_int32_t tag_len_max = AuthAlgoFactory::getDigestLength(auth_algo_);
+  if(!tag_len_max) auth_tag_length_ = 0;
+  else if(tag_len_max < auth_tag_length_) {
+    cLog.msg(Log::PRIO_WARNING) << auth_algo_ << " auth algo can't generate tags of length " << auth_tag_length_ << ", using maximum tag length(" << tag_len_max << ")";
+    auth_tag_length_ = tag_len_max;
+  }
+#endif
+
+  if(anytun02_compat_)
+    cLog.msg(Log::PRIO_WARNING) << "--anytun02-compat is deprecated and very likly to be removed by the next release";
   
   if(dev_name_ == "" && dev_type_ == "")
     dev_type_ = "tun";
@@ -528,7 +545,6 @@ void Options::printUsage()
  #ifndef NO_CRYPT
   std::cout << "   [-k|--kd-prf] <kd-prf type>         key derivation pseudo random function" << std::endl;
   std::cout << "   [-e|--role] <role>                  left (alice) or right (bob)" << std::endl;
-  std::cout << "   [-O|--anytun02-compat]              enable compatiblity mode for anytun 0.2.x and prior" << std::endl;
  #ifndef NO_PASSPHRASE
   std::cout << "   [-E|--passphrase] <pass phrase>     a passprhase to generate master key and salt from" << std::endl;
  #endif
@@ -542,6 +558,7 @@ void Options::printUsage()
  #ifndef NO_CRYPT
   std::cout << "   [-c|--cipher] <cipher type>         payload encryption algorithm" << std::endl;
   std::cout << "   [-a|--auth-algo] <algo type>        message authentication algorithm" << std::endl;
+  std::cout << "   [-b|--auth-tag-length]              length of the auth tag" << std::endl;
  #endif
 
 #endif
@@ -602,6 +619,7 @@ void Options::printOptions()
   std::cout << std::endl;
   std::cout << "cipher = '" << cipher_ << "'" << std::endl;
   std::cout << "auth_algo = '" << auth_algo_ << "'" << std::endl;
+  std::cout << "auth_tag_length = " << auth_tag_length_ << std::endl;
   std::cout << "kd_prf = '" << kd_prf_ << "'" << std::endl;
   std::cout << "role = ";
   switch(role_) {
@@ -971,6 +989,20 @@ Options& Options::setAuthAlgo(std::string a)
   return *this;
 }
 
+u_int32_t Options::getAuthTagLength()
+{
+  ReadersLock lock(mutex);
+  return auth_tag_length_;
+}
+
+Options& Options::setAuthTagLength(u_int32_t a)
+{
+  WritersLock lock(mutex);
+  auth_tag_length_ = a;
+  return *this;
+}
+
+
 std::string Options::getKdPrf()
 {
   ReadersLock lock(mutex);
diff --git a/src/options.h b/src/options.h
index 480d1c7..71229cc 100644
--- a/src/options.h
+++ b/src/options.h
@@ -149,6 +149,8 @@ public:
   Options& setCipher(std::string c);
   std::string getAuthAlgo();
   Options& setAuthAlgo(std::string a);
+  u_int32_t getAuthTagLength();
+  Options& setAuthTagLength(u_int32_t a);
   std::string getKdPrf();
   Options& setKdPrf(std::string k);
   role_t getRole();
@@ -212,6 +214,7 @@ private:
 
   std::string cipher_;
   std::string auth_algo_;
+  u_int32_t auth_tag_length_;
   std::string kd_prf_;
   role_t role_;
   bool anytun02_compat_;