1 files changed, 126 insertions, 0 deletions
diff --git a/src/eax_dec.cpp b/src/eax_dec.cpp
new file mode 100644
index 000000000..70cdd9863
--- /dev/null
+++ b/src/eax_dec.cpp
@@ -0,0 +1,126 @@
+/*************************************************
+* EAX Mode Encryption Source File                *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/eax.h>
+#include <botan/lookup.h>
+#include <botan/xor_buf.h>
+#include <botan/parsing.h>
+#include <algorithm>
+
+namespace Botan {
+
+/*************************************************
+* EAX_Decryption Constructor                     *
+*************************************************/
+EAX_Decryption::EAX_Decryption(const std::string& cipher_name,
+                               u32bit tag_size) :
+   EAX_Base(cipher_name, tag_size)
+   {
+   queue.create(2*TAG_SIZE + DEFAULT_BUFFERSIZE);
+   queue_start = queue_end = 0;
+   }
+
+/*************************************************
+* EAX_Decryption Constructor                     *
+*************************************************/
+EAX_Decryption::EAX_Decryption(const std::string& cipher_name,
+                               const SymmetricKey& key,
+                               const InitializationVector& iv,
+                               u32bit tag_size) :
+   EAX_Base(cipher_name, tag_size)
+   {
+   set_key(key);
+   set_iv(iv);
+   queue.create(2*TAG_SIZE + DEFAULT_BUFFERSIZE);
+   queue_start = queue_end = 0;
+   }
+
+/*************************************************
+* Decrypt in EAX mode                            *
+*************************************************/
+void EAX_Decryption::write(const byte input[], u32bit length)
+   {
+   while(length)
+      {
+      const u32bit copied = std::min(length, queue.size() - queue_end);
+
+      queue.copy(queue_end, input, copied);
+      input += copied;
+      length -= copied;
+      queue_end += copied;
+
+      SecureVector<byte> block_buf(cipher->BLOCK_SIZE);
+      while((queue_end - queue_start) > TAG_SIZE)
+         {
+         u32bit removed = (queue_end - queue_start) - TAG_SIZE;
+         do_write(queue + queue_start, removed);
+         queue_start += removed;
+         }
+
+      if(queue_start + TAG_SIZE == queue_end &&
+         queue_start >= queue.size() / 2)
+         {
+         SecureVector<byte> queue_data(TAG_SIZE);
+         queue_data.copy(queue + queue_start, TAG_SIZE);
+         queue.copy(queue_data, TAG_SIZE);
+         queue_start = 0;
+         queue_end = TAG_SIZE;
+         }
+      }
+   }
+
+/*************************************************
+* Decrypt in EAX mode                            *
+*************************************************/
+void EAX_Decryption::do_write(const byte input[], u32bit length)
+   {
+   mac->update(input, length);
+
+   u32bit copied = std::min(BLOCK_SIZE - position, length);
+   xor_buf(buffer + position, input, copied);
+   send(buffer + position, copied);
+   input += copied;
+   length -= copied;
+   position += copied;
+
+   if(position == BLOCK_SIZE)
+      increment_counter();
+
+   while(length >= BLOCK_SIZE)
+      {
+      xor_buf(buffer, input, BLOCK_SIZE);
+      send(buffer, BLOCK_SIZE);
+
+      input += BLOCK_SIZE;
+      length -= BLOCK_SIZE;
+      increment_counter();
+      }
+
+   xor_buf(buffer + position, input, length);
+   send(buffer + position, length);
+   position += length;
+   }
+
+/*************************************************
+* Finish decrypting in EAX mode                  *
+*************************************************/
+void EAX_Decryption::end_msg()
+   {
+   if((queue_end - queue_start) != TAG_SIZE)
+      throw Integrity_Failure(name() + ": Message authentication failure");
+
+   SecureVector<byte> data_mac = mac->final();
+
+   for(u32bit j = 0; j != TAG_SIZE; ++j)
+      if(queue[queue_start+j] != (data_mac[j] ^ nonce_mac[j] ^ header_mac[j]))
+         throw Integrity_Failure(name() + ": Message authentication failure");
+
+   state.clear();
+   buffer.clear();
+   position = 0;
+   queue_start = queue_end = 0;
+   }
+
+}