1 files changed, 183 insertions, 0 deletions
diff --git a/src/modes/aead/siv/siv.cpp b/src/modes/aead/siv/siv.cpp
new file mode 100644
index 000000000..15fb16aa0
--- /dev/null
+++ b/src/modes/aead/siv/siv.cpp
@@ -0,0 +1,183 @@
+/*
+* SIV Mode Encryption
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/siv.h>
+#include <botan/cmac.h>
+#include <botan/ctr.h>
+#include <botan/parsing.h>
+#include <botan/internal/xor_buf.h>
+#include <algorithm>
+
+#include <iostream>
+#include <botan/hex.h>
+
+namespace Botan {
+
+SIV_Mode::SIV_Mode(BlockCipher* cipher) :
+   m_name(cipher->name() + "/SIV"),
+   m_ctr(new CTR_BE(cipher->clone())),
+   m_cmac(new CMAC(cipher))
+   {
+   }
+
+void SIV_Mode::clear()
+   {
+   m_ctr.reset();
+   m_nonce.clear();
+   m_msg_buf.clear();
+   m_ad_macs.clear();
+   }
+
+std::string SIV_Mode::name() const
+   {
+   return m_name;
+   }
+
+bool SIV_Mode::valid_nonce_length(size_t) const
+   {
+   return true;
+   }
+
+size_t SIV_Mode::update_granularity() const
+   {
+   /*
+   This value does not particularly matter as regardless SIV_Mode::update
+   buffers all input, so in theory this could be 1. However as for instance
+   Transformation_Filter creates update_granularity() byte buffers, use a
+   somewhat large size to avoid bouncing on a tiny buffer.
+   */
+   return 128;
+   }
+
+Key_Length_Specification SIV_Mode::key_spec() const
+   {
+   return m_cmac->key_spec().multiple(2);
+   }
+
+void SIV_Mode::key_schedule(const byte key[], size_t length)
+   {
+   const size_t keylen = length / 2;
+   m_cmac->set_key(key, keylen);
+   m_ctr->set_key(key + keylen, keylen);
+   m_ad_macs.clear();
+   }
+
+void SIV_Mode::set_associated_data_n(size_t n, const byte ad[], size_t length)
+   {
+   if(n >= m_ad_macs.size())
+      m_ad_macs.resize(n+1);
+
+   m_ad_macs[n] = m_cmac->process(ad, length);
+   }
+
+secure_vector<byte> SIV_Mode::start(const byte nonce[], size_t nonce_len)
+   {
+   if(!valid_nonce_length(nonce_len))
+      throw Invalid_IV_Length(name(), nonce_len);
+
+   if(nonce_len)
+      m_nonce = m_cmac->process(nonce, nonce_len);
+   else
+      m_nonce.clear();
+
+   m_msg_buf.clear();
+
+   return secure_vector<byte>();
+   }
+
+void SIV_Mode::update(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   const size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   m_msg_buf.insert(m_msg_buf.end(), buf, buf + sz);
+   buffer.resize(offset); // truncate msg
+   }
+
+secure_vector<byte> SIV_Mode::S2V(const byte* text, size_t text_len)
+   {
+   const byte zero[16] = { 0 };
+
+   secure_vector<byte> V = cmac().process(zero, 16);
+
+   for(size_t i = 0; i != m_ad_macs.size(); ++i)
+      {
+      V = CMAC::poly_double(V, 0x87);
+      V ^= m_ad_macs[i];
+      }
+
+   if(m_nonce.size())
+      {
+      V = CMAC::poly_double(V, 0x87);
+      V ^= m_nonce;
+      }
+
+   if(text_len < 16)
+      {
+      V = CMAC::poly_double(V, 0x87);
+      xor_buf(&V[0], text, text_len);
+      V[text_len] ^= 0x80;
+      return cmac().process(V);
+      }
+
+   cmac().update(text, text_len - 16);
+   xor_buf(&V[0], &text[text_len - 16], 16);
+   cmac().update(V);
+
+   return cmac().final();
+   }
+
+void SIV_Mode::set_ctr_iv(secure_vector<byte> V)
+   {
+   V[8] &= 0x7F;
+   V[12] &= 0x7F;
+
+   ctr().set_iv(&V[0], V.size());
+   }
+
+void SIV_Encryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+
+   buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
+
+   secure_vector<byte> V = S2V(&buffer[offset], buffer.size() - offset);
+
+   buffer.insert(buffer.begin() + offset, V.begin(), V.end());
+
+   set_ctr_iv(V);
+   ctr().cipher1(&buffer[offset + V.size()], buffer.size() - offset - V.size());
+   }
+
+void SIV_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+
+   buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
+
+   const size_t sz = buffer.size() - offset;
+
+   BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
+
+   secure_vector<byte> V(&buffer[offset], &buffer[offset + 16]);
+
+   set_ctr_iv(V);
+
+   ctr().cipher(&buffer[offset + V.size()],
+                &buffer[offset],
+                buffer.size() - offset - V.size());
+
+   secure_vector<byte> T = S2V(&buffer[offset], buffer.size() - offset - V.size());
+
+   if(T != V)
+      throw Integrity_Failure("SIV tag check failed");
+
+   buffer.resize(buffer.size() - tag_size());
+   }
+
+}