1 files changed, 266 insertions, 0 deletions
diff --git a/src/lib/modes/aead/ccm/ccm.cpp b/src/lib/modes/aead/ccm/ccm.cpp
new file mode 100644
index 000000000..50fc38738
--- /dev/null
+++ b/src/lib/modes/aead/ccm/ccm.cpp
@@ -0,0 +1,266 @@
+/*
+* CCM Mode Encryption
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ccm.h>
+#include <botan/parsing.h>
+#include <botan/internal/xor_buf.h>
+#include <algorithm>
+
+namespace Botan {
+
+/*
+* CCM_Mode Constructor
+*/
+CCM_Mode::CCM_Mode(BlockCipher* cipher, size_t tag_size, size_t L) :
+   m_tag_size(tag_size),
+   m_L(L),
+   m_cipher(cipher)
+   {
+   if(m_cipher->block_size() != BS)
+      throw std::invalid_argument(m_cipher->name() + " cannot be used with CCM mode");
+
+   if(L < 2 || L > 8)
+      throw std::invalid_argument("Invalid CCM L value " + std::to_string(L));
+
+   if(tag_size < 4 || tag_size > 16 || tag_size % 2 != 0)
+      throw std::invalid_argument("invalid CCM tag length " + std::to_string(tag_size));
+   }
+
+void CCM_Mode::clear()
+   {
+   m_cipher.reset();
+   m_msg_buf.clear();
+   m_ad_buf.clear();
+   }
+
+std::string CCM_Mode::name() const
+   {
+   return (m_cipher->name() + "/CCM(" + std::to_string(tag_size()) + "," + std::to_string(L())) + ")";
+   }
+
+bool CCM_Mode::valid_nonce_length(size_t n) const
+   {
+   return (n == (15-L()));
+   }
+
+size_t CCM_Mode::default_nonce_length() const
+   {
+   return (15-L());
+   }
+
+size_t CCM_Mode::update_granularity() const
+   {
+   /*
+   This value does not particularly matter as regardless CCM_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 m_cipher->parallel_bytes();
+   }
+
+Key_Length_Specification CCM_Mode::key_spec() const
+   {
+   return m_cipher->key_spec();
+   }
+
+void CCM_Mode::key_schedule(const byte key[], size_t length)
+   {
+   m_cipher->set_key(key, length);
+   }
+
+void CCM_Mode::set_associated_data(const byte ad[], size_t length)
+   {
+   m_ad_buf.clear();
+
+   if(length)
+      {
+      // FIXME: support larger AD using length encoding rules
+      BOTAN_ASSERT(length < (0xFFFF - 0xFF), "Supported CCM AD length");
+
+      m_ad_buf.push_back(get_byte<u16bit>(0, length));
+      m_ad_buf.push_back(get_byte<u16bit>(1, length));
+      m_ad_buf += std::make_pair(ad, length);
+      while(m_ad_buf.size() % BS)
+         m_ad_buf.push_back(0); // pad with zeros to full block size
+      }
+   }
+
+secure_vector<byte> CCM_Mode::start(const byte nonce[], size_t nonce_len)
+   {
+   if(!valid_nonce_length(nonce_len))
+      throw Invalid_IV_Length(name(), nonce_len);
+
+   m_nonce.assign(nonce, nonce + nonce_len);
+   m_msg_buf.clear();
+
+   return secure_vector<byte>();
+   }
+
+void CCM_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
+   }
+
+void CCM_Mode::encode_length(size_t len, byte out[])
+   {
+   const size_t len_bytes = L();
+
+   BOTAN_ASSERT(len_bytes < sizeof(size_t), "Length field fits");
+
+   for(size_t i = 0; i != len_bytes; ++i)
+      out[i] = get_byte(sizeof(size_t)-i, len);
+
+   BOTAN_ASSERT((len >> (len_bytes*8)) == 0, "Message length fits in field");
+   }
+
+void CCM_Mode::inc(secure_vector<byte>& C)
+   {
+   for(size_t i = 0; i != C.size(); ++i)
+      if(++C[C.size()-i-1])
+         break;
+   }
+
+secure_vector<byte> CCM_Mode::format_b0(size_t sz)
+   {
+   secure_vector<byte> B0(BS);
+
+   const byte b_flags = (m_ad_buf.size() ? 64 : 0) + (((tag_size()/2)-1) << 3) + (L()-1);
+
+   B0[0] = b_flags;
+   copy_mem(&B0[1], &m_nonce[0], m_nonce.size());
+   encode_length(sz, &B0[m_nonce.size()+1]);
+
+   return B0;
+   }
+
+secure_vector<byte> CCM_Mode::format_c0()
+   {
+   secure_vector<byte> C(BS);
+
+   const byte a_flags = L()-1;
+
+   C[0] = a_flags;
+   copy_mem(&C[1], &m_nonce[0], m_nonce.size());
+
+   return C;
+   }
+
+void CCM_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());
+
+   const size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const secure_vector<byte>& ad = ad_buf();
+   BOTAN_ASSERT(ad.size() % BS == 0, "AD is block size multiple");
+
+   const BlockCipher& E = cipher();
+
+   secure_vector<byte> T(BS);
+   E.encrypt(format_b0(sz), T);
+
+   for(size_t i = 0; i != ad.size(); i += BS)
+      {
+      xor_buf(&T[0], &ad[i], BS);
+      E.encrypt(T);
+      }
+
+   secure_vector<byte> C = format_c0();
+   secure_vector<byte> S0(BS);
+   E.encrypt(C, S0);
+   inc(C);
+
+   secure_vector<byte> X(BS);
+
+   const byte* buf_end = &buf[sz];
+
+   while(buf != buf_end)
+      {
+      const size_t to_proc = std::min<size_t>(BS, buf_end - buf);
+
+      xor_buf(&T[0], buf, to_proc);
+      E.encrypt(T);
+
+      E.encrypt(C, X);
+      xor_buf(buf, &X[0], to_proc);
+      inc(C);
+
+      buf += to_proc;
+      }
+
+   T ^= S0;
+
+   buffer += std::make_pair(&T[0], tag_size());
+   }
+
+void CCM_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;
+   byte* buf = &buffer[offset];
+
+   BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
+
+   const secure_vector<byte>& ad = ad_buf();
+   BOTAN_ASSERT(ad.size() % BS == 0, "AD is block size multiple");
+
+   const BlockCipher& E = cipher();
+
+   secure_vector<byte> T(BS);
+   E.encrypt(format_b0(sz - tag_size()), T);
+
+   for(size_t i = 0; i != ad.size(); i += BS)
+      {
+      xor_buf(&T[0], &ad[i], BS);
+      E.encrypt(T);
+      }
+
+   secure_vector<byte> C = format_c0();
+
+   secure_vector<byte> S0(BS);
+   E.encrypt(C, S0);
+   inc(C);
+
+   secure_vector<byte> X(BS);
+
+   const byte* buf_end = &buf[sz - tag_size()];
+
+   while(buf != buf_end)
+      {
+      const size_t to_proc = std::min<size_t>(BS, buf_end - buf);
+
+      E.encrypt(C, X);
+      xor_buf(buf, &X[0], to_proc);
+      inc(C);
+
+      xor_buf(&T[0], buf, to_proc);
+      E.encrypt(T);
+
+      buf += to_proc;
+      }
+
+   T ^= S0;
+
+   if(!same_mem(&T[0], buf_end, tag_size()))
+      throw Integrity_Failure("CCM tag check failed");
+
+   buffer.resize(buffer.size() - tag_size());
+   }
+
+}