1 files changed, 444 insertions, 0 deletions
diff --git a/src/modes/aead/ocb/ocb.cpp b/src/modes/aead/ocb/ocb.cpp
new file mode 100644
index 000000000..4cbd8bde8
--- /dev/null
+++ b/src/modes/aead/ocb/ocb.cpp
@@ -0,0 +1,444 @@
+/*
+* OCB Mode
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ocb.h>
+#include <botan/cmac.h>
+#include <botan/internal/xor_buf.h>
+#include <botan/internal/bit_ops.h>
+#include <algorithm>
+
+namespace Botan {
+
+// Has to be in Botan namespace so unique_ptr can reference it
+class L_computer
+   {
+   public:
+      L_computer(const BlockCipher& cipher)
+         {
+         m_L_star.resize(cipher.block_size());
+         cipher.encrypt(m_L_star);
+         m_L_dollar = poly_double(star());
+         m_L.push_back(poly_double(dollar()));
+         }
+
+      const secure_vector<byte>& star() const { return m_L_star; }
+
+      const secure_vector<byte>& dollar() const { return m_L_dollar; }
+
+      const secure_vector<byte>& operator()(size_t i) const { return get(i); }
+
+      const secure_vector<byte>& get(size_t i) const
+         {
+         while(m_L.size() <= i)
+            m_L.push_back(poly_double(m_L.back()));
+
+         return m_L.at(i);
+         }
+
+   private:
+      secure_vector<byte> poly_double(const secure_vector<byte>& in) const
+         {
+         return CMAC::poly_double(in, 0x87);
+         }
+
+      secure_vector<byte> m_L_dollar, m_L_star;
+      mutable std::vector<secure_vector<byte>> m_L;
+   };
+
+class Nonce_State
+   {
+   public:
+      Nonce_State(const BlockCipher& cipher) : m_cipher(cipher) {}
+
+      secure_vector<byte> update_nonce(const byte nonce[],
+                                       size_t nonce_len);
+   private:
+      const BlockCipher& m_cipher;
+      secure_vector<byte> m_last_nonce;
+      secure_vector<byte> m_stretch;
+   };
+
+secure_vector<byte>
+Nonce_State::update_nonce(const byte nonce[], size_t nonce_len)
+   {
+   const size_t BS = 16;
+
+   BOTAN_ASSERT(nonce_len < BS, "Nonce is less than 128 bits");
+
+   secure_vector<byte> nonce_buf(BS);
+
+   copy_mem(&nonce_buf[BS - nonce_len], nonce, nonce_len);
+   nonce_buf[BS - nonce_len - 1] = 1;
+
+   const byte bottom = nonce_buf[15] & 0x3F;
+   nonce_buf[15] &= 0xC0;
+
+   const bool need_new_stretch = (m_last_nonce != nonce_buf);
+
+   if(need_new_stretch)
+      {
+      m_last_nonce = nonce_buf;
+
+      m_cipher.encrypt(nonce_buf);
+
+      for(size_t i = 0; i != 8; ++i)
+         nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+1]);
+
+      m_stretch = nonce_buf;
+      }
+
+   // now set the offset from stretch and bottom
+
+   const size_t shift_bytes = bottom / 8;
+   const size_t shift_bits  = bottom % 8;
+
+   secure_vector<byte> offset(BS);
+   for(size_t i = 0; i != BS; ++i)
+      {
+      offset[i]  = (m_stretch[i+shift_bytes] << shift_bits);
+      offset[i] |= (m_stretch[i+shift_bytes+1] >> (8-shift_bits));
+      }
+
+   return offset;
+   }
+
+namespace {
+
+/*
+* OCB's HASH
+*/
+secure_vector<byte> ocb_hash(const L_computer& L,
+                             const BlockCipher& cipher,
+                             const byte ad[], size_t ad_len)
+   {
+   const size_t BS = cipher.block_size();
+
+   secure_vector<byte> sum(BS);
+   secure_vector<byte> offset(BS);
+
+   secure_vector<byte> buf(BS);
+
+   const size_t ad_blocks = (ad_len / BS);
+   const size_t ad_remainder = (ad_len % BS);
+
+   for(size_t i = 0; i != ad_blocks; ++i)
+      {
+      // this loop could run in parallel
+      offset ^= L(ctz(i+1));
+
+      buf = offset;
+      xor_buf(&buf[0], &ad[BS*i], BS);
+
+      cipher.encrypt(buf);
+
+      sum ^= buf;
+      }
+
+   if(ad_remainder)
+      {
+      offset ^= L.star();
+
+      buf = offset;
+      xor_buf(&buf[0], &ad[BS*ad_blocks], ad_remainder);
+      buf[ad_len % BS] ^= 0x80;
+
+      cipher.encrypt(buf);
+
+      sum ^= buf;
+      }
+
+   return sum;
+   }
+
+}
+
+OCB_Mode::OCB_Mode(BlockCipher* cipher, size_t tag_size) :
+   m_cipher(cipher),
+   m_tag_size(tag_size),
+   m_ad_hash(BS), m_offset(BS), m_checksum(BS)
+   {
+   if(m_cipher->block_size() != BS)
+      throw std::invalid_argument("OCB requires a 128 bit cipher so cannot be used with " +
+                                  m_cipher->name());
+
+   if(m_tag_size != 16) // fixme: 64, 96 bits also supported
+      throw std::invalid_argument("OCB cannot produce a " + std::to_string(m_tag_size) +
+                                  " byte tag");
+
+   }
+
+OCB_Mode::~OCB_Mode() { /* for unique_ptr destructor */ }
+
+void OCB_Mode::clear()
+   {
+   m_cipher.reset();
+   m_L.reset();
+   zeroise(m_ad_hash);
+   zeroise(m_offset);
+   zeroise(m_checksum);
+   }
+
+bool OCB_Mode::valid_nonce_length(size_t length) const
+   {
+   return (length > 0 && length < 16);
+   }
+
+std::string OCB_Mode::name() const
+   {
+   return m_cipher->name() + "/OCB"; // include tag size
+   }
+
+size_t OCB_Mode::update_granularity() const
+   {
+   return 8 * m_cipher->parallel_bytes();
+   }
+
+Key_Length_Specification OCB_Mode::key_spec() const
+   {
+   return m_cipher->key_spec();
+   }
+
+void OCB_Mode::key_schedule(const byte key[], size_t length)
+   {
+   m_cipher->set_key(key, length);
+   m_L.reset(new L_computer(*m_cipher));
+   m_nonce_state.reset(new Nonce_State(*m_cipher));
+   }
+
+void OCB_Mode::set_associated_data(const byte ad[], size_t ad_len)
+   {
+   BOTAN_ASSERT(m_L, "A key was set");
+   m_ad_hash = ocb_hash(*m_L, *m_cipher, &ad[0], ad_len);
+   }
+
+secure_vector<byte> OCB_Mode::start(const byte nonce[], size_t nonce_len)
+   {
+   if(!valid_nonce_length(nonce_len))
+      throw Invalid_IV_Length(name(), nonce_len);
+
+   BOTAN_ASSERT(m_nonce_state, "A key was set");
+
+   m_offset = m_nonce_state->update_nonce(nonce, nonce_len);
+   zeroise(m_checksum);
+   m_block_index = 0;
+
+   return secure_vector<byte>();
+   }
+
+void OCB_Encryption::encrypt(byte buffer[], size_t blocks)
+   {
+   const L_computer& L = *m_L; // convenient name
+
+   const size_t par_bytes = m_cipher->parallel_bytes();
+
+   BOTAN_ASSERT(par_bytes % BS == 0, "Cipher is parallel in full blocks");
+
+   const size_t par_blocks = par_bytes / BS;
+
+   secure_vector<byte> csum_accum(par_bytes);
+   secure_vector<byte> offsets(par_bytes);
+
+   size_t blocks_left = blocks;
+
+   while(blocks_left)
+      {
+      const size_t proc_blocks = std::min(blocks_left, par_blocks);
+      const size_t proc_bytes = proc_blocks * BS;
+
+      for(size_t i = 0; i != proc_blocks; ++i)
+         { // could be done in parallel
+         m_offset ^= L(ctz(++m_block_index));
+         copy_mem(&offsets[BS*i], &m_offset[0], BS);
+         }
+
+      xor_buf(&csum_accum[0], &buffer[0], proc_bytes);
+
+      xor_buf(&buffer[0], &offsets[0], proc_bytes);
+
+      m_cipher->encrypt_n(&buffer[0], &buffer[0], proc_blocks);
+
+      xor_buf(&buffer[0], &offsets[0], proc_bytes);
+
+      buffer += proc_bytes;
+      blocks_left -= proc_blocks;
+      }
+
+   // fold into checksum
+   for(size_t i = 0; i != csum_accum.size(); ++i)
+      m_checksum[i % BS] ^= csum_accum[i];
+   }
+
+void OCB_Encryption::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];
+
+   BOTAN_ASSERT(sz % BS == 0, "Input length is an even number of blocks");
+
+   encrypt(buf, sz / BS);
+   }
+
+void OCB_Encryption::finish(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];
+
+   if(sz)
+      {
+      const size_t final_full_blocks = sz / BS;
+      const size_t remainder_bytes = sz - (final_full_blocks * BS);
+
+      encrypt(buf, final_full_blocks);
+
+      if(remainder_bytes)
+         {
+         BOTAN_ASSERT(remainder_bytes < BS, "Only a partial block left");
+         byte* remainder = &buf[sz - remainder_bytes];
+
+         xor_buf(&m_checksum[0], &remainder[0], remainder_bytes);
+         m_checksum[remainder_bytes] ^= 0x80;
+
+         m_offset ^= m_L->star(); // Offset_*
+
+         secure_vector<byte> buf(BS);
+         m_cipher->encrypt(m_offset, buf);
+         xor_buf(&remainder[0], &buf[0], remainder_bytes);
+         }
+      }
+
+   // now compute the tag
+   secure_vector<byte> mac = m_offset;
+   mac ^= m_checksum;
+   mac ^= m_L->dollar();
+
+   m_cipher->encrypt(mac);
+
+   mac ^= m_ad_hash;
+
+   buffer += std::make_pair(&mac[0], tag_size());
+
+   zeroise(m_checksum);
+   zeroise(m_offset);
+   m_block_index = 0;
+   }
+
+void OCB_Decryption::decrypt(byte buffer[], size_t blocks)
+   {
+   const L_computer& L = *m_L; // convenient name
+
+   const size_t par_bytes = m_cipher->parallel_bytes();
+
+   BOTAN_ASSERT(par_bytes % BS == 0, "Cipher is parallel in full blocks");
+
+   const size_t par_blocks = par_bytes / BS;
+
+   secure_vector<byte> csum_accum(par_bytes);
+   secure_vector<byte> offsets(par_bytes);
+
+   size_t blocks_left = blocks;
+
+   while(blocks_left)
+      {
+      const size_t proc_blocks = std::min(blocks_left, par_blocks);
+      const size_t proc_bytes = proc_blocks * BS;
+
+      for(size_t i = 0; i != proc_blocks; ++i)
+         { // could be done in parallel
+         m_offset ^= L(ctz(++m_block_index));
+         copy_mem(&offsets[BS*i], &m_offset[0], BS);
+         }
+
+      xor_buf(&buffer[0], &offsets[0], proc_bytes);
+
+      m_cipher->decrypt_n(&buffer[0], &buffer[0], proc_blocks);
+
+      xor_buf(&buffer[0], &offsets[0], proc_bytes);
+
+      xor_buf(&csum_accum[0], &buffer[0], proc_bytes);
+
+      buffer += proc_bytes;
+      blocks_left -= proc_blocks;
+      }
+
+   // fold into checksum
+   for(size_t i = 0; i != csum_accum.size(); ++i)
+      m_checksum[i % BS] ^= csum_accum[i];
+   }
+
+void OCB_Decryption::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];
+
+   BOTAN_ASSERT(sz % BS == 0, "Input length is an even number of blocks");
+
+   decrypt(buf, sz / BS);
+   }
+
+void OCB_Decryption::finish(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];
+
+   BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
+
+   const size_t remaining = sz - tag_size();
+
+   if(remaining)
+      {
+      const size_t final_full_blocks = remaining / BS;
+      const size_t final_bytes = remaining - (final_full_blocks * BS);
+
+      decrypt(&buf[0], final_full_blocks);
+
+      if(final_bytes)
+         {
+         BOTAN_ASSERT(final_bytes < BS, "Only a partial block left");
+
+         byte* remainder = &buf[remaining - final_bytes];
+
+         m_offset ^= m_L->star(); // Offset_*
+
+         secure_vector<byte> pad(BS);
+         m_cipher->encrypt(m_offset, pad); // P_*
+
+         xor_buf(&remainder[0], &pad[0], final_bytes);
+
+         xor_buf(&m_checksum[0], &remainder[0], final_bytes);
+         m_checksum[final_bytes] ^= 0x80;
+         }
+      }
+
+   // compute the mac
+   secure_vector<byte> mac = m_offset;
+   mac ^= m_checksum;
+   mac ^= m_L->dollar();
+
+   m_cipher->encrypt(mac);
+
+   mac ^= m_ad_hash;
+
+   // reset state
+   zeroise(m_checksum);
+   zeroise(m_offset);
+   m_block_index = 0;
+
+   // compare mac
+   const byte* included_tag = &buf[remaining];
+
+   if(!same_mem(&mac[0], included_tag, tag_size()))
+      throw Integrity_Failure("OCB tag check failed");
+
+   // remove tag from end of message
+   buffer.resize(remaining + offset);
+   }
+
+}