3 files changed, 242 insertions, 0 deletions
diff --git a/lib/modes/cfb/cfb.cpp b/lib/modes/cfb/cfb.cpp
new file mode 100644
index 000000000..7721e1487
--- /dev/null
+++ b/lib/modes/cfb/cfb.cpp
@@ -0,0 +1,150 @@
+/*
+* CFB Mode
+* (C) 1999-2007,2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/cfb.h>
+#include <botan/parsing.h>
+#include <botan/internal/xor_buf.h>
+
+namespace Botan {
+
+CFB_Mode::CFB_Mode(BlockCipher* cipher, size_t feedback_bits) :
+   m_cipher(cipher),
+   m_feedback_bytes(feedback_bits ? feedback_bits / 8 : cipher->block_size())
+   {
+   if(feedback_bits % 8 || feedback() > cipher->block_size())
+      throw std::invalid_argument(name() + ": feedback bits " +
+                                  std::to_string(feedback_bits) + " not supported");
+   }
+
+void CFB_Mode::clear()
+   {
+   m_cipher->clear();
+   m_shift_register.clear();
+   }
+
+std::string CFB_Mode::name() const
+   {
+   if(feedback() == cipher().block_size())
+      return cipher().name() + "/CFB";
+   else
+      return cipher().name() + "/CFB(" + std::to_string(feedback()*8) + ")";
+   }
+
+size_t CFB_Mode::output_length(size_t input_length) const
+   {
+   return input_length;
+   }
+
+size_t CFB_Mode::update_granularity() const
+   {
+   return feedback();
+   }
+
+size_t CFB_Mode::minimum_final_size() const
+   {
+   return 0;
+   }
+
+Key_Length_Specification CFB_Mode::key_spec() const
+   {
+   return cipher().key_spec();
+   }
+
+size_t CFB_Mode::default_nonce_length() const
+   {
+   return cipher().block_size();
+   }
+
+bool CFB_Mode::valid_nonce_length(size_t n) const
+   {
+   return (n == cipher().block_size());
+   }
+
+void CFB_Mode::key_schedule(const byte key[], size_t length)
+   {
+   m_cipher->set_key(key, length);
+   }
+
+secure_vector<byte> CFB_Mode::start(const byte nonce[], size_t nonce_len)
+   {
+   if(!valid_nonce_length(nonce_len))
+      throw Invalid_IV_Length(name(), nonce_len);
+
+   m_shift_register.assign(nonce, nonce + nonce_len);
+   m_keystream_buf.resize(m_shift_register.size());
+   cipher().encrypt(m_shift_register, m_keystream_buf);
+
+   return secure_vector<byte>();
+   }
+
+void CFB_Encryption::update(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const size_t BS = cipher().block_size();
+
+   secure_vector<byte>& state = shift_register();
+   const size_t shift = feedback();
+
+   while(sz)
+      {
+      const size_t took = std::min(shift, sz);
+      xor_buf(&buf[0], &keystream_buf()[0], took);
+
+      // Assumes feedback-sized block except for last input
+      copy_mem(&state[0], &state[shift], BS - shift);
+      copy_mem(&state[BS-shift], &buf[0], shift);
+      cipher().encrypt(state, keystream_buf());
+
+      buf += took;
+      sz -= took;
+      }
+   }
+
+void CFB_Encryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   update(buffer, offset);
+   }
+
+void CFB_Decryption::update(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const size_t BS = cipher().block_size();
+
+   secure_vector<byte>& state = shift_register();
+   const size_t shift = feedback();
+
+   while(sz)
+      {
+      const size_t took = std::min(shift, sz);
+
+      // first update shift register with ciphertext
+      copy_mem(&state[0], &state[shift], BS - shift);
+      copy_mem(&state[BS-shift], &buf[0], took);
+
+      // then decrypt
+      xor_buf(&buf[0], &keystream_buf()[0], took);
+
+      // then update keystream
+      cipher().encrypt(state, keystream_buf());
+
+      buf += took;
+      sz -= took;
+      }
+   }
+
+void CFB_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   update(buffer, offset);
+   }
+
+}
diff --git a/lib/modes/cfb/cfb.h b/lib/modes/cfb/cfb.h
new file mode 100644
index 000000000..48be0a2d9
--- /dev/null
+++ b/lib/modes/cfb/cfb.h
@@ -0,0 +1,91 @@
+/*
+* CFB mode
+* (C) 1999-2007,2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_MODE_CFB_H__
+#define BOTAN_MODE_CFB_H__
+
+#include <botan/cipher_mode.h>
+#include <botan/block_cipher.h>
+#include <botan/mode_pad.h>
+#include <memory>
+
+namespace Botan {
+
+/**
+* CFB Mode
+*/
+class BOTAN_DLL CFB_Mode : public Cipher_Mode
+   {
+   public:
+      secure_vector<byte> start(const byte nonce[], size_t nonce_len) override;
+
+      std::string name() const override;
+
+      size_t update_granularity() const override;
+
+      size_t minimum_final_size() const override;
+
+      Key_Length_Specification key_spec() const override;
+
+      size_t output_length(size_t input_length) const override;
+
+      size_t default_nonce_length() const override;
+
+      bool valid_nonce_length(size_t n) const override;
+
+      void clear();
+   protected:
+      CFB_Mode(BlockCipher* cipher, size_t feedback_bits);
+
+      const BlockCipher& cipher() const { return *m_cipher; }
+
+      size_t feedback() const { return m_feedback_bytes; }
+
+      secure_vector<byte>& shift_register() { return m_shift_register; }
+
+      secure_vector<byte>& keystream_buf() { return m_keystream_buf; }
+
+   private:
+      void key_schedule(const byte key[], size_t length) override;
+
+      std::unique_ptr<BlockCipher> m_cipher;
+      secure_vector<byte> m_shift_register;
+      secure_vector<byte> m_keystream_buf;
+      size_t m_feedback_bytes;
+   };
+
+/**
+* CFB Encryption
+*/
+class BOTAN_DLL CFB_Encryption : public CFB_Mode
+   {
+   public:
+      CFB_Encryption(BlockCipher* cipher, size_t feedback_bits) :
+         CFB_Mode(cipher, feedback_bits) {}
+
+      void update(secure_vector<byte>& blocks, size_t offset = 0) override;
+
+      void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
+   };
+
+/**
+* CFB Decryption
+*/
+class BOTAN_DLL CFB_Decryption : public CFB_Mode
+   {
+   public:
+      CFB_Decryption(BlockCipher* cipher, size_t feedback_bits) :
+         CFB_Mode(cipher, feedback_bits) {}
+
+      void update(secure_vector<byte>& blocks, size_t offset = 0) override;
+
+      void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
+   };
+
+}
+
+#endif
diff --git a/lib/modes/cfb/info.txt b/lib/modes/cfb/info.txt
new file mode 100644
index 000000000..8d0e20a84
--- /dev/null
+++ b/lib/modes/cfb/info.txt
@@ -0,0 +1 @@
+define MODE_CFB 20131128