1 files changed, 109 insertions, 0 deletions
diff --git a/src/modes/aead/gcm/gcm.h b/src/modes/aead/gcm/gcm.h
new file mode 100644
index 000000000..e1479c27f
--- /dev/null
+++ b/src/modes/aead/gcm/gcm.h
@@ -0,0 +1,109 @@
+/*
+* GCM Mode
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_AEAD_GCM_H__
+#define BOTAN_AEAD_GCM_H__
+
+#include <botan/aead.h>
+#include <botan/block_cipher.h>
+#include <botan/stream_cipher.h>
+#include <memory>
+
+namespace Botan {
+
+/**
+* GCM Mode
+*/
+class BOTAN_DLL GCM_Mode : public AEAD_Mode
+   {
+   public:
+      secure_vector<byte> start(const byte nonce[], size_t nonce_len) override;
+
+      void set_associated_data(const byte ad[], size_t ad_len) override;
+
+      std::string name() const override;
+
+      size_t update_granularity() const;
+
+      Key_Length_Specification key_spec() const override;
+
+      // GCM supports arbitrary nonce lengths
+      bool valid_nonce_length(size_t) const override { return true; }
+
+      void clear();
+   protected:
+      void key_schedule(const byte key[], size_t length) override;
+
+      GCM_Mode(BlockCipher* cipher, size_t tag_size);
+
+      size_t tag_size() const { return m_tag_size; }
+
+      static const size_t BS = 16;
+
+      const size_t m_tag_size;
+      const std::string m_cipher_name;
+
+      std::unique_ptr<StreamCipher> m_ctr;
+      secure_vector<byte> m_H;
+      secure_vector<byte> m_H_ad;
+      secure_vector<byte> m_mac;
+      secure_vector<byte> m_enc_y0;
+      size_t m_ad_len, m_text_len;
+   };
+
+/**
+* GCM Encryption
+*/
+class BOTAN_DLL GCM_Encryption : public GCM_Mode
+   {
+   public:
+      /**
+      * @param cipher the 128 bit block cipher to use
+      * @param tag_size is how big the auth tag will be
+      */
+      GCM_Encryption(BlockCipher* cipher, size_t tag_size = 16) :
+         GCM_Mode(cipher, tag_size) {}
+
+      size_t output_length(size_t input_length) const override
+         { return input_length + tag_size(); }
+
+      size_t minimum_final_size() const override { return 0; }
+
+      void update(secure_vector<byte>& blocks, size_t offset) override;
+
+      void finish(secure_vector<byte>& final_block, size_t offset) override;
+   };
+
+/**
+* GCM Decryption
+*/
+class BOTAN_DLL GCM_Decryption : public GCM_Mode
+   {
+   public:
+      /**
+      * @param cipher the 128 bit block cipher to use
+      * @param tag_size is how big the auth tag will be
+      */
+      GCM_Decryption(BlockCipher* cipher, size_t tag_size = 16) :
+         GCM_Mode(cipher, tag_size) {}
+
+      size_t output_length(size_t input_length) const override
+         {
+         BOTAN_ASSERT(input_length > tag_size(), "Sufficient input");
+         return input_length - tag_size();
+         }
+
+      size_t minimum_final_size() const override { return tag_size(); }
+
+      void update(secure_vector<byte>& blocks, size_t offset) override;
+
+      void finish(secure_vector<byte>& final_block, size_t offset) override;
+   };
+
+}
+
+#endif