Add Tweakable_Block_Cipher class

3 files changed, 28 insertions, 14 deletions

diff --git a/src/lib/block/block_cipher.h b/src/lib/block/block_cipher.h
index 939382fc0..5d490ae49 100644
--- a/src/lib/block/block_cipher.h
+++ b/src/lib/block/block_cipher.h
@@ -198,10 +198,26 @@ class BOTAN_PUBLIC_API(2,0) BlockCipher : public SymmetricAlgorithm
    };
 
 /**
+* Tweakable block ciphers allow setting a tweak which is a non-keyed
+* value which affects the encryption/decryption operation.
+*/
+class BOTAN_PUBLIC_API(2,8) Tweakable_Block_Cipher : public BlockCipher
+   {
+   public:
+      /**
+      * Set the tweak value. This must be called after setting a key. The value
+      * persists until either set_tweak, set_key, or clear is called.
+      * Different algorithms support different tweak length(s). If called with
+      * an unsupported length, Invalid_Argument will be thrown.
+      */
+      virtual void set_tweak(const uint8_t tweak[], size_t len) = 0;
+   };
+
+/**
 * Represents a block cipher with a single fixed block size
 */
-template<size_t BS, size_t KMIN, size_t KMAX = 0, size_t KMOD = 1>
-class Block_Cipher_Fixed_Params : public BlockCipher
+template<size_t BS, size_t KMIN, size_t KMAX = 0, size_t KMOD = 1, typename BaseClass = BlockCipher>
+class Block_Cipher_Fixed_Params : public BaseClass
    {
    public:
       enum { BLOCK_SIZE = BS };
@@ -213,7 +229,7 @@ class Block_Cipher_Fixed_Params : public BlockCipher
                          size_t blocks) const final override
          {
          xor_buf(data, mask, blocks * BS);
-         encrypt_n(data, data, blocks);
+         this->encrypt_n(data, data, blocks);
          xor_buf(data, mask, blocks * BS);
          }
 
@@ -222,7 +238,7 @@ class Block_Cipher_Fixed_Params : public BlockCipher
                          size_t blocks) const final override
          {
          xor_buf(data, mask, blocks * BS);
-         decrypt_n(data, data, blocks);
+         this->decrypt_n(data, data, blocks);
          xor_buf(data, mask, blocks * BS);
          }
 
diff --git a/src/lib/block/threefish_512/threefish_512.h b/src/lib/block/threefish_512/threefish_512.h
index 8b39c75c5..2e936b25f 100644
--- a/src/lib/block/threefish_512/threefish_512.h
+++ b/src/lib/block/threefish_512/threefish_512.h
@@ -15,13 +15,14 @@ namespace Botan {
 /**
 * Threefish-512
 */
-class BOTAN_PUBLIC_API(2,0) Threefish_512 final : public Block_Cipher_Fixed_Params<64, 64>
+class BOTAN_PUBLIC_API(2,0) Threefish_512 final :
+   public Block_Cipher_Fixed_Params<64, 64, 0, 1, Tweakable_Block_Cipher>
    {
    public:
       void encrypt_n(const uint8_t in[], uint8_t out[], size_t blocks) const override;
       void decrypt_n(const uint8_t in[], uint8_t out[], size_t blocks) const override;
 
-      void set_tweak(const uint8_t tweak[], size_t len);
+      void set_tweak(const uint8_t tweak[], size_t len) override;
 
       void clear() override;
       std::string provider() const override;
diff --git a/src/tests/test_block.cpp b/src/tests/test_block.cpp
index 7a5c8492b..66ef9e24b 100644
--- a/src/tests/test_block.cpp
+++ b/src/tests/test_block.cpp
@@ -10,10 +10,6 @@
 
 #include <botan/block_cipher.h>
 
-#if defined(BOTAN_HAS_THREEFISH_512)
-  #include <botan/threefish_512.h>
-#endif
-
 namespace Botan_Tests {
 
 class Block_Cipher_Tests final : public Text_Based_Test
@@ -94,10 +90,11 @@ class Block_Cipher_Tests final : public Text_Based_Test
 
             if(tweak.size() > 0)
                {
-               Botan::Threefish_512* t512 = dynamic_cast<Botan::Threefish_512*>(cipher.get());
-               result.confirm("Only Threefish supports tweaks", t512);
-               if(t512)
-                  t512->set_tweak(tweak.data(), tweak.size());
+               Botan::Tweakable_Block_Cipher* tbc = dynamic_cast<Botan::Tweakable_Block_Cipher*>(cipher.get());
+               if(tbc == nullptr)
+                  result.test_failure("Tweak set in test data but cipher is not a Tweakable_Block_Cipher");
+               else
+                  tbc->set_tweak(tweak.data(), tweak.size());
                }
 
             // Test that clone works and does not affect parent object