Allow tag sizes other than 128 bits in GCM and OCB

2 files changed, 42 insertions, 34 deletions

diff --git a/src/aead/ocb/ocb.cpp b/src/aead/ocb/ocb.cpp
index 50b33960f..df9d37fa2 100644
--- a/src/aead/ocb/ocb.cpp
+++ b/src/aead/ocb/ocb.cpp
@@ -313,7 +313,7 @@ void OCB_Encryption::finish(secure_vector<byte>& buffer)
 
    mac ^= m_ad_hash;
 
-   buffer += mac;
+   buffer += std::pair(&mac[0], tag_size());
 
    zeroise(m_checksum);
    zeroise(m_offset);
diff --git a/src/engine/core_engine/core_modes.cpp b/src/engine/core_engine/core_modes.cpp
index 588c5d7a2..199b71838 100644
--- a/src/engine/core_engine/core_modes.cpp
+++ b/src/engine/core_engine/core_modes.cpp
@@ -141,30 +141,6 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
 #endif
       }
 
-#if defined(BOTAN_HAS_AEAD_FILTER)
-
-#if defined(BOTAN_HAS_AEAD_OCB)
-   if(mode == "OCB")
-      {
-      if(direction == ENCRYPTION)
-         return new AEAD_Filter(new OCB_Encryption(block_cipher->clone(), 16));
-      else
-         return new AEAD_Filter(new OCB_Decryption(block_cipher->clone(), 16));
-      }
-#endif
-
-#if defined(BOTAN_HAS_AEAD_GCM)
-   if(mode == "GCM")
-      {
-      if(direction == ENCRYPTION)
-         return new AEAD_Filter(new GCM_Encryption(block_cipher->clone(), 16));
-      else
-         return new AEAD_Filter(new GCM_Decryption(block_cipher->clone(), 16));
-      }
-#endif
-
-#endif
-
 #if defined(BOTAN_HAS_XTS)
    if(mode == "XTS")
       {
@@ -176,7 +152,9 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
 #endif
 
    if(mode.find("CFB") != std::string::npos ||
-      mode.find("EAX") != std::string::npos)
+      mode.find("EAX") != std::string::npos ||
+      mode.find("GCM") != std::string::npos ||
+      mode.find("OCB") != std::string::npos)
       {
       std::vector<std::string> algo_info = parse_algorithm_name(mode);
       const std::string mode_name = algo_info[0];
@@ -189,25 +167,55 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
       else
          return nullptr;
 
-#if defined(BOTAN_HAS_CFB)
-      if(mode_name == "CFB")
+#if defined(BOTAN_HAS_AEAD_FILTER)
+
+      if(bits % 8 != 0)
+         throw std::invalid_argument("AEAD interface does not support non-octet length tags");
+
+      const size_t tag_size = bits / 8;
+
+#if defined(BOTAN_HAS_AEAD_EAX)
+      if(mode_name == "EAX")
          {
          if(direction == ENCRYPTION)
-            return new CFB_Encryption(block_cipher->clone(), bits);
+            return new AEAD_Filter(new EAX_Encryption(block_cipher->clone(), tag_size));
          else
-            return new CFB_Decryption(block_cipher->clone(), bits);
+            return new AEAD_Filter(new EAX_Decryption(block_cipher->clone(), tag_size));
          }
 #endif
 
-#if defined(BOTAN_HAS_AEAD_EAX)
-      if(mode_name == "EAX")
+#if defined(BOTAN_HAS_AEAD_OCB)
+   if(mode == "OCB")
+      {
+      if(direction == ENCRYPTION)
+         return new AEAD_Filter(new OCB_Encryption(block_cipher->clone(), tag_size));
+      else
+         return new AEAD_Filter(new OCB_Decryption(block_cipher->clone(), tag_size));
+      }
+#endif
+
+#if defined(BOTAN_HAS_AEAD_GCM)
+   if(mode == "GCM")
+      {
+      if(direction == ENCRYPTION)
+         return new AEAD_Filter(new GCM_Encryption(block_cipher->clone(), tag_size));
+      else
+         return new AEAD_Filter(new GCM_Decryption(block_cipher->clone(), tag_size));
+      }
+#endif
+
+#endif
+
+#if defined(BOTAN_HAS_CFB)
+      if(mode_name == "CFB")
          {
          if(direction == ENCRYPTION)
-            return new AEAD_Filter(new EAX_Encryption(block_cipher->clone(), bits / 8));
+            return new CFB_Encryption(block_cipher->clone(), bits);
          else
-            return new AEAD_Filter(new EAX_Decryption(block_cipher->clone(), bits / 8));
+            return new CFB_Decryption(block_cipher->clone(), bits);
          }
 #endif
+
       }
 
    return nullptr;