Add ESP block cipher padding from RFC 4303

ESP padding is one of the recommended padding
methods from BSI-TR-02102-1.

2 files changed, 62 insertions, 1 deletions

diff --git a/src/lib/modes/mode_pad/mode_pad.cpp b/src/lib/modes/mode_pad/mode_pad.cpp
index 7b4546c86..6550edef2 100644
--- a/src/lib/modes/mode_pad/mode_pad.cpp
+++ b/src/lib/modes/mode_pad/mode_pad.cpp
@@ -1,6 +1,7 @@
 /*
 * CBC Padding Methods
 * (C) 1999-2007,2013 Jack Lloyd
+* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -27,6 +28,9 @@ BlockCipherModePaddingMethod* get_bc_pad(const std::string& algo_spec)
    if(algo_spec == "X9.23")
       return new ANSI_X923_Padding;
 
+   if(algo_spec == "ESP")
+      return new ESP_Padding;
+
    return nullptr;
    }
 
@@ -121,5 +125,44 @@ size_t OneAndZeros_Padding::unpad(const byte block[], size_t size) const
    return (size-1);
    }
 
+/*
+* Pad with ESP Padding Method
+*/
+void ESP_Padding::add_padding(secure_vector<byte>& buffer,
+                                      size_t last_byte_pos,
+                                      size_t block_size) const
+   {
+   byte pad_value = 0x01;
+
+   for(size_t i = last_byte_pos; i < block_size; ++i)
+      {
+      buffer.push_back(pad_value++);
+      }
+   }
+
+/*
+* Unpad with ESP Padding Method
+*/
+size_t ESP_Padding::unpad(const byte block[], size_t size) const
+   {
+   while(size)
+      {
+      if(block[size-1] == 0x01)
+         {
+         break;
+         }
+      if(block[size-1] == 0x00)
+         {
+         throw Decoding_Error(name());
+         }
+      size--;
+      }
+   if(!size)
+      {
+      throw Decoding_Error(name());
+      }
+   return (size-1);
+   }
+
 
 }
diff --git a/src/lib/modes/mode_pad/mode_pad.h b/src/lib/modes/mode_pad/mode_pad.h
index d52fbd7b6..af528a926 100644
--- a/src/lib/modes/mode_pad/mode_pad.h
+++ b/src/lib/modes/mode_pad/mode_pad.h
@@ -1,6 +1,7 @@
 /*
 * ECB/CBC Padding Methods
 * (C) 1999-2008,2013 Jack Lloyd
+* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -96,7 +97,7 @@ class BOTAN_DLL ANSI_X923_Padding final : public BlockCipherModePaddingMethod
    };
 
 /**
-* One And Zeros Padding
+* One And Zeros Padding (ISO/IEC 7816-4)
 */
 class BOTAN_DLL OneAndZeros_Padding final : public BlockCipherModePaddingMethod
    {
@@ -113,6 +114,23 @@ class BOTAN_DLL OneAndZeros_Padding final : public BlockCipherModePaddingMethod
    };
 
 /**
+* ESP Padding (RFC 4304)
+*/
+class BOTAN_DLL ESP_Padding final : public BlockCipherModePaddingMethod
+   {
+   public:
+      void add_padding(secure_vector<byte>& buffer,
+                       size_t final_block_bytes,
+                       size_t block_size) const override;
+
+      size_t unpad(const byte[], size_t) const override;
+
+      bool valid_blocksize(size_t bs) const override { return (bs > 0); }
+
+      std::string name() const override { return "ESP"; }
+   };
+
+/**
 * Null Padding
 */
 class BOTAN_DLL Null_Padding final : public BlockCipherModePaddingMethod