Convert HKDF to the normal KDF interface

2 files changed, 34 insertions, 59 deletions

diff --git a/src/lib/kdf/hkdf/hkdf.cpp b/src/lib/kdf/hkdf/hkdf.cpp
index 28f97cadb..8c92c779b 100644
--- a/src/lib/kdf/hkdf/hkdf.cpp
+++ b/src/lib/kdf/hkdf/hkdf.cpp
@@ -1,67 +1,51 @@
 /*
 * HKDF
-* (C) 2013 Jack Lloyd
+* (C) 2013,2015 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
 
+#include <botan/internal/kdf_utils.h>
 #include <botan/hkdf.h>
 
 namespace Botan {
 
-std::string HKDF::name() const
-   {
-   const std::string prf = m_prf->name();
-   const std::string ext = m_extractor->name();
-
-   if(prf == ext)
-      return "HKDF(" + prf + ")";
-   return "HKDF(" + ext + "," + prf + ")";
-   }
-
-void HKDF::clear()
-   {
-   m_extractor->clear();
-   m_prf->clear();
-   }
+BOTAN_REGISTER_NAMED_T(KDF, "HKDF", HKDF, HKDF::make);
 
-void HKDF::start_extract(const byte salt[], size_t salt_len)
+HKDF* HKDF::make(const Spec& spec)
    {
-   m_extractor->set_key(salt, salt_len);
-   }
+   if(auto mac = make_a<MessageAuthenticationCode>(spec.arg(0)))
+      return new HKDF(mac);
 
-void HKDF::extract(const byte input[], size_t input_len)
-   {
-   m_extractor->update(input, input_len);
-   }
+   if(auto mac = make_a<MessageAuthenticationCode>("HMAC(" + spec.arg(0) + ")"))
+      return new HKDF(mac);
 
-void HKDF::finish_extract()
-   {
-   m_prf->set_key(m_extractor->final());
+   return nullptr;
    }
 
-void HKDF::expand(byte output[], size_t output_len,
-                  const byte info[], size_t info_len)
+size_t HKDF::kdf(byte out[], size_t out_len,
+                 const byte secret[], size_t secret_len,
+                 const byte salt[], size_t salt_len) const
    {
-   if(output_len > m_prf->output_length() * 255)
-      throw std::invalid_argument("HKDF requested output too large");
+   m_prf->set_key(secret, secret_len);
 
    byte counter = 1;
+   secure_vector<byte> h;
+   size_t offset = 0;
 
-   secure_vector<byte> T;
-
-   while(output_len)
+   while(offset != out_len && counter != 0)
       {
-      m_prf->update(T);
-      m_prf->update(info, info_len);
+      m_prf->update(h);
+      m_prf->update(salt, salt_len);
       m_prf->update(counter++);
-      m_prf->final(T);
+      m_prf->final(h);
 
-      const size_t to_write = std::min(T.size(), output_len);
-      copy_mem(&output[0], &T[0], to_write);
-      output += to_write;
-      output_len -= to_write;
+      const size_t written = std::min(h.size(), out_len - offset);
+      copy_mem(&out[offset], &h[0], written);
+      offset += written;
       }
+
+   return offset;
    }
 
 }
diff --git a/src/lib/kdf/hkdf/hkdf.h b/src/lib/kdf/hkdf/hkdf.h
index f1ae61453..c5737b1cc 100644
--- a/src/lib/kdf/hkdf/hkdf.h
+++ b/src/lib/kdf/hkdf/hkdf.h
@@ -1,6 +1,6 @@
 /*
 * HKDF
-* (C) 2013 Jack Lloyd
+* (C) 2013,2015 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -16,33 +16,24 @@ namespace Botan {
 
 /**
 * HKDF, see @rfc 5869 for details
+* This is only the expansion portion of HKDF
 */
-class BOTAN_DLL HKDF
+class BOTAN_DLL HKDF : public KDF
    {
    public:
-      HKDF(MessageAuthenticationCode* extractor,
-           MessageAuthenticationCode* prf) :
-         m_extractor(extractor), m_prf(prf) {}
+      HKDF(MessageAuthenticationCode* prf) : m_prf(prf) {}
 
-      HKDF(MessageAuthenticationCode* prf) :
-         m_extractor(prf), m_prf(m_extractor->clone()) {}
+      static HKDF* make(const Spec& spec);
 
-      void start_extract(const byte salt[], size_t salt_len);
-      void extract(const byte input[], size_t input_len);
-      void finish_extract();
+      KDF* clone() const { return new HKDF(m_prf->clone()); }
 
-      /**
-      * Only call after extract
-      * @param output_len must be less than 256*hashlen
-      */
-      void expand(byte output[], size_t output_len,
-                  const byte info[], size_t info_len);
+      std::string name() const { return "HKDF(" + m_prf->name() + ")"; }
 
-      std::string name() const;
+      size_t kdf(byte out[], size_t out_len,
+                 const byte secret[], size_t secret_len,
+                 const byte salt[], size_t salt_len) const override;
 
-      void clear();
    private:
-      std::unique_ptr<MessageAuthenticationCode> m_extractor;
       std::unique_ptr<MessageAuthenticationCode> m_prf;
    };