1 files changed, 103 insertions, 0 deletions
diff --git a/src/lib/rng/hmac_drbg/hmac_drbg.cpp b/src/lib/rng/hmac_drbg/hmac_drbg.cpp
new file mode 100644
index 000000000..3227841f0
--- /dev/null
+++ b/src/lib/rng/hmac_drbg/hmac_drbg.cpp
@@ -0,0 +1,103 @@
+/*
+* HMAC_DRBG
+* (C) 2014 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/hmac_drbg.h>
+#include <algorithm>
+
+namespace Botan {
+
+HMAC_DRBG::HMAC_DRBG(MessageAuthenticationCode* mac,
+                     RandomNumberGenerator* prng) :
+   m_mac(mac),
+   m_prng(prng),
+   m_V(m_mac->output_length(), 0x01),
+   m_reseed_counter(0)
+   {
+   m_mac->set_key(secure_vector<byte>(m_mac->output_length(), 0x00));
+   }
+
+void HMAC_DRBG::randomize(byte out[], size_t length)
+   {
+   if(!is_seeded() || m_reseed_counter > BOTAN_RNG_MAX_OUTPUT_BEFORE_RESEED)
+      reseed(m_mac->output_length() * 8);
+
+   if(!is_seeded())
+      throw PRNG_Unseeded(name());
+
+   while(length)
+      {
+      const size_t to_copy = std::min(length, m_V.size());
+      m_V = m_mac->process(m_V);
+      copy_mem(&out[0], &m_V[0], to_copy);
+
+      length -= to_copy;
+      out += to_copy;
+      }
+
+   update(nullptr, 0); // additional_data is always empty
+   }
+
+/*
+* Reset V and the mac key with new values
+*/
+void HMAC_DRBG::update(const byte input[], size_t input_len)
+   {
+   m_mac->update(m_V);
+   m_mac->update(0x00);
+   m_mac->update(input, input_len);
+   m_mac->set_key(m_mac->final());
+
+   m_V = m_mac->process(m_V);
+
+   if(input_len)
+      {
+      m_mac->update(m_V);
+      m_mac->update(0x01);
+      m_mac->update(input, input_len);
+      m_mac->set_key(m_mac->final());
+
+      m_V = m_mac->process(m_V);
+      }
+   }
+
+void HMAC_DRBG::reseed(size_t poll_bits)
+   {
+   m_prng->reseed(poll_bits);
+
+   if(m_prng->is_seeded())
+      {
+      secure_vector<byte> input = m_prng->random_vec(m_mac->output_length());
+      update(&input[0], input.size());
+      m_reseed_counter = 1;
+      }
+   }
+
+void HMAC_DRBG::add_entropy(const byte input[], size_t length)
+   {
+   // Should we also poll the underlying PRNG here?
+   update(input, length);
+   }
+
+bool HMAC_DRBG::is_seeded() const
+   {
+   return m_reseed_counter > 0;
+   }
+
+void HMAC_DRBG::clear()
+   {
+   m_mac->clear();
+   m_prng->clear();
+   zeroise(m_V);
+   zeroise(m_K);
+   }
+
+std::string HMAC_DRBG::name() const
+   {
+   return "HMAC_DRBG(" + m_mac->name() + ")";
+   }
+
+}