1 files changed, 63 insertions, 0 deletions
diff --git a/src/tls_prf.cpp b/src/tls_prf.cpp
new file mode 100644
index 000000000..2222e3baa
--- /dev/null
+++ b/src/tls_prf.cpp
@@ -0,0 +1,63 @@
+/*************************************************
+* TLS PRF Source File                            *
+* (C) 2004-2006 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/kdf.h>
+#include <botan/lookup.h>
+#include <botan/xor_buf.h>
+#include <botan/hmac.h>
+
+namespace Botan {
+
+/*************************************************
+* TLS PRF                                        *
+*************************************************/
+SecureVector<byte> TLS_PRF::derive(u32bit key_len,
+                                   const byte secret[], u32bit secret_len,
+                                   const byte seed[], u32bit seed_len) const
+   {
+   u32bit S1_len = (secret_len + 1) / 2,
+          S2_len = (secret_len + 1) / 2;
+   const byte* S1 = secret;
+   const byte* S2 = secret + (secret_len - S2_len);
+
+   SecureVector<byte> key1, key2;
+   key1 = P_hash("MD5",   key_len, S1, S1_len, seed, seed_len);
+   key2 = P_hash("SHA-1", key_len, S2, S2_len, seed, seed_len);
+
+   xor_buf(key1.begin(), key2.begin(), key2.size());
+
+   return key1;
+   }
+
+/*************************************************
+* TLS PRF P_hash function                        *
+*************************************************/
+SecureVector<byte> TLS_PRF::P_hash(const std::string& hash, u32bit len,
+                                   const byte secret[], u32bit secret_len,
+                                   const byte seed[], u32bit seed_len) const
+   {
+   SecureVector<byte> out;
+
+   HMAC hmac(hash);
+   hmac.set_key(secret, secret_len);
+
+   SecureVector<byte> A(seed, seed_len);
+   while(len)
+      {
+      const u32bit this_block_len = std::min(hmac.OUTPUT_LENGTH, len);
+
+      A = hmac.process(A);
+
+      hmac.update(A);
+      hmac.update(seed, seed_len);
+      SecureVector<byte> block = hmac.final();
+
+      out.append(block, this_block_len);
+      len -= this_block_len;
+      }
+   return out;
+   }
+
+}