3 files changed, 51 insertions, 0 deletions
diff --git a/src/tls/tls_channel.cpp b/src/tls/tls_channel.cpp
index 6d90ed47f..cb811278a 100644
--- a/src/tls/tls_channel.cpp
+++ b/src/tls/tls_channel.cpp
@@ -12,6 +12,7 @@
 #include <botan/internal/tls_record.h>
 #include <botan/internal/assert.h>
 #include <botan/internal/rounding.h>
+#include <botan/internal/stl_util.h>
 #include <botan/loadstor.h>
 
 namespace Botan {
@@ -526,6 +527,38 @@ bool Channel::secure_renegotiation_supported() const
    return m_secure_renegotiation;
    }
 
+SymmetricKey Channel::key_material_export(const std::string& label,
+                                          const std::string& context,
+                                          size_t length) const
+   {
+   if(!m_active_state)
+      throw std::runtime_error("Channel::key_material_export connection not active");
+
+   Handshake_State& state = *m_active_state;
+
+   std::unique_ptr<KDF> prf(state.protocol_specific_prf());
+
+   const secure_vector<byte>& master_secret =
+      state.session_keys().master_secret();
+
+   std::vector<byte> salt;
+   salt += to_byte_vector(label);
+   salt += state.client_hello()->random();
+   salt += state.server_hello()->random();
+
+   if(context != "")
+      {
+      size_t context_size = context.length();
+      if(context_size > 0xFFFF)
+         throw std::runtime_error("key_material_export context is too long");
+      salt.push_back(get_byte<u16bit>(0, context_size));
+      salt.push_back(get_byte<u16bit>(1, context_size));
+      salt += to_byte_vector(context);
+      }
+
+   return prf->derive_key(length, master_secret, salt);
+   }
+
 }
 
 }
diff --git a/src/tls/tls_channel.h b/src/tls/tls_channel.h
index 1ea6b06eb..8b495fcd4 100644
--- a/src/tls/tls_channel.h
+++ b/src/tls/tls_channel.h
@@ -85,6 +85,17 @@ class BOTAN_DLL Channel
       */
       std::vector<X509_Certificate> peer_cert_chain() const;
 
+      /**
+      * Key material export (RFC 5705)
+      * @param label a disambiguating label string
+      * @param context a per-association context value
+      * @param length the length of the desired key in bytes
+      * @return key of length bytes
+      */
+      SymmetricKey key_material_export(const std::string& label,
+                                       const std::string& context,
+                                       size_t length) const;
+
       Channel(std::function<void (const byte[], size_t)> socket_output_fn,
               std::function<void (const byte[], size_t, Alert)> proc_fn,
               std::function<bool (const Session&)> handshake_complete,
diff --git a/src/utils/stl_util.h b/src/utils/stl_util.h
index 1a62e8fe7..690d2af01 100644
--- a/src/utils/stl_util.h
+++ b/src/utils/stl_util.h
@@ -9,10 +9,17 @@
 #define BOTAN_STL_UTIL_H__
 
 #include <vector>
+#include <string>
 #include <map>
 
 namespace Botan {
 
+std::vector<byte> to_byte_vector(const std::string& s)
+   {
+   return std::vector<byte>(reinterpret_cast<const byte*>(&s[0]),
+                            reinterpret_cast<const byte*>(&s[s.size()]));
+   }
+
 /*
 * Searching through a std::map
 * @param mapping the map to search