Merge GH #1839 Add TLS asio stream wrapper

7 files changed, 1255 insertions, 0 deletions

diff --git a/src/lib/tls/asio/asio_async_ops.h b/src/lib/tls/asio/asio_async_ops.h
new file mode 100644
index 000000000..34d9ce0dd
--- /dev/null
+++ b/src/lib/tls/asio/asio_async_ops.h
@@ -0,0 +1,368 @@
+/*
+* Helpers for TLS ASIO Stream
+* (C) 2018-2019 Jack Lloyd
+*     2018-2019 Hannes Rantzsch, Tim Oesterreich, Rene Meusel
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_ASIO_ASYNC_OPS_H_
+#define BOTAN_ASIO_ASYNC_OPS_H_
+
+#include <botan/build.h>
+
+#include <boost/version.hpp>
+#if BOOST_VERSION >= 106600
+
+#include <botan/asio_error.h>
+
+// We need to define BOOST_ASIO_DISABLE_SERIAL_PORT before any asio imports. Otherwise asio will include <termios.h>,
+// which interferes with Botan's amalgamation by defining macros like 'B0' and 'FF1'.
+#define BOOST_ASIO_DISABLE_SERIAL_PORT
+#include <boost/asio.hpp>
+#include <boost/asio/yield.hpp>
+
+namespace Botan {
+namespace TLS {
+namespace detail {
+
+/**
+ * Base class for asynchronous stream operations.
+ *
+ * Asynchronous operations, used for example to implement an interface for boost::asio::async_read_some and
+ * boost::asio::async_write_some, are based on boost::asio::coroutines.
+ * Derived operations should implement a call operator and invoke it with the correct parameters upon construction. The
+ * call operator needs to make sure that the user-provided handler is not called directly. Typically, yield / reenter is
+ * used for this in the following fashion:
+ *
+ * ```
+ * void operator()(boost::system::error_code ec, std::size_t bytes_transferred, bool isContinuation = true)
+ *    {
+ *    reenter(this)
+ *       {
+ *       // operation specific logic, repeatedly interacting with the stream_core and the next_layer (socket)
+ *
+ *       // make sure intermediate initiating function is called
+ *       if(!isContinuation)
+ *          {
+ *          yield next_layer.async_operation(empty_buffer, this);
+ *          }
+ *
+ *       // call the completion handler
+ *       complete_now(error_code, bytes_transferred);
+ *       }
+ *    }
+ * ```
+ *
+ * Once the operation is completed and ready to call the completion handler it checks if an intermediate initiating
+ * function has been called using the `isContinuation` parameter. If not, it will call an asynchronous operation, such
+ * as `async_read_some`, with and empty buffer, set the object itself as the handler, and `yield`. As a result, the call
+ * operator will be invoked again, this time as a continuation, and will jump to the location where it yielded before
+ * using `reenter`. It is now safe to call the handler function via `complete_now`.
+ *
+ * \tparam Handler Type of the completion handler
+ * \tparam Executor1 Type of the asio executor (usually derived from the lower layer)
+ * \tparam Allocator Type of the allocator to be used
+ */
+template <class Handler, class Executor1, class Allocator>
+class AsyncBase : public boost::asio::coroutine
+   {
+   public:
+      using allocator_type = boost::asio::associated_allocator_t<Handler, Allocator>;
+      using executor_type = boost::asio::associated_executor_t<Handler, Executor1>;
+
+      allocator_type get_allocator() const noexcept
+         {
+         return boost::asio::get_associated_allocator(m_handler);
+         }
+
+      executor_type get_executor() const noexcept
+         {
+         return boost::asio::get_associated_executor(m_handler, m_work_guard_1.get_executor());
+         }
+
+   protected:
+      template <class HandlerT>
+      AsyncBase(HandlerT&& handler, const Executor1& executor)
+         : m_handler(std::forward<HandlerT>(handler))
+         , m_work_guard_1(executor)
+         {
+         }
+
+      /**
+       * Call the completion handler.
+       *
+       * This function should only be called after an intermediate initiating function has been called.
+       *
+       * @param args Arguments forwarded to the completion handler function.
+       */
+      template<class... Args>
+      void complete_now(Args&& ... args)
+         {
+         m_work_guard_1.reset();
+         m_handler(std::forward<Args>(args)...);
+         }
+
+      Handler m_handler;
+      boost::asio::executor_work_guard<Executor1> m_work_guard_1;
+   };
+
+template <class Handler, class Stream, class MutableBufferSequence, class Allocator = std::allocator<void>>
+class AsyncReadOperation : public AsyncBase<Handler, typename Stream::executor_type, Allocator>
+   {
+   public:
+      /**
+       * Construct and invoke an AsyncWriteOperation.
+       *
+       * @param handler Handler function to be called upon completion.
+       * @param stream The stream from which the data will be read
+       * @param buffers The buffers into which the data will be read.
+       * @param ec Optional error code; used to report an error to the handler function.
+       */
+      template <class HandlerT>
+      AsyncReadOperation(HandlerT&& handler,
+                         Stream& stream,
+                         const MutableBufferSequence& buffers,
+                         const boost::system::error_code& ec = {})
+         : AsyncBase<Handler, typename Stream::executor_type, Allocator>(
+              std::forward<HandlerT>(handler),
+              stream.get_executor())
+         , m_stream(stream)
+         , m_buffers(buffers)
+         , m_decodedBytes(0)
+         {
+         this->operator()(ec, std::size_t(0), false);
+         }
+
+      AsyncReadOperation(AsyncReadOperation&&) = default;
+
+      void operator()(boost::system::error_code ec, std::size_t bytes_transferred, bool isContinuation = true)
+         {
+         reenter(this)
+            {
+            if(bytes_transferred > 0 && !ec)
+               {
+               // We have received encrypted data from the network, now hand it to TLS::Channel for decryption.
+               boost::asio::const_buffer read_buffer{m_stream.input_buffer().data(), bytes_transferred};
+               try
+                  {
+                  m_stream.native_handle()->received_data(
+                     static_cast<const uint8_t*>(read_buffer.data()), read_buffer.size()
+                  );
+                  }
+               catch(const TLS_Exception& e)
+                  {
+                  ec = e.type();
+                  }
+               catch(const Botan::Exception& e)
+                  {
+                  ec = e.error_type();
+                  }
+               catch(...)
+                  {
+                  ec = Botan::ErrorType::Unknown;
+                  }
+               }
+
+            if(!m_stream.has_received_data() && !ec && boost::asio::buffer_size(m_buffers) > 0)
+               {
+               // The channel did not decrypt a complete record yet, we need more data from the socket.
+               m_stream.next_layer().async_read_some(m_stream.input_buffer(), std::move(*this));
+               return;
+               }
+
+            if(m_stream.has_received_data() && !ec)
+               {
+               // The channel has decrypted a TLS record, now copy it to the output buffers.
+               m_decodedBytes = m_stream.copy_received_data(m_buffers);
+               }
+
+            if(!isContinuation)
+               {
+               // Make sure the handler is not called without an intermediate initiating function.
+               // "Reading" into a zero-byte buffer will complete immediately.
+               m_ec = ec;
+               yield m_stream.next_layer().async_read_some(boost::asio::mutable_buffer(), std::move(*this));
+               ec = m_ec;
+               }
+
+            this->complete_now(ec, m_decodedBytes);
+            }
+         }
+
+   private:
+      Stream&                   m_stream;
+      MutableBufferSequence     m_buffers;
+      std::size_t               m_decodedBytes;
+      boost::system::error_code m_ec;
+   };
+
+template <typename Handler, class Stream, class Allocator = std::allocator<void>>
+class AsyncWriteOperation : public AsyncBase<Handler, typename Stream::executor_type, Allocator>
+   {
+   public:
+      /**
+       * Construct and invoke an AsyncWriteOperation.
+       *
+       * @param handler Handler function to be called upon completion.
+       * @param stream The stream from which the data will be read
+       * @param plainBytesTransferred Number of bytes to be reported to the user-provided handler function as
+       *                              bytes_transferred. This needs to be provided since the amount of plaintext data
+       *                              consumed from the input buffer can differ from the amount of encrypted data written
+       *                              to the next layer.
+       * @param ec Optional error code; used to report an error to the handler function.
+       */
+      template <class HandlerT>
+      AsyncWriteOperation(HandlerT&& handler,
+                          Stream& stream,
+                          std::size_t plainBytesTransferred,
+                          const boost::system::error_code& ec = {})
+         : AsyncBase<Handler, typename Stream::executor_type, Allocator>(
+              std::forward<HandlerT>(handler),
+              stream.get_executor())
+         , m_stream(stream)
+         , m_plainBytesTransferred(plainBytesTransferred)
+         {
+         this->operator()(ec, std::size_t(0), false);
+         }
+
+      AsyncWriteOperation(AsyncWriteOperation&&) = default;
+
+      void operator()(boost::system::error_code ec, std::size_t bytes_transferred, bool isContinuation = true)
+         {
+         reenter(this)
+            {
+            // mark the number of encrypted bytes sent to the network as "consumed"
+            // Note: bytes_transferred will be zero on first call
+            m_stream.consume_send_buffer(bytes_transferred);
+
+            if(m_stream.has_data_to_send() && !ec)
+               {
+               m_stream.next_layer().async_write_some(m_stream.send_buffer(), std::move(*this));
+               return;
+               }
+
+            if(!isContinuation)
+               {
+               // Make sure the handler is not called without an intermediate initiating function.
+               // "Writing" to a zero-byte buffer will complete immediately.
+               m_ec = ec;
+               yield m_stream.next_layer().async_write_some(boost::asio::const_buffer(), std::move(*this));
+               ec = m_ec;
+               }
+
+            // The size of the sent TLS record can differ from the size of the payload due to TLS encryption. We need to
+            // tell the handler how many bytes of the original data we already processed.
+            this->complete_now(ec, m_plainBytesTransferred);
+            }
+         }
+
+   private:
+      Stream&                   m_stream;
+      std::size_t               m_plainBytesTransferred;
+      boost::system::error_code m_ec;
+   };
+
+template <class Handler, class Stream, class Allocator = std::allocator<void>>
+class AsyncHandshakeOperation : public AsyncBase<Handler, typename Stream::executor_type, Allocator>
+   {
+   public:
+      /**
+       * Construct and invoke an AsyncHandshakeOperation.
+       *
+       * @param handler Handler function to be called upon completion.
+       * @param stream The stream from which the data will be read
+       * @param ec Optional error code; used to report an error to the handler function.
+       */
+      template<class HandlerT>
+      AsyncHandshakeOperation(
+         HandlerT&& handler,
+         Stream& stream,
+         const boost::system::error_code& ec = {})
+         : AsyncBase<Handler, typename Stream::executor_type, Allocator>(
+              std::forward<HandlerT>(handler),
+              stream.get_executor())
+         , m_stream(stream)
+         {
+         this->operator()(ec, std::size_t(0), false);
+         }
+
+      AsyncHandshakeOperation(AsyncHandshakeOperation&&) = default;
+
+      void operator()(boost::system::error_code ec, std::size_t bytesTransferred, bool isContinuation = true)
+         {
+         reenter(this)
+            {
+            if(bytesTransferred > 0 && !ec)
+               {
+               // Provide encrypted TLS data received from the network to TLS::Channel for decryption
+               boost::asio::const_buffer read_buffer {m_stream.input_buffer().data(), bytesTransferred};
+               try
+                  {
+                  m_stream.native_handle()->received_data(
+                     static_cast<const uint8_t*>(read_buffer.data()), read_buffer.size()
+                  );
+                  }
+               catch(const TLS_Exception& e)
+                  {
+                  ec = e.type();
+                  }
+               catch(const Botan::Exception& e)
+                  {
+                  ec = e.error_type();
+                  }
+               catch(...)
+                  {
+                  ec = Botan::ErrorType::Unknown;
+                  }
+               }
+
+            if(m_stream.has_data_to_send() && !ec)
+               {
+               // Write encrypted TLS data provided by the TLS::Channel on the wire
+
+               // Note: we construct `AsyncWriteOperation` with 0 as its last parameter (`plainBytesTransferred`). This
+               // operation will eventually call `*this` as its own handler, passing the 0 back to this call operator.
+               // This is necessary because the check of `bytesTransferred > 0` assumes that `bytesTransferred` bytes
+               // were just read and are available in input_buffer for further processing.
+               AsyncWriteOperation<
+               AsyncHandshakeOperation<typename std::decay<Handler>::type, Stream, Allocator>,
+                                       Stream,
+                                       Allocator>
+                                       op{std::move(*this), m_stream, 0};
+               return;
+               }
+
+            if(!m_stream.native_handle()->is_active() && !ec)
+               {
+               // Read more encrypted TLS data from the network
+               m_stream.next_layer().async_read_some(m_stream.input_buffer(), std::move(*this));
+               return;
+               }
+
+            if(!isContinuation)
+               {
+               // Make sure the handler is not called without an intermediate initiating function.
+               // "Reading" into a zero-byte buffer will complete immediately.
+               m_ec = ec;
+               yield m_stream.next_layer().async_read_some(boost::asio::mutable_buffer(), std::move(*this));
+               ec = m_ec;
+               }
+
+            this->complete_now(ec);
+            }
+         }
+
+   private:
+      Stream&                   m_stream;
+      boost::system::error_code m_ec;
+   };
+
+}  // namespace detail
+}  // namespace TLS
+}  // namespace Botan
+
+#include <boost/asio/unyield.hpp>
+
+#endif // BOOST_VERSION
+#endif // BOTAN_ASIO_ASYNC_OPS_H_
diff --git a/src/lib/tls/asio/asio_context.h b/src/lib/tls/asio/asio_context.h
new file mode 100644
index 000000000..7de88ebce
--- /dev/null
+++ b/src/lib/tls/asio/asio_context.h
@@ -0,0 +1,39 @@
+/*
+ * TLS Context
+ * (C) 2018-2019 Jack Lloyd
+ *     2018-2019 Hannes Rantzsch, Tim Oesterreich, Rene Meusel
+ *
+ * Botan is released under the Simplified BSD License (see license.txt)
+ */
+
+#ifndef BOTAN_ASIO_TLS_CONTEXT_H_
+#define BOTAN_ASIO_TLS_CONTEXT_H_
+
+#include <botan/build.h>
+
+#include <boost/version.hpp>
+#if BOOST_VERSION >= 106600
+
+#include <botan/credentials_manager.h>
+#include <botan/rng.h>
+#include <botan/tls_policy.h>
+#include <botan/tls_server_info.h>
+#include <botan/tls_session_manager.h>
+
+namespace Botan {
+namespace TLS {
+
+struct Context
+   {
+   Credentials_Manager*   credentialsManager;
+   RandomNumberGenerator* randomNumberGenerator;
+   Session_Manager*       sessionManager;
+   Policy*                policy;
+   Server_Information     serverInfo;
+   };
+
+}  // namespace TLS
+}  // namespace Botan
+
+#endif  // BOOST_VERSION
+#endif  // BOTAN_ASIO_TLS_CONTEXT_H_
diff --git a/src/lib/tls/asio/asio_error.h b/src/lib/tls/asio/asio_error.h
new file mode 100644
index 000000000..7356ab3d7
--- /dev/null
+++ b/src/lib/tls/asio/asio_error.h
@@ -0,0 +1,98 @@
+/*
+* TLS Stream Errors
+* (C) 2018-2019 Jack Lloyd
+*     2018-2019 Hannes Rantzsch, Tim Oesterreich, Rene Meusel
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_ASIO_ERROR_H_
+#define BOTAN_ASIO_ERROR_H_
+
+#include <botan/build.h>
+
+#include <boost/version.hpp>
+#if BOOST_VERSION >= 106600
+
+#include <boost/system/system_error.hpp>
+
+#include <botan/exceptn.h>
+#include <botan/tls_alert.h>
+#include <botan/tls_exceptn.h>
+
+namespace Botan {
+namespace TLS {
+
+//! @brief An error category for TLS alerts
+struct BotanAlertCategory : boost::system::error_category
+   {
+   const char* name() const noexcept override
+      {
+      return "asio.botan.tls.alert";
+      }
+
+   std::string message(int ev) const override
+      {
+      Botan::TLS::Alert alert(static_cast<Botan::TLS::Alert::Type>(ev));
+      return alert.type_string();
+      }
+   };
+
+inline const BotanAlertCategory& botan_alert_category() noexcept
+   {
+   static BotanAlertCategory category;
+   return category;
+   }
+
+inline boost::system::error_code make_error_code(Botan::TLS::Alert::Type c)
+   {
+   return boost::system::error_code(static_cast<int>(c), Botan::TLS::botan_alert_category());
+   }
+
+}  // namespace TLS
+
+//! @brief An error category for errors from Botan (other than TLS alerts)
+struct BotanErrorCategory : boost::system::error_category
+   {
+   const char* name() const noexcept override
+      {
+      return "asio.botan.tls";
+      }
+
+   std::string message(int ev) const override
+      {
+      return Botan::to_string(static_cast<Botan::ErrorType>(ev));
+      }
+   };
+
+inline const BotanErrorCategory& botan_category() noexcept
+   {
+   static BotanErrorCategory category;
+   return category;
+   }
+
+inline boost::system::error_code make_error_code(Botan::ErrorType e)
+   {
+   return boost::system::error_code(static_cast<int>(e), Botan::botan_category());
+   }
+
+}  // namespace Botan
+
+namespace boost {
+namespace system {
+
+template<> struct is_error_code_enum<Botan::TLS::Alert::Type>
+   {
+   static const bool value = true;
+   };
+
+template<> struct is_error_code_enum<Botan::ErrorType>
+   {
+   static const bool value = true;
+   };
+
+}  // namespace system
+}  // namespace boost
+
+#endif // BOOST_VERSION
+#endif // BOTAN_ASIO_ERROR_H_
diff --git a/src/lib/tls/asio/asio_stream.h b/src/lib/tls/asio/asio_stream.h
new file mode 100644
index 000000000..4449cb14a
--- /dev/null
+++ b/src/lib/tls/asio/asio_stream.h
@@ -0,0 +1,674 @@
+/*
+* TLS ASIO Stream
+* (C) 2018-2019 Jack Lloyd
+*     2018-2019 Hannes Rantzsch, Tim Oesterreich, Rene Meusel
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_ASIO_STREAM_H_
+#define BOTAN_ASIO_STREAM_H_
+
+#include <botan/build.h>
+
+// first version to be compatible with Networking TS (N4656) and boost::beast
+#include <boost/version.hpp>
+#if BOOST_VERSION >= 106600
+
+#include <botan/asio_async_ops.h>
+#include <botan/asio_context.h>
+#include <botan/asio_error.h>
+
+#include <botan/tls_callbacks.h>
+#include <botan/tls_channel.h>
+#include <botan/tls_client.h>
+#include <botan/tls_magic.h>
+
+// We need to define BOOST_ASIO_DISABLE_SERIAL_PORT before any asio imports. Otherwise asio will include <termios.h>,
+// which interferes with Botan's amalgamation by defining macros like 'B0' and 'FF1'.
+#define BOOST_ASIO_DISABLE_SERIAL_PORT
+#include <boost/asio.hpp>
+#include <boost/beast/core/flat_buffer.hpp>
+
+#include <algorithm>
+#include <memory>
+#include <type_traits>
+
+namespace Botan {
+namespace TLS {
+
+/**
+ * @brief boost::asio compatible SSL/TLS stream
+ *
+ * Currently only the TLS::Client specialization is implemented.
+ *
+ * @tparam StreamLayer type of the next layer, usually a network socket
+ * @tparam ChannelT type of the native_handle, defaults to Botan::TLS::Channel, only needed for testing purposes
+ */
+template <class StreamLayer, class ChannelT = Channel>
+class Stream
+   {
+   public:
+      //! \name construction
+      //! @{
+
+      template <typename... Args>
+      explicit Stream(Context& context, Args&& ... args)
+         : m_context(context)
+         , m_nextLayer(std::forward<Args>(args)...)
+         , m_core(m_receive_buffer, m_send_buffer)
+         , m_input_buffer_space(MAX_CIPHERTEXT_SIZE, '\0')
+         , m_input_buffer(m_input_buffer_space.data(), m_input_buffer_space.size())
+         {}
+
+      // overload for boost::asio::ssl::stream compatibility
+      template <typename Arg>
+      explicit Stream(Arg&& arg, Context& context)
+         : m_context(context)
+         , m_nextLayer(std::forward<Arg>(arg))
+         , m_core(m_receive_buffer, m_send_buffer)
+         , m_input_buffer_space(MAX_CIPHERTEXT_SIZE, '\0')
+         , m_input_buffer(m_input_buffer_space.data(), m_input_buffer_space.size())
+         {}
+
+      virtual ~Stream() = default;
+
+      Stream(Stream&& other) = default;
+      Stream& operator=(Stream&& other) = default;
+
+      Stream(const Stream& other) = delete;
+      Stream& operator=(const Stream& other) = delete;
+
+      //! @}
+      //! \name boost::asio accessor methods
+      //! @{
+
+      using next_layer_type = typename std::remove_reference<StreamLayer>::type;
+      using lowest_layer_type = typename next_layer_type::lowest_layer_type;
+      using executor_type = typename next_layer_type::executor_type;
+      using native_handle_type = typename std::add_pointer<ChannelT>::type;
+
+      executor_type get_executor() noexcept { return m_nextLayer.get_executor(); }
+
+      const next_layer_type& next_layer() const { return m_nextLayer; }
+      next_layer_type& next_layer() { return m_nextLayer; }
+
+      lowest_layer_type& lowest_layer() { return m_nextLayer.lowest_layer(); }
+      const lowest_layer_type& lowest_layer() const { return m_nextLayer.lowest_layer(); }
+
+      native_handle_type native_handle() { return m_native_handle.get(); }
+
+      //! @}
+      //! \name configuration and callback setters
+      //! @{
+
+      //! @throws Not_Implemented
+      template<typename VerifyCallback>
+      void set_verify_callback(VerifyCallback callback)
+         {
+         BOTAN_UNUSED(callback);
+         throw Not_Implemented("set_verify_callback is not implemented");
+         }
+
+      /**
+       * Not Implemented.
+       * @param ec Will be set to `Botan::ErrorType::NotImplemented`
+       */
+      template<typename VerifyCallback>
+      void set_verify_callback(VerifyCallback callback,
+                               boost::system::error_code& ec)
+         {
+         BOTAN_UNUSED(callback);
+         ec = Botan::ErrorType::NotImplemented;
+         }
+
+      //! @throws Not_Implemented
+      void set_verify_depth(int depth)
+         {
+         BOTAN_UNUSED(depth);
+         throw Not_Implemented("set_verify_depth is not implemented");
+         }
+
+      /**
+       * Not Implemented.
+       * @param ec Will be set to `Botan::ErrorType::NotImplemented`
+       */
+      void set_verify_depth(int depth,
+                            boost::system::error_code& ec)
+         {
+         BOTAN_UNUSED(depth);
+         ec = Botan::ErrorType::NotImplemented;
+         }
+
+      //! @throws Not_Implemented
+      template <typename verify_mode>
+      void set_verify_mode(verify_mode v)
+         {
+         BOTAN_UNUSED(v);
+         throw Not_Implemented("set_verify_mode is not implemented");
+         }
+
+      /**
+       * Not Implemented.
+       * @param ec Will be set to `Botan::ErrorType::NotImplemented`
+       */
+      template <typename verify_mode>
+      void set_verify_mode(verify_mode v,
+                           boost::system::error_code& ec)
+         {
+         BOTAN_UNUSED(v);
+         ec = Botan::ErrorType::NotImplemented;
+         }
+
+      //! @}
+      //! \name handshake methods
+      //! @{
+
+      /**
+       * @brief Performs SSL handshaking.
+       *
+       * The function call will block until handshaking is complete or an error occurs.
+       *
+       * @param type The type of handshaking to be performed, i.e. as a client or as a server.
+       * @throws boost::system::system_error if error occured, or if the chosen Connection_Side is not available
+       */
+      void handshake(Connection_Side side)
+         {
+         boost::system::error_code ec;
+         handshake(side, ec);
+         boost::asio::detail::throw_error(ec, "handshake");
+         }
+
+      /**
+       * @brief Performs SSL handshaking.
+       *
+       * The function call will block until handshaking is complete or an error occurs.
+       *
+       * @param type The type of handshaking to be performed, i.e. as a client or as a server.
+       * @param ec Set to indicate what error occurred, if any.
+       */
+      void handshake(Connection_Side side, boost::system::error_code& ec)
+         {
+         setup_native_handle(side, ec);
+
+         // send client hello, which was written to the send buffer on client instantiation
+         send_pending_encrypted_data(ec);
+
+         while(!native_handle()->is_active() && !ec)
+            {
+            boost::asio::const_buffer read_buffer{input_buffer().data(), m_nextLayer.read_some(input_buffer(), ec)};
+            if(ec)
+               { return; }
+
+            try
+               {
+               native_handle()->received_data(static_cast<const uint8_t*>(read_buffer.data()), read_buffer.size());
+               }
+            catch(const TLS_Exception& e)
+               {
+               ec = e.type();
+               }
+            catch(const Botan::Exception& e)
+               {
+               ec = e.error_type();
+               }
+            catch(const std::exception&)
+               {
+               ec = Botan::ErrorType::Unknown;
+               }
+
+            send_pending_encrypted_data(ec);
+            }
+         }
+
+      /**
+       * @brief Starts an asynchronous SSL handshake.
+       *
+       * This function call always returns immediately.
+       *
+       * @param type The type of handshaking to be performed, i.e. as a client or as a server.
+       * @param handler The handler to be called when the handshake operation completes.
+       *                The equivalent function signature of the handler must be: void(boost::system::error_code)
+       * @throws Invalid_Argument if Connection_Side could not be validated
+       */
+      template <typename HandshakeHandler>
+      BOOST_ASIO_INITFN_RESULT_TYPE(HandshakeHandler,
+                                    void(boost::system::error_code))
+      async_handshake(Connection_Side side, HandshakeHandler&& handler)
+         {
+         BOOST_ASIO_HANDSHAKE_HANDLER_CHECK(HandshakeHandler, handler) type_check;
+
+         boost::system::error_code ec;
+         setup_native_handle(side, ec);
+         // If ec is set by setup_native_handle, the AsyncHandshakeOperation created below will do nothing but call the
+         // handler with the error_code set appropriately - no need to early return here.
+
+         boost::asio::async_completion<HandshakeHandler, void(boost::system::error_code)> init(handler);
+
+         detail::AsyncHandshakeOperation<typename std::decay<HandshakeHandler>::type, Stream>
+         op{std::move(init.completion_handler), *this, ec};
+
+         return init.result.get();
+         }
+
+      //! @throws Not_Implemented
+      template <typename ConstBufferSequence, typename BufferedHandshakeHandler>
+      BOOST_ASIO_INITFN_RESULT_TYPE(BufferedHandshakeHandler,
+                                    void(boost::system::error_code, std::size_t))
+      async_handshake(Connection_Side side, const ConstBufferSequence& buffers,
+                      BufferedHandshakeHandler&& handler)
+         {
+         BOTAN_UNUSED(side, buffers, handler);
+         BOOST_ASIO_HANDSHAKE_HANDLER_CHECK(BufferedHandshakeHandler, handler) type_check;
+         throw Not_Implemented("buffered async handshake is not implemented");
+         }
+
+      //! @}
+      //! \name shutdown methods
+      //! @{
+
+      /**
+       * @brief Shut down SSL on the stream.
+       *
+       * This function is used to shut down SSL on the stream. The function call will block until SSL has been shut down
+       * or an error occurs. Note that this will not close the lowest layer.
+       *
+       * @param ec Set to indicate what error occured, if any.
+       */
+      void shutdown(boost::system::error_code& ec)
+         {
+         try
+            {
+            native_handle()->close();
+            }
+         catch(const TLS_Exception& e)
+            {
+            ec = e.type();
+            }
+         catch(const Botan::Exception& e)
+            {
+            ec = e.error_type();
+            }
+         catch(const std::exception&)
+            {
+            ec = Botan::ErrorType::Unknown;
+            }
+
+         if(!ec)
+            { send_pending_encrypted_data(ec); }
+         }
+
+      /**
+       * @brief Shut down SSL on the stream.
+       *
+       * This function is used to shut down SSL on the stream. The function call will block until SSL has been shut down
+       * or an error occurs. Note that this will not close the lowest layer.
+       *
+       * @throws boost::system::system_error if error occured
+       */
+      void shutdown()
+         {
+         boost::system::error_code ec;
+         shutdown(ec);
+         boost::asio::detail::throw_error(ec, "shutdown");
+         }
+
+      /**
+       * @brief Asynchronously shut down SSL on the stream.
+       *
+       * This function call always returns immediately.
+       *
+       * @param handler The handler to be called when the handshake operation completes.
+       *                The equivalent function signature of the handler must be: void(boost::system::error_code)
+       */
+      template <typename ShutdownHandler>
+      void async_shutdown(ShutdownHandler&& handler)
+         {
+         BOOST_ASIO_HANDSHAKE_HANDLER_CHECK(ShutdownHandler, handler) type_check;
+         BOTAN_UNUSED(handler);
+         throw Not_Implemented("async shutdown is not implemented");
+         // TODO: Implement a subclass of AsyncBase that calls native_handle()->close() and writes pending data from
+         // the core to the network, e.g. using AsyncWriteOperation.
+         }
+
+      //! @}
+      //! \name I/O methods
+      //! @{
+
+      /**
+       * @brief Read some data from the stream.
+       *
+       * The function call will block until one or more bytes of data has been read successfully, or until an error
+       * occurs.
+       *
+       * @param buffers The buffers into which the data will be read.
+       * @param ec Set to indicate what error occured, if any.
+       * @return The number of bytes read. Returns 0 if an error occurred.
+       */
+      template <typename MutableBufferSequence>
+      std::size_t read_some(const MutableBufferSequence& buffers,
+                            boost::system::error_code& ec)
+         {
+         if(has_received_data())
+            { return copy_received_data(buffers); }
+
+         boost::asio::const_buffer read_buffer{input_buffer().data(), m_nextLayer.read_some(input_buffer(), ec)};
+         if(ec)
+            { return 0; }
+
+         try
+            {
+            native_handle()->received_data(static_cast<const uint8_t*>(read_buffer.data()), read_buffer.size());
+            }
+         catch(const TLS_Exception& e)
+            {
+            ec = e.type();
+            }
+         catch(const Botan::Exception& e)
+            {
+            ec = e.error_type();
+            }
+         catch(const std::exception&)
+            {
+            ec = Botan::ErrorType::Unknown;
+            }
+
+         return !ec ? copy_received_data(buffers) : 0;
+         }
+
+      /**
+       * @brief Read some data from the stream.
+       *
+       * The function call will block until one or more bytes of data has been read successfully, or until an error
+       * occurs.
+       *
+       * @param buffers The buffers into which the data will be read.
+       * @return The number of bytes read. Returns 0 if an error occurred.
+       * @throws boost::system::system_error if error occured
+       */
+      template <typename MutableBufferSequence>
+      std::size_t read_some(const MutableBufferSequence& buffers)
+         {
+         boost::system::error_code ec;
+         auto const n = read_some(buffers, ec);
+         boost::asio::detail::throw_error(ec, "read_some");
+         return n;
+         }
+
+      /**
+       * @brief Write some data to the stream.
+       *
+       * The function call will block until one or more bytes of data has been written successfully, or until an error
+       * occurs.
+       *
+       * @param buffers The data to be written.
+       * @param ec Set to indicate what error occurred, if any.
+       * @return The number of bytes processed from the input buffers.
+       */
+      template <typename ConstBufferSequence>
+      std::size_t write_some(const ConstBufferSequence& buffers,
+                             boost::system::error_code& ec)
+         {
+         tls_encrypt(buffers, ec);
+         send_pending_encrypted_data(ec);
+         return !ec ? boost::asio::buffer_size(buffers) : 0;
+         }
+
+      /**
+       * @brief Write some data to the stream.
+       *
+       * The function call will block until one or more bytes of data has been written successfully, or until an error
+       * occurs.
+       *
+       * @param buffers The data to be written.
+       * @return The number of bytes written.
+       * @throws boost::system::system_error if error occured
+       */
+      template <typename ConstBufferSequence>
+      std::size_t write_some(const ConstBufferSequence& buffers)
+         {
+         boost::system::error_code ec;
+         auto const n = write_some(buffers, ec);
+         boost::asio::detail::throw_error(ec, "write_some");
+         return n;
+         }
+
+      /**
+       * @brief Start an asynchronous write. The function call always returns immediately.
+       *
+       * @param buffers The data to be written.
+       * @param handler The handler to be called when the write operation completes. Copies will be made of the handler
+       *        as required. The equivalent function signature of the handler must be:
+       *        void(boost::system::error_code, std::size_t)
+       */
+      template <typename ConstBufferSequence, typename WriteHandler>
+      BOOST_ASIO_INITFN_RESULT_TYPE(WriteHandler,
+                                    void(boost::system::error_code, std::size_t))
+      async_write_some(const ConstBufferSequence& buffers, WriteHandler&& handler)
+         {
+         BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;
+
+         boost::asio::async_completion<WriteHandler, void(boost::system::error_code, std::size_t)> init(handler);
+
+         boost::system::error_code ec;
+         tls_encrypt(buffers, ec);
+         if(ec)
+            {
+            // we cannot be sure how many bytes were committed here so clear the send_buffer and let the
+            // AsyncWriteOperation call the handler with the error_code set
+            consume_send_buffer(m_send_buffer.size());
+            detail::AsyncWriteOperation<typename std::decay<WriteHandler>::type, Stream>
+            op{std::move(init.completion_handler), *this, std::size_t(0), ec};
+            return init.result.get();
+            }
+
+         detail::AsyncWriteOperation<typename std::decay<WriteHandler>::type, Stream>
+         op{std::move(init.completion_handler), *this, boost::asio::buffer_size(buffers)};
+
+         return init.result.get();
+         }
+
+      /**
+       * @brief Start an asynchronous read. The function call always returns immediately.
+       *
+       * @param buffers The buffers into which the data will be read. Although the buffers object may be copied as
+       *                necessary, ownership of the underlying buffers is retained by the caller, which must guarantee
+       *                that they remain valid until the handler is called.
+       * @param handler The handler to be called when the read operation completes. The equivalent function signature of
+       *                the handler must be:
+       *                void(boost::system::error_code, std::size_t)
+       */
+      template <typename MutableBufferSequence, typename ReadHandler>
+      BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler,
+                                    void(boost::system::error_code, std::size_t))
+      async_read_some(const MutableBufferSequence& buffers, ReadHandler&& handler)
+         {
+         BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
+
+         boost::asio::async_completion<ReadHandler, void(boost::system::error_code, std::size_t)> init(handler);
+
+         detail::AsyncReadOperation<typename std::decay<ReadHandler>::type, Stream, MutableBufferSequence>
+         op{std::move(init.completion_handler), *this, buffers};
+         return init.result.get();
+         }
+
+      //! @}
+
+   protected:
+      template <typename> friend class detail::AsyncWriteOperation;
+      template <typename> friend class detail::AsyncReadOperation;
+      template <typename> friend class detail::AsyncHandshakeOperation;
+
+      /**
+       * @brief Helper class that implements Botan::TLS::Callbacks
+       *
+       * This class is provided to the stream's native_handle (Botan::TLS::Channel) and implements the callback
+       * functions triggered by the native_handle.
+       *
+       * @param receive_buffer reference to the buffer where decrypted data should be placed
+       * @param send_buffer reference to the buffer where encrypted data should be placed
+       */
+      class StreamCore : public Botan::TLS::Callbacks
+         {
+         public:
+            StreamCore(boost::beast::flat_buffer& receive_buffer, boost::beast::flat_buffer& send_buffer)
+               : m_receive_buffer(receive_buffer), m_send_buffer(send_buffer) {}
+
+            virtual ~StreamCore() = default;
+
+            void tls_emit_data(const uint8_t data[], std::size_t size) override
+               {
+               m_send_buffer.commit(
+                  boost::asio::buffer_copy(m_send_buffer.prepare(size), boost::asio::buffer(data, size))
+               );
+               }
+
+            void tls_record_received(uint64_t, const uint8_t data[], std::size_t size) override
+               {
+               m_receive_buffer.commit(
+                  boost::asio::buffer_copy(m_receive_buffer.prepare(size), boost::asio::const_buffer(data, size))
+               );
+               }
+
+            void tls_alert(Botan::TLS::Alert alert) override
+               {
+               BOTAN_UNUSED(alert);
+               }
+
+            std::chrono::milliseconds tls_verify_cert_chain_ocsp_timeout() const override
+               {
+               return std::chrono::milliseconds(1000);
+               }
+
+            bool tls_session_established(const Botan::TLS::Session&) override
+               {
+               // TODO: it should be possible to configure this in the using application (via callback?)
+               return true;
+               }
+
+            boost::beast::flat_buffer& m_receive_buffer;
+            boost::beast::flat_buffer& m_send_buffer;
+         };
+
+      const boost::asio::mutable_buffer& input_buffer() { return m_input_buffer; }
+      boost::asio::const_buffer send_buffer() const { return m_send_buffer.data(); }
+
+      //! @brief Check if decrypted data is available in the receive buffer
+      bool has_received_data() const { return m_receive_buffer.size() > 0; }
+
+      //! @brief Copy decrypted data into the user-provided buffer
+      template <typename MutableBufferSequence>
+      std::size_t copy_received_data(MutableBufferSequence buffers)
+         {
+         // Note: It would be nice to avoid this buffer copy. This could be achieved by equipping the StreamCore with
+         // the user's desired target buffer once a read is started, and reading directly into that buffer in tls_record
+         // received. However, we need to deal with the case that the receive buffer provided by the caller is smaller
+         // than the decrypted record, so this optimization might not be worth the additional complexity.
+         const auto copiedBytes = boost::asio::buffer_copy(buffers, m_receive_buffer.data());
+         m_receive_buffer.consume(copiedBytes);
+         return copiedBytes;
+         }
+
+      //! @brief Check if encrypted data is available in the send buffer
+      bool has_data_to_send() const { return m_send_buffer.size() > 0; }
+
+      //! @brief Mark bytes in the send buffer as consumed, removing them from the buffer
+      void consume_send_buffer(std::size_t bytesConsumed) { m_send_buffer.consume(bytesConsumed); }
+
+      // This is a helper construct to allow mocking the native_handle in test code. It is activated by explicitly
+      // specifying a (mocked) channel type template parameter when constructing the stream and does not attempt to
+      // instantiate the native_handle.
+      // Note: once we have C++17 we can achieve this much more elegantly using constexpr if.
+      template<class T = ChannelT>
+      typename std::enable_if<!std::is_same<Channel, T>::value>::type
+      setup_native_handle(Connection_Side, boost::system::error_code&) {}
+
+      /**
+       * @brief Create the native handle.
+       *
+       * Depending on the desired connection side, this function will create a Botan::TLS::Client or a
+       * Botan::TLS::Server.
+       *
+       * @param side The desired connection side (client or server)
+       * @param ec Set to NotImplemented when side is SERVER - currently only CLIENT is implemented
+       */
+      template<class T = ChannelT>
+      typename std::enable_if<std::is_same<Channel, T>::value>::type
+      setup_native_handle(Connection_Side side, boost::system::error_code& ec)
+         {
+         if(side == CLIENT)
+            {
+            m_native_handle = std::unique_ptr<Client>(new Client(m_core,
+                              *m_context.sessionManager,
+                              *m_context.credentialsManager,
+                              *m_context.policy,
+                              *m_context.randomNumberGenerator,
+                              m_context.serverInfo));
+            }
+         else
+            {
+            // TODO: First steps in order to support the server side of this stream would be to instantiate a
+            // Botan::TLS::Server instance as the stream's native_handle and implement the handshake appropriately.
+            ec = Botan::ErrorType::NotImplemented;
+            }
+         }
+
+      size_t send_pending_encrypted_data(boost::system::error_code& ec)
+         {
+         if(ec)
+            { return 0; }
+
+         auto writtenBytes = boost::asio::write(m_nextLayer, send_buffer(), ec);
+         consume_send_buffer(writtenBytes);
+         return writtenBytes;
+         }
+
+      template <typename ConstBufferSequence>
+      void tls_encrypt(const ConstBufferSequence& buffers, boost::system::error_code& ec)
+         {
+         // NOTE: This is not asynchronous: it encrypts the data synchronously.
+         // The data encrypted by native_handle()->send() is synchronously stored in the send_buffer of m_core,
+         // but is not actually written to the wire, yet.
+         for(auto it = boost::asio::buffer_sequence_begin(buffers);
+               !ec && it != boost::asio::buffer_sequence_end(buffers);
+               it++)
+            {
+            const boost::asio::const_buffer buffer = *it;
+            try
+               {
+               native_handle()->send(static_cast<const uint8_t*>(buffer.data()), buffer.size());
+               }
+            catch(const TLS_Exception& e)
+               {
+               ec = e.type();
+               }
+            catch(const Botan::Exception& e)
+               {
+               ec = e.error_type();
+               }
+            catch(const std::exception&)
+               {
+               ec = Botan::ErrorType::Unknown;
+               }
+            }
+         }
+
+      Context                   m_context;
+      StreamLayer               m_nextLayer;
+
+      boost::beast::flat_buffer m_receive_buffer;
+      boost::beast::flat_buffer m_send_buffer;
+
+      StreamCore                m_core;
+      std::unique_ptr<ChannelT> m_native_handle;
+
+      // Buffer space used to read input intended for the core
+      std::vector<uint8_t>              m_input_buffer_space;
+      const boost::asio::mutable_buffer m_input_buffer;
+   };
+
+}  // namespace TLS
+}  // namespace Botan
+
+#endif // BOOST_VERSION
+#endif // BOTAN_ASIO_STREAM_H_
diff --git a/src/lib/tls/asio/info.txt b/src/lib/tls/asio/info.txt
new file mode 100644
index 000000000..7862a1c28
--- /dev/null
+++ b/src/lib/tls/asio/info.txt
@@ -0,0 +1,15 @@
+<defines>
+TLS_ASIO_STREAM -> 20181218
+</defines>
+
+<header:public>
+asio_context.h
+asio_stream.h
+asio_error.h
+asio_async_ops.h
+</header:public>
+
+<requires>
+boost
+tls
+</requires>
diff --git a/src/lib/utils/exceptn.cpp b/src/lib/utils/exceptn.cpp
index 78365f98b..3876c3b26 100644
--- a/src/lib/utils/exceptn.cpp
+++ b/src/lib/utils/exceptn.cpp
@@ -8,6 +8,64 @@
 
 namespace Botan {
 
+std::string to_string(ErrorType type)
+{
+   switch(type)
+   {
+   case ErrorType::Unknown:
+      return "Unknown";
+   case ErrorType::SystemError:
+      return "SystemError";
+   case ErrorType::NotImplemented:
+      return "NotImplemented";
+   case ErrorType::OutOfMemory:
+      return "OutOfMemory";
+   case ErrorType::InternalError:
+      return "InternalError";
+   case ErrorType::IoError:
+      return "IoError";
+   case ErrorType::InvalidObjectState :
+      return "InvalidObjectState";
+   case ErrorType::KeyNotSet:
+      return "KeyNotSet";
+   case ErrorType::InvalidArgument:
+      return "InvalidArgument";
+   case ErrorType::InvalidKeyLength:
+      return "InvalidKeyLength";
+   case ErrorType::InvalidNonceLength:
+      return "InvalidNonceLength";
+   case ErrorType::LookupError:
+      return "LookupError";
+   case ErrorType::EncodingFailure:
+      return "EncodingFailure";
+   case ErrorType::DecodingFailure:
+      return "DecodingFailure";
+   case ErrorType::TLSError:
+      return "TLSError";
+   case ErrorType::HttpError:
+      return "HttpError";
+   case ErrorType::InvalidTag:
+      return "InvalidTag";
+   case ErrorType::OpenSSLError :
+      return "OpenSSLError";
+   case ErrorType::CommonCryptoError:
+      return "CommonCryptoError";
+   case ErrorType::Pkcs11Error:
+      return "Pkcs11Error";
+   case ErrorType::TPMError:
+      return "TPMError";
+   case ErrorType::ZlibError :
+      return "ZlibError";
+   case ErrorType::Bzip2Error:
+      return "Bzip2Error" ;
+   case ErrorType::LzmaError:
+      return "LzmaError";
+
+   default:
+      return "unrecognized botan error";
+   }
+}
+
 Exception::Exception(const std::string& msg) : m_msg(msg)
    {}
 
diff --git a/src/lib/utils/exceptn.h b/src/lib/utils/exceptn.h
index c4934ed04..0ca888316 100644
--- a/src/lib/utils/exceptn.h
+++ b/src/lib/utils/exceptn.h
@@ -72,6 +72,9 @@ enum class ErrorType {
 
 };
 
+//! \brief Convert an ErrorType to string
+std::string BOTAN_PUBLIC_API(2,11) to_string(ErrorType type);
+
 /**
 * Base class for all exceptions thrown by the library
 */