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diff --git a/src/lib/tls/tls_callbacks.h b/src/lib/tls/tls_callbacks.h
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+++ b/src/lib/tls/tls_callbacks.h
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+/*
+* TLS Callbacks
+* (C) 2016 Matthias Gierlings
+*     2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_TLS_CALLBACKS_H__
+#define BOTAN_TLS_CALLBACKS_H__
+
+#include <botan/tls_session.h>
+#include <botan/tls_alert.h>
+namespace Botan {
+
+namespace TLS {
+
+class Handshake_Message;
+
+/**
+* Encapsulates the callbacks that a TLS channel will make which are due to
+* channel specific operations.
+*/
+class BOTAN_DLL Callbacks
+   {
+   public:
+       virtual ~Callbacks() {}
+
+       /**
+       * Mandatory callback: output function
+       * The channel will call this with data which needs to be sent to the peer
+       * (eg, over a socket or some other form of IPC). The array will be overwritten
+       * when the function returns so a copy must be made if the data cannot be
+       * sent immediately.
+       *
+       * @param data the vector of data to send
+       *
+       * @param size the number of bytes to send
+       */
+       virtual void tls_emit_data(const uint8_t data[], size_t size) = 0;
+
+       /**
+       * Mandatory callback: process application data
+       * Called when application data record is received from the peer.
+       * Again the array is overwritten immediately after the function returns.
+       *
+       * @param seq_no the underlying TLS/DTLS record sequence number
+       *
+       * @param data the vector containing the received record
+       *
+       * @param size the length of the received record, in bytes
+       */
+       virtual void tls_record_received(u64bit seq_no, const uint8_t data[], size_t size) = 0;
+
+       /**
+       * Mandary callback: alert received
+       * Called when an alert is received from the peer
+       * If fatal, the connection is closing. If not fatal, the connection may
+       * still be closing (depending on the error and the peer).
+       *
+       * @param alert the source of the alert
+       */
+       virtual void tls_alert(Alert alert) = 0;
+
+       /**
+       * Mandatory callback: session established
+       * Called when a session is established. Throw an exception to abort
+       * the connection.
+       *
+       * @param session the session descriptor
+       *
+       * @return return false to prevent the session from being cached,
+       * return true to cache the session in the configured session manager
+       */
+       virtual bool tls_session_established(const Session& session) = 0;
+
+       /**
+       * Optional callback: inspect handshake message
+       * Throw an exception to abort the handshake.
+       *
+       * @param message the handshake message
+       */
+       virtual void tls_inspect_handshake_msg(const Handshake_Message& message) {}
+
+       /**
+       * Optional callback for server: choose ALPN protocol
+       * ALPN (RFC 7301) works by the client sending a list of application
+       * protocols it is willing to negotiate. The server then selects which
+       * protocol to use, which is not necessarily even on the list that
+       * the client sent.
+       *
+       * @param client_protos the vector of protocols the client is willing to negotiate
+       *
+       * @return the protocol selected by the server, which need not be on the
+       * list that the client sent; if this is the empty string, the server ignores the
+       * client ALPN extension
+       */
+       virtual std::string tls_server_choose_app_protocol(const std::vector<std::string>& client_protos)
+          {
+          return "";
+          }
+
+       /**
+       * Optional callback: debug logging. (not currently used)
+       */
+       virtual bool tls_log_debug(const char*) { return false; }
+   };
+
+/**
+* TLS::Callbacks using std::function for compatability with the old API signatures.
+* This type is only provided for backward compatibility.
+* New implementations should derive from TLS::Callbacks instead.
+*/
+class BOTAN_DLL Compat_Callbacks final : public Callbacks
+   {
+   public:
+      typedef std::function<void (const byte[], size_t)> output_fn;
+      typedef std::function<void (const byte[], size_t)> data_cb;
+      typedef std::function<void (Alert, const byte[], size_t)> alert_cb;
+      typedef std::function<bool (const Session&)> handshake_cb;
+      typedef std::function<void (const Handshake_Message&)> handshake_msg_cb;
+      typedef std::function<std::string (std::vector<std::string>)> next_protocol_fn;
+
+      /**
+       * @param output_fn is called with data for the outbound socket
+       *
+       * @param app_data_cb is called when new application data is received
+       *
+       * @param alert_cb is called when a TLS alert is received
+       *
+       * @param handshake_cb is called when a handshake is completed
+       */
+       BOTAN_DEPRECATED("Use TLS::Callbacks (virtual interface).")
+       Compat_Callbacks(output_fn out, data_cb app_data_cb, alert_cb alert_cb,
+                        handshake_cb hs_cb, handshake_msg_cb hs_msg_cb = nullptr,
+                        next_protocol_fn next_proto = nullptr)
+          : m_output_function(out), m_app_data_cb(app_data_cb),
+            m_alert_cb(std::bind(alert_cb, std::placeholders::_1, nullptr, 0)),
+            m_hs_cb(hs_cb), m_hs_msg_cb(hs_msg_cb), m_next_proto(next_proto) {}
+
+       BOTAN_DEPRECATED("Use TLS::Callbacks (virtual interface).")
+       Compat_Callbacks(output_fn out, data_cb app_data_cb,
+                        std::function<void (Alert)> alert_cb,
+                        handshake_cb hs_cb,
+                        handshake_msg_cb hs_msg_cb = nullptr,
+                        next_protocol_fn next_proto = nullptr)
+          : m_output_function(out), m_app_data_cb(app_data_cb),
+            m_alert_cb(alert_cb),
+            m_hs_cb(hs_cb), m_hs_msg_cb(hs_msg_cb), m_next_proto(next_proto) {}
+
+       void tls_emit_data(const byte data[], size_t size) override
+          {
+          BOTAN_ASSERT(m_output_function != nullptr,
+                       "Invalid TLS output function callback.");
+          m_output_function(data, size);
+          }
+
+       void tls_record_received(u64bit /*seq_no*/, const byte data[], size_t size) override
+          {
+          BOTAN_ASSERT(m_app_data_cb != nullptr,
+                       "Invalid TLS app data callback.");
+          m_app_data_cb(data, size);
+          }
+
+       void tls_alert(Alert alert) override
+          {
+          BOTAN_ASSERT(m_alert_cb != nullptr,
+                       "Invalid TLS alert callback.");
+          m_alert_cb(alert);
+          }
+
+       bool tls_session_established(const Session& session) override
+          {
+          BOTAN_ASSERT(m_hs_cb != nullptr,
+                       "Invalid TLS handshake callback.");
+          return m_hs_cb(session);
+          }
+
+       std::string tls_server_choose_app_protocol(const std::vector<std::string>& client_protos) override
+          {
+          if(m_next_proto != nullptr) { return m_next_proto(client_protos); }
+          return "";
+          }
+
+       void tls_inspect_handshake_msg(const Handshake_Message& hmsg) override
+          {
+          // The handshake message callback is optional so we can
+          // not assume it has been set.
+          if(m_hs_msg_cb != nullptr) { m_hs_msg_cb(hmsg); }
+          }
+
+    private:
+         const output_fn m_output_function;
+         const data_cb m_app_data_cb;
+         const std::function<void (Alert)> m_alert_cb;
+         const handshake_cb m_hs_cb;
+         const handshake_msg_cb m_hs_msg_cb;
+         const next_protocol_fn m_next_proto;
+   };
+
+}
+
+}
+
+#endif