TLS improvements

Use constant time operations when checking CBC padding in TLS decryption

Fix a bug in decoding ClientHellos that prevented DTLS rehandshakes
from working: on decode the session id and hello cookie would be
swapped, causing confusion between client and server.

Various changes in the service of finding the above DTLS bug that
should have been done before now anyway - better control of handshake
timeouts (via TLS::Policy), better reporting of handshake state in the
case of an error, and finally expose the facility for per-message
application callbacks.

1 files changed, 14 insertions, 3 deletions

diff --git a/src/lib/tls/tls_channel.h b/src/lib/tls/tls_channel.h
index 4e6874a16..9ef2d17c4 100644
--- a/src/lib/tls/tls_channel.h
+++ b/src/lib/tls/tls_channel.h
@@ -24,6 +24,7 @@ namespace TLS {
 class Connection_Cipher_State;
 class Connection_Sequence_Numbers;
 class Handshake_State;
+class Handshake_Message;
 
 /**
 * Generic interface for TLS endpoint
@@ -35,15 +36,18 @@ class BOTAN_DLL Channel
       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;
 
       Channel(output_fn out,
               data_cb app_data_cb,
               alert_cb alert_cb,
               handshake_cb hs_cb,
+              handshake_msg_cb hs_msg_cb,
               Session_Manager& session_manager,
               RandomNumberGenerator& rng,
+              const Policy& policy,
               bool is_datagram,
-              size_t reserved_io_buffer_size);
+              size_t io_buf_sz = 16*1024);
 
       Channel(const Channel&) = delete;
 
@@ -196,6 +200,8 @@ class BOTAN_DLL Channel
 
       Handshake_State& create_handshake_state(Protocol_Version version);
 
+      void inspect_handshake_message(const Handshake_Message& msg);
+
       void activate_session();
 
       void change_cipher_spec_reader(Connection_Side side);
@@ -214,8 +220,11 @@ class BOTAN_DLL Channel
 
       Session_Manager& session_manager() { return m_session_manager; }
 
+      const Policy& policy() const { return m_policy; }
+
       bool save_session(const Session& session) const { return m_handshake_cb(session); }
 
+      handshake_msg_cb get_handshake_msg_cb() const { return m_handshake_msg_cb; }
    private:
       size_t maximum_fragment_size() const;
 
@@ -245,14 +254,16 @@ class BOTAN_DLL Channel
       bool m_is_datagram;
 
       /* callbacks */
-      handshake_cb m_handshake_cb;
       data_cb m_data_cb;
       alert_cb m_alert_cb;
       output_fn m_output_fn;
+      handshake_cb m_handshake_cb;
+      handshake_msg_cb m_handshake_msg_cb;
 
       /* external state */
-      RandomNumberGenerator& m_rng;
       Session_Manager& m_session_manager;
+      const Policy& m_policy;
+      RandomNumberGenerator& m_rng;
 
       /* sequence number state */
       std::unique_ptr<Connection_Sequence_Numbers> m_sequence_numbers;