Remove support for the TLS min fragment length extension.

11 files changed, 18 insertions, 147 deletions

diff --git a/src/lib/tls/msg_client_hello.cpp b/src/lib/tls/msg_client_hello.cpp
index 34edac29c..43ab84f33 100644
--- a/src/lib/tls/msg_client_hello.cpp
+++ b/src/lib/tls/msg_client_hello.cpp
@@ -141,9 +141,6 @@ Client_Hello::Client_Hello(Handshake_IO& io,
    m_extensions.add(new Session_Ticket(session.session_ticket()));
    m_extensions.add(new Supported_Elliptic_Curves(policy.allowed_ecc_curves()));
 
-   if(session.fragment_size() != 0)
-      m_extensions.add(new Maximum_Fragment_Length(session.fragment_size()));
-
    if(m_version.supports_negotiable_signature_algorithms())
       m_extensions.add(new Signature_Algorithms(policy.allowed_signature_hashes(),
                                                 policy.allowed_signature_methods()));
diff --git a/src/lib/tls/msg_server_hello.cpp b/src/lib/tls/msg_server_hello.cpp
index bbc483a4e..f9962a8ee 100644
--- a/src/lib/tls/msg_server_hello.cpp
+++ b/src/lib/tls/msg_server_hello.cpp
@@ -44,9 +44,6 @@ Server_Hello::Server_Hello(Handshake_IO& io,
    if(client_hello.supports_session_ticket() && offer_session_ticket)
       m_extensions.add(new Session_Ticket());
 
-   if(size_t max_fragment_size = client_hello.fragment_size())
-      m_extensions.add(new Maximum_Fragment_Length(max_fragment_size));
-
    if(!next_protocol.empty() && client_hello.supports_alpn())
       m_extensions.add(new Application_Layer_Protocol_Notification(next_protocol));
 
@@ -99,9 +96,6 @@ Server_Hello::Server_Hello(Handshake_IO& io,
    if(client_hello.supports_session_ticket() && offer_session_ticket)
       m_extensions.add(new Session_Ticket());
 
-   if(size_t max_fragment_size = resumed_session.fragment_size())
-      m_extensions.add(new Maximum_Fragment_Length(max_fragment_size));
-
    if(!next_protocol.empty() && client_hello.supports_alpn())
       m_extensions.add(new Application_Layer_Protocol_Notification(next_protocol));
 
diff --git a/src/lib/tls/tls_channel.cpp b/src/lib/tls/tls_channel.cpp
index 44627e7bc..2cf351c80 100644
--- a/src/lib/tls/tls_channel.cpp
+++ b/src/lib/tls/tls_channel.cpp
@@ -160,22 +160,6 @@ void Channel::renegotiate(bool force_full_renegotiation)
       throw Exception("Cannot renegotiate on inactive connection");
    }
 
-size_t Channel::maximum_fragment_size() const
-   {
-   // should we be caching this value?
-
-   if(auto pending = pending_state())
-      if(auto server_hello = pending->server_hello())
-         if(size_t frag = server_hello->fragment_size())
-            return frag;
-
-   if(auto active = active_state())
-      if(size_t frag = active->server_hello()->fragment_size())
-         return frag;
-
-   return MAX_PLAINTEXT_SIZE;
-   }
-
 void Channel::change_cipher_spec_reader(Connection_Side side)
    {
    auto pending = pending_state();
@@ -275,8 +259,6 @@ size_t Channel::received_data(const std::vector<byte>& buf)
 
 size_t Channel::received_data(const byte input[], size_t input_size)
    {
-   const size_t max_fragment_size = maximum_fragment_size();
-
    try
       {
       while(!is_closed() && input_size)
@@ -316,9 +298,9 @@ size_t Channel::received_data(const byte input[], size_t input_size)
          if(input_size == 0 && needed != 0)
             return needed; // need more data to complete record
 
-         if(record.size() > max_fragment_size)
+         if(record.size() > MAX_PLAINTEXT_SIZE)
             throw TLS_Exception(Alert::RECORD_OVERFLOW,
-                                "TLS input record is larger than allowed maximum");
+                                "TLS plaintext record is larger than allowed maximum");
 
          if(record_type == HANDSHAKE || record_type == CHANGE_CIPHER_SPEC)
             {
@@ -492,11 +474,9 @@ void Channel::send_record_array(u16bit epoch, byte type, const byte input[], siz
       length -= 1;
       }
 
-   const size_t max_fragment_size = maximum_fragment_size();
-
    while(length)
       {
-      const size_t sending = std::min(length, max_fragment_size);
+      const size_t sending = std::min<size_t>(length, MAX_PLAINTEXT_SIZE);
       write_record(cipher_state.get(), epoch, type, input, sending);
 
       input += sending;
diff --git a/src/lib/tls/tls_channel.h b/src/lib/tls/tls_channel.h
index aca5c7138..e0219c242 100644
--- a/src/lib/tls/tls_channel.h
+++ b/src/lib/tls/tls_channel.h
@@ -204,8 +204,6 @@ class BOTAN_DLL Channel
 
       handshake_msg_cb get_handshake_msg_cb() const { return m_handshake_msg_cb; }
    private:
-      size_t maximum_fragment_size() const;
-
       void send_record(byte record_type, const std::vector<byte>& record);
 
       void send_record_under_epoch(u16bit epoch, byte record_type,
diff --git a/src/lib/tls/tls_client.cpp b/src/lib/tls/tls_client.cpp
index 623a52225..368e4569e 100644
--- a/src/lib/tls/tls_client.cpp
+++ b/src/lib/tls/tls_client.cpp
@@ -509,7 +509,6 @@ void Client::process_handshake_msg(const Handshake_State* active_state,
          state.server_hello()->ciphersuite(),
          state.server_hello()->compression_method(),
          CLIENT,
-         state.server_hello()->fragment_size(),
          state.server_hello()->supports_extended_master_secret(),
          get_peer_cert_chain(state),
          session_ticket,
diff --git a/src/lib/tls/tls_extensions.cpp b/src/lib/tls/tls_extensions.cpp
index 6bf32f1f1..b81a0dcb9 100644
--- a/src/lib/tls/tls_extensions.cpp
+++ b/src/lib/tls/tls_extensions.cpp
@@ -24,9 +24,6 @@ Extension* make_extension(TLS_Data_Reader& reader,
       case TLSEXT_SERVER_NAME_INDICATION:
          return new Server_Name_Indicator(reader, size);
 
-      case TLSEXT_MAX_FRAGMENT_LENGTH:
-         return new Maximum_Fragment_Length(reader, size);
-
       case TLSEXT_SRP_IDENTIFIER:
          return new SRP_Identifier(reader, size);
 
@@ -215,53 +212,6 @@ std::vector<byte> Renegotiation_Extension::serialize() const
    return buf;
    }
 
-std::vector<byte> Maximum_Fragment_Length::serialize() const
-   {
-   switch(m_max_fragment)
-      {
-      case 512:
-         return std::vector<byte>(1, 1);
-      case 1024:
-         return std::vector<byte>(1, 2);
-      case 2048:
-         return std::vector<byte>(1, 3);
-      case 4096:
-         return std::vector<byte>(1, 4);
-      default:
-         throw Invalid_Argument("Bad setting " +
-                                     std::to_string(m_max_fragment) +
-                                     " for maximum fragment size");
-      }
-   }
-
-Maximum_Fragment_Length::Maximum_Fragment_Length(TLS_Data_Reader& reader,
-                                                 u16bit extension_size)
-   {
-   if(extension_size != 1)
-      throw Decoding_Error("Bad size for maximum fragment extension");
-
-   const byte val = reader.get_byte();
-
-   switch(val)
-      {
-      case 1:
-         m_max_fragment = 512;
-         break;
-      case 2:
-         m_max_fragment = 1024;
-         break;
-      case 3:
-         m_max_fragment = 2048;
-         break;
-      case 4:
-         m_max_fragment = 4096;
-         break;
-      default:
-         throw TLS_Exception(Alert::ILLEGAL_PARAMETER,
-                             "Bad value " + std::to_string(val) + " for max fragment len");
-      }
-   }
-
 Application_Layer_Protocol_Notification::Application_Layer_Protocol_Notification(TLS_Data_Reader& reader,
                                                                                  u16bit extension_size)
    {
diff --git a/src/lib/tls/tls_extensions.h b/src/lib/tls/tls_extensions.h
index 8b2cbc096..a4ca31410 100644
--- a/src/lib/tls/tls_extensions.h
+++ b/src/lib/tls/tls_extensions.h
@@ -23,7 +23,7 @@ class TLS_Data_Reader;
 
 enum Handshake_Extension_Type {
    TLSEXT_SERVER_NAME_INDICATION = 0,
-   TLSEXT_MAX_FRAGMENT_LENGTH    = 1,
+   // 1 is maximum fragment length
    TLSEXT_CLIENT_CERT_URL        = 2,
    TLSEXT_TRUSTED_CA_KEYS        = 3,
    TLSEXT_TRUNCATED_HMAC         = 4,
@@ -150,38 +150,6 @@ class Renegotiation_Extension final : public Extension
    };
 
 /**
-* Maximum Fragment Length Negotiation Extension (RFC 4366 sec 3.2)
-*/
-class Maximum_Fragment_Length final : public Extension
-   {
-   public:
-      static Handshake_Extension_Type static_type()
-         { return TLSEXT_MAX_FRAGMENT_LENGTH; }
-
-      Handshake_Extension_Type type() const override { return static_type(); }
-
-      bool empty() const override { return false; }
-
-      size_t fragment_size() const { return m_max_fragment; }
-
-      std::vector<byte> serialize() const override;
-
-      /**
-      * @param max_fragment specifies what maximum fragment size to
-      *        advertise. Currently must be one of 512, 1024, 2048, or
-      *        4096.
-      */
-      Maximum_Fragment_Length(size_t max_fragment) :
-         m_max_fragment(max_fragment) {}
-
-      Maximum_Fragment_Length(TLS_Data_Reader& reader,
-                              u16bit extension_size);
-
-   private:
-      size_t m_max_fragment;
-   };
-
-/**
 * ALPN (RFC 7301)
 */
 class Application_Layer_Protocol_Notification final : public Extension
diff --git a/src/lib/tls/tls_messages.h b/src/lib/tls/tls_messages.h
index ba05ee9a7..739eca23e 100644
--- a/src/lib/tls/tls_messages.h
+++ b/src/lib/tls/tls_messages.h
@@ -114,13 +114,6 @@ class Client_Hello final : public Handshake_Message
          return std::vector<byte>();
          }
 
-      size_t fragment_size() const
-         {
-         if(Maximum_Fragment_Length* frag = m_extensions.get<Maximum_Fragment_Length>())
-            return frag->fragment_size();
-         return 0;
-         }
-
       bool supports_session_ticket() const
          {
          return m_extensions.has<Session_Ticket>();
@@ -225,13 +218,6 @@ class Server_Hello final : public Handshake_Message
          return std::vector<byte>();
          }
 
-      size_t fragment_size() const
-         {
-         if(Maximum_Fragment_Length* frag = m_extensions.get<Maximum_Fragment_Length>())
-            return frag->fragment_size();
-         return 0;
-         }
-
       bool supports_extended_master_secret() const
          {
          return m_extensions.has<Extended_Master_Secret>();
diff --git a/src/lib/tls/tls_server.cpp b/src/lib/tls/tls_server.cpp
index 76db9ce6b..6aed40479 100644
--- a/src/lib/tls/tls_server.cpp
+++ b/src/lib/tls/tls_server.cpp
@@ -665,7 +665,6 @@ void Server::process_handshake_msg(const Handshake_State* active_state,
             state.server_hello()->ciphersuite(),
             state.server_hello()->compression_method(),
             SERVER,
-            state.server_hello()->fragment_size(),
             state.server_hello()->supports_extended_master_secret(),
             get_peer_cert_chain(state),
             std::vector<byte>(),
diff --git a/src/lib/tls/tls_session.cpp b/src/lib/tls/tls_session.cpp
index dbdb99ac8..6d5fc1a7b 100644
--- a/src/lib/tls/tls_session.cpp
+++ b/src/lib/tls/tls_session.cpp
@@ -23,7 +23,6 @@ Session::Session(const std::vector<byte>& session_identifier,
                  u16bit ciphersuite,
                  byte compression_method,
                  Connection_Side side,
-                 size_t fragment_size,
                  bool extended_master_secret,
                  const std::vector<X509_Certificate>& certs,
                  const std::vector<byte>& ticket,
@@ -40,7 +39,6 @@ Session::Session(const std::vector<byte>& session_identifier,
    m_connection_side(side),
    m_srtp_profile(srtp_profile),
    m_extended_master_secret(extended_master_secret),
-   m_fragment_size(fragment_size),
    m_peer_certs(certs),
    m_server_info(server_info),
    m_srp_identifier(srp_identifier)
@@ -69,6 +67,7 @@ Session::Session(const byte ber[], size_t ber_len)
 
    size_t start_time = 0;
    size_t srtp_profile = 0;
+   size_t fragment_size = 0;
 
    BER_Decoder(ber, ber_len)
       .start_cons(SEQUENCE)
@@ -82,7 +81,7 @@ Session::Session(const byte ber[], size_t ber_len)
         .decode_integer_type(m_ciphersuite)
         .decode_integer_type(m_compression_method)
         .decode_integer_type(side_code)
-        .decode_integer_type(m_fragment_size)
+        .decode_integer_type(fragment_size)
         .decode(m_extended_master_secret)
         .decode(m_master_secret, OCTET_STRING)
         .decode(peer_cert_bits, OCTET_STRING)
@@ -94,6 +93,16 @@ Session::Session(const byte ber[], size_t ber_len)
       .end_cons()
       .verify_end();
 
+   /*
+   Fragment size is not supported anymore, but the field is still
+   set in the session object.
+   */
+   if(fragment_size != 0)
+      {
+      throw Decoding_Error("Serialized TLS session used maximum fragment length which is "
+                           " no longer supported");
+      }
+
    m_version = Protocol_Version(major_version, minor_version);
    m_start_time = std::chrono::system_clock::from_time_t(start_time);
    m_connection_side = static_cast<Connection_Side>(side_code);
@@ -131,7 +140,7 @@ secure_vector<byte> Session::DER_encode() const
          .encode(static_cast<size_t>(m_ciphersuite))
          .encode(static_cast<size_t>(m_compression_method))
          .encode(static_cast<size_t>(m_connection_side))
-         .encode(static_cast<size_t>(m_fragment_size))
+         .encode(static_cast<size_t>(/*old fragment size*/0))
          .encode(m_extended_master_secret)
          .encode(m_master_secret, OCTET_STRING)
          .encode(peer_cert_bits, OCTET_STRING)
diff --git a/src/lib/tls/tls_session.h b/src/lib/tls/tls_session.h
index f38ca8e27..0e22037f6 100644
--- a/src/lib/tls/tls_session.h
+++ b/src/lib/tls/tls_session.h
@@ -38,8 +38,7 @@ class BOTAN_DLL Session
          m_compression_method(0),
          m_connection_side(static_cast<Connection_Side>(0)),
          m_srtp_profile(0),
-         m_extended_master_secret(false),
-         m_fragment_size(0)
+         m_extended_master_secret(false)
             {}
 
       /**
@@ -51,7 +50,6 @@ class BOTAN_DLL Session
               u16bit ciphersuite,
               byte compression_method,
               Connection_Side side,
-              size_t fragment_size,
               bool supports_extended_master_secret,
               const std::vector<X509_Certificate>& peer_certs,
               const std::vector<byte>& session_ticket,
@@ -153,11 +151,6 @@ class BOTAN_DLL Session
       const std::vector<byte>& session_id() const { return m_identifier; }
 
       /**
-      * Get the negotiated maximum fragment size (or 0 if default)
-      */
-      size_t fragment_size() const { return m_fragment_size; }
-
-      /**
       * Get the negotiated DTLS-SRTP algorithm (RFC 5764)
       */
       u16bit dtls_srtp_profile() const { return m_srtp_profile; }
@@ -202,8 +195,6 @@ class BOTAN_DLL Session
       u16bit m_srtp_profile;
       bool m_extended_master_secret;
 
-      size_t m_fragment_size;
-
       std::vector<X509_Certificate> m_peer_certs;
       Server_Information m_server_info; // optional
       std::string m_srp_identifier; // optional