Merge GH #645 TLS compressed points

9 files changed, 133 insertions, 4 deletions

diff --git a/src/lib/tls/msg_client_hello.cpp b/src/lib/tls/msg_client_hello.cpp
index b493fd3ee..36335e7ce 100644
--- a/src/lib/tls/msg_client_hello.cpp
+++ b/src/lib/tls/msg_client_hello.cpp
@@ -98,8 +98,12 @@ Client_Hello::Client_Hello(Handshake_IO& io,
    if(reneg_info.empty() && !next_protocols.empty())
       m_extensions.add(new Application_Layer_Protocol_Notification(next_protocols));
 
+   if(m_version.supports_negotiable_signature_algorithms())
+      m_extensions.add(new Signature_Algorithms(policy.allowed_signature_hashes(),
+                                                policy.allowed_signature_methods()));
+
    if(m_version.is_datagram_protocol())
-     m_extensions.add(new SRTP_Protection_Profiles(policy.srtp_profiles()));
+      m_extensions.add(new SRTP_Protection_Profiles(policy.srtp_profiles()));
 
 #if defined(BOTAN_HAS_SRP6)
    m_extensions.add(new SRP_Identifier(client_settings.srp_identifier()));
@@ -112,6 +116,11 @@ Client_Hello::Client_Hello(Handshake_IO& io,
 
    m_extensions.add(new Supported_Elliptic_Curves(policy.allowed_ecc_curves()));
 
+   if(!policy.allowed_ecc_curves().empty() && policy.use_ecc_point_compression())
+   {
+      m_extensions.add(new Supported_Point_Formats());
+   }
+
    if(m_version.supports_negotiable_signature_algorithms())
       m_extensions.add(new Signature_Algorithms(policy.allowed_signature_hashes(),
                                                 policy.allowed_signature_methods()));
@@ -156,6 +165,11 @@ 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(!policy.allowed_ecc_curves().empty() && policy.use_ecc_point_compression())
+   {
+      m_extensions.add(new Supported_Point_Formats());
+   }
+
    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_client_kex.cpp b/src/lib/tls/msg_client_kex.cpp
index bc4d33d52..0eceadb3b 100644
--- a/src/lib/tls/msg_client_kex.cpp
+++ b/src/lib/tls/msg_client_kex.cpp
@@ -172,7 +172,10 @@ Client_Key_Exchange::Client_Key_Exchange(Handshake_IO& io,
             append_tls_length_value(m_pre_master, psk.bits_of(), 2);
             }
 
-         append_tls_length_value(m_key_material, priv_key.public_value(), 1);
+         // follow server's preference for point compression
+         append_tls_length_value(m_key_material,
+               priv_key.public_value(state.server_hello()->prefers_compressed_ec_points() ?
+               PointGFp::COMPRESSED : PointGFp::UNCOMPRESSED ), 1);
          }
 #if defined(BOTAN_HAS_SRP6)
       else if(kex_algo == "SRP_SHA")
diff --git a/src/lib/tls/msg_server_hello.cpp b/src/lib/tls/msg_server_hello.cpp
index ebe8fb085..4f95a5c9d 100644
--- a/src/lib/tls/msg_server_hello.cpp
+++ b/src/lib/tls/msg_server_hello.cpp
@@ -35,12 +35,18 @@ Server_Hello::Server_Hello(Handshake_IO& io,
    if(client_hello.supports_extended_master_secret())
       m_extensions.add(new Extended_Master_Secret);
 
+   Ciphersuite c = Ciphersuite::by_id(m_ciphersuite);
+
    if(client_hello.supports_encrypt_then_mac() && policy.negotiate_encrypt_then_mac())
       {
-      Ciphersuite c = Ciphersuite::by_id(m_ciphersuite);
       if(c.cbc_ciphersuite())
          m_extensions.add(new Encrypt_then_MAC);
       }
+
+   if(c.ecc_ciphersuite() && policy.use_ecc_point_compression())
+      {
+      m_extensions.add(new Supported_Point_Formats());
+      }
       
    if(client_hello.secure_renegotiation())
       m_extensions.add(new Renegotiation_Extension(reneg_info));
diff --git a/src/lib/tls/msg_server_kex.cpp b/src/lib/tls/msg_server_kex.cpp
index 10581fe45..33b980ba9 100644
--- a/src/lib/tls/msg_server_kex.cpp
+++ b/src/lib/tls/msg_server_kex.cpp
@@ -85,7 +85,10 @@ Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
       m_params.push_back(get_byte(0, named_curve_id));
       m_params.push_back(get_byte(1, named_curve_id));
 
-      append_tls_length_value(m_params, ecdh->public_value(), 1);
+      // follow client's preference for point compression
+      append_tls_length_value(m_params,
+            ecdh->public_value(state.client_hello()->prefers_compressed_ec_points() ?
+            PointGFp::COMPRESSED : PointGFp::UNCOMPRESSED), 1);
 
       m_kex_key.reset(ecdh.release());
       }
diff --git a/src/lib/tls/tls_extensions.cpp b/src/lib/tls/tls_extensions.cpp
index e38e4ccdc..df265d915 100644
--- a/src/lib/tls/tls_extensions.cpp
+++ b/src/lib/tls/tls_extensions.cpp
@@ -33,6 +33,9 @@ Extension* make_extension(TLS_Data_Reader& reader,
       case TLSEXT_USABLE_ELLIPTIC_CURVES:
          return new Supported_Elliptic_Curves(reader, size);
 
+      case TLSEXT_EC_POINT_FORMATS:
+         return new Supported_Point_Formats(reader, size);
+
       case TLSEXT_SAFE_RENEGOTIATION:
          return new Renegotiation_Extension(reader, size);
 
@@ -353,6 +356,43 @@ Supported_Elliptic_Curves::Supported_Elliptic_Curves(TLS_Data_Reader& reader,
       }
    }
 
+std::vector<byte> Supported_Point_Formats::serialize() const
+   {
+   // if we send this extension, we prefer compressed points,
+   // otherwise we don't send it (which is equal to supporting only uncompressed)
+   // if this extension is sent, it MUST include uncompressed (RFC 4492, section 5.1)
+   return std::vector<byte>{2, ANSIX962_COMPRESSED_PRIME, UNCOMPRESSED};
+   }
+
+Supported_Point_Formats::Supported_Point_Formats(TLS_Data_Reader& reader,
+                                                 u16bit extension_size)
+   {
+   byte len = reader.get_byte();
+
+   if(len + 1 != extension_size)
+      throw Decoding_Error("Inconsistent length field in supported point formats list");
+
+   for(size_t i = 0; i != len; ++i)
+      {
+      byte format = reader.get_byte();
+
+      if(format == UNCOMPRESSED)
+         {
+         m_prefers_compressed = false;
+         reader.discard_next(len-i-1);
+         return;
+         }
+      else if(format == ANSIX962_COMPRESSED_PRIME)
+         {
+         m_prefers_compressed = true;
+         reader.discard_next(len-i-1);
+         return;
+         }
+
+      // ignore ANSIX962_COMPRESSED_CHAR2, we don't support these curves
+      }
+   }
+
 std::string Signature_Algorithms::hash_algo_name(byte code)
    {
    switch(code)
diff --git a/src/lib/tls/tls_extensions.h b/src/lib/tls/tls_extensions.h
index c270bf23a..d69e40a60 100644
--- a/src/lib/tls/tls_extensions.h
+++ b/src/lib/tls/tls_extensions.h
@@ -258,6 +258,38 @@ class Supported_Elliptic_Curves final : public Extension
    };
 
 /**
+* Supported Point Formats Extension (RFC 4492)
+*/
+class Supported_Point_Formats final : public Extension
+   {
+   public:
+      enum ECPointFormat : byte {
+         UNCOMPRESSED = 0,
+         ANSIX962_COMPRESSED_PRIME = 1,
+         ANSIX962_COMPRESSED_CHAR2 = 2, // don't support these curves
+      };
+
+      static Handshake_Extension_Type static_type()
+         { return TLSEXT_EC_POINT_FORMATS; }
+
+      Handshake_Extension_Type type() const override { return static_type(); }
+
+      std::vector<byte> serialize() const override;
+
+      explicit Supported_Point_Formats() : m_prefers_compressed(true) {}
+
+      Supported_Point_Formats(TLS_Data_Reader& reader,
+                              u16bit extension_size);
+
+      bool empty() const override { return false; }
+
+      bool prefers_compressed() { return m_prefers_compressed; }
+
+   private:
+      bool m_prefers_compressed = false;
+   };
+
+/**
 * Signature Algorithms Extension for TLS 1.2 (RFC 5246)
 */
 class Signature_Algorithms final : public Extension
diff --git a/src/lib/tls/tls_messages.h b/src/lib/tls/tls_messages.h
index 698dbc99f..25228c865 100644
--- a/src/lib/tls/tls_messages.h
+++ b/src/lib/tls/tls_messages.h
@@ -121,6 +121,15 @@ class BOTAN_DLL Client_Hello final : public Handshake_Message
          return std::vector<std::string>();
          }
 
+      bool prefers_compressed_ec_points() const
+         {
+         if(Supported_Point_Formats* ecc_formats = m_extensions.get<Supported_Point_Formats>())
+            {
+            return ecc_formats->prefers_compressed();
+            }
+         return false;
+         }
+
       std::string sni_hostname() const
          {
          if(Server_Name_Indicator* sni = m_extensions.get<Server_Name_Indicator>())
@@ -328,6 +337,15 @@ class BOTAN_DLL Server_Hello final : public Handshake_Message
       std::set<Handshake_Extension_Type> extension_types() const
          { return m_extensions.extension_types(); }
 
+      bool prefers_compressed_ec_points() const
+         {
+         if(auto ecc_formats = m_extensions.get<Supported_Point_Formats>())
+            {
+            return ecc_formats->prefers_compressed();
+            }
+         return false;
+         }
+
       Server_Hello(Handshake_IO& io,
                    Handshake_Hash& hash,
                    const Policy& policy,
diff --git a/src/lib/tls/tls_policy.cpp b/src/lib/tls/tls_policy.cpp
index 592d4f572..9646aa320 100644
--- a/src/lib/tls/tls_policy.cpp
+++ b/src/lib/tls/tls_policy.cpp
@@ -104,6 +104,11 @@ bool Policy::allowed_ecc_curve(const std::string& curve) const
    return value_exists(allowed_ecc_curves(), curve);
    }
 
+bool Policy::use_ecc_point_compression() const
+   {
+   return false;
+   }
+
 /*
 * Choose an ECC curve to use
 */
diff --git a/src/lib/tls/tls_policy.h b/src/lib/tls/tls_policy.h
index 76e80ddde..47ac51685 100644
--- a/src/lib/tls/tls_policy.h
+++ b/src/lib/tls/tls_policy.h
@@ -67,6 +67,11 @@ class BOTAN_DLL Policy
       bool allowed_ecc_curve(const std::string& curve) const;
 
       /**
+      * Request that ECC curve points are sent compressed
+      */
+      virtual bool use_ecc_point_compression() const;
+
+      /**
       * Returns a list of compression algorithms we are willing to use,
       * in order of preference. Allowed values any value of
       * Compression_Method.
@@ -348,6 +353,9 @@ class BOTAN_DLL Text_Policy : public Policy
       std::vector<std::string> allowed_ecc_curves() const override
          { return get_list("ecc_curves", Policy::allowed_ecc_curves()); }
       
+      bool use_ecc_point_compression() const override
+         { return get_bool("use_ecc_point_compression", Policy::use_ecc_point_compression()); }
+
       bool allow_tls10() const override
          { return get_bool("allow_tls10", Policy::allow_tls10()); }