Support encoding of supported point formats extension

1 files changed, 48 insertions, 0 deletions

diff --git a/src/lib/tls/tls_extensions.cpp b/src/lib/tls/tls_extensions.cpp
index e38e4ccdc..d82df20c5 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 +356,51 @@ Supported_Elliptic_Curves::Supported_Elliptic_Curves(TLS_Data_Reader& reader,
       }
    }
 
+std::vector<byte> Supported_Point_Formats::serialize() const
+   {
+   std::vector<byte> buf(1);
+
+   // if we send this extension, we prefer compressed points,
+   // otherwise we don't send it (which is equal to supporting only uncompressed)
+   buf.push_back(ANSIX962_COMPRESSED_PRIME);
+
+   // if this extension is sent, it MUST include uncompressed (RFC 4492, section 5.1)
+   buf.push_back(UNCOMPRESSED);
+
+   buf[0] = static_cast<byte>(buf.size()-1);
+
+   return buf;
+   }
+
+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)