ec2.rb in cose-0.5.0

- old
+ new

@@ -1,8 +1,9 @@
 # frozen_string_literal: true
 
 require "cose/key/base"
+require "openssl"
 
 module COSE
   module Key
     class EC2 < Base
       ALG_LABEL = 3
@@ -11,11 +12,49 @@
       D_LABEL = -4
       X_LABEL = -2
       Y_LABEL = -3
 
       KTY_EC2 = 2
+      CRV_P256 = 1
+      CRV_P384 = 2
+      CRV_P521 = 3
 
+      PKEY_CURVES = {
+        CRV_P256 => "prime256v1",
+        CRV_P384 => "secp384r1",
+        CRV_P521 => "secp521r1"
+      }.freeze
+
+      def self.from_pkey(pkey)
+        curve = PKEY_CURVES.key(pkey.group.curve_name) || raise("Unsupported EC curve #{pkey.group.curve_name}")
+
+        case pkey
+        when OpenSSL::PKey::EC::Point
+          public_key = pkey
+        when OpenSSL::PKey::EC
+          public_key = pkey.public_key
+          private_key = pkey.private_key
+        else
+          raise "Unsupported"
+        end
+
+        if public_key
+          bytes = public_key.to_bn.to_s(2)[1..-1]
+
+          coordinate_length = bytes.size / 2
+
+          x_coordinate = bytes[0..(coordinate_length - 1)]
+          y_coordinate = bytes[coordinate_length..-1]
+        end
+
+        if private_key
+          d_coordinate = private_key.to_s(2)
+        end
+
+        new(curve: curve, x_coordinate: x_coordinate, y_coordinate: y_coordinate, d_coordinate: d_coordinate)
+      end
+
       attr_reader :algorithm, :curve, :d_coordinate, :x_coordinate, :y_coordinate
 
       def initialize(algorithm: nil, curve:, d_coordinate: nil, x_coordinate:, y_coordinate:)
         if !curve
           raise ArgumentError, "Required curve is missing"
@@ -27,9 +66,37 @@
           @algorithm = algorithm
           @curve = curve
           @d_coordinate = d_coordinate
           @x_coordinate = x_coordinate
           @y_coordinate = y_coordinate
+        end
+      end
+
+      def serialize
+        CBOR.encode(
+          Base::LABEL_KTY => KTY_EC2,
+          CRV_LABEL => curve,
+          X_LABEL => x_coordinate,
+          Y_LABEL => y_coordinate,
+          D_LABEL => d_coordinate
+        )
+      end
+
+      def to_pkey
+        if PKEY_CURVES[curve]
+          group = OpenSSL::PKey::EC::Group.new(PKEY_CURVES[curve])
+          pkey = OpenSSL::PKey::EC.new(group)
+          public_key_bn = OpenSSL::BN.new("\x04" + x_coordinate + y_coordinate, 2)
+          public_key_point = OpenSSL::PKey::EC::Point.new(group, public_key_bn)
+          pkey.public_key = public_key_point
+
+          if d_coordinate
+            pkey.private_key = OpenSSL::BN.new(d_coordinate, 2)
+          end
+
+          pkey
+        else
+          raise "Unsupported curve #{curve}"
         end
       end
 
       def self.from_map(map)
         enforce_type(map, KTY_EC2, "Not an EC2 key")