Class: COSE::Key::EC2

Inherits:
CurveKey show all
Defined in:
lib/cose/key/ec2.rb

Constant Summary collapse

LABEL_Y = 
-3
KTY_EC2 = 
2
ZERO_BYTE = 
"\0".b

Constants inherited from CurveKey

CurveKey::LABEL_CRV, CurveKey::LABEL_D, CurveKey::LABEL_X

Constants inherited from Base

Base::LABEL_ALG, Base::LABEL_BASE_IV, Base::LABEL_KEY_OPS, Base::LABEL_KID, Base::LABEL_KTY

Instance Attribute Summary collapse

Attributes inherited from CurveKey

#crv, #d, #x

Attributes inherited from Base

#alg, #base_iv, #key_ops, #kid

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Base

deserialize, from_map, #serialize

Constructor Details

#initialize(y: nil, **keyword_arguments) ⇒ EC2

rubocop:disable Naming/MethodParameterName



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# File 'lib/cose/key/ec2.rb', line 53

def initialize(y: nil, **keyword_arguments) # rubocop:disable Naming/MethodParameterName
  if (!y || !keyword_arguments[:x]) && !keyword_arguments[:d]
    raise ArgumentError, "Both x and y are required if d is missing"
  else
    super(**keyword_arguments)

    @y = y
  end
end

Instance Attribute Details

#y ⇒ Object (readonly)

Returns the value of attribute y.



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# File 'lib/cose/key/ec2.rb', line 51

def y
  @y
end

Class Method Details

.enforce_type(map) ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 16

def self.enforce_type(map)
  if map[LABEL_KTY] != KTY_EC2
    raise "Not an EC2 key"
  end
end

.from_pkey(pkey) ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 22

def self.from_pkey(pkey)
  curve = Curve.by_pkey_name(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 = bytes[0..(coordinate_length - 1)]
    y = bytes[coordinate_length..-1]
  end

  if private_key
    d = private_key.to_s(2)
  end

  new(crv: curve.id, x: x, y: y, d: d)
end

.keyword_arguments_for_initialize(map) ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 115

def self.keyword_arguments_for_initialize(map)
  super.merge(y: map[LABEL_Y])
end

Instance Method Details

#curve ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 111

def curve
  Curve.find(crv)
end

#map ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 63

def map
  super.merge(
    Base::LABEL_KTY => KTY_EC2,
    LABEL_Y => y,
  ).compact
end

#pad_coordinate(group, coordinate) ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 119

def pad_coordinate(group, coordinate)
  coordinate_length = (group.degree + 7) / 8
  padding_required = coordinate_length - coordinate.length
  return coordinate if padding_required <= 0

  (ZERO_BYTE * padding_required) + coordinate
end

#to_pkey ⇒ Object 



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# File 'lib/cose/key/ec2.rb', line 70

def to_pkey
  if curve
    group = OpenSSL::PKey::EC::Group.new(curve.pkey_name)
    public_key_bn = OpenSSL::BN.new("\x04" + pad_coordinate(group, x) + pad_coordinate(group, y), 2)
    public_key_point = OpenSSL::PKey::EC::Point.new(group, public_key_bn)

    # RFC5480 SubjectPublicKeyInfo
    asn1 = OpenSSL::ASN1::Sequence(
      [
        OpenSSL::ASN1::Sequence(
          [
            OpenSSL::ASN1::ObjectId("id-ecPublicKey"),
            OpenSSL::ASN1::ObjectId(curve.pkey_name),
          ]
        ),
        OpenSSL::ASN1::BitString(public_key_point.to_octet_string(:uncompressed))
      ]
    )

    if d
      # RFC5915 ECPrivateKey
      asn1 = OpenSSL::ASN1::Sequence(
        [
          OpenSSL::ASN1::Integer.new(1),
          # Not properly padded but OpenSSL doesn't mind
          OpenSSL::ASN1::OctetString(OpenSSL::BN.new(d, 2).to_s(2)),
          OpenSSL::ASN1::ObjectId(curve.pkey_name, 0, :EXPLICIT),
          OpenSSL::ASN1::BitString(public_key_point.to_octet_string(:uncompressed), 1, :EXPLICIT),
        ]
      )

      der = asn1.to_der
      return OpenSSL::PKey::EC.new(der)
    end

    OpenSSL::PKey::EC.new(asn1.to_der)
  else
    raise "Unsupported curve #{crv}"
  end
end