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# frozen_string_literal: true
require "cose/key/curve"
require "cose/key/curve_key"
require "openssl"
module COSE
module Key
class EC2 < CurveKey
LABEL_Y = -3
KTY_EC2 = 2
ZERO_BYTE = "\0".b
def self.enforce_type(map)
if map[LABEL_KTY] != KTY_EC2
raise "Not an EC2 key"
end
end
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
attr_reader :y
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
def map
super.merge(
Base::LABEL_KTY => KTY_EC2,
LABEL_Y => y,
).compact
end
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
def curve
Curve.find(crv)
end
def self.keyword_arguments_for_initialize(map)
super.merge(y: map[LABEL_Y])
end
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
end
end
end
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