lib/json_web_token/algorithm/ecdsa.rb
require 'json_web_token/algorithm/common'
require 'json_web_token/format/asn1'
module JsonWebToken
module Algorithm
# Sign or verify a JSON Web Signature (JWS) structure using ECDSA
# @see http://tools.ietf.org/html/rfc7518#section-3.4
module Ecdsa
extend JsonWebToken::Algorithm::Common
extend JsonWebToken::Format::Asn1
MAC_BYTE_COUNT = {
'256' => 64, # prime256v1 aka: secp256r1
'384' => 96, # secp384r1
'512' => 132 # secp521r1 note difference (not 128) due to using 521-bit integers
}
module_function
# @param sha_bits [String] desired security level in bits of the signature scheme
# @param private_key [OpenSSL::PKey::EC] key used to sign a digital signature, or mac
# @param signing_input [String] input payload for a mac computation
# @return [BinaryString] a digital signature, or mac
# @example
# Ecdsa.sign('256', private_key, 'signing_input').bytes
# # => [90, 34, 44, 252, 147, 130, 167, 173, 86, 191, 247, 93, 94, 12, 200, 30, 173, 115, 248, 89, 246, 222, 4, 213, 119, 74, 70, 20, 231, 194, 104, 103]
def sign(sha_bits, private_key, signing_input)
validate_key(sha_bits, private_key)
der = private_key.dsa_sign_asn1(ssl_digest_hash sha_bits, signing_input)
der_to_signature(der, sha_bits)
end
# @param mac [BinaryString] a digital signature, or mac
# @param sha_bits [String] desired security level in bits of the signature scheme
# @param public_key [OpenSSL::PKey::EC] key used to verify a digital signature, or mac
# @param signing_input [String] input payload for a mac computation
# @return [Boolean] a predicate to verify the signing_input for a given +mac+
# @example
# Ecdsa.verify?(< binary_string >, '256', < public_key >, 'signing_input')
# # => true
def verify?(mac, sha_bits, public_key, signing_input)
validate_key(sha_bits, public_key)
validate_signature_size(mac, sha_bits)
der = signature_to_der(mac, sha_bits)
public_key.dsa_verify_asn1(ssl_digest_hash(sha_bits, signing_input), der)
end
def validate_key_size(_sha_bits, _key); end
def ssl_digest_hash(sha_bits, signing_input)
digest_new(sha_bits).digest(signing_input)
end
def validate_signature_size(mac, sha_bits)
fail('Invalid signature') unless mac && mac.bytesize == MAC_BYTE_COUNT[sha_bits]
end
private_class_method :validate_key_size,
:ssl_digest_hash,
:validate_signature_size
end
end
end