module JWT

# File lib/jwt/version.rb, line 4
def self.gem_version
  Gem::Version.new VERSION::STRING
end

# File lib/jwt.rb, line 169
def asn1_to_raw(signature, public_key)
  byte_size = (public_key.group.degree + 7) / 8
  OpenSSL::ASN1.decode(signature).value.map { |value| value.value.to_s(2).rjust(byte_size, "\x00") }.join
end

# File lib/jwt.rb, line 174
def base64url_decode(str)
  Decode.base64url_decode(str)
end

# File lib/jwt.rb, line 66
def base64url_encode(str)
  Base64.encode64(str).tr('+/', '-_').gsub(/[\n=]/, '')
end

# File lib/jwt.rb, line 97
def decode(jwt, key = nil, verify = true, custom_options = {}, &keyfinder)
  fail(JWT::DecodeError, 'Nil JSON web token') unless jwt

  options = {
    verify_expiration: true,
    verify_not_before: true,
    verify_iss: false,
    verify_iat: false,
    verify_jti: false,
    verify_aud: false,
    verify_sub: false,
    leeway: 0
  }

  merged_options = options.merge(custom_options)

  decoder = Decode.new jwt, key, verify, merged_options, &keyfinder
  header, payload, signature, signing_input = decoder.decode_segments
  decoder.verify

  fail(JWT::DecodeError, 'Not enough or too many segments') unless header && payload

  if verify
    algo, key = signature_algorithm_and_key(header, key, &keyfinder)
    if merged_options[:algorithm] && algo != merged_options[:algorithm]
      fail JWT::IncorrectAlgorithm, 'Expected a different algorithm'
    end
    verify_signature(algo, key, signing_input, signature)
  end

  [payload, header]
end

# File lib/jwt.rb, line 88
def encode(payload, key, algorithm = 'HS256', header_fields = {})
  algorithm ||= 'none'
  segments = []
  segments << encoded_header(algorithm, header_fields)
  segments << encoded_payload(payload)
  segments << encoded_signature(segments.join('.'), key, algorithm)
  segments.join('.')
end

# File lib/jwt.rb, line 70
def encoded_header(algorithm = 'HS256', header_fields = {})
  header = { 'typ' => 'JWT', 'alg' => algorithm }.merge(header_fields)
  base64url_encode(encode_json(header))
end

# File lib/jwt.rb, line 75
def encoded_payload(payload)
  base64url_encode(encode_json(payload))
end

# File lib/jwt.rb, line 79
def encoded_signature(signing_input, key, algorithm)
  if algorithm == 'none'
    ''
  else
    signature = sign(algorithm, signing_input, key)
    base64url_encode(signature)
  end
end

# File lib/jwt.rb, line 162
def raw_to_asn1(signature, private_key)
  byte_size = (private_key.group.degree + 7) / 8
  r = signature[0..(byte_size - 1)]
  s = signature[byte_size..-1]
  OpenSSL::ASN1::Sequence.new([r, s].map { |int| OpenSSL::ASN1::Integer.new(OpenSSL::BN.new(int, 2)) }).to_der
end

# File lib/jwt.rb, line 153
def secure_compare(a, b)
  return false if a.nil? || b.nil? || a.empty? || b.empty? || a.bytesize != b.bytesize
  l = a.unpack "C#{a.bytesize}"

  res = 0
  b.each_byte { |byte| res |= byte ^ l.shift }
  res == 0
end

# File lib/jwt.rb, line 22
def sign(algorithm, msg, key)
  if %w(HS256 HS384 HS512).include?(algorithm)
    sign_hmac(algorithm, msg, key)
  elsif %w(RS256 RS384 RS512).include?(algorithm)
    sign_rsa(algorithm, msg, key)
  elsif %w(ES256 ES384 ES512).include?(algorithm)
    sign_ecdsa(algorithm, msg, key)
  else
    fail NotImplementedError, 'Unsupported signing method'
  end
end

# File lib/jwt.rb, line 38
def sign_ecdsa(algorithm, msg, private_key)
  key_algorithm = NAMED_CURVES[private_key.group.curve_name]
  if algorithm != key_algorithm
    fail IncorrectAlgorithm, "payload algorithm is #{algorithm} but #{key_algorithm} signing key was provided"
  end

  digest = OpenSSL::Digest.new(algorithm.sub('ES', 'sha'))
  asn1_to_raw(private_key.dsa_sign_asn1(digest.digest(msg)), private_key)
end

# File lib/jwt.rb, line 62
def sign_hmac(algorithm, msg, key)
  OpenSSL::HMAC.digest(OpenSSL::Digest.new(algorithm.sub('HS', 'sha')), key, msg)
end

# File lib/jwt.rb, line 34
def sign_rsa(algorithm, msg, private_key)
  private_key.sign(OpenSSL::Digest.new(algorithm.sub('RS', 'sha')), msg)
end

# File lib/jwt.rb, line 130
def signature_algorithm_and_key(header, key, &keyfinder)
  key = keyfinder.call(header) if keyfinder
  [header['alg'], key]
end

# File lib/jwt.rb, line 52
def verify_ecdsa(algorithm, public_key, signing_input, signature)
  key_algorithm = NAMED_CURVES[public_key.group.curve_name]
  if algorithm != key_algorithm
    fail IncorrectAlgorithm, "payload algorithm is #{algorithm} but #{key_algorithm} verification key was provided"
  end

  digest = OpenSSL::Digest.new(algorithm.sub('ES', 'sha'))
  public_key.dsa_verify_asn1(digest.digest(signing_input), raw_to_asn1(signature, public_key))
end

# File lib/jwt.rb, line 48
def verify_rsa(algorithm, public_key, signing_input, signature)
  public_key.verify(OpenSSL::Digest.new(algorithm.sub('RS', 'sha')), signature, signing_input)
end

# File lib/jwt.rb, line 135
def verify_signature(algo, key, signing_input, signature)
  if %w(HS256 HS384 HS512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raised') unless secure_compare(signature, sign_hmac(algo, signing_input, key))
  elsif %w(RS256 RS384 RS512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raised') unless verify_rsa(algo, key, signing_input, signature)
  elsif %w(ES256 ES384 ES512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raised') unless verify_ecdsa(algo, key, signing_input, signature)
  else
    fail JWT::VerificationError, 'Algorithm not supported'
  end
rescue OpenSSL::PKey::PKeyError
  raise JWT::VerificationError, 'Signature verification raised'
ensure
  OpenSSL.errors.clear
end