module JWT

# File lib/jwt.rb, line 228
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 75
def base64url_decode(str)
  str += '=' * (4 - str.length.modulo(4))
  Base64.decode64(str.tr('-_', '+/'))
end

# File lib/jwt.rb, line 80
def base64url_encode(str)
  Base64.encode64(str).tr('+/', '-_').gsub(/[\n=]/, '')
end

# File lib/jwt.rb, line 132
def decode(jwt, key = nil, verify = true, options = {}, &keyfinder)
  fail(JWT::DecodeError, 'Nil JSON web token') unless jwt

  header, payload, signature, signing_input = decoded_segments(jwt, verify)
  fail(JWT::DecodeError, 'Not enough or too many segments') unless header && payload

  default_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
  }

  options = default_options.merge(options)

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

  if options[:verify_expiration] && payload.include?('exp')
    fail(JWT::ExpiredSignature, 'Signature has expired') unless payload['exp'].to_i > (Time.now.to_i - options[:leeway])
  end
  if options[:verify_not_before] && payload.include?('nbf')
    fail(JWT::ImmatureSignature, 'Signature nbf has not been reached') unless payload['nbf'].to_i <= (Time.now.to_i + options[:leeway])
  end
  if options[:verify_iss] && options[:iss]
    fail(JWT::InvalidIssuerError, "Invalid issuer. Expected #{options[:iss]}, received #{payload['iss'] || '<none>'}") unless payload['iss'].to_s == options[:iss].to_s
  end
  if options[:verify_iat] && payload.include?('iat')
    fail(JWT::InvalidIatError, 'Invalid iat') unless payload['iat'].is_a?(Integer) && payload['iat'].to_i <= (Time.now.to_i + options[:leeway])
  end
  if options[:verify_aud] && options[:aud]
    if payload[:aud].is_a?(Array)
      fail(JWT::InvalidAudError, 'Invalid audience') unless payload['aud'].include?(options[:aud].to_s)
    else
      fail(JWT::InvalidAudError, "Invalid audience. Expected #{options[:aud]}, received #{payload['aud'] || '<none>'}") unless payload['aud'].to_s == options[:aud].to_s
    end
  end
  if options[:verify_sub] && options.include?(:sub)
    fail(JWT::InvalidSubError, "Invalid subject. Expected #{options[:sub]}, received #{payload['sub'] || '<none>'}") unless payload['sub'].to_s == options[:sub].to_s
  end
  if options[:verify_jti] && payload.include?('jti')
    fail(JWT::InvalidJtiError, 'need iat for verify jwt id') unless payload.include?('iat')
    fail(JWT::InvalidJtiError, 'Not a uniq jwt id') unless options[:jti].to_s == Digest::MD5.hexdigest("#{key}:#{payload['iat']}")
  end

  [payload, header]
end

# File lib/jwt.rb, line 118
def decode_header_and_payload(header_segment, payload_segment)
  header = decode_json(base64url_decode(header_segment))
  payload = decode_json(base64url_decode(payload_segment))
  [header, payload]
end

# File lib/jwt.rb, line 124
def decoded_segments(jwt, verify = true)
  header_segment, payload_segment, crypto_segment = raw_segments(jwt, verify)
  header, payload = decode_header_and_payload(header_segment, payload_segment)
  signature = base64url_decode(crypto_segment.to_s) if verify
  signing_input = [header_segment, payload_segment].join('.')
  [header, payload, signature, signing_input]
end

# File lib/jwt.rb, line 102
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 84
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 89
def encoded_payload(payload)
  base64url_encode(encode_json(payload))
end

# File lib/jwt.rb, line 93
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 111
def raw_segments(jwt, verify = true)
  segments = jwt.split('.')
  required_num_segments = verify ? [3] : [2, 3]
  fail(JWT::DecodeError, 'Not enough or too many segments') unless required_num_segments.include? segments.length
  segments
end

# File lib/jwt.rb, line 221
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 212
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 31
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 47
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 71
def sign_hmac(algorithm, msg, key)
  OpenSSL::HMAC.digest(OpenSSL::Digest.new(algorithm.sub('HS', 'sha')), key, msg)
end

# File lib/jwt.rb, line 43
def sign_rsa(algorithm, msg, private_key)
  private_key.sign(OpenSSL::Digest.new(algorithm.sub('RS', 'sha')), msg)
end

# File lib/jwt.rb, line 189
def signature_algorithm_and_key(header, key, &keyfinder)
  key = keyfinder.call(header) if keyfinder
  [header['alg'], key]
end

# File lib/jwt.rb, line 61
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 57
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 194
def verify_signature(algo, key, signing_input, signature)
  if %w(HS256 HS384 HS512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raiseed') unless secure_compare(signature, sign_hmac(algo, signing_input, key))
  elsif %w(RS256 RS384 RS512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raiseed') unless verify_rsa(algo, key, signing_input, signature)
  elsif %w(ES256 ES384 ES512).include?(algo)
    fail(JWT::VerificationError, 'Signature verification raiseed') 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