module JWT

# File lib/jwt.rb, line 36
def self.base64url_decode(str)
  str += '=' * (4 - str.length.modulo(4))
  Base64.decode64(str.gsub("-", "+").gsub("_", "/"))
end

# File lib/jwt.rb, line 41
def self.base64url_encode(str)
  Base64.encode64(str).gsub("+", "-").gsub("/", "_").gsub("\n", "").gsub('=', '')
end

# File lib/jwt.rb, line 61
def self.decode(jwt, key=nil, verify=true, &keyfinder)
  segments = jwt.split('.')
  raise JWT::DecodeError.new("Not enough or too many segments") unless [2,3].include? segments.length
  header_segment, payload_segment, crypto_segment = segments
  signing_input = [header_segment, payload_segment].join('.')
  begin
    header = MultiJson.decode(base64url_decode(header_segment))
    payload = MultiJson.decode(base64url_decode(payload_segment))
    signature = base64url_decode(crypto_segment) if verify
  rescue MultiJson::LoadError => e
    raise JWT::DecodeError.new("Invalid segment encoding")
  end
  if verify
    algo = header['alg']

    if keyfinder
      key = keyfinder.call(header)
    end

    begin
      if ["HS256", "HS384", "HS512"].include?(algo)
        raise JWT::DecodeError.new("Signature verification failed") unless secure_compare(signature, sign_hmac(algo, signing_input, key))
      elsif ["RS256", "RS384", "RS512"].include?(algo)
        raise JWT::DecodeError.new("Signature verification failed") unless verify_rsa(algo, key, signing_input, signature)
      else
        raise JWT::DecodeError.new("Algorithm not supported")
      end
    rescue OpenSSL::PKey::PKeyError
      raise JWT::DecodeError.new("Signature verification failed")
    end
  end
  payload
end

# File lib/jwt.rb, line 45
def self.encode(payload, key, algorithm='HS256', header_fields={})
  algorithm ||= "none"
  segments = []
  header = {"typ" => "JWT", "alg" => algorithm}.merge(header_fields)
  segments << base64url_encode(MultiJson.encode(header))
  segments << base64url_encode(MultiJson.encode(payload))
  signing_input = segments.join('.')
  if algorithm != "none"
    signature = sign(algorithm, signing_input, key)
    segments << base64url_encode(signature)
  else
    segments << ""
  end
  segments.join('.')
end

# File lib/jwt.rb, line 97
def self.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 14
def self.sign(algorithm, msg, key)
  if ["HS256", "HS384", "HS512"].include?(algorithm)
    sign_hmac(algorithm, msg, key)
  elsif ["RS256", "RS384", "RS512"].include?(algorithm)
    sign_rsa(algorithm, msg, key)
  else
    raise NotImplementedError.new("Unsupported signing method")
  end
end

# File lib/jwt.rb, line 32
def self.sign_hmac(algorithm, msg, key)
  OpenSSL::HMAC.digest(OpenSSL::Digest::Digest.new(algorithm.sub('HS', 'sha')), key, msg)
end

# File lib/jwt.rb, line 24
def self.sign_rsa(algorithm, msg, private_key)
  private_key.sign(OpenSSL::Digest::Digest.new(algorithm.sub('RS', 'sha')), msg)
end

# File lib/jwt.rb, line 28
def self.verify_rsa(algorithm, public_key, signing_input, signature)
  public_key.verify(OpenSSL::Digest::Digest.new(algorithm.sub('RS', 'sha')), signature, signing_input)
end