from __future__ import (absolute_import, print_function, division) import os import select import socket import sys import threading import time import traceback import contextlib import binascii from six.moves import range import certifi from backports import ssl_match_hostname import six import OpenSSL from OpenSSL import SSL from netlib import certutils, version_check, basetypes, exceptions # This is a rather hackish way to make sure that # the latest version of pyOpenSSL is actually installed. version_check.check_pyopenssl_version() if six.PY2: socket_fileobject = socket._fileobject else: socket_fileobject = socket.SocketIO EINTR = 4 if os.environ.get("NO_ALPN"): HAS_ALPN = False else: HAS_ALPN = OpenSSL._util.lib.Cryptography_HAS_ALPN # To enable all SSL methods use: SSLv23 # then add options to disable certain methods # https://bugs.launchpad.net/pyopenssl/+bug/1020632/comments/3 SSL_BASIC_OPTIONS = ( SSL.OP_CIPHER_SERVER_PREFERENCE ) if hasattr(SSL, "OP_NO_COMPRESSION"): SSL_BASIC_OPTIONS |= SSL.OP_NO_COMPRESSION SSL_DEFAULT_METHOD = SSL.SSLv23_METHOD SSL_DEFAULT_OPTIONS = ( SSL.OP_NO_SSLv2 | SSL.OP_NO_SSLv3 | SSL_BASIC_OPTIONS ) if hasattr(SSL, "OP_NO_COMPRESSION"): SSL_DEFAULT_OPTIONS |= SSL.OP_NO_COMPRESSION """ Map a reasonable SSL version specification into the format OpenSSL expects. Don't ask... https://bugs.launchpad.net/pyopenssl/+bug/1020632/comments/3 """ sslversion_choices = { "all": (SSL.SSLv23_METHOD, SSL_BASIC_OPTIONS), # SSLv23_METHOD + NO_SSLv2 + NO_SSLv3 == TLS 1.0+ # TLSv1_METHOD would be TLS 1.0 only "secure": (SSL.SSLv23_METHOD, (SSL.OP_NO_SSLv2 | SSL.OP_NO_SSLv3 | SSL_BASIC_OPTIONS)), "SSLv2": (SSL.SSLv2_METHOD, SSL_BASIC_OPTIONS), "SSLv3": (SSL.SSLv3_METHOD, SSL_BASIC_OPTIONS), "TLSv1": (SSL.TLSv1_METHOD, SSL_BASIC_OPTIONS), "TLSv1_1": (SSL.TLSv1_1_METHOD, SSL_BASIC_OPTIONS), "TLSv1_2": (SSL.TLSv1_2_METHOD, SSL_BASIC_OPTIONS), } class SSLKeyLogger(object): def __init__(self, filename): self.filename = filename self.f = None self.lock = threading.Lock() # required for functools.wraps, which pyOpenSSL uses. __name__ = "SSLKeyLogger" def __call__(self, connection, where, ret): if where == SSL.SSL_CB_HANDSHAKE_DONE and ret == 1: with self.lock: if not self.f: d = os.path.dirname(self.filename) if not os.path.isdir(d): os.makedirs(d) self.f = open(self.filename, "ab") self.f.write(b"\r\n") client_random = binascii.hexlify(connection.client_random()) masterkey = binascii.hexlify(connection.master_key()) self.f.write(b"CLIENT_RANDOM %s %s\r\n" % (client_random, masterkey)) self.f.flush() def close(self): with self.lock: if self.f: self.f.close() @staticmethod def create_logfun(filename): if filename: return SSLKeyLogger(filename) return False log_ssl_key = SSLKeyLogger.create_logfun( os.getenv("MITMPROXY_SSLKEYLOGFILE") or os.getenv("SSLKEYLOGFILE")) class _FileLike(object): BLOCKSIZE = 1024 * 32 def __init__(self, o): self.o = o self._log = None self.first_byte_timestamp = None def set_descriptor(self, o): self.o = o def __getattr__(self, attr): return getattr(self.o, attr) def start_log(self): """ Starts or resets the log. This will store all bytes read or written. """ self._log = [] def stop_log(self): """ Stops the log. """ self._log = None def is_logging(self): return self._log is not None def get_log(self): """ Returns the log as a string. """ if not self.is_logging(): raise ValueError("Not logging!") return b"".join(self._log) def add_log(self, v): if self.is_logging(): self._log.append(v) def reset_timestamps(self): self.first_byte_timestamp = None class Writer(_FileLike): def flush(self): """ May raise exceptions.TcpDisconnect """ if hasattr(self.o, "flush"): try: self.o.flush() except (socket.error, IOError) as v: raise exceptions.TcpDisconnect(str(v)) def write(self, v): """ May raise exceptions.TcpDisconnect """ if v: self.first_byte_timestamp = self.first_byte_timestamp or time.time() try: if hasattr(self.o, "sendall"): self.add_log(v) return self.o.sendall(v) else: r = self.o.write(v) self.add_log(v[:r]) return r except (SSL.Error, socket.error) as e: raise exceptions.TcpDisconnect(str(e)) class Reader(_FileLike): def read(self, length): """ If length is -1, we read until connection closes. """ result = b'' start = time.time() while length == -1 or length > 0: if length == -1 or length > self.BLOCKSIZE: rlen = self.BLOCKSIZE else: rlen = length try: data = self.o.read(rlen) except SSL.ZeroReturnError: # TLS connection was shut down cleanly break except (SSL.WantWriteError, SSL.WantReadError): # From the OpenSSL docs: # If the underlying BIO is non-blocking, SSL_read() will also return when the # underlying BIO could not satisfy the needs of SSL_read() to continue the # operation. In this case a call to SSL_get_error with the return value of # SSL_read() will yield SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE. if (time.time() - start) < self.o.gettimeout(): time.sleep(0.1) continue else: raise exceptions.TcpTimeout() except socket.timeout: raise exceptions.TcpTimeout() except socket.error as e: raise exceptions.TcpDisconnect(str(e)) except SSL.SysCallError as e: if e.args == (-1, 'Unexpected EOF'): break raise exceptions.TlsException(str(e)) except SSL.Error as e: raise exceptions.TlsException(str(e)) self.first_byte_timestamp = self.first_byte_timestamp or time.time() if not data: break result += data if length != -1: length -= len(data) self.add_log(result) return result def readline(self, size=None): result = b'' bytes_read = 0 while True: if size is not None and bytes_read >= size: break ch = self.read(1) bytes_read += 1 if not ch: break else: result += ch if ch == b'\n': break return result def safe_read(self, length): """ Like .read, but is guaranteed to either return length bytes, or raise an exception. """ result = self.read(length) if length != -1 and len(result) != length: if not result: raise exceptions.TcpDisconnect() else: raise exceptions.TcpReadIncomplete( "Expected %s bytes, got %s" % (length, len(result)) ) return result def peek(self, length): """ Tries to peek into the underlying file object. Returns: Up to the next N bytes if peeking is successful. Raises: exceptions.TcpException if there was an error with the socket TlsException if there was an error with pyOpenSSL. NotImplementedError if the underlying file object is not a [pyOpenSSL] socket """ if isinstance(self.o, socket_fileobject): try: return self.o._sock.recv(length, socket.MSG_PEEK) except socket.error as e: raise exceptions.TcpException(repr(e)) elif isinstance(self.o, SSL.Connection): try: if tuple(int(x) for x in OpenSSL.__version__.split(".")[:2]) > (0, 15): return self.o.recv(length, socket.MSG_PEEK) else: # TODO: remove once a new version is released # Polyfill for pyOpenSSL <= 0.15.1 # Taken from https://github.com/pyca/pyopenssl/commit/1d95dea7fea03c7c0df345a5ea30c12d8a0378d2 buf = SSL._ffi.new("char[]", length) result = SSL._lib.SSL_peek(self.o._ssl, buf, length) self.o._raise_ssl_error(self.o._ssl, result) return SSL._ffi.buffer(buf, result)[:] except SSL.Error as e: six.reraise(exceptions.TlsException, exceptions.TlsException(str(e)), sys.exc_info()[2]) else: raise NotImplementedError("Can only peek into (pyOpenSSL) sockets") class Address(basetypes.Serializable): """ This class wraps an IPv4/IPv6 tuple to provide named attributes and ipv6 information. """ def __init__(self, address, use_ipv6=False): self.address = tuple(address) self.use_ipv6 = use_ipv6 def get_state(self): return { "address": self.address, "use_ipv6": self.use_ipv6 } def set_state(self, state): self.address = state["address"] self.use_ipv6 = state["use_ipv6"] @classmethod def from_state(cls, state): return Address(**state) @classmethod def wrap(cls, t): if isinstance(t, cls): return t else: return cls(t) def __call__(self): return self.address @property def host(self): return self.address[0] @property def port(self): return self.address[1] @property def use_ipv6(self): return self.family == socket.AF_INET6 @use_ipv6.setter def use_ipv6(self, b): self.family = socket.AF_INET6 if b else socket.AF_INET def __repr__(self): return "{}:{}".format(self.host, self.port) def __eq__(self, other): if not other: return False other = Address.wrap(other) return (self.address, self.family) == (other.address, other.family) def __ne__(self, other): return not self.__eq__(other) def __hash__(self): return hash(self.address) ^ 42 # different hash than the tuple alone. def ssl_read_select(rlist, timeout): """ This is a wrapper around select.select() which also works for SSL.Connections by taking ssl_connection.pending() into account. Caveats: If .pending() > 0 for any of the connections in rlist, we avoid the select syscall and **will not include any other connections which may or may not be ready**. Args: rlist: wait until ready for reading Returns: subset of rlist which is ready for reading. """ return [ conn for conn in rlist if isinstance(conn, SSL.Connection) and conn.pending() > 0 ] or select.select(rlist, (), (), timeout)[0] def close_socket(sock): """ Does a hard close of a socket, without emitting a RST. """ try: # We already indicate that we close our end. # may raise "Transport endpoint is not connected" on Linux sock.shutdown(socket.SHUT_WR) # Section 4.2.2.13 of RFC 1122 tells us that a close() with any pending # readable data could lead to an immediate RST being sent (which is the # case on Windows). # http://ia600609.us.archive.org/22/items/TheUltimateSo_lingerPageOrWhyIsMyTcpNotReliable/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable.html # # This in turn results in the following issue: If we send an error page # to the client and then close the socket, the RST may be received by # the client before the error page and the users sees a connection # error rather than the error page. Thus, we try to empty the read # buffer on Windows first. (see # https://github.com/mitmproxy/mitmproxy/issues/527#issuecomment-93782988) # if os.name == "nt": # pragma: no cover # We cannot rely on the shutdown()-followed-by-read()-eof technique # proposed by the page above: Some remote machines just don't send # a TCP FIN, which would leave us in the unfortunate situation that # recv() would block infinitely. As a workaround, we set a timeout # here even if we are in blocking mode. sock.settimeout(sock.gettimeout() or 20) # limit at a megabyte so that we don't read infinitely for _ in range(1024 ** 3 // 4096): # may raise a timeout/disconnect exception. if not sock.recv(4096): break # Now we can close the other half as well. sock.shutdown(socket.SHUT_RD) except socket.error: pass sock.close() class _Connection(object): rbufsize = -1 wbufsize = -1 def _makefile(self): """ Set up .rfile and .wfile attributes from .connection """ # Ideally, we would use the Buffered IO in Python 3 by default. # Unfortunately, the implementation of .peek() is broken for n>1 bytes, # as it may just return what's left in the buffer and not all the bytes we want. # As a workaround, we just use unbuffered sockets directly. # https://mail.python.org/pipermail/python-dev/2009-June/089986.html if six.PY2: self.rfile = Reader(self.connection.makefile('rb', self.rbufsize)) self.wfile = Writer(self.connection.makefile('wb', self.wbufsize)) else: self.rfile = Reader(socket.SocketIO(self.connection, "rb")) self.wfile = Writer(socket.SocketIO(self.connection, "wb")) def __init__(self, connection): if connection: self.connection = connection self.ip_address = Address(connection.getpeername()) self._makefile() else: self.connection = None self.ip_address = None self.rfile = None self.wfile = None self.ssl_established = False self.finished = False def get_current_cipher(self): if not self.ssl_established: return None name = self.connection.get_cipher_name() bits = self.connection.get_cipher_bits() version = self.connection.get_cipher_version() return name, bits, version def finish(self): self.finished = True # If we have an SSL connection, wfile.close == connection.close # (We call _FileLike.set_descriptor(conn)) # Closing the socket is not our task, therefore we don't call close # then. if not isinstance(self.connection, SSL.Connection): if not getattr(self.wfile, "closed", False): try: self.wfile.flush() self.wfile.close() except exceptions.TcpDisconnect: pass self.rfile.close() else: try: self.connection.shutdown() except SSL.Error: pass def _create_ssl_context(self, method=SSL_DEFAULT_METHOD, options=SSL_DEFAULT_OPTIONS, verify_options=SSL.VERIFY_NONE, ca_path=None, ca_pemfile=None, cipher_list=None, alpn_protos=None, alpn_select=None, alpn_select_callback=None, ): """ Creates an SSL Context. :param method: One of SSLv2_METHOD, SSLv3_METHOD, SSLv23_METHOD, TLSv1_METHOD, TLSv1_1_METHOD, or TLSv1_2_METHOD :param options: A bit field consisting of OpenSSL.SSL.OP_* values :param verify_options: A bit field consisting of OpenSSL.SSL.VERIFY_* values :param ca_path: Path to a directory of trusted CA certificates prepared using the c_rehash tool :param ca_pemfile: Path to a PEM formatted trusted CA certificate :param cipher_list: A textual OpenSSL cipher list, see https://www.openssl.org/docs/apps/ciphers.html :rtype : SSL.Context """ context = SSL.Context(method) # Options (NO_SSLv2/3) if options is not None: context.set_options(options) # Verify Options (NONE/PEER and trusted CAs) if verify_options is not None: def verify_cert(conn, x509, errno, err_depth, is_cert_verified): if not is_cert_verified: self.ssl_verification_error = dict(errno=errno, depth=err_depth) return is_cert_verified context.set_verify(verify_options, verify_cert) if ca_path is None and ca_pemfile is None: ca_pemfile = certifi.where() context.load_verify_locations(ca_pemfile, ca_path) # Workaround for # https://github.com/pyca/pyopenssl/issues/190 # https://github.com/mitmproxy/mitmproxy/issues/472 # Options already set before are not cleared. context.set_mode(SSL._lib.SSL_MODE_AUTO_RETRY) # Cipher List if cipher_list: try: context.set_cipher_list(cipher_list) # TODO: maybe change this to with newer pyOpenSSL APIs context.set_tmp_ecdh(OpenSSL.crypto.get_elliptic_curve('prime256v1')) except SSL.Error as v: raise exceptions.TlsException("SSL cipher specification error: %s" % str(v)) # SSLKEYLOGFILE if log_ssl_key: context.set_info_callback(log_ssl_key) if HAS_ALPN: if alpn_protos is not None: # advertise application layer protocols context.set_alpn_protos(alpn_protos) elif alpn_select is not None and alpn_select_callback is None: # select application layer protocol def alpn_select_callback(conn_, options): if alpn_select in options: return bytes(alpn_select) else: # pragma no cover return options[0] context.set_alpn_select_callback(alpn_select_callback) elif alpn_select_callback is not None and alpn_select is None: context.set_alpn_select_callback(alpn_select_callback) elif alpn_select_callback is not None and alpn_select is not None: raise exceptions.TlsException("ALPN error: only define alpn_select (string) OR alpn_select_callback (method).") return context @contextlib.contextmanager def _closer(client): try: yield finally: client.close() class TCPClient(_Connection): def __init__(self, address, source_address=None): super(TCPClient, self).__init__(None) self.address = address self.source_address = source_address self.cert = None self.server_certs = [] self.ssl_verification_error = None self.sni = None @property def address(self): return self.__address @address.setter def address(self, address): if address: self.__address = Address.wrap(address) else: self.__address = None @property def source_address(self): return self.__source_address @source_address.setter def source_address(self, source_address): if source_address: self.__source_address = Address.wrap(source_address) else: self.__source_address = None def close(self): # Make sure to close the real socket, not the SSL proxy. # OpenSSL is really good at screwing up, i.e. when trying to recv from a failed connection, # it tries to renegotiate... if isinstance(self.connection, SSL.Connection): close_socket(self.connection._socket) else: close_socket(self.connection) def create_ssl_context(self, cert=None, alpn_protos=None, **sslctx_kwargs): context = self._create_ssl_context( alpn_protos=alpn_protos, **sslctx_kwargs) # Client Certs if cert: try: context.use_privatekey_file(cert) context.use_certificate_file(cert) except SSL.Error as v: raise exceptions.TlsException("SSL client certificate error: %s" % str(v)) return context def convert_to_ssl(self, sni=None, alpn_protos=None, **sslctx_kwargs): """ cert: Path to a file containing both client cert and private key. options: A bit field consisting of OpenSSL.SSL.OP_* values verify_options: A bit field consisting of OpenSSL.SSL.VERIFY_* values ca_path: Path to a directory of trusted CA certificates prepared using the c_rehash tool ca_pemfile: Path to a PEM formatted trusted CA certificate """ verification_mode = sslctx_kwargs.get('verify_options', None) if verification_mode == SSL.VERIFY_PEER and not sni: raise exceptions.TlsException("Cannot validate certificate hostname without SNI") context = self.create_ssl_context( alpn_protos=alpn_protos, **sslctx_kwargs ) self.connection = SSL.Connection(context, self.connection) if sni: self.sni = sni self.connection.set_tlsext_host_name(sni) self.connection.set_connect_state() try: self.connection.do_handshake() except SSL.Error as v: if self.ssl_verification_error: raise exceptions.InvalidCertificateException("SSL handshake error: %s" % repr(v)) else: raise exceptions.TlsException("SSL handshake error: %s" % repr(v)) else: # Fix for pre v1.0 OpenSSL, which doesn't throw an exception on # certificate validation failure if verification_mode == SSL.VERIFY_PEER and self.ssl_verification_error is not None: raise exceptions.InvalidCertificateException("SSL handshake error: certificate verify failed") self.cert = certutils.SSLCert(self.connection.get_peer_certificate()) # Keep all server certificates in a list for i in self.connection.get_peer_cert_chain(): self.server_certs.append(certutils.SSLCert(i)) # Validate TLS Hostname try: crt = dict( subjectAltName=[("DNS", x.decode("ascii", "strict")) for x in self.cert.altnames] ) if self.cert.cn: crt["subject"] = [[["commonName", self.cert.cn.decode("ascii", "strict")]]] if sni: hostname = sni.decode("ascii", "strict") else: hostname = "no-hostname" ssl_match_hostname.match_hostname(crt, hostname) except (ValueError, ssl_match_hostname.CertificateError) as e: self.ssl_verification_error = dict(depth=0, errno="Invalid Hostname") if verification_mode == SSL.VERIFY_PEER: raise exceptions.InvalidCertificateException("Presented certificate for {} is not valid: {}".format(sni, str(e))) self.ssl_established = True self.rfile.set_descriptor(self.connection) self.wfile.set_descriptor(self.connection) def connect(self): try: connection = socket.socket(self.address.family, socket.SOCK_STREAM) if self.source_address: connection.bind(self.source_address()) connection.connect(self.address()) self.source_address = Address(connection.getsockname()) except (socket.error, IOError) as err: raise exceptions.TcpException( 'Error connecting to "%s": %s' % (self.address.host, err)) self.connection = connection self.ip_address = Address(connection.getpeername()) self._makefile() return _closer(self) def settimeout(self, n): self.connection.settimeout(n) def gettimeout(self): return self.connection.gettimeout() def get_alpn_proto_negotiated(self): if HAS_ALPN and self.ssl_established: return self.connection.get_alpn_proto_negotiated() else: return b"" class BaseHandler(_Connection): """ The instantiator is expected to call the handle() and finish() methods. """ def __init__(self, connection, address, server): super(BaseHandler, self).__init__(connection) self.address = Address.wrap(address) self.server = server self.clientcert = None def create_ssl_context(self, cert, key, handle_sni=None, request_client_cert=None, chain_file=None, dhparams=None, extra_chain_certs=None, **sslctx_kwargs): """ cert: A certutils.SSLCert object or the path to a certificate chain file. handle_sni: SNI handler, should take a connection object. Server name can be retrieved like this: connection.get_servername() And you can specify the connection keys as follows: new_context = Context(TLSv1_METHOD) new_context.use_privatekey(key) new_context.use_certificate(cert) connection.set_context(new_context) The request_client_cert argument requires some explanation. We're supposed to be able to do this with no negative effects - if the client has no cert to present, we're notified and proceed as usual. Unfortunately, Android seems to have a bug (tested on 4.2.2) - when an Android client is asked to present a certificate it does not have, it hangs up, which is frankly bogus. Some time down the track we may be able to make the proper behaviour the default again, but until then we're conservative. """ context = self._create_ssl_context(**sslctx_kwargs) context.use_privatekey(key) if isinstance(cert, certutils.SSLCert): context.use_certificate(cert.x509) else: context.use_certificate_chain_file(cert) if extra_chain_certs: for i in extra_chain_certs: context.add_extra_chain_cert(i.x509) if handle_sni: # SNI callback happens during do_handshake() context.set_tlsext_servername_callback(handle_sni) if request_client_cert: def save_cert(conn_, cert, errno_, depth_, preverify_ok_): self.clientcert = certutils.SSLCert(cert) # Return true to prevent cert verification error return True context.set_verify(SSL.VERIFY_PEER, save_cert) # Cert Verify if chain_file: context.load_verify_locations(chain_file) if dhparams: SSL._lib.SSL_CTX_set_tmp_dh(context._context, dhparams) return context def convert_to_ssl(self, cert, key, **sslctx_kwargs): """ Convert connection to SSL. For a list of parameters, see BaseHandler._create_ssl_context(...) """ context = self.create_ssl_context( cert, key, **sslctx_kwargs) self.connection = SSL.Connection(context, self.connection) self.connection.set_accept_state() try: self.connection.do_handshake() except SSL.Error as v: raise exceptions.TlsException("SSL handshake error: %s" % repr(v)) self.ssl_established = True self.rfile.set_descriptor(self.connection) self.wfile.set_descriptor(self.connection) def handle(self): # pragma: no cover raise NotImplementedError def settimeout(self, n): self.connection.settimeout(n) def get_alpn_proto_negotiated(self): if HAS_ALPN and self.ssl_established: return self.connection.get_alpn_proto_negotiated() else: return b"" class Counter: def __init__(self): self._count = 0 self._lock = threading.Lock() @property def count(self): with self._lock: return self._count def __enter__(self): with self._lock: self._count += 1 def __exit__(self, *args): with self._lock: self._count -= 1 class TCPServer(object): request_queue_size = 20 def __init__(self, address): self.address = Address.wrap(address) self.__is_shut_down = threading.Event() self.__shutdown_request = False self.socket = socket.socket(self.address.family, socket.SOCK_STREAM) self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.socket.bind(self.address()) self.address = Address.wrap(self.socket.getsockname()) self.socket.listen(self.request_queue_size) self.handler_counter = Counter() def connection_thread(self, connection, client_address): with self.handler_counter: client_address = Address(client_address) try: self.handle_client_connection(connection, client_address) except: self.handle_error(connection, client_address) finally: close_socket(connection) def serve_forever(self, poll_interval=0.1): self.__is_shut_down.clear() try: while not self.__shutdown_request: try: r, w_, e_ = select.select( [self.socket], [], [], poll_interval) except select.error as ex: # pragma: no cover if ex[0] == EINTR: continue else: raise if self.socket in r: connection, client_address = self.socket.accept() t = threading.Thread( target=self.connection_thread, args=(connection, client_address), name="ConnectionThread (%s:%s -> %s:%s)" % (client_address[0], client_address[1], self.address.host, self.address.port) ) t.setDaemon(1) try: t.start() except threading.ThreadError: self.handle_error(connection, Address(client_address)) connection.close() finally: self.__shutdown_request = False self.__is_shut_down.set() def shutdown(self): self.__shutdown_request = True self.__is_shut_down.wait() self.socket.close() self.handle_shutdown() def handle_error(self, connection_, client_address, fp=sys.stderr): """ Called when handle_client_connection raises an exception. """ # If a thread has persisted after interpreter exit, the module might be # none. if traceback and six: exc = six.text_type(traceback.format_exc()) print(u'-' * 40, file=fp) print( u"Error in processing of request from %s" % repr(client_address), file=fp) print(exc, file=fp) print(u'-' * 40, file=fp) def handle_client_connection(self, conn, client_address): # pragma: no cover """ Called after client connection. """ raise NotImplementedError def handle_shutdown(self): """ Called after server shutdown. """