Notaries sign notebooks now

IPython/html/notebookapp.py

@@ -1,874 +1,874 b''
 # coding: utf-8
 """A tornado based IPython notebook server.
 
 Authors:
 
 * Brian Granger
 """
 from __future__ import print_function
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2013  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # stdlib
 import errno
 import io
 import json
 import logging
 import os
 import random
 import select
 import signal
 import socket
 import sys
 import threading
 import time
 import webbrowser
 
 
 # Third party
 # check for pyzmq 2.1.11
 from IPython.utils.zmqrelated import check_for_zmq
 check_for_zmq('2.1.11', 'IPython.html')
 
 from jinja2 import Environment, FileSystemLoader
 
 # Install the pyzmq ioloop. This has to be done before anything else from
 # tornado is imported.
 from zmq.eventloop import ioloop
 ioloop.install()
 
 # check for tornado 3.1.0
 msg = "The IPython Notebook requires tornado >= 3.1.0"
 try:
     import tornado
 except ImportError:
     raise ImportError(msg)
 try:
     version_info = tornado.version_info
 except AttributeError:
     raise ImportError(msg + ", but you have < 1.1.0")
 if version_info < (3,1,0):
     raise ImportError(msg + ", but you have %s" % tornado.version)
 
 from tornado import httpserver
 from tornado import web
 
 # Our own libraries
 from IPython.html import DEFAULT_STATIC_FILES_PATH
 from .base.handlers import Template404
 from .log import log_request
 from .services.kernels.kernelmanager import MappingKernelManager
 from .services.notebooks.nbmanager import NotebookManager
 from .services.notebooks.filenbmanager import FileNotebookManager
 from .services.clusters.clustermanager import ClusterManager
 from .services.sessions.sessionmanager import SessionManager
 
 from .base.handlers import AuthenticatedFileHandler, FileFindHandler
 
 from IPython.config.application import catch_config_error, boolean_flag
 from IPython.core.application import BaseIPythonApplication
 from IPython.core.profiledir import ProfileDir
 from IPython.consoleapp import IPythonConsoleApp
 from IPython.kernel import swallow_argv
 from IPython.kernel.zmq.session import default_secure
 from IPython.kernel.zmq.kernelapp import (
     kernel_flags,
     kernel_aliases,
 )
 from IPython.nbformat import current, sign
 from IPython.utils.importstring import import_item
 from IPython.utils.localinterfaces import localhost
 from IPython.utils import submodule
 from IPython.utils.traitlets import (
     Dict, Unicode, Integer, List, Bool, Bytes,
     DottedObjectName, Instance,
 )
 from IPython.utils import py3compat
 from IPython.utils.path import filefind, get_ipython_dir
 
 from .utils import url_path_join
 
 #-----------------------------------------------------------------------------
 # Module globals
 #-----------------------------------------------------------------------------
 
 _examples = """
 ipython notebook                       # start the notebook
 ipython notebook --profile=sympy       # use the sympy profile
 ipython notebook --certfile=mycert.pem # use SSL/TLS certificate
 """
 
 #-----------------------------------------------------------------------------
 # Helper functions
 #-----------------------------------------------------------------------------
 
 def random_ports(port, n):
     """Generate a list of n random ports near the given port.
 
     The first 5 ports will be sequential, and the remaining n-5 will be
     randomly selected in the range [port-2*n, port+2*n].
     """
     for i in range(min(5, n)):
         yield port + i
     for i in range(n-5):
         yield max(1, port + random.randint(-2*n, 2*n))
 
 def load_handlers(name):
     """Load the (URL pattern, handler) tuples for each component."""
     name = 'IPython.html.' + name
     mod = __import__(name, fromlist=['default_handlers'])
     return mod.default_handlers
 
 #-----------------------------------------------------------------------------
 # The Tornado web application
 #-----------------------------------------------------------------------------
 
 class NotebookWebApplication(web.Application):
 
     def __init__(self, ipython_app, kernel_manager, notebook_manager,
                  cluster_manager, session_manager, log, base_project_url,
                  settings_overrides):
 
         settings = self.init_settings(
             ipython_app, kernel_manager, notebook_manager, cluster_manager,
             session_manager, log, base_project_url, settings_overrides)
         handlers = self.init_handlers(settings)
 
         super(NotebookWebApplication, self).__init__(handlers, **settings)
 
     def init_settings(self, ipython_app, kernel_manager, notebook_manager,
                       cluster_manager, session_manager, log, base_project_url,
                       settings_overrides):
         # Python < 2.6.5 doesn't accept unicode keys in f(**kwargs), and
         # base_project_url will always be unicode, which will in turn
         # make the patterns unicode, and ultimately result in unicode
         # keys in kwargs to handler._execute(**kwargs) in tornado.
         # This enforces that base_project_url be ascii in that situation.
         # 
         # Note that the URLs these patterns check against are escaped,
         # and thus guaranteed to be ASCII: 'héllo' is really 'h%C3%A9llo'.
         base_project_url = py3compat.unicode_to_str(base_project_url, 'ascii')
         template_path = settings_overrides.get("template_path", os.path.join(os.path.dirname(__file__), "templates"))
         settings = dict(
             # basics
             log_function=log_request,
             base_project_url=base_project_url,
             base_kernel_url=ipython_app.base_kernel_url,
             template_path=template_path,
             static_path=ipython_app.static_file_path,
             static_handler_class = FileFindHandler,
             static_url_prefix = url_path_join(base_project_url,'/static/'),
             
             # authentication
             cookie_secret=ipython_app.cookie_secret,
             login_url=url_path_join(base_project_url,'/login'),
             password=ipython_app.password,
             
             # managers
             kernel_manager=kernel_manager,
             notebook_manager=notebook_manager,
             cluster_manager=cluster_manager,
             session_manager=session_manager,
 
             # IPython stuff
             nbextensions_path = ipython_app.nbextensions_path,
             mathjax_url=ipython_app.mathjax_url,
             config=ipython_app.config,
             jinja2_env=Environment(loader=FileSystemLoader(template_path)),
         )
 
         # allow custom overrides for the tornado web app.
         settings.update(settings_overrides)
         return settings
 
     def init_handlers(self, settings):
         # Load the (URL pattern, handler) tuples for each component.
         handlers = []
         handlers.extend(load_handlers('base.handlers'))
         handlers.extend(load_handlers('tree.handlers'))
         handlers.extend(load_handlers('auth.login'))
         handlers.extend(load_handlers('auth.logout'))
         handlers.extend(load_handlers('notebook.handlers'))
         handlers.extend(load_handlers('nbconvert.handlers'))
         handlers.extend(load_handlers('services.kernels.handlers'))
         handlers.extend(load_handlers('services.notebooks.handlers'))
         handlers.extend(load_handlers('services.clusters.handlers'))
         handlers.extend(load_handlers('services.sessions.handlers'))
         handlers.extend(load_handlers('services.nbconvert.handlers'))
         handlers.extend([
             (r"/files/(.*)", AuthenticatedFileHandler, {'path' : settings['notebook_manager'].notebook_dir}),
             (r"/nbextensions/(.*)", FileFindHandler, {'path' : settings['nbextensions_path']}),
         ])
         # prepend base_project_url onto the patterns that we match
         new_handlers = []
         for handler in handlers:
             pattern = url_path_join(settings['base_project_url'], handler[0])
             new_handler = tuple([pattern] + list(handler[1:]))
             new_handlers.append(new_handler)
         # add 404 on the end, which will catch everything that falls through
         new_handlers.append((r'(.*)', Template404))
         return new_handlers
 
 
 #-----------------------------------------------------------------------------
 # Subcommands
 #-----------------------------------------------------------------------------
 
 class NbserverListApp(BaseIPythonApplication):
     
     description="List currently running notebook servers in this profile."
     
     flags = dict(
         json=({'NbserverListApp': {'json': True}},
               "Produce machine-readable JSON output."),
     )
     
     json = Bool(False, config=True,
           help="If True, each line of output will be a JSON object with the "
                   "details from the server info file.")
 
     def start(self):
         if not self.json:
             print("Currently running servers:")
         for serverinfo in list_running_servers(self.profile):
             if self.json:
                 print(json.dumps(serverinfo))
             else:
                 print(serverinfo['url'], "::", serverinfo['notebook_dir'])
 
 
 class NotebookTrustApp(BaseIPythonApplication):
     
     description="""Sign one or more IPython notebooks with your key,
     to trust their dynamic (HTML, Javascript) output."""
     
     examples="""ipython notebook trust mynotebook.ipynb"""
     
     notary = Instance(sign.NotebookNotary)
     def _notary_default(self):
         return sign.NotebookNotary(parent=self, profile_dir=self.profile_dir)
     
     def sign_notebook(self, notebook_path):
         if not os.path.exists(notebook_path):
             self.log.error("Notebook missing: %s" % notebook_path)
             self.exit(1)
         with io.open(notebook_path, encoding='utf8') as f:
             nb = current.read(f, 'json')
-        sign.trust_notebook(nb, self.notary.secret, self.notary.signature_scheme)
+        self.notary.sign(nb)
         with io.open(notebook_path, 'w', encoding='utf8') as f:
             current.write(nb, f, 'json')
     
     def start(self):
         if not self.extra_args:
             self.log.critical("Specify at least one notebook to sign.")
             self.exit(1)
         
         for notebook_path in self.extra_args:
             print("Signing notebook: %s" % notebook_path)
             self.sign_notebook(notebook_path)
 
 #-----------------------------------------------------------------------------
 # Aliases and Flags
 #-----------------------------------------------------------------------------
 
 flags = dict(kernel_flags)
 flags['no-browser']=(
     {'NotebookApp' : {'open_browser' : False}},
     "Don't open the notebook in a browser after startup."
 )
 flags['no-mathjax']=(
     {'NotebookApp' : {'enable_mathjax' : False}},
     """Disable MathJax
     
     MathJax is the javascript library IPython uses to render math/LaTeX. It is
     very large, so you may want to disable it if you have a slow internet
     connection, or for offline use of the notebook.
     
     When disabled, equations etc. will appear as their untransformed TeX source.
     """
 )
 
 # Add notebook manager flags
 flags.update(boolean_flag('script', 'FileNotebookManager.save_script',
                'Auto-save a .py script everytime the .ipynb notebook is saved',
                'Do not auto-save .py scripts for every notebook'))
 
 # the flags that are specific to the frontend
 # these must be scrubbed before being passed to the kernel,
 # or it will raise an error on unrecognized flags
 notebook_flags = ['no-browser', 'no-mathjax', 'script', 'no-script']
 
 aliases = dict(kernel_aliases)
 
 aliases.update({
     'ip': 'NotebookApp.ip',
     'port': 'NotebookApp.port',
     'port-retries': 'NotebookApp.port_retries',
     'transport': 'KernelManager.transport',
     'keyfile': 'NotebookApp.keyfile',
     'certfile': 'NotebookApp.certfile',
     'notebook-dir': 'NotebookManager.notebook_dir',
     'browser': 'NotebookApp.browser',
 })
 
 # remove ipkernel flags that are singletons, and don't make sense in
 # multi-kernel evironment:
 aliases.pop('f', None)
 
 notebook_aliases = [u'port', u'port-retries', u'ip', u'keyfile', u'certfile',
                     u'notebook-dir', u'profile', u'profile-dir']
 
 #-----------------------------------------------------------------------------
 # NotebookApp
 #-----------------------------------------------------------------------------
 
 class NotebookApp(BaseIPythonApplication):
 
     name = 'ipython-notebook'
     
     description = """
         The IPython HTML Notebook.
         
         This launches a Tornado based HTML Notebook Server that serves up an
         HTML5/Javascript Notebook client.
     """
     examples = _examples
     
     classes = IPythonConsoleApp.classes + [MappingKernelManager, NotebookManager,
         FileNotebookManager]
     flags = Dict(flags)
     aliases = Dict(aliases)
     
     subcommands = dict(
         list=(NbserverListApp, NbserverListApp.description.splitlines()[0]),
         trust=(NotebookTrustApp, NotebookTrustApp.description),
     )
 
     kernel_argv = List(Unicode)
 
     def _log_level_default(self):
         return logging.INFO
 
     def _log_format_default(self):
         """override default log format to include time"""
         return u"%(asctime)s.%(msecs).03d [%(name)s]%(highlevel)s %(message)s"
 
     # create requested profiles by default, if they don't exist:
     auto_create = Bool(True)
 
     # file to be opened in the notebook server
     file_to_run = Unicode('')
 
     # Network related information.
 
     ip = Unicode(config=True,
         help="The IP address the notebook server will listen on."
     )
     def _ip_default(self):
         return localhost()
 
     def _ip_changed(self, name, old, new):
         if new == u'*': self.ip = u''
 
     port = Integer(8888, config=True,
         help="The port the notebook server will listen on."
     )
     port_retries = Integer(50, config=True,
         help="The number of additional ports to try if the specified port is not available."
     )
 
     certfile = Unicode(u'', config=True, 
         help="""The full path to an SSL/TLS certificate file."""
     )
     
     keyfile = Unicode(u'', config=True, 
         help="""The full path to a private key file for usage with SSL/TLS."""
     )
     
     cookie_secret = Bytes(b'', config=True,
         help="""The random bytes used to secure cookies.
         By default this is a new random number every time you start the Notebook.
         Set it to a value in a config file to enable logins to persist across server sessions.
         
         Note: Cookie secrets should be kept private, do not share config files with
         cookie_secret stored in plaintext (you can read the value from a file).
         """
     )
     def _cookie_secret_default(self):
         return os.urandom(1024)
 
     password = Unicode(u'', config=True,
                       help="""Hashed password to use for web authentication.
 
                       To generate, type in a python/IPython shell:
 
                         from IPython.lib import passwd; passwd()
 
                       The string should be of the form type:salt:hashed-password.
                       """
     )
 
     open_browser = Bool(True, config=True,
                         help="""Whether to open in a browser after starting.
                         The specific browser used is platform dependent and
                         determined by the python standard library `webbrowser`
                         module, unless it is overridden using the --browser
                         (NotebookApp.browser) configuration option.
                         """)
 
     browser = Unicode(u'', config=True,
                       help="""Specify what command to use to invoke a web
                       browser when opening the notebook. If not specified, the
                       default browser will be determined by the `webbrowser`
                       standard library module, which allows setting of the
                       BROWSER environment variable to override it.
                       """)
     
     webapp_settings = Dict(config=True,
             help="Supply overrides for the tornado.web.Application that the "
                  "IPython notebook uses.")
     
     enable_mathjax = Bool(True, config=True,
         help="""Whether to enable MathJax for typesetting math/TeX
 
         MathJax is the javascript library IPython uses to render math/LaTeX. It is
         very large, so you may want to disable it if you have a slow internet
         connection, or for offline use of the notebook.
 
         When disabled, equations etc. will appear as their untransformed TeX source.
         """
     )
     def _enable_mathjax_changed(self, name, old, new):
         """set mathjax url to empty if mathjax is disabled"""
         if not new:
             self.mathjax_url = u''
 
     base_project_url = Unicode('/', config=True,
                                help='''The base URL for the notebook server.
 
                                Leading and trailing slashes can be omitted,
                                and will automatically be added.
                                ''')
     def _base_project_url_changed(self, name, old, new):
         if not new.startswith('/'):
             self.base_project_url = '/'+new
         elif not new.endswith('/'):
             self.base_project_url = new+'/'
 
     base_kernel_url = Unicode('/', config=True,
                                help='''The base URL for the kernel server
 
                                Leading and trailing slashes can be omitted,
                                and will automatically be added.
                                ''')
     def _base_kernel_url_changed(self, name, old, new):
         if not new.startswith('/'):
             self.base_kernel_url = '/'+new
         elif not new.endswith('/'):
             self.base_kernel_url = new+'/'
 
     websocket_url = Unicode("", config=True,
         help="""The base URL for the websocket server,
         if it differs from the HTTP server (hint: it almost certainly doesn't).
         
         Should be in the form of an HTTP origin: ws[s]://hostname[:port]
         """
     )
 
     extra_static_paths = List(Unicode, config=True,
         help="""Extra paths to search for serving static files.
         
         This allows adding javascript/css to be available from the notebook server machine,
         or overriding individual files in the IPython"""
     )
     def _extra_static_paths_default(self):
         return [os.path.join(self.profile_dir.location, 'static')]
     
     @property
     def static_file_path(self):
         """return extra paths + the default location"""
         return self.extra_static_paths + [DEFAULT_STATIC_FILES_PATH]
     
     nbextensions_path = List(Unicode, config=True,
         help="""paths for Javascript extensions. By default, this is just IPYTHONDIR/nbextensions"""
     )
     def _nbextensions_path_default(self):
         return [os.path.join(get_ipython_dir(), 'nbextensions')]
 
     mathjax_url = Unicode("", config=True,
         help="""The url for MathJax.js."""
     )
     def _mathjax_url_default(self):
         if not self.enable_mathjax:
             return u''
         static_url_prefix = self.webapp_settings.get("static_url_prefix",
                          url_path_join(self.base_project_url, "static")
         )
         
         # try local mathjax, either in nbextensions/mathjax or static/mathjax
         for (url_prefix, search_path) in [
             (url_path_join(self.base_project_url, "nbextensions"), self.nbextensions_path),
             (static_url_prefix, self.static_file_path),
         ]:
             self.log.debug("searching for local mathjax in %s", search_path)
             try:
                 mathjax = filefind(os.path.join('mathjax', 'MathJax.js'), search_path)
             except IOError:
                 continue
             else:
                 url = url_path_join(url_prefix, u"mathjax/MathJax.js")
                 self.log.info("Serving local MathJax from %s at %s", mathjax, url)
                 return url
         
         # no local mathjax, serve from CDN
         if self.certfile:
             # HTTPS: load from Rackspace CDN, because SSL certificate requires it
             host = u"https://c328740.ssl.cf1.rackcdn.com"
         else:
             host = u"http://cdn.mathjax.org"
         
         url = host + u"/mathjax/latest/MathJax.js"
         self.log.info("Using MathJax from CDN: %s", url)
         return url
     
     def _mathjax_url_changed(self, name, old, new):
         if new and not self.enable_mathjax:
             # enable_mathjax=False overrides mathjax_url
             self.mathjax_url = u''
         else:
             self.log.info("Using MathJax: %s", new)
 
     notebook_manager_class = DottedObjectName('IPython.html.services.notebooks.filenbmanager.FileNotebookManager',
         config=True,
         help='The notebook manager class to use.')
 
     trust_xheaders = Bool(False, config=True,
         help=("Whether to trust or not X-Scheme/X-Forwarded-Proto and X-Real-Ip/X-Forwarded-For headers"
               "sent by the upstream reverse proxy. Necessary if the proxy handles SSL")
     )
     
     info_file = Unicode()
 
     def _info_file_default(self):
         info_file = "nbserver-%s.json"%os.getpid()
         return os.path.join(self.profile_dir.security_dir, info_file)
 
     def parse_command_line(self, argv=None):
         super(NotebookApp, self).parse_command_line(argv)
         
         if self.extra_args:
             arg0 = self.extra_args[0]
             f = os.path.abspath(arg0)
             self.argv.remove(arg0)
             if not os.path.exists(f):
                 self.log.critical("No such file or directory: %s", f)
                 self.exit(1)
             if os.path.isdir(f):
                 self.config.FileNotebookManager.notebook_dir = f
             elif os.path.isfile(f):
                 self.file_to_run = f
 
     def init_kernel_argv(self):
         """construct the kernel arguments"""
         # Scrub frontend-specific flags
         self.kernel_argv = swallow_argv(self.argv, notebook_aliases, notebook_flags)
         if any(arg.startswith(u'--pylab') for arg in self.kernel_argv):
             self.log.warn('\n    '.join([
                 "Starting all kernels in pylab mode is not recommended,",
                 "and will be disabled in a future release.",
                 "Please use the %matplotlib magic to enable matplotlib instead.",
                 "pylab implies many imports, which can have confusing side effects",
                 "and harm the reproducibility of your notebooks.",
             ]))
         # Kernel should inherit default config file from frontend
         self.kernel_argv.append("--IPKernelApp.parent_appname='%s'" % self.name)
         # Kernel should get *absolute* path to profile directory
         self.kernel_argv.extend(["--profile-dir", self.profile_dir.location])
 
     def init_configurables(self):
         # force Session default to be secure
         default_secure(self.config)
         self.kernel_manager = MappingKernelManager(
             parent=self, log=self.log, kernel_argv=self.kernel_argv,
             connection_dir = self.profile_dir.security_dir,
         )
         kls = import_item(self.notebook_manager_class)
         self.notebook_manager = kls(parent=self, log=self.log)
         self.session_manager = SessionManager(parent=self, log=self.log)
         self.cluster_manager = ClusterManager(parent=self, log=self.log)
         self.cluster_manager.update_profiles()
 
     def init_logging(self):
         # This prevents double log messages because tornado use a root logger that
         # self.log is a child of. The logging module dipatches log messages to a log
         # and all of its ancenstors until propagate is set to False.
         self.log.propagate = False
         
         # hook up tornado 3's loggers to our app handlers
         for name in ('access', 'application', 'general'):
             logger = logging.getLogger('tornado.%s' % name)
             logger.parent = self.log
             logger.setLevel(self.log.level)
     
     def init_webapp(self):
         """initialize tornado webapp and httpserver"""
         self.web_app = NotebookWebApplication(
             self, self.kernel_manager, self.notebook_manager, 
             self.cluster_manager, self.session_manager,
             self.log, self.base_project_url, self.webapp_settings
         )
         if self.certfile:
             ssl_options = dict(certfile=self.certfile)
             if self.keyfile:
                 ssl_options['keyfile'] = self.keyfile
         else:
             ssl_options = None
         self.web_app.password = self.password
         self.http_server = httpserver.HTTPServer(self.web_app, ssl_options=ssl_options,
                                                  xheaders=self.trust_xheaders)
         if not self.ip:
             warning = "WARNING: The notebook server is listening on all IP addresses"
             if ssl_options is None:
                 self.log.critical(warning + " and not using encryption. This "
                     "is not recommended.")
             if not self.password:
                 self.log.critical(warning + " and not using authentication. "
                     "This is highly insecure and not recommended.")
         success = None
         for port in random_ports(self.port, self.port_retries+1):
             try:
                 self.http_server.listen(port, self.ip)
             except socket.error as e:
                 if e.errno == errno.EADDRINUSE:
                     self.log.info('The port %i is already in use, trying another random port.' % port)
                     continue
                 elif e.errno in (errno.EACCES, getattr(errno, 'WSAEACCES', errno.EACCES)):
                     self.log.warn("Permission to listen on port %i denied" % port)
                     continue
                 else:
                     raise
             else:
                 self.port = port
                 success = True
                 break
         if not success:
             self.log.critical('ERROR: the notebook server could not be started because '
                               'no available port could be found.')
             self.exit(1)
     
     @property
     def display_url(self):
         ip = self.ip if self.ip else '[all ip addresses on your system]'
         return self._url(ip)
 
     @property
     def connection_url(self):
         ip = self.ip if self.ip else localhost()
         return self._url(ip)
 
     def _url(self, ip):
         proto = 'https' if self.certfile else 'http'
         return "%s://%s:%i%s" % (proto, ip, self.port, self.base_project_url)
 
     def init_signal(self):
         if not sys.platform.startswith('win'):
             signal.signal(signal.SIGINT, self._handle_sigint)
         signal.signal(signal.SIGTERM, self._signal_stop)
         if hasattr(signal, 'SIGUSR1'):
             # Windows doesn't support SIGUSR1
             signal.signal(signal.SIGUSR1, self._signal_info)
         if hasattr(signal, 'SIGINFO'):
             # only on BSD-based systems
             signal.signal(signal.SIGINFO, self._signal_info)
     
     def _handle_sigint(self, sig, frame):
         """SIGINT handler spawns confirmation dialog"""
         # register more forceful signal handler for ^C^C case
         signal.signal(signal.SIGINT, self._signal_stop)
         # request confirmation dialog in bg thread, to avoid
         # blocking the App
         thread = threading.Thread(target=self._confirm_exit)
         thread.daemon = True
         thread.start()
     
     def _restore_sigint_handler(self):
         """callback for restoring original SIGINT handler"""
         signal.signal(signal.SIGINT, self._handle_sigint)
     
     def _confirm_exit(self):
         """confirm shutdown on ^C
         
         A second ^C, or answering 'y' within 5s will cause shutdown,
         otherwise original SIGINT handler will be restored.
         
         This doesn't work on Windows.
         """
         # FIXME: remove this delay when pyzmq dependency is >= 2.1.11
         time.sleep(0.1)
         info = self.log.info
         info('interrupted')
         print(self.notebook_info())
         sys.stdout.write("Shutdown this notebook server (y/[n])? ")
         sys.stdout.flush()
         r,w,x = select.select([sys.stdin], [], [], 5)
         if r:
             line = sys.stdin.readline()
             if line.lower().startswith('y'):
                 self.log.critical("Shutdown confirmed")
                 ioloop.IOLoop.instance().stop()
                 return
         else:
             print("No answer for 5s:", end=' ')
         print("resuming operation...")
         # no answer, or answer is no:
         # set it back to original SIGINT handler
         # use IOLoop.add_callback because signal.signal must be called
         # from main thread
         ioloop.IOLoop.instance().add_callback(self._restore_sigint_handler)
     
     def _signal_stop(self, sig, frame):
         self.log.critical("received signal %s, stopping", sig)
         ioloop.IOLoop.instance().stop()
 
     def _signal_info(self, sig, frame):
         print(self.notebook_info())
     
     def init_components(self):
         """Check the components submodule, and warn if it's unclean"""
         status = submodule.check_submodule_status()
         if status == 'missing':
             self.log.warn("components submodule missing, running `git submodule update`")
             submodule.update_submodules(submodule.ipython_parent())
         elif status == 'unclean':
             self.log.warn("components submodule unclean, you may see 404s on static/components")
             self.log.warn("run `setup.py submodule` or `git submodule update` to update")
     
     @catch_config_error
     def initialize(self, argv=None):
         super(NotebookApp, self).initialize(argv)
         self.init_logging()
         self.init_kernel_argv()
         self.init_configurables()
         self.init_components()
         self.init_webapp()
         self.init_signal()
 
     def cleanup_kernels(self):
         """Shutdown all kernels.
         
         The kernels will shutdown themselves when this process no longer exists,
         but explicit shutdown allows the KernelManagers to cleanup the connection files.
         """
         self.log.info('Shutting down kernels')
         self.kernel_manager.shutdown_all()
 
     def notebook_info(self):
         "Return the current working directory and the server url information"
         info = self.notebook_manager.info_string() + "\n"
         info += "%d active kernels \n" % len(self.kernel_manager._kernels)
         return info + "The IPython Notebook is running at: %s" % self.display_url
 
     def server_info(self):
         """Return a JSONable dict of information about this server."""
         return {'url': self.connection_url,
                 'hostname': self.ip if self.ip else 'localhost',
                 'port': self.port,
                 'secure': bool(self.certfile),
                 'base_project_url': self.base_project_url,
                 'notebook_dir': os.path.abspath(self.notebook_manager.notebook_dir),
                }
 
     def write_server_info_file(self):
         """Write the result of server_info() to the JSON file info_file."""
         with open(self.info_file, 'w') as f:
             json.dump(self.server_info(), f, indent=2)
 
     def remove_server_info_file(self):
         """Remove the nbserver-<pid>.json file created for this server.
         
         Ignores the error raised when the file has already been removed.
         """
         try:
             os.unlink(self.info_file)
         except OSError as e:
             if e.errno != errno.ENOENT:
                 raise
 
     def start(self):
         """ Start the IPython Notebook server app, after initialization
         
         This method takes no arguments so all configuration and initialization
         must be done prior to calling this method."""
         if self.subapp is not None:
             return self.subapp.start()
 
         info = self.log.info
         for line in self.notebook_info().split("\n"):
             info(line)
         info("Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).")
 
         self.write_server_info_file()
 
         if self.open_browser or self.file_to_run:
             try:
                 browser = webbrowser.get(self.browser or None)
             except webbrowser.Error as e:
                 self.log.warn('No web browser found: %s.' % e)
                 browser = None
             
             f = self.file_to_run
             if f:
                 nbdir = os.path.abspath(self.notebook_manager.notebook_dir)
                 if f.startswith(nbdir):
                     f = f[len(nbdir):]
                 else:
                     self.log.warn(
                         "Probably won't be able to open notebook %s "
                         "because it is not in notebook_dir %s",
                         f, nbdir,
                     )
 
             if os.path.isfile(self.file_to_run):
                 url = url_path_join('notebooks', f)
             else:
                 url = url_path_join('tree', f)
             if browser:
                 b = lambda : browser.open("%s%s" % (self.connection_url, url),
                                           new=2)
                 threading.Thread(target=b).start()
         try:
             ioloop.IOLoop.instance().start()
         except KeyboardInterrupt:
             info("Interrupted...")
         finally:
             self.cleanup_kernels()
             self.remove_server_info_file()
 
 
 def list_running_servers(profile='default'):
     """Iterate over the server info files of running notebook servers.
     
     Given a profile name, find nbserver-* files in the security directory of
     that profile, and yield dicts of their information, each one pertaining to
     a currently running notebook server instance.
     """
     pd = ProfileDir.find_profile_dir_by_name(get_ipython_dir(), name=profile)
     for file in os.listdir(pd.security_dir):
         if file.startswith('nbserver-'):
             with io.open(os.path.join(pd.security_dir, file), encoding='utf-8') as f:
                 yield json.load(f)
 
 #-----------------------------------------------------------------------------
 # Main entry point
 #-----------------------------------------------------------------------------
 
 launch_new_instance = NotebookApp.launch_instance
 

IPython/html/services/notebooks/filenbmanager.py

@@ -1,419 +1,425 b''
 """A notebook manager that uses the local file system for storage.
 
 Authors:
 
 * Brian Granger
 * Zach Sailer
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import io
 import itertools
 import os
 import glob
 import shutil
 
 from tornado import web
 
 from .nbmanager import NotebookManager
 from IPython.nbformat import current, sign
 from IPython.utils.traitlets import Unicode, Dict, Bool, TraitError
 from IPython.utils import tz
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class FileNotebookManager(NotebookManager):
     
     save_script = Bool(False, config=True,
         help="""Automatically create a Python script when saving the notebook.
         
         For easier use of import, %run and %load across notebooks, a
         <notebook-name>.py script will be created next to any
         <notebook-name>.ipynb on each save.  This can also be set with the
         short `--script` flag.
         """
     )
     
     checkpoint_dir = Unicode(config=True,
         help="""The location in which to keep notebook checkpoints
         
         By default, it is notebook-dir/.ipynb_checkpoints
         """
     )
     def _checkpoint_dir_default(self):
         return os.path.join(self.notebook_dir, '.ipynb_checkpoints')
     
     def _checkpoint_dir_changed(self, name, old, new):
         """do a bit of validation of the checkpoint dir"""
         if not os.path.isabs(new):
             # If we receive a non-absolute path, make it absolute.
             abs_new = os.path.abspath(new)
             self.checkpoint_dir = abs_new
             return
         if os.path.exists(new) and not os.path.isdir(new):
             raise TraitError("checkpoint dir %r is not a directory" % new)
         if not os.path.exists(new):
             self.log.info("Creating checkpoint dir %s", new)
             try:
                 os.mkdir(new)
             except:
                 raise TraitError("Couldn't create checkpoint dir %r" % new)
 
     def get_notebook_names(self, path=''):
         """List all notebook names in the notebook dir and path."""
         path = path.strip('/')
         if not os.path.isdir(self.get_os_path(path=path)):
             raise web.HTTPError(404, 'Directory not found: ' + path)
         names = glob.glob(self.get_os_path('*'+self.filename_ext, path))
         names = [os.path.basename(name)
                  for name in names]
         return names
 
     def increment_filename(self, basename, path='', ext='.ipynb'):
         """Return a non-used filename of the form basename<int>."""
         path = path.strip('/')
         for i in itertools.count():
             name = u'{basename}{i}{ext}'.format(basename=basename, i=i, ext=ext)
             os_path = self.get_os_path(name, path)
             if not os.path.isfile(os_path):
                 break
         return name
 
     def path_exists(self, path):
         """Does the API-style path (directory) actually exist?
         
         Parameters
         ----------
         path : string
             The path to check. This is an API path (`/` separated,
             relative to base notebook-dir).
         
         Returns
         -------
         exists : bool
             Whether the path is indeed a directory.
         """
         path = path.strip('/')
         os_path = self.get_os_path(path=path)
         return os.path.isdir(os_path)
     
     def get_os_path(self, name=None, path=''):
         """Given a notebook name and a URL path, return its file system
         path.
 
         Parameters
         ----------
         name : string
             The name of a notebook file with the .ipynb extension
         path : string
             The relative URL path (with '/' as separator) to the named
             notebook.
 
         Returns
         -------
         path : string
             A file system path that combines notebook_dir (location where
             server started), the relative path, and the filename with the
             current operating system's url.
         """
         parts = path.strip('/').split('/')
         parts = [p for p in parts if p != ''] # remove duplicate splits
         if name is not None:
             parts.append(name)
         path = os.path.join(self.notebook_dir, *parts)
         return path
 
     def notebook_exists(self, name, path=''):
         """Returns a True if the notebook exists. Else, returns False.
 
         Parameters
         ----------
         name : string
             The name of the notebook you are checking.
         path : string
             The relative path to the notebook (with '/' as separator)
 
         Returns
         -------
         bool
         """
         path = path.strip('/')
         nbpath = self.get_os_path(name, path=path)
         return os.path.isfile(nbpath)
 
     def list_notebooks(self, path):
         """Returns a list of dictionaries that are the standard model
         for all notebooks in the relative 'path'.
         
         Parameters
         ----------
         path : str
             the URL path that describes the relative path for the
             listed notebooks
         
         Returns
         -------
         notebooks : list of dicts
             a list of the notebook models without 'content'
         """
         path = path.strip('/')
         notebook_names = self.get_notebook_names(path)
         notebooks = []
         for name in notebook_names:
             model = self.get_notebook_model(name, path, content=False)
             notebooks.append(model)
         notebooks = sorted(notebooks, key=lambda item: item['name'])
         return notebooks
 
     def get_notebook_model(self, name, path='', content=True):
         """ Takes a path and name for a notebook and returns its model
         
         Parameters
         ----------
         name : str
             the name of the notebook
         path : str
             the URL path that describes the relative path for
             the notebook
             
         Returns
         -------
         model : dict
             the notebook model. If contents=True, returns the 'contents' 
             dict in the model as well.
         """
         path = path.strip('/')
         if not self.notebook_exists(name=name, path=path):
             raise web.HTTPError(404, u'Notebook does not exist: %s' % name)
         os_path = self.get_os_path(name, path)
         info = os.stat(os_path)
         last_modified = tz.utcfromtimestamp(info.st_mtime)
         created = tz.utcfromtimestamp(info.st_ctime)
         # Create the notebook model.
         model ={}
         model['name'] = name
         model['path'] = path
         model['last_modified'] = last_modified
         model['created'] = created
         if content:
             with io.open(os_path, 'r', encoding='utf-8') as f:
                 try:
                     nb = current.read(f, u'json')
                 except Exception as e:
                     raise web.HTTPError(400, u"Unreadable Notebook: %s %s" % (os_path, e))
             model['content'] = nb
-            sign.mark_trusted_cells(nb, self.notary.secret, self.notary.scheme)
+            trusted = self.notary.check_signature(nb)
+            if not trusted:
+                self.log.warn("Notebook %s/%s is not trusted", model['path'], model['name'])
+            self.notary.mark_cells(nb, trusted)
         return model
 
     def save_notebook_model(self, model, name='', path=''):
         """Save the notebook model and return the model with no content."""
         path = path.strip('/')
 
         if 'content' not in model:
             raise web.HTTPError(400, u'No notebook JSON data provided')
         
         # One checkpoint should always exist
         if self.notebook_exists(name, path) and not self.list_checkpoints(name, path):
             self.create_checkpoint(name, path)
 
         new_path = model.get('path', path).strip('/')
         new_name = model.get('name', name)
 
         if path != new_path or name != new_name:
             self.rename_notebook(name, path, new_name, new_path)
 
         # Save the notebook file
         os_path = self.get_os_path(new_name, new_path)
         nb = current.to_notebook_json(model['content'])
         
-        if sign.check_trusted_cells(nb):
-            sign.trust_notebook(nb, self.notary.secret, self.notary.scheme)
+        if self.notary.check_cells(nb):
+            self.notary.sign(nb)
+        else:
+            self.log.warn("Saving untrusted notebook %s/%s", new_path, new_name)
+            
         
         if 'name' in nb['metadata']:
             nb['metadata']['name'] = u''
         try:
             self.log.debug("Autosaving notebook %s", os_path)
             with io.open(os_path, 'w', encoding='utf-8') as f:
                 current.write(nb, f, u'json')
         except Exception as e:
             raise web.HTTPError(400, u'Unexpected error while autosaving notebook: %s %s' % (os_path, e))
 
         # Save .py script as well
         if self.save_script:
             py_path = os.path.splitext(os_path)[0] + '.py'
             self.log.debug("Writing script %s", py_path)
             try:
                 with io.open(py_path, 'w', encoding='utf-8') as f:
                     current.write(nb, f, u'py')
             except Exception as e:
                 raise web.HTTPError(400, u'Unexpected error while saving notebook as script: %s %s' % (py_path, e))
 
         model = self.get_notebook_model(new_name, new_path, content=False)
         return model
 
     def update_notebook_model(self, model, name, path=''):
         """Update the notebook's path and/or name"""
         path = path.strip('/')
         new_name = model.get('name', name)
         new_path = model.get('path', path).strip('/')
         if path != new_path or name != new_name:
             self.rename_notebook(name, path, new_name, new_path)
         model = self.get_notebook_model(new_name, new_path, content=False)
         return model
 
     def delete_notebook_model(self, name, path=''):
         """Delete notebook by name and path."""
         path = path.strip('/')
         os_path = self.get_os_path(name, path)
         if not os.path.isfile(os_path):
             raise web.HTTPError(404, u'Notebook does not exist: %s' % os_path)
         
         # clear checkpoints
         for checkpoint in self.list_checkpoints(name, path):
             checkpoint_id = checkpoint['id']
             cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
             if os.path.isfile(cp_path):
                 self.log.debug("Unlinking checkpoint %s", cp_path)
                 os.unlink(cp_path)
         
         self.log.debug("Unlinking notebook %s", os_path)
         os.unlink(os_path)
 
     def rename_notebook(self, old_name, old_path, new_name, new_path):
         """Rename a notebook."""
         old_path = old_path.strip('/')
         new_path = new_path.strip('/')
         if new_name == old_name and new_path == old_path:
             return
         
         new_os_path = self.get_os_path(new_name, new_path)
         old_os_path = self.get_os_path(old_name, old_path)
 
         # Should we proceed with the move?
         if os.path.isfile(new_os_path):
             raise web.HTTPError(409, u'Notebook with name already exists: %s' % new_os_path)
         if self.save_script:
             old_py_path = os.path.splitext(old_os_path)[0] + '.py'
             new_py_path = os.path.splitext(new_os_path)[0] + '.py'
             if os.path.isfile(new_py_path):
                 raise web.HTTPError(409, u'Python script with name already exists: %s' % new_py_path)
 
         # Move the notebook file
         try:
             os.rename(old_os_path, new_os_path)
         except Exception as e:
             raise web.HTTPError(500, u'Unknown error renaming notebook: %s %s' % (old_os_path, e))
 
         # Move the checkpoints
         old_checkpoints = self.list_checkpoints(old_name, old_path)
         for cp in old_checkpoints:
             checkpoint_id = cp['id']
             old_cp_path = self.get_checkpoint_path(checkpoint_id, old_name, old_path)
             new_cp_path = self.get_checkpoint_path(checkpoint_id, new_name, new_path)
             if os.path.isfile(old_cp_path):
                 self.log.debug("Renaming checkpoint %s -> %s", old_cp_path, new_cp_path)
                 os.rename(old_cp_path, new_cp_path)
 
         # Move the .py script
         if self.save_script:
             os.rename(old_py_path, new_py_path)
   
     # Checkpoint-related utilities
     
     def get_checkpoint_path(self, checkpoint_id, name, path=''):
         """find the path to a checkpoint"""
         path = path.strip('/')
         basename, _ = os.path.splitext(name)
         filename = u"{name}-{checkpoint_id}{ext}".format(
             name=basename,
             checkpoint_id=checkpoint_id,
             ext=self.filename_ext,
         )
         cp_path = os.path.join(path, self.checkpoint_dir, filename)
         return cp_path
 
     def get_checkpoint_model(self, checkpoint_id, name, path=''):
         """construct the info dict for a given checkpoint"""
         path = path.strip('/')
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         stats = os.stat(cp_path)
         last_modified = tz.utcfromtimestamp(stats.st_mtime)
         info = dict(
             id = checkpoint_id,
             last_modified = last_modified,
         )
         return info
         
     # public checkpoint API
     
     def create_checkpoint(self, name, path=''):
         """Create a checkpoint from the current state of a notebook"""
         path = path.strip('/')
         nb_path = self.get_os_path(name, path)
         # only the one checkpoint ID:
         checkpoint_id = u"checkpoint"
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         self.log.debug("creating checkpoint for notebook %s", name)
         if not os.path.exists(self.checkpoint_dir):
             os.mkdir(self.checkpoint_dir)
         shutil.copy2(nb_path, cp_path)
         
         # return the checkpoint info
         return self.get_checkpoint_model(checkpoint_id, name, path)
     
     def list_checkpoints(self, name, path=''):
         """list the checkpoints for a given notebook
         
         This notebook manager currently only supports one checkpoint per notebook.
         """
         path = path.strip('/')
         checkpoint_id = "checkpoint"
         path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.exists(path):
             return []
         else:
             return [self.get_checkpoint_model(checkpoint_id, name, path)]
         
     
     def restore_checkpoint(self, checkpoint_id, name, path=''):
         """restore a notebook to a checkpointed state"""
         path = path.strip('/')
         self.log.info("restoring Notebook %s from checkpoint %s", name, checkpoint_id)
         nb_path = self.get_os_path(name, path)
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.isfile(cp_path):
             self.log.debug("checkpoint file does not exist: %s", cp_path)
             raise web.HTTPError(404,
                 u'Notebook checkpoint does not exist: %s-%s' % (name, checkpoint_id)
             )
         # ensure notebook is readable (never restore from an unreadable notebook)
         with io.open(cp_path, 'r', encoding='utf-8') as f:
             nb = current.read(f, u'json')
         shutil.copy2(cp_path, nb_path)
         self.log.debug("copying %s -> %s", cp_path, nb_path)
     
     def delete_checkpoint(self, checkpoint_id, name, path=''):
         """delete a notebook's checkpoint"""
         path = path.strip('/')
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.isfile(cp_path):
             raise web.HTTPError(404,
                 u'Notebook checkpoint does not exist: %s%s-%s' % (path, name, checkpoint_id)
             )
         self.log.debug("unlinking %s", cp_path)
         os.unlink(cp_path)
     
     def info_string(self):
         return "Serving notebooks from local directory: %s" % self.notebook_dir

IPython/nbformat/sign.py

@@ -1,199 +1,203 b''
 """Functions for signing notebooks"""
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2014, The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import base64
 from contextlib import contextmanager
 import hashlib
 from hmac import HMAC
 import io
 import os
 
 from IPython.utils.py3compat import string_types, unicode_type, cast_bytes
 from IPython.config import LoggingConfigurable
-from IPython.utils.traitlets import Instance, Bytes, Enum
+from IPython.utils.traitlets import Instance, Bytes, Enum, Any, Unicode
 
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
 
 def yield_everything(obj):
     """Yield every item in a container as bytes
     
     Allows any JSONable object to be passed to an HMAC digester
     without having to serialize the whole thing.
     """
     if isinstance(obj, dict):
         for key in sorted(obj):
             value = obj[key]
             yield cast_bytes(key)
             for b in yield_everything(value):
                 yield b
     elif isinstance(obj, (list, tuple)):
         for element in obj:
             for b in yield_everything(element):
                 yield b
     elif isinstance(obj, unicode_type):
         yield obj.encode('utf8')
     else:
         yield unicode_type(obj).encode('utf8')
 
 
 @contextmanager
 def signature_removed(nb):
     """Context manager for operating on a notebook with its signature removed
     
     Used for excluding the previous signature when computing a notebook's signature.
     """
     save_signature = nb['metadata'].pop('signature', None)
     try:
         yield
     finally:
         if save_signature is not None:
             nb['metadata']['signature'] = save_signature
 
 
-def notebook_signature(nb, secret, scheme):
-    """Compute a notebook's signature
-    
-    by hashing the entire contents of the notebook via HMAC digest.
-    scheme is the hashing scheme, which must be an attribute of the hashlib module,
-    as listed in hashlib.algorithms.
-    """
-    hmac = HMAC(secret, digestmod=getattr(hashlib, scheme))
-    # don't include the previous hash in the content to hash
-    with signature_removed(nb):
-        # sign the whole thing
-        for b in yield_everything(nb):
-            hmac.update(b)
-        
-    return hmac.hexdigest()
-
-
-def check_notebook_signature(nb, secret, scheme):
-    """Check a notebook's stored signature
-    
-    If a signature is stored in the notebook's metadata,
-    a new signature is computed and compared with the stored value.
-    
-    Returns True if the signature is found and matches, False otherwise.
-    
-    The following conditions must all be met for a notebook to be trusted:
-    - a signature is stored in the form 'scheme:hexdigest'
-    - the stored scheme matches the requested scheme
-    - the requested scheme is available from hashlib
-    - the computed hash from notebook_signature matches the stored hash
-    """
-    stored_signature = nb['metadata'].get('signature', None)
-    if not stored_signature \
-        or not isinstance(stored_signature, string_types) \
-        or ':' not in stored_signature:
-        return False
-    stored_scheme, sig = stored_signature.split(':', 1)
-    if scheme != stored_scheme:
-        return False
-    try:
-        my_signature = notebook_signature(nb, secret, scheme)
-    except AttributeError:
-        return False
-    return my_signature == sig
-
-
-def trust_notebook(nb, secret, scheme):
-    """Re-sign a notebook, indicating that its output is trusted
-    
-    stores 'scheme:hmac-hexdigest' in notebook.metadata.signature
-    
-    e.g. 'sha256:deadbeef123...'
-    """
-    signature = notebook_signature(nb, secret, scheme)
-    nb['metadata']['signature'] = "%s:%s" % (scheme, signature)
-
-
-def mark_trusted_cells(nb, secret, scheme):
-    """Mark cells as trusted if the notebook's signature can be verified
-    
-    Sets ``cell.trusted = True | False`` on all code cells,
-    depending on whether the stored signature can be verified.
-    """
-    if not nb['worksheets']:
-        # nothing to mark if there are no cells
-        return True
-    trusted = check_notebook_signature(nb, secret, scheme)
-    for cell in nb['worksheets'][0]['cells']:
-        if cell['cell_type'] == 'code':
-            cell['trusted'] = trusted
-    return trusted
-
-
-def check_trusted_cells(nb):
-    """Return whether all code cells are trusted
-    
-    If there are no code cells, return True.
-    """
-    if not nb['worksheets']:
-        return True
-    for cell in nb['worksheets'][0]['cells']:
-        if cell['cell_type'] != 'code':
-            continue
-        if not cell.get('trusted', False):
-            return False
-    return True
-
-
 class NotebookNotary(LoggingConfigurable):
-    """A class for configuring notebook signatures
-    
-    It stores the secret with which to sign notebooks,
-    and the hashing scheme to use for notebook signatures.
-    """
-    
-    scheme = Enum(hashlib.algorithms, default_value='sha256', config=True,
-        help="""The hashing algorithm used to sign notebooks."""
-    )
+    """A class for computing and verifying notebook signatures."""
     
     profile_dir = Instance("IPython.core.profiledir.ProfileDir")
     def _profile_dir_default(self):
         from IPython.core.application import BaseIPythonApplication
         if BaseIPythonApplication.initialized():
             app = BaseIPythonApplication.instance()
         else:
             # create an app, without the global instance
             app = BaseIPythonApplication()
             app.initialize()
         return app.profile_dir
     
+    algorithm = Enum(hashlib.algorithms, default_value='sha256', config=True,
+        help="""The hashing algorithm used to sign notebooks."""
+    )
+    def _algorithm_changed(self, name, old, new):
+        self.digestmod = getattr(hashlib, self.algorithm)
+    
+    digestmod = Any()
+    def _digestmod_default(self):
+        return getattr(hashlib, self.algorithm)
+    
+    secret_file = Unicode()
+    def _secret_file_default(self):
+        if self.profile_dir is None:
+            return ''
+        return os.path.join(self.profile_dir.security_dir, 'notebook_secret')
+    
     secret = Bytes(config=True,
         help="""The secret key with which notebooks are signed."""
     )
     def _secret_default(self):
         # note : this assumes an Application is running
-        profile_dir = self.profile_dir
-        secret_file = os.path.join(profile_dir.security_dir, 'notebook_secret')
-        if os.path.exists(secret_file):
-            with io.open(secret_file, 'rb') as f:
+        if os.path.exists(self.secret_file):
+            with io.open(self.secret_file, 'rb') as f:
                 return f.read()
         else:
             secret = base64.encodestring(os.urandom(1024))
-            self.log.info("Writing output secret to %s", secret_file)
-            with io.open(secret_file, 'wb') as f:
-                f.write(secret)
-            try:
-                os.chmod(secret_file, 0o600)
-            except OSError:
-                self.log.warn(
-                    "Could not set permissions on %s",
-                    secret_file
-                )
+            self._write_secret_file(secret)
             return secret
+    
+    def _write_secret_file(self, secret):
+        """write my secret to my secret_file"""
+        self.log.info("Writing output secret to %s", self.secret_file)
+        with io.open(self.secret_file, 'wb') as f:
+            f.write(secret)
+        try:
+            os.chmod(self.secret_file, 0o600)
+        except OSError:
+            self.log.warn(
+                "Could not set permissions on %s",
+                self.secret_file
+            )
+        return secret
+    
+    def compute_signature(self, nb):
+        """Compute a notebook's signature
+        
+        by hashing the entire contents of the notebook via HMAC digest.
+        """
+        hmac = HMAC(self.secret, digestmod=self.digestmod)
+        # don't include the previous hash in the content to hash
+        with signature_removed(nb):
+            # sign the whole thing
+            for b in yield_everything(nb):
+                hmac.update(b)
+        
+        return hmac.hexdigest()
+    
+    def check_signature(self, nb):
+        """Check a notebook's stored signature
+        
+        If a signature is stored in the notebook's metadata,
+        a new signature is computed and compared with the stored value.
+        
+        Returns True if the signature is found and matches, False otherwise.
+        
+        The following conditions must all be met for a notebook to be trusted:
+        - a signature is stored in the form 'scheme:hexdigest'
+        - the stored scheme matches the requested scheme
+        - the requested scheme is available from hashlib
+        - the computed hash from notebook_signature matches the stored hash
+        """
+        stored_signature = nb['metadata'].get('signature', None)
+        if not stored_signature \
+            or not isinstance(stored_signature, string_types) \
+            or ':' not in stored_signature:
+            return False
+        stored_algo, sig = stored_signature.split(':', 1)
+        if self.algorithm != stored_algo:
+            return False
+        my_signature = self.compute_signature(nb)
+        return my_signature == sig
+    
+    def sign(self, nb):
+        """Sign a notebook, indicating that its output is trusted
+        
+        stores 'algo:hmac-hexdigest' in notebook.metadata.signature
+        
+        e.g. 'sha256:deadbeef123...'
+        """
+        signature = self.compute_signature(nb)
+        nb['metadata']['signature'] = "%s:%s" % (self.algorithm, signature)
+    
+    def mark_cells(self, nb, trusted):
+        """Mark cells as trusted if the notebook's signature can be verified
+        
+        Sets ``cell.trusted = True | False`` on all code cells,
+        depending on whether the stored signature can be verified.
+        
+        This function is the inverse of check_cells
+        """
+        if not nb['worksheets']:
+            # nothing to mark if there are no cells
+            return
+        for cell in nb['worksheets'][0]['cells']:
+            if cell['cell_type'] == 'code':
+                cell['trusted'] = trusted
+    
+    def check_cells(self, nb):
+        """Return whether all code cells are trusted
+        
+        If there are no code cells, return True.
+        
+        This function is the inverse of mark_cells.
+        """
+        if not nb['worksheets']:
+            return True
+        for cell in nb['worksheets'][0]['cells']:
+            if cell['cell_type'] != 'code':
+                continue
+            if not cell.get('trusted', False):
+                return False
+        return True
+    
 
     
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