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# -*- coding: utf-8 -*-
WSGI application traceback debugger.
:copyright: 2007 Pallets
:license: BSD-3-Clause
import getpass
import hashlib
import json
import mimetypes
import os
import pkgutil
import re
import sys
import time
import uuid
from itertools import chain
from os.path import basename
from os.path import join
from .._compat import text_type
from .._internal import _log
from ..http import parse_cookie
from import gen_salt
from ..wrappers import BaseRequest as Request
from ..wrappers import BaseResponse as Response
from .console import Console
from .tbtools import get_current_traceback
from .tbtools import render_console_html
# A week
PIN_TIME = 60 * 60 * 24 * 7
def hash_pin(pin):
if isinstance(pin, text_type):
pin = pin.encode("utf-8", "replace")
return hashlib.md5(pin + b"shittysalt").hexdigest()[:12]
_machine_id = None
def get_machine_id():
global _machine_id
if _machine_id is not None:
return _machine_id
def _generate():
linux = b""
# machine-id is stable across boots, boot_id is not.
for filename in "/etc/machine-id", "/proc/sys/kernel/random/boot_id":
with open(filename, "rb") as f:
value = f.readline().strip()
except IOError:
if value:
linux += value
# Containers share the same machine id, add some cgroup
# information. This is used outside containers too but should be
# relatively stable across boots.
with open("/proc/self/cgroup", "rb") as f:
linux += f.readline().strip().rpartition(b"/")[2]
except IOError:
if linux:
return linux
# On OS X, use ioreg to get the computer's serial number.
# subprocess may not be available, e.g. Google App Engine
from subprocess import Popen, PIPE
dump = Popen(
["ioreg", "-c", "IOPlatformExpertDevice", "-d", "2"], stdout=PIPE
match ='"serial-number" = <([^>]+)', dump)
if match is not None:
except (OSError, ImportError):
# On Windows, use winreg to get the machine guid.
import winreg as wr
except ImportError:
import _winreg as wr
except ImportError:
wr = None
if wr is not None:
with wr.OpenKey(
wr.KEY_READ | wr.KEY_WOW64_64KEY,
) as rk:
guid, guid_type = wr.QueryValueEx(rk, "MachineGuid")
if guid_type == wr.REG_SZ:
return guid.encode("utf-8")
return guid
except WindowsError:
_machine_id = _generate()
return _machine_id
class _ConsoleFrame(object):
"""Helper class so that we can reuse the frame console code for the
standalone console.
def __init__(self, namespace):
self.console = Console(namespace) = 0
def get_pin_and_cookie_name(app):
"""Given an application object this returns a semi-stable 9 digit pin
code and a random key. The hope is that this is stable between
restarts to not make debugging particularly frustrating. If the pin
was forcefully disabled this returns `None`.
Second item in the resulting tuple is the cookie name for remembering.
pin = os.environ.get("WERKZEUG_DEBUG_PIN")
rv = None
num = None
# Pin was explicitly disabled
if pin == "off":
return None, None
# Pin was provided explicitly
if pin is not None and pin.replace("-", "").isdigit():
# If there are separators in the pin, return it directly
if "-" in pin:
rv = pin
num = pin
modname = getattr(app, "__module__", app.__class__.__module__)
# getuser imports the pwd module, which does not exist in Google
# App Engine. It may also raise a KeyError if the UID does not
# have a username, such as in Docker.
username = getpass.getuser()
except (ImportError, KeyError):
username = None
mod = sys.modules.get(modname)
# This information only exists to make the cookie unique on the
# computer, not as a security feature.
probably_public_bits = [
getattr(app, "__name__", app.__class__.__name__),
getattr(mod, "__file__", None),
# This information is here to make it harder for an attacker to
# guess the cookie name. They are unlikely to be contained anywhere
# within the unauthenticated debug page.
private_bits = [str(uuid.getnode()), get_machine_id()]
h = hashlib.md5()
for bit in chain(probably_public_bits, private_bits):
if not bit:
if isinstance(bit, text_type):
bit = bit.encode("utf-8")
cookie_name = "__wzd" + h.hexdigest()[:20]
# If we need to generate a pin we salt it a bit more so that we don't
# end up with the same value and generate out 9 digits
if num is None:
num = ("%09d" % int(h.hexdigest(), 16))[:9]
# Format the pincode in groups of digits for easier remembering if
# we don't have a result yet.
if rv is None:
for group_size in 5, 4, 3:
if len(num) % group_size == 0:
rv = "-".join(
num[x : x + group_size].rjust(group_size, "0")
for x in range(0, len(num), group_size)
rv = num
return rv, cookie_name
class DebuggedApplication(object):
"""Enables debugging support for a given application::
from werkzeug.debug import DebuggedApplication
from myapp import app
app = DebuggedApplication(app, evalex=True)
The `evalex` keyword argument allows evaluating expressions in a
traceback's frame context.
:param app: the WSGI application to run debugged.
:param evalex: enable exception evaluation feature (interactive
debugging). This requires a non-forking server.
:param request_key: The key that points to the request object in ths
environment. This parameter is ignored in current
:param console_path: the URL for a general purpose console.
:param console_init_func: the function that is executed before starting
the general purpose console. The return value
is used as initial namespace.
:param show_hidden_frames: by default hidden traceback frames are skipped.
You can show them by setting this parameter
to `True`.
:param pin_security: can be used to disable the pin based security system.
:param pin_logging: enables the logging of the pin system.
def __init__(
if not console_init_func:
console_init_func = None = app
self.evalex = evalex
self.frames = {}
self.tracebacks = {}
self.request_key = request_key
self.console_path = console_path
self.console_init_func = console_init_func
self.show_hidden_frames = show_hidden_frames
self.secret = gen_salt(20)
self._failed_pin_auth = 0
self.pin_logging = pin_logging
if pin_security:
# Print out the pin for the debugger on standard out.
if os.environ.get("WERKZEUG_RUN_MAIN") == "true" and pin_logging:
_log("warning", " * Debugger is active!")
if is None:
_log("warning", " * Debugger PIN disabled. DEBUGGER UNSECURED!")
_log("info", " * Debugger PIN: %s" %
else: = None
def pin(self):
if not hasattr(self, "_pin"):
self._pin, self._pin_cookie = get_pin_and_cookie_name(
return self._pin
def pin(self, value):
self._pin = value
def pin_cookie_name(self):
"""The name of the pin cookie."""
if not hasattr(self, "_pin_cookie"):
self._pin, self._pin_cookie = get_pin_and_cookie_name(
return self._pin_cookie
def debug_application(self, environ, start_response):
"""Run the application and conserve the traceback frames."""
app_iter = None
app_iter =, start_response)
for item in app_iter:
yield item
if hasattr(app_iter, "close"):
except Exception:
if hasattr(app_iter, "close"):
traceback = get_current_traceback(
for frame in traceback.frames:
self.frames[] = frame
self.tracebacks[] = traceback
("Content-Type", "text/html; charset=utf-8"),
# Disable Chrome's XSS protection, the debug
# output can cause false-positives.
("X-XSS-Protection", "0"),
except Exception:
# if we end up here there has been output but an error
# occurred. in that situation we can do nothing fancy any
# more, better log something into the error log and fall
# back gracefully.
"Debugging middleware caught exception in streamed "
"response at a point where response headers were already "
is_trusted = bool(self.check_pin_trust(environ))
yield traceback.render_full(
evalex=self.evalex, evalex_trusted=is_trusted, secret=self.secret
).encode("utf-8", "replace")
def execute_command(self, request, command, frame):
"""Execute a command in a console."""
return Response(frame.console.eval(command), mimetype="text/html")
def display_console(self, request):
"""Display a standalone shell."""
if 0 not in self.frames:
if self.console_init_func is None:
ns = {}
ns = dict(self.console_init_func())
self.frames[0] = _ConsoleFrame(ns)
is_trusted = bool(self.check_pin_trust(request.environ))
return Response(
render_console_html(secret=self.secret, evalex_trusted=is_trusted),
def paste_traceback(self, request, traceback):
"""Paste the traceback and return a JSON response."""
rv = traceback.paste()
return Response(json.dumps(rv), mimetype="application/json")
def get_resource(self, request, filename):
"""Return a static resource from the shared folder."""
filename = join("shared", basename(filename))
data = pkgutil.get_data(__package__, filename)
except OSError:
data = None
if data is not None:
mimetype = mimetypes.guess_type(filename)[0] or "application/octet-stream"
return Response(data, mimetype=mimetype)
return Response("Not Found", status=404)
def check_pin_trust(self, environ):
"""Checks if the request passed the pin test. This returns `True` if the
request is trusted on a pin/cookie basis and returns `False` if not.
Additionally if the cookie's stored pin hash is wrong it will return
`None` so that appropriate action can be taken.
if is None:
return True
val = parse_cookie(environ).get(self.pin_cookie_name)
if not val or "|" not in val:
return False
ts, pin_hash = val.split("|", 1)
if not ts.isdigit():
return False
if pin_hash != hash_pin(
return None
return (time.time() - PIN_TIME) < int(ts)
def _fail_pin_auth(self):
time.sleep(5.0 if self._failed_pin_auth > 5 else 0.5)
self._failed_pin_auth += 1
def pin_auth(self, request):
"""Authenticates with the pin."""
exhausted = False
auth = False
trust = self.check_pin_trust(request.environ)
# If the trust return value is `None` it means that the cookie is
# set but the stored pin hash value is bad. This means that the
# pin was changed. In this case we count a bad auth and unset the
# cookie. This way it becomes harder to guess the cookie name
# instead of the pin as we still count up failures.
bad_cookie = False
if trust is None:
bad_cookie = True
# If we're trusted, we're authenticated.
elif trust:
auth = True
# If we failed too many times, then we're locked out.
elif self._failed_pin_auth > 10:
exhausted = True
# Otherwise go through pin based authentication
entered_pin = request.args.get("pin")
if entered_pin.strip().replace("-", "") =="-", ""):
self._failed_pin_auth = 0
auth = True
rv = Response(
json.dumps({"auth": auth, "exhausted": exhausted}),
if auth:
"%s|%s" % (int(time.time()), hash_pin(,
elif bad_cookie:
return rv
def log_pin_request(self):
"""Log the pin if needed."""
if self.pin_logging and is not None:
"info", " * To enable the debugger you need to enter the security pin:"
_log("info", " * Debugger pin code: %s" %
return Response("")
def __call__(self, environ, start_response):
"""Dispatch the requests."""
# important: don't ever access a function here that reads the incoming
# form data! Otherwise the application won't have access to that data
# any more!
request = Request(environ)
response = self.debug_application
if request.args.get("__debugger__") == "yes":
cmd = request.args.get("cmd")
arg = request.args.get("f")
secret = request.args.get("s")
traceback = self.tracebacks.get(request.args.get("tb", type=int))
frame = self.frames.get(request.args.get("frm", type=int))
if cmd == "resource" and arg:
response = self.get_resource(request, arg)
elif cmd == "paste" and traceback is not None and secret == self.secret:
response = self.paste_traceback(request, traceback)
elif cmd == "pinauth" and secret == self.secret:
response = self.pin_auth(request)
elif cmd == "printpin" and secret == self.secret:
response = self.log_pin_request()
elif (
and cmd is not None
and frame is not None
and self.secret == secret
and self.check_pin_trust(environ)
response = self.execute_command(request, cmd, frame)
elif (
and self.console_path is not None
and request.path == self.console_path
response = self.display_console(request)
return response(environ, start_response)
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