我一直在寻找一种在 Google App Engine 中进行基于 cookie 的身份验证/会话的方法，因为我不喜欢基于 memcache 的会话的想法，而且我也不喜欢强迫用户创建 google 帐户只是为了使用网站。我偶然发现有人发帖提到了 Tornado 框架中的一些签名 cookie 函数，它看起来像我需要的。我想到的是将用户的 id 存储在防篡改 cookie 中，并且可能使用请求处理程序的装饰器来测试用户的身份验证状态，并且作为附带好处，用户 id 将可用于请求处理程序数据存储工作等。这个概念类似于 ASP.NET 中的表单身份验证。这段代码来自 Tornado 框架的 web.py 模块。
根据文档字符串，它“对 cookie 进行签名和时间戳记，因此它不能被伪造”和“如果验证，则返回给定的签名 cookie，或者无。”
我尝试在 App Engine 项目中使用它，但我不理解尝试让这些方法在请求处理程序的上下文中工作的细微差别。有人可以告诉我正确的方法来做到这一点，而不会失去 FriendFeed 开发人员投入其中的功能吗？set_secure_cookie 和 get_secure_cookie 部分是最重要的，但如果能够使用其他方法也很好。
#!/usr/bin/env python
import Cookie
import base64
import time
import hashlib
import hmac
import datetime
import re
import calendar
import email.utils
import logging
def _utf8(s):
if isinstance(s, unicode):
return s.encode("utf-8")
assert isinstance(s, str)
return s
def _unicode(s):
if isinstance(s, str):
try:
return s.decode("utf-8")
except UnicodeDecodeError:
raise HTTPError(400, "Non-utf8 argument")
assert isinstance(s, unicode)
return s
def _time_independent_equals(a, b):
if len(a) != len(b):
return False
result = 0
for x, y in zip(a, b):
result |= ord(x) ^ ord(y)
return result == 0
def cookies(self):
"""A dictionary of Cookie.Morsel objects."""
if not hasattr(self,"_cookies"):
self._cookies = Cookie.BaseCookie()
if "Cookie" in self.request.headers:
try:
self._cookies.load(self.request.headers["Cookie"])
except:
self.clear_all_cookies()
return self._cookies
def _cookie_signature(self,*parts):
self.require_setting("cookie_secret","secure cookies")
hash = hmac.new(self.application.settings["cookie_secret"],
digestmod=hashlib.sha1)
for part in parts:hash.update(part)
return hash.hexdigest()
def get_cookie(self,name,default=None):
"""Gets the value of the cookie with the given name,else default."""
if name in self.cookies:
return self.cookies[name].value
return default
def set_cookie(self,name,value,domain=None,expires=None,path="/",
expires_days=None):
"""Sets the given cookie name/value with the given options."""
name = _utf8(name)
value = _utf8(value)
if re.search(r"[\x00-\x20]",name + value):
# Don't let us accidentally inject bad stuff
raise ValueError("Invalid cookie %r:%r" % (name,value))
if not hasattr(self,"_new_cookies"):
self._new_cookies = []
new_cookie = Cookie.BaseCookie()
self._new_cookies.append(new_cookie)
new_cookie[name] = value
if domain:
new_cookie[name]["domain"] = domain
if expires_days is not None and not expires:
expires = datetime.datetime.utcnow() + datetime.timedelta(
days=expires_days)
if expires:
timestamp = calendar.timegm(expires.utctimetuple())
new_cookie[name]["expires"] = email.utils.formatdate(
timestamp,localtime=False,usegmt=True)
if path:
new_cookie[name]["path"] = path
def clear_cookie(self,name,path="/",domain=None):
"""Deletes the cookie with the given name."""
expires = datetime.datetime.utcnow() - datetime.timedelta(days=365)
self.set_cookie(name,value="",path=path,expires=expires,
domain=domain)
def clear_all_cookies(self):
"""Deletes all the cookies the user sent with this request."""
for name in self.cookies.iterkeys():
self.clear_cookie(name)
def set_secure_cookie(self,name,value,expires_days=30,**kwargs):
"""Signs and timestamps a cookie so it cannot be forged"""
timestamp = str(int(time.time()))
value = base64.b64encode(value)
signature = self._cookie_signature(name,value,timestamp)
value = "|".join([value,timestamp,signature])
self.set_cookie(name,value,expires_days=expires_days,**kwargs)
def get_secure_cookie(self,name,include_name=True,value=None):
"""Returns the given signed cookie if it validates,or None"""
if value is None:value = self.get_cookie(name)
if not value:return None
parts = value.split("|")
if len(parts) != 3:return None
if include_name:
signature = self._cookie_signature(name,parts[0],parts[1])
else:
signature = self._cookie_signature(parts[0],parts[1])
if not _time_independent_equals(parts[2],signature):
logging.warning("Invalid cookie signature %r",value)
return None
timestamp = int(parts[1])
if timestamp < time.time() - 31 * 86400:
logging.warning("Expired cookie %r",value)
return None
try:
return base64.b64decode(parts[0])
except:
return None
uid=1234|1234567890|d32b9e9c67274fa062e2599fd659cc14
部分：
1. uid 是密钥的名称
2. 1234 是您的明文值
3. 1234567890 是时间戳
4. d32b9e9c67274fa062e2599fd659cc14 是由值和时间戳组成的签名