wrw/auth.py

   1 import binascii, hashlib, threading, time
   2 import resp
   3
   4 class unauthorized(resp.httperror):
   5     def __init__(self, challenge, message=None, detail=None):
   6         super(unauthorized, self).__init__(401, message, detail)
   7         if isinstance(challenge, str):
   8             challenge = [challenge]
   9         self.challenge = challenge
  10
  11     def handle(self, req):
  12         for challenge in self.challenge:
  13             req.ohead.add("WWW-Authenticate", challenge)
  14         return super(unauthorized, self).handle(req)
  15
  16 class forbidden(resp.httperror):
  17     def __init__(self, message=None, detail=None):
  18         super(forbidden, self).__init__(403, message, detail)
  19
  20 def parsemech(req):
  21     h = req.ihead.get("Authorization", None)
  22     if h is None:
  23         return None, None
  24     p = h.find(" ")
  25     if p < 0:
  26         return None, None
  27     return h[:p].strip().lower(), h[p + 1:].strip()
  28
  29 def parsebasic(req):
  30     mech, data = parsemech(req)
  31     if mech != "basic":
  32         return None, None
  33     try:
  34         raw = binascii.a2b_base64(data)
  35     except binascii.Error:
  36         return None, None
  37     p = raw.find(":")
  38     if p < 0:
  39         return None, None
  40     return raw[:p], raw[p + 1:]
  41
  42 class basiccache(object):
  43     cachetime = 300
  44
  45     def __init__(self, realm, authfn=None):
  46         self._lock = threading.Lock()
  47         self._cache = {}
  48         self.realm = realm
  49         if authfn is not None:
  50             self.auth = authfn
  51
  52     def _obscure(self, nm, pw):
  53         dig = hashlib.sha256()
  54         dig.update(self.realm)
  55         dig.update(nm)
  56         dig.update(pw)
  57         return dig.digest()
  58
  59     def check(self, req):
  60         nm, pw = parsebasic(req)
  61         if nm is None:
  62             raise unauthorized("Basic Realm=\"%s\"" % self.realm)
  63         pwh = self._obscure(nm, pw)
  64         now = time.time()
  65         with self._lock:
  66             if (nm, pwh) in self._cache:
  67                 lock, atime, res, resob = self._cache[nm, pwh]
  68                 if now - atime < self.cachetime:
  69                     if res == "s":
  70                         return resob
  71                     elif res == "f":
  72                         raise resob
  73             else:
  74                 lock = threading.Lock()
  75                 self._cache[nm, pwh] = (lock, now, None, None)
  76         with lock:
  77             try:
  78                 ret = self.auth(req, nm, pw)
  79             except forbidden, exc:
  80                 with self._lock:
  81                     self._cache[nm, pwh] = (lock, now, "f", exc)
  82                 raise
  83             if ret is None:
  84                 raise forbidden()
  85             with self._lock:
  86                 self._cache[nm, pwh] = (lock, now, "s", ret)
  87             return ret
  88
  89     def auth(self, req, nm, pw):
  90         raise Exception("authentication function neither supplied nor overridden")