Source Code for Module ganeti.serializer

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2007, 2008 Google Inc. 
  5  # 
  6  # This program is free software; you can redistribute it and/or modify 
  7  # it under the terms of the GNU General Public License as published by 
  8  # the Free Software Foundation; either version 2 of the License, or 
  9  # (at your option) any later version. 
 10  # 
 11  # This program is distributed in the hope that it will be useful, but 
 12  # WITHOUT ANY WARRANTY; without even the implied warranty of 
 13  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
 14  # General Public License for more details. 
 15  # 
 16  # You should have received a copy of the GNU General Public License 
 17  # along with this program; if not, write to the Free Software 
 18  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 
 19  # 02110-1301, USA. 
 20   
 21  """Serializer abstraction module 
 22   
 23  This module introduces a simple abstraction over the serialization 
 24  backend (currently json). 
 25   
 26  """ 
 27  # pylint: disable=C0103 
 28   
 29  # C0103: Invalid name, since pylint doesn't see that Dump points to a 
 30  # function and not a constant 
 31   
 32  import simplejson 
 33  import re 
 34   
 35  from ganeti import errors 
 36  from ganeti import utils 
 37   
 38   
 39  _JSON_INDENT = 2 
 40   
 41  _RE_EOLSP = re.compile("[ \t]+$", re.MULTILINE) 
 42   
 43   
 44 -def _GetJsonDumpers(_encoder_class=simplejson.JSONEncoder): 
 45    """Returns two JSON functions to serialize data. 
 46   
 47    @rtype: (callable, callable) 
 48    @return: The function to generate a compact form of JSON and another one to 
 49             generate a more readable, indented form of JSON (if supported) 
 50   
 51    """ 
 52    plain_encoder = _encoder_class(sort_keys=True) 
 53   
 54    # Check whether the simplejson module supports indentation 
 55    try: 
 56      indent_encoder = _encoder_class(indent=_JSON_INDENT, sort_keys=True) 
 57    except TypeError: 
 58      # Indentation not supported 
 59      indent_encoder = plain_encoder 
 60   
 61    return (plain_encoder.encode, indent_encoder.encode) 
 62   
 63   
 64  (_DumpJson, _DumpJsonIndent) = _GetJsonDumpers() 
 65   
 66   
 67 -def DumpJson(data, indent=True): 
 68    """Serialize a given object. 
 69   
 70    @param data: the data to serialize 
 71    @param indent: whether to indent output (depends on simplejson version) 
 72   
 73    @return: the string representation of data 
 74   
 75    """ 
 76    if indent: 
 77      fn = _DumpJsonIndent 
 78    else: 
 79      fn = _DumpJson 
 80   
 81    txt = _RE_EOLSP.sub("", fn(data)) 
 82    if not txt.endswith("\n"): 
 83      txt += "\n" 
 84   
 85    return txt 
 86   
 87   
 88 -def LoadJson(txt): 
 89    """Unserialize data from a string. 
 90   
 91    @param txt: the json-encoded form 
 92   
 93    @return: the original data 
 94   
 95    """ 
 96    return simplejson.loads(txt) 
 97   
 98   
 99 -def DumpSignedJson(data, key, salt=None, key_selector=None): 
100    """Serialize a given object and authenticate it. 
101   
102    @param data: the data to serialize 
103    @param key: shared hmac key 
104    @param key_selector: name/id that identifies the key (in case there are 
105      multiple keys in use, e.g. in a multi-cluster environment) 
106    @return: the string representation of data signed by the hmac key 
107   
108    """ 
109    txt = DumpJson(data, indent=False) 
110    if salt is None: 
111      salt = "" 
112    signed_dict = { 
113      "msg": txt, 
114      "salt": salt, 
115      } 
116   
117    if key_selector: 
118      signed_dict["key_selector"] = key_selector 
119    else: 
120      key_selector = "" 
121   
122    signed_dict["hmac"] = utils.Sha1Hmac(key, txt, salt=salt + key_selector) 
123   
124    return DumpJson(signed_dict, indent=False) 
125   
126   
127 -def LoadSignedJson(txt, key): 
128    """Verify that a given message was signed with the given key, and load it. 
129   
130    @param txt: json-encoded hmac-signed message 
131    @param key: the shared hmac key or a callable taking one argument (the key 
132      selector), which returns the hmac key belonging to the key selector. 
133      Typical usage is to pass a reference to the get method of a dict. 
134    @rtype: tuple of original data, string 
135    @return: original data, salt 
136    @raises errors.SignatureError: if the message signature doesn't verify 
137   
138    """ 
139    signed_dict = LoadJson(txt) 
140    if not isinstance(signed_dict, dict): 
141      raise errors.SignatureError("Invalid external message") 
142    try: 
143      msg = signed_dict["msg"] 
144      salt = signed_dict["salt"] 
145      hmac_sign = signed_dict["hmac"] 
146    except KeyError: 
147      raise errors.SignatureError("Invalid external message") 
148   
149    if callable(key): 
150      # pylint: disable=E1103 
151      key_selector = signed_dict.get("key_selector", None) 
152      hmac_key = key(key_selector) 
153      if not hmac_key: 
154        raise errors.SignatureError("No key with key selector '%s' found" % 
155                                    key_selector) 
156    else: 
157      key_selector = "" 
158      hmac_key = key 
159   
160    if not utils.VerifySha1Hmac(hmac_key, msg, hmac_sign, 
161                                salt=salt + key_selector): 
162      raise errors.SignatureError("Invalid Signature") 
163   
164    return LoadJson(msg), salt 
165   
166   
167  Dump = DumpJson 
168  Load = LoadJson 
169  DumpSigned = DumpSignedJson 
170  LoadSigned = LoadSignedJson 
171