Coverage for /var/srv/projects/api.amasfac.comuna18.com/tmp/venv/lib/python3.9/site-packages/django/core/signing.py: 37%
114 statements
« prev ^ index » next coverage.py v6.4.4, created at 2023-07-17 14:22 -0600
1"""
2Functions for creating and restoring url-safe signed JSON objects.
4The format used looks like this:
6>>> signing.dumps("hello")
7'ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk'
9There are two components here, separated by a ':'. The first component is a
10URLsafe base64 encoded JSON of the object passed to dumps(). The second
11component is a base64 encoded hmac/SHA1 hash of "$first_component:$secret"
13signing.loads(s) checks the signature and returns the deserialized object.
14If the signature fails, a BadSignature exception is raised.
16>>> signing.loads("ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk")
17'hello'
18>>> signing.loads("ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk-modified")
19...
20BadSignature: Signature failed: ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk-modified
22You can optionally compress the JSON prior to base64 encoding it to save
23space, using the compress=True argument. This checks if compression actually
24helps and only applies compression if the result is a shorter string:
26>>> signing.dumps(list(range(1, 20)), compress=True)
27'.eJwFwcERACAIwLCF-rCiILN47r-GyZVJsNgkxaFxoDgxcOHGxMKD_T7vhAml:1QaUaL:BA0thEZrp4FQVXIXuOvYJtLJSrQ'
29The fact that the string is compressed is signalled by the prefixed '.' at the
30start of the base64 JSON.
32There are 65 url-safe characters: the 64 used by url-safe base64 and the ':'.
33These functions make use of all of them.
34"""
36import base64
37import datetime
38import json
39import time
40import zlib
42from django.conf import settings
43from django.utils.crypto import constant_time_compare, salted_hmac
44from django.utils.encoding import force_bytes
45from django.utils.module_loading import import_string
46from django.utils.regex_helper import _lazy_re_compile
48_SEP_UNSAFE = _lazy_re_compile(r"^[A-z0-9-_=]*$")
49BASE62_ALPHABET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
52class BadSignature(Exception):
53 """Signature does not match."""
55 pass
58class SignatureExpired(BadSignature):
59 """Signature timestamp is older than required max_age."""
61 pass
64def b62_encode(s):
65 if s == 0:
66 return "0"
67 sign = "-" if s < 0 else ""
68 s = abs(s)
69 encoded = ""
70 while s > 0:
71 s, remainder = divmod(s, 62)
72 encoded = BASE62_ALPHABET[remainder] + encoded
73 return sign + encoded
76def b62_decode(s):
77 if s == "0":
78 return 0
79 sign = 1
80 if s[0] == "-":
81 s = s[1:]
82 sign = -1
83 decoded = 0
84 for digit in s:
85 decoded = decoded * 62 + BASE62_ALPHABET.index(digit)
86 return sign * decoded
89def b64_encode(s):
90 return base64.urlsafe_b64encode(s).strip(b"=")
93def b64_decode(s):
94 pad = b"=" * (-len(s) % 4)
95 return base64.urlsafe_b64decode(s + pad)
98def base64_hmac(salt, value, key, algorithm="sha1"):
99 return b64_encode(
100 salted_hmac(salt, value, key, algorithm=algorithm).digest()
101 ).decode()
104def get_cookie_signer(salt="django.core.signing.get_cookie_signer"):
105 Signer = import_string(settings.SIGNING_BACKEND)
106 key = force_bytes(settings.SECRET_KEY) # SECRET_KEY may be str or bytes.
107 return Signer(b"django.http.cookies" + key, salt=salt)
110class JSONSerializer:
111 """
112 Simple wrapper around json to be used in signing.dumps and
113 signing.loads.
114 """
116 def dumps(self, obj):
117 return json.dumps(obj, separators=(",", ":")).encode("latin-1")
119 def loads(self, data):
120 return json.loads(data.decode("latin-1"))
123def dumps(
124 obj, key=None, salt="django.core.signing", serializer=JSONSerializer, compress=False
125):
126 """
127 Return URL-safe, hmac signed base64 compressed JSON string. If key is
128 None, use settings.SECRET_KEY instead. The hmac algorithm is the default
129 Signer algorithm.
131 If compress is True (not the default), check if compressing using zlib can
132 save some space. Prepend a '.' to signify compression. This is included
133 in the signature, to protect against zip bombs.
135 Salt can be used to namespace the hash, so that a signed string is
136 only valid for a given namespace. Leaving this at the default
137 value or re-using a salt value across different parts of your
138 application without good cause is a security risk.
140 The serializer is expected to return a bytestring.
141 """
142 return TimestampSigner(key, salt=salt).sign_object(
143 obj, serializer=serializer, compress=compress
144 )
147def loads(
148 s, key=None, salt="django.core.signing", serializer=JSONSerializer, max_age=None
149):
150 """
151 Reverse of dumps(), raise BadSignature if signature fails.
153 The serializer is expected to accept a bytestring.
154 """
155 return TimestampSigner(key, salt=salt).unsign_object(
156 s, serializer=serializer, max_age=max_age
157 )
160class Signer:
161 def __init__(self, key=None, sep=":", salt=None, algorithm=None):
162 self.key = key or settings.SECRET_KEY
163 self.sep = sep
164 if _SEP_UNSAFE.match(self.sep): 164 ↛ 165line 164 didn't jump to line 165, because the condition on line 164 was never true
165 raise ValueError(
166 "Unsafe Signer separator: %r (cannot be empty or consist of "
167 "only A-z0-9-_=)" % sep,
168 )
169 self.salt = salt or "%s.%s" % (
170 self.__class__.__module__,
171 self.__class__.__name__,
172 )
173 self.algorithm = algorithm or "sha256"
175 def signature(self, value):
176 return base64_hmac(
177 self.salt + "signer", value, self.key, algorithm=self.algorithm
178 )
180 def sign(self, value):
181 return "%s%s%s" % (value, self.sep, self.signature(value))
183 def unsign(self, signed_value):
184 if self.sep not in signed_value:
185 raise BadSignature('No "%s" found in value' % self.sep)
186 value, sig = signed_value.rsplit(self.sep, 1)
187 if constant_time_compare(sig, self.signature(value)):
188 return value
189 raise BadSignature('Signature "%s" does not match' % sig)
191 def sign_object(self, obj, serializer=JSONSerializer, compress=False):
192 """
193 Return URL-safe, hmac signed base64 compressed JSON string.
195 If compress is True (not the default), check if compressing using zlib
196 can save some space. Prepend a '.' to signify compression. This is
197 included in the signature, to protect against zip bombs.
199 The serializer is expected to return a bytestring.
200 """
201 data = serializer().dumps(obj)
202 # Flag for if it's been compressed or not.
203 is_compressed = False
205 if compress:
206 # Avoid zlib dependency unless compress is being used.
207 compressed = zlib.compress(data)
208 if len(compressed) < (len(data) - 1):
209 data = compressed
210 is_compressed = True
211 base64d = b64_encode(data).decode()
212 if is_compressed:
213 base64d = "." + base64d
214 return self.sign(base64d)
216 def unsign_object(self, signed_obj, serializer=JSONSerializer, **kwargs):
217 # Signer.unsign() returns str but base64 and zlib compression operate
218 # on bytes.
219 base64d = self.unsign(signed_obj, **kwargs).encode()
220 decompress = base64d[:1] == b"."
221 if decompress:
222 # It's compressed; uncompress it first.
223 base64d = base64d[1:]
224 data = b64_decode(base64d)
225 if decompress:
226 data = zlib.decompress(data)
227 return serializer().loads(data)
230class TimestampSigner(Signer):
231 def timestamp(self):
232 return b62_encode(int(time.time()))
234 def sign(self, value):
235 value = "%s%s%s" % (value, self.sep, self.timestamp())
236 return super().sign(value)
238 def unsign(self, value, max_age=None):
239 """
240 Retrieve original value and check it wasn't signed more
241 than max_age seconds ago.
242 """
243 result = super().unsign(value)
244 value, timestamp = result.rsplit(self.sep, 1)
245 timestamp = b62_decode(timestamp)
246 if max_age is not None:
247 if isinstance(max_age, datetime.timedelta):
248 max_age = max_age.total_seconds()
249 # Check timestamp is not older than max_age
250 age = time.time() - timestamp
251 if age > max_age:
252 raise SignatureExpired("Signature age %s > %s seconds" % (age, max_age))
253 return value