Add google-endpoints to third_party/.

third_party/google-endpoints/Crypto/Hash/HMAC.py

+# HMAC.py - Implements the HMAC algorithm as described by RFC 2104.
+#
+# ===================================================================
+# Portions Copyright (c) 2001, 2002, 2003 Python Software Foundation;
+# All Rights Reserved
+#
+# This file contains code from the Python 2.2 hmac.py module (the
+# "Original Code"), with modifications made after it was incorporated
+# into PyCrypto (the "Modifications").
+#
+# To the best of our knowledge, the Python Software Foundation is the
+# copyright holder of the Original Code, and has licensed it under the
+# Python 2.2 license.  See the file LEGAL/copy/LICENSE.python-2.2 for
+# details.
+#
+# The Modifications to this file are dedicated to the public domain.
+# To the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.  No rights are
+# reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+
+"""HMAC (Hash-based Message Authentication Code) algorithm
+
+HMAC is a MAC defined in RFC2104_ and FIPS-198_ and constructed using
+a cryptograpic hash algorithm.
+It is usually named *HMAC-X*, where *X* is the hash algorithm; for
+instance *HMAC-SHA1* or *HMAC-MD5*.
+
+The strength of an HMAC depends on:
+
+ - the strength of the hash algorithm
+ - the length and entropy of the secret key
+
+An example of possible usage is the following:
+
+    >>> from Crypto.Hash import HMAC
+    >>>
+    >>> secret = b'Swordfish'
+    >>> h = HMAC.new(secret)
+    >>> h.update(b'Hello')
+    >>> print h.hexdigest()
+
+.. _RFC2104: http://www.ietf.org/rfc/rfc2104.txt
+.. _FIPS-198: http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
+"""
+
+# This is just a copy of the Python 2.2 HMAC module, modified to work when
+# used on versions of Python before 2.2.
+
+__revision__ = "$Id$"
+
+__all__ = ['new', 'digest_size', 'HMAC' ]
+
+from Crypto.Util.strxor import strxor_c
+from Crypto.Util.py3compat import *
+
+#: The size of the authentication tag produced by the MAC.
+#: It matches the digest size on the underlying
+#: hashing module used.
+digest_size = None
+
+class HMAC:
+    """Class that implements HMAC"""
+
+    #: The size of the authentication tag produced by the MAC.
+    #: It matches the digest size on the underlying
+    #: hashing module used.
+    digest_size = None
+    
+    def __init__(self, key, msg = None, digestmod = None):
+        """Create a new HMAC object.
+
+        :Parameters:
+          key : byte string
+            secret key for the MAC object.
+            It must be long enough to match the expected security level of the
+            MAC. However, there is no benefit in using keys longer than the
+            `digest_size` of the underlying hash algorithm.
+          msg : byte string
+            The very first chunk of the message to authenticate.
+            It is equivalent to an early call to `update()`. Optional.
+        :Parameter digestmod:
+            The hash algorithm the HMAC is based on.
+            Default is `Crypto.Hash.MD5`.
+        :Type digestmod:
+            A hash module or object instantiated from `Crypto.Hash`
+        """
+        if digestmod is None:
+            import MD5
+            digestmod = MD5
+
+        self.digestmod = digestmod
+        self.outer = digestmod.new()
+        self.inner = digestmod.new()
+        try:
+            self.digest_size = digestmod.digest_size
+        except AttributeError:
+            self.digest_size = len(self.outer.digest())
+
+        try:
+            # The block size is 128 bytes for SHA384 and SHA512 and 64 bytes
+            # for the others hash function
+            blocksize = digestmod.block_size
+        except AttributeError:
+            blocksize = 64
+
+        ipad = 0x36
+        opad = 0x5C
+
+        if len(key) > blocksize:
+            key = digestmod.new(key).digest()
+
+        key = key + bchr(0) * (blocksize - len(key))
+        self.outer.update(strxor_c(key, opad))
+        self.inner.update(strxor_c(key, ipad))
+        if (msg):
+            self.update(msg)
+
+    def update(self, msg):
+        """Continue authentication of a message by consuming the next chunk of data.
+        
+        Repeated calls are equivalent to a single call with the concatenation
+        of all the arguments. In other words:
+
+           >>> m.update(a); m.update(b)
+           
+        is equivalent to:
+        
+           >>> m.update(a+b)
+
+        :Parameters:
+          msg : byte string
+            The next chunk of the message being authenticated
+        """
+ 
+        self.inner.update(msg)
+
+    def copy(self):
+        """Return a copy ("clone") of the MAC object.
+
+        The copy will have the same internal state as the original MAC
+        object.
+        This can be used to efficiently compute the MAC of strings that
+        share a common initial substring.
+
+        :Returns: An `HMAC` object
+        """
+        other = HMAC(b(""))
+        other.digestmod = self.digestmod
+        other.inner = self.inner.copy()
+        other.outer = self.outer.copy()
+        return other
+
+    def digest(self):
+        """Return the **binary** (non-printable) MAC of the message that has
+        been authenticated so far.
+
+        This method does not change the state of the MAC object.
+        You can continue updating the object after calling this function.
+        
+        :Return: A byte string of `digest_size` bytes. It may contain non-ASCII
+         characters, including null bytes.
+        """
+        h = self.outer.copy()
+        h.update(self.inner.digest())
+        return h.digest()
+
+    def hexdigest(self):
+        """Return the **printable** MAC of the message that has been
+        authenticated so far.
+
+        This method does not change the state of the MAC object.
+        
+        :Return: A string of 2* `digest_size` bytes. It contains only
+         hexadecimal ASCII digits.
+        """
+        return "".join(["%02x" % bord(x)
+                  for x in tuple(self.digest())])
+
+def new(key, msg = None, digestmod = None):
+    """Create a new HMAC object.
+
+    :Parameters:
+      key : byte string
+        key for the MAC object.
+        It must be long enough to match the expected security level of the
+        MAC. However, there is no benefit in using keys longer than the
+        `digest_size` of the underlying hash algorithm.
+      msg : byte string
+        The very first chunk of the message to authenticate.
+        It is equivalent to an early call to `HMAC.update()`.
+        Optional.
+    :Parameter digestmod:
+        The hash to use to implement the HMAC. Default is `Crypto.Hash.MD5`.
+    :Type digestmod:
+        A hash module or instantiated object from `Crypto.Hash`
+    :Returns: An `HMAC` object
+    """
+    return HMAC(key, msg, digestmod)
+