Add google-endpoints to third_party/.

third_party/google-endpoints/Crypto/Signature/PKCS1_PSS.py

Index: third_party/google-endpoints/Crypto/Signature/PKCS1_PSS.py
diff --git a/third_party/google-endpoints/Crypto/Signature/PKCS1_PSS.py b/third_party/google-endpoints/Crypto/Signature/PKCS1_PSS.py
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+# -*- coding: utf-8 -*-
+#
+#  Signature/PKCS1_PSS.py : PKCS#1 PPS
+#
+# ===================================================================
+# The contents of 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.
+# ===================================================================
+
+"""RSA digital signature protocol with appendix according to PKCS#1 PSS.
+
+See RFC3447__ or the `original RSA Labs specification`__.
+
+This scheme is more properly called ``RSASSA-PSS``.
+
+For example, a sender may authenticate a message using SHA-1 and PSS like
+this:
+
+    >>> from Crypto.Signature import PKCS1_PSS
+    >>> from Crypto.Hash import SHA
+    >>> from Crypto.PublicKey import RSA
+    >>> from Crypto import Random
+    >>>
+    >>> message = 'To be signed'
+    >>> key = RSA.importKey(open('privkey.der').read())
+    >>> h = SHA.new()
+    >>> h.update(message)
+    >>> signer = PKCS1_PSS.new(key)
+    >>> signature = PKCS1_PSS.sign(key)
+
+At the receiver side, verification can be done like using the public part of
+the RSA key:
+
+    >>> key = RSA.importKey(open('pubkey.der').read())
+    >>> h = SHA.new()
+    >>> h.update(message)
+    >>> verifier = PKCS1_PSS.new(key)
+    >>> if verifier.verify(h, signature):
+    >>>     print "The signature is authentic."
+    >>> else:
+    >>>     print "The signature is not authentic."
+
+:undocumented: __revision__, __package__
+
+.. __: http://www.ietf.org/rfc/rfc3447.txt
+.. __: http://www.rsa.com/rsalabs/node.asp?id=2125
+"""
+
+# Allow nested scopes in Python 2.1
+# See http://oreilly.com/pub/a/python/2001/04/19/pythonnews.html
+from __future__ import nested_scopes
+
+__revision__ = "$Id$"
+__all__ = [ 'new', 'PSS_SigScheme' ]
+
+from Crypto.Util.py3compat import *
+if sys.version_info[0] == 2 and sys.version_info[1] == 1:
+    from Crypto.Util.py21compat import *
+import Crypto.Util.number
+from Crypto.Util.number import ceil_shift, ceil_div, long_to_bytes
+from Crypto.Util.strxor import strxor
+
+class PSS_SigScheme:
+    """This signature scheme can perform PKCS#1 PSS RSA signature or verification."""
+
+    def __init__(self, key, mgfunc, saltLen):
+        """Initialize this PKCS#1 PSS signature scheme object.
+        
+        :Parameters:
+         key : an RSA key object
+                If a private half is given, both signature and verification are possible.
+                If a public half is given, only verification is possible.
+         mgfunc : callable
+                A mask generation function that accepts two parameters: a string to
+                use as seed, and the lenth of the mask to generate, in bytes.
+         saltLen : int
+                Length of the salt, in bytes.
+        """
+        self._key = key
+        self._saltLen = saltLen
+        self._mgfunc = mgfunc
+
+    def can_sign(self):
+        """Return True if this cipher object can be used for signing messages."""
+        return self._key.has_private()
+ 
+    def sign(self, mhash):
+        """Produce the PKCS#1 PSS signature of a message.
+    
+        This function is named ``RSASSA-PSS-SIGN``, and is specified in
+        section 8.1.1 of RFC3447.
+    
+        :Parameters:
+         mhash : hash object
+                The hash that was carried out over the message. This is an object
+                belonging to the `Crypto.Hash` module.
+   
+        :Return: The PSS signature encoded as a string.
+        :Raise ValueError:
+            If the RSA key length is not sufficiently long to deal with the given
+            hash algorithm.
+        :Raise TypeError:
+            If the RSA key has no private half.
+    
+        :attention: Modify the salt length and the mask generation function only
+                    if you know what you are doing.
+                    The receiver must use the same parameters too.
+        """
+        # TODO: Verify the key is RSA
+    
+        randfunc = self._key._randfunc
+        
+        # Set defaults for salt length and mask generation function
+        if self._saltLen == None:
+            sLen = mhash.digest_size
+        else:
+            sLen = self._saltLen
+        if self._mgfunc:
+            mgf = self._mgfunc
+        else:
+             mgf  = lambda x,y: MGF1(x,y,mhash)
+ 
+        modBits = Crypto.Util.number.size(self._key.n)
+    
+        # See 8.1.1 in RFC3447
+        k = ceil_div(modBits,8) # Convert from bits to bytes
+        # Step 1
+        em = EMSA_PSS_ENCODE(mhash, modBits-1, randfunc, mgf, sLen)
+        # Step 2a (OS2IP) and 2b (RSASP1)
+        m = self._key.decrypt(em)
+        # Step 2c (I2OSP)
+        S = bchr(0x00)*(k-len(m)) + m
+        return S
+    
+    def verify(self, mhash, S):
+        """Verify that a certain PKCS#1 PSS signature is authentic.
+    
+        This function checks if the party holding the private half of the given
+        RSA key has really signed the message.
+    
+        This function is called ``RSASSA-PSS-VERIFY``, and is specified in section
+        8.1.2 of RFC3447.
+    
+        :Parameters:
+         mhash : hash object
+                The hash that was carried out over the message. This is an object
+                belonging to the `Crypto.Hash` module.
+         S : string
+                The signature that needs to be validated.
+    
+        :Return: True if verification is correct. False otherwise.
+        """
+        # TODO: Verify the key is RSA
+    
+        # Set defaults for salt length and mask generation function
+        if self._saltLen == None:
+            sLen = mhash.digest_size
+        else:
+            sLen = self._saltLen
+        if self._mgfunc:
+            mgf = self._mgfunc
+        else:
+            mgf  = lambda x,y: MGF1(x,y,mhash)
+
+        modBits = Crypto.Util.number.size(self._key.n)
+    
+        # See 8.1.2 in RFC3447
+        k = ceil_div(modBits,8) # Convert from bits to bytes
+        # Step 1
+        if len(S) != k:
+            return False
+        # Step 2a (O2SIP), 2b (RSAVP1), and partially 2c (I2OSP)
+        # Note that signature must be smaller than the module
+        # but RSA.py won't complain about it.
+        # TODO: Fix RSA object; don't do it here.
+        em = self._key.encrypt(S, 0)[0]
+        # Step 2c
+        emLen = ceil_div(modBits-1,8)
+        em = bchr(0x00)*(emLen-len(em)) + em
+        # Step 3
+        try:
+            result = EMSA_PSS_VERIFY(mhash, em, modBits-1, mgf, sLen)
+        except ValueError:
+            return False
+        # Step 4
+        return result
+    
+def MGF1(mgfSeed, maskLen, hash):
+    """Mask Generation Function, described in B.2.1"""
+    T = b("")
+    for counter in xrange(ceil_div(maskLen, hash.digest_size)):
+        c = long_to_bytes(counter, 4)
+        T = T + hash.new(mgfSeed + c).digest()
+    assert(len(T)>=maskLen)
+    return T[:maskLen]
+
+def EMSA_PSS_ENCODE(mhash, emBits, randFunc, mgf, sLen):
+    """
+    Implement the ``EMSA-PSS-ENCODE`` function, as defined
+    in PKCS#1 v2.1 (RFC3447, 9.1.1).
+
+    The original ``EMSA-PSS-ENCODE`` actually accepts the message ``M`` as input,
+    and hash it internally. Here, we expect that the message has already
+    been hashed instead.
+
+    :Parameters:
+     mhash : hash object
+            The hash object that holds the digest of the message being signed.
+     emBits : int
+            Maximum length of the final encoding, in bits.
+     randFunc : callable
+            An RNG function that accepts as only parameter an int, and returns
+            a string of random bytes, to be used as salt.
+     mgf : callable
+            A mask generation function that accepts two parameters: a string to
+            use as seed, and the lenth of the mask to generate, in bytes.
+     sLen : int
+            Length of the salt, in bytes.
+
+    :Return: An ``emLen`` byte long string that encodes the hash
+            (with ``emLen = \ceil(emBits/8)``).
+
+    :Raise ValueError:
+        When digest or salt length are too big.
+    """
+
+    emLen = ceil_div(emBits,8)
+
+    # Bitmask of digits that fill up
+    lmask = 0
+    for i in xrange(8*emLen-emBits):
+        lmask = lmask>>1 | 0x80
+
+    # Step 1 and 2 have been already done
+    # Step 3
+    if emLen < mhash.digest_size+sLen+2:
+        raise ValueError("Digest or salt length are too long for given key size.")
+    # Step 4
+    salt = b("")
+    if randFunc and sLen>0:
+        salt = randFunc(sLen)
+    # Step 5 and 6
+    h = mhash.new(bchr(0x00)*8 + mhash.digest() + salt)
+    # Step 7 and 8
+    db = bchr(0x00)*(emLen-sLen-mhash.digest_size-2) + bchr(0x01) + salt
+    # Step 9
+    dbMask = mgf(h.digest(), emLen-mhash.digest_size-1)
+    # Step 10
+    maskedDB = strxor(db,dbMask)
+    # Step 11
+    maskedDB = bchr(bord(maskedDB[0]) & ~lmask) + maskedDB[1:]
+    # Step 12
+    em = maskedDB + h.digest() + bchr(0xBC)
+    return em
+
+def EMSA_PSS_VERIFY(mhash, em, emBits, mgf, sLen):
+    """
+    Implement the ``EMSA-PSS-VERIFY`` function, as defined
+    in PKCS#1 v2.1 (RFC3447, 9.1.2).
+
+    ``EMSA-PSS-VERIFY`` actually accepts the message ``M`` as input,
+    and hash it internally. Here, we expect that the message has already
+    been hashed instead.
+
+    :Parameters:
+     mhash : hash object
+            The hash object that holds the digest of the message to be verified.
+     em : string
+            The signature to verify, therefore proving that the sender really signed
+            the message that was received.
+     emBits : int
+            Length of the final encoding (em), in bits.
+     mgf : callable
+            A mask generation function that accepts two parameters: a string to
+            use as seed, and the lenth of the mask to generate, in bytes.
+     sLen : int
+            Length of the salt, in bytes.
+
+    :Return: 0 if the encoding is consistent, 1 if it is inconsistent.
+
+    :Raise ValueError:
+        When digest or salt length are too big.
+    """
+
+    emLen = ceil_div(emBits,8)
+
+    # Bitmask of digits that fill up
+    lmask = 0
+    for i in xrange(8*emLen-emBits):
+        lmask = lmask>>1 | 0x80
+
+    # Step 1 and 2 have been already done
+    # Step 3
+    if emLen < mhash.digest_size+sLen+2:
+        return False
+    # Step 4
+    if ord(em[-1:])!=0xBC:
+        return False
+    # Step 5
+    maskedDB = em[:emLen-mhash.digest_size-1]
+    h = em[emLen-mhash.digest_size-1:-1]
+    # Step 6
+    if lmask & bord(em[0]):
+        return False
+    # Step 7
+    dbMask = mgf(h, emLen-mhash.digest_size-1)
+    # Step 8
+    db = strxor(maskedDB, dbMask)
+    # Step 9
+    db = bchr(bord(db[0]) & ~lmask) + db[1:]
+    # Step 10
+    if not db.startswith(bchr(0x00)*(emLen-mhash.digest_size-sLen-2) + bchr(0x01)):
+        return False
+    # Step 11
+    salt = b("")
+    if sLen: salt = db[-sLen:]
+    # Step 12 and 13
+    hp = mhash.new(bchr(0x00)*8 + mhash.digest() + salt).digest()
+    # Step 14
+    if h!=hp:
+        return False
+    return True
+
+def new(key, mgfunc=None, saltLen=None):
+    """Return a signature scheme object `PSS_SigScheme` that
+    can be used to perform PKCS#1 PSS signature or verification.
+
+    :Parameters:
+     key : RSA key object
+        The key to use to sign or verify the message. This is a `Crypto.PublicKey.RSA` object.
+        Signing is only possible if *key* is a private RSA key.
+     mgfunc : callable
+        A mask generation function that accepts two parameters: a string to
+        use as seed, and the lenth of the mask to generate, in bytes.
+        If not specified, the standard MGF1 is used.
+     saltLen : int
+        Length of the salt, in bytes. If not specified, it matches the output
+        size of the hash function.
+ 
+    """
+    return PSS_SigScheme(key, mgfunc, saltLen)
+