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python/gdata/tlslite/VerifierDB.py

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+"""Class for storing SRP password verifiers."""
+
+from utils.cryptomath import *
+from utils.compat import *
+import mathtls
+from BaseDB import BaseDB
+
+class VerifierDB(BaseDB):
+    """This class represent an in-memory or on-disk database of SRP
+    password verifiers.
+
+    A VerifierDB can be passed to a server handshake to authenticate
+    a client based on one of the verifiers.
+
+    This class is thread-safe.
+    """
+    def __init__(self, filename=None):
+        """Create a new VerifierDB instance.
+
+        @type filename: str
+        @param filename: Filename for an on-disk database, or None for
+        an in-memory database.  If the filename already exists, follow
+        this with a call to open().  To create a new on-disk database,
+        follow this with a call to create().
+        """
+        BaseDB.__init__(self, filename, "verifier")
+
+    def _getItem(self, username, valueStr):
+        (N, g, salt, verifier) = valueStr.split(" ")
+        N = base64ToNumber(N)
+        g = base64ToNumber(g)
+        salt = base64ToString(salt)
+        verifier = base64ToNumber(verifier)
+        return (N, g, salt, verifier)
+
+    def __setitem__(self, username, verifierEntry):
+        """Add a verifier entry to the database.
+
+        @type username: str
+        @param username: The username to associate the verifier with.
+        Must be less than 256 characters in length.  Must not already
+        be in the database.
+
+        @type verifierEntry: tuple
+        @param verifierEntry: The verifier entry to add.  Use
+        L{tlslite.VerifierDB.VerifierDB.makeVerifier} to create a
+        verifier entry.
+        """
+        BaseDB.__setitem__(self, username, verifierEntry)
+
+
+    def _setItem(self, username, value):
+        if len(username)>=256:
+            raise ValueError("username too long")
+        N, g, salt, verifier = value
+        N = numberToBase64(N)
+        g = numberToBase64(g)
+        salt = stringToBase64(salt)
+        verifier = numberToBase64(verifier)
+        valueStr = " ".join( (N, g, salt, verifier)  )
+        return valueStr
+
+    def _checkItem(self, value, username, param):
+        (N, g, salt, verifier) = value
+        x = mathtls.makeX(salt, username, param)
+        v = powMod(g, x, N)
+        return (verifier == v)
+
+
+    def makeVerifier(username, password, bits):
+        """Create a verifier entry which can be stored in a VerifierDB.
+
+        @type username: str
+        @param username: The username for this verifier.  Must be less
+        than 256 characters in length.
+
+        @type password: str
+        @param password: The password for this verifier.
+
+        @type bits: int
+        @param bits: This values specifies which SRP group parameters
+        to use.  It must be one of (1024, 1536, 2048, 3072, 4096, 6144,
+        8192).  Larger values are more secure but slower.  2048 is a
+        good compromise between safety and speed.
+
+        @rtype: tuple
+        @return: A tuple which may be stored in a VerifierDB.
+        """
+        return mathtls.makeVerifier(username, password, bits)
+    makeVerifier = staticmethod(makeVerifier)