1# Author: Trevor Perrin 2# See the LICENSE file for legal information regarding use of this file. 3 4"""Class for storing SRP password verifiers.""" 5 6from .utils.cryptomath import * 7from .utils.compat import * 8from tlslite import mathtls 9from .basedb import BaseDB 10 11class VerifierDB(BaseDB): 12 """This class represent an in-memory or on-disk database of SRP 13 password verifiers. 14 15 A VerifierDB can be passed to a server handshake to authenticate 16 a client based on one of the verifiers. 17 18 This class is thread-safe. 19 """ 20 def __init__(self, filename=None): 21 """Create a new VerifierDB instance. 22 23 @type filename: str 24 @param filename: Filename for an on-disk database, or None for 25 an in-memory database. If the filename already exists, follow 26 this with a call to open(). To create a new on-disk database, 27 follow this with a call to create(). 28 """ 29 BaseDB.__init__(self, filename, "verifier") 30 31 def _getItem(self, username, valueStr): 32 (N, g, salt, verifier) = valueStr.split(" ") 33 N = bytesToNumber(a2b_base64(N)) 34 g = bytesToNumber(a2b_base64(g)) 35 salt = a2b_base64(salt) 36 verifier = bytesToNumber(a2b_base64(verifier)) 37 return (N, g, salt, verifier) 38 39 def __setitem__(self, username, verifierEntry): 40 """Add a verifier entry to the database. 41 42 @type username: str 43 @param username: The username to associate the verifier with. 44 Must be less than 256 characters in length. Must not already 45 be in the database. 46 47 @type verifierEntry: tuple 48 @param verifierEntry: The verifier entry to add. Use 49 L{tlslite.verifierdb.VerifierDB.makeVerifier} to create a 50 verifier entry. 51 """ 52 BaseDB.__setitem__(self, username, verifierEntry) 53 54 55 def _setItem(self, username, value): 56 if len(username)>=256: 57 raise ValueError("username too long") 58 N, g, salt, verifier = value 59 N = b2a_base64(numberToByteArray(N)) 60 g = b2a_base64(numberToByteArray(g)) 61 salt = b2a_base64(salt) 62 verifier = b2a_base64(numberToByteArray(verifier)) 63 valueStr = " ".join( (N, g, salt, verifier) ) 64 return valueStr 65 66 def _checkItem(self, value, username, param): 67 (N, g, salt, verifier) = value 68 x = mathtls.makeX(salt, username, param) 69 v = powMod(g, x, N) 70 return (verifier == v) 71 72 73 def makeVerifier(username, password, bits): 74 """Create a verifier entry which can be stored in a VerifierDB. 75 76 @type username: str 77 @param username: The username for this verifier. Must be less 78 than 256 characters in length. 79 80 @type password: str 81 @param password: The password for this verifier. 82 83 @type bits: int 84 @param bits: This values specifies which SRP group parameters 85 to use. It must be one of (1024, 1536, 2048, 3072, 4096, 6144, 86 8192). Larger values are more secure but slower. 2048 is a 87 good compromise between safety and speed. 88 89 @rtype: tuple 90 @return: A tuple which may be stored in a VerifierDB. 91 """ 92 usernameBytes = bytearray(username, "utf-8") 93 passwordBytes = bytearray(password, "utf-8") 94 return mathtls.makeVerifier(usernameBytes, passwordBytes, bits) 95 makeVerifier = staticmethod(makeVerifier) 96