Package tlslite :: Module handshakesettings
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Source Code for Module tlslite.handshakesettings

  1  # Authors:  
  2  #   Trevor Perrin 
  3  #   Dave Baggett (Arcode Corporation) - cleanup handling of constants 
  4  # 
  5  # See the LICENSE file for legal information regarding use of this file. 
  6   
  7  """Class for setting handshake parameters.""" 
  8   
  9  from .constants import CertificateType 
 10  from .utils import cryptomath 
 11  from .utils import cipherfactory 
 12   
 13  # RC4 is preferred as faster in Python, works in SSL3, and immune to CBC 
 14  # issues such as timing attacks 
 15  CIPHER_NAMES = ["rc4", "aes256", "aes128", "3des"] 
 16  MAC_NAMES = ["sha"] # "md5" is allowed 
 17  CIPHER_IMPLEMENTATIONS = ["openssl", "pycrypto", "python"] 
 18  CERTIFICATE_TYPES = ["x509"] 
 19   
20 -class HandshakeSettings(object):
21 """This class encapsulates various parameters that can be used with 22 a TLS handshake. 23 @sort: minKeySize, maxKeySize, cipherNames, macNames, certificateTypes, 24 minVersion, maxVersion 25 26 @type minKeySize: int 27 @ivar minKeySize: The minimum bit length for asymmetric keys. 28 29 If the other party tries to use SRP, RSA, or Diffie-Hellman 30 parameters smaller than this length, an alert will be 31 signalled. The default is 1023. 32 33 @type maxKeySize: int 34 @ivar maxKeySize: The maximum bit length for asymmetric keys. 35 36 If the other party tries to use SRP, RSA, or Diffie-Hellman 37 parameters larger than this length, an alert will be signalled. 38 The default is 8193. 39 40 @type cipherNames: list 41 @ivar cipherNames: The allowed ciphers, in order of preference. 42 43 The allowed values in this list are 'aes256', 'aes128', '3des', and 44 'rc4'. If these settings are used with a client handshake, they 45 determine the order of the ciphersuites offered in the ClientHello 46 message. 47 48 If these settings are used with a server handshake, the server will 49 choose whichever ciphersuite matches the earliest entry in this 50 list. 51 52 NOTE: If '3des' is used in this list, but TLS Lite can't find an 53 add-on library that supports 3DES, then '3des' will be silently 54 removed. 55 56 The default value is ['rc4', 'aes256', 'aes128', '3des']. 57 58 @type macNames: list 59 @ivar macNames: The allowed MAC algorithms. 60 61 The allowed values in this list are 'sha' and 'md5'. 62 63 The default value is ['sha']. 64 65 66 @type certificateTypes: list 67 @ivar certificateTypes: The allowed certificate types, in order of 68 preference. 69 70 The only allowed certificate type is 'x509'. This list is only used with a 71 client handshake. The client will advertise to the server which certificate 72 types are supported, and will check that the server uses one of the 73 appropriate types. 74 75 76 @type minVersion: tuple 77 @ivar minVersion: The minimum allowed SSL/TLS version. 78 79 This variable can be set to (3,0) for SSL 3.0, (3,1) for 80 TLS 1.0, or (3,2) for TLS 1.1. If the other party wishes to 81 use a lower version, a protocol_version alert will be signalled. 82 The default is (3,0). 83 84 @type maxVersion: tuple 85 @ivar maxVersion: The maximum allowed SSL/TLS version. 86 87 This variable can be set to (3,0) for SSL 3.0, (3,1) for 88 TLS 1.0, or (3,2) for TLS 1.1. If the other party wishes to 89 use a higher version, a protocol_version alert will be signalled. 90 The default is (3,2). (WARNING: Some servers may (improperly) 91 reject clients which offer support for TLS 1.1. In this case, 92 try lowering maxVersion to (3,1)). 93 94 @type useExperimentalTackExtension: bool 95 @ivar useExperimentalTackExtension: Whether to enabled TACK support. 96 97 Note that TACK support is not standardized by IETF and uses a temporary 98 TLS Extension number, so should NOT be used in production software. 99 """
100 - def __init__(self):
101 self.minKeySize = 1023 102 self.maxKeySize = 8193 103 self.cipherNames = CIPHER_NAMES 104 self.macNames = MAC_NAMES 105 self.cipherImplementations = CIPHER_IMPLEMENTATIONS 106 self.certificateTypes = CERTIFICATE_TYPES 107 self.minVersion = (3,0) 108 self.maxVersion = (3,2) 109 self.useExperimentalTackExtension = False
110 111 # Validates the min/max fields, and certificateTypes 112 # Filters out unsupported cipherNames and cipherImplementations
113 - def _filter(self):
114 other = HandshakeSettings() 115 other.minKeySize = self.minKeySize 116 other.maxKeySize = self.maxKeySize 117 other.cipherNames = self.cipherNames 118 other.macNames = self.macNames 119 other.cipherImplementations = self.cipherImplementations 120 other.certificateTypes = self.certificateTypes 121 other.minVersion = self.minVersion 122 other.maxVersion = self.maxVersion 123 124 if not cipherfactory.tripleDESPresent: 125 other.cipherNames = [e for e in self.cipherNames if e != "3des"] 126 if len(other.cipherNames)==0: 127 raise ValueError("No supported ciphers") 128 if len(other.certificateTypes)==0: 129 raise ValueError("No supported certificate types") 130 131 if not cryptomath.m2cryptoLoaded: 132 other.cipherImplementations = \ 133 [e for e in other.cipherImplementations if e != "openssl"] 134 if not cryptomath.pycryptoLoaded: 135 other.cipherImplementations = \ 136 [e for e in other.cipherImplementations if e != "pycrypto"] 137 if len(other.cipherImplementations)==0: 138 raise ValueError("No supported cipher implementations") 139 140 if other.minKeySize<512: 141 raise ValueError("minKeySize too small") 142 if other.minKeySize>16384: 143 raise ValueError("minKeySize too large") 144 if other.maxKeySize<512: 145 raise ValueError("maxKeySize too small") 146 if other.maxKeySize>16384: 147 raise ValueError("maxKeySize too large") 148 for s in other.cipherNames: 149 if s not in CIPHER_NAMES: 150 raise ValueError("Unknown cipher name: '%s'" % s) 151 for s in other.cipherImplementations: 152 if s not in CIPHER_IMPLEMENTATIONS: 153 raise ValueError("Unknown cipher implementation: '%s'" % s) 154 for s in other.certificateTypes: 155 if s not in CERTIFICATE_TYPES: 156 raise ValueError("Unknown certificate type: '%s'" % s) 157 158 if other.minVersion > other.maxVersion: 159 raise ValueError("Versions set incorrectly") 160 161 if not other.minVersion in ((3,0), (3,1), (3,2)): 162 raise ValueError("minVersion set incorrectly") 163 164 if not other.maxVersion in ((3,0), (3,1), (3,2)): 165 raise ValueError("maxVersion set incorrectly") 166 167 return other
168
169 - def _getCertificateTypes(self):
170 l = [] 171 for ct in self.certificateTypes: 172 if ct == "x509": 173 l.append(CertificateType.x509) 174 else: 175 raise AssertionError() 176 return l
177