1"""HMAC (Keyed-Hashing for Message Authentication) module. 2 3Implements the HMAC algorithm as described by RFC 2104. 4""" 5 6import warnings as _warnings 7try: 8 import _hashlib as _hashopenssl 9except ImportError: 10 _hashopenssl = None 11 _functype = None 12 from _operator import _compare_digest as compare_digest 13else: 14 compare_digest = _hashopenssl.compare_digest 15 _functype = type(_hashopenssl.openssl_sha256) # builtin type 16 17import hashlib as _hashlib 18 19trans_5C = bytes((x ^ 0x5C) for x in range(256)) 20trans_36 = bytes((x ^ 0x36) for x in range(256)) 21 22# The size of the digests returned by HMAC depends on the underlying 23# hashing module used. Use digest_size from the instance of HMAC instead. 24digest_size = None 25 26 27class HMAC: 28 """RFC 2104 HMAC class. Also complies with RFC 4231. 29 30 This supports the API for Cryptographic Hash Functions (PEP 247). 31 """ 32 blocksize = 64 # 512-bit HMAC; can be changed in subclasses. 33 34 __slots__ = ( 35 "_hmac", "_inner", "_outer", "block_size", "digest_size" 36 ) 37 38 def __init__(self, key, msg=None, digestmod=''): 39 """Create a new HMAC object. 40 41 key: bytes or buffer, key for the keyed hash object. 42 msg: bytes or buffer, Initial input for the hash or None. 43 digestmod: A hash name suitable for hashlib.new(). *OR* 44 A hashlib constructor returning a new hash object. *OR* 45 A module supporting PEP 247. 46 47 Required as of 3.8, despite its position after the optional 48 msg argument. Passing it as a keyword argument is 49 recommended, though not required for legacy API reasons. 50 """ 51 52 if not isinstance(key, (bytes, bytearray)): 53 raise TypeError("key: expected bytes or bytearray, but got %r" % type(key).__name__) 54 55 if not digestmod: 56 raise TypeError("Missing required parameter 'digestmod'.") 57 58 if _hashopenssl and isinstance(digestmod, (str, _functype)): 59 try: 60 self._init_hmac(key, msg, digestmod) 61 except _hashopenssl.UnsupportedDigestmodError: 62 self._init_old(key, msg, digestmod) 63 else: 64 self._init_old(key, msg, digestmod) 65 66 def _init_hmac(self, key, msg, digestmod): 67 self._hmac = _hashopenssl.hmac_new(key, msg, digestmod=digestmod) 68 self.digest_size = self._hmac.digest_size 69 self.block_size = self._hmac.block_size 70 71 def _init_old(self, key, msg, digestmod): 72 if callable(digestmod): 73 digest_cons = digestmod 74 elif isinstance(digestmod, str): 75 digest_cons = lambda d=b'': _hashlib.new(digestmod, d) 76 else: 77 digest_cons = lambda d=b'': digestmod.new(d) 78 79 self._hmac = None 80 self._outer = digest_cons() 81 self._inner = digest_cons() 82 self.digest_size = self._inner.digest_size 83 84 if hasattr(self._inner, 'block_size'): 85 blocksize = self._inner.block_size 86 if blocksize < 16: 87 _warnings.warn('block_size of %d seems too small; using our ' 88 'default of %d.' % (blocksize, self.blocksize), 89 RuntimeWarning, 2) 90 blocksize = self.blocksize 91 else: 92 _warnings.warn('No block_size attribute on given digest object; ' 93 'Assuming %d.' % (self.blocksize), 94 RuntimeWarning, 2) 95 blocksize = self.blocksize 96 97 if len(key) > blocksize: 98 key = digest_cons(key).digest() 99 100 # self.blocksize is the default blocksize. self.block_size is 101 # effective block size as well as the public API attribute. 102 self.block_size = blocksize 103 104 key = key.ljust(blocksize, b'\0') 105 self._outer.update(key.translate(trans_5C)) 106 self._inner.update(key.translate(trans_36)) 107 if msg is not None: 108 self.update(msg) 109 110 @property 111 def name(self): 112 if self._hmac: 113 return self._hmac.name 114 else: 115 return f"hmac-{self._inner.name}" 116 117 def update(self, msg): 118 """Feed data from msg into this hashing object.""" 119 inst = self._hmac or self._inner 120 inst.update(msg) 121 122 def copy(self): 123 """Return a separate copy of this hashing object. 124 125 An update to this copy won't affect the original object. 126 """ 127 # Call __new__ directly to avoid the expensive __init__. 128 other = self.__class__.__new__(self.__class__) 129 other.digest_size = self.digest_size 130 if self._hmac: 131 other._hmac = self._hmac.copy() 132 other._inner = other._outer = None 133 else: 134 other._hmac = None 135 other._inner = self._inner.copy() 136 other._outer = self._outer.copy() 137 return other 138 139 def _current(self): 140 """Return a hash object for the current state. 141 142 To be used only internally with digest() and hexdigest(). 143 """ 144 if self._hmac: 145 return self._hmac 146 else: 147 h = self._outer.copy() 148 h.update(self._inner.digest()) 149 return h 150 151 def digest(self): 152 """Return the hash value of this hashing object. 153 154 This returns the hmac value as bytes. The object is 155 not altered in any way by this function; you can continue 156 updating the object after calling this function. 157 """ 158 h = self._current() 159 return h.digest() 160 161 def hexdigest(self): 162 """Like digest(), but returns a string of hexadecimal digits instead. 163 """ 164 h = self._current() 165 return h.hexdigest() 166 167def new(key, msg=None, digestmod=''): 168 """Create a new hashing object and return it. 169 170 key: bytes or buffer, The starting key for the hash. 171 msg: bytes or buffer, Initial input for the hash, or None. 172 digestmod: A hash name suitable for hashlib.new(). *OR* 173 A hashlib constructor returning a new hash object. *OR* 174 A module supporting PEP 247. 175 176 Required as of 3.8, despite its position after the optional 177 msg argument. Passing it as a keyword argument is 178 recommended, though not required for legacy API reasons. 179 180 You can now feed arbitrary bytes into the object using its update() 181 method, and can ask for the hash value at any time by calling its digest() 182 or hexdigest() methods. 183 """ 184 return HMAC(key, msg, digestmod) 185 186 187def digest(key, msg, digest): 188 """Fast inline implementation of HMAC. 189 190 key: bytes or buffer, The key for the keyed hash object. 191 msg: bytes or buffer, Input message. 192 digest: A hash name suitable for hashlib.new() for best performance. *OR* 193 A hashlib constructor returning a new hash object. *OR* 194 A module supporting PEP 247. 195 """ 196 if _hashopenssl is not None and isinstance(digest, (str, _functype)): 197 try: 198 return _hashopenssl.hmac_digest(key, msg, digest) 199 except _hashopenssl.UnsupportedDigestmodError: 200 pass 201 202 if callable(digest): 203 digest_cons = digest 204 elif isinstance(digest, str): 205 digest_cons = lambda d=b'': _hashlib.new(digest, d) 206 else: 207 digest_cons = lambda d=b'': digest.new(d) 208 209 inner = digest_cons() 210 outer = digest_cons() 211 blocksize = getattr(inner, 'block_size', 64) 212 if len(key) > blocksize: 213 key = digest_cons(key).digest() 214 key = key + b'\x00' * (blocksize - len(key)) 215 inner.update(key.translate(trans_36)) 216 outer.update(key.translate(trans_5C)) 217 inner.update(msg) 218 outer.update(inner.digest()) 219 return outer.digest() 220