| """HMAC (Keyed-Hashing for Message Authentication) module. | |
| Implements the HMAC algorithm as described by RFC 2104. | |
| """ | |
| try: | |
| import _hashlib as _hashopenssl | |
| except ImportError: | |
| _hashopenssl = None | |
| _functype = None | |
| from _operator import _compare_digest as compare_digest | |
| else: | |
| compare_digest = _hashopenssl.compare_digest | |
| _functype = type(_hashopenssl.openssl_sha256) # builtin type | |
| try: | |
| import _hmac | |
| except ImportError: | |
| _hmac = None | |
| trans_5C = bytes((x ^ 0x5C) for x in range(256)) | |
| trans_36 = bytes((x ^ 0x36) for x in range(256)) | |
| # The size of the digests returned by HMAC depends on the underlying | |
| # hashing module used. Use digest_size from the instance of HMAC instead. | |
| digest_size = None | |
| def _is_shake_constructor(digest_like): | |
| if isinstance(digest_like, str): | |
| name = digest_like | |
| else: | |
| h = digest_like() if callable(digest_like) else digest_like.new() | |
| if not isinstance(name := getattr(h, "name", None), str): | |
| return False | |
| return name.startswith(("shake", "SHAKE")) | |
| def _get_digest_constructor(digest_like): | |
| if callable(digest_like): | |
| return digest_like | |
| if isinstance(digest_like, str): | |
| def digest_wrapper(d=b''): | |
| import hashlib | |
| return hashlib.new(digest_like, d) | |
| else: | |
| def digest_wrapper(d=b''): | |
| return digest_like.new(d) | |
| return digest_wrapper | |
| class HMAC: | |
| """RFC 2104 HMAC class. Also complies with RFC 4231. | |
| This supports the API for Cryptographic Hash Functions (PEP 247). | |
| """ | |
| # Note: self.blocksize is the default blocksize; self.block_size | |
| # is effective block size as well as the public API attribute. | |
| blocksize = 64 # 512-bit HMAC; can be changed in subclasses. | |
| __slots__ = ( | |
| "_hmac", "_inner", "_outer", "block_size", "digest_size" | |
| ) | |
| def __init__(self, key, msg=None, digestmod=''): | |
| """Create a new HMAC object. | |
| key: bytes or buffer, key for the keyed hash object. | |
| msg: bytes or buffer, Initial input for the hash or None. | |
| digestmod: A hash name suitable for hashlib.new(). *OR* | |
| A hashlib constructor returning a new hash object. *OR* | |
| A module supporting PEP 247. | |
| Required as of 3.8, despite its position after the optional | |
| msg argument. Passing it as a keyword argument is | |
| recommended, though not required for legacy API reasons. | |
| """ | |
| if not isinstance(key, (bytes, bytearray)): | |
| raise TypeError(f"key: expected bytes or bytearray, " | |
| f"but got {type(key).__name__!r}") | |
| if not digestmod: | |
| raise TypeError("Missing required argument 'digestmod'.") | |
| self.__init(key, msg, digestmod) | |
| def __init(self, key, msg, digestmod): | |
| if _hashopenssl and isinstance(digestmod, (str, _functype)): | |
| try: | |
| self._init_openssl_hmac(key, msg, digestmod) | |
| return | |
| except _hashopenssl.UnsupportedDigestmodError: # pragma: no cover | |
| pass | |
| if _hmac and isinstance(digestmod, str): | |
| try: | |
| self._init_builtin_hmac(key, msg, digestmod) | |
| return | |
| except _hmac.UnknownHashError: # pragma: no cover | |
| pass | |
| self._init_old(key, msg, digestmod) | |
| def _init_openssl_hmac(self, key, msg, digestmod): | |
| self._hmac = _hashopenssl.hmac_new(key, msg, digestmod=digestmod) | |
| self._inner = self._outer = None # because the slots are defined | |
| self.digest_size = self._hmac.digest_size | |
| self.block_size = self._hmac.block_size | |
| _init_hmac = _init_openssl_hmac # for backward compatibility (if any) | |
| def _init_builtin_hmac(self, key, msg, digestmod): | |
| self._hmac = _hmac.new(key, msg, digestmod=digestmod) | |
| self._inner = self._outer = None # because the slots are defined | |
| self.digest_size = self._hmac.digest_size | |
| self.block_size = self._hmac.block_size | |
| def _init_old(self, key, msg, digestmod): | |
| import warnings | |
| digest_cons = _get_digest_constructor(digestmod) | |
| if _is_shake_constructor(digest_cons): | |
| raise ValueError(f"unsupported hash algorithm {digestmod}") | |
| self._hmac = None | |
| self._outer = digest_cons() | |
| self._inner = digest_cons() | |
| self.digest_size = self._inner.digest_size | |
| if hasattr(self._inner, 'block_size'): | |
| blocksize = self._inner.block_size | |
| if blocksize < 16: | |
| warnings.warn(f"block_size of {blocksize} seems too small; " | |
| f"using our default of {self.blocksize}.", | |
| RuntimeWarning, 2) | |
| blocksize = self.blocksize # pragma: no cover | |
| else: | |
| warnings.warn("No block_size attribute on given digest object; " | |
| f"Assuming {self.blocksize}.", | |
| RuntimeWarning, 2) | |
| blocksize = self.blocksize # pragma: no cover | |
| if len(key) > blocksize: | |
| key = digest_cons(key).digest() | |
| self.block_size = blocksize | |
| key = key.ljust(blocksize, b'\0') | |
| self._outer.update(key.translate(trans_5C)) | |
| self._inner.update(key.translate(trans_36)) | |
| if msg is not None: | |
| self.update(msg) | |
| @property | |
| def name(self): | |
| if self._hmac: | |
| return self._hmac.name | |
| else: | |
| return f"hmac-{self._inner.name}" | |
| def update(self, msg): | |
| """Feed data from msg into this hashing object.""" | |
| inst = self._hmac or self._inner | |
| inst.update(msg) | |
| def copy(self): | |
| """Return a separate copy of this hashing object. | |
| An update to this copy won't affect the original object. | |
| """ | |
| # Call __new__ directly to avoid the expensive __init__. | |
| other = self.__class__.__new__(self.__class__) | |
| other.digest_size = self.digest_size | |
| other.block_size = self.block_size | |
| if self._hmac: | |
| other._hmac = self._hmac.copy() | |
| other._inner = other._outer = None | |
| else: | |
| other._hmac = None | |
| other._inner = self._inner.copy() | |
| other._outer = self._outer.copy() | |
| return other | |
| def _current(self): | |
| """Return a hash object for the current state. | |
| To be used only internally with digest() and hexdigest(). | |
| """ | |
| if self._hmac: | |
| return self._hmac | |
| else: | |
| h = self._outer.copy() | |
| h.update(self._inner.digest()) | |
| return h | |
| def digest(self): | |
| """Return the hash value of this hashing object. | |
| This returns the hmac value as bytes. The object is | |
| not altered in any way by this function; you can continue | |
| updating the object after calling this function. | |
| """ | |
| h = self._current() | |
| return h.digest() | |
| def hexdigest(self): | |
| """Like digest(), but returns a string of hexadecimal digits instead. | |
| """ | |
| h = self._current() | |
| return h.hexdigest() | |
| def new(key, msg=None, digestmod=''): | |
| """Create a new hashing object and return it. | |
| key: bytes or buffer, The starting key for the hash. | |
| msg: bytes or buffer, Initial input for the hash, or None. | |
| digestmod: A hash name suitable for hashlib.new(). *OR* | |
| A hashlib constructor returning a new hash object. *OR* | |
| A module supporting PEP 247. | |
| Required as of 3.8, despite its position after the optional | |
| msg argument. Passing it as a keyword argument is | |
| recommended, though not required for legacy API reasons. | |
| You can now feed arbitrary bytes into the object using its update() | |
| method, and can ask for the hash value at any time by calling its digest() | |
| or hexdigest() methods. | |
| """ | |
| return HMAC(key, msg, digestmod) | |
| def digest(key, msg, digest): | |
| """Fast inline implementation of HMAC. | |
| key: bytes or buffer, The key for the keyed hash object. | |
| msg: bytes or buffer, Input message. | |
| digest: A hash name suitable for hashlib.new() for best performance. *OR* | |
| A hashlib constructor returning a new hash object. *OR* | |
| A module supporting PEP 247. | |
| """ | |
| if _hashopenssl and isinstance(digest, (str, _functype)): | |
| try: | |
| return _hashopenssl.hmac_digest(key, msg, digest) | |
| except OverflowError: | |
| # OpenSSL's HMAC limits the size of the key to INT_MAX. | |
| # Instead of falling back to HACL* implementation which | |
| # may still not be supported due to a too large key, we | |
| # directly switch to the pure Python fallback instead | |
| # even if we could have used streaming HMAC for small keys | |
| # but large messages. | |
| return _compute_digest_fallback(key, msg, digest) | |
| except _hashopenssl.UnsupportedDigestmodError: | |
| pass | |
| if _hmac and isinstance(digest, str): | |
| try: | |
| return _hmac.compute_digest(key, msg, digest) | |
| except (OverflowError, _hmac.UnknownHashError): | |
| # HACL* HMAC limits the size of the key to UINT32_MAX | |
| # so we fallback to the pure Python implementation even | |
| # if streaming HMAC may have been used for small keys | |
| # and large messages. | |
| pass | |
| return _compute_digest_fallback(key, msg, digest) | |
| def _compute_digest_fallback(key, msg, digest): | |
| if not isinstance(key, (bytes, bytearray)): | |
| raise TypeError(f"key: expected bytes or bytearray, " | |
| f"but got {type(key).__name__!r}") | |
| digest_cons = _get_digest_constructor(digest) | |
| if _is_shake_constructor(digest_cons): | |
| raise ValueError(f"unsupported hash algorithm {digest}") | |
| inner = digest_cons() | |
| outer = digest_cons() | |
| blocksize = getattr(inner, 'block_size', 64) | |
| if len(key) > blocksize: | |
| key = digest_cons(key).digest() | |
| key = key.ljust(blocksize, b'\0') | |
| inner.update(key.translate(trans_36)) | |
| outer.update(key.translate(trans_5C)) | |
| inner.update(msg) | |
| outer.update(inner.digest()) | |
| return outer.digest() |