| """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 _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) |
| |
| 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 |
| 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): |
| digest_cons = _get_digest_constructor(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() |
