codekingpro/portable-devtools

1"""HMAC (Keyed-Hashing for Message Authentication) module.2 3Implements the HMAC algorithm as described by RFC 2104.4"""5 6try:7    import _hashlib as _hashopenssl8except ImportError:9    _hashopenssl = None10    _functype = None11    from _operator import _compare_digest as compare_digest12else:13    compare_digest = _hashopenssl.compare_digest14    _functype = type(_hashopenssl.openssl_sha256)  # builtin type15 16try:17    import _hmac18except ImportError:19    _hmac = None20 21trans_5C = bytes((x ^ 0x5C) for x in range(256))22trans_36 = bytes((x ^ 0x36) for x in range(256))23 24# The size of the digests returned by HMAC depends on the underlying25# hashing module used.  Use digest_size from the instance of HMAC instead.26digest_size = None27 28 29def _get_digest_constructor(digest_like):30    if callable(digest_like):31        return digest_like32    if isinstance(digest_like, str):33        def digest_wrapper(d=b''):34            import hashlib35            return hashlib.new(digest_like, d)36    else:37        def digest_wrapper(d=b''):38            return digest_like.new(d)39    return digest_wrapper40 41 42class HMAC:43    """RFC 2104 HMAC class.  Also complies with RFC 4231.44 45    This supports the API for Cryptographic Hash Functions (PEP 247).46    """47 48    # Note: self.blocksize is the default blocksize; self.block_size49    # is effective block size as well as the public API attribute.50    blocksize = 64  # 512-bit HMAC; can be changed in subclasses.51 52    __slots__ = (53        "_hmac", "_inner", "_outer", "block_size", "digest_size"54    )55 56    def __init__(self, key, msg=None, digestmod=''):57        """Create a new HMAC object.58 59        key: bytes or buffer, key for the keyed hash object.60        msg: bytes or buffer, Initial input for the hash or None.61        digestmod: A hash name suitable for hashlib.new(). *OR*62                   A hashlib constructor returning a new hash object. *OR*63                   A module supporting PEP 247.64 65                   Required as of 3.8, despite its position after the optional66                   msg argument.  Passing it as a keyword argument is67                   recommended, though not required for legacy API reasons.68        """69 70        if not isinstance(key, (bytes, bytearray)):71            raise TypeError(f"key: expected bytes or bytearray, "72                            f"but got {type(key).__name__!r}")73 74        if not digestmod:75            raise TypeError("Missing required argument 'digestmod'.")76 77        self.__init(key, msg, digestmod)78 79    def __init(self, key, msg, digestmod):80        if _hashopenssl and isinstance(digestmod, (str, _functype)):81            try:82                self._init_openssl_hmac(key, msg, digestmod)83                return84            except _hashopenssl.UnsupportedDigestmodError:  # pragma: no cover85                pass86        if _hmac and isinstance(digestmod, str):87            try:88                self._init_builtin_hmac(key, msg, digestmod)89                return90            except _hmac.UnknownHashError:  # pragma: no cover91                pass92        self._init_old(key, msg, digestmod)93 94    def _init_openssl_hmac(self, key, msg, digestmod):95        self._hmac = _hashopenssl.hmac_new(key, msg, digestmod=digestmod)96        self._inner = self._outer = None  # because the slots are defined97        self.digest_size = self._hmac.digest_size98        self.block_size = self._hmac.block_size99 100    _init_hmac = _init_openssl_hmac  # for backward compatibility (if any)101 102    def _init_builtin_hmac(self, key, msg, digestmod):103        self._hmac = _hmac.new(key, msg, digestmod=digestmod)104        self._inner = self._outer = None  # because the slots are defined105        self.digest_size = self._hmac.digest_size106        self.block_size = self._hmac.block_size107 108    def _init_old(self, key, msg, digestmod):109        import warnings110 111        digest_cons = _get_digest_constructor(digestmod)112 113        self._hmac = None114        self._outer = digest_cons()115        self._inner = digest_cons()116        self.digest_size = self._inner.digest_size117 118        if hasattr(self._inner, 'block_size'):119            blocksize = self._inner.block_size120            if blocksize < 16:121                warnings.warn(f"block_size of {blocksize} seems too small; "122                              f"using our default of {self.blocksize}.",123                              RuntimeWarning, 2)124                blocksize = self.blocksize  # pragma: no cover125        else:126            warnings.warn("No block_size attribute on given digest object; "127                          f"Assuming {self.blocksize}.",128                          RuntimeWarning, 2)129            blocksize = self.blocksize  # pragma: no cover130 131        if len(key) > blocksize:132            key = digest_cons(key).digest()133 134        self.block_size = blocksize135 136        key = key.ljust(blocksize, b'\0')137        self._outer.update(key.translate(trans_5C))138        self._inner.update(key.translate(trans_36))139        if msg is not None:140            self.update(msg)141 142    @property143    def name(self):144        if self._hmac:145            return self._hmac.name146        else:147            return f"hmac-{self._inner.name}"148 149    def update(self, msg):150        """Feed data from msg into this hashing object."""151        inst = self._hmac or self._inner152        inst.update(msg)153 154    def copy(self):155        """Return a separate copy of this hashing object.156 157        An update to this copy won't affect the original object.158        """159        # Call __new__ directly to avoid the expensive __init__.160        other = self.__class__.__new__(self.__class__)161        other.digest_size = self.digest_size162        other.block_size = self.block_size163        if self._hmac:164            other._hmac = self._hmac.copy()165            other._inner = other._outer = None166        else:167            other._hmac = None168            other._inner = self._inner.copy()169            other._outer = self._outer.copy()170        return other171 172    def _current(self):173        """Return a hash object for the current state.174 175        To be used only internally with digest() and hexdigest().176        """177        if self._hmac:178            return self._hmac179        else:180            h = self._outer.copy()181            h.update(self._inner.digest())182            return h183 184    def digest(self):185        """Return the hash value of this hashing object.186 187        This returns the hmac value as bytes.  The object is188        not altered in any way by this function; you can continue189        updating the object after calling this function.190        """191        h = self._current()192        return h.digest()193 194    def hexdigest(self):195        """Like digest(), but returns a string of hexadecimal digits instead.196        """197        h = self._current()198        return h.hexdigest()199 200 201def new(key, msg=None, digestmod=''):202    """Create a new hashing object and return it.203 204    key: bytes or buffer, The starting key for the hash.205    msg: bytes or buffer, Initial input for the hash, or None.206    digestmod: A hash name suitable for hashlib.new(). *OR*207               A hashlib constructor returning a new hash object. *OR*208               A module supporting PEP 247.209 210               Required as of 3.8, despite its position after the optional211               msg argument.  Passing it as a keyword argument is212               recommended, though not required for legacy API reasons.213 214    You can now feed arbitrary bytes into the object using its update()215    method, and can ask for the hash value at any time by calling its digest()216    or hexdigest() methods.217    """218    return HMAC(key, msg, digestmod)219 220 221def digest(key, msg, digest):222    """Fast inline implementation of HMAC.223 224    key: bytes or buffer, The key for the keyed hash object.225    msg: bytes or buffer, Input message.226    digest: A hash name suitable for hashlib.new() for best performance. *OR*227            A hashlib constructor returning a new hash object. *OR*228            A module supporting PEP 247.229    """230    if _hashopenssl and isinstance(digest, (str, _functype)):231        try:232            return _hashopenssl.hmac_digest(key, msg, digest)233        except OverflowError:234            # OpenSSL's HMAC limits the size of the key to INT_MAX.235            # Instead of falling back to HACL* implementation which236            # may still not be supported due to a too large key, we237            # directly switch to the pure Python fallback instead238            # even if we could have used streaming HMAC for small keys239            # but large messages.240            return _compute_digest_fallback(key, msg, digest)241        except _hashopenssl.UnsupportedDigestmodError:242            pass243 244    if _hmac and isinstance(digest, str):245        try:246            return _hmac.compute_digest(key, msg, digest)247        except (OverflowError, _hmac.UnknownHashError):248            # HACL* HMAC limits the size of the key to UINT32_MAX249            # so we fallback to the pure Python implementation even250            # if streaming HMAC may have been used for small keys251            # and large messages.252            pass253 254    return _compute_digest_fallback(key, msg, digest)255 256 257def _compute_digest_fallback(key, msg, digest):258    digest_cons = _get_digest_constructor(digest)259    inner = digest_cons()260    outer = digest_cons()261    blocksize = getattr(inner, 'block_size', 64)262    if len(key) > blocksize:263        key = digest_cons(key).digest()264    key = key.ljust(blocksize, b'\0')265    inner.update(key.translate(trans_36))266    outer.update(key.translate(trans_5C))267    inner.update(msg)268    outer.update(inner.digest())269    return outer.digest()270