gh-136547: fix hashlib_helper for blocking and requesting digests (#136762)

- Fix `hashlib_helper.block_algorithm` where the dummy functions were incorrectly defined.
- Rename `hashlib_helper.HashAPI` to `hashlib_helper.HashInfo` and add more helper methods.
- Simplify `hashlib_helper.requires_*()` functions.
- Rewrite some private helpers in `hashlib_helper`.
- Remove `find_{builtin,openssl}_hashdigest_constructor()` as they are no more needed and were
  not meant to be public in the first place.
- Fix some tests in `test_hashlib` when FIPS mode is on.

Lib/hashlib.py

@@ -136,12 +136,22 @@ def __get_openssl_constructor(name):
         # Prefer our builtin blake2 implementation.
         return __get_builtin_constructor(name)
     try:
-        # MD5, SHA1, and SHA2 are in all supported OpenSSL versions
-        # SHA3/shake are available in OpenSSL 1.1.1+
+        # Fetch the OpenSSL hash function if it exists,
+        # independently of the context security policy.
         f = getattr(_hashlib, 'openssl_' + name)
-        # Allow the C module to raise ValueError.  The function will be
-        # defined but the hash not actually available.  Don't fall back to
-        # builtin if the current security policy blocks a digest, bpo#40695.
+        # Check if the context security policy blocks the digest or not
+        # by allowing the C module to raise a ValueError. The function
+        # will be defined but the hash will not be available at runtime.
+        #
+        # We use "usedforsecurity=False" to prevent falling back to the
+        # built-in function in case the security policy does not allow it.
+        #
+        # Note that this only affects the explicit named constructors,
+        # and not the algorithms exposed through hashlib.new() which
+        # can still be resolved to a built-in function even if the
+        # current security policy does not allow it.
+        #
+        # See https://github.com/python/cpython/issues/84872.
         f(usedforsecurity=False)
         # Use the C function directly (very fast)
         return f

Lib/test/support/hashlib_helper.py

@@ -1,91 +1,214 @@
 import contextlib
+import enum
 import functools
-import hashlib
 import importlib
 import inspect
 import unittest
 import unittest.mock
-from collections import namedtuple
-from test.support.import_helper import import_module
+from test.support import import_helper
 from types import MappingProxyType
 
-try:
-    import _hashlib
-except ImportError:
-    _hashlib = None
 
-try:
-    import _hmac
-except ImportError:
-    _hmac = None
+def try_import_module(module_name):
+    """Try to import a module and return None on failure."""
+    try:
+        return importlib.import_module(module_name)
+    except ImportError:
+        return None
 
 
-CANONICAL_DIGEST_NAMES = frozenset((
-    'md5', 'sha1',
-    'sha224', 'sha256', 'sha384', 'sha512',
-    'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512',
-    'shake_128', 'shake_256',
-    'blake2s', 'blake2b',
+class HID(enum.StrEnum):
+    """Enumeration containing the canonical digest names.
+
+    Those names should only be used by hashlib.new() or hmac.new().
+    Their support by _hashlib.new() is not necessarily guaranteed.
+    """
+
+    md5 = enum.auto()
+    sha1 = enum.auto()
+
+    sha224 = enum.auto()
+    sha256 = enum.auto()
+    sha384 = enum.auto()
+    sha512 = enum.auto()
+
+    sha3_224 = enum.auto()
+    sha3_256 = enum.auto()
+    sha3_384 = enum.auto()
+    sha3_512 = enum.auto()
+
+    shake_128 = enum.auto()
+    shake_256 = enum.auto()
+
+    blake2s = enum.auto()
+    blake2b = enum.auto()
+
+    def __repr__(self):
+        return str(self)
+
+    @property
+    def is_xof(self):
+        """Indicate whether the hash is an extendable-output hash function."""
+        return self.startswith("shake_")
+
+    @property
+    def is_keyed(self):
+        """Indicate whether the hash is a keyed hash function."""
+        return self.startswith("blake2")
+
+
+CANONICAL_DIGEST_NAMES = frozenset(map(str, HID.__members__))
+NON_HMAC_DIGEST_NAMES = frozenset((
+    HID.shake_128, HID.shake_256,
+    HID.blake2s, HID.blake2b,
 ))
 
-NON_HMAC_DIGEST_NAMES = frozenset({
-    'shake_128', 'shake_256',
-    'blake2s', 'blake2b',
-})
 
+class HashInfo:
+    """Dataclass storing explicit hash constructor names.
 
-class HashAPI(namedtuple("HashAPI", "builtin openssl hashlib")):
+    - *builtin* is the fully-qualified name for the explicit HACL*
+      hash constructor function, e.g., "_md5.md5".
 
-    def fullname(self, typ):
-        match typ:
+    - *openssl* is the name of the "_hashlib" module method for the explicit
+      OpenSSL hash constructor function, e.g., "openssl_md5".
+
+    - *hashlib* is the name of the "hashlib" module method for the explicit
+      hash constructor function, e.g., "md5".
+    """
+
+    def __init__(self, builtin, openssl=None, hashlib=None):
+        assert isinstance(builtin, str), builtin
+        assert len(builtin.split(".")) == 2, builtin
+
+        self.builtin = builtin
+        self.builtin_module_name, self.builtin_method_name = (
+            self.builtin.split(".", maxsplit=1)
+        )
+
+        assert openssl is None or openssl.startswith("openssl_")
+        self.openssl = self.openssl_method_name = openssl
+        self.openssl_module_name = "_hashlib" if openssl else None
+
+        assert hashlib is None or isinstance(hashlib, str)
+        self.hashlib = self.hashlib_method_name = hashlib
+        self.hashlib_module_name = "hashlib" if hashlib else None
+
+    def module_name(self, implementation):
+        match implementation:
             case "builtin":
-                return self.builtin
+                return self.builtin_module_name
             case "openssl":
-                return f"_hashlib.{self.openssl}" if self.openssl else None
+                return self.openssl_module_name
             case "hashlib":
-                return f"hashlib.{self.hashlib}" if self.hashlib else None
-            case _:
-                raise AssertionError(f"unknown type: {typ}")
+                return self.hashlib_module_name
+        raise AssertionError(f"invalid implementation {implementation}")
+
+    def method_name(self, implementation):
+        match implementation:
+            case "builtin":
+                return self.builtin_method_name
+            case "openssl":
+                return self.openssl_method_name
+            case "hashlib":
+                return self.hashlib_method_name
+        raise AssertionError(f"invalid implementation {implementation}")
+
+    def fullname(self, implementation):
+        """Get the fully qualified name of a given implementation.
+
+        This returns a string of the form "MODULE_NAME.METHOD_NAME" or None
+        if the hash function does not have a corresponding implementation.
+
+        *implementation* must be "builtin", "openssl" or "hashlib".
+        """
+        module_name = self.module_name(implementation)
+        method_name = self.method_name(implementation)
+        if module_name is None or method_name is None:
+            return None
+        return f"{module_name}.{method_name}"
 
 
 # Mapping from a "canonical" name to a pair (HACL*, _hashlib.*, hashlib.*)
 # constructors. If the constructor name is None, then this means that the
 # algorithm can only be used by the "agile" new() interfaces.
-_EXPLICIT_CONSTRUCTORS = MappingProxyType({
-    "md5": HashAPI("_md5.md5", "openssl_md5", "md5"),
-    "sha1": HashAPI("_sha1.sha1", "openssl_sha1", "sha1"),
-    "sha224": HashAPI("_sha2.sha224", "openssl_sha224", "sha224"),
-    "sha256": HashAPI("_sha2.sha256", "openssl_sha256", "sha256"),
-    "sha384": HashAPI("_sha2.sha384", "openssl_sha384", "sha384"),
-    "sha512": HashAPI("_sha2.sha512", "openssl_sha512", "sha512"),
-    "sha3_224": HashAPI("_sha3.sha3_224", "openssl_sha3_224", "sha3_224"),
-    "sha3_256": HashAPI("_sha3.sha3_256", "openssl_sha3_256", "sha3_256"),
-    "sha3_384": HashAPI("_sha3.sha3_384", "openssl_sha3_384", "sha3_384"),
-    "sha3_512": HashAPI("_sha3.sha3_512", "openssl_sha3_512", "sha3_512"),
-    "shake_128": HashAPI("_sha3.shake_128", "openssl_shake_128", "shake_128"),
-    "shake_256": HashAPI("_sha3.shake_256", "openssl_shake_256", "shake_256"),
-    "blake2s": HashAPI("_blake2.blake2s", None, "blake2s"),
-    "blake2b": HashAPI("_blake2.blake2b", None, "blake2b"),
+_EXPLICIT_CONSTRUCTORS = MappingProxyType({  # fmt: skip
+    HID.md5: HashInfo("_md5.md5", "openssl_md5", "md5"),
+    HID.sha1: HashInfo("_sha1.sha1", "openssl_sha1", "sha1"),
+    HID.sha224: HashInfo("_sha2.sha224", "openssl_sha224", "sha224"),
+    HID.sha256: HashInfo("_sha2.sha256", "openssl_sha256", "sha256"),
+    HID.sha384: HashInfo("_sha2.sha384", "openssl_sha384", "sha384"),
+    HID.sha512: HashInfo("_sha2.sha512", "openssl_sha512", "sha512"),
+    HID.sha3_224: HashInfo(
+        "_sha3.sha3_224", "openssl_sha3_224", "sha3_224"
+    ),
+    HID.sha3_256: HashInfo(
+        "_sha3.sha3_256", "openssl_sha3_256", "sha3_256"
+    ),
+    HID.sha3_384: HashInfo(
+        "_sha3.sha3_384", "openssl_sha3_384", "sha3_384"
+    ),
+    HID.sha3_512: HashInfo(
+        "_sha3.sha3_512", "openssl_sha3_512", "sha3_512"
+    ),
+    HID.shake_128: HashInfo(
+        "_sha3.shake_128", "openssl_shake_128", "shake_128"
+    ),
+    HID.shake_256: HashInfo(
+        "_sha3.shake_256", "openssl_shake_256", "shake_256"
+    ),
+    HID.blake2s: HashInfo("_blake2.blake2s", None, "blake2s"),
+    HID.blake2b: HashInfo("_blake2.blake2b", None, "blake2b"),
 })
 assert _EXPLICIT_CONSTRUCTORS.keys() == CANONICAL_DIGEST_NAMES
+get_hash_info = _EXPLICIT_CONSTRUCTORS.__getitem__
 
+# Mapping from canonical hash names to their explicit HACL* HMAC constructor.
+# There is currently no OpenSSL one-shot named function and there will likely
+# be none in the future.
 _EXPLICIT_HMAC_CONSTRUCTORS = {
-    name: f'_hmac.compute_{name}' for name in (
-        'md5', 'sha1',
-        'sha224', 'sha256', 'sha384', 'sha512',
-        'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512',
-    )
+    HID(name): f"_hmac.compute_{name}"
+    for name in CANONICAL_DIGEST_NAMES
 }
-_EXPLICIT_HMAC_CONSTRUCTORS['shake_128'] = None
-_EXPLICIT_HMAC_CONSTRUCTORS['shake_256'] = None
+# Neither HACL* nor OpenSSL supports HMAC over XOFs.
+_EXPLICIT_HMAC_CONSTRUCTORS[HID.shake_128] = None
+_EXPLICIT_HMAC_CONSTRUCTORS[HID.shake_256] = None
 # Strictly speaking, HMAC-BLAKE is meaningless as BLAKE2 is already a
 # keyed hash function. However, as it's exposed by HACL*, we test it.
-_EXPLICIT_HMAC_CONSTRUCTORS['blake2s'] = '_hmac.compute_blake2s_32'
-_EXPLICIT_HMAC_CONSTRUCTORS['blake2b'] = '_hmac.compute_blake2b_32'
+_EXPLICIT_HMAC_CONSTRUCTORS[HID.blake2s] = '_hmac.compute_blake2s_32'
+_EXPLICIT_HMAC_CONSTRUCTORS[HID.blake2b] = '_hmac.compute_blake2b_32'
 _EXPLICIT_HMAC_CONSTRUCTORS = MappingProxyType(_EXPLICIT_HMAC_CONSTRUCTORS)
 assert _EXPLICIT_HMAC_CONSTRUCTORS.keys() == CANONICAL_DIGEST_NAMES
 
 
+def _decorate_func_or_class(decorator_func, func_or_class):
+    if not isinstance(func_or_class, type):
+        return decorator_func(func_or_class)
+
+    decorated_class = func_or_class
+    setUpClass = decorated_class.__dict__.get('setUpClass')
+    if setUpClass is None:
+        def setUpClass(cls):
+            super(decorated_class, cls).setUpClass()
+        setUpClass.__qualname__ = decorated_class.__qualname__ + '.setUpClass'
+        setUpClass.__module__ = decorated_class.__module__
+    else:
+        setUpClass = setUpClass.__func__
+    setUpClass = classmethod(decorator_func(setUpClass))
+    decorated_class.setUpClass = setUpClass
+    return decorated_class
+
+
+def _chain_decorators(decorators):
+    """Obtain a decorator by chaining multiple decorators.
+
+    The decorators are applied in the order they are given.
+    """
+    def decorator_func(func):
+        return functools.reduce(lambda w, deco: deco(w), decorators, func)
+    return functools.partial(_decorate_func_or_class, decorator_func)
+
+
 def _ensure_wrapper_signature(wrapper, wrapped):
     """Ensure that a wrapper has the same signature as the wrapped function.
 
@@ -108,49 +231,129 @@ def _ensure_wrapper_signature(wrapper, wrapped):
 
 
 def requires_hashlib():
+    _hashlib = try_import_module("_hashlib")
     return unittest.skipIf(_hashlib is None, "requires _hashlib")
 
 
 def requires_builtin_hmac():
+    _hmac = try_import_module("_hmac")
     return unittest.skipIf(_hmac is None, "requires _hmac")
 
 
-def _missing_hash(digestname, implementation=None, *, exc=None):
-    parts = ["missing", implementation, f"hash algorithm: {digestname!r}"]
-    msg = " ".join(filter(None, parts))
-    raise unittest.SkipTest(msg) from exc
+class SkipNoHash(unittest.SkipTest):
+    """A SkipTest exception raised when a hash is not available."""
+
+    def __init__(self, digestname, implementation=None, interface=None):
+        parts = ["missing", implementation, f"hash algorithm {digestname!r}"]
+        if interface is not None:
+            parts.append(f"for {interface}")
+        super().__init__(" ".join(filter(None, parts)))
 
 
-def _openssl_availabillity(digestname, *, usedforsecurity):
+def _hashlib_new(digestname, openssl, /, **kwargs):
+    """Check availability of [hashlib|_hashlib].new(digestname, **kwargs).
+
+    If *openssl* is True, module is "_hashlib" (C extension module),
+    otherwise it is "hashlib" (pure Python interface).
+
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
+    """
+    assert isinstance(digestname, str), digestname
+    # Re-import 'hashlib' in case it was mocked, but propagate
+    # exceptions as it should be unconditionally available.
+    hashlib = importlib.import_module("hashlib")
+    # re-import '_hashlib' in case it was mocked
+    _hashlib = try_import_module("_hashlib")
+    module = _hashlib if openssl and _hashlib is not None else hashlib
+    try:
+        module.new(digestname, **kwargs)
+    except ValueError as exc:
+        interface = f"{module.__name__}.new"
+        raise SkipNoHash(digestname, interface=interface) from exc
+    return functools.partial(module.new, digestname)
+
+
+def _builtin_hash(module_name, digestname, /, **kwargs):
+    """Check availability of <module_name>.<digestname>(**kwargs).
+
+    - The *module_name* is the C extension module name based on HACL*.
+    - The *digestname* is one of its member, e.g., 'md5'.
+
+    The constructor function is returned, or SkipTest is raised if none exists.
+    """
+    assert isinstance(module_name, str), module_name
+    assert isinstance(digestname, str), digestname
+    fullname = f'{module_name}.{digestname}'
+    try:
+        builtin_module = importlib.import_module(module_name)
+    except ImportError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    try:
+        constructor = getattr(builtin_module, digestname)
+    except AttributeError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    try:
+        constructor(**kwargs)
+    except ValueError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    return constructor
+
+
+def _openssl_new(digestname, /, **kwargs):
+    """Check availability of _hashlib.new(digestname, **kwargs).
+
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
+    """
     assert isinstance(digestname, str), digestname
     try:
-        _hashlib.new(digestname, usedforsecurity=usedforsecurity)
-    except AttributeError:
-        assert _hashlib is None
-        _missing_hash(digestname, "OpenSSL")
+        # re-import '_hashlib' in case it was mocked
+        _hashlib = importlib.import_module("_hashlib")
+    except ImportError as exc:
+        raise SkipNoHash(digestname, "openssl") from exc
+    try:
+        _hashlib.new(digestname, **kwargs)
     except ValueError as exc:
-        _missing_hash(digestname, "OpenSSL", exc=exc)
+        raise SkipNoHash(digestname, interface="_hashlib.new") from exc
+    return functools.partial(_hashlib.new, digestname)
 
 
-def _decorate_func_or_class(func_or_class, decorator_func):
-    if not isinstance(func_or_class, type):
-        return decorator_func(func_or_class)
+def _openssl_hash(digestname, /, **kwargs):
+    """Check availability of _hashlib.openssl_<digestname>(**kwargs).
 
-    decorated_class = func_or_class
-    setUpClass = decorated_class.__dict__.get('setUpClass')
-    if setUpClass is None:
-        def setUpClass(cls):
-            super(decorated_class, cls).setUpClass()
-        setUpClass.__qualname__ = decorated_class.__qualname__ + '.setUpClass'
-        setUpClass.__module__ = decorated_class.__module__
-    else:
-        setUpClass = setUpClass.__func__
-    setUpClass = classmethod(decorator_func(setUpClass))
-    decorated_class.setUpClass = setUpClass
-    return decorated_class
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
+    """
+    assert isinstance(digestname, str), digestname
+    fullname = f"_hashlib.openssl_{digestname}"
+    try:
+        # re-import '_hashlib' in case it was mocked
+        _hashlib = importlib.import_module("_hashlib")
+    except ImportError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
+    try:
+        constructor = getattr(_hashlib, f"openssl_{digestname}", None)
+    except AttributeError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
+    try:
+        constructor(**kwargs)
+    except ValueError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
+    return constructor
 
 
-def requires_hashdigest(digestname, openssl=None, usedforsecurity=True):
+def _make_requires_hashdigest_decorator(test, /, *test_args, **test_kwargs):
+    def decorator_func(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kwargs):
+            test(*test_args, **test_kwargs)
+            return func(*args, **kwargs)
+        return wrapper
+    return functools.partial(_decorate_func_or_class, decorator_func)
+
+
+def requires_hashdigest(digestname, openssl=None, *, usedforsecurity=True):
     """Decorator raising SkipTest if a hashing algorithm is not available.
 
     The hashing algorithm may be missing, blocked by a strict crypto policy,
@@ -167,27 +370,9 @@ def requires_hashdigest(digestname, openssl=None, usedforsecurity=True):
     ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for FIPS
     ValueError: unsupported hash type md4
     """
-    assert isinstance(digestname, str), digestname
-    if openssl and _hashlib is not None:
-        def test_availability():
-            _hashlib.new(digestname, usedforsecurity=usedforsecurity)
-    else:
-        def test_availability():
-            hashlib.new(digestname, usedforsecurity=usedforsecurity)
-
-    def decorator_func(func):
-        @functools.wraps(func)
-        def wrapper(*args, **kwargs):
-            try:
-                test_availability()
-            except ValueError as exc:
-                _missing_hash(digestname, exc=exc)
-            return func(*args, **kwargs)
-        return wrapper
-
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
+    return _make_requires_hashdigest_decorator(
+        _hashlib_new, digestname, openssl, usedforsecurity=usedforsecurity
+    )
 
 
 def requires_openssl_hashdigest(digestname, *, usedforsecurity=True):
@@ -195,27 +380,9 @@ def requires_openssl_hashdigest(digestname, *, usedforsecurity=True):
 
     The hashing algorithm may be missing or blocked by a strict crypto policy.
     """
-    assert isinstance(digestname, str), digestname
-    def decorator_func(func):
-        @requires_hashlib()  # avoid checking at each call
-        @functools.wraps(func)
-        def wrapper(*args, **kwargs):
-            _openssl_availabillity(digestname, usedforsecurity=usedforsecurity)
-            return func(*args, **kwargs)
-        return wrapper
-
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
-
-
-def find_openssl_hashdigest_constructor(digestname, *, usedforsecurity=True):
-    """Find the OpenSSL hash function constructor by its name."""
-    assert isinstance(digestname, str), digestname
-    _openssl_availabillity(digestname, usedforsecurity=usedforsecurity)
-    # This returns a function of the form _hashlib.openssl_<name> and
-    # not a lambda function as it is rejected by _hashlib.hmac_new().
-    return getattr(_hashlib, f"openssl_{digestname}")
+    return _make_requires_hashdigest_decorator(
+        _openssl_new, digestname, usedforsecurity=usedforsecurity
+    )
 
 
 def requires_builtin_hashdigest(
@@ -226,40 +393,22 @@ def requires_builtin_hashdigest(
     - The *module_name* is the C extension module name based on HACL*.
     - The *digestname* is one of its member, e.g., 'md5'.
     """
-    assert isinstance(digestname, str), digestname
-    def decorator_func(func):
-        @functools.wraps(func)
-        def wrapper(*args, **kwargs):
-            module = import_module(module_name)
-            try:
-                getattr(module, digestname)
-            except AttributeError:
-                fullname = f'{module_name}.{digestname}'
-                _missing_hash(fullname, implementation="HACL")
-            return func(*args, **kwargs)
-        return wrapper
-
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
+    return _make_requires_hashdigest_decorator(
+        _builtin_hash, module_name, digestname, usedforsecurity=usedforsecurity
+    )
 
 
-def find_builtin_hashdigest_constructor(
-    module_name, digestname, *, usedforsecurity=True
-):
-    """Find the HACL* hash function constructor.
-
-    - The *module_name* is the C extension module name based on HACL*.
-    - The *digestname* is one of its member, e.g., 'md5'.
-    """
-    assert isinstance(digestname, str), digestname
-    module = import_module(module_name)
-    try:
-        constructor = getattr(module, digestname)
-        constructor(b'', usedforsecurity=usedforsecurity)
-    except (AttributeError, TypeError, ValueError):
-        _missing_hash(f'{module_name}.{digestname}', implementation="HACL")
-    return constructor
+def requires_builtin_hashes(*ignored, usedforsecurity=True):
+    """Decorator raising SkipTest if one HACL* hashing algorithm is missing."""
+    return _chain_decorators((
+        requires_builtin_hashdigest(
+            api.builtin_module_name,
+            api.builtin_method_name,
+            usedforsecurity=usedforsecurity,
+        )
+        for name, api in _EXPLICIT_CONSTRUCTORS.items()
+        if name not in ignored
+    ))
 
 
 class HashFunctionsTrait:
@@ -281,7 +430,9 @@ class HashFunctionsTrait:
         'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512',
     ]
 
-    # Default 'usedforsecurity' to use when looking up a hash function.
+    # Default 'usedforsecurity' to use when checking a hash function.
+    # When the trait properties are callables (e.g., _md5.md5) and
+    # not strings, they must be called with the same 'usedforsecurity'.
     usedforsecurity = True
 
     @classmethod
@@ -357,9 +508,9 @@ class OpenSSLHashFunctionsTrait(HashFunctionsTrait):
 
     def _find_constructor(self, digestname):
         self.is_valid_digest_name(digestname)
-        return find_openssl_hashdigest_constructor(
-            digestname, usedforsecurity=self.usedforsecurity
-        )
+        # This returns a function of the form _hashlib.openssl_<name> and
+        # not a lambda function as it is rejected by _hashlib.hmac_new().
+        return _openssl_hash(digestname, usedforsecurity=self.usedforsecurity)
 
 
 class BuiltinHashFunctionsTrait(HashFunctionsTrait):
@@ -370,49 +521,14 @@ class BuiltinHashFunctionsTrait(HashFunctionsTrait):
     is not since the former is unconditionally built.
     """
 
-    def _find_constructor_in(self, module, digestname):
+    def _find_constructor(self, digestname):
         self.is_valid_digest_name(digestname)
-        return find_builtin_hashdigest_constructor(module, digestname)
-
-    @property
-    def md5(self):
-        return self._find_constructor_in("_md5", "md5")
-
-    @property
-    def sha1(self):
-        return self._find_constructor_in("_sha1", "sha1")
-
-    @property
-    def sha224(self):
-        return self._find_constructor_in("_sha2", "sha224")
-
-    @property
-    def sha256(self):
-        return self._find_constructor_in("_sha2", "sha256")
-
-    @property
-    def sha384(self):
-        return self._find_constructor_in("_sha2", "sha384")
-
-    @property
-    def sha512(self):
-        return self._find_constructor_in("_sha2", "sha512")
-
-    @property
-    def sha3_224(self):
-        return self._find_constructor_in("_sha3", "sha3_224")
-
-    @property
-    def sha3_256(self):
-        return self._find_constructor_in("_sha3","sha3_256")
-
-    @property
-    def sha3_384(self):
-        return self._find_constructor_in("_sha3","sha3_384")
-
-    @property
-    def sha3_512(self):
-        return self._find_constructor_in("_sha3","sha3_512")
+        info = _EXPLICIT_CONSTRUCTORS[digestname]
+        return _builtin_hash(
+            info.builtin_module_name,
+            info.builtin_method_name,
+            usedforsecurity=self.usedforsecurity,
+        )
 
 
 def find_gil_minsize(modules_names, default=2048):
@@ -426,38 +542,45 @@ def find_gil_minsize(modules_names, default=2048):
     """
     sizes = []
     for module_name in modules_names:
-        try:
-            module = importlib.import_module(module_name)
-        except ImportError:
-            continue
-        sizes.append(getattr(module, '_GIL_MINSIZE', default))
+        module = try_import_module(module_name)
+        if module is not None:
+            sizes.append(getattr(module, '_GIL_MINSIZE', default))
     return max(sizes, default=default)
 
 
 def _block_openssl_hash_new(blocked_name):
     """Block OpenSSL implementation of _hashlib.new()."""
     assert isinstance(blocked_name, str), blocked_name
-    if _hashlib is None:
+
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := try_import_module("_hashlib")) is None:
         return contextlib.nullcontext()
+
     @functools.wraps(wrapped := _hashlib.new)
-    def wrapper(name, data=b'', *, usedforsecurity=True, string=None):
+    def _hashlib_new(name, data=b'', *, usedforsecurity=True, string=None):
         if name == blocked_name:
             raise _hashlib.UnsupportedDigestmodError(blocked_name)
-        return wrapped(*args, **kwargs)
-    _ensure_wrapper_signature(wrapper, wrapped)
-    return unittest.mock.patch('_hashlib.new', wrapper)
+        return wrapped(name, data,
+                       usedforsecurity=usedforsecurity, string=string)
+
+    _ensure_wrapper_signature(_hashlib_new, wrapped)
+    return unittest.mock.patch('_hashlib.new', _hashlib_new)
 
 
 def _block_openssl_hmac_new(blocked_name):
     """Block OpenSSL HMAC-HASH implementation."""
     assert isinstance(blocked_name, str), blocked_name
-    if _hashlib is None:
+
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := try_import_module("_hashlib")) is None:
         return contextlib.nullcontext()
+
     @functools.wraps(wrapped := _hashlib.hmac_new)
     def wrapper(key, msg=b'', digestmod=None):
         if digestmod == blocked_name:
             raise _hashlib.UnsupportedDigestmodError(blocked_name)
         return wrapped(key, msg, digestmod)
+
     _ensure_wrapper_signature(wrapper, wrapped)
     return unittest.mock.patch('_hashlib.hmac_new', wrapper)
 
@@ -465,112 +588,132 @@ def wrapper(key, msg=b'', digestmod=None):
 def _block_openssl_hmac_digest(blocked_name):
     """Block OpenSSL HMAC-HASH one-shot digest implementation."""
     assert isinstance(blocked_name, str), blocked_name
-    if _hashlib is None:
+
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := try_import_module("_hashlib")) is None:
         return contextlib.nullcontext()
+
     @functools.wraps(wrapped := _hashlib.hmac_digest)
-    def wrapper(key, msg, digest):
+    def _hashlib_hmac_digest(key, msg, digest):
         if digest == blocked_name:
             raise _hashlib.UnsupportedDigestmodError(blocked_name)
-        return wrapped(key, msg, digestmod)
-    _ensure_wrapper_signature(wrapper, wrapped)
-    return unittest.mock.patch('_hashlib.hmac_digest', wrapper)
+        return wrapped(key, msg, digest)
+
+    _ensure_wrapper_signature(_hashlib_hmac_digest, wrapped)
+    return unittest.mock.patch('_hashlib.hmac_digest', _hashlib_hmac_digest)
 
 
-@contextlib.contextmanager
 def _block_builtin_hash_new(name):
+    """Block a buitin-in hash name from the hashlib.new() interface."""
     assert isinstance(name, str), name
     assert name.lower() == name, f"invalid name: {name}"
+    assert name in HID, f"invalid hash: {name}"
 
-    builtin_cache = getattr(hashlib, '__builtin_constructor_cache')
-    if name in builtin_cache:
-        f = builtin_cache.pop(name)
-        F = builtin_cache.pop(name.upper(), None)
-    else:
-        f = F = None
-    try:
-        yield
-    finally:
-        if f is not None:
-            builtin_cache[name] = f
-        if F is not None:
-            builtin_cache[name.upper()] = F
+    # Re-import 'hashlib' in case it was mocked
+    hashlib = importlib.import_module('hashlib')
+    builtin_constructor_cache = getattr(hashlib, '__builtin_constructor_cache')
+    builtin_constructor_cache_mock = builtin_constructor_cache.copy()
+    builtin_constructor_cache_mock.pop(name, None)
+    builtin_constructor_cache_mock.pop(name.upper(), None)
+
+    # __get_builtin_constructor() imports the HACL* modules on demand,
+    # so we need to block the possibility of importing it, but only
+    # during the call to __get_builtin_constructor().
+    get_builtin_constructor = getattr(hashlib, '__get_builtin_constructor')
+    builtin_module_name = _EXPLICIT_CONSTRUCTORS[name].builtin_module_name
+
+    @functools.wraps(get_builtin_constructor)
+    def get_builtin_constructor_mock(name):
+        with import_helper.isolated_modules():
+            sys = importlib.import_module("sys")
+            sys.modules[builtin_module_name] = None  # block module's import
+            return get_builtin_constructor(name)
+
+    return unittest.mock.patch.multiple(
+        hashlib,
+        __get_builtin_constructor=get_builtin_constructor_mock,
+        __builtin_constructor_cache=builtin_constructor_cache_mock
+    )
 
 
 def _block_builtin_hmac_new(blocked_name):
     assert isinstance(blocked_name, str), blocked_name
-    if _hmac is None:
+
+    # re-import '_hmac' in case it was mocked
+    if (_hmac := try_import_module("_hmac")) is None:
         return contextlib.nullcontext()
+
     @functools.wraps(wrapped := _hmac.new)
-    def wrapper(key, msg=None, digestmod=None):
+    def _hmac_new(key, msg=None, digestmod=None):
         if digestmod == blocked_name:
             raise _hmac.UnknownHashError(blocked_name)
         return wrapped(key, msg, digestmod)
-    _ensure_wrapper_signature(wrapper, wrapped)
-    return unittest.mock.patch('_hmac.new', wrapper)
+
+    _ensure_wrapper_signature(_hmac_new, wrapped)
+    return unittest.mock.patch('_hmac.new', _hmac_new)
 
 
 def _block_builtin_hmac_digest(blocked_name):
     assert isinstance(blocked_name, str), blocked_name
-    if _hmac is None:
+
+    # re-import '_hmac' in case it was mocked
+    if (_hmac := try_import_module("_hmac")) is None:
         return contextlib.nullcontext()
+
     @functools.wraps(wrapped := _hmac.compute_digest)
-    def wrapper(key, msg, digest):
+    def _hmac_compute_digest(key, msg, digest):
         if digest == blocked_name:
             raise _hmac.UnknownHashError(blocked_name)
         return wrapped(key, msg, digest)
-    _ensure_wrapper_signature(wrapper, wrapped)
-    return unittest.mock.patch('_hmac.compute_digest', wrapper)
+
+    _ensure_wrapper_signature(_hmac_compute_digest, wrapped)
+    return unittest.mock.patch('_hmac.compute_digest', _hmac_compute_digest)
 
 
-def _make_hash_constructor_blocker(name, dummy, *, interface):
-    assert isinstance(name, str), name
-    assert interface in ('builtin', 'openssl', 'hashlib')
-    assert name in _EXPLICIT_CONSTRUCTORS, f"invalid hash: {name}"
-    fullname = _EXPLICIT_CONSTRUCTORS[name].fullname(interface)
-    if fullname is None:
+def _make_hash_constructor_blocker(name, dummy, implementation):
+    info = _EXPLICIT_CONSTRUCTORS[name]
+    module_name = info.module_name(implementation)
+    method_name = info.method_name(implementation)
+    if module_name is None or method_name is None:
         # function shouldn't exist for this implementation
         return contextlib.nullcontext()
-    assert fullname.count('.') == 1, fullname
-    module_name, method = fullname.split('.', maxsplit=1)
+
     try:
         module = importlib.import_module(module_name)
     except ImportError:
         # module is already disabled
         return contextlib.nullcontext()
-    wrapped = getattr(module, method)
+
+    wrapped = getattr(module, method_name)
     wrapper = functools.wraps(wrapped)(dummy)
     _ensure_wrapper_signature(wrapper, wrapped)
-    return unittest.mock.patch(fullname, wrapper)
+    return unittest.mock.patch(info.fullname(implementation), wrapper)
 
 
 def _block_hashlib_hash_constructor(name):
     """Block explicit public constructors."""
-    assert isinstance(name, str), name
     def dummy(data=b'', *, usedforsecurity=True, string=None):
-        raise ValueError(f"unsupported hash name: {name}")
-    return _make_hash_constructor_blocker(name, dummy, interface='hashlib')
+        raise ValueError(f"blocked explicit public hash name: {name}")
+
+    return _make_hash_constructor_blocker(name, dummy, 'hashlib')
 
 
 def _block_openssl_hash_constructor(name):
     """Block explicit OpenSSL constructors."""
-    assert isinstance(name, str), name
     def dummy(data=b'', *, usedforsecurity=True, string=None):
-        raise ValueError(f"unsupported hash name: {name}")
-    return _make_hash_constructor_blocker(name, dummy, interface='openssl')
+        raise ValueError(f"blocked explicit OpenSSL hash name: {name}")
+    return _make_hash_constructor_blocker(name, dummy, 'openssl')
 
 
 def _block_builtin_hash_constructor(name):
     """Block explicit HACL* constructors."""
-    assert isinstance(name, str), name
     def dummy(data=b'', *, usedforsecurity=True, string=b''):
-        raise ValueError(f"unsupported hash name: {name}")
-    return _make_hash_constructor_blocker(name, dummy, interface='builtin')
+        raise ValueError(f"blocked explicit builtin hash name: {name}")
+    return _make_hash_constructor_blocker(name, dummy, 'builtin')
 
 
 def _block_builtin_hmac_constructor(name):
     """Block explicit HACL* HMAC constructors."""
-    assert isinstance(name, str), name
-    assert name in _EXPLICIT_HMAC_CONSTRUCTORS, f"invalid hash: {name}"
     fullname = _EXPLICIT_HMAC_CONSTRUCTORS[name]
     if fullname is None:
         # function shouldn't exist for this implementation
@@ -585,7 +728,7 @@ def _block_builtin_hmac_constructor(name):
         return contextlib.nullcontext()
     @functools.wraps(wrapped := getattr(module, method))
     def wrapper(key, obj):
-        raise ValueError(f"unsupported hash name: {name}")
+        raise ValueError(f"blocked hash name: {name}")
     _ensure_wrapper_signature(wrapper, wrapped)
     return unittest.mock.patch(fullname, wrapper)
 
@@ -600,22 +743,54 @@ def block_algorithm(name, *, allow_openssl=False, allow_builtin=False):
     """
     with contextlib.ExitStack() as stack:
         if not (allow_openssl or allow_builtin):
-            # If one of the private interface is allowed, then the
-            # public interface will fallback to it even though the
-            # comment in hashlib.py says otherwise.
+            # Named constructors have a different behavior in the sense
+            # that they are either built-ins or OpenSSL ones, but not
+            # "agile" ones (namely once "hashlib" has been imported,
+            # they are fixed).
             #
-            # So we should only block it if the private interfaces
-            # are blocked as well.
+            # If OpenSSL is not available, hashes fall back to built-in ones,
+            # in which case we don't need to block the explicit public hashes
+            # as they will call a mocked one.
+            #
+            # If OpenSSL is available, hashes fall back to "openssl_*" ones,
+            # except for BLAKE2b and BLAKE2s.
             stack.enter_context(_block_hashlib_hash_constructor(name))
+        elif (
+            # In FIPS mode, hashlib.<name>() functions may raise if they use
+            # the OpenSSL implementation, except with usedforsecurity=False.
+            # However, blocking such functions also means blocking them
+            # so we again need to block them if we want to.
+            (_hashlib := try_import_module("_hashlib"))
+            and _hashlib.get_fips_mode()
+            and not allow_openssl
+        ) or (
+            # Without OpenSSL, hashlib.<name>() functions are aliases
+            # to built-in functions, so both of them must be blocked
+            # as the module may have been imported before the HACL ones.
+            not (_hashlib := try_import_module("_hashlib"))
+            and not allow_builtin
+        ):
+            stack.enter_context(_block_hashlib_hash_constructor(name))
+
         if not allow_openssl:
+            # _hashlib.new()
             stack.enter_context(_block_openssl_hash_new(name))
-            stack.enter_context(_block_openssl_hmac_new(name))
-            stack.enter_context(_block_openssl_hmac_digest(name))
+            # _hashlib.openssl_*()
             stack.enter_context(_block_openssl_hash_constructor(name))
+            # _hashlib.hmac_new()
+            stack.enter_context(_block_openssl_hmac_new(name))
+            # _hashlib.hmac_digest()
+            stack.enter_context(_block_openssl_hmac_digest(name))
+
         if not allow_builtin:
+            # __get_builtin_constructor(name)
             stack.enter_context(_block_builtin_hash_new(name))
-            stack.enter_context(_block_builtin_hmac_new(name))
-            stack.enter_context(_block_builtin_hmac_digest(name))
+            # <built-in module>.<built-in name>()
             stack.enter_context(_block_builtin_hash_constructor(name))
+            # _hmac.new(..., name)
+            stack.enter_context(_block_builtin_hmac_new(name))
+            # _hmac.compute_<name>()
             stack.enter_context(_block_builtin_hmac_constructor(name))
+            # _hmac.compute_digest(..., name)
+            stack.enter_context(_block_builtin_hmac_digest(name))
         yield

Lib/test/test_hashlib.py

@@ -545,13 +545,17 @@ def check(self, name, data, hexdigest, shake=False, **kwargs):
 
     def check_file_digest(self, name, data, hexdigest):
         hexdigest = hexdigest.lower()
-        try:
-            hashlib.new(name)
-        except ValueError:
-            # skip, algorithm is blocked by security policy.
-            return
-        digests = [name]
-        digests.extend(self.constructors_to_test[name])
+        digests = []
+        for digest in [name, *self.constructors_to_test[name]]:
+            try:
+                if callable(digest):
+                    digest(b"")
+                else:
+                    hashlib.new(digest)
+            except ValueError:
+                # skip, algorithm is blocked by security policy.
+                continue
+            digests.append(digest)
 
         with tempfile.TemporaryFile() as f:
             f.write(data)

Lib/test/test_support.py

@@ -2,6 +2,7 @@
 import errno
 import importlib
 import itertools
+import inspect
 import io
 import logging
 import os
@@ -820,6 +821,7 @@ def test_linked_to_musl(self):
     # SuppressCrashReport
 
 
+@hashlib_helper.requires_builtin_hashes()
 class TestHashlibSupport(unittest.TestCase):
 
     @classmethod
@@ -828,11 +830,20 @@ def setUpClass(cls):
         cls.hashlib = import_helper.import_module("hashlib")
         cls.hmac = import_helper.import_module("hmac")
 
-        # We required the extension modules to be present since blocking
-        # HACL* implementations while allowing OpenSSL ones would still
-        # result in failures.
+        # All C extension modules must be present since blocking
+        # the built-in implementation while allowing OpenSSL or vice-versa
+        # may result in failures depending on the exposed built-in hashes.
         cls._hashlib = import_helper.import_module("_hashlib")
         cls._hmac = import_helper.import_module("_hmac")
+        cls._md5 = import_helper.import_module("_md5")
+
+    def skip_if_fips_mode(self):
+        if self._hashlib.get_fips_mode():
+            self.skipTest("disabled in FIPS mode")
+
+    def skip_if_not_fips_mode(self):
+        if not self._hashlib.get_fips_mode():
+            self.skipTest("requires FIPS mode")
 
     def check_context(self, disabled=True):
         if disabled:
@@ -853,25 +864,19 @@ def try_import_attribute(self, fullname, default=None):
         except TypeError:
             return default
 
-    def validate_modules(self):
-        if hasattr(hashlib_helper, 'hashlib'):
-            self.assertIs(hashlib_helper.hashlib, self.hashlib)
-        if hasattr(hashlib_helper, 'hmac'):
-            self.assertIs(hashlib_helper.hmac, self.hmac)
-
-    def fetch_hash_function(self, name, typ):
-        entry = hashlib_helper._EXPLICIT_CONSTRUCTORS[name]
-        match typ:
+    def fetch_hash_function(self, name, implementation):
+        info = hashlib_helper.get_hash_info(name)
+        match implementation:
             case "hashlib":
-                assert entry.hashlib is not None, entry
-                return getattr(self.hashlib, entry.hashlib)
+                assert info.hashlib is not None, info
+                return getattr(self.hashlib, info.hashlib)
             case "openssl":
                 try:
-                    return getattr(self._hashlib, entry.openssl, None)
+                    return getattr(self._hashlib, info.openssl, None)
                 except TypeError:
                     return None
-            case "builtin":
-                return self.try_import_attribute(entry.fullname(typ))
+        fullname = info.fullname(implementation)
+        return self.try_import_attribute(fullname)
 
     def fetch_hmac_function(self, name):
         fullname = hashlib_helper._EXPLICIT_HMAC_CONSTRUCTORS[name]
@@ -936,16 +941,12 @@ def check_builtin_hmac(self, name, *, disabled=True):
     )
     def test_disable_hash(self, name, allow_openssl, allow_builtin):
         # In FIPS mode, the function may be available but would still need
-        # to raise a ValueError. For simplicity, we don't test the helper
-        # when we're in FIPS mode.
-        if self._hashlib.get_fips_mode():
-            self.skipTest("hash functions may still be blocked in FIPS mode")
+        # to raise a ValueError, so we will test the helper separately.
+        self.skip_if_fips_mode()
         flags = dict(allow_openssl=allow_openssl, allow_builtin=allow_builtin)
-        is_simple_disabled = not allow_builtin and not allow_openssl
+        is_fully_disabled = not allow_builtin and not allow_openssl
 
         with hashlib_helper.block_algorithm(name, **flags):
-            self.validate_modules()
-
             # OpenSSL's blake2s and blake2b are unknown names
             # when only the OpenSSL interface is available.
             if allow_openssl and not allow_builtin:
@@ -954,25 +955,104 @@ def test_disable_hash(self, name, allow_openssl, allow_builtin):
             else:
                 name_for_hashlib_new = name
 
-            with self.check_context(is_simple_disabled):
+            with self.check_context(is_fully_disabled):
                 _ = self.hashlib.new(name_for_hashlib_new)
-            with self.check_context(is_simple_disabled):
-                _ = getattr(self.hashlib, name)(b"")
+
+            # Since _hashlib is present, explicit blake2b/blake2s constructors
+            # use the built-in implementation, while others (since we are not
+            # in FIPS mode and since _hashlib exists) use the OpenSSL function.
+            with self.check_context(is_fully_disabled):
+                _ = getattr(self.hashlib, name)()
 
             self.check_openssl_hash(name, disabled=not allow_openssl)
             self.check_builtin_hash(name, disabled=not allow_builtin)
 
             if name not in hashlib_helper.NON_HMAC_DIGEST_NAMES:
-                with self.check_context(is_simple_disabled):
+                with self.check_context(is_fully_disabled):
                     _ = self.hmac.new(b"", b"", name)
-                with self.check_context(is_simple_disabled):
+                with self.check_context(is_fully_disabled):
                     _ = self.hmac.HMAC(b"", b"", name)
-                with self.check_context(is_simple_disabled):
+                with self.check_context(is_fully_disabled):
                     _ = self.hmac.digest(b"", b"", name)
 
                 self.check_openssl_hmac(name, disabled=not allow_openssl)
                 self.check_builtin_hmac(name, disabled=not allow_builtin)
 
+    @hashlib_helper.block_algorithm("md5")
+    def test_disable_hash_md5_in_fips_mode(self):
+        self.skip_if_not_fips_mode()
+
+        self.assertRaises(ValueError, self.hashlib.new, "md5")
+        self.assertRaises(ValueError, self._hashlib.new, "md5")
+        self.assertRaises(ValueError, self.hashlib.md5)
+        self.assertRaises(ValueError, self._hashlib.openssl_md5)
+
+        kwargs = dict(usedforsecurity=True)
+        self.assertRaises(ValueError, self.hashlib.new, "md5", **kwargs)
+        self.assertRaises(ValueError, self._hashlib.new, "md5", **kwargs)
+        self.assertRaises(ValueError, self.hashlib.md5, **kwargs)
+        self.assertRaises(ValueError, self._hashlib.openssl_md5, **kwargs)
+
+    @hashlib_helper.block_algorithm("md5", allow_openssl=True)
+    def test_disable_hash_md5_in_fips_mode_allow_openssl(self):
+        self.skip_if_not_fips_mode()
+        # Allow the OpenSSL interface to be used but not the HACL* one.
+        # hashlib.new("md5") is dispatched to hashlib.openssl_md5()
+        self.assertRaises(ValueError, self.hashlib.new, "md5")
+        # dispatched to hashlib.openssl_md5() in FIPS mode
+        h2 = self.hashlib.new("md5", usedforsecurity=False)
+        self.assertIsInstance(h2, self._hashlib.HASH)
+
+        # block_algorithm() does not mock hashlib.md5 and _hashlib.openssl_md5
+        self.assertNotHasAttr(self.hashlib.md5, "__wrapped__")
+        self.assertNotHasAttr(self._hashlib.openssl_md5, "__wrapped__")
+
+        hashlib_md5 = inspect.unwrap(self.hashlib.md5)
+        self.assertIs(hashlib_md5, self._hashlib.openssl_md5)
+        self.assertRaises(ValueError, self.hashlib.md5)
+        # allow MD5 to be used in FIPS mode if usedforsecurity=False
+        h3 = self.hashlib.md5(usedforsecurity=False)
+        self.assertIsInstance(h3, self._hashlib.HASH)
+
+    @hashlib_helper.block_algorithm("md5", allow_builtin=True)
+    def test_disable_hash_md5_in_fips_mode_allow_builtin(self):
+        self.skip_if_not_fips_mode()
+        # Allow the HACL* interface to be used but not the OpenSSL one.
+        h1 = self.hashlib.new("md5")  # dispatched to _md5.md5()
+        self.assertNotIsInstance(h1, self._hashlib.HASH)
+        h2 = self.hashlib.new("md5", usedforsecurity=False)
+        self.assertIsInstance(h2, type(h1))
+
+        # block_algorithm() mocks hashlib.md5 and _hashlib.openssl_md5
+        self.assertHasAttr(self.hashlib.md5, "__wrapped__")
+        self.assertHasAttr(self._hashlib.openssl_md5, "__wrapped__")
+
+        hashlib_md5 = inspect.unwrap(self.hashlib.md5)
+        openssl_md5 = inspect.unwrap(self._hashlib.openssl_md5)
+        self.assertIs(hashlib_md5, openssl_md5)
+        self.assertRaises(ValueError, self.hashlib.md5)
+        self.assertRaises(ValueError, self.hashlib.md5,
+                          usedforsecurity=False)
+
+    @hashlib_helper.block_algorithm("md5",
+                                    allow_openssl=True,
+                                    allow_builtin=True)
+    def test_disable_hash_md5_in_fips_mode_allow_all(self):
+        self.skip_if_not_fips_mode()
+        # hashlib.new() isn't blocked as it falls back to _md5.md5
+        self.assertIsInstance(self.hashlib.new("md5"), self._md5.MD5Type)
+        self.assertRaises(ValueError, self._hashlib.new, "md5")
+        h = self._hashlib.new("md5", usedforsecurity=False)
+        self.assertIsInstance(h, self._hashlib.HASH)
+
+        self.assertNotHasAttr(self.hashlib.md5, "__wrapped__")
+        self.assertNotHasAttr(self._hashlib.openssl_md5, "__wrapped__")
+
+        self.assertIs(self.hashlib.md5, self._hashlib.openssl_md5)
+        self.assertRaises(ValueError, self.hashlib.md5)
+        h = self.hashlib.md5(usedforsecurity=False)
+        self.assertIsInstance(h, self._hashlib.HASH)
+
 
 if __name__ == '__main__':
     unittest.main()