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Commitad0fab8

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gh-127298: When in FIPS mode ensure builtin hashes check for usedforsecurity=False
When _hashlib/OpenSSL is available, and OpenSSL is in FIPS mode,ensure that builtin (fallback) hash implementations are wrapped with acheck for usedforsecurity=False. It is likely that buitinimplementations are FIPS unapproved (either algorithm disallowed; orthe implementation not certified by NIST).This enables strict approved-only compliance when usedforsecurity=Trueon FIPS systems only.And yet it also enables fallback access with usedforsecurity=False forany missing (historical, disallowed or missing certifiedimplementation) algorithms (i.e. blake2, md5, shake/sha3) depending onthe runtime configuration of OpenSSL.
1 parent2b0e2b2 commitad0fab8

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6 files changed

+116
-16
lines changed

6 files changed

+116
-16
lines changed

‎Lib/hashlib.py

Lines changed: 32 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -79,6 +79,23 @@
7979
'blake2b','blake2s',
8080
}
8181

82+
# Wrapper that only allows usage when usedforsecurity=False
83+
# (effectively unapproved service indicator)
84+
def__usedforsecurity_check(md,name,*args,**kwargs):
85+
ifkwargs.get("usedforsecurity",True):
86+
raiseValueError(name+" is blocked when usedforsecurity=True")
87+
returnmd(*args,**kwargs)
88+
89+
# If _hashlib is in FIPS mode, use the above wrapper to ensure builtin
90+
# implementation checks usedforsecurity kwarg. It means all builtin
91+
# implementations are treated as an unapproved implementation, as they
92+
# are unlikely to have been certified by NIST.
93+
def__get_wrapped_builtin(md,name):
94+
if_hashlibisnotNoneand_hashlib.get_fips_mode()==1:
95+
fromfunctoolsimportpartial
96+
returnpartial(__usedforsecurity_check,md,name)
97+
returnmd
98+
8299
def__get_builtin_constructor(name):
83100
cache=__builtin_constructor_cache
84101
constructor=cache.get(name)
@@ -87,32 +104,32 @@ def __get_builtin_constructor(name):
87104
try:
88105
ifnamein {'SHA1','sha1'}:
89106
import_sha1
90-
cache['SHA1']=cache['sha1']=_sha1.sha1
107+
cache['SHA1']=cache['sha1']=__get_wrapped_builtin(_sha1.sha1,name)
91108
elifnamein {'MD5','md5'}:
92109
import_md5
93-
cache['MD5']=cache['md5']=_md5.md5
110+
cache['MD5']=cache['md5']=__get_wrapped_builtin(_md5.md5,name)
94111
elifnamein {'SHA256','sha256','SHA224','sha224'}:
95112
import_sha2
96-
cache['SHA224']=cache['sha224']=_sha2.sha224
97-
cache['SHA256']=cache['sha256']=_sha2.sha256
113+
cache['SHA224']=cache['sha224']=__get_wrapped_builtin(_sha2.sha224,name)
114+
cache['SHA256']=cache['sha256']=__get_wrapped_builtin(_sha2.sha256,name)
98115
elifnamein {'SHA512','sha512','SHA384','sha384'}:
99116
import_sha2
100-
cache['SHA384']=cache['sha384']=_sha2.sha384
101-
cache['SHA512']=cache['sha512']=_sha2.sha512
117+
cache['SHA384']=cache['sha384']=__get_wrapped_builtin(_sha2.sha384,name)
118+
cache['SHA512']=cache['sha512']=__get_wrapped_builtin(_sha2.sha512,name)
102119
elifnamein {'blake2b','blake2s'}:
103120
import_blake2
104-
cache['blake2b']=_blake2.blake2b
105-
cache['blake2s']=_blake2.blake2s
121+
cache['blake2b']=__get_wrapped_builtin(_blake2.blake2b,name)
122+
cache['blake2s']=__get_wrapped_builtin(_blake2.blake2s,name)
106123
elifnamein {'sha3_224','sha3_256','sha3_384','sha3_512'}:
107124
import_sha3
108-
cache['sha3_224']=_sha3.sha3_224
109-
cache['sha3_256']=_sha3.sha3_256
110-
cache['sha3_384']=_sha3.sha3_384
111-
cache['sha3_512']=_sha3.sha3_512
125+
cache['sha3_224']=__get_wrapped_builtin(_sha3.sha3_224,name)
126+
cache['sha3_256']=__get_wrapped_builtin(_sha3.sha3_256,name)
127+
cache['sha3_384']=__get_wrapped_builtin(_sha3.sha3_384,name)
128+
cache['sha3_512']=__get_wrapped_builtin(_sha3.sha3_512,name)
112129
elifnamein {'shake_128','shake_256'}:
113130
import_sha3
114-
cache['shake_128']=_sha3.shake_128
115-
cache['shake_256']=_sha3.shake_256
131+
cache['shake_128']=__get_wrapped_builtin(_sha3.shake_128,name)
132+
cache['shake_256']=__get_wrapped_builtin(_sha3.shake_256,name)
116133
exceptImportError:
117134
pass# no extension module, this hash is unsupported.
118135

@@ -163,7 +180,7 @@ def __hash_new(name, data=b'', **kwargs):
163180
# hash, try using our builtin implementations.
164181
# This allows for SHA224/256 and SHA384/512 support even though
165182
# the OpenSSL library prior to 0.9.8 doesn't provide them.
166-
return__get_builtin_constructor(name)(data)
183+
return__get_builtin_constructor(name)(data,**kwargs)
167184

168185

169186
try:

‎Lib/test/hashlibdata/openssl.cnf

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
# Activate base provider only, with default properties fips=yes. It
2+
# means that fips mode is on, and no digest implementations are
3+
# available. Perfect for mock testing builtin FIPS wrappers.
4+
5+
config_diagnostics = 1
6+
openssl_conf = openssl_init
7+
8+
[openssl_init]
9+
providers = provider_sect
10+
alg_section = algorithm_sect
11+
12+
[provider_sect]
13+
base = base_sect
14+
15+
[base_sect]
16+
activate = 1
17+
18+
[algorithm_sect]
19+
default_properties =fips=yes

‎Lib/test/ssltests.py

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77

88
TESTS= [
99
'test_asyncio','test_ensurepip.py','test_ftplib','test_hashlib',
10-
'test_hmac','test_httplib','test_imaplib',
10+
'test_hashlib_fips','test_hmac','test_httplib','test_imaplib',
1111
'test_poplib','test_ssl','test_smtplib','test_smtpnet',
1212
'test_urllib2_localnet','test_venv','test_xmlrpc'
1313
]

‎Lib/test/test_hashlib_fips.py

Lines changed: 59 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,59 @@
1+
# Test the hashlib module usedforsecurity wrappers under fips.
2+
#
3+
# Copyright (C) 2024 Dimitri John Ledkov (dimitri.ledkov@surgut.co.uk)
4+
# Licensed to PSF under a Contributor Agreement.
5+
#
6+
7+
importos
8+
importunittest
9+
10+
OPENSSL_CONF_BACKUP=os.environ.get("OPENSSL_CONF")
11+
12+
classHashLibFIPSTestCase(unittest.TestCase):
13+
@classmethod
14+
defsetUpClass(cls):
15+
# This openssl.cnf mocks FIPS mode without any digest
16+
# loaded. It means all digests must raise ValueError when
17+
# usedforsecurity=True via either openssl or builtin
18+
# constructors
19+
OPENSSL_CONF=os.path.join(os.path.dirname(__file__),"hashlibdata","openssl.cnf")
20+
os.environ["OPENSSL_CONF"]=OPENSSL_CONF
21+
# Ensure hashlib is loading a fresh libcrypto with openssl
22+
# context affected by the above config file. Check if this can
23+
# be folded into test_hashlib.py, specifically if
24+
# import_fresh_module() results in a fresh library context
25+
importhashlib
26+
27+
defsetUp(self):
28+
try:
29+
from_hashlibimportget_fips_mode
30+
exceptImportError:
31+
self.skipTest('_hashlib not available')
32+
33+
ifget_fips_mode()!=1:
34+
self.skipTest('mocking fips mode failed')
35+
36+
@classmethod
37+
deftearDownClass(cls):
38+
ifOPENSSL_CONF_BACKUP:
39+
os.environ["OPENSSL_CONF"]=OPENSSL_CONF_BACKUP
40+
else:
41+
del(os.environ["OPENSSL_CONF"])
42+
43+
deftest_algorithms_available(self):
44+
importhashlib
45+
self.assertTrue(set(hashlib.algorithms_guaranteed).
46+
issubset(hashlib.algorithms_available))
47+
# all available algorithms must be loadable, bpo-47101
48+
self.assertNotIn("undefined",hashlib.algorithms_available)
49+
fornameinhashlib.algorithms_available:
50+
digest=hashlib.new(name,usedforsecurity=False)
51+
52+
deftest_usedforsecurity_true(self):
53+
importhashlib
54+
fornameinhashlib.algorithms_available:
55+
withself.assertRaises(ValueError):
56+
digest=hashlib.new(name,usedforsecurity=True)
57+
58+
if__name__=="__main__":
59+
unittest.main()

‎Makefile.pre.in

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2447,6 +2447,7 @@ TESTSUBDIRS=idlelib/idle_test \
24472447
test/decimaltestdata \
24482448
test/dtracedata \
24492449
test/encoded_modules \
2450+
test/hashlibdata \
24502451
test/leakers \
24512452
test/libregrtest \
24522453
test/mathdata \
Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
1+
:mod:`hashlib`'s fallback builtin hash implementations now check
2+
usedforsecurity=True, if hashlib is in FIPS mode. This ensures that
3+
approved-only implementations are in use on FIPS systems by default,
4+
and fallback ones are made available for unapproved purposes only.

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