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GH-161739: Don't test PBKDF2 HMAC on FIPS with len(salt) < 16 #161748

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GH-161739: Don't test PBKDF2 HMAC on FIPS with len(salt) < 16 #161748

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GH-161739: Don't test PBKDF2 HMAC on FIPS with len(salt) < 16
hroncok Nov 10, 2026
35c8eb2
fixup! GH-161739: Don't test PBKDF2 HMAC on FIPS with len(salt) < 16
hroncok Nov 10, 2026
c661c00
Update Lib/test/test_hashlib.py
hroncok Nov 10, 2026
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37 changes: 34 additions & 3 deletions Lib/test/test_hashlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1236,6 +1236,9 @@ class KDFTests(unittest.TestCase):
(b'passwordPASSWORDpassword', b'saltSALTsaltSALTsaltSALTsaltSALTsalt',
4096, -1),
(b'pass\0word', b'sa\0lt', 4096, 16),

@vstinner vstinner Nov 10, 2026

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It might be interesting to test also this case (null bytes) using b'sa\0lt'*4.

(b'password', b'salt'*4, 1, None),

@vstinner vstinner Nov 10, 2026

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Suggested change
(b'password', b'salt'*4, 1, None),
# FIPS needs salt of at least 128 bits (b'salt'*4 is 128-bit)
(b'password', b'salt'*4, 1, None),

@picnixz picnixz Nov 10, 2026 •
edited
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Can you add the FIPS guidelines ref here (it's NIST SP 800-132, §5.1), but since the guidelines will be ervisied (well they are under revs since 2023), you can drop the paragraph actually.

(b'password', b'salt'*4, 2, None),
(b'password', b'salt'*4, 4096, None),
]

pbkdf2_results = {
Expand All @@ -1247,7 +1250,12 @@ class KDFTests(unittest.TestCase):
#(bytes.fromhex('eefe3d61cd4da4e4e9945b3d6ba2158c2634e984'), None),
(bytes.fromhex('3d2eec4fe41c849b80c8d83662c0e44a8b291a964c'
'f2f07038'), 25),
(bytes.fromhex('56fa6aa75548099dcc37d7f03425e0c3'), None),],
(bytes.fromhex('56fa6aa75548099dcc37d7f03425e0c3'), None),
# more test vectors with FIPS compatible salt
(bytes.fromhex('7f0d22e4398436acf7bcd2cfbb9903755def9522'), None),
(bytes.fromhex('f6d0ee787450939262e452e8f1b7ceca4ccc4cba'), None),
(bytes.fromhex('b7845a91aea7946bc875fcd9d19fd515381ddf94'), None),
],
"sha256": [
(bytes.fromhex('120fb6cffcf8b32c43e7225256c4f837'
'a86548c92ccc35480805987cb70be17b'), None),
Expand All @@ -1259,7 +1267,14 @@ class KDFTests(unittest.TestCase):
# 'f7f179e89b3b0bcb17ad10e3ac6eba46'), None),
(bytes.fromhex('348c89dbcbd32b2f32d814b8116e84cf2b17'
'347ebc1800181c4e2a1fb8dd53e1c635518c7dac47e9'), 40),
(bytes.fromhex('89b69d0516f829893c696226650a8687'), None),],
(bytes.fromhex('89b69d0516f829893c696226650a8687'), None),
(bytes.fromhex('b13d6697e99cd6d1745da097ee03e4be'
'501341e76fe9161a788de3d4cd0be219'), None),
(bytes.fromhex('b3a65a254dd590fab9aacfabd5695a0b'
'd79727d2899a6a519d26f13b52d8e6f4'), None),
(bytes.fromhex('16e35b12b41f465ca64d069578d75005'
'9775ccad5df3ad53d6b204acb122d1ee'), None),
],
"sha512": [
(bytes.fromhex('867f70cf1ade02cff3752599a3a53dc4af34c7a669815ae5'
'd513554e1c8cf252c02d470a285a0501bad999bfe943c08f'
Expand All @@ -1273,7 +1288,17 @@ class KDFTests(unittest.TestCase):
(bytes.fromhex('8c0511f4c6e597c6ac6315d8f0362e225f3c501495ba23b8'
'68c005174dc4ee71115b59f9e60cd9532fa33e0f75aefe30'
'225c583a186cd82bd4daea9724a3d3b8'), 64),
(bytes.fromhex('9d9e9c4cd21fe4be24d5b8244c759665'), None),],
(bytes.fromhex('9d9e9c4cd21fe4be24d5b8244c759665'), None),
(bytes.fromhex('ccc6bd2cbf575bd344c9cf542877fc6e9372cbf1f1e1df39'
'2c6cf5f6038bb5743834aeea6f0226c4a257bbbabe7c185d'
'17999a8d2b62d89bb83d24273b8a3229'), None),
(bytes.fromhex('4dfa5258b4acd6db7d276988daf21d61ea07d44d370d81a9'
'bc1770962829689030a8c7ffc1078593f9e27a90e79165b2'
'd81a2f471ff6c10c82420a4fa76d7a06'), None),
(bytes.fromhex('7dc69993c22ab444a13574b9d71b2cafc54e68914d9ddfd0'
'0ed5c23545b854d5e0e68b7f5614eef5df9087573bab8360'
'b20267791ed7a77669005fd94b5731e2'), None),
],
}

def _test_pbkdf2_hmac(self, pbkdf2, supported):
Expand All @@ -1282,6 +1307,8 @@ def _test_pbkdf2_hmac(self, pbkdf2, supported):
continue
for i, vector in enumerate(self.pbkdf2_test_vectors):
password, salt, rounds, dklen = vector
if self.fips_incompatible_salt(salt):
continue
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expected, overwrite_dklen = results[i]
if overwrite_dklen:
dklen = overwrite_dklen
Expand Down Expand Up @@ -1325,6 +1352,10 @@ def _test_pbkdf2_hmac(self, pbkdf2, supported):
iterations=1, dklen=None)
self.assertEqual(out, self.pbkdf2_results['sha1'][0][0])

# gh-161739: FIPS requires a salt of at least 128-bit (16 bytes)
def fips_incompatible_salt(self, salt):
return get_fips_mode() and len(salt) < 16

@unittest.skipIf(openssl_hashlib is None, "requires OpenSSL bindings")
def test_pbkdf2_hmac_c(self):
self._test_pbkdf2_hmac(openssl_hashlib.pbkdf2_hmac, openssl_md_meth_names)
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Tests/2026-11-10-14-49-01.gh-issue-161739.NZTbYC.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
``test_hashlibtest_pbkdf2_hmac_c`` from ``test_haslib`` no longer fails with
``ValueError: [Provider routines] invalid salt length`` with FIPS enabled.
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