fix(proxy): probe scrypt instead of MD5 in the fips_mode OpenSSL check (#50305)

* fix(proxy): probe scrypt instead of MD5 in the fips_mode OpenSSL check

* test(proxy): fake a working scrypt so the fips_mode check tests pass on FIPS hosts

litellm/proxy/common_utils/fips.py

@@ -23,7 +23,7 @@ def _fips_mode_setting(general_settings: Mapping[str, object]) -> bool | None:
 
 
 def openssl_enforces_fips() -> bool:
-    """Python's OpenSSL runs with FIPS-only defaults and itself refuses MD5."""
+    """Python's OpenSSL runs with FIPS-only defaults and itself refuses scrypt."""
     try:
         import _hashlib
 
@@ -32,7 +32,7 @@ def openssl_enforces_fips() -> bool:
     except (ImportError, AttributeError, ValueError):
         return False
     try:
-        _hashlib.new("md5", b"", usedforsecurity=True)
+        _hashlib.scrypt(b"", salt=b"\0" * 16, n=2, r=1, p=1, dklen=16)
     except ValueError:
         return True
     return False

tests/unit/proxy/common_utils/test_fips.py

@@ -1,7 +1,6 @@
 import _hashlib
 from collections.abc import Mapping
 from contextlib import nullcontext
-from typing import Final
 from unittest.mock import Mock
 
 import pytest
@@ -17,30 +16,32 @@ from litellm.proxy.common_utils.fips import (
 )
 
 
-def _fake_openssl(monkeypatch: pytest.MonkeyPatch, *, fips_flag: int, md5_refused: bool) -> None:
-    real_new: Final = _hashlib.new
-
-    def new(name: str, data: bytes = b"", *, usedforsecurity: bool = True) -> _hashlib.HASH:
-        if name == "md5" and md5_refused:
-            raise _hashlib.UnsupportedDigestmodError("unsupported hash type")
-        return real_new(name, data, usedforsecurity=usedforsecurity)
-
+def _fake_openssl(monkeypatch: pytest.MonkeyPatch, *, fips_flag: int, scrypt_refused: bool) -> None:
     monkeypatch.setattr(_hashlib, "get_fips_mode", lambda: fips_flag)
-    monkeypatch.setattr(_hashlib, "new", new)
+    if scrypt_refused:
+        monkeypatch.setattr(_hashlib, "scrypt", Mock(side_effect=ValueError("[digital envelope routines] unsupported")))
+    else:
+        monkeypatch.setattr(_hashlib, "scrypt", Mock(return_value=b"\0" * 16))
 
 
 @pytest.mark.parametrize(
-    "fips_flag, md5_refused, enforces",
+    "fips_flag, scrypt_refused, enforces",
     [(1, True, True), (0, True, False), (1, False, False)],
-    ids=["fips", "fips-flag-off", "md5-allowed"],
+    ids=["fips", "fips-flag-off", "scrypt-allowed"],
 )
-def test_openssl_enforces_fips_needs_the_fips_flag_and_a_refused_md5(
-    monkeypatch: pytest.MonkeyPatch, fips_flag: int, md5_refused: bool, enforces: bool
+def test_openssl_enforces_fips_needs_the_fips_flag_and_a_refused_scrypt(
+    monkeypatch: pytest.MonkeyPatch, fips_flag: int, scrypt_refused: bool, enforces: bool
 ) -> None:
-    _fake_openssl(monkeypatch, fips_flag=fips_flag, md5_refused=md5_refused)
+    _fake_openssl(monkeypatch, fips_flag=fips_flag, scrypt_refused=scrypt_refused)
     assert openssl_enforces_fips() is enforces
 
 
+def test_openssl_enforces_fips_while_md5_is_still_served_for_non_security_use(monkeypatch: pytest.MonkeyPatch) -> None:
+    _fake_openssl(monkeypatch, fips_flag=1, scrypt_refused=True)
+    monkeypatch.setattr(_hashlib, "new", Mock(return_value=Mock()))
+    assert openssl_enforces_fips() is True
+
+
 def test_openssl_without_get_fips_mode_does_not_enforce_fips(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.delattr(_hashlib, "get_fips_mode")
     assert openssl_enforces_fips() is False
@@ -113,7 +114,7 @@ def test_enforce_fips_mode(
     cryptography_fips: bool,
     refusal: str | None,
 ) -> None:
-    _fake_openssl(monkeypatch, fips_flag=int(openssl_fips), md5_refused=openssl_fips)
+    _fake_openssl(monkeypatch, fips_flag=int(openssl_fips), scrypt_refused=openssl_fips)
     monkeypatch.setattr(rust_openssl, "is_fips_enabled", lambda: cryptography_fips)
 
     with pytest.raises(FipsModeError, match=refusal) if refusal else nullcontext():