fix(tls): ignore LITELLM_SSL_CIPHERS override under FIPS mode with a warning

litellm/constants.py

@@ -364,11 +364,12 @@ MODEL_GROUP_ALIAS_RESOLVED_SCOPE_KEY: Final = "litellm.model_group_alias_resolve
 REALTIME_SESSION_SUCCESS_LOGGED_KEY: Final = "realtime_session_success_logged"
 REALTIME_SESSION_FAILURE_LOGGED_KEY: Final = "realtime_session_failure_logged"
 
-FIPS_SSL_CIPHERS: Final = os.getenv(
-    "LITELLM_SSL_CIPHERS",
+# Certified GCM-only list: deliberately NOT overridable via LITELLM_SSL_CIPHERS so a
+# custom override cannot silently weaken the FIPS posture when LITELLM_FIPS_MODE is set.
+FIPS_SSL_CIPHERS: Final = (
     "TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:"
     "ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:"
-    "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256",
+    "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256"
 )
 DEFAULT_SSL_CIPHERS: Final = os.getenv(
     "LITELLM_SSL_CIPHERS",

litellm/llms/custom_httpx/http_handler.py

@@ -286,7 +286,13 @@ _ssl_context_cache: Final[dict[tuple[str | None, str | None, str | None, str], s
 def _outbound_ssl_ciphers() -> str:
     from litellm.proxy.common_utils.fips import is_fips_mode
 
-    return FIPS_SSL_CIPHERS if is_fips_mode() else DEFAULT_SSL_CIPHERS
+    if is_fips_mode():
+        if os.getenv("LITELLM_SSL_CIPHERS"):
+            verbose_logger.warning(
+                "LITELLM_SSL_CIPHERS override ignored in FIPS mode; using FIPS_SSL_CIPHERS"
+            )
+        return FIPS_SSL_CIPHERS
+    return DEFAULT_SSL_CIPHERS
 
 
 def _create_ssl_context(

tests/unit/llms/custom_httpx/test_http_handler.py

@@ -366,6 +366,80 @@ def test_get_ssl_configuration_uses_fips_cipher_list_only_in_fips_mode(monkeypat
     assert get_ssl_configuration() is fips_context
 
 
+_CHACHA_OVERRIDE: Final = "ECDHE-RSA-CHACHA20-POLY1305:ECDHE-RSA-AES128-SHA256"
+
+
+def _simulate_cipher_override_at_import(monkeypatch: pytest.MonkeyPatch, http_handler) -> None:
+    """Simulate a process that started with LITELLM_SSL_CIPHERS set: litellm.constants
+    re-reads the env at import and http_handler binds those values at import. Reloading
+    http_handler itself would rebind its classes and break isinstance in later tests, so
+    only constants is re-executed and the handler's bindings are swapped explicitly."""
+    from litellm import constants
+
+    importlib.reload(constants)
+    monkeypatch.setattr(http_handler, "DEFAULT_SSL_CIPHERS", constants.DEFAULT_SSL_CIPHERS)
+    monkeypatch.setattr(http_handler, "FIPS_SSL_CIPHERS", constants.FIPS_SSL_CIPHERS)
+
+
+def _restore_cipher_constants(monkeypatch: pytest.MonkeyPatch) -> None:
+    from litellm import constants
+
+    monkeypatch.delenv("LITELLM_SSL_CIPHERS", raising=False)
+    importlib.reload(constants)
+
+
+def test_get_ssl_configuration_ignores_ssl_ciphers_override_in_fips_mode(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+):
+    import logging
+
+    from litellm.llms.custom_httpx import http_handler
+
+    monkeypatch.setattr(http_handler, "_ssl_context_cache", {})
+    monkeypatch.setenv("LITELLM_SSL_CIPHERS", _CHACHA_OVERRIDE)
+    monkeypatch.setenv("LITELLM_FIPS_MODE", "true")
+    monkeypatch.delenv("SSL_SECURITY_LEVEL", raising=False)
+    monkeypatch.delenv("SSL_ECDH_CURVE", raising=False)
+
+    _simulate_cipher_override_at_import(monkeypatch, http_handler)
+    with caplog.at_level(logging.WARNING, logger="LiteLLM"):
+        context = http_handler.get_ssl_configuration()
+    _restore_cipher_constants(monkeypatch)
+
+    assert isinstance(context, ssl.SSLContext)
+    names = _context_tls12_cipher_names(context)
+    supported = _supported_tls12_cipher_names()
+    assert names == (_tls12_cipher_names(http_handler.FIPS_SSL_CIPHERS) & supported)
+    assert not any("CHACHA" in name for name in names)
+    assert "LITELLM_SSL_CIPHERS override ignored" in caplog.text
+
+
+def test_get_ssl_configuration_applies_ssl_ciphers_override_outside_fips_mode(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+):
+    import logging
+
+    from litellm.llms.custom_httpx import http_handler
+
+    monkeypatch.setattr(http_handler, "_ssl_context_cache", {})
+    monkeypatch.setenv("LITELLM_SSL_CIPHERS", _CHACHA_OVERRIDE)
+    monkeypatch.delenv("LITELLM_FIPS_MODE", raising=False)
+    monkeypatch.delenv("SSL_SECURITY_LEVEL", raising=False)
+    monkeypatch.delenv("SSL_ECDH_CURVE", raising=False)
+
+    _simulate_cipher_override_at_import(monkeypatch, http_handler)
+    with caplog.at_level(logging.WARNING, logger="LiteLLM"):
+        context = http_handler.get_ssl_configuration()
+    _restore_cipher_constants(monkeypatch)
+
+    assert isinstance(context, ssl.SSLContext)
+    names = _context_tls12_cipher_names(context)
+    supported = _supported_tls12_cipher_names()
+    assert names == (_tls12_cipher_names(_CHACHA_OVERRIDE) & supported)
+    assert any("CHACHA" in name for name in names)
+    assert "LITELLM_SSL_CIPHERS override ignored" not in caplog.text
+
+
 # Session Reuse Tests
 class MockClientSession:
     """Mock ClientSession that is not callable"""
@@ -1532,7 +1606,6 @@ async def test_connection_error_retry_forwards_content(method: str):
         await handler.close()
 
 
-
 @pytest.fixture
 def forward_proxy_server():
     """Plain HTTP forward proxy that records the absolute URIs it is asked to fetch."""
@@ -1927,6 +2000,7 @@ def _vcr_outcome_gate(request, vcr):
     yield
     record_vcr_outcome(request, vcr)
 
+
 @pytest.fixture(scope="function")
 def isolate_litellm_state():
     """
@@ -1979,6 +2053,7 @@ def isolate_litellm_state():
             setattr(litellm, attr, original_value)
     _invalidate_model_cost_lowercase_map()
 
+
 _SCALAR_DEFAULTS = {
     "num_retries": getattr(litellm, "num_retries", None),
     "num_retries_per_request": getattr(litellm, "num_retries_per_request", None),
@@ -1999,6 +2074,7 @@ _SCALAR_DEFAULTS = {
     "api_key": getattr(litellm, "api_key", None),
 }
 
+
 @pytest.fixture(scope="module")
 def setup_and_teardown():
     """
@@ -2021,12 +2097,14 @@ def setup_and_teardown():
             litellm.in_memory_llm_clients_cache.flush_cache()
     yield
 
+
 _SERVER_DELAY_S = 5
 
 _PER_REQUEST_TIMEOUT_S = 1.0
 
 _CLIENT_DEFAULT_TIMEOUT_S = 60.0
 
+
 class _SlowHandler(BaseHTTPRequestHandler):
     def do_POST(self):
         time.sleep(_SERVER_DELAY_S)
@@ -2040,6 +2118,7 @@ class _SlowHandler(BaseHTTPRequestHandler):
     def log_message(self, *args):
         pass
 
+
 @pytest.mark.usefixtures("_vcr_outcome_gate", "isolate_litellm_state", "setup_and_teardown")
 def test_post_delay_exceeds_per_request_timeout_raises():
     server = ThreadingHTTPServer(("127.0.0.1", 0), _SlowHandler)

tests/unit/test_constants.py

@@ -96,12 +96,15 @@ def test_fips_ssl_ciphers_tls12_suites_are_all_gcm():
     assert all("-GCM-" in suite for suite in tls12_suites)
 
 
-def test_ssl_ciphers_env_override_applies_to_both_lists(monkeypatch: pytest.MonkeyPatch):
+def test_ssl_ciphers_env_override_applies_to_default_list_only(monkeypatch: pytest.MonkeyPatch):
     monkeypatch.setenv("LITELLM_SSL_CIPHERS", "ECDHE-RSA-AES128-GCM-SHA256")
     importlib.reload(constants)
     try:
         assert constants.DEFAULT_SSL_CIPHERS == "ECDHE-RSA-AES128-GCM-SHA256"
-        assert constants.FIPS_SSL_CIPHERS == "ECDHE-RSA-AES128-GCM-SHA256"
+        # The FIPS list must stay certified regardless of the override so FIPS mode
+        # cannot be silently weakened by LITELLM_SSL_CIPHERS.
+        assert constants.FIPS_SSL_CIPHERS != "ECDHE-RSA-AES128-GCM-SHA256"
+        assert all("-GCM-" in suite for suite in _cipher_suites(constants.FIPS_SSL_CIPHERS) if not suite.startswith("TLS_"))
     finally:
         monkeypatch.delenv("LITELLM_SSL_CIPHERS")
         importlib.reload(constants)