chore: sanitize model name inputs

PiperOrigin-RevId: 828998104

Author: speedstorm1

google/genai/_transformers.py

@@ -199,6 +199,8 @@ def _resource_name(
 def t_model(client: _api_client.BaseApiClient, model: str) -> str:
   if not model:
     raise ValueError('model is required.')
+  if '..' in model or '?' in model or '&' in model:
+    raise ValueError('invalid model parameter.')
   if client.vertexai:
     if (
         model.startswith('projects/')

google/genai/tests/models/test_generate_content.py

@@ -502,6 +502,33 @@ class InstrumentEnum(Enum):
         ),
         ignore_keys=['parsed'],
     ),
+    pytest_helper.TestTableItem(
+        name='test_invalid_model_parameter_path',
+        parameters=types._GenerateContentParameters(
+            model='gemini-2.5-flash/../../upload/v1beta/files',
+            contents=t.t_contents('What is your name?'),
+        ),
+        exception_if_vertex='invalid model parameter',
+        exception_if_mldev='invalid model parameter',
+    ),
+    pytest_helper.TestTableItem(
+        name='test_invalid_model_parameter_question_mark',
+        parameters=types._GenerateContentParameters(
+            model='gemini-2.5-flash?',
+            contents=t.t_contents('What is your name?'),
+        ),
+        exception_if_vertex='invalid model parameter',
+        exception_if_mldev='invalid model parameter',
+    ),
+    pytest_helper.TestTableItem(
+        name='test_invalid_model_parameter_ampersand',
+        parameters=types._GenerateContentParameters(
+            model='gemini-2.5-flash&',
+            contents=t.t_contents('What is your name?'),
+        ),
+        exception_if_vertex='invalid model parameter',
+        exception_if_mldev='invalid model parameter',
+    ),
 ]
 
 pytestmark = pytest_helper.setup(