Validate proxy server image name

pathwaysutils/experimental/shared_pathways_service/validators.py

@@ -127,6 +127,11 @@ def validate_proxy_server_image(proxy_server_image: str) -> None:
         f"Proxy server image '{proxy_server_image}' must contain a tag with ':'"
         " or a digest with '@'."
     )
+  if not re.fullmatch(r"[A-Za-z0-9][A-Za-z0-9._/:@-]*", proxy_server_image):
+    raise ValueError(
+        f"Proxy server image '{proxy_server_image}' contains characters that"
+        " are not valid in a Docker image reference."
+    )
 
 
 def validate_xla_flags(xla_flags: Iterable[str] | None) -> None:

pathwaysutils/test/experimental/shared_pathways_service/validators_test.py

@@ -252,6 +252,30 @@ def test_validate_proxy_server_image_success(self, image):
               " with ':' or a digest with '@'."
           ),
       ),
+      dict(
+          testcase_name="newline_yaml_injection",
+          image="alpine/alpine:latest\n command: [sh, -c, 'id']",
+          expected_regex=(
+              "contains characters that are not valid in a Docker image"
+              " reference."
+          ),
+      ),
+      dict(
+          testcase_name="spaces_in_image",
+          image="gcr.io/project/image:tag extra_args",
+          expected_regex=(
+              "contains characters that are not valid in a Docker image"
+              " reference."
+          ),
+      ),
+      dict(
+          testcase_name="invalid_punctuation",
+          image="gcr.io/project/image:tag;echo pwn",
+          expected_regex=(
+              "contains characters that are not valid in a Docker image"
+              " reference."
+          ),
+      ),
   )
   def test_validate_proxy_server_image_failure(self, image, expected_regex):
     """Tests that invalid proxy server image strings raise a ValueError."""