fix: wildcard CORS + credentials spec violation, path-traversal guard on /icons proxy

CORS: drop allow_credentials=True. With allow_origins=['*'] Starlette reflects
the request Origin and emits Access-Control-Allow-Credentials: true on any
credentialed request — a reflect-any-origin hole. The app authenticates with
Bearer tokens in the Authorization header, so credentialed CORS was never needed.

/icons/{icon_name}: validate against a strict allowlist (re.fullmatch
[A-Za-z0-9._-]+\.png) and assert the resolved path stays inside ICONS_DIR before
any filesystem write or outbound fetch. Closes the path-traversal / arbitrary-write
(CWE-22) and controlled-URL (CWE-73) surface on the unsanitized icon_name.

Adds CORS middleware tests and icon-name validation tests (traversal, encoded
slash, null byte, trailing newline, wrong extension).

Closes #298

Signed-off-by: Devam Shah <devamshah91@gmail.com>

tests/integration/routes/test_static_icon_validation.py

@@ -0,0 +1,109 @@
+"""Tests for the /icons/{icon_name} allowlist and path-containment guard (CWE-22)."""
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from agentic_security.routes.static import ICON_NAME_RE, router
+
+_app = FastAPI()
+_app.include_router(router)
+_client = TestClient(_app, raise_server_exceptions=False)
+
+
+# ---------------------------------------------------------------------------
+# ICON_NAME_RE unit tests — no HTTP round-trip needed
+# ---------------------------------------------------------------------------
+
+
+class TestIconNameRegex:
+    """ICON_NAME_RE rejects all names that could cause path traversal or SSRF."""
+
+    @pytest.mark.parametrize(
+        "name",
+        [
+            "openai.png",
+            "claude-3.png",
+            "gpt_4.png",
+            "Anthropic.png",
+            "my.icon.png",
+            "test-icon-123.png",
+            "A.png",
+        ],
+    )
+    def test_valid_names_match(self, name: str):
+        assert ICON_NAME_RE.fullmatch(name), f"Expected {name!r} to be accepted"
+
+    @pytest.mark.parametrize(
+        "name",
+        [
+            "../etc/passwd",  # classic path traversal
+            "../../secret.png",  # multi-level traversal
+            "foo%2Fbar.png",  # percent-encoded slash
+            "foo/bar.png",  # literal slash
+            "icon.PNG",  # uppercase extension (not in the dataset)
+            "icon.jpg",  # wrong extension
+            "icon.gif",  # wrong extension
+            ".png",  # empty stem
+            "",  # empty string
+            "icon.png.sh",  # double extension — shell script suffix
+            "\x00icon.png",  # null byte
+            "icon.png\n",  # trailing newline (defeats $-anchored match)
+        ],
+    )
+    def test_invalid_names_rejected(self, name: str):
+        assert not ICON_NAME_RE.fullmatch(name), f"Expected {name!r} to be rejected"
+
+
+# ---------------------------------------------------------------------------
+# Integration tests — HTTP-level validation via TestClient
+# ---------------------------------------------------------------------------
+
+
+class TestServeIconValidation:
+    """serve_icon returns 400 for names that fail the allowlist check."""
+
+    @pytest.mark.parametrize(
+        "bad_name",
+        [
+            "no-extension",
+            "icon.jpg",
+            "icon.PNG",
+            ".png",
+            "icon.png.sh",
+        ],
+    )
+    def test_invalid_name_returns_400(self, bad_name: str):
+        """Names that fail ICON_NAME_RE get a 400 before any FS/network I/O."""
+        response = _client.get(f"/icons/{bad_name}")
+        assert (
+            response.status_code == 400
+        ), f"Expected 400 for {bad_name!r}, got {response.status_code}"
+        assert response.json().get("detail") == "Invalid icon name"
+
+    def test_valid_name_does_not_return_400(self, tmp_path, mocker):
+        """A well-formed name passes validation; 404 is acceptable when the
+        upstream fetch also fails, but 400 must not be returned."""
+        mocker.patch("agentic_security.routes.static.ICONS_DIR", tmp_path)
+
+        # Stub the external HTTP call so the test is hermetic
+        mock_resp = mocker.MagicMock()
+        mock_resp.status_code = 404
+        mocker.patch(
+            "agentic_security.routes.static.requests.get", return_value=mock_resp
+        )
+
+        response = _client.get("/icons/openai.png")
+        assert (
+            response.status_code != 400
+        ), "A valid icon name should not be rejected by the allowlist check"
+
+    def test_valid_name_served_from_cache(self, tmp_path, mocker):
+        """When the icon file already exists locally it is served directly."""
+        mocker.patch("agentic_security.routes.static.ICONS_DIR", tmp_path)
+        icon_file = tmp_path / "openai.png"
+        icon_file.write_bytes(b"\x89PNG\r\n\x1a\n")  # minimal PNG magic bytes
+
+        response = _client.get("/icons/openai.png")
+        assert response.status_code == 200
+        assert response.headers.get("content-type", "").startswith("image/png")