PR-5790 Add CORS preflight OPTIONS request

tests/test_app.py

@@ -437,7 +437,7 @@ def test_do_auth_and_return(mock_get_urs_url, monkeypatch):
     assert response.headers == {"Location": "%2Fsome%2Fpath"}
 
 
-def test_send_cors_header(current_request, monkeypatch):
+def test_add_cors_headers(current_request, monkeypatch):
     current_request.headers = {}
     headers = {"foo": "bar"}
     app.add_cors_headers(headers)
@@ -1093,6 +1093,41 @@ def test_try_download_head_error(
     )
 
 
+@mock.patch(f"{MODULE}.b_map", None)
+def test_dynamic_url_options(current_request, monkeypatch):
+    monkeypatch.setenv("CORS_ORIGIN", "example.com")
+    current_request.headers = {
+        "origin": "example.com",
+        "access-control-request-method": "GET",
+    }
+
+    current_request.uri_params = {"proxy": "DATA-TYPE-1/PLATFORM-A/OBJECT_1"}
+
+    # Can't use the chalice test client here as it doesn't seem to understand the `{proxy+}` route
+    response = app.dynamic_url_options()
+
+    assert response.body == ""
+    assert response.status_code == 204
+    assert response.headers == {
+        "Access-Control-Allow-Origin": "example.com",
+        "Access-Control-Allow-Credentials": "true",
+        "Access-Control-Allow-Methods": "GET, HEAD, OPTIONS",
+        "Access-Control-Allow-Headers": "Authorization, Origin, X-Requested-With",
+    }
+
+
+@mock.patch(f"{MODULE}.b_map", None)
+def test_dynamic_url_options_error(current_request):
+    current_request.uri_params = {"proxy": "DATA-TYPE-1/PLATFORM-A/OBJECT_1"}
+
+    # Can't use the chalice test client here as it doesn't seem to understand the `{proxy+}` route
+    response = app.dynamic_url_options()
+
+    assert response.body == "Method Not Allowed"
+    assert response.status_code == 405
+    assert response.headers == {}
+
+
 @mock.patch(f"{MODULE}.get_yaml_file", autospec=True)
 @mock.patch(f"{MODULE}.try_download_head", autospec=True)
 @mock.patch(f"{MODULE}.b_map", None)

tests_e2e/test_cors.py

@@ -5,16 +5,73 @@ def test_cors(urls, auth_cookies):
     origin_host = "https://something.asf.alaska.edu"
 
     url = urls.join(urls.METADATA_FILE_CH)
-    origin_headers = {"origin": origin_host}
+    request_headers = {"origin": origin_host}
 
-    r = requests.get(url, cookies=auth_cookies, headers=origin_headers, allow_redirects=False)
+    r = requests.get(
+        url,
+        cookies=auth_cookies,
+        headers=request_headers,
+        allow_redirects=False,
+    )
     headers = dict(r.headers)
 
     assert headers.get("Access-Control-Allow-Origin") == origin_host
     assert headers.get("Access-Control-Allow-Credentials") == "true"
 
-    headers = {"origin": "null"}
-    r = requests.get(url, cookies=auth_cookies, headers=headers, allow_redirects=False)
+
+def test_cors_origin_null(urls, auth_cookies):
+    url = urls.join(urls.METADATA_FILE_CH)
+    request_headers = {"origin": "null"}
+    r = requests.get(
+        url,
+        cookies=auth_cookies,
+        headers=request_headers,
+        allow_redirects=False,
+    )
     headers = dict(r.headers)
 
     assert headers.get("Access-Control-Allow-Origin") == "null"
+
+
+def test_cors_preflight_options(urls, auth_cookies):
+    origin_host = "https://something.asf.alaska.edu"
+
+    url = urls.join(urls.METADATA_FILE_CH)
+    request_headers = {
+        "Origin": origin_host,
+        "Access-Control-Request-Method": "GET"
+    }
+
+    r = requests.options(
+        url,
+        cookies=auth_cookies,
+        headers=request_headers,
+        allow_redirects=False,
+    )
+    headers = dict(r.headers)
+
+    assert r.status_code == 204
+    assert headers["Access-Control-Allow-Origin"] == origin_host
+    assert set(headers["Access-Control-Allow-Methods"].split(", ")) >= {"GET", "HEAD", "OPTIONS"}
+    assert set(headers["Access-Control-Allow-Headers"].split(", ")) >= {"Authorization", "Origin"}
+
+
+def test_cors_preflight_options_origin_null(urls, auth_cookies):
+    url = urls.join(urls.METADATA_FILE_CH)
+    request_headers = {
+        "Origin": "null",
+        "Access-Control-Request-Method": "GET"
+    }
+
+    r = requests.options(
+        url,
+        cookies=auth_cookies,
+        headers=request_headers,
+        allow_redirects=False,
+    )
+    headers = dict(r.headers)
+
+    assert r.status_code == 204
+    assert headers["Access-Control-Allow-Origin"] == "null"
+    assert set(headers["Access-Control-Allow-Methods"].split(", ")) >= {"GET", "HEAD", "OPTIONS"}
+    assert set(headers["Access-Control-Allow-Headers"].split(", ")) >= {"Authorization", "Origin"}

thin_egress_app/app.py

@@ -459,17 +459,34 @@ def add_cors_headers(headers):
 
     # send CORS headers if we're configured to use them
     origin_header = app.current_request.headers.get("origin")
-    if origin_header is not None:
+    if is_cors_allowed():
+        headers["Access-Control-Allow-Origin"] = origin_header
+        headers["Access-Control-Allow-Credentials"] = "true"
+    else:
         cors_origin = os.getenv("CORS_ORIGIN")
-        if cors_origin and (origin_header.endswith(cors_origin) or origin_header.lower() == "null"):
-            headers["Access-Control-Allow-Origin"] = origin_header
-            headers["Access-Control-Allow-Credentials"] = "true"
-        else:
-            log.warning(
-                "Origin %s is not an approved CORS host: %s",
-                origin_header,
-                cors_origin,
-            )
+        log.warning(
+            "Origin %s is not an approved CORS host: %s",
+            origin_header,
+            cors_origin,
+        )
+
+
+def is_cors_allowed():
+    assert app.current_request is not None
+
+    # send CORS headers if we're configured to use them
+    origin_header = app.current_request.headers.get("origin")
+    cors_origin = os.getenv("CORS_ORIGIN")
+
+    log.debug("origin_header: %r, cors_origin: %r", origin_header, cors_origin)
+    return bool(
+        origin_header
+        and cors_origin
+        and (
+            origin_header.endswith(cors_origin)
+            or origin_header.lower() == "null"
+        )
+    )
 
 
 @with_trace()
@@ -942,6 +959,47 @@ def try_download_head(bucket, filename):
     return make_redirect(presigned_url, {}, 303)
 
 
+@app.route("/{proxy+}", methods=["OPTIONS"])
+@with_trace(context={})
+def dynamic_url_options():
+    allowed_methods = [
+        "GET",
+        "HEAD",
+        "OPTIONS",
+    ]
+    allowed_headers = [
+        "Authorization",
+        "Origin",
+        "X-Requested-With",
+    ]
+    request_method = app.current_request.headers.get(
+        "access-control-request-method",
+        "",
+    ).strip()
+    log.info("Received CORS preflight request for method: %r", request_method)
+
+    log.debug("is_cors_allowed: %s", is_cors_allowed())
+    log.debug("request_method in allowed_methods: %s", request_method in allowed_methods)
+    if is_cors_allowed() and request_method in allowed_methods:
+        headers = {
+            "Access-Control-Allow-Methods": ", ".join(allowed_methods),
+            "Access-Control-Allow-Headers": ", ".join(allowed_headers),
+        }
+        add_cors_headers(headers)
+        log.info("Returning success response")
+        return Response(
+            body="",
+            headers=headers,
+            status_code=204,
+        )
+
+    log.info("Returning error response")
+    return Response(
+        body="Method Not Allowed",
+        status_code=405,
+    )
+
+
 # Attempt to validate HEAD request
 @app.route("/{proxy+}", methods=["HEAD"])
 @with_trace(context={})