Return 400 instead of reporting malformed requests as server errors (#8160)

## Rationale
Malformed requests, mostly from vulnerability scanners, are logged as
500s and reported to mothership as server errors. This PR returns a 4xx
for them instead, and stops reporting them.

Tomcat 11 throws on every parameter read once a query string or form
body fails to parse. Rendering the standard error page reads parameters
too, so even a 404 for such a request became a 500.

Triage notes for these mothership reports:
https://claude.ai/artifact/CtxKZANKRqfhZxs7PHEqBr

## Related Pull Requests
- LabKey/testAutomation#3247

## Changes
- Requests whose parameters can't be parsed get a plain 4xx response
using Tomcat's status code, without rendering an error page. They are
never reported to mothership.
- Multipart bodies that can't be parsed get a 400 on standard actions,
instead of being rethrown as a server error.
- WebDAV reports to mothership only for 5xx responses, and returns 400
for unparseable query strings.
- Added a unit test for the invalid-parameter handling.

Tested against a local server with probe-style requests: invalid UTF-8
and empty-name parameters, a forwarded image request, and broken
multipart POSTs to actions and WebDAV. All returned 400 with no errors
logged, and normal pages were unaffected.

## Tasks
- [x] Claude Code Review
- [x] Manual Testing - probably not needed
- [x] Test Automation
- [x] Code Review @labkey-adam

---------

Co-authored-by: Adam Rauch <adam@labkey.com>

Author: labkey-jeckels

api/src/org/labkey/api/action/SpringActionController.java

@@ -21,6 +21,7 @@
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.exception.ExceptionUtils;
 import org.apache.logging.log4j.Logger;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -73,6 +74,8 @@
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.web.HttpRequestMethodNotSupportedException;
+import org.springframework.web.multipart.MaxUploadSizeExceededException;
+import org.springframework.web.multipart.MultipartException;
 import org.springframework.web.multipart.support.StandardServletMultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.ModelAndView;
@@ -367,6 +370,11 @@ private ModelAndView handleBadRequestException(HttpServletRequest request, HttpS
     }
 
     private ModelAndView handleBadRequestException(HttpServletRequest request, HttpServletResponse response, Controller controller, BadRequestException x) throws Exception
+    {
+        return handleBadRequestException(request, response, controller, x, HttpServletResponse.SC_BAD_REQUEST);
+    }
+
+    private ModelAndView handleBadRequestException(HttpServletRequest request, HttpServletResponse response, Controller controller, BadRequestException x, int status) throws Exception
    {
        // TODO: we are assuming that all ApiActions respond with JSON and all !ApiAction respond HTML. Would be better to be explicit.
        boolean jsonResponse = controller instanceof BaseApiAction;
@@ -379,13 +387,13 @@ private ModelAndView handleBadRequestException(HttpServletRequest request, HttpS
            {
                // Issue 53120: Set content-type, status when responding with JSON content
                response.setContentType(ApiJsonWriter.CONTENT_TYPE_JSON);
-               response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
+               response.setStatus(status);
            }
 
            Writer w = response.getWriter();
            JSONObject json = new JSONObject();
            json.put("success", false);
-           json.put("status", HttpServletResponse.SC_BAD_REQUEST);
+           json.put("status", status);
            json.put("exception", x.getMessage());
            if (htmlWrappedJson)
                w.write("<html><body><textarea>");
@@ -397,7 +405,7 @@ private ModelAndView handleBadRequestException(HttpServletRequest request, HttpS
 
        if (textResponse)
        {
-           response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
+           response.setStatus(status);
            response.setContentType("text/plain");
            Writer w = response.getWriter();
            w.write(x.getMessage());
@@ -407,7 +415,7 @@ private ModelAndView handleBadRequestException(HttpServletRequest request, HttpS
        // TODO design/text for custom view
        if (x instanceof AntiVirusException)
        {
-           response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
+           response.setStatus(status);
            HttpView<?> view = SimpleErrorView.fromMessage(x.getMessage());
 
            PageConfig page = new PageConfig(request);
@@ -416,7 +424,7 @@ private ModelAndView handleBadRequestException(HttpServletRequest request, HttpS
            return null;
        }
 
-       response.sendError(HttpServletResponse.SC_BAD_REQUEST, x.getMessage());
+       response.sendError(status, x.getMessage());
        return null;
    }
 
@@ -538,6 +546,23 @@ public ModelAndView handleRequest(HttpServletRequest request, @NotNull HttpServl
                     // TODO Better/custom error report page/response
                     if (x.getCause() instanceof BadRequestException)
                         return handleBadRequestException(request, response, controller, (BadRequestException)x.getCause());
+                    if (x instanceof MultipartException && ExceptionUtil.isClientRequestFailure(x))
+                    {
+                        _log.debug("Unable to parse multipart request", x);
+                        int status;
+                        String message;
+                        if (x instanceof MaxUploadSizeExceededException)
+                        {
+                            status = HttpServletResponse.SC_REQUEST_ENTITY_TOO_LARGE;
+                            message = StringUtils.defaultIfBlank(ExceptionUtils.getRootCause(x).getMessage(), x.getMessage());
+                        }
+                        else
+                        {
+                            status = HttpServletResponse.SC_BAD_REQUEST;
+                            message = "Unable to parse multipart request";
+                        }
+                        return handleBadRequestException(request, response, controller, new BadRequestException(message, x), status);
+                    }
                     throw x;
                 }
             }

api/src/org/labkey/api/module/DefaultModule.java

@@ -1061,7 +1061,17 @@ public void dispatch(HttpServletRequest request, HttpServletResponse response, A
             return;
         }
 
-        ViewContext rootContext = new ViewContext(request, response, url);
+        ViewContext rootContext;
+        try
+        {
+            rootContext = new ViewContext(request, response, url);
+        }
+        // First parameter read; unparseable parameters would otherwise escape to Tomcat's own error handling
+        catch (IllegalStateException x)
+        {
+            ExceptionUtil.handleException(request, response, x, null, false);
+            return;
+        }
 
         Container container = rootContext.getContainer();
         if (container != null && !isAvailable(container))