Java Jersey REST Request Parameter Sanitation

Question

I'm trying to make sure my Jersey request parameters are sanitized.

When processing a Jersey GET request, do I need to filter non String types?
For example, if the parameter submitted is an integer are both option 1 (getIntData) and option 2 (getStringData) hacker safe? What about a JSON PUT request, is my ESAPI implementation enough, or do I need to validate each data parameter after it is mapped? Could it be validated before it is mapped?

Jersey Rest Example Class:

public class RestExample {

//Option 1 Submit data as an Integer
//Jersey throws an internal server error if the type is not Integer
//Is that a valid way to validate the data?

//Integer Data, not filtered
@Path("/data/int/{data}/")
@GET
@Produces(MediaType.TEXT_HTML)
public Response getIntData(@PathParam("data") Integer data){
    return Response.ok("You entered:" + data).build();  
}

//Option 2 Submit data as a String, then validate it and cast it to an Integer

//String Data, filtered
@Path("/data/string/{data}/")
@GET
@Produces(MediaType.TEXT_HTML)
public Response getStringData(@PathParam("data") String data) {
    data = ESAPI.encoder().canonicalize(data);
    if (ESAPI.validator().isValidInteger("data", data, 0, 999999, false))
    {
        int intData = Integer.parseInt(data);
        return Response.ok("You entered:" + intData).build();   
    }
    return Response.status(404).entity("404 Not Found").build();
}

//JSON data, HTML encoded
@Path("/post/{requestid}")
@POST
@Consumes({MediaType.APPLICATION_FORM_URLENCODED, MediaType.APPLICATION_JSON})
@Produces(MediaType.TEXT_HTML)
public Response postData(String json) {
    json = ESAPI.encoder().canonicalize(json);
    json = ESAPI.encoder().encodeForHTML(json);

    //Is there a way to iterate through each JSON KeyValue and filter here?

    ObjectMapper mapper = new ObjectMapper();
    DataMap dm = new DataMap();
    try {
        dm = mapper.readValue(json, DataMap.class);
    } catch (Exception e) {
        e.printStackTrace();
    } 

    //Do we need to validate each DataMap object value and is there a dynamic way to do it?
    if (ESAPI.validator().isValidInput("strData", dm.strData, "HTTPParameterValue", 25, false, true)) 
    {
        //Is Integer validation needed or will the thrown exception be good enough?
        return Response.ok("You entered:" + dm.strData + " and " + dm.intData).build();
    }
    return Response.status(404).entity("404 Not Found").build();
}
}

Data Map Class:

public class DataMap {

public DataMap(){}

String strData;
Integer intData;
}

score 5 · Accepted Answer · edited May 23 '17 at 12:29

The short answer is yes, though by "filter" I interpret it as "validate," because no amount of "filtering" will EVER provide you with SAFE data. You can still run into integer overflows in Java, and while those may not have immediate security concerns, they could still put parts of your application in an unplanned for state, and hacking is all about perturbing the system in ways you can control.

You packed waaaaay too many questions into one "question," but here we go:

First off, the lines

json = ESAPI.encoder().canonicalize(json);
json = ESAPI.encoder().encodeForHTML(json);

Aren't doing what you think they're doing. If your JSON is coming in as a raw String right here, these two calls are going to be applying mass rules across the entire string, when you really need to handle these with more surgical precision, which you seem to at least be subconsciously aware of in the next question.

//Is there a way to iterate through each JSON KeyValue and filter here?

Partial duplicate of this question.

While you're in the loop discussed here, you can perform any data transformations you want, but what you should really be considering is using the JSONObject class referenced in that first link. Then you'll have JSON parsed into an object where you'll have better access to JSON key/value pairs.

//Do we need to validate each DataMap object value and is there a dynamic way to do it?

Yes, we validate everything that comes from a user. All users are assumed to be trained hackers, and smarter than you. However if you handled filtering before you do your data mapping transformation, you don't need to do it a second time. Doing it dynamically?

Something like:

JSONObject json = new JSONObject(s);
Iterator iterator = json.keys();

while( iterator.hasNext() ){
  String data = iterator.next();
  //filter and or business logic
}

^^That syntax is skipping typechecks but it should get you where you need to go.

/Is Integer validation needed or will the thrown exception be good enough?

I don't see where you're throwing an exception with these lines of code:

if (ESAPI.validator().isValidInput("strData", dm.strData, "HTTPParameterValue", 25, false, true)) 
{
    //Is Integer validation needed or will the thrown exception be good enough?
    return Response.ok("You entered:" + dm.strData + " and " + dm.intData).build();
}

Firstly, in java we have autoboxing which means this:

int foo = 555555;
String bar = "";
//the code
foo + bar;

Will be cast to a string in any instance. The compiler will promote the int to an Integer and then silently call the Integer.toString() method. Also, in your Response.ok( String ); call, THIS is where you're going to want to encodeForHTML or whatever the output context may be. Encoding methods are ALWAYS For outputting data to user, whereas canonicalize you want to call when receiving data. Finally, in this segment of code we also have an error where you're assuming that you're dealing with an HTTPParameter. NOT at this point in the code. You'll validate http Parameters in instances where you're calling request.getParameter("id"): where id isn't a large blob of data like an entire JSON response or an entire XML response. At this point you should be validating for things like "SafeString"

Usually there are parsing libraries in Java that can at least get you to the level of Java objects, but on the validation side you're always going to be running through every item and punting whatever might be malicious.

As a final note, while coding, keep these principles in mind your code will be cleaner and your thought process much more focused:

user input is NEVER safe. (Yes, even if you've run it through an XSS filter.)
Use validate and canonicalize methods whenever RECEIVING data, and encode methods whenever transferring data to a different context, where context is defined as "Html field. Http attribute. Javascript input, etc...)
Instead of using the method isValidInput() I'd suggest using getValidInput() because it will call canonicalize for you, making you have to provide one less call.
Encode ANY time your data is going to be passed to another dynamic language, like SQL, groovy, Perl, or javascript.

Java Jersey REST Request Parameter Sanitation

1 Answers1