GM_xmlhttpRequest bug when adding function to Object.prototype

[chris0385]

If you add a function to Object.prototype, GM_xmlhttpRequest doesn't work any more.

So the script below don't work and throw : "Erreur : uncaught exception: unknown (can't convert to string)"

// ----------------------------------------------------------------

GM_xmlhttpRequest({
method: 'GET',
url: 'http://greaseblog.blogspot.com/atom.xml',
headers: {
'User-agent': 'Mozilla/4.0 (compatible) Greasemonkey',
'Accept': 'application/atom+xml,application/xml,text/xml',
},
onload: function(responseDetails) {
alert('Request for Atom feed returned ' + responseDetails.status +
' ' + responseDetails.statusText + '\n\n' +
'Feed data:\n' + responseDetails.responseText);
}
});

/**
Erreur : uncaught exception: unknown (can't convert to string)

That was thrown while running the GM_xmlhttpRequest just above.
*/
Object.prototype.anyFunctionName=function(str) { } // BUG

//Object.prototype.x=1; // variables work

// ----------------------------------------------------------------

I Use :
Greasemonkey version : 0.8.20091209.4
Mozilla/5.0 (X11; U; Linux i686; fr; rv:1.9.0.15) Gecko/2009102814 Ubuntu/8.04 (hardy) Firefox/3.0.15

[arantius]

Cannot reproduce on GM 0.8.20100211.5

Test script:

Object.prototype.AnyNameHere = function(x) {}

GM_xmlhttpRequest({
    method: "GET",
    url: "http://www.example.net/",
    onload: function(responseDetails) {
      alert('Request returned ' + responseDetails.status +
            ' ' + responseDetails.statusText + '\n\n' +
            'Data:\n' + responseDetails.responseText);
    }
});

Works as expected.

[erikvold]

arantius: It might have to do with the object literal that is used in the example chris0385 provided. I assume that the object literal is parsed for it's properties and all the properties are used in the header; so the error must occur because one property is a function (ie: a method).

If this is the case then one way to correct this bug would be to test that the property is not a method before attempting to use it.

[erikvold]

the headers object literal that is..

[Ventero]

Yeah, I can confirm that the function-property of the headers-object is causing this problem. The relevant code is L74-L78 in content/xmlhttprequest.js.

As erikvold said, a possible fix is to check if the property is a function.

Additionally it might be a good idea to throw a

if(details.headers.hasOwnProperty(prop))

in there.

Edit: Actually not functions itself cause the problem, but multi-line strings.
For example,

Object.prototype.foo = "foo\nbar;

GM_xmlhttpRequest({method: 'GET', url: 'http://github.com/', headers: {}});

throws the same exception (which is
"Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIXMLHttpRequest.setRequestHeader]" for reference).
The reason why it throws the same error for functions is, that a function's toString() always returns a multi-line string. So checking the typeof for each property definitely isn't enough.

[erikvold]

Nice work Ventero!

I took a look at yui and using the hasOwnProperty() method seems to be what they use as well. I also did some reading on it and it does appear to be the correct method to use.

So I created a branch from the greasemonkey/master branch called issue-1065 and made the change here

I also tested this change with this userscript and it works.

[arantius]

commit 6000de1