Computer

  
Cross-site scripting (XSS) Aggressions
Cross-site scripting (XSS) is a sign of defencelessness regularly build in edifice contacts. This defencelessness moulds it feasible restraint aggressioners to inject vindictive mode (e.g. JavaScript programs) into sufferer’s edifice browser.
Using this vindictive mode, the aggressioners can peculate the sufferer’s credentials, such as cookies. The entrance govern policies (i.e., the selfselfsame camanifestation plan) industrious by the browser to preserve those credentials can be bypassed by acting the XSS defencelessness. Vulnerabilities of this peel can theoretically bring to large-scale aggressions.
To evidence what aggressioners can do by acting XSS vulnerabilities, we own be up a edifice contact determined Elgg in our pre-built Ubuntu VM fiction. Elgg is an unconcealed-source edifice contact restraint political networking, and it has implemented a estimate of countermeasures to redress the XSS denunciation. To evidence how XSS aggressions composition, we own commented quenched these countermeasures in Elgg in our installation, intentionally making Elgg delicate to XSS aggressions. Withquenched the countermeasures, manifestationrs can shaft any harsh referable attributable attributableice, including JavaScript programs, to the manifestationr marks. In this lab, students insufficiency to act this defencelessness to propel an XSS aggression on the qualified Elgg, in a fashion that is harmonious to what Samy Kamkar did to MyIntervenience in 2005 through the known Samy hint. The conclusive sight of this aggression is to ramify an XSS hint unmoulded the manifestationrs, such that whoever apprehensions an rotten manifestationr prosmooth conciliate be rotten, and whoever is rotten conciliate gather you (i.e., the aggressioner) to his/her confidant catalogue.
Environment beup restraint the drift:
Restraint this drift, we conciliate wear that you own be up the Ubuntu implicit means environment naturalized on the instructions in the Syllabus beneath “Special Software Installation Exactments”.
We conciliate insufficiency the coercionthcoming: 

Firefox edifice browser 
Apache edifice server
Elgg edifice contact

Restraint the Firefox browser, we insufficiency to manifestation the LiveHTTPHeaders production restraint Firefox to overhaul the HTTP entreats and responses (adapted beneath the “Tools” menu in Firefox). The pre-built Ubuntu VM fiction granted to you has already domiciled the Firefox edifice browser with the exactd production. 
The Apache edifice server is too interposed in the pre-built Ubuntu fiction. However, the edifice server is referable attributable attributable attributable launched by lapse. You own to chief initiate the edifice server using individual of the coercionthcoming couple commands:
% sudo apache2ctl initiate 
or 
% sudo portraiture apache2 initiate
The Elgg edifice contact is already be up in the pre-built Ubuntu VM fiction. We own too created be-unlikeent manifestationr accounts on the Elgg server and the credentials are abandoned adown (username, password):
admin, seedelgg
alice, seedalice
boby, seedboby
charlie, seedcharlie
samy, seedsamy
You can entrance the Elgg server using the coercionthcoming URL (the Apache server insufficiencys to be launched chief):
http://www.xsslabelgg.com
(this URL is barely entranceible from within of the implicit means, becamanifestation we own qualified the /etc/hosts smooth to map the territory cintegral (www.xsslabelgg.com) to the implicit means’s persomal IP gatherress 127.0.0.1).
Once you log in as a manifestationr in Elgg, you can entrance your Prosmooth and catalogue of Confidants by clicking on icons in the remarkable left divorce of the browser window.
Note: Some of the plan labors exact some basic disrespect with JavaScript. Wherever compulsory,
we yield a exemplification JavaScript program to acceleration you object launched 

  
Writing an XSS Hint
In this and proximate labor, we conciliate execute an aggression harmonious to what Samy did to MyIntervenience in 2005 (i.e., the Samy
Worm). Chief, we conciliate transcribe an XSS hint that does referable attributable attributable attributable self-propagate; in the proximate labor, we conciliate mould it
self-propagating. From the anterior labor, we own read how to peculate the cookies from the sufferer.
In this labor, we insufficiency to transcribe a vindictive JavaScript to restraintge a HTTP entreat instantly from the sufferer’s browser. This aggression does referable attributable attributable attributable exact the mediation from the aggressioner. The JavaScript that can object this is calld a cross-site scripting hint. 
This labor consists of couple fractions sub-tasks.

i: XSS Hint that gathers a confidant
The concrete of the aggression in this sublabor is to disagree the sufferer’s prosmooth and gather Samy as a confidant of the sufferer. To gather a confidant restraint the sufferer, we should chief perceive quenched how a integralowable manifestationr gathers a confidant in Elgg.
More specifically, we insufficiency to statue quenched what is sent to the server when a manifestationr gathers a confidant. Firefox’s
LiveHTTPHeaders production can acceleration us (adapted beneath the “Tools” menu in Firefox); it can ostentation the header and divergency of any HTTP entreat referable attributable attributableice sent from the browser. From this, we can confirm integral the parameters in the entreat.
There are couple low signs of HTTP entreats, individual is HTTP GET entreat, and the other is HTTP POST entreat. These couple signs of HTTP entreats be-unlove in how they bestow the divergency of the entreat to the server. We can manifestation the JavaScript XMLHttpEntreat appearance to bestow HTTP GET and POST entreats to edifice contacts. XMLHttpEntreat can barely bestow HTTP entreats object to the server, instead of other computers, becamanifestation the selfsame-camanifestation plan is strongly enforced restraint XMLHttpRequest. This is referable attributable attributable attributable an conclusion restraint us, becamanifestation we do absence to manifestation XMLHttpEntreat to bestow a restraintged HTTP entreat object to the Elgg server.
To gather how to manifestation XMLHttpRequest, you can consider these muniments:
https://www.w3schools.com/xml/ajax_xmlhttprequest_create.asp
https://www.w3schools.com/xml/xml_http.asp
https://developer.mozilla.org/en-US/docs/AJAX/Getting_Started
https://www.tutorialspoint.com/ajax/what_is_xmlhttprequest.htm
If you are referable attributable attributable attributable household with JavaScript programming, we hint that you consider the coercionthcoming muniments to gather some basic JavaScript functions. You conciliate own to manifestation some of these functions.
Essential Javascript – A Javascript Tutorial: 
https://www.evl.uic.edu/luc/bvis546/Essential_Javascript_–_A_Javascript_Tutorial.pdf
You may too insufficiency to debug your JavaScript mode. Firebug is a Firefox production that accelerations you debug JavaScript mode. It can subject-matter you to the punctilious places that comprise errors. FireBug is already domiciled in Firefox in our pre-built Ubuntu VM fiction (adapted beneath the “Tools” menu in Firefox).
Restraint this subtask, the hint program should do the coercionthcoming:
1. Create the emobject entreat to gather Samy to the confidants catalogue of the manifestationr who is executing the vindictive mode
2. Restraintge a HTTP GET entreat to gather Samy as a confidant.

Mode Skeleton. We yield a skeleton of the JavaScript mode that you insufficiency to transcribe. This JavaScript mode is inserted into manifestationr Samy’s mark, and any manifestationr that apprehensions Samy’s prosmooth conciliate then unimpassionedally gather Samy as their confidant. You insufficiency to increase in integral the compulsory details. When you emcollection the conclusive JavaScript mode in the referable attributable attributableice shafted to Samy’s mark, you insufficiency to suppress integral the comments, extra intervenience, and new-line characters.
  
<script id=”worm”   type=”text/javascript”>
var Ajax=null;
//Construct the HTTP entreat to gather   Samy as a confidant.
var bestowurl=”…”;
//Create and bestow Ajax entreat to gather   friend.
// The restraintmat of the entreat can be   read from LiveHttpHeaders.
Ajax=new XMLHttpRequest();
Ajax.open(“GET”,sendurl,true);
Ajax.setRequestHeader(“Host”,”www.xsslabelgg.com”);
Ajax.setRequestHeader(“Keep-Alive”,”300″);
Ajax.setRequestHeader(“Connection”,”keep-alive”);
// (JavaScript mode to entrance synod   cookie)
Ajax.setRequestHeader(“Cookie”,document.cookie);
Ajax.setRequestHeader(“Content-Type”,”application/x-www-form-urlencoded”);
Ajax.send();
</script>
Note that in this condition the GET rule is manifestationd to bestow the HTTP entreat.
To disagree the sufferer’s mark, the HTTP entreat sent by the hint should comprise the sufferer’s __elgg_ts and __elgg_token values in the bestowurl inconstant. These details are give in the edifice page (right-click and “Apprehension Page Source”) and the hint insufficiencys to perceive quenched and manifestation this knowledge using JavaScript mode. The bestowurl inconstant should too comprise Samy’s id.

What you insufficiency to do: 
1. Naturalized on the restraintmat of the GET entreat to gather a confidant, transcribe a JavaScript script that gathers Samy to the confidants catalogue of any manifestationr who apprehensions Samy’s mark. Save your JavaScript script in a smooth labor4-1.txt.
2. Login as manifestationr Samy and inject in the “Abquenched me” scope of Samy’s prosmooth the script from smooth labor4-1.txt. (Mould gentleman to picked “Suppress editor” precedently editing this scope, in arrange to disentitle any unimpassioned restraintmatting)
3. Logquenched and login as manifestationr Alice, and then apprehension Samy’s prosmooth by pickeding manifestationr Samy from “More => Components” in the Elgg menu. At this subject-matter, the vindictive Javascript script conciliate be effected and Samy conciliate be gathered to Alice’s confidant catalogue.
4. Emcollection in your plan muniment: 
a. a palliate printquenched with Alice’s confidants catalogue succeeding apprehensioning Samy’s mark.
b. a printquenched of your JavaScript smooth labor4-1.txt.

  
ii. XSS Hint that varys the sufferer’s mark
The concrete of the aggression in this sublabor is to disagree the sufferer’s prosmooth “Abquenched me” scope to profession the citation “Samy is my HERO”. To do this, we should chief perceive quenched how a integralowable prosmooth vary looks love in Elgg. More specifically, we insufficiency to statue quenched what is sent to the server when a manifestationr varys the “Abquenched me” scope and saves her mark. Firefox’s LiveHTTPHeaders production can acceleration us (adapted beneath the “Tools” menu in Firefox); it can ostentation the header and divergency of any HTTP entreat referable attributable attributableice sent from the browser. From this, we can confirm integral the insufficiencyed postulates in the entreat.
Restraint this subtask, the hint program should do the coercionthcoming:
1. Create the emobject entreat to gather a gentleman ingredient of citation into the prosmooth of a manifestationr (the sufferer) who is apprehensioning Samy’s mark
2. Restraintge a HTTP POST entreat to vary the prosmooth of the sufferer manifestationr.

Mode Skeleton. We yield a skeleton of the JavaScript mode that you insufficiency to transcribe. This JavaScript mode is inserted into manifestationr Samy’s mark, and any manifestationr that apprehensions Samy’s prosmooth conciliate then unimpassionedally own their “Abquenched me” prosmooth scope varyd to a gentleman ingredient of citation. You insufficiency to increase in integral the compulsory details. When you emcollection the conclusive JavaScript mode in the referable attributable attributableice shafted to Samy’s mark, you insufficiency to suppress integral the comments, extra intervenience, and new-line characters.
  
<script id=”worm”   type=”text/javascript”>
var Ajax=null;
//Construct the HTTP POST entreat to   disagree mark.
var bestowurl=”… “;
var full= “…”;
//Disagree Sufferer’s prosmooth bar restraint   SAMY
if(…)
{
//Create   and bestow Ajax entreat to disagree mark
Ajax=null;
Ajax=new   XMLHttpRequest();
Ajax.open(“POST”,sendurl,true);
Ajax.setRequestHeader(“Host”,”www.xsslabelgg.com”);
Ajax.setRequestHeader(“Keep-Alive”,”300″);
Ajax.setRequestHeader(“Connection”,”keep-alive”);
//   JavaScript mode to entrance synod cookie
Ajax.setRequestHeader(“Cookie”,document.cookie);
Ajax.setRequestHeader(“Content-Type”,”application/x-www-form-urlencoded”);
Ajax.send(content);
}
</script>
Note that in this condition the POST rule is manifestationd to bestow the HTTP entreat.
To disagree the sufferer’s mark, the HTTP entreat sent by the hint should comprise gentleman knowledge abquenched the sufferer in the HTML collection of the entreat (which is sent via the full inconstant):
· The __elgg_ts and __elgg_token values are give in the edifice page (right-click and “Apprehension Page Source”) and the hint insufficiencys to perceive quenched and manifestation this knowledge using JavaScript mode.
· The sufferer’s manifestationr cintegral can be obtained using elgg.session.user.name
· The sufferer’s id (guid) can be obtained using elgg.session.user.guid
Important referable attributable attributablee: Be regardful when intercourse with an rotten mark. If a prosmooth is already rotten by the XSS hint, you may absence to permission them peculiar, instead of disagreeing them intermittently. If you are referable attributable attributable attributable regardful, you may object up removing the XSS hint from the mark.

What you insufficiency to do: 
1. Naturalized on the restraintmat of the POST entreat to vary a manifestationr’s mark, transcribe a JavaScript script that varys the “Abquenched me” scope in the prosmooth of any manifestationr (the sufferer) who apprehensions Samy’s mark. The “Abquenched me” scope should comprise the coercionthcoming citation: 
Samy is my HERO (adventitious by <insert your team component call/s here>
Save your JavaScript script in a smooth labor4-2.txt.
2. Login as manifestationr Samy and inject in the “Abquenched me” scope of Samy’s prosmooth the script from smooth labor4-2.txt. (Mould gentleman to picked “Suppress editor” precedently editing this scope, in arrange to disentitle any unimpassioned restraintmatting)
3. Logquenched and login as manifestationr Alice, and then apprehension Samy’s prosmooth by pickeding manifestationr Samy from “More => Components” in the Elgg menu. At this subject-matter, the vindictive Javascript script conciliate be effected and Alice’s prosmooth conciliate be varyd.
4. Emcollection in your plan muniment: 
a. a palliate printquenched with Alice’s prosmooth succeeding apprehensioning Samy’s mark.
b. a printquenched of your JavaScript smooth labor4-2.txt. 

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