Embedding Scripts in HTTP Query Strings |
Attack Pattern ID: 32 (Detailed Attack Pattern Completeness: Complete) | Typical Severity: High | Status: Draft |
Summary
A variant of cross-site scripting called "reflected" cross-site scripting, the HTTP Query Strings attack consists of passing a malicious script inside an otherwise valid HTTP request query string. This is of significant concern for sites that rely on dynamic, user-generated content such as bulletin boards, news sites, blogs, and web enabled administration GUIs. The malicious script may steal session data, browse history, probe files, or otherwise execute attacks on the client side. Once the attacker has prepared the malicious HTTP query it is sent to a victim user (perhaps by email, IM, or posted on an online forum), who clicks on a normal looking link that contains a poison query string. This technique can be made more effective through the use of services like http://tinyurl.com/, which makes very small URLs that will redirect to very large, complex ones. The victim will not know what he is really clicking on.
Attack Execution Flow
Spider:
Using a browser or an automated tool, an attacker follows all public links on a web site. He records all the links he finds.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Use a spidering tool to follow and record all links. Make special note of any links that include parameters in the URL.
env-Web2 Use a proxy tool to record all links visited during a manual traversal of the web application. Make special note of any links that include parameters in the URL. Manual traversal of this type is frequently necessary to identify forms that are GET method forms rather than POST forms.
env-Web3 Use a browser to manually explore the website and analyze how it is constructed. Many browser's plugins are available to facilitate the analysis or automate the URL discovery.
env-WebIndicators
ID type Indicator Description Environments 1 Positive URL parameters are used by the application or the browser (DOM)
env-Web2 Inconclusive Using URL rewriting, parameters may be part of the URL path.
env-Web3 Inconclusive No parameters appear on the URL. Even though none appear, the web application may still use them if they are provided.
env-Web4 Inconclusive Application could use POST variable as GET inside the application. Therefore, looking for POST parameters and adding them to the query string.
env-Web5 Negative Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible.
env-WebOutcomes
ID type Outcome Description 1 Success A list of URLs, with their corresponding parameters is created by the attacker.Security Controls
ID type Security Control Description 1 Detective Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them).2 Detective Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application.3 Preventative Use CAPTCHA to prevent the use of the application by an automated tool.4 Preventative Actively monitor the application and either deny or redirect requests from origins that appear to be automated.
Attempt variations on input parameters:
Possibly using an automated tool, an attacker requests variations on the URLs he spidered before. He sends parameters that include variations of payloads. He records all the responses from the server that include unmodified versions of his script.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Use a list of XSS probe strings to inject in parameters of known URLs. If possible, the probe strings contain a unique identifier.
env-Web2 Use a proxy tool to record results of manual input of XSS probes in known URLs.
env-WebIndicators
ID type Indicator Description Environments 1 Positive The output of pages includes some form of a URL parameter. E.g., ?error="File not Found" becomes "File not Found" in the title of the web page.
env-Web2 Positive Input parameters become part of JavaScript, VBScript, or other script in a web page.
env-Web3 Inconclusive Nothing is returned to the web page. It may be a stored XSS. The unique identifier from the probe helps to trace the flow of the possible XSS.
env-WebOutcomes
ID type Outcome Description 1 Success The attacker's cross-site scripting string is repeated back verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, script, etc.)2 Failure All HTML-sensitive characters are consistently re-encoded before being sent to the web browser.3 Inconclusive Some sensitive characters are consistently encoded, but others are not.Security Controls
ID type Security Control Description 1 Detective Monitor input to web servers, application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use.2 Preventative Apply appropriate input validation to filter all user-controllable input of scripting syntax3 Preventative Do not embed user-controllable input generated HTTP headers4 Preventative Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes.
Steal session IDs, credentials, page content, etc.:
As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker.
env-Web2 Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately.
env-WebOutcomes
ID type Outcome Description 1 Success The attacker gets the user's cookies or other session identifiers.2 Success The attacker gets the content of the page the user is viewing.3 Success The attacker causes the user's browser to visit a page with malicious content.Security Controls
ID type Security Control Description 1 Detective Monitor server logs for scripting parameters.2 Detective Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate.3 Preventative Apply appropriate input validation to filter all user-controllable input of scripting syntax4 Preventative Appropriately encode all browser output to avoid scripting syntax5 Preventative Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes.Forceful browsing:
When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not).
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site
env-Web2 Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities).
env-WebOutcomes
ID type Outcome Description 1 Success The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF.2 Success The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of.Security Controls
ID type Security Control Description 1 Detective Monitor server logs for scripting parameters.2 Detective Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate.3 Preventative Apply appropriate input validation to filter all user-controllable input of scripting syntax4 Preventative Appropriately encode all browser output to avoid scripting syntax5 Preventative Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes.Content spoofing:
By manipulating the content, the attacker targets the information that the user would like to get from the website.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page.
env-WebOutcomes
ID type Outcome Description 1 Success The user sees a page containing wrong informationSecurity Controls
ID type Security Control Description 1 Detective Monitor server logs for scripting parameters.1 Detective Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate.2 Preventative Apply appropriate input validation to filter all user-controllable input of scripting syntax3 Preventative Appropriately encode all browser output to avoid scripting syntax4 Preventative Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes.
Target client software must allow scripting such as Javascript. Server software must allow display of remote generated HTML without sufficient input or output validation.
Description
http://user:host@example.com:8080/oradb<script>alert('Hi')</script>
Description
Web applications that accept name value pairs in a HTTP Query string are inherently at risk to any value (or name for that matter) that an attacker would like to enter in the query string. This can be done manually via web browser or trivially scripted to post the query string to multiple sites. In the latter case, in the instance of many sites using similar infrastructure with predictable http queries being accepted and operated on (such as blogging software, Google applications, and so on), a single malicious payload can be scritped to target a wide variety of sites.
Web 2.0 type sites like Technorati and del.icio.us rely on user generated content like tags to build http links that are displayed to other users. del.icio.us allows users to identify sites, tag them with metadata and provide URL, descriptions and more data. This data is then echoed back to any other web browser that is interested in the link. If the data is not validated by the del.icio.us site properly then an abritrary code can be added into the standard http string sent to del.icio.us by the attacker, for example formatted as normal content with a URL and description and tagged as Java, and available to be clicked on (and executed by) any user browsing for Java content that clicks on this trojaned content.
Skill or Knowledge Level: Low
To place malicious payload on server via HTTP
Skill or Knowledge Level: High
Exploiting any information gathered by HTTP Query on script host
Design: Use browser technologies that do not allow client side scripting.
Design: Utilize strict type, character, and encoding enforcement
Design: Server side developers should not proxy content via XHR or other means, if a http proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from.
Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification.
Implementation: Perform input validation for all remote content, including remote and user-generated content
Implementation: Perform output validation for all remote content.
Implementation: Disable scripting languages such as Javascript in browser
Implementation: Session tokens for specific host
Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this.
Implementation: Privileges are constrained, if a script is loaded, ensure system runs in chroot jail or other limited authority mode
Script delivered through standard web server, such as a web server with user-generated content.
Client web browser may be used to steal session data, passwords, cookies, and other tokens.
CWE-ID | Weakness Name | Weakness Relationship Type |
---|---|---|
79 | Failure to Preserve Web Page Structure ('Cross-site Scripting') | Targeted |
84 | Failure to Resolve Encoded URI Schemes in a Web Page | Targeted |
85 | Doubled Character XSS Manipulations | Targeted |
20 | Improper Input Validation | Targeted |
86 | Improper Neutralization of Invalid Characters in Identifiers in Web Pages | Targeted |
692 | Incomplete Blacklist to Cross-Site Scripting | Targeted |
697 | Insufficient Comparison | Targeted |
713 | OWASP Top Ten 2007 Category A2 - Injection Flaws | Targeted |
71 | Apple '.DS_Store' | Targeted |
Nature | Type | ID | Name | Description | View(s) this relationship pertains to![]() |
---|---|---|---|---|---|
ChildOf | ![]() | 18 | Embedding Scripts in Nonscript Elements | Mechanism of Attack (primary)1000 | |
ChildOf | ![]() | 220 | Client-Server Protocol Manipulation | Mechanism of Attack (primary)1000 |
Submissions | ||||
---|---|---|---|---|
Submitter | Organization | Date | ||
G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. | Cigital, Inc | 2007-01-01 |
Modifications | |||||
---|---|---|---|---|---|
Modifier | Organization | Date | Comments | ||
Gunnar Peterson | Cigital, Inc | 2007-02-28 | Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" | ||
Sean Barnum | Cigital, Inc | 2007-03-09 | Review and revise | ||
Richard Struse | VOXEM, Inc | 2007-03-26 | Review and feedback leading to changes in Name and Examples | ||
Sean Barnum | Cigital, Inc | 2007-04-13 | Modified pattern content according to review and feedback | ||
Romain Gaucher | Cigital, Inc | 2009-02-10 | Created draft content for detailed description | ||
Sean Barnum | Cigital Federal, Inc | 2009-04-13 | Reviewed and revised content for detailed description |