Embedding Script (XSS ) in HTTP Headers |
Attack Pattern ID: 86 (Detailed Attack Pattern Completeness: Complete) | Typical Severity: Very High | Status: Draft |
Summary
An attack of this type exploits web applications that generate web content, such as links in a HTML page, based on unvalidated or improperly validated data submitted by other actors. XSS in HTTP Headers attacks target the HTTP headers which are hidden from most users and may not be validated by web applications.
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 entry points (input) that becomes part of generated HTTP header (not only GET/POST/COOKIE, but also Content-Type, etc.)
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters used in the HTTP headers.
env-Web2 Look for HTML meta tags that could be injectable
env-Web3 Use a proxy tool to record all links visited during a manual traversal of the web application.
env-Web4 Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery.
env-WebIndicators
ID type Indicator Description Environments 1 Positive Web content is generated by the application and served to the browser based on user-controllable inputs.
env-Web2 Positive HTTP header variables are used by the application or the browser (DOM)
env-Web3 Inconclusive No HTTP variables appear to be used on the current page. Even though none appear, the web application may still use them if they are provided.
env-Web4 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 HTTP variables 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.
Probe identified potential entry points for XSS vulnerability:
The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. He records all the responses from the server that include unmodified versions of his script.
The attacker tries also to inject extra-parameter to the HTTP request to see if they are reflected back in the web page or in the HTTP response.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Manually inject various script payloads into each identified entry point using a list of common script injection probes and observe system behavior to determine if script was executed.
env-Web2 Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes and observe system behavior to determine if script was executed.
env-Web3 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 User-controllable input is embedded as part of generated HTTP headers
env-Web2 Positive Input parameters become part of the web page (even in meta tags)
env-Web3 Positive Output to the browser is not encoded to remove executable scripting syntax.
env-Web4 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 (not only GET, but all in the inputs), 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.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.
Target software must be a client that allows scripting communication from remote hosts, and attacker must control a remote site of some sort to redirect client and data to.
Description
Utilize a remote style sheet set in the HTTP header for XSS attack. When the attacker is able to point to a remote stylesheet, any of the variables set in that stylesheet are controllable on the client side by the remote attacker. Like most XSS attacks, results vary depending on browser that is used.
(source:http://ha.ckers.org/xss.html)
<META HTTP-EQUIV="Link" Content="<http://ha.ckers.org/xss.css>; REL=stylesheet">
Description
Google's 404 redirection script was found vulnerable to this attack vector.
Google's 404 file not found page read
* Response headers: "Content-Type: text/html; charset=[encoding]".
* Response body: <META http-equiv="Content-Type" (...) charset=[encoding]/>
If the response sends an unexpected encoding type such as UTF-7, then no enforcement is done on the payload and arbitrary XSS code will be transported along with the standard HTTP response. Source: http://seclists.org/fulldisclosure/2005/Dec/1107.html
Description
XSS can be used in variety of ways, because it is scripted and executes in a distribtued, asynchronous fashion it can create its own vector and openings. For example, the attacker can use XSS to mount a DDoS attack by having series of different computers unknowingly executing requests against a single host.
Skill or Knowledge Level: Low
To achieve a redirection and use of less trusted source, an attacker can simply edit HTTP Headers that are sent to client machine.
Skill or Knowledge Level: High
Exploiting a client side vulnerability to inject malicious scripts into the browser's executable process.
Ability to deploy a custom hostile service for access by targeted clients. Ability to communicate synchronously or asynchronously with client machine
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.
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.
Varies with instantiation of attack pattern. In the case of HTTP headers they may not be visible to the end user via a browser
Enables attacker to execute scripts to launch attacks on server as well as remote client machine and environment
CWE-ID | Weakness Name | Weakness Relationship Type |
---|---|---|
79 | Failure to Preserve Web Page Structure ('Cross-site Scripting') | Targeted |
184 | Incomplete Blacklist | Secondary |
348 | Use of Less Trusted Source | Targeted |
96 | Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection') | Targeted |
20 | Improper Input Validation | Targeted |
116 | Improper Encoding or Escaping of Output | Targeted |
86 | Improper Neutralization of Invalid Characters in Identifiers in Web Pages | Secondary |
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 |
Vulnerability ID | Relationship Description |
---|---|
CVE-2006-5442 | ViewVC 1.0.2 and earlier does not specify a charset in its HTTP headers or HTML documents, which allows remote attackers to conduct cross-site scripting (XSS) attacks that inject arbitrary UTF-7 encoded JavaScript code via a view. |
CVE-2006-3918 | http_protocol.c in (1) IBM HTTP Server 6.0 before 6.0.2.13 and 6.1 before 6.1.0.1, and (2) Apache HTTP Server 1.3 before 1.3.35, 2.0 before 2.0.58, and 2.2 before 2.2.2, does not sanitize the Expect header from an HTTP request when it is reflected back in an error message, which might allow cross-site scripting (XSS) style attacks using web client components that can send arbitrary headers in requests, as demonstrated using a Flash SWF file. |
Nature | Type | ID | Name | Description | View(s) this relationship pertains to |
---|---|---|---|---|---|
ChildOf | Attack Pattern | 18 | Embedding Scripts in Nonscript Elements | Mechanism of Attack (primary)1000 | |
ChildOf | Attack Pattern | 220 | Client-Server Protocol Manipulation | Mechanism of Attack (primary)1000 | |
ParentOf | Attack Pattern | 107 | Cross Site Tracing | 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 | ||
Sean Barnum | Cigital, Inc | 2007-04-16 | 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 |