Simple Script Injection |
Attack Pattern ID: 63 (Standard Attack Pattern Completeness: Complete) | Typical Severity: Very High | Status: Draft |
Summary
An attacker embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level.
An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.
Attack Execution Flow
Survey the application for user-controllable inputs:
Using a browser or an automated tool, an attacker follows all public links and actions on a web site. He records all the links, the forms, the resources accessed and all other potential entry-points for the web application.
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 in the URL.
env-Web2 Use a proxy tool to record all links visited during a manual traversal of the web application.
env-Web3 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 Inputs 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 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 parameters (POST, GET, COOKIE, etc.) is created by the attacker.2 Success A list of application user interface entry fields is created by the attacker.3 Success A list of resources accessed by the application 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.
Attack Step Techniques
ID Attack Step Technique Description Environments 1 Use a list of XSS probe strings to inject script 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-Web3 Use a list of XSS probe strings to inject script into UI entry fields. If possible, the probe strings contain a unique identifier.
env-Web4 Use a list of XSS probe strings to inject script into resources accessed by the application. If possible, the probe strings contain a unique identifier.
env-WebIndicators
ID type Indicator Description Environments 1 Positive The output of pages includes some form of a URL parameter. E.g., ?error="<foobar>'(){};=" becomes "<foobar>'(){}=" in the title of the web page.
env-Web2 Positive Input content becomes part of the 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 (not only GET, but all potential 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 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.
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 client software must be a client that allows scripting communication from remote hosts, such as a Javascript-enabled Web Browser
Description
Classic phishing attacks lure users to click on content that appears trustworthy, such as logos, and links that seem to go to their trusted financial institutions and online auction sites. But instead the attacker appends malicious scripts into the otherwise innocent appearing resources. The HTML source for a standard phishing attack looks like this
<a href="www.exampletrustedsite.com%3FName=%3Fscript%253Emaliciousscript%3F/script%253E.html">Trusted Site</a>
When the user clicks the link, the appended script also executes on the local user's machine.
Skill or Knowledge Level: Low
To achieve a redirection and use of less trusted source, an attacker can simply place a script in bulletin board, blog, wiki, or other user-generated content site that are echoed back to other client machines.
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: 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.
Malicious input delivered through standard content (containing scripts) that is sent to the user's machine, for example HTML page containing Javascript.
Varies with instantiation of attack pattern. Malicious script payload may be appended to end of legitimate looking link
Enables attacker to execute scripts to launch attacks on remote client machine and environment. Intranet and local systems may not be patched to the same degree as "externally" facing systems, so simple attacks may identify more victims on an "internal" system such as a corporate Intranet
CWE-ID | Weakness Name | Weakness Relationship Type |
---|---|---|
79 | Failure to Preserve Web Page Structure ('Cross-site Scripting') | Targeted |
20 | Improper Input Validation | Targeted |
184 | Incomplete Blacklist | Secondary |
96 | Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection') | Targeted |
113 | Failure to Sanitize CRLF Sequences in HTTP Headers ('HTTP Response Splitting') | Targeted |
348 | Use of Less Trusted Source | Targeted |
116 | Improper Encoding or Escaping of Output | Targeted |
350 | Improperly Trusted Reverse DNS | Targeted |
86 | Improper Neutralization of Invalid Characters in Identifiers in Web Pages | Secondary |
602 | Client-Side Enforcement of Server-Side Security | 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 | Attack Pattern | 242 | Script Injection | Mechanism of Attack (primary)1000 | |
ChildOf | Category | 341 | WASC Threat Classification 2.0 - WASC-08 - Cross-Site Scripting | WASC Threat Classification 2.0333 | |
ParentOf | Attack Pattern | 18 | Embedding Scripts in Nonscript Elements | Mechanism of Attack1000 | |
ParentOf | Attack Pattern | 73 | User-Controlled Filename | Mechanism of Attack1000 | |
ParentOf | Attack Pattern | 106 | Cross Site Scripting through Log Files | Script injection attack pattern is one of the components of the current attack pattern | Mechanism of Attack1000 |
Architectural Paradigms | Client-Server |
---|---|
Frameworks | J2EE .NET |
Platforms | All |
Languages | JSP Java ASP.NET ASP PHP AJAX |
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 Description | ||
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 |