External Control of File Name or Path

The software allows user input to control or influence paths or file names that are used in filesystem operations.


Description

This could allow an attacker to access or modify system files or other files that are critical to the application.

Path manipulation errors occur when the following two conditions are met:

An attacker can specify a path used in an operation on the filesystem.

By specifying the resource, the attacker gains a capability that would not otherwise be permitted.

For example, the program may give the attacker the ability to overwrite the specified file or run with a configuration controlled by the attacker.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files (CWE-22).

String rName = request.getParameter("reportName");
File rFile = new File("/usr/local/apfr/reports/" + rName);
...
rFile.delete();

Example Two

The following code uses input from a configuration file to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can change the configuration file, they can use the program to read any file on the system that ends with the extension .txt.

fis = new FileInputStream(cfg.getProperty("sub")+".txt");
amt = fis.read(arr);
out.println(arr);

See Also

Limit Access

Weaknesses in this category are related to the design and architecture of system resources. Frequently these deal with restricting the amount of resources that are acc...

SFP Secondary Cluster: Path Traversal

This category identifies Software Fault Patterns (SFPs) within the Path Traversal cluster (SFP16).

CERT C++ Secure Coding Section 09 - Input Output (FIO)

Weaknesses in this category are related to rules in the Input Output (FIO) section of the CERT C++ Secure Coding Standard. Since not all rules map to specific weakness...

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.

Weaknesses Introduced During Design

This view (slice) lists weaknesses that can be introduced during design.


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