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Trust boundary violation

ID: java/trust-boundary-violation
Kind: path-problem
Security severity: 8.8
Severity: error
Precision: medium
Tags:
   - security
   - external/cwe/cwe-501
Query suites:
   - java-security-extended.qls
   - java-security-and-quality.qls

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A trust boundary violation occurs when a value is passed from a less trusted context to a more trusted context.

For example, a value that is generated by a less trusted source, such as a user, may be passed to a more trusted source, such as a system process. If the less trusted source is malicious, then the value may be crafted to exploit the more trusted source.

Trust boundary violations are often caused by a failure to validate input. For example, if a web application accepts a cookie from a user, then the application should validate the cookie before using it. If the cookie is not validated, then the user may be able to craft a malicious cookie that exploits the application.

Recommendation

To maintain a trust boundary, validate data from less trusted sources before use.

Example

In the first (bad) example, the server accepts a parameter from the user, then uses it to set the username without validation.

public void doGet(HttpServletRequest request, HttpServletResponse response) {
    String username = request.getParameter("username");

    // BAD: The input is written to the session without being sanitized.
    request.getSession().setAttribute("username", username);
}

In the second (good) example, the server validates the parameter from the user, then uses it to set the username.

public void doGet(HttpServletRequest request, HttpServletResponse response) {
    String username = request.getParameter("username");

    if (validator.isValidInput("HTTP parameter", username, "username", 20, false)) {
        // GOOD: The input is sanitized before being written to the session.
        request.getSession().setAttribute("username", username);
    }
}

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