Prevent Server-Side Request Forgery (SSRF)

Why this matters

SSRF vulnerabilities allow attackers to manipulate server-side requests, potentially accessing internal resources or exposing sensitive data.

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    URL url = new URL(location);

    HttpURLConnection  conn = (HttpURLConnection) url.openConnection();
}

Prefer

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    List<String> allowedHosts = new ArrayList<String>();
    allowedHosts.add("https://trusted1.example.com/");
    allowedHosts.add("https://trusted2.example.com/");

    URL url = new URL(location);

    if (allowedHosts.contains(location))
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
}

More snippets

Bad

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    URL url = new URL(location);

    HttpURLConnection  conn = (HttpURLConnection) url.openConnection();
}

Good

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    List<String> allowedHosts = new ArrayList<String>();
    allowedHosts.add("https://trusted1.example.com/");
    allowedHosts.add("https://trusted2.example.com/");

    URL url = new URL(location);

    if (allowedHosts.contains(location))
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
}

Related rules

From the same buckets as this rule.

Critical

Always sanitize user inputs

Check if user inputs are sanitized before being used in rendering or database queries. Unsanitized inputs can lead to injection vulnerabilities like XSS or SQL injection.

security-hardening

Critical

Always Verify Server Certificates in SSL/TLS Connections

Ensure that SSL/TLS certificate validation is always enabled to prevent Man-in-the-Middle (MitM) attacks.

security-hardening

Critical

Avoid modifying built-in prototypes

Detect modifications to built-in prototypes. Modifying built-in objects can lead to compatibility issues and unexpected behavior. Recommend creating helper functions instead.

maintainabilitysecurity-hardening

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    URL url = new URL(location);

    HttpURLConnection  conn = (HttpURLConnection) url.openConnection();
}

Prefer

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    List<String> allowedHosts = new ArrayList<String>();
    allowedHosts.add("https://trusted1.example.com/");
    allowedHosts.add("https://trusted2.example.com/");

    URL url = new URL(location);

    if (allowedHosts.contains(location))
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
}

More snippets

Bad

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    URL url = new URL(location);

    HttpURLConnection  conn = (HttpURLConnection) url.openConnection();
}

Good

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String location = req.getParameter("url");

    List<String> allowedHosts = new ArrayList<String>();
    allowedHosts.add("https://trusted1.example.com/");
    allowedHosts.add("https://trusted2.example.com/");

    URL url = new URL(location);

    if (allowedHosts.contains(location))
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
}

Related rules

From the same buckets as this rule.

Critical

Always sanitize user inputs

Check if user inputs are sanitized before being used in rendering or database queries. Unsanitized inputs can lead to injection vulnerabilities like XSS or SQL injection.

security-hardening

Critical

Always Verify Server Certificates in SSL/TLS Connections

Ensure that SSL/TLS certificate validation is always enabled to prevent Man-in-the-Middle (MitM) attacks.

security-hardening

Critical

Avoid modifying built-in prototypes

Detect modifications to built-in prototypes. Modifying built-in objects can lead to compatibility issues and unexpected behavior. Recommend creating helper functions instead.

maintainabilitysecurity-hardening