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feat: Improve security and code quality #45

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@alexandravaron alexandravaron commented Oct 28, 2025

  • Fix null pointer vulnerability in HomeServlet by adding null checks
  • Add XSS protection by implementing HTML escaping in both servlets
  • Improve error handling with proper HTTP status codes and logging
  • Add input validation and sanitization for user inputs
  • Remove empty nested loops and TODO comments
  • Add security configuration file with recommended HTTP headers
  • Enhance session security with size limits and validation
  • Update README with security improvements documentation

These changes address common security vulnerabilities while maintaining the educational value of the demo project.

github-advanced-security[bot]
github-advanced-security bot found potential problems Oct 28, 2025
View reviewed changes
src/main/java/demo/security/servlet/HomeServlet.java Outdated
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.print("<h2>Hello "+name+ "</h2>");
out.print("<h2>Hello " + escapedName + "</h2>");

Check failure

Code scanning / SonarQube

Endpoints should not be vulnerable to reflected cross-site scripting (XSS) attacks

<!--SONAR_ISSUE_KEY:0f79bfe7-c1c3-45cd-8b64-c089c4e8d8b4-->Change this code to not reflect unsanitized user-controlled data. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=0f79bfe7-c1c3-45cd-8b64-c089c4e8d8b4&open=0f79bfe7-c1c3-45cd-8b64-c089c4e8d8b4">SonarQube</a></p>
src/main/java/demo/security/servlet/HomeServlet.java Outdated

// Add request validation
if (request.getContentLength() > 1024) {
response.sendError(HttpServletResponse.SC_REQUEST_ENTITY_TOO_LARGE,

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:fde2c3fd-3b69-40ec-9d78-d70be78901e0-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=fde2c3fd-3b69-40ec-9d78-d70be78901e0&open=fde2c3fd-3b69-40ec-9d78-d70be78901e0">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated

// Add input validation
if (user == null || user.trim().isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Username parameter is required");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:15d86e48-f70f-407d-ad1e-684abc8bdcbf-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=15d86e48-f70f-407d-ad1e-684abc8bdcbf&open=15d86e48-f70f-407d-ad1e-684abc8bdcbf">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
}

if (user.length() > MAX_USERNAME_LENGTH) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Username too long");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:05d842a9-fa74-4718-8305-9b174f2098dc-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=05d842a9-fa74-4718-8305-9b174f2098dc&open=05d842a9-fa74-4718-8305-9b174f2098dc">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
throw new RuntimeException(e);
// Log the error instead of throwing RuntimeException
System.err.println("Error retrieving users: " + e.getMessage());
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Internal server error");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:5ea2b000-33a2-4a28-a549-6c527aec5064-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=5ea2b000-33a2-4a28-a549-6c527aec5064&open=5ea2b000-33a2-4a28-a549-6c527aec5064">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
SessionHeader sessionHeader = getSessionHeader(request);
if (sessionHeader == null) return;
if (sessionHeader == null) {
response.sendError(HttpServletResponse.SC_UNAUTHORIZED, "Invalid session");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:61f01dbd-6197-4fc9-a24a-cb7030fe9b4d-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=61f01dbd-6197-4fc9-a24a-cb7030fe9b4d&open=61f01dbd-6197-4fc9-a24a-cb7030fe9b4d">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated

String user = sessionHeader.getUsername();
if (user == null || user.trim().isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid username in session");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:c6c189d5-65c7-4f63-afe5-7921cec30e17-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=c6c189d5-65c7-4f63-afe5-7921cec30e17&open=c6c189d5-65c7-4f63-afe5-7921cec30e17">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
throw new RuntimeException(e);
// Log the error instead of throwing RuntimeException
System.err.println("Error retrieving users: " + e.getMessage());
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Internal server error");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:db380efa-1ec3-455a-8ebc-93e217998601-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&branch=server-changes&issues=db380efa-1ec3-455a-8ebc-93e217998601&open=db380efa-1ec3-455a-8ebc-93e217998601">SonarQube</a></p>
@sonar-nautilus
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sonar-nautilus bot commented Oct 28, 2025 •
edited
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Quality Gate failed Quality Gate failed

Failed conditions
13 New issues
0.0% Coverage on New Code (required ≥ 80%)
18.3% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube

Catch issues before they fail your Quality Gate with our IDE extension SonarQube for IDE SonarQube for IDE

github-advanced-security[bot]
github-advanced-security bot found potential problems Oct 28, 2025
View reviewed changes
src/main/java/demo/security/servlet/HomeServlet.java Outdated
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.print("<h2>Hello "+name+ "</h2>");
out.print("<h2>Hello " + escapedName + "</h2>");

Check failure

Code scanning / SonarQube

Endpoints should not be vulnerable to reflected cross-site scripting (XSS) attacks

<!--SONAR_ISSUE_KEY:7cb987a0-f578-449f-8aa4-ba29a4bdc5d8-->Change this code to not reflect unsanitized user-controlled data. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=7cb987a0-f578-449f-8aa4-ba29a4bdc5d8&open=7cb987a0-f578-449f-8aa4-ba29a4bdc5d8">SonarQube</a></p>
src/main/java/demo/security/servlet/HomeServlet.java Outdated

// Add request validation
if (request.getContentLength() > 1024) {
response.sendError(HttpServletResponse.SC_REQUEST_ENTITY_TOO_LARGE,

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:336161c6-6519-4a2a-a1b4-43abee823382-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=336161c6-6519-4a2a-a1b4-43abee823382&open=336161c6-6519-4a2a-a1b4-43abee823382">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated

// Add input validation
if (user == null || user.trim().isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Username parameter is required");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:bfcfb5b8-bef1-4910-83b8-d6c2157e9c89-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=bfcfb5b8-bef1-4910-83b8-d6c2157e9c89&open=bfcfb5b8-bef1-4910-83b8-d6c2157e9c89">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
}

if (user.length() > MAX_USERNAME_LENGTH) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Username too long");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:3a06dcb0-50ba-4273-8bd9-6367e97236df-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=3a06dcb0-50ba-4273-8bd9-6367e97236df&open=3a06dcb0-50ba-4273-8bd9-6367e97236df">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
throw new RuntimeException(e);
// Log the error instead of throwing RuntimeException
System.err.println("Error retrieving users: " + e.getMessage());
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Internal server error");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:dfd95620-db37-4994-8bd6-ba5e5146d065-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=dfd95620-db37-4994-8bd6-ba5e5146d065&open=dfd95620-db37-4994-8bd6-ba5e5146d065">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
SessionHeader sessionHeader = getSessionHeader(request);
if (sessionHeader == null) return;
if (sessionHeader == null) {
response.sendError(HttpServletResponse.SC_UNAUTHORIZED, "Invalid session");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:dea62db1-7641-41c4-8d94-c8b5a51b1303-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=dea62db1-7641-41c4-8d94-c8b5a51b1303&open=dea62db1-7641-41c4-8d94-c8b5a51b1303">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated

String user = sessionHeader.getUsername();
if (user == null || user.trim().isEmpty()) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid username in session");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:8fa074ab-5319-41b6-98b1-229b43fd59c3-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=8fa074ab-5319-41b6-98b1-229b43fd59c3&open=8fa074ab-5319-41b6-98b1-229b43fd59c3">SonarQube</a></p>
src/main/java/demo/security/servlet/UserServlet.java Outdated
throw new RuntimeException(e);
// Log the error instead of throwing RuntimeException
System.err.println("Error retrieving users: " + e.getMessage());
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Internal server error");

Check notice

Code scanning / SonarQube

Exceptions should not be thrown from servlet methods

<!--SONAR_ISSUE_KEY:97d742e1-a3fc-4ac5-b8ad-bebce699c2c4-->Handle the following exception that could be thrown by "sendError": IOException. <p>See more on <a href="https://nautilus.sonarqube.org/project/issues?id=demo%3Ajava-security&pullRequest=45&issues=97d742e1-a3fc-4ac5-b8ad-bebce699c2c4&open=97d742e1-a3fc-4ac5-b8ad-bebce699c2c4">SonarQube</a></p>
feat: Add comprehensive SonarQube demo issues
50a3f5a 
- Add SQL injection vulnerabilities with taint analysis examples
- Include XSS vulnerabilities with unescaped user input
- Add path traversal and command injection issues
- Include security hotspots (hardcoded passwords, weak crypto)
- Add code quality issues (dead code, duplicated code, magic numbers)
- Create complex data flow examples for taint analysis demos
- Add deserialization vulnerabilities and information disclosure
- Include performance issues and code smells
- Update README with comprehensive demo guide for sales engineers

Perfect for demonstrating SonarQube's comprehensive analysis capabilities
including taint analysis, security hotspots, and code quality metrics.
refactor: Remove verbose comments and simplify README
359ad68 
- Remove all SonarQube issue comments from servlet files
- Simplify README to basic usage instructions
- Keep vulnerabilities intact for demo purposes
- Clean up code for better readability
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@alexandravaron