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| // webapps/<web-app-name>/WEB-INF/classes/CSPPoliciesApplier.java
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.List;
/* for Tomcat 9 and below
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
*/
import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.FilterConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.annotation.WebFilter;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.apache.commons.codec.binary.Hex;
/**
* Sample filter implementation to define a set of Content Security Policies.<br/>
* This implementation has a dependency on Commons Codec API.<br/>
* This filter set CSP policies using all HTTP headers defined into W3C specification.<br/>
* <br/>
* This implementation is oriented to be easily understandable and easily adapted.<br/>
*/
@WebFilter("/*")
public class CSPPoliciesApplier implements Filter {
/** Configuration member to specify if web app use web fonts */
public static final boolean APP_USE_WEBFONTS = false;
/** Configuration member to specify if web app use videos or audios */
public static final boolean APP_USE_AUDIOS_OR_VIDEOS = false;
/**
* Configuration member to specify if filter must add CSP directive used by Mozilla (Firefox)
*/
public static final boolean INCLUDE_MOZILLA_CSP_DIRECTIVES = false;
/** Filter configuration */
@SuppressWarnings("unused")
private FilterConfig filterConfig = null;
/** List CSP HTTP Headers */
private List<String> cspHeaders = new ArrayList<String>();
/** Collection of CSP polcies that will be applied */
private String policies = null;
/** Used for Script Nonce */
private SecureRandom prng = null;
/**
* Used to prepare (one time for all) set of CSP policies that will be applied on each HTTP
* response.
*
* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
*/
@Override
public void init(FilterConfig fConfig) throws ServletException {
// Get filter configuration
this.filterConfig = fConfig;
// Init secure random
try {
this.prng = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
throw new ServletException(e);
}
// Define list of CSP HTTP Headers
this.cspHeaders.add("Content-Security-Policy");
// this.cspHeaders.add("X-Content-Security-Policy");
// this.cspHeaders.add("X-WebKit-CSP");
// Define CSP policies
// Loading policies for Frame and Sandboxing will be dynamically defined : We need to know if context use Frame
List<String> cspPolicies = new ArrayList<String>();
String originLocationRef = "'self'";
// --Disable default source in order to avoid browser fallback loading using 'default-src'
// locations
cspPolicies.add("default-src 'none'");
// --Define loading policies for Scripts
// cspPolicies.add("script-src " + originLocationRef + " 'unsafe-inline' 'unsafe-eval'"); <- bad policy!
cspPolicies.add("script-src " + originLocationRef); // not the best but will do
if (INCLUDE_MOZILLA_CSP_DIRECTIVES) {
cspPolicies.add("options inline-script eval-script");
cspPolicies.add("xhr-src 'self'");
}
// --Define loading policies for Plugins
cspPolicies.add("object-src " + originLocationRef);
// --Define loading policies for Styles (CSS)
cspPolicies.add("style-src " + "'unsafe-inline'");
// --Define loading policies for Images
cspPolicies.add("img-src " + originLocationRef);
// --Define loading policies for Form
cspPolicies.add("form-action " + originLocationRef);
// --Define loading policies for Audios/Videos
if (APP_USE_AUDIOS_OR_VIDEOS) {
cspPolicies.add("media-src " + originLocationRef);
}
// --Define loading policies for Fonts
if (APP_USE_WEBFONTS) {
cspPolicies.add("font-src " + originLocationRef);
}
// --Define loading policies for Connection
cspPolicies.add("connect-src " + originLocationRef);
// --Define loading policies for Plugins Types
// cspPolicies.add("plugin-types application/pdf application/x-shockwave-flash");
// --Define browser XSS filtering feature running mode
// cspPolicies.add("reflected-xss block");
// Target formating
this.policies = cspPolicies.toString().replaceAll("(\\[|\\])", "").replaceAll(",", ";")
.trim();
}
/**
* Add CSP policies on each HTTP response.
*
* @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest,
* javax.servlet.ServletResponse, javax.servlet.FilterChain)
*/
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain fchain)
throws IOException, ServletException {
HttpServletRequest httpRequest = ((HttpServletRequest) request);
HttpServletResponse httpResponse = ((HttpServletResponse) response);
/* Step 1 : Detect if target resource is a Frame */
// Customize here according to your context...
boolean isFrame = false;
/* Step 2 : Add CSP policies to HTTP response */
StringBuilder policiesBuffer = new StringBuilder(this.policies);
// If resource is a frame add Frame/Sandbox CSP policy
if (isFrame) {
// Frame + Sandbox : Here sandbox allow nothing, customize sandbox options depending on
// your app....
policiesBuffer.append(";").append("frame-src 'self';sandbox");
if (INCLUDE_MOZILLA_CSP_DIRECTIVES) {
policiesBuffer.append(";").append("frame-ancestors 'self'");
}
}
/*
// Add Script Nonce CSP Policy
// --Generate a random number
String randomNum = new Integer(this.prng.nextInt()).toString();
// --Get its digest
MessageDigest sha;
try {
sha = MessageDigest.getInstance("SHA-1");
} catch (NoSuchAlgorithmException e) {
throw new ServletException(e);
}
byte[] digest = sha.digest(randomNum.getBytes());
// --Encode it into HEXA
String scriptNonce = Hex.encodeHexString(digest);
policiesBuffer.append(";").append("script-nonce ").append(scriptNonce);
// --Made available script nonce in view app layer
httpRequest.setAttribute("CSP_SCRIPT_NONCE", scriptNonce);
*/
// Add policies to all HTTP headers
for (String header : this.cspHeaders) {
httpResponse.setHeader(header, policiesBuffer.toString());
}
/* Step 3 : Let request continue chain filter */
fchain.doFilter(request, response);
}
/**
* {@inheritDoc}
*
* @see javax.servlet.Filter#destroy()
*/
@Override
public void destroy() {
// Not used
}
}
|
Not Vulnerable
