jodd.servlet.CsrfShield Maven / Gradle / Ivy
// Copyright (c) 2003-2011, Jodd Team (jodd.org). All Rights Reserved.
package jodd.servlet;
import jodd.util.RandomStringUtil;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.PageContext;
import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;
import java.io.Serializable;
/**
* Shields against CSRF attacks.
*/
public class CsrfShield {
public static final String CSRF_TOKEN_NAME = "_csrf_token";
public static final String CSRF_TOKEN_SET = "_csrf_token_set";
protected static int timeToLive = 600;
protected static int maxTokensPerSession = 20;
/**
* Sets time to live for tokens in seconds.
* By setting negative value or 0 token leaves forever.
*/
public static void setTimeToLive(int periodInSeconds) {
timeToLive = periodInSeconds;
}
/**
* Sets max number of tokens that will be stored for single session.
* It is actually the number of CSRF validation that may occur in the
* same time. Limit prevents from malicious growing of the set.
*/
public static void setMaxTokensPerSession(int maxTokensPerSession) {
CsrfShield.maxTokensPerSession = maxTokensPerSession;
}
// ---------------------------------------------------------------- prepare
/**
* @see #prepareCsrfToken(javax.servlet.http.HttpSession, int)
*/
public static String prepareCsrfToken(PageContext pageContext) {
return prepareCsrfToken(pageContext.getSession());
}
/**
* @see #prepareCsrfToken(javax.servlet.http.HttpSession, int)
*/
public static String prepareCsrfToken(HttpSession session) {
return prepareCsrfToken(session, timeToLive);
}
/**
* Generates new CSRF token and puts it in the session. Returns generated token value.
*/
@SuppressWarnings({"unchecked"})
public static synchronized String prepareCsrfToken(HttpSession session, int timeToLive) {
Set tokenSet = (Set) session.getAttribute(CSRF_TOKEN_SET);
if (tokenSet == null) {
tokenSet = new HashSet();
session.setAttribute(CSRF_TOKEN_SET, tokenSet);
}
String value;
boolean unique;
do {
value = RandomStringUtil.randomAlphaNumeric(32);
assureSize(tokenSet);
unique = tokenSet.add(new Token(value, timeToLive));
} while (!unique);
return value;
}
/**
* Removes expired tokens if token set is full.
* @see #setMaxTokensPerSession(int)
*/
protected static void assureSize(Set tokenSet) {
if (tokenSet.size() < maxTokensPerSession) {
return;
}
long validUntilMin = Long.MAX_VALUE;
Token tokenToRemove = null;
Iterator iterator = tokenSet.iterator();
while (iterator.hasNext()) {
Token token = iterator.next();
if (token.isExpired()) {
iterator.remove();
continue;
}
if (token.validUntil < validUntilMin) {
validUntilMin = token.validUntil;
tokenToRemove = token;
}
}
if ((tokenToRemove != null) && (tokenSet.size() >= maxTokensPerSession)) {
tokenSet.remove(tokenToRemove);
}
}
// ---------------------------------------------------------------- check
/**
* @see #checkCsrfToken(javax.servlet.http.HttpServletRequest, String)
*/
public static boolean checkCsrfToken(HttpServletRequest request) {
return checkCsrfToken(request, CSRF_TOKEN_NAME);
}
/**
* Checks if {@link jodd.servlet.tag.CsrfTokenTag CSRF token} is valid.
* Returns false if token was requested, but not found.
* Otherwise, it returns true.
*/
@SuppressWarnings({"unchecked"})
public static boolean checkCsrfToken(HttpServletRequest request, String tokenName) {
String tokenValue = request.getParameter(tokenName);
return checkCsrfToken(request.getSession(), tokenValue);
}
/**
* Checks token value.
C */
@SuppressWarnings({"unchecked"})
public static synchronized boolean checkCsrfToken(HttpSession session, String tokenValue) {
Set tokenSet = (Set) session.getAttribute(CSRF_TOKEN_SET);
if ((tokenSet == null) && (tokenValue == null)) {
return true;
}
if ((tokenSet == null) || (tokenValue == null)) {
return false;
}
boolean found = false;
Iterator it = tokenSet.iterator();
while (it.hasNext()) {
Token t = it.next();
if (t.isExpired()) {
it.remove();
continue;
}
if (t.getValue().equals(tokenValue)) {
it.remove();
found = true;
}
}
return found;
}
/**
* CSRF Token.
*/
public static class Token implements Serializable {
protected final String value;
protected final long validUntil;
public Token(String value) {
this(value, 0);
}
public Token(String value, long timeToLive) {
this.value = value;
this.validUntil = timeToLive <= 0 ? Long.MAX_VALUE : (System.currentTimeMillis() + timeToLive * 1000);
}
/**
* Returns true if token is expired.
*/
public boolean isExpired() {
return System.currentTimeMillis() > validUntil;
}
/**
* Returns token value.
*/
public String getValue() {
return value;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Token token = (Token) o;
return value.equals(token.value);
}
@Override
public int hashCode() {
return value.hashCode();
}
}
}