/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.security.web.firewall;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Default implementation which wraps requests in order to provide consistent
* values of the {@code servletPath} and {@code pathInfo}, which do not contain
* path parameters (as defined in
* <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>). Different
* servlet containers interpret the servlet spec differently as to how path
* parameters are treated and it is possible they might be added in order to
* bypass particular security constraints. When using this implementation, they
* will be removed for all requests as the request passes through the security
* filter chain. Note that this means that any segments in the decoded path
* which contain a semi-colon, will have the part following the semi-colon
* removed for request matching. Your application should not contain any valid
* paths which contain semi-colons.
* <p>
* If any un-normalized paths are found (containing directory-traversal
* character sequences), the request will be rejected immediately. Most
* containers normalize the paths before performing the servlet-mapping, but
* again this is not guaranteed by the servlet spec.
*
* @author Luke Taylor
*/
public class DefaultHttpFirewall implements HttpFirewall {
private boolean allowUrlEncodedSlash;
@Override
public FirewalledRequest getFirewalledRequest(HttpServletRequest request) throws RequestRejectedException {
FirewalledRequest fwr = new RequestWrapper(request);
if (!isNormalized(fwr.getServletPath()) || !isNormalized(fwr.getPathInfo())) {
throw new RequestRejectedException("Un-normalized paths are not supported: " + fwr.getServletPath()
+ (fwr.getPathInfo() != null ? fwr.getPathInfo() : ""));
}
String requestURI = fwr.getRequestURI();
if (containsInvalidUrlEncodedSlash(requestURI)) {
throw new RequestRejectedException("The requestURI cannot contain encoded slash. Got " + requestURI);
}
return fwr;
}
@Override
public HttpServletResponse getFirewalledResponse(HttpServletResponse response) {
return new FirewalledResponse(response);
}
/**
* <p>
* Sets if the application should allow a URL encoded slash character.
* </p>
* <p>
* If true (default is false), a URL encoded slash will be allowed in the
* URL. Allowing encoded slashes can cause security vulnerabilities in some
* situations depending on how the container constructs the
* HttpServletRequest.
* </p>
*
* @param allowUrlEncodedSlash
* the new value (default false)
*/
public void setAllowUrlEncodedSlash(boolean allowUrlEncodedSlash) {
this.allowUrlEncodedSlash = allowUrlEncodedSlash;
}
private boolean containsInvalidUrlEncodedSlash(String uri) {
if (this.allowUrlEncodedSlash || uri == null) {
return false;
}
if (uri.contains("%2f") || uri.contains("%2F")) {
return true;
}
return false;
}
/**
* Checks whether a path is normalized (doesn't contain path traversal
* sequences like "./", "/../" or "/.")
*
* @param path
* the path to test
* @return true if the path doesn't contain any path-traversal character
* sequences.
*/
private boolean isNormalized(String path) {
if (path == null) {
return true;
}
for (int j = path.length(); j > 0;) {
int i = path.lastIndexOf('/', j - 1);
int gap = j - i;
if (gap == 2 && path.charAt(i + 1) == '.') {
// ".", "/./" or "/."
return false;
} else if (gap == 3 && path.charAt(i + 1) == '.' && path.charAt(i + 2) == '.') {
return false;
}
j = i;
}
return true;
}
}