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AllowedResourceAliasChecker.java
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AllowedResourceAliasChecker.java
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//
// ========================================================================
// Copyright (c) 1995-2021 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.server;
import org.eclipse.jetty.server.handler.ContextHandler;
import org.eclipse.jetty.util.StringUtil;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.resource.Resource;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.Path;
/**
* This will approve an alias to any resource which is not a protected target.
* Except symlinks...
*/
public class AllowedResourceAliasChecker implements ContextHandler.AliasCheck
{
private static final Logger LOG = Log.getLogger(AllowedResourceAliasChecker.class);
private final ContextHandler _contextHandler;
private final boolean _checkSymlinkTargets;
public AllowedResourceAliasChecker(ContextHandler contextHandler)
{
this(contextHandler, false);
}
public AllowedResourceAliasChecker(ContextHandler contextHandler, boolean checkSymlinkTargets)
{
_contextHandler = contextHandler;
_checkSymlinkTargets = checkSymlinkTargets;
}
@Override
public boolean check(String uri, Resource resource)
{
try
{
if (!resource.exists())
return false;
Path resourcePath = resource.getFile().toPath();
Path realPath = resourcePath.toRealPath(LinkOption.NOFOLLOW_LINKS);
if (isProtectedPath(realPath, false))
return false;
if (_checkSymlinkTargets && hasSymbolicLink(resourcePath))
{
realPath = resourcePath.toRealPath();
if (isProtectedPath(realPath, true))
return false;
}
}
catch (Throwable t)
{
LOG.warn(t);
return false;
}
return true;
}
private boolean isProtectedPath(Path path, boolean followLinks) throws IOException
{
String basePath = followLinks ? _contextHandler.getBaseResource().getFile().toPath().toRealPath().toString() :
_contextHandler.getBaseResource().getFile().toPath().toRealPath(LinkOption.NOFOLLOW_LINKS).toString();
String targetPath = path.toString();
if (!targetPath.startsWith(basePath))
return true;
for (String s : _contextHandler.getProtectedTargets())
{
String protectedTarget = new File(basePath, s).getCanonicalPath();
if (StringUtil.startsWithIgnoreCase(targetPath, protectedTarget))
{
if (targetPath.length() == protectedTarget.length())
return true;
// Check that the target prefix really is a path segment.
char c = targetPath.charAt(protectedTarget.length());
if (c == File.separatorChar)
return true;
}
}
return false;
}
private boolean hasSymbolicLink(Path path)
{
// Is file itself a symlink?
if (Files.isSymbolicLink(path))
return true;
// Lets try each path segment
Path base = path.getRoot();
for (Path segment : path)
{
base = base.resolve(segment);
if (Files.isSymbolicLink(base))
return true;
}
return false;
}
@Override
public String toString()
{
return String.format("%s@%x{checkSymlinkTargets=%s}", AllowedResourceAliasChecker.class.getSimpleName(), hashCode(), _checkSymlinkTargets);
}
}