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From Jonathan Revusky <jrevu...@terra.es>
Subject Re: template encodings
Date Mon, 16 Jul 2001 21:38:03 GMT
Jon Stevens wrote:
> 
> on 7/15/01 5:09 PM, "Jonathan Revusky" <jrevusky@terra.es> wrote:
> 
> > Somebody else pointed out that if you
> > specifically give an absolute location for the template file, it doesn't
> > work, i.e. some naive user who tries:
> > getTemplate("C:\\mytemplates\\mytemplate.html"). Well, that's basically
> > a bug. The default code should have the smarts that if you give it an
> > absolute path AND the file is there and readable, it should use it. To
> > have any other behavior is to willfully waste people's time.
> 
> No, it is a security hole.
> 
> You don't want some random user to be able to access something like
> /etc/passwd or /etc/shadow.

Could you explain the mechanism by which a random user would access
/etc/passwd because I load a template file from an absolute path?

> 
> Setting a base template path is necessary. Then everything to access the
> file is relative to that path and you don't have to worry about people
> randomly reading files from that path.
> 
> Go read the bugtraq archives. You will see literally hundreds of security
> holes as a result of what you describe.
> 
> This is a very common mistake by newbie software engineers.
> 
> Lastly, it is entirely possible within Velocity for you to come up with your
> own ResourceLoader. So, if you don't like the one that comes with Velocity,
> then make your own! 


I already did. Though I am advocating the position of a newbie user, *I*
am not at all helpless in this regard. The code below is in the version
of Niggle I put up today. It seems fairly reasonable to me. Note that a
template is only loaded from an absolute location if the application
programmer specifies an absolute location. I encourage people to locate
their templates relative to the servlet context classpath.

/*
Bridge Code to use Velocity template engine with Niggle
Copyright (c) 2001, Jonathan Revusky
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright
notice,
this list of conditions and the following disclaimer in the
documentation
and/or other materials provided with the distribution.

The name of Jonathan Revusky may not be used to endorse or promote
products derived from this software without specific prior written
permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/

package com.revusky.niggle.templates.velocityimpl;

import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.resource.loader.ResourceLoader;
import org.apache.velocity.runtime.resource.Resource;
import org.apache.commons.collections.ExtendedProperties;
import com.revusky.oreo.util.*;
import java.io.*;
import java.util.*;
import java.net.URL;

public class CustomResourceLoader extends ResourceLoader {

    static private ClassLoader classLoader;
    static private String searchPath;

    static public void setClassLoader(ClassLoader classLoader) {
        CustomResourceLoader.classLoader = classLoader;
    }

    static public void setSearchPath(String searchPath) {
        CustomResourceLoader.searchPath = searchPath;
    }

    public void init(ExtendedProperties props) {
        Logger.log("Niggle custom resource loader for Velocity :
initialized.", Logger.LOG_INFO);
    }

    public InputStream getResourceStream(String name)
    throws ResourceNotFoundException {
        try {
            return findResource(name);
        } catch (IOException ioe) {
        }
        throw new ResourceNotFoundException("Template " + name + " not
found");
    }

    private InputStream findResource(String name) throws IOException {
        InputStream is = findAbsolute(name);
        if (is == null) {
            is = findOnSearchPath(name);
        }
        if (is == null) {
            is = findOnClassPath(name);
        }
        return is;
    }

    private InputStream findAbsolute(String name) throws IOException {
        File f = new File(name);
        if (f.isAbsolute() && f.canRead()) {
            fileCache.put(name, f);
            lastModifiedCache.put(name, new Long(f.lastModified()));
            return new FileInputStream(f);
        }
        else
            return null;
    }

    private InputStream findOnSearchPath(String name) throws IOException
{
        if (searchPath != null) {
            StringTokenizer st = new StringTokenizer(searchPath,
File.pathSeparator);
            while (st.hasMoreTokens()) {
                String path = st.nextToken();
                if (path.endsWith("/") || path.endsWith("\\")) {
                    path = path.substring(0, path.length() -1);
                }
                String filename = path + "/" + name;
                InputStream is = findAbsolute(filename);
                if (is == null) {
                    is = findOnClassPath(filename);
                }
                if (is != null) {
                    return is;
                }
            }
        }
        return null;
    }

    private InputStream findOnClassPath(String name) throws IOException
{
        URL url = classLoader.getResource(name);
        if (url == null) {
            url = ClassLoader.getSystemResource(name);
        }
        if (url == null) {
            return null;
        }
        String filename = url.getFile();
        if (filename.startsWith("file:")) {
            filename = filename.substring(5);
        }
        File f = new File(filename);
        if (f.exists()) {
            fileCache.put(name, f);
            lastModifiedCache.put(name, new Long(f.lastModified()));
        }
        else
            fileCache.put(name, null);
        return url.openStream();
    }


    public boolean isSourceModified(Resource res) {
        String name = res.getName();
        if (fileCache.containsKey(name)) {
            File f = (File) fileCache.get(name);
            if (f == null) {
                return false;
            }
            else {
                long l = f.lastModified();
                Long L = (Long) lastModifiedCache.get(name);
                return (L!=null) && (L.longValue() < l);
            }
        }
        return false;
    }

    public long getLastModified(Resource res) {
        String name = res.getName();
        Long L = (Long) lastModifiedCache.get(name);
        if (L!= null) {
            return L.longValue();
        }
        return 0L;
    }

    private Map fileCache = Collections.synchronizedMap(new HashMap());
    private Map lastModifiedCache = Collections.synchronizedMap(new
HashMap());
}

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