org.owasp.html.AttributePolicy Maven / Gradle / Ivy
// Copyright (c) 2011, Mike Samuel
// 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.
// Neither the name of the OWASP nor the names of its contributors may
// 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
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package org.owasp.html;
import com.google.common.base.Optional;
import com.google.common.collect.ImmutableList;
import java.util.Set;
import javax.annotation.CheckReturnValue;
import javax.annotation.Nullable;
import org.owasp.html.Joinable.JoinHelper;
/**
* A policy that can be applied to an HTML attribute to decide whether or not to
* allow it in the output, possibly after transforming its value.
*
* @author Mike Samuel ([email protected])
* @see HtmlPolicyBuilder.AttributeBuilder#matching(AttributePolicy)
*/
@TCB public interface AttributePolicy {
/**
* @param elementName the lower-case element name.
* @param attributeName the lower-case attribute name.
* @param value the attribute value without quotes and with HTML entities
* decoded.
*
* @return {@code null} to disallow the attribute or the adjusted value if
* allowed.
*/
public @Nullable String apply(
String elementName, String attributeName, String value);
/** Utilities for working with attribute policies. */
public static final class Util {
/**
* An attribute policy equivalent to applying all the given policies in
* order, failing early if any of them fails.
*/
@CheckReturnValue
public static final AttributePolicy join(AttributePolicy... policies) {
AttributePolicyJoiner joiner = new AttributePolicyJoiner();
for (AttributePolicy p : policies) {
if (p != null) {
joiner.unroll(p);
}
}
return joiner.join();
}
static final class AttributePolicyJoiner
extends JoinHelper {
AttributePolicyJoiner() {
super(AttributePolicy.class,
JoinableAttributePolicy.class,
REJECT_ALL_ATTRIBUTE_POLICY,
IDENTITY_ATTRIBUTE_POLICY);
}
@Override
Optional> split(AttributePolicy x) {
if (x instanceof JoinedAttributePolicy) {
return Optional.of(((JoinedAttributePolicy) x).policies);
} else {
return Optional.absent();
}
}
@Override
AttributePolicy rejoin(Set xs) {
return new JoinedAttributePolicy(xs);
}
}
}
/** An attribute policy that returns the value unchanged. */
public static final AttributePolicy IDENTITY_ATTRIBUTE_POLICY
= new AttributePolicy() {
public String apply(
String elementName, String attributeName, String value) {
return value;
}
};
/** An attribute policy that rejects all values. */
public static final AttributePolicy REJECT_ALL_ATTRIBUTE_POLICY
= new AttributePolicy() {
public @Nullable String apply(
String elementName, String attributeName, String value) {
return null;
}
};
/** An attribute policy that is joinable. */
static interface JoinableAttributePolicy
extends AttributePolicy, Joinable {
// Parameterized Appropriately.
}
}