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Override URL encoding when serializing results to HTML #87

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merged 2 commits into from
Jun 24, 2021
Merged

Override URL encoding when serializing results to HTML #87

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be6a42b
Override URL encoding when serializing results to HTML
spassarop Jun 17, 2021
2dc029f
Add useXHTML as false on HTML encoding test
spassarop Jun 17, 2021
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13 changes: 13 additions & 0 deletions src/main/java/org/owasp/validator/html/scan/ASHTMLSerializer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,13 +4,16 @@
import org.apache.xml.serialize.HTMLdtd;
import org.apache.xml.serialize.OutputFormat;
import org.owasp.validator.html.InternalPolicy;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.Writer;

@SuppressWarnings("deprecation")
public class ASHTMLSerializer extends org.apache.xml.serialize.HTMLSerializer {

private static final Logger logger = LoggerFactory.getLogger(ASHTMLSerializer.class);
private boolean encodeAllPossibleEntities;

public ASHTMLSerializer(Writer w, OutputFormat format, InternalPolicy policy) {
Expand Down Expand Up @@ -67,4 +70,14 @@ public void endElementIO(String namespaceURI, String localName,
_printer.flush();
}

@Override
protected String escapeURI(String uri) {
String originalURI = uri;
try {
printEscaped(uri);
} catch (IOException e) {
logger.error("URI escaping failed for value: " + originalURI);
}
return "";
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Is this method supposed to ALWAYS return an empty string? Seems strange to me.

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It is. On the HTMLSerializer, that function is supposed to returned the URL with escaped quotes and nothing else. I'm reusing printEscaped which does the encoding we want and internally "prints" the result in the XML that is being built. If I return a non-empty string, that string is also "printed" because the call to escapeURI is something like print(escapeURI()). I mentioned this on our emails, it may be explained better there.

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Can you add all the necessary explanation to this code as comments so it stands alone? Otherwise future reviewers will have the same concerns.

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I've done a separate PR with the comment. I tried to push directly to 1.6.4 and had git issues, but I'm kinda in a hurry and wanted to have this solved fast.

}
}
12 changes: 12 additions & 0 deletions src/test/java/org/owasp/validator/html/test/AntiSamyTest.java
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Expand Up @@ -1490,5 +1490,17 @@ public void testGithubIssue81() throws ScanException, PolicyException {
assertThat(as.scan("<p style=\"color: red\">Some Text</p>", policy, AntiSamy.DOM).getCleanHTML(), not(containsString("!important")));
assertThat(as.scan("<p style=\"color: red\">Some Text</p>", policy, AntiSamy.SAX).getCleanHTML(), not(containsString("!important")));
}

@Test
public void entityReferenceEncodedInHtmlAttribute() throws ScanException, PolicyException {
// Concern is that "&" is not being encoded and "#00058" was not being interpreted as ":"
// so the validations based on regexp passed and a browser would load "&:" together.
// All this when not using the XHTML serializer.
Policy revised = policy.cloneWithDirective("useXHTML","false");
assertThat(as.scan("<p><a href=\"javascript&#00058x=1,%61%6c%65%72%74%28%22%62%6f%6f%6d%22%29\">xss</a></p>", revised, AntiSamy.DOM).getCleanHTML(),
containsString("javascript&amp;#00058"));
assertThat(as.scan("<p><a href=\"javascript&#00058x=1,%61%6c%65%72%74%28%22%62%6f%6f%6d%22%29\">xss</a></p>", revised, AntiSamy.SAX).getCleanHTML(),
containsString("javascript&amp;#00058"));
}
}