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https://issues.apache.org/jira/browse/MYFACES-4266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16698501#comment-16698501
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ASF GitHub Bot commented on MYFACES-4266:
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cnsgithub edited a comment on issue #27: MYFACES-4266: Ajax update fails due to
invalid characters in response XML (DoS)
URL: https://github.com/apache/myfaces/pull/27#issuecomment-441527197
> 1. all right, it would be just cool if we would have some more tests which
also covers other #write methods or even writeAttribute - but not required
Provided another test for `writeAttribute`.
> 2. Oh, really sorry - thats my fault because of a too fast review. I
thought that you would wrap a simple char with a string now.
> I would just do:
>
> ` @Override public void write(String str, int off, int len) throws
IOException { super.write(new String(xmlEncode(str.toCharArray())), off, len);
}`
Done.
> I just wonder if we should replace the invalid char by a blank instead of
empty? Not sure...
Also considered this. However, it would complicate things since array
lengths might change then. When looking at OWASP's encoder you'll find they
also replace illegal characters by spaces.
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> Ajax update fails due to invalid characters in response XML (DoS)
> -----------------------------------------------------------------
>
> Key: MYFACES-4266
> URL: https://issues.apache.org/jira/browse/MYFACES-4266
> Project: MyFaces Core
> Issue Type: Bug
> Affects Versions: 2.3.2
> Environment: jetty 9.4.14.v20181114
> JDK 10
> Reporter: cnsgithub
> Priority: Major
>
> I noticed that the {{<f:ajax />}} update fails when the updated form contains
> unicode characters, which are not allowed in the [XML 1.0
> spec|https://www.w3.org/TR/REC-xml/#charsets].
> h2. Expected Behaviour
> If the update response contains characters that are not allowed in XML, they
> should be filtered by MyFaces before writing the response.
> h2. Actual Behaviour
> Some illegal XML characters are not filtered and therefore the browser fails
> to parse the response.
> h2. Steps to reproduce
> I created a small github project to reproduce this behaviour:
> [https://github.com/cnsgithub/mojarra-ajax/tree/myfaces] (branch myfaces)
> To reproduce:
> - {{git clone [https://github.com/cnsgithub/mojarra-ajax]}}
> - {{git checkout myfaces}}
> - run {{mvn clean package jetty:run}}
> - after the server has started, open [http://localhost:8080/index.xhtml]
> - Click the button, the error should occur
> The issue also occurs with user supplied inputs:
> - open [http://localhost:8080/input.xhtml]
> - Paste the characters from the {{illegal-xml-chars.txt}} file into the
> input field
> - Click the button
> This issue should be addressed with high priority since it is security
> related (might be exploited for Denial of Service).
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