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https://issues.apache.org/jira/browse/CMIS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14709010#comment-14709010
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Florent Guillaume commented on CMIS-941:
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Nevertheless, if only to appease code audits, I think it's a good idea to add:
{code:java}
transformerFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING);
{code}
even though this code is for debugging.
> XML External Entity Injection possible in LoggingFilter
> -------------------------------------------------------
>
> Key: CMIS-941
> URL: https://issues.apache.org/jira/browse/CMIS-941
> Project: Chemistry
> Issue Type: Bug
> Components: opencmis-client
> Affects Versions: OpenCMIS 0.13.0
> Reporter: Donald Kwakkel
>
> The XML parser configured in LoggingFilter.java:205 does not prevent nor
> limit Document Type Definition (DTD) entity resolution. This can expose the
> parser to an XML Entity Expansion injection.
> Explanation:
> XML Entity Expansion injection also known as XML Bombs are DoS attacks that
> benefit from valid and well-formed XML blocks that expand exponentially until
> they exhaust the server allocated resources. XML allows to define custom
> entities which act as string substitution macros. By nesting recurrent entity
> resolutions, an attacker can easily crash the server resources.
> The following XML document shows an example of an XML Bomb.
> <?xml version="1.0"?>
> <!DOCTYPE lolz [
> <!ENTITY lol "lol">
> <!ENTITY lol2 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
> <!ENTITY lol3
> "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
> <!ENTITY lol4
> "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
> <!ENTITY lol5
> "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
> <!ENTITY lol6
> "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
> <!ENTITY lol7
> "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
> <!ENTITY lol8
> "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
> <!ENTITY lol9
> "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
> ]>
> <lolz>&lol9;</lolz>
> This test could crash the server by expanding the small XML document into
> more than 3GB in memory.
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