ArcGIS Server 10.3.1: RMIClassLoader useCodebaseOnly=false RCE

[Harrison Neal <hneal () whatdidibreak com>]

Using an Esri-provided image on Azure's Marketplace, ArcGIS Server 10.3.1
started Java's rmid on port 1098 and explicitly set the
property java.rmi.server.useCodebaseOnly equal to false.

Screenshot:
https://www.dropbox.com/s/xz9ugal3ixnfh1c/10.3.1_rmid_useCodebaseOnly%3Dfalse.png?dl=0

As discussed on Oracle's website, the default value of
java.rmi.server.useCodebaseOnly was changed to true in Java 7 Update 21,
with a remark that setting it to false could create a risk of RCE.

Link:
http://docs.oracle.com/javase/7/docs/technotes/guides/rmi/enhancements-7.html

While the version of Java included in ArcGIS Server 10.3.1 appears to be
Java 7 Update 76, which would have the more secure default setting, that is
irrelevant due to the ArcGIS solution manually changing it.

Screenshot:
https://www.dropbox.com/s/5reh81dwwp9e4dz/10.3.1_rmid_java7u76.png?dl=0

When an attacker can remotely reach rmid on the victim server, and the
victim server can reach a web server on a machine controlled by the
attacker, this is relatively easily exploited to gain RCE.

Video:
https://www.dropbox.com/s/t4fmxwzjzzo7yhe/ArcGIS_useCodebaseOnly%3Dfalse_exploitation.wmv?dl=0

Administrators are encouraged to use a tool such as Process Explorer or
wmic to ensure that the command line arguments passed to rmid have the
java.rmi.server.useCodebaseOnly property equal to true.

During testing, Esri-provided images on Azure's Marketplace for ArcGIS
Server 10.4.1 and 10.5.1 were found to set that property to true;
administrators may try updating to a newer version of ArcGIS Server, and/or
contacting Esri for assistance.

If an update is required but not immediately possible, consider firewall
rules to block access to rmid from systems that have no need to connect to
it.

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