Security - eXist: A NoSQL Database and Application Development Platform - page 179

Table 8-12. Security-sensitive XQuery extension modules

XQuery
extension
module

Security implications of use

Cache module A user could potentially store a large quantity of information into the cache. This would exhaust the

memory available to the JVM used by eXist and could cause the database to crash.

Counter module A user could create many counters on disk, filling the available disk space of the server and thereby

potentially crashing eXist or the underlying server.

File module You have to be a user in the dba group in eXist to use the functions in the File module. However, should a

user be able to obtain dba privileges, he will be able to read/write anywhere in the filesystem that the
account under which the eXist server is running can read/write. Potentially, he could delete the .dbx files
that make up your database, download data or sensitive files, or fill up your server's disk space.

FTP module(s) The EXPath FTP module could allow a user to retrieve documents from remote sources by URI; you can

reduce or alleviate this risk by using sensible firewall and network settings. This module could also
potentially be used to launch a Denial of Service (DoS) attack against a remote service.

HTTP module(s) eXist and EXPath HTTP module could allow a user to retrieve documents from remote sources by URI; you

can reduce or alleviate this risk by using sensible firewall and network settings (e.g., forced transparent
proxy). These modules could also potentially be used to launch a DoS attack against a remote service.

JNDI module A user could potentially gain access to external JNDI sources, depending on how the authentication of the

JNDI sources is configured by the container (e.g., Jetty, Tomcat, etc.).

Mail module The Mail module could allow a user to send email either via a local sendmail or via a remote SMTP host.

This could be used to send SPAM or launch a DoS attack against a remote SMTP server. Consequently, a
local sendmail should not be used and remote SMTP servers should be secured appropriately to avoid such
attacks.

Memcached
module

A user could potentially store a large quantity of information into a Memcached instance, which could
affect the stability of that instance and the server on which it resides.

Session module A user could potentially store a large quantity of information into her session. This would exhaust the

memory available to the JVM used by eXist and could cause the database to crash.

SQL module A user could potentially open many connections against a remote SQL database, which could affect its

ability to respond and, in effect, cause a DoS attack.

Util module A user could use the util:serialize function to create many files on disk, filling the available disk

space of the server and therefore potentially crashing eXist or the underlying server.
A user could use the util:wait function to pause the current database broker for a long period. If this
was done across many connections, the available brokers could rapidly be exhausted, effectively causing a
DoS attack on eXist.