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>20.5. Function and Trigger Security</A
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>   Functions and triggers allow users to insert code into the backend
   server that other users might execute unintentionally. Hence, both
   mechanisms permit users to <SPAN
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>"Trojan horse"</SPAN
>
   others with relative ease. The only real protection is tight
   control over who can define functions.
  </P
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>   Functions run inside the backend
   server process with the operating system permissions of the
   database server daemon.  If the programming language
   used for the function allows unchecked memory accesses, it is
   possible to change the server's internal data structures.
   Hence, among many other things, such functions can circumvent any
   system access controls.  Function languages that allow such access
   are considered <SPAN
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>"untrusted"</SPAN
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   <SPAN
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>PostgreSQL</SPAN
> allows only superusers to
   create functions written in those languages.
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