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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>22.6. Function Security</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="predefined-roles.html" title="22.5. Predefined Roles" /><link rel="next" href="managing-databases.html" title="Chapter 23. Managing Databases" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">22.6. Function Security</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="predefined-roles.html" title="22.5. Predefined Roles">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="user-manag.html" title="Chapter 22. Database Roles">Up</a></td><th width="60%" align="center">Chapter 22. Database Roles</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="managing-databases.html" title="Chapter 23. Managing Databases">Next</a></td></tr></table><hr /></div><div class="sect1" id="PERM-FUNCTIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">22.6. Function Security <a href="#PERM-FUNCTIONS" class="id_link">#</a></h2></div></div></div><p>
Functions, triggers and row-level security policies allow users to insert
code into the backend server that other users might execute
unintentionally. Hence, these mechanisms permit users to <span class="quote">“<span class="quote">Trojan
horse</span>”</span> others with relative ease. The strongest protection is tight
control over who can define objects. Where that is infeasible, write
queries referring only to objects having trusted owners. Remove
from <code class="varname">search_path</code> any schemas that permit untrusted users
to create objects.
</p><p>
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 class="quote">“<span class="quote">untrusted</span>”</span>, and
<span class="productname">PostgreSQL</span> allows only superusers to
create functions written in those languages.
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