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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >passwordcheck</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Additional Supplied Modules" HREF="contrib.html"><LINK REL="PREVIOUS" TITLE="pageinspect" HREF="pageinspect.html"><LINK REL="NEXT" TITLE="pg_buffercache" HREF="pgbuffercache.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="pageinspect" HREF="pageinspect.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Appendix F. Additional Supplied Modules</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="pg_buffercache" HREF="pgbuffercache.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="PASSWORDCHECK" >F.23. passwordcheck</A ></H1 ><P > The <TT CLASS="FILENAME" >passwordcheck</TT > module checks users' passwords whenever they are set with <A HREF="sql-createrole.html" >CREATE ROLE</A > or <A HREF="sql-alterrole.html" >ALTER ROLE</A >. If a password is considered too weak, it will be rejected and the command will terminate with an error. </P ><P > To enable this module, add <TT CLASS="LITERAL" >'$libdir/passwordcheck'</TT > to <A HREF="runtime-config-resource.html#GUC-SHARED-PRELOAD-LIBRARIES" >shared_preload_libraries</A > in <TT CLASS="FILENAME" >postgresql.conf</TT >, then restart the server. </P ><P > You can adapt this module to your needs by changing the source code. For example, you can use <A HREF="http://sourceforge.net/projects/cracklib/" TARGET="_top" >CrackLib</A > to check passwords — this only requires uncommenting two lines in the <TT CLASS="FILENAME" >Makefile</TT > and rebuilding the module. (We cannot include <SPAN CLASS="PRODUCTNAME" >CrackLib</SPAN > by default for license reasons.) Without <SPAN CLASS="PRODUCTNAME" >CrackLib</SPAN >, the module enforces a few simple rules for password strength, which you can modify or extend as you see fit. </P ><DIV CLASS="CAUTION" ><P ></P ><TABLE CLASS="CAUTION" BORDER="1" WIDTH="100%" ><TR ><TD ALIGN="CENTER" ><B >Caution</B ></TD ></TR ><TR ><TD ALIGN="LEFT" ><P > To prevent unencrypted passwords from being sent across the network, written to the server log or otherwise stolen by a database administrator, <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > allows the user to supply pre-encrypted passwords. Many client programs make use of this functionality and encrypt the password before sending it to the server. </P ><P > This limits the usefulness of the <TT CLASS="FILENAME" >passwordcheck</TT > module, because in that case it can only try to guess the password. For this reason, <TT CLASS="FILENAME" >passwordcheck</TT > is not recommended if your security requirements are high. It is more secure to use an external authentication method such as Kerberos (see <A HREF="client-authentication.html" >Chapter 19</A >) than to rely on passwords within the database. </P ><P > Alternatively, you could modify <TT CLASS="FILENAME" >passwordcheck</TT > to reject pre-encrypted passwords, but forcing users to set their passwords in clear text carries its own security risks. </P ></TD ></TR ></TABLE ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="pageinspect.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="pgbuffercache.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >pageinspect</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >pg_buffercache</TD ></TR ></TABLE ></DIV ></BODY ></HTML >