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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>20.2. User Name Maps</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="auth-pg-hba-conf.html" title="20.1. The pg_hba.conf File" /><link rel="next" href="auth-methods.html" title="20.3. Authentication Methods" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">20.2. User Name Maps</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="auth-pg-hba-conf.html" title="20.1. The pg_hba.conf File">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="client-authentication.html" title="Chapter 20. Client Authentication">Up</a></td><th width="60%" align="center">Chapter 20. Client Authentication</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="auth-methods.html" title="20.3. Authentication Methods">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="AUTH-USERNAME-MAPS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">20.2. User Name Maps</h2></div></div></div><a id="id-1.6.7.9.2" class="indexterm"></a><p>
When using an external authentication system such as Ident or GSSAPI,
the name of the operating system user that initiated the connection
might not be the same as the database user (role) that is to be used.
In this case, a user name map can be applied to map the operating system
user name to a database user. To use user name mapping, specify
<code class="literal">map</code>=<em class="replaceable"><code>map-name</code></em>
in the options field in <code class="filename">pg_hba.conf</code>. This option is
supported for all authentication methods that receive external user names.
Since different mappings might be needed for different connections,
the name of the map to be used is specified in the
<em class="replaceable"><code>map-name</code></em> parameter in <code class="filename">pg_hba.conf</code>
to indicate which map to use for each individual connection.
</p><p>
User name maps are defined in the ident map file, which by default is named
<code class="filename">pg_ident.conf</code><a id="id-1.6.7.9.4.2" class="indexterm"></a>
and is stored in the
cluster's data directory. (It is possible to place the map file
elsewhere, however; see the <a class="xref" href="runtime-config-file-locations.html#GUC-IDENT-FILE">ident_file</a>
configuration parameter.)
The ident map file contains lines of the general form:
</p><pre class="synopsis">
<em class="replaceable"><code>map-name</code></em> <em class="replaceable"><code>system-username</code></em> <em class="replaceable"><code>database-username</code></em>
</pre><p>
Comments and whitespace are handled in the same way as in
<code class="filename">pg_hba.conf</code>. The
<em class="replaceable"><code>map-name</code></em> is an arbitrary name that will be used to
refer to this mapping in <code class="filename">pg_hba.conf</code>. The other
two fields specify an operating system user name and a matching
database user name. The same <em class="replaceable"><code>map-name</code></em> can be
used repeatedly to specify multiple user-mappings within a single map.
</p><p>
There is no restriction regarding how many database users a given
operating system user can correspond to, nor vice versa. Thus, entries
in a map should be thought of as meaning <span class="quote">“<span class="quote">this operating system
user is allowed to connect as this database user</span>”</span>, rather than
implying that they are equivalent. The connection will be allowed if
there is any map entry that pairs the user name obtained from the
external authentication system with the database user name that the
user has requested to connect as.
</p><p>
If the <em class="replaceable"><code>system-username</code></em> field starts with a slash (<code class="literal">/</code>),
the remainder of the field is treated as a regular expression.
(See <a class="xref" href="functions-matching.html#POSIX-SYNTAX-DETAILS" title="9.7.3.1. Regular Expression Details">Section 9.7.3.1</a> for details of
<span class="productname">PostgreSQL</span>'s regular expression syntax.) The regular
expression can include a single capture, or parenthesized subexpression,
which can then be referenced in the <em class="replaceable"><code>database-username</code></em>
field as <code class="literal">\1</code> (backslash-one). This allows the mapping of
multiple user names in a single line, which is particularly useful for
simple syntax substitutions. For example, these entries
</p><pre class="programlisting">
mymap /^(.*)@mydomain\.com$ \1
mymap /^(.*)@otherdomain\.com$ guest
</pre><p>
will remove the domain part for users with system user names that end with
<code class="literal">@mydomain.com</code>, and allow any user whose system name ends with
<code class="literal">@otherdomain.com</code> to log in as <code class="literal">guest</code>.
</p><div class="tip"><h3 class="title">Tip</h3><p>
Keep in mind that by default, a regular expression can match just part of
a string. It's usually wise to use <code class="literal">^</code> and <code class="literal">$</code>, as
shown in the above example, to force the match to be to the entire
system user name.
</p></div><p>
The <code class="filename">pg_ident.conf</code> file is read on start-up and
when the main server process receives a
<span class="systemitem">SIGHUP</span><a id="id-1.6.7.9.8.3" class="indexterm"></a>
signal. If you edit the file on an
active system, you will need to signal the postmaster
(using <code class="literal">pg_ctl reload</code>, calling the SQL function
<code class="function">pg_reload_conf()</code>, or using <code class="literal">kill
-HUP</code>) to make it re-read the file.
</p><p>
A <code class="filename">pg_ident.conf</code> file that could be used in
conjunction with the <code class="filename">pg_hba.conf</code> file in <a class="xref" href="auth-pg-hba-conf.html#EXAMPLE-PG-HBA.CONF" title="Example 20.1. Example pg_hba.conf Entries">Example 20.1</a> is shown in <a class="xref" href="auth-username-maps.html#EXAMPLE-PG-IDENT.CONF" title="Example 20.2. An Example pg_ident.conf File">Example 20.2</a>. In this example, anyone
logged in to a machine on the 192.168 network that does not have the
operating system user name <code class="literal">bryanh</code>, <code class="literal">ann</code>, or
<code class="literal">robert</code> would not be granted access. Unix user
<code class="literal">robert</code> would only be allowed access when he tries to
connect as <span class="productname">PostgreSQL</span> user <code class="literal">bob</code>, not
as <code class="literal">robert</code> or anyone else. <code class="literal">ann</code> would
only be allowed to connect as <code class="literal">ann</code>. User
<code class="literal">bryanh</code> would be allowed to connect as either
<code class="literal">bryanh</code> or as <code class="literal">guest1</code>.
</p><div class="example" id="EXAMPLE-PG-IDENT.CONF"><p class="title"><strong>Example 20.2. An Example <code class="filename">pg_ident.conf</code> File</strong></p><div class="example-contents"><pre class="programlisting">
# MAPNAME SYSTEM-USERNAME PG-USERNAME
omicron bryanh bryanh
omicron ann ann
# bob has user name robert on these machines
omicron robert bob
# bryanh can also connect as guest1
omicron bryanh guest1
</pre></div></div><br class="example-break" /></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="auth-pg-hba-conf.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="client-authentication.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="auth-methods.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">20.1. The <code class="filename">pg_hba.conf</code> File </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 20.3. Authentication Methods</td></tr></table></div></body></html>
