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Presently, the privilege check for SET SESSION AUTHORIZATION checks whether the original authenticated role was a superuser at connection start time. Even if the role loses the superuser attribute, its existing sessions are permitted to change session authorization to any role. This commit modifies this privilege check to verify the original authenticated role currently has superuser. In the event that the authenticated role loses superuser within a session authorization change, the authorization change will remain in effect, which means the user can still take advantage of the target role's privileges. However, [RE]SET SESSION AUTHORIZATION will only permit switching to the original authenticated role. Author: Joseph Koshakow Discussion: https://postgr.es/m/CAAvxfHc-HHzONQ2oXdvhFF9ayRnidPwK%2BfVBhRzaBWYYLVQL-g%40mail.gmail.com
131 lines
4.0 KiB
Plaintext
131 lines
4.0 KiB
Plaintext
<!--
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doc/src/sgml/ref/set_session_auth.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-set-session-authorization">
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<indexterm zone="sql-set-session-authorization">
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<primary>SET SESSION AUTHORIZATION</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>SET SESSION AUTHORIZATION</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>SET SESSION AUTHORIZATION</refname>
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<refpurpose>set the session user identifier and the current user identifier of the current session</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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SET [ SESSION | LOCAL ] SESSION AUTHORIZATION <replaceable class="parameter">user_name</replaceable>
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SET [ SESSION | LOCAL ] SESSION AUTHORIZATION DEFAULT
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RESET SESSION AUTHORIZATION
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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This command sets the session user identifier and the current user
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identifier of the current SQL session to be <replaceable
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class="parameter">user_name</replaceable>. The user name can be
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written as either an identifier or a string literal. Using this
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command, it is possible, for example, to temporarily become an
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unprivileged user and later switch back to being a superuser.
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</para>
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<para>
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The session user identifier is initially set to be the (possibly
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authenticated) user name provided by the client. The current user
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identifier is normally equal to the session user identifier, but
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might change temporarily in the context of <literal>SECURITY DEFINER</literal>
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functions and similar mechanisms; it can also be changed by
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<link linkend="sql-set-role"><command>SET ROLE</command></link>.
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The current user identifier is relevant for permission checking.
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</para>
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<para>
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The session user identifier can be changed only if the initial session
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user (the <firstterm>authenticated user</firstterm>) has the
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superuser privilege. Otherwise, the command is accepted only if it
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specifies the authenticated user name.
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</para>
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<para>
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The <literal>SESSION</literal> and <literal>LOCAL</literal> modifiers act the same
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as for the regular <link linkend="sql-set"><command>SET</command></link>
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command.
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</para>
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<para>
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The <literal>DEFAULT</literal> and <literal>RESET</literal> forms reset the session
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and current user identifiers to be the originally authenticated user
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name. These forms can be executed by any user.
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</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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<command>SET SESSION AUTHORIZATION</command> cannot be used within a
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<literal>SECURITY DEFINER</literal> function.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<programlisting>
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SELECT SESSION_USER, CURRENT_USER;
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session_user | current_user
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--------------+--------------
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peter | peter
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SET SESSION AUTHORIZATION 'paul';
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SELECT SESSION_USER, CURRENT_USER;
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session_user | current_user
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--------------+--------------
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paul | paul
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</programlisting>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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The SQL standard allows some other expressions to appear in place
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of the literal <replaceable>user_name</replaceable>, but these options
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are not important in practice. <productname>PostgreSQL</productname>
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allows identifier syntax (<literal>"<replaceable>username</replaceable>"</literal>), which SQL
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does not. SQL does not allow this command during a transaction;
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<productname>PostgreSQL</productname> does not make this
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restriction because there is no reason to.
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The <literal>SESSION</literal> and <literal>LOCAL</literal> modifiers are a
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<productname>PostgreSQL</productname> extension, as is the
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<literal>RESET</literal> syntax.
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</para>
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<para>
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The privileges necessary to execute this command are left
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implementation-defined by the standard.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-set-role"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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