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Document the behavior of GRANT/REVOKE in cases where the privilege is

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held by means of role membership, rather than directly.  Per discussion
and bug fix of a couple weeks ago.
This commit is contained in:
Tom Lane
2005-10-20 19:18:01 +00:00
parent 7218aab7a2
commit c9de6b922e
3 changed files with 143 additions and 79 deletions
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170
doc/src/sgml/user-manag.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/user-manag.sgml,v 1.32 2005/10/15 20:12:33 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/user-manag.sgml,v 1.33 2005/10/20 19:18:00 tgl Exp $
-->
<chapter id="user-manag">
@@ -267,6 +267,81 @@ ALTER ROLE myname SET enable_indexscan TO off;
</para>
</sect1>
<sect1 id="privileges">
<title>Privileges</title>
<indexterm zone="privileges">
<primary>privilege</primary>
</indexterm>
<indexterm zone="privileges">
<primary>owner</primary>
</indexterm>
<indexterm zone="privileges">
<primary>GRANT</primary>
</indexterm>
<indexterm zone="privileges">
<primary>REVOKE</primary>
</indexterm>
<para>
When an object is created, it is assigned an owner. The
owner is normally the role that executed the creation statement.
For most kinds of objects, the initial state is that only the owner
(or a superuser) can do anything with the object. To allow
other roles to use it, <firstterm>privileges</firstterm> must be
granted.
There are several different kinds of privilege: <literal>SELECT</>,
<literal>INSERT</>, <literal>UPDATE</>, <literal>DELETE</>,
<literal>RULE</>, <literal>REFERENCES</>, <literal>TRIGGER</>,
<literal>CREATE</>, <literal>TEMPORARY</>, <literal>EXECUTE</>,
and <literal>USAGE</>. For more
information on the different types of privileges supported by
<productname>PostgreSQL</productname>, see the
<xref linkend="sql-grant" endterm="sql-grant-title"> reference page.
</para>
<para>
To assign privileges, the <command>GRANT</command> command is
used. So, if <literal>joe</literal> is an existing role, and
<literal>accounts</literal> is an existing table, the privilege to
update the table can be granted with
<programlisting>
GRANT UPDATE ON accounts TO joe;
</programlisting>
The special name <literal>PUBLIC</literal> can
be used to grant a privilege to every role on the system. Writing
<literal>ALL</literal> in place of a specific privilege specifies that all
privileges that apply to the object will be granted.
</para>
<para>
To revoke a privilege, use the fittingly named
<xref linkend="sql-revoke" endterm="sql-revoke-title"> command:
<programlisting>
REVOKE ALL ON accounts FROM PUBLIC;
</programlisting>
</para>
<para>
The special privileges of an object's owner (i.e., the right to modify
or destroy the object) are always implicit in being the owner,
and cannot be granted or revoked. But the owner can choose
to revoke his own ordinary privileges, for example to make a
table read-only for himself as well as others.
</para>
<para>
An object can be assigned to a new owner with an <command>ALTER</command>
command of the appropriate kind for the object. Superusers can always do
this; ordinary roles can only do it if they are both the current owner
of the object (or a member of the owning role) and a member of the new
owning role.
</para>
</sect1>
<sect1 id="role-membership">
<title>Role Membership</title>
@@ -373,6 +448,22 @@ RESET ROLE;
</para>
</note>
<para>
The role attributes <literal>LOGIN</>, <literal>SUPERUSER</>,
<literal>CREATEDB</>, and <literal>CREATEROLE</> can be thought of as
special privileges, but they are never inherited as ordinary privileges
on database objects are. You must actually <command>SET ROLE</> to a
specific role having one of these attributes in order to make use of
the attribute. Continuing the above example, we might well choose to
grant <literal>CREATEDB</> and <literal>CREATEROLE</> to the
<literal>admin</> role. Then a session connecting as role <literal>joe</>
would not have these privileges immediately, only after doing
<command>SET ROLE admin</>.
</para>
<para>
</para>
<para>
To destroy a group role, use <xref
linkend="sql-droprole" endterm="sql-droprole-title">:
@@ -386,87 +477,12 @@ DROP ROLE <replaceable>name</replaceable>;
</para>
</sect1>
<sect1 id="privileges">
<title>Privileges</title>
<indexterm zone="privileges">
<primary>privilege</primary>
</indexterm>
<indexterm zone="privileges">
<primary>owner</primary>
</indexterm>
<indexterm zone="privileges">
<primary>GRANT</primary>
</indexterm>
<indexterm zone="privileges">
<primary>REVOKE</primary>
</indexterm>
<para>
When an object is created, it is assigned an owner. The
owner is normally the role that executed the creation statement.
For most kinds of objects, the initial state is that only the owner
(or a superuser) can do anything with the object. To allow
other roles to use it, <firstterm>privileges</firstterm> must be
granted.
There are several different kinds of privilege: <literal>SELECT</>,
<literal>INSERT</>, <literal>UPDATE</>, <literal>DELETE</>,
<literal>RULE</>, <literal>REFERENCES</>, <literal>TRIGGER</>,
<literal>CREATE</>, <literal>TEMPORARY</>, <literal>EXECUTE</>,
and <literal>USAGE</>. For more
information on the different types of privileges supported by
<productname>PostgreSQL</productname>, see the
<xref linkend="sql-grant" endterm="sql-grant-title"> reference page.
</para>
<para>
To assign privileges, the <command>GRANT</command> command is
used. So, if <literal>joe</literal> is an existing role, and
<literal>accounts</literal> is an existing table, the privilege to
update the table can be granted with
<programlisting>
GRANT UPDATE ON accounts TO joe;
</programlisting>
The special name <literal>PUBLIC</literal> can
be used to grant a privilege to every role on the system. Writing
<literal>ALL</literal> in place of a specific privilege specifies that all
privileges that apply to the object will be granted.
</para>
<para>
To revoke a privilege, use the fittingly named
<xref linkend="sql-revoke" endterm="sql-revoke-title"> command:
<programlisting>
REVOKE ALL ON accounts FROM PUBLIC;
</programlisting>
</para>
<para>
The special privileges of an object's owner (i.e., the right to modify
or destroy the object) are always implicit in being the owner,
and cannot be granted or revoked. But the owner can choose
to revoke his own ordinary privileges, for example to make a
table read-only for himself as well as others.
</para>
<para>
An object can be assigned to a new owner with an <command>ALTER</command>
command of the appropriate kind for the object. Superusers can always do
this; ordinary roles can only do it if they are both the current owner
of the object (or a member of the owning role) and a member of the new
owning role.
</para>
</sect1>
<sect1 id="perm-functions">
<title>Functions and Triggers</title>
<para>
Functions and triggers allow users to insert code into the backend
server that other users may execute without knowing it. Hence, both
server that other users may execute unintentionally. Hence, both
mechanisms permit users to <quote>Trojan horse</quote>
others with relative ease. The only real protection is tight
control over who can define functions.