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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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25
doc/src/sgml/ref/grant.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/grant.sgml,v 1.49 2005/10/13 23:26:00 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/grant.sgml,v 1.50 2005/10/20 19:18:01 tgl Exp $
PostgreSQL documentation
-->
@ -343,6 +343,29 @@ GRANT <replaceable class="PARAMETER">role</replaceable> [, ...]
by the containing role itself.)
</para>
<para>
<command>GRANT</> and <command>REVOKE</> can also be done by a role
that is not the owner of the affected object, but is a member of the role
that owns the object, or is a member of a role that holds privileges
<literal>WITH GRANT OPTION</literal> on the object. In this case the
privileges will be recorded as having been granted by the role that
actually owns the object or holds the privileges
<literal>WITH GRANT OPTION</literal>. For example, if table
<literal>t1</> is owned by role <literal>g1</>, of which role
<literal>u1</> is a member, then <literal>u1</> can grant privileges
on <literal>t1</> to <literal>u2</>, but those privileges will appear
to have been granted directly by <literal>g1</>. Any other member
of role <literal>g1</> could revoke them later.
</para>
<para>
If the role executing <command>GRANT</> holds the required privileges
indirectly via more than one role membership path, it is unspecified
which containing role will be recorded as having done the grant. In such
cases it is best practice to use <command>SET ROLE</> to become the
specific role you want to do the <command>GRANT</> as.
</para>
<para>
Currently, <productname>PostgreSQL</productname> does not support
granting or revoking privileges for individual columns of a table.

27
doc/src/sgml/ref/revoke.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/revoke.sgml,v 1.34 2005/07/26 23:24:02 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/revoke.sgml,v 1.35 2005/10/20 19:18:01 tgl Exp $
PostgreSQL documentation
-->
@ -158,6 +158,31 @@ REVOKE [ ADMIN OPTION FOR ]
it is possible for a superuser to revoke all privileges, but this may
require use of <literal>CASCADE</literal> as stated above.
</para>
<para>
<command>REVOKE</> can also be done by a role
that is not the owner of the affected object, but is a member of the role
that owns the object, or is a member of a role that holds privileges
<literal>WITH GRANT OPTION</literal> on the object. In this case the
command is performed as though it were issued by the containing role that
actually owns the object or holds the privileges
<literal>WITH GRANT OPTION</literal>. For example, if table
<literal>t1</> is owned by role <literal>g1</>, of which role
<literal>u1</> is a member, then <literal>u1</> can revoke privileges
on <literal>t1</> that are recorded as being granted by <literal>g1</>.
This would include grants made by <literal>u1</> as well as by other
members of role <literal>g1</>.
</para>
<para>
If the role executing <command>REVOKE</> holds privileges
indirectly via more than one role membership path, it is unspecified
which containing role will be used to perform the command. In such cases
it is best practice to use <command>SET ROLE</> to become the specific
role you want to do the <command>REVOKE</> as. Failure to do so may
lead to revoking privileges other than the ones you intended, or not
revoking anything at all.
</para>
</refsect1>
<refsect1 id="SQL-REVOKE-examples">

170
doc/src/sgml/user-manag.sgml
View File

@ -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.