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<refentry id="SQL-SECURITY-LABEL">
 <refmeta>
  <refentrytitle>SECURITY LABEL</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>SECURITY LABEL</refname>
  <refpurpose>define or change a security label applied to an object</refpurpose>
 </refnamediv>

 <indexterm zone="sql-security-label">
  <primary>SECURITY LABEL</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
SECURITY LABEL [ FOR <replaceable class="PARAMETER">provider</replaceable> ] ON
{
  TABLE <replaceable class="PARAMETER">object_name</replaceable> |
  COLUMN <replaceable class="PARAMETER">table_name</replaceable>.<replaceable class="PARAMETER">column_name</replaceable> |
  AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable class="PARAMETER">agg_type</replaceable> [, ...] ) |
  DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) |
  LARGE OBJECT <replaceable class="PARAMETER">large_object_oid</replaceable> |
  [ PROCEDURAL ] LANGUAGE <replaceable class="PARAMETER">object_name</replaceable> |
  SCHEMA <replaceable class="PARAMETER">object_name</replaceable> |
  SEQUENCE <replaceable class="PARAMETER">object_name</replaceable> |
  TYPE <replaceable class="PARAMETER">object_name</replaceable> |
  VIEW <replaceable class="PARAMETER">object_name</replaceable>
} IS '<replaceable class="PARAMETER">label</replaceable>'
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>SECURITY LABEL</command> applies a security label to a database
   object.  An arbitrary number of security labels, one per label provider, can
   be associated with a given database object.  Label providers are loadable
   modules which register themselves by using the function
   <function>register_label_provider</>.
  </para>

  <note>
    <para>
      <function>register_label_provider</> is not an SQL function; it can
      only be called from C code loaded into the backend.
    </para>
  </note>

  <para>
   The label provider determines whether a given a label is valid and whether
   it is permissible to assign that label to a given object.  The meaning of a
   given label is likewise at the discretion of the label provider.
   <productname>PostgreSQL</> places no restrictions on whether or how a
   label provider must interpret security labels; it merely provides a
   mechanism for storing them.  In practice, this facility is intended to allow
   integration with label-based mandatory access control (MAC) systems such as
   <productname>SE-Linux</>.  Such systems make all access control decisions
   based on object labels, rather than traditional discretionary access control
   (DAC) concepts such as users and groups.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">object_name</replaceable></term>
    <term><replaceable class="parameter">table_name.column_name</replaceable></term>
    <term><replaceable class="parameter">agg_name</replaceable></term>
    <term><replaceable class="parameter">function_name</replaceable></term>
    <listitem>
     <para>
      The name of the object to be commented.  Names of tables,
      aggregates, domains, functions, sequences, types, and views can
      be schema-qualified.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">provider</replaceable></term>
    <listitem>
     <para>
      The name of the provider with which this label is to be associated.  The
      named provider must be loaded and must consent to the proposed labeling
      operation.  If exactly one provider is loaded, the provider name may be
      omitted for brevity.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">arg_type</replaceable></term>
    <listitem>
     <para>
      An input data type on which the aggregate function operates.
      To reference a zero-argument aggregate function, write <literal>*</>
      in place of the list of input data types.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argmode</replaceable></term>

    <listitem>
     <para>
      The mode of a function argument: <literal>IN</>, <literal>OUT</>,
      <literal>INOUT</>, or <literal>VARIADIC</>.
      If omitted, the default is <literal>IN</>.
      Note that <command>COMMENT ON FUNCTION</command> does not actually pay
      any attention to <literal>OUT</> arguments, since only the input
      arguments are needed to determine the function's identity.
      So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
      and <literal>VARIADIC</> arguments.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argname</replaceable></term>

    <listitem>
     <para>
      The name of a function argument.
      Note that <command>COMMENT ON FUNCTION</command> does not actually pay
      any attention to argument names, since only the argument data
      types are needed to determine the function's identity.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argtype</replaceable></term>

    <listitem>
     <para>
      The data type(s) of the function's arguments (optionally 
      schema-qualified), if any.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">large_object_oid</replaceable></term>
    <listitem>
     <para>
      The OID of the large object.
     </para>
    </listitem>
   </varlistentry>

    <varlistentry>
     <term><literal>PROCEDURAL</literal></term>

     <listitem>
      <para>
       This is a noise word.
      </para>
     </listitem>
    </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">label</replaceable></term>
    <listitem>
     <para>
      The new security label, written as a string literal; or <literal>NULL</>
      to drop the security label.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   The following example shows how the security label of a table might
   be changed.

<programlisting>
SECURITY LABEL FOR selinux ON TABLE mytable IS 'system_u:object_r:sepgsql_table_t:s0';
</programlisting>
  </para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>
  <para>
   There is no <command>SECURITY LABEL</command> command in the SQL standard.
  </para>
 </refsect1>
</refentry>
