Create default roles

This creates an initial set of default roles which administrators may
use to grant access to, historically, superuser-only functions.  Using
these roles instead of granting superuser access reduces the number of
superuser roles required for a system.  Documention for each of the
default roles has been added to user-manag.sgml.

Bump catversion to 201604082, as we had a commit that bumped it to
201604081 and another that set it back to 201604071...

Reviews by José Luis Tallón and Robert Haas

doc/src/sgml/func.sgml

@@ -17454,7 +17454,8 @@ SELECT set_config('log_statement_stats', 'off', false);
         </entry>
        <entry><type>boolean</type></entry>
        <entry>Cancel a backend's current query.  This is also allowed if the
-        calling role is a member of the role whose backend is being canceled,
+        calling role is a member of the role whose backend is being canceled or
+        the calling role has been granted <literal>pg_signal_backend</literal>,
         however only superusers can cancel superuser backends.
         </entry>
       </row>
@@ -17478,8 +17479,9 @@ SELECT set_config('log_statement_stats', 'off', false);
         </entry>
        <entry><type>boolean</type></entry>
        <entry>Terminate a backend.  This is also allowed if the calling role
-        is a member of the role whose backend is being terminated, however only
-        superusers can terminate superuser backends.
+        is a member of the role whose backend is being terminated or the
+        calling role has been granted <literal>pg_signal_backend</literal>,
+        however only superusers can terminate superuser backends.
        </entry>
       </row>
      </tbody>

doc/src/sgml/user-manag.sgml

@@ -483,6 +483,57 @@ DROP ROLE doomed_role;
   </para>
  </sect1>
 
+ <sect1 id="default-roles">
+  <title>Default Roles</title>
+
+  <indexterm zone="default-roles">
+   <primary>role</>
+  </indexterm>
+
+  <para>
+   <productname>PostgreSQL</productname> provides a set of default roles
+   which provide access to certain, commonly needed, privileged capabilities
+   and information.  Administrators can GRANT these roles to users and/or
+   other roles in their environment, providing those users with access to
+   the specified capabilities and information.
+  </para>
+
+  <para>
+   The default roles are described in <xref linkend="default-roles-table">.
+   Note that the specific permissions for each of the default roles may
+   change in the future as additional capabilities are added.  Administrators
+   should monitor the release notes for changes.
+  </para>
+
+   <table tocentry="1" id="default-roles-table">
+    <title>Default Roles</title>
+    <tgroup cols="2">
+     <thead>
+      <row>
+       <entry>Role</entry>
+       <entry>Allowed Access</entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry>pg_signal_backend</entry>
+       <entry>Send signals to other backends (eg: cancel query, terminate).</entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+  <para>
+   Administrators can grant access to these roles to users using the GRANT
+   command:
+
+<programlisting>
+GRANT pg_signal_backend TO admin_user;
+</programlisting>
+  </para>
+
+ </sect1>
+
  <sect1 id="perm-functions">
   <title>Function and Trigger Security</title>
 

src/backend/utils/adt/misc.c

@@ -21,6 +21,7 @@
 #include <unistd.h>
 
 #include "access/sysattr.h"
+#include "catalog/pg_authid.h"
 #include "catalog/catalog.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_type.h"
@@ -244,7 +245,8 @@ pg_signal_backend(int pid, int sig)
 		return SIGNAL_BACKEND_NOSUPERUSER;
 
 	/* Users can signal backends they have role membership in. */
-	if (!has_privs_of_role(GetUserId(), proc->roleId))
+	if (!has_privs_of_role(GetUserId(), proc->roleId) &&
+		!has_privs_of_role(GetUserId(), DEFAULT_ROLE_SIGNAL_BACKENDID))
 		return SIGNAL_BACKEND_NOPERMISSION;
 
 	/*
@@ -290,7 +292,7 @@ pg_cancel_backend(PG_FUNCTION_ARGS)
 	if (r == SIGNAL_BACKEND_NOPERMISSION)
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 (errmsg("must be a member of the role whose query is being canceled"))));
+				 (errmsg("must be a member of the role whose query is being canceled or member of pg_signal_backend"))));
 
 	PG_RETURN_BOOL(r == SIGNAL_BACKEND_SUCCESS);
 }
@@ -314,7 +316,7 @@ pg_terminate_backend(PG_FUNCTION_ARGS)
 	if (r == SIGNAL_BACKEND_NOPERMISSION)
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 (errmsg("must be a member of the role whose process is being terminated"))));
+				 (errmsg("must be a member of the role whose process is being terminated or member of pg_signal_backend"))));
 
 	PG_RETURN_BOOL(r == SIGNAL_BACKEND_SUCCESS);
 }

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201604071
+#define CATALOG_VERSION_NO	201604082
 
 #endif

src/include/catalog/pg_authid.h

@@ -93,10 +93,16 @@ typedef FormData_pg_authid *Form_pg_authid;
  *
  * The uppercase quantities will be replaced at initdb time with
  * user choices.
+ *
+ * If adding new default roles or changing the OIDs below, be sure to add or
+ * update the #defines which follow as appropriate.
  * ----------------
  */
 DATA(insert OID = 10 ( "POSTGRES" t t t t t t t -1 _null_ _null_));
+DATA(insert OID = 4200 ( "pg_signal_backend" f t f f f f f -1 _null_ _null_));
+
+#define BOOTSTRAP_SUPERUSERID			10
 
-#define BOOTSTRAP_SUPERUSERID 10
+#define DEFAULT_ROLE_SIGNAL_BACKENDID	4200
 
 #endif   /* PG_AUTHID_H */

src/test/regress/expected/rolenames.out

@@ -824,6 +824,11 @@ ERROR:  role "pg_abcdef" is reserved
 DETAIL:  Cannot GRANT roles to a reserved role.
 SET ROLE pg_testrole; -- error
 ERROR:  invalid value for parameter "role": "pg_testrole"
+SET ROLE pg_signal_backend; --error
+ERROR:  invalid value for parameter "role": "pg_signal_backend"
+CREATE SCHEMA test_schema AUTHORIZATION pg_signal_backend; --error
+ERROR:  role "pg_signal_backend" is reserved
+DETAIL:  Cannot specify reserved role as owner.
 UPDATE pg_proc SET proacl = null WHERE proname LIKE 'testagg_';
 SELECT proname, proacl FROM pg_proc WHERE proname LIKE 'testagg_';
  proname  | proacl 

src/test/regress/sql/rolenames.sql

@@ -385,6 +385,8 @@ GRANT testrol0 TO pg_abc; -- error
 GRANT pg_abc TO pg_abcdef; -- error
 
 SET ROLE pg_testrole; -- error
+SET ROLE pg_signal_backend; --error
+CREATE SCHEMA test_schema AUTHORIZATION pg_signal_backend; --error
 
 UPDATE pg_proc SET proacl = null WHERE proname LIKE 'testagg_';
 SELECT proname, proacl FROM pg_proc WHERE proname LIKE 'testagg_';