Row-Level Security Policies (RLS)

Building on the updatable security-barrier views work, add the
ability to define policies on tables to limit the set of rows
which are returned from a query and which are allowed to be added
to a table.  Expressions defined by the policy for filtering are
added to the security barrier quals of the query, while expressions
defined to check records being added to a table are added to the
with-check options of the query.

New top-level commands are CREATE/ALTER/DROP POLICY and are
controlled by the table owner.  Row Security is able to be enabled
and disabled by the owner on a per-table basis using
ALTER TABLE .. ENABLE/DISABLE ROW SECURITY.

Per discussion, ROW SECURITY is disabled on tables by default and
must be enabled for policies on the table to be used.  If no
policies exist on a table with ROW SECURITY enabled, a default-deny
policy is used and no records will be visible.

By default, row security is applied at all times except for the
table owner and the superuser.  A new GUC, row_security, is added
which can be set to ON, OFF, or FORCE.  When set to FORCE, row
security will be applied even for the table owner and superusers.
When set to OFF, row security will be disabled when allowed and an
error will be thrown if the user does not have rights to bypass row
security.

Per discussion, pg_dump sets row_security = OFF by default to ensure
that exports and backups will have all data in the table or will
error if there are insufficient privileges to bypass row security.
A new option has been added to pg_dump, --enable-row-security, to
ask pg_dump to export with row security enabled.

A new role capability, BYPASSRLS, which can only be set by the
superuser, is added to allow other users to be able to bypass row
security using row_security = OFF.

Many thanks to the various individuals who have helped with the
design, particularly Robert Haas for his feedback.

Authors include Craig Ringer, KaiGai Kohei, Adam Brightwell, Dean
Rasheed, with additional changes and rework by me.

Reviewers have included all of the above, Greg Smith,
Jeff McCormick, and Robert Haas.

1 files changed, 13 insertions, 5 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 01eda70f054..a546292da6e 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -501,6 +501,12 @@ ExecutorRewind(QueryDesc *queryDesc)
  *
  * Returns true if permissions are adequate.  Otherwise, throws an appropriate
  * error if ereport_on_violation is true, or simply returns false otherwise.
+ *
+ * Note that this does NOT address row-level security policies (aka: RLS).  If
+ * rows will be returned to the user as a result of this permission check
+ * passing, then RLS also needs to be consulted (and check_enable_rls()).
+ *
+ * See rewrite/rowsecurity.c.
  */
 bool
 ExecCheckRTPerms(List *rangeTable, bool ereport_on_violation)
@@ -1660,15 +1666,17 @@ ExecWithCheckOptions(ResultRelInfo *resultRelInfo,
 
 		/*
 		 * WITH CHECK OPTION checks are intended to ensure that the new tuple
-		 * is visible in the view.  If the view's qual evaluates to NULL, then
-		 * the new tuple won't be included in the view.  Therefore we need to
-		 * tell ExecQual to return FALSE for NULL (the opposite of what we do
-		 * above for CHECK constraints).
+		 * is visible (in the case of a view) or that it passes the
+		 * 'with-check' policy (in the case of row security).
+		 * If the qual evaluates to NULL or FALSE, then the new tuple won't be
+		 * included in the view or doesn't pass the 'with-check' policy for the
+		 * table.  We need ExecQual to return FALSE for NULL to handle the view
+		 * case (the opposite of what we do above for CHECK constraints).
 		 */
 		if (!ExecQual((List *) wcoExpr, econtext, false))
 			ereport(ERROR,
 					(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
-				 errmsg("new row violates WITH CHECK OPTION for view \"%s\"",
+				 errmsg("new row violates WITH CHECK OPTION for \"%s\"",
 						wco->viewname),
 					 errdetail("Failing row contains %s.",
 							   ExecBuildSlotValueDescription(slot,