/*

 * rewrite/rowsecurity.c

 *    Routines to support policies for row-level security (aka RLS).

 *

 * Policies in PostgreSQL provide a mechanism to limit what records are

 * returned to a user and what records a user is permitted to add to a table.

 *

 * Policies can be defined for specific roles, specific commands, or provided

 * by an extension.  Row security can also be enabled for a table without any

 * policies being explicitly defined, in which case a default-deny policy is

 * applied.

 *

 * Any part of the system which is returning records back to the user, or

 * which is accepting records from the user to add to a table, needs to

 * consider the policies associated with the table (if any).  For normal

 * queries, this is handled by calling get_row_security_policies() during

 * rewrite, for each RTE in the query.  This returns the expressions defined

 * by the table's policies as a list that is prepended to the securityQuals

 * list for the RTE.  For queries which modify the table, any WITH CHECK

 * clauses from the table's policies are also returned and prepended to the

 * list of WithCheckOptions for the Query to check each row that is being

 * added to the table.  Other parts of the system (eg: COPY) simply construct

 * a normal query and use that, if RLS is to be applied.

 *

 * The check to see if RLS should be enabled is provided through

 * check_enable_rls(), which returns an enum (defined in rowsecurity.h) to

 * indicate if RLS should be enabled (RLS_ENABLED), or bypassed (RLS_NONE or

 * RLS_NONE_ENV).  RLS_NONE_ENV indicates that RLS should be bypassed

 * in the current environment, but that may change if the row_security GUC or

 * the current role changes.

 *

 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 */

#include "postgres.h"

#include "access/table.h"

#include "catalog/pg_class.h"

#include "catalog/pg_type.h"

#include "miscadmin.h"

#include "nodes/makefuncs.h"

#include "nodes/pg_list.h"

#include "parser/parse_relation.h"

#include "rewrite/rewriteDefine.h"

#include "rewrite/rewriteManip.h"

#include "rewrite/rowsecurity.h"

#include "utils/acl.h"

#include "utils/rel.h"

#include "utils/rls.h"

static void get_policies_for_relation(Relation relation,

                    CmdType cmd, Oid user_id,

                    List **permissive_policies,

                    List **restrictive_policies);

static void sort_policies_by_name(List *policies);

static int  row_security_policy_cmp(const ListCell *a, const ListCell *b);

static void add_security_quals(int rt_index,

                 List *permissive_policies,

                 List *restrictive_policies,

                 List **securityQuals,

                 bool *hasSubLinks);

static void add_with_check_options(Relation rel,

                   int rt_index,

                   WCOKind kind,

                   List *permissive_policies,

                   List *restrictive_policies,

                   List **withCheckOptions,

                   bool *hasSubLinks,

                   bool force_using);

static bool check_role_for_policy(ArrayType *policy_roles, Oid user_id);

/*

 * hooks to allow extensions to add their own security policies

 *

 * row_security_policy_hook_permissive can be used to add policies which

 * are combined with the other permissive policies, using OR.

 *

 * row_security_policy_hook_restrictive can be used to add policies which

 * are enforced, regardless of other policies (they are combined using AND).

 */

row_security_policy_hook_type row_security_policy_hook_permissive = NULL;

row_security_policy_hook_type row_security_policy_hook_restrictive = NULL;

/*

 * Get any row security quals and WithCheckOption checks that should be

 * applied to the specified RTE.

 *

 * In addition, hasRowSecurity is set to true if row-level security is enabled

 * (even if this RTE doesn't have any row security quals), and hasSubLinks is

 * set to true if any of the quals returned contain sublinks.

 */

void

get_row_security_policies(Query *root, RangeTblEntry *rte, int rt_index,

              List **securityQuals, List **withCheckOptions,

              bool *hasRowSecurity, bool *hasSubLinks)

{

  Oid     user_id;

  int     rls_status;

  Relation  rel;

  CmdType   commandType;

  List     *permissive_policies;

  List     *restrictive_policies;

  RTEPermissionInfo *perminfo;

  /* Defaults for the return values */

  *securityQuals = NIL;

  *withCheckOptions = NIL;

  *hasRowSecurity = false;

  *hasSubLinks = false;

  Assert(rte->rtekind == RTE_RELATION);

  /* If this is not a normal relation, just return immediately */

  if (rte->relkind != RELKIND_RELATION &&

    rte->relkind != RELKIND_PARTITIONED_TABLE)

    return;

  perminfo = getRTEPermissionInfo(root->rteperminfos, rte);

  /* Switch to checkAsUser if it's set */

  user_id = OidIsValid(perminfo->checkAsUser) ?

    perminfo->checkAsUser : GetUserId();

  /* Determine the state of RLS for this, pass checkAsUser explicitly */

  rls_status = check_enable_rls(rte->relid, perminfo->checkAsUser, false);

  /* If there is no RLS on this table at all, nothing to do */

  if (rls_status == RLS_NONE)

    return;

  /*

   * RLS_NONE_ENV means we are not doing any RLS now, but that may change

   * with changes to the environment, so we mark it as hasRowSecurity to

   * force a re-plan when the environment changes.

   */

  if (rls_status == RLS_NONE_ENV)

  {

    /*

     * Indicate that this query may involve RLS and must therefore be

     * replanned if the environment changes (GUCs, role), but we are not

     * adding anything here.

     */

    *hasRowSecurity = true;

    return;

  }

  /*

   * RLS is enabled for this relation.

   *

   * Get the security policies that should be applied, based on the command

   * type.  Note that if this isn't the target relation, we actually want

   * the relation's SELECT policies, regardless of the query command type,

   * for example in UPDATE t1 ... FROM t2 we need to apply t1's UPDATE

   * policies and t2's SELECT policies.

   */

  rel = table_open(rte->relid, NoLock);

  commandType = rt_index == root->resultRelation ?

    root->commandType : CMD_SELECT;

  /*

   * In some cases, we need to apply USING policies (which control the

   * visibility of records) associated with multiple command types (see

   * specific cases below).

   *

   * When considering the order in which to apply these USING policies, we

   * prefer to apply higher privileged policies, those which allow the user

   * to lock records (UPDATE and DELETE), first, followed by policies which

   * don't (SELECT).

   *

   * Note that the optimizer is free to push down and reorder quals which

   * use leakproof functions.

   *

   * In all cases, if there are no policy clauses allowing access to rows in

   * the table for the specific type of operation, then a single

   * always-false clause (a default-deny policy) will be added (see

   * add_security_quals).

   */

  /*

   * For a SELECT, if UPDATE privileges are required (eg: the user has

   * specified FOR [KEY] UPDATE/SHARE), then add the UPDATE USING quals

   * first.

   *

   * This way, we filter out any records from the SELECT FOR SHARE/UPDATE

   * which the user does not have access to via the UPDATE USING policies,

   * similar to how we require normal UPDATE rights for these queries.

   */

  if (commandType == CMD_SELECT && perminfo->requiredPerms & ACL_UPDATE)

  {

    List     *update_permissive_policies;

    List     *update_restrictive_policies;

    get_policies_for_relation(rel, CMD_UPDATE, user_id,

                  &update_permissive_policies,

                  &update_restrictive_policies);

    add_security_quals(rt_index,

               update_permissive_policies,

               update_restrictive_policies,

               securityQuals,

               hasSubLinks);

  }

  /*

   * For SELECT, UPDATE and DELETE, add security quals to enforce the USING

   * policies.  These security quals control access to existing table rows.

   * Restrictive policies are combined together using AND, and permissive

   * policies are combined together using OR.

   */

  get_policies_for_relation(rel, commandType, user_id, &permissive_policies,

                &restrictive_policies);

  if (commandType == CMD_SELECT ||

    commandType == CMD_UPDATE ||

    commandType == CMD_DELETE)

    add_security_quals(rt_index,

               permissive_policies,

               restrictive_policies,

               securityQuals,

               hasSubLinks);

  /*

   * Similar to above, during an UPDATE, DELETE, or MERGE, if SELECT rights

   * are also required (eg: when a RETURNING clause exists, or the user has

   * provided a WHERE clause which involves columns from the relation), we

   * collect up CMD_SELECT policies and add them via add_security_quals

   * first.

   *

   * This way, we filter out any records which are not visible through an

   * ALL or SELECT USING policy.

   */

  if ((commandType == CMD_UPDATE || commandType == CMD_DELETE ||

     commandType == CMD_MERGE) &&

    perminfo->requiredPerms & ACL_SELECT)

  {

    List     *select_permissive_policies;

    List     *select_restrictive_policies;

    get_policies_for_relation(rel, CMD_SELECT, user_id,

                  &select_permissive_policies,

                  &select_restrictive_policies);

    add_security_quals(rt_index,

               select_permissive_policies,

               select_restrictive_policies,

               securityQuals,

               hasSubLinks);

  }

  /*

   * For INSERT and UPDATE, add withCheckOptions to verify that any new

   * records added are consistent with the security policies.  This will use

   * each policy's WITH CHECK clause, or its USING clause if no explicit

   * WITH CHECK clause is defined.

   */

  if (commandType == CMD_INSERT || commandType == CMD_UPDATE)

  {

    /* This should be the target relation */

    Assert(rt_index == root->resultRelation);

    add_with_check_options(rel, rt_index,

                 commandType == CMD_INSERT ?

                 WCO_RLS_INSERT_CHECK : WCO_RLS_UPDATE_CHECK,

                 permissive_policies,

                 restrictive_policies,

                 withCheckOptions,

                 hasSubLinks,

                 false);

    /*

     * Get and add ALL/SELECT policies, if SELECT rights are required for

     * this relation (eg: when RETURNING is used).  These are added as WCO

     * policies rather than security quals to ensure that an error is

     * raised if a policy is violated; otherwise, we might end up silently

     * dropping rows to be added.

     */

    if (perminfo->requiredPerms & ACL_SELECT)

    {

      List     *select_permissive_policies = NIL;

      List     *select_restrictive_policies = NIL;

      get_policies_for_relation(rel, CMD_SELECT, user_id,

                    &select_permissive_policies,

                    &select_restrictive_policies);

      add_with_check_options(rel, rt_index,

                   commandType == CMD_INSERT ?

                   WCO_RLS_INSERT_CHECK : WCO_RLS_UPDATE_CHECK,

                   select_permissive_policies,

                   select_restrictive_policies,

                   withCheckOptions,

                   hasSubLinks,

                   true);

    }

    /*

     * For INSERT ... ON CONFLICT DO UPDATE we need additional policy

     * checks for the UPDATE which may be applied to the same RTE.

     */

    if (commandType == CMD_INSERT &&

      root->onConflict && root->onConflict->action == ONCONFLICT_UPDATE)

    {

      List     *conflict_permissive_policies;

      List     *conflict_restrictive_policies;

      List     *conflict_select_permissive_policies = NIL;

      List     *conflict_select_restrictive_policies = NIL;

      /* Get the policies that apply to the auxiliary UPDATE */

      get_policies_for_relation(rel, CMD_UPDATE, user_id,

                    &conflict_permissive_policies,

                    &conflict_restrictive_policies);

      /*

       * Enforce the USING clauses of the UPDATE policies using WCOs

       * rather than security quals.  This ensures that an error is

       * raised if the conflicting row cannot be updated due to RLS,

       * rather than the change being silently dropped.

       */

      add_with_check_options(rel, rt_index,

                   WCO_RLS_CONFLICT_CHECK,

                   conflict_permissive_policies,

                   conflict_restrictive_policies,

                   withCheckOptions,

                   hasSubLinks,

                   true);

      /*

       * Get and add ALL/SELECT policies, as WCO_RLS_CONFLICT_CHECK WCOs

       * to ensure they are considered when taking the UPDATE path of an

       * INSERT .. ON CONFLICT DO UPDATE, if SELECT rights are required

       * for this relation, also as WCO policies, again, to avoid

       * silently dropping data.  See above.

       */

      if (perminfo->requiredPerms & ACL_SELECT)

      {

        get_policies_for_relation(rel, CMD_SELECT, user_id,

                      &conflict_select_permissive_policies,

                      &conflict_select_restrictive_policies);

        add_with_check_options(rel, rt_index,

                     WCO_RLS_CONFLICT_CHECK,

                     conflict_select_permissive_policies,

                     conflict_select_restrictive_policies,

                     withCheckOptions,

                     hasSubLinks,

                     true);

      }

      /* Enforce the WITH CHECK clauses of the UPDATE policies */

      add_with_check_options(rel, rt_index,

                   WCO_RLS_UPDATE_CHECK,

                   conflict_permissive_policies,

                   conflict_restrictive_policies,

                   withCheckOptions,

                   hasSubLinks,

                   false);

      /*

       * Add ALL/SELECT policies as WCO_RLS_UPDATE_CHECK WCOs, to ensure

       * that the final updated row is visible when taking the UPDATE

       * path of an INSERT .. ON CONFLICT DO UPDATE, if SELECT rights

       * are required for this relation.

       */

      if (perminfo->requiredPerms & ACL_SELECT)

        add_with_check_options(rel, rt_index,

                     WCO_RLS_UPDATE_CHECK,

                     conflict_select_permissive_policies,

                     conflict_select_restrictive_policies,

                     withCheckOptions,

                     hasSubLinks,

                     true);

    }

  }

  /*

   * FOR MERGE, we fetch policies for UPDATE, DELETE and INSERT (and ALL)

   * and set them up so that we can enforce the appropriate policy depending

   * on the final action we take.

   *

   * We already fetched the SELECT policies above, to check existing rows,

   * but we must also check that new rows created by INSERT/UPDATE actions

   * are visible, if SELECT rights are required. For INSERT actions, we only

   * do this if RETURNING is specified, to be consistent with a plain INSERT

   * command, which can only require SELECT rights when RETURNING is used.

   *

   * We don't push the UPDATE/DELETE USING quals to the RTE because we don't

   * really want to apply them while scanning the relation since we don't

   * know whether we will be doing an UPDATE or a DELETE at the end. We

   * apply the respective policy once we decide the final action on the

   * target tuple.

   *

   * XXX We are setting up USING quals as WITH CHECK. If RLS prohibits

   * UPDATE/DELETE on the target row, we shall throw an error instead of

   * silently ignoring the row. This is different than how normal

   * UPDATE/DELETE works and more in line with INSERT ON CONFLICT DO UPDATE

   * handling.

   */

  if (commandType == CMD_MERGE)

  {

    List     *merge_update_permissive_policies;

    List     *merge_update_restrictive_policies;

    List     *merge_delete_permissive_policies;

    List     *merge_delete_restrictive_policies;

    List     *merge_insert_permissive_policies;

    List     *merge_insert_restrictive_policies;

    List     *merge_select_permissive_policies = NIL;

    List     *merge_select_restrictive_policies = NIL;

    /*

     * Fetch the UPDATE policies and set them up to execute on the

     * existing target row before doing UPDATE.

     */

    get_policies_for_relation(rel, CMD_UPDATE, user_id,

                  &merge_update_permissive_policies,

                  &merge_update_restrictive_policies);

    /*

     * WCO_RLS_MERGE_UPDATE_CHECK is used to check UPDATE USING quals on

     * the existing target row.

     */

    add_with_check_options(rel, rt_index,

                 WCO_RLS_MERGE_UPDATE_CHECK,

                 merge_update_permissive_policies,

                 merge_update_restrictive_policies,

                 withCheckOptions,

                 hasSubLinks,

                 true);

    /* Enforce the WITH CHECK clauses of the UPDATE policies */

    add_with_check_options(rel, rt_index,

                 WCO_RLS_UPDATE_CHECK,

                 merge_update_permissive_policies,

                 merge_update_restrictive_policies,

                 withCheckOptions,

                 hasSubLinks,

                 false);

    /*

     * Add ALL/SELECT policies as WCO_RLS_UPDATE_CHECK WCOs, to ensure

     * that the updated row is visible when executing an UPDATE action, if

     * SELECT rights are required for this relation.

     */

    if (perminfo->requiredPerms & ACL_SELECT)

    {

      get_policies_for_relation(rel, CMD_SELECT, user_id,

                    &merge_select_permissive_policies,

                    &merge_select_restrictive_policies);

      add_with_check_options(rel, rt_index,

                   WCO_RLS_UPDATE_CHECK,

                   merge_select_permissive_policies,

                   merge_select_restrictive_policies,

                   withCheckOptions,

                   hasSubLinks,

                   true);

    }

    /*

     * Fetch the DELETE policies and set them up to execute on the

     * existing target row before doing DELETE.

     */

    get_policies_for_relation(rel, CMD_DELETE, user_id,

                  &merge_delete_permissive_policies,

                  &merge_delete_restrictive_policies);

    /*

     * WCO_RLS_MERGE_DELETE_CHECK is used to check DELETE USING quals on

     * the existing target row.

     */

    add_with_check_options(rel, rt_index,

                 WCO_RLS_MERGE_DELETE_CHECK,

                 merge_delete_permissive_policies,

                 merge_delete_restrictive_policies,

                 withCheckOptions,

                 hasSubLinks,

                 true);

    /*

     * No special handling is required for INSERT policies. They will be

     * checked and enforced during ExecInsert(). But we must add them to

     * withCheckOptions.

     */

    get_policies_for_relation(rel, CMD_INSERT, user_id,

                  &merge_insert_permissive_policies,

                  &merge_insert_restrictive_policies);

    add_with_check_options(rel, rt_index,

                 WCO_RLS_INSERT_CHECK,

                 merge_insert_permissive_policies,

                 merge_insert_restrictive_policies,

                 withCheckOptions,

                 hasSubLinks,

                 false);

    /*

     * Add ALL/SELECT policies as WCO_RLS_INSERT_CHECK WCOs, to ensure

     * that the inserted row is visible when executing an INSERT action,

     * if RETURNING is specified and SELECT rights are required for this

     * relation.

     */

    if (perminfo->requiredPerms & ACL_SELECT && root->returningList)

      add_with_check_options(rel, rt_index,

                   WCO_RLS_INSERT_CHECK,

                   merge_select_permissive_policies,

                   merge_select_restrictive_policies,

                   withCheckOptions,

                   hasSubLinks,

                   true);

  }

  table_close(rel, NoLock);

  /*

   * Copy checkAsUser to the row security quals and WithCheckOption checks,

   * in case they contain any subqueries referring to other relations.

   */

  setRuleCheckAsUser((Node *) *securityQuals, perminfo->checkAsUser);

  setRuleCheckAsUser((Node *) *withCheckOptions, perminfo->checkAsUser);

  /*

   * Mark this query as having row security, so plancache can invalidate it

   * when necessary (eg: role changes)

   */

  *hasRowSecurity = true;

}

/*

 * get_policies_for_relation

 *

 * Returns lists of permissive and restrictive policies to be applied to the

 * specified relation, based on the command type and role.

 *

 * This includes any policies added by extensions.

 */

static void

get_policies_for_relation(Relation relation, CmdType cmd, Oid user_id,

              List **permissive_policies,

              List **restrictive_policies)

{

  ListCell   *item;

  *permissive_policies = NIL;

  *restrictive_policies = NIL;

  /* First find all internal policies for the relation. */

  foreach(item, relation->rd_rsdesc->policies)

  {

    bool    cmd_matches = false;

    RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

    /* Always add ALL policies, if they exist. */

    if (policy->polcmd == '*')

      cmd_matches = true;

    else

    {

      /* Check whether the policy applies to the specified command type */

      switch (cmd)

      {

        case CMD_SELECT:

          if (policy->polcmd == ACL_SELECT_CHR)

            cmd_matches = true;

          break;

        case CMD_INSERT:

          if (policy->polcmd == ACL_INSERT_CHR)

            cmd_matches = true;

          break;

        case CMD_UPDATE:

          if (policy->polcmd == ACL_UPDATE_CHR)

            cmd_matches = true;

          break;

        case CMD_DELETE:

          if (policy->polcmd == ACL_DELETE_CHR)

            cmd_matches = true;

          break;

        case CMD_MERGE:

          /*

           * We do not support a separate policy for MERGE command.

           * Instead it derives from the policies defined for other

           * commands.

           */

          break;

        default:

          elog(ERROR, "unrecognized policy command type %d",

             (int) cmd);

          break;

      }

    }

    /*

     * Add this policy to the relevant list of policies if it applies to

     * the specified role.

     */

    if (cmd_matches && check_role_for_policy(policy->roles, user_id))

    {

      if (policy->permissive)

        *permissive_policies = lappend(*permissive_policies, policy);

      else

        *restrictive_policies = lappend(*restrictive_policies, policy);

    }

  }

  /*

   * We sort restrictive policies by name so that any WCOs they generate are

   * checked in a well-defined order.

   */

  sort_policies_by_name(*restrictive_policies);

  /*

   * Then add any permissive or restrictive policies defined by extensions.

   * These are simply appended to the lists of internal policies, if they

   * apply to the specified role.

   */

  if (row_security_policy_hook_restrictive)

  {

    List     *hook_policies =

      (*row_security_policy_hook_restrictive) (cmd, relation);

    /*

     * As with built-in restrictive policies, we sort any hook-provided

     * restrictive policies by name also.  Note that we also intentionally

     * always check all built-in restrictive policies, in name order,

     * before checking restrictive policies added by hooks, in name order.

     */

    sort_policies_by_name(hook_policies);

    foreach(item, hook_policies)

    {

      RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

      if (check_role_for_policy(policy->roles, user_id))

        *restrictive_policies = lappend(*restrictive_policies, policy);

    }

  }

  if (row_security_policy_hook_permissive)

  {

    List     *hook_policies =

      (*row_security_policy_hook_permissive) (cmd, relation);

    foreach(item, hook_policies)

    {

      RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

      if (check_role_for_policy(policy->roles, user_id))

        *permissive_policies = lappend(*permissive_policies, policy);

    }

  }

}

/*

 * sort_policies_by_name

 *

 * This is only used for restrictive policies, ensuring that any

 * WithCheckOptions they generate are applied in a well-defined order.

 * This is not necessary for permissive policies, since they are all combined

 * together using OR into a single WithCheckOption check.

 */

static void

sort_policies_by_name(List *policies)

{

  list_sort(policies, row_security_policy_cmp);

}

/*

 * list_sort comparator to sort RowSecurityPolicy entries by name

 */

static int

row_security_policy_cmp(const ListCell *a, const ListCell *b)

{

  const RowSecurityPolicy *pa = (const RowSecurityPolicy *) lfirst(a);

  const RowSecurityPolicy *pb = (const RowSecurityPolicy *) lfirst(b);

  /* Guard against NULL policy names from extensions */

  if (pa->policy_name == NULL)

    return pb->policy_name == NULL ? 0 : 1;

  if (pb->policy_name == NULL)

    return -1;

  return strcmp(pa->policy_name, pb->policy_name);

}

/*

 * add_security_quals

 *

 * Add security quals to enforce the specified RLS policies, restricting

 * access to existing data in a table.  If there are no policies controlling

 * access to the table, then all access is prohibited --- i.e., an implicit

 * default-deny policy is used.

 *

 * New security quals are added to securityQuals, and hasSubLinks is set to

 * true if any of the quals added contain sublink subqueries.

 */

static void

add_security_quals(int rt_index,

           List *permissive_policies,

           List *restrictive_policies,

           List **securityQuals,

           bool *hasSubLinks)

{

  ListCell   *item;

  List     *permissive_quals = NIL;

  Expr     *rowsec_expr;

  /*

   * First collect up the permissive quals.  If we do not find any

   * permissive policies then no rows are visible (this is handled below).

   */

  foreach(item, permissive_policies)

  {

    RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

    if (policy->qual != NULL)

    {

      permissive_quals = lappend(permissive_quals,

                     copyObject(policy->qual));

      *hasSubLinks |= policy->hassublinks;

    }

  }

  /*

   * We must have permissive quals, always, or no rows are visible.

   *

   * If we do not, then we simply return a single 'false' qual which results

   * in no rows being visible.

   */

  if (permissive_quals != NIL)

  {

    /*

     * We now know that permissive policies exist, so we can now add

     * security quals based on the USING clauses from the restrictive

     * policies.  Since these need to be combined together using AND, we

     * can just add them one at a time.

     */

    foreach(item, restrictive_policies)

    {

      RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

      Expr     *qual;

      if (policy->qual != NULL)

      {

        qual = copyObject(policy->qual);

        ChangeVarNodes((Node *) qual, 1, rt_index, 0);

        *securityQuals = list_append_unique(*securityQuals, qual);

        *hasSubLinks |= policy->hassublinks;

      }

    }

    /*

     * Then add a single security qual combining together the USING

     * clauses from all the permissive policies using OR.

     */

    if (list_length(permissive_quals) == 1)

      rowsec_expr = (Expr *) linitial(permissive_quals);

    else

      rowsec_expr = makeBoolExpr(OR_EXPR, permissive_quals, -1);

    ChangeVarNodes((Node *) rowsec_expr, 1, rt_index, 0);

    *securityQuals = list_append_unique(*securityQuals, rowsec_expr);

  }

  else

    /*

     * A permissive policy must exist for rows to be visible at all.

     * Therefore, if there were no permissive policies found, return a

     * single always-false clause.

     */

    *securityQuals = lappend(*securityQuals,

                 makeConst(BOOLOID, -1, InvalidOid,

                       sizeof(bool), BoolGetDatum(false),

                       false, true));

}

/*

 * add_with_check_options

 *

 * Add WithCheckOptions of the specified kind to check that new records

 * added by an INSERT or UPDATE are consistent with the specified RLS

 * policies.  Normally new data must satisfy the WITH CHECK clauses from the

 * policies.  If a policy has no explicit WITH CHECK clause, its USING clause

 * is used instead.  In the special case of an UPDATE arising from an

 * INSERT ... ON CONFLICT DO UPDATE, existing records are first checked using

 * a WCO_RLS_CONFLICT_CHECK WithCheckOption, which always uses the USING

 * clauses from RLS policies.

 *

 * New WCOs are added to withCheckOptions, and hasSubLinks is set to true if

 * any of the check clauses added contain sublink subqueries.

 */

static void

add_with_check_options(Relation rel,

             int rt_index,

             WCOKind kind,

             List *permissive_policies,

             List *restrictive_policies,

             List **withCheckOptions,

             bool *hasSubLinks,

             bool force_using)

{

  ListCell   *item;

  List     *permissive_quals = NIL;

#define QUAL_FOR_WCO(policy) \

  ( !force_using && \

    (policy)->with_check_qual != NULL ? \

    (policy)->with_check_qual : (policy)->qual )

  /*

   * First collect up the permissive policy clauses, similar to

   * add_security_quals.

   */

  foreach(item, permissive_policies)

  {

    RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

    Expr     *qual = QUAL_FOR_WCO(policy);

    if (qual != NULL)

    {

      permissive_quals = lappend(permissive_quals, copyObject(qual));

      *hasSubLinks |= policy->hassublinks;

    }

  }

  /*

   * There must be at least one permissive qual found or no rows are allowed

   * to be added.  This is the same as in add_security_quals.

   *

   * If there are no permissive_quals then we fall through and return a

   * single 'false' WCO, preventing all new rows.

   */

  if (permissive_quals != NIL)

  {

    /*

     * Add a single WithCheckOption for all the permissive policy clauses,

     * combining them together using OR.  This check has no policy name,

     * since if the check fails it means that no policy granted permission

     * to perform the update, rather than any particular policy being

     * violated.

     */

    WithCheckOption *wco;

    wco = makeNode(WithCheckOption);

    wco->kind = kind;

    wco->relname = pstrdup(RelationGetRelationName(rel));

    wco->polname = NULL;

    wco->cascaded = false;

    if (list_length(permissive_quals) == 1)

      wco->qual = (Node *) linitial(permissive_quals);

    else

      wco->qual = (Node *) makeBoolExpr(OR_EXPR, permissive_quals, -1);

    ChangeVarNodes(wco->qual, 1, rt_index, 0);

    *withCheckOptions = list_append_unique(*withCheckOptions, wco);

    /*

     * Now add WithCheckOptions for each of the restrictive policy clauses

     * (which will be combined together using AND).  We use a separate

     * WithCheckOption for each restrictive policy to allow the policy

     * name to be included in error reports if the policy is violated.

     */

    foreach(item, restrictive_policies)

    {

      RowSecurityPolicy *policy = (RowSecurityPolicy *) lfirst(item);

      Expr     *qual = QUAL_FOR_WCO(policy);

      if (qual != NULL)

      {

        qual = copyObject(qual);

        ChangeVarNodes((Node *) qual, 1, rt_index, 0);

        wco = makeNode(WithCheckOption);

        wco->kind = kind;

        wco->relname = pstrdup(RelationGetRelationName(rel));

        wco->polname = pstrdup(policy->policy_name);

        wco->qual = (Node *) qual;

        wco->cascaded = false;

        *withCheckOptions = list_append_unique(*withCheckOptions, wco);

        *hasSubLinks |= policy->hassublinks;

      }

    }

  }

  else

  {

    /*

     * If there were no policy clauses to check new data, add a single

     * always-false WCO (a default-deny policy).

     */

    WithCheckOption *wco;

    wco = makeNode(WithCheckOption);

    wco->kind = kind;

    wco->relname = pstrdup(RelationGetRelationName(rel));

    wco->polname = NULL;

    wco->qual = (Node *) makeConst(BOOLOID, -1, InvalidOid,

                     sizeof(bool), BoolGetDatum(false),

                     false, true);

    wco->cascaded = false;

    *withCheckOptions = lappend(*withCheckOptions, wco);

  }

}

/*

 * check_role_for_policy -

 *   determines if the policy should be applied for the current role

 */

static bool

check_role_for_policy(ArrayType *policy_roles, Oid user_id)

{

  int     i;

  Oid      *roles = (Oid *) ARR_DATA_PTR(policy_roles);

  /* Quick fall-thru for policies applied to all roles */

  if (roles[0] == ACL_ID_PUBLIC)

    return true;

  for (i = 0; i < ARR_DIMS(policy_roles)[0]; i++)

  {

    if (has_privs_of_role(user_id, roles[i]))

      return true;

  }

  return false;

}