Merge similar algorithms into roles_is_member_of().

The next commit would have complicated two or three algorithms, so take
this opportunity to consolidate.  No functional changes.

Reviewed by John Naylor.

Discussion: https://postgr.es/m/20201228043148.GA1053024@rfd.leadboat.com

Author: nmisch

src/backend/utils/adt/acl.c

@@ -50,32 +50,24 @@ typedef struct
 /*
  * We frequently need to test whether a given role is a member of some other
  * role.  In most of these tests the "given role" is the same, namely the
- * active current user.  So we can optimize it by keeping a cached list of
- * all the roles the "given role" is a member of, directly or indirectly.
- *
- * There are actually two caches, one computed under "has_privs" rules
- * (do not recurse where rolinherit isn't true) and one computed under
- * "is_member" rules (recurse regardless of rolinherit).
+ * active current user.  So we can optimize it by keeping cached lists of all
+ * the roles the "given role" is a member of, directly or indirectly.
  *
  * Possibly this mechanism should be generalized to allow caching membership
  * info for multiple roles?
  *
- * The has_privs cache is:
- * cached_privs_role is the role OID the cache is for.
- * cached_privs_roles is an OID list of roles that cached_privs_role
- *		has the privileges of (always including itself).
- * The cache is valid if cached_privs_role is not InvalidOid.
- *
- * The is_member cache is similarly:
- * cached_member_role is the role OID the cache is for.
- * cached_membership_roles is an OID list of roles that cached_member_role
- *		is a member of (always including itself).
- * The cache is valid if cached_member_role is not InvalidOid.
+ * Each element of cached_roles is an OID list of constituent roles for the
+ * corresponding element of cached_role (always including the cached_role
+ * itself).  One cache has ROLERECURSE_PRIVS semantics, and the other has
+ * ROLERECURSE_MEMBERS semantics.
  */
-static Oid	cached_privs_role = InvalidOid;
-static List *cached_privs_roles = NIL;
-static Oid	cached_member_role = InvalidOid;
-static List *cached_membership_roles = NIL;
+enum RoleRecurseType
+{
+	ROLERECURSE_PRIVS = 0,		/* recurse if rolinherit */
+	ROLERECURSE_MEMBERS = 1		/* recurse unconditionally */
+};
+static Oid	cached_role[] = {InvalidOid, InvalidOid};
+static List *cached_roles[] = {NIL, NIL};
 
 
 static const char *getid(const char *s, char *n);
@@ -4675,8 +4667,8 @@ initialize_acl(void)
 	{
 		/*
 		 * In normal mode, set a callback on any syscache invalidation of rows
-		 * of pg_auth_members (for each AUTHMEM search in this file) or
-		 * pg_authid (for has_rolinherit())
+		 * of pg_auth_members (for roles_is_member_of()) or pg_authid (for
+		 * has_rolinherit())
 		 */
 		CacheRegisterSyscacheCallback(AUTHMEMROLEMEM,
 									  RoleMembershipCacheCallback,
@@ -4695,8 +4687,8 @@ static void
 RoleMembershipCacheCallback(Datum arg, int cacheid, uint32 hashvalue)
 {
 	/* Force membership caches to be recomputed on next use */
-	cached_privs_role = InvalidOid;
-	cached_member_role = InvalidOid;
+	cached_role[ROLERECURSE_PRIVS] = InvalidOid;
+	cached_role[ROLERECURSE_MEMBERS] = InvalidOid;
 }
 
 
@@ -4718,30 +4710,35 @@ has_rolinherit(Oid roleid)
 
 
 /*
- * Get a list of roles that the specified roleid has the privileges of
+ * Get a list of roles that the specified roleid is a member of
  *
- * This is defined not to recurse through roles that don't have rolinherit
- * set; for such roles, membership implies the ability to do SET ROLE, but
- * the privileges are not available until you've done so.
+ * Type ROLERECURSE_PRIVS recurses only through roles that have rolinherit
+ * set, while ROLERECURSE_MEMBERS recurses through all roles.  This sets
+ * *is_admin==true if and only if role "roleid" has an ADMIN OPTION membership
+ * in role "admin_of".
  *
  * Since indirect membership testing is relatively expensive, we cache
  * a list of memberships.  Hence, the result is only guaranteed good until
- * the next call of roles_has_privs_of()!
+ * the next call of roles_is_member_of()!
  *
  * For the benefit of select_best_grantor, the result is defined to be
  * in breadth-first order, ie, closer relationships earlier.
  */
 static List *
-roles_has_privs_of(Oid roleid)
+roles_is_member_of(Oid roleid, enum RoleRecurseType type,
+				   Oid admin_of, bool *is_admin)
 {
 	List	   *roles_list;
 	ListCell   *l;
-	List	   *new_cached_privs_roles;
+	List	   *new_cached_roles;
 	MemoryContext oldctx;
 
-	/* If cache is already valid, just return the list */
-	if (OidIsValid(cached_privs_role) && cached_privs_role == roleid)
-		return cached_privs_roles;
+	Assert(OidIsValid(admin_of) == PointerIsValid(is_admin));
+
+	/* If cache is valid and ADMIN OPTION not sought, just return the list */
+	if (cached_role[type] == roleid && !OidIsValid(admin_of) &&
+		OidIsValid(cached_role[type]))
+		return cached_roles[type];
 
 	/*
 	 * Find all the roles that roleid is a member of, including multi-level
@@ -4762,9 +4759,8 @@ roles_has_privs_of(Oid roleid)
 		CatCList   *memlist;
 		int			i;
 
-		/* Ignore non-inheriting roles */
-		if (!has_rolinherit(memberid))
-			continue;
+		if (type == ROLERECURSE_PRIVS && !has_rolinherit(memberid))
+			continue;			/* ignore non-inheriting roles */
 
 		/* Find roles that memberid is directly a member of */
 		memlist = SearchSysCacheList1(AUTHMEMMEMROLE,
@@ -4775,83 +4771,13 @@ roles_has_privs_of(Oid roleid)
 			Oid			otherid = ((Form_pg_auth_members) GETSTRUCT(tup))->roleid;
 
 			/*
-			 * Even though there shouldn't be any loops in the membership
-			 * graph, we must test for having already seen this role. It is
-			 * legal for instance to have both A->B and A->C->B.
+			 * While otherid==InvalidOid shouldn't appear in the catalog, the
+			 * OidIsValid() avoids crashing if that arises.
 			 */
-			roles_list = list_append_unique_oid(roles_list, otherid);
-		}
-		ReleaseSysCacheList(memlist);
-	}
-
-	/*
-	 * Copy the completed list into TopMemoryContext so it will persist.
-	 */
-	oldctx = MemoryContextSwitchTo(TopMemoryContext);
-	new_cached_privs_roles = list_copy(roles_list);
-	MemoryContextSwitchTo(oldctx);
-	list_free(roles_list);
-
-	/*
-	 * Now safe to assign to state variable
-	 */
-	cached_privs_role = InvalidOid; /* just paranoia */
-	list_free(cached_privs_roles);
-	cached_privs_roles = new_cached_privs_roles;
-	cached_privs_role = roleid;
-
-	/* And now we can return the answer */
-	return cached_privs_roles;
-}
-
-
-/*
- * Get a list of roles that the specified roleid is a member of
- *
- * This is defined to recurse through roles regardless of rolinherit.
- *
- * Since indirect membership testing is relatively expensive, we cache
- * a list of memberships.  Hence, the result is only guaranteed good until
- * the next call of roles_is_member_of()!
- */
-static List *
-roles_is_member_of(Oid roleid)
-{
-	List	   *roles_list;
-	ListCell   *l;
-	List	   *new_cached_membership_roles;
-	MemoryContext oldctx;
-
-	/* If cache is already valid, just return the list */
-	if (OidIsValid(cached_member_role) && cached_member_role == roleid)
-		return cached_membership_roles;
-
-	/*
-	 * Find all the roles that roleid is a member of, including multi-level
-	 * recursion.  The role itself will always be the first element of the
-	 * resulting list.
-	 *
-	 * Each element of the list is scanned to see if it adds any indirect
-	 * memberships.  We can use a single list as both the record of
-	 * already-found memberships and the agenda of roles yet to be scanned.
-	 * This is a bit tricky but works because the foreach() macro doesn't
-	 * fetch the next list element until the bottom of the loop.
-	 */
-	roles_list = list_make1_oid(roleid);
-
-	foreach(l, roles_list)
-	{
-		Oid			memberid = lfirst_oid(l);
-		CatCList   *memlist;
-		int			i;
-
-		/* Find roles that memberid is directly a member of */
-		memlist = SearchSysCacheList1(AUTHMEMMEMROLE,
-									  ObjectIdGetDatum(memberid));
-		for (i = 0; i < memlist->n_members; i++)
-		{
-			HeapTuple	tup = &memlist->members[i]->tuple;
-			Oid			otherid = ((Form_pg_auth_members) GETSTRUCT(tup))->roleid;
+			if (otherid == admin_of &&
+				((Form_pg_auth_members) GETSTRUCT(tup))->admin_option &&
+				OidIsValid(admin_of))
+				*is_admin = true;
 
 			/*
 			 * Even though there shouldn't be any loops in the membership
@@ -4867,20 +4793,20 @@ roles_is_member_of(Oid roleid)
 	 * Copy the completed list into TopMemoryContext so it will persist.
 	 */
 	oldctx = MemoryContextSwitchTo(TopMemoryContext);
-	new_cached_membership_roles = list_copy(roles_list);
+	new_cached_roles = list_copy(roles_list);
 	MemoryContextSwitchTo(oldctx);
 	list_free(roles_list);
 
 	/*
 	 * Now safe to assign to state variable
 	 */
-	cached_member_role = InvalidOid;	/* just paranoia */
-	list_free(cached_membership_roles);
-	cached_membership_roles = new_cached_membership_roles;
-	cached_member_role = roleid;
+	cached_role[type] = InvalidOid; /* just paranoia */
+	list_free(cached_roles[type]);
+	cached_roles[type] = new_cached_roles;
+	cached_role[type] = roleid;
 
 	/* And now we can return the answer */
-	return cached_membership_roles;
+	return cached_roles[type];
 }
 
 
@@ -4906,7 +4832,9 @@ has_privs_of_role(Oid member, Oid role)
 	 * Find all the roles that member has the privileges of, including
 	 * multi-level recursion, then see if target role is any one of them.
 	 */
-	return list_member_oid(roles_has_privs_of(member), role);
+	return list_member_oid(roles_is_member_of(member, ROLERECURSE_PRIVS,
+											  InvalidOid, NULL),
+						   role);
 }
 
 
@@ -4930,7 +4858,9 @@ is_member_of_role(Oid member, Oid role)
 	 * Find all the roles that member is a member of, including multi-level
 	 * recursion, then see if target role is any one of them.
 	 */
-	return list_member_oid(roles_is_member_of(member), role);
+	return list_member_oid(roles_is_member_of(member, ROLERECURSE_MEMBERS,
+											  InvalidOid, NULL),
+						   role);
 }
 
 /*
@@ -4964,7 +4894,9 @@ is_member_of_role_nosuper(Oid member, Oid role)
 	 * Find all the roles that member is a member of, including multi-level
 	 * recursion, then see if target role is any one of them.
 	 */
-	return list_member_oid(roles_is_member_of(member), role);
+	return list_member_oid(roles_is_member_of(member, ROLERECURSE_MEMBERS,
+											  InvalidOid, NULL),
+						   role);
 }
 
 
@@ -4977,8 +4909,6 @@ bool
 is_admin_of_role(Oid member, Oid role)
 {
 	bool		result = false;
-	List	   *roles_list;
-	ListCell   *l;
 
 	if (superuser_arg(member))
 		return true;
@@ -5016,44 +4946,7 @@ is_admin_of_role(Oid member, Oid role)
 		return member == GetSessionUserId() &&
 			!InLocalUserIdChange() && !InSecurityRestrictedOperation();
 
-	/*
-	 * Find all the roles that member is a member of, including multi-level
-	 * recursion.  We build a list in the same way that is_member_of_role does
-	 * to track visited and unvisited roles.
-	 */
-	roles_list = list_make1_oid(member);
-
-	foreach(l, roles_list)
-	{
-		Oid			memberid = lfirst_oid(l);
-		CatCList   *memlist;
-		int			i;
-
-		/* Find roles that memberid is directly a member of */
-		memlist = SearchSysCacheList1(AUTHMEMMEMROLE,
-									  ObjectIdGetDatum(memberid));
-		for (i = 0; i < memlist->n_members; i++)
-		{
-			HeapTuple	tup = &memlist->members[i]->tuple;
-			Oid			otherid = ((Form_pg_auth_members) GETSTRUCT(tup))->roleid;
-
-			if (otherid == role &&
-				((Form_pg_auth_members) GETSTRUCT(tup))->admin_option)
-			{
-				/* Found what we came for, so can stop searching */
-				result = true;
-				break;
-			}
-
-			roles_list = list_append_unique_oid(roles_list, otherid);
-		}
-		ReleaseSysCacheList(memlist);
-		if (result)
-			break;
-	}
-
-	list_free(roles_list);
-
+	(void) roles_is_member_of(member, ROLERECURSE_MEMBERS, role, &result);
 	return result;
 }
 
@@ -5125,10 +5018,11 @@ select_best_grantor(Oid roleId, AclMode privileges,
 	/*
 	 * Otherwise we have to do a careful search to see if roleId has the
 	 * privileges of any suitable role.  Note: we can hang onto the result of
-	 * roles_has_privs_of() throughout this loop, because aclmask_direct()
+	 * roles_is_member_of() throughout this loop, because aclmask_direct()
 	 * doesn't query any role memberships.
 	 */
-	roles_list = roles_has_privs_of(roleId);
+	roles_list = roles_is_member_of(roleId, ROLERECURSE_PRIVS,
+									InvalidOid, NULL);
 
 	/* initialize candidate result as default */
 	*grantorId = roleId;