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In the "simple Query" code path, it's fine for parse analysis or execution of a utility statement to scribble on the statement's node tree, since that'll just be thrown away afterwards. However it's not fine if the node tree is in the plan cache, as then it'd be corrupted for subsequent executions. Up to now we've dealt with that by having individual utility-statement functions apply copyObject() if they were going to modify the tree. But that's prone to errors of omission. Bug #17053 from Charles Samborski shows that CREATE/ALTER DOMAIN didn't get this memo, and can crash if executed repeatedly from plan cache. In the back branches, we'll just apply a narrow band-aid for that, but in HEAD it seems prudent to have a more principled fix that will close off the possibility of other similar bugs in future. Hence, let's hoist the responsibility for doing copyObject up into ProcessUtility from its children, thus ensuring that it happens for all utility statement types. Also, modify ProcessUtility's API so that its callers can tell it whether a copy step is necessary. It turns out that in all cases, the immediate caller knows whether the node tree is transient, so this doesn't involve a huge amount of code thrashing. In this way, while we lose a little bit in the execute-from-cache code path due to sometimes copying node trees that wouldn't be mutated anyway, we gain something in the simple-Query code path by not copying throwaway node trees. Statements that are complex enough to be expensive to copy are almost certainly ones that would have to be copied anyway, so the loss in the cache code path shouldn't be much. (Note that this whole problem applies only to utility statements. Optimizable statements don't have the issue because we long ago made the executor treat Plan trees as read-only. Perhaps someday we will make utility statement execution act likewise, but I'm not holding my breath.) Discussion: https://postgr.es/m/931771.1623893989@sss.pgh.pa.us Discussion: https://postgr.es/m/17053-3ca3f501bbc212b4@postgresql.org
483 lines
11 KiB
C
483 lines
11 KiB
C
/* -------------------------------------------------------------------------
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*
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* contrib/sepgsql/hooks.c
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*
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* Entrypoints of the hooks in PostgreSQL, and dispatches the callbacks.
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*
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* Copyright (c) 2010-2021, PostgreSQL Global Development Group
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*
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* -------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "catalog/dependency.h"
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#include "catalog/objectaccess.h"
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#include "catalog/pg_class.h"
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#include "catalog/pg_database.h"
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#include "catalog/pg_namespace.h"
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#include "catalog/pg_proc.h"
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#include "commands/seclabel.h"
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#include "executor/executor.h"
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#include "fmgr.h"
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#include "miscadmin.h"
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#include "sepgsql.h"
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#include "tcop/utility.h"
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#include "utils/guc.h"
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#include "utils/queryenvironment.h"
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PG_MODULE_MAGIC;
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/*
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* Declarations
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*/
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void _PG_init(void);
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/*
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* Saved hook entries (if stacked)
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*/
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static object_access_hook_type next_object_access_hook = NULL;
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static ExecutorCheckPerms_hook_type next_exec_check_perms_hook = NULL;
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static ProcessUtility_hook_type next_ProcessUtility_hook = NULL;
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/*
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* Contextual information on DDL commands
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*/
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typedef struct
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{
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NodeTag cmdtype;
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/*
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* Name of the template database given by users on CREATE DATABASE
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* command. Elsewhere (including the case of default) NULL.
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*/
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const char *createdb_dtemplate;
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} sepgsql_context_info_t;
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static sepgsql_context_info_t sepgsql_context_info;
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/*
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* GUC: sepgsql.permissive = (on|off)
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*/
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static bool sepgsql_permissive;
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bool
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sepgsql_get_permissive(void)
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{
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return sepgsql_permissive;
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}
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/*
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* GUC: sepgsql.debug_audit = (on|off)
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*/
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static bool sepgsql_debug_audit;
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bool
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sepgsql_get_debug_audit(void)
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{
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return sepgsql_debug_audit;
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}
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/*
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* sepgsql_object_access
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*
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* Entrypoint of the object_access_hook. This routine performs as
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* a dispatcher of invocation based on access type and object classes.
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*/
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static void
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sepgsql_object_access(ObjectAccessType access,
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Oid classId,
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Oid objectId,
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int subId,
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void *arg)
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{
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if (next_object_access_hook)
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(*next_object_access_hook) (access, classId, objectId, subId, arg);
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switch (access)
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{
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case OAT_POST_CREATE:
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{
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ObjectAccessPostCreate *pc_arg = arg;
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bool is_internal;
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is_internal = pc_arg ? pc_arg->is_internal : false;
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switch (classId)
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{
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case DatabaseRelationId:
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Assert(!is_internal);
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sepgsql_database_post_create(objectId,
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sepgsql_context_info.createdb_dtemplate);
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break;
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case NamespaceRelationId:
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Assert(!is_internal);
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sepgsql_schema_post_create(objectId);
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break;
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case RelationRelationId:
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if (subId == 0)
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{
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/*
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* The cases in which we want to apply permission
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* checks on creation of a new relation correspond
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* to direct user invocation. For internal uses,
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* that is creation of toast tables, index rebuild
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* or ALTER TABLE commands, we need neither
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* assignment of security labels nor permission
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* checks.
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*/
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if (is_internal)
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break;
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sepgsql_relation_post_create(objectId);
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}
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else
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sepgsql_attribute_post_create(objectId, subId);
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break;
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case ProcedureRelationId:
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Assert(!is_internal);
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sepgsql_proc_post_create(objectId);
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break;
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default:
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/* Ignore unsupported object classes */
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break;
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}
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}
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break;
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case OAT_DROP:
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{
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ObjectAccessDrop *drop_arg = (ObjectAccessDrop *) arg;
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/*
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* No need to apply permission checks on object deletion due
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* to internal cleanups; such as removal of temporary database
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* object on session closed.
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*/
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if ((drop_arg->dropflags & PERFORM_DELETION_INTERNAL) != 0)
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break;
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switch (classId)
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{
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case DatabaseRelationId:
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sepgsql_database_drop(objectId);
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break;
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case NamespaceRelationId:
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sepgsql_schema_drop(objectId);
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break;
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case RelationRelationId:
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if (subId == 0)
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sepgsql_relation_drop(objectId);
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else
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sepgsql_attribute_drop(objectId, subId);
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break;
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case ProcedureRelationId:
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sepgsql_proc_drop(objectId);
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break;
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default:
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/* Ignore unsupported object classes */
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break;
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}
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}
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break;
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case OAT_TRUNCATE:
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{
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switch (classId)
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{
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case RelationRelationId:
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sepgsql_relation_truncate(objectId);
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break;
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default:
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/* Ignore unsupported object classes */
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break;
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}
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}
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break;
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case OAT_POST_ALTER:
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{
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ObjectAccessPostAlter *pa_arg = arg;
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bool is_internal = pa_arg->is_internal;
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switch (classId)
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{
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case DatabaseRelationId:
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Assert(!is_internal);
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sepgsql_database_setattr(objectId);
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break;
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case NamespaceRelationId:
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Assert(!is_internal);
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sepgsql_schema_setattr(objectId);
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break;
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case RelationRelationId:
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if (subId == 0)
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{
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/*
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* A case when we don't want to apply permission
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* check is that relation is internally altered
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* without user's intention. E.g, no need to check
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* on toast table/index to be renamed at end of
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* the table rewrites.
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*/
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if (is_internal)
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break;
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sepgsql_relation_setattr(objectId);
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}
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else
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sepgsql_attribute_setattr(objectId, subId);
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break;
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case ProcedureRelationId:
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Assert(!is_internal);
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sepgsql_proc_setattr(objectId);
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break;
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default:
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/* Ignore unsupported object classes */
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break;
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}
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}
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break;
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case OAT_NAMESPACE_SEARCH:
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{
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ObjectAccessNamespaceSearch *ns_arg = arg;
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/*
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* If stacked extension already decided not to allow users to
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* search this schema, we just stick with that decision.
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*/
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if (!ns_arg->result)
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break;
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Assert(classId == NamespaceRelationId);
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Assert(ns_arg->result);
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ns_arg->result
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= sepgsql_schema_search(objectId,
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ns_arg->ereport_on_violation);
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}
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break;
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case OAT_FUNCTION_EXECUTE:
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{
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Assert(classId == ProcedureRelationId);
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sepgsql_proc_execute(objectId);
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}
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break;
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default:
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elog(ERROR, "unexpected object access type: %d", (int) access);
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break;
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}
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}
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/*
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* sepgsql_exec_check_perms
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*
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* Entrypoint of DML permissions
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*/
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static bool
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sepgsql_exec_check_perms(List *rangeTabls, bool abort)
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{
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/*
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* If security provider is stacking and one of them replied 'false' at
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* least, we don't need to check any more.
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*/
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if (next_exec_check_perms_hook &&
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!(*next_exec_check_perms_hook) (rangeTabls, abort))
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return false;
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if (!sepgsql_dml_privileges(rangeTabls, abort))
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return false;
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return true;
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}
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/*
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* sepgsql_utility_command
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*
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* It tries to rough-grained control on utility commands; some of them can
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* break whole of the things if nefarious user would use.
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*/
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static void
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sepgsql_utility_command(PlannedStmt *pstmt,
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const char *queryString,
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bool readOnlyTree,
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ProcessUtilityContext context,
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ParamListInfo params,
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QueryEnvironment *queryEnv,
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DestReceiver *dest,
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QueryCompletion *qc)
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{
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Node *parsetree = pstmt->utilityStmt;
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sepgsql_context_info_t saved_context_info = sepgsql_context_info;
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ListCell *cell;
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PG_TRY();
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{
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/*
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* Check command tag to avoid nefarious operations, and save the
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* current contextual information to determine whether we should apply
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* permission checks here, or not.
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*/
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sepgsql_context_info.cmdtype = nodeTag(parsetree);
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switch (nodeTag(parsetree))
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{
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case T_CreatedbStmt:
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/*
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* We hope to reference name of the source database, but it
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* does not appear in system catalog. So, we save it here.
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*/
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foreach(cell, ((CreatedbStmt *) parsetree)->options)
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{
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DefElem *defel = (DefElem *) lfirst(cell);
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if (strcmp(defel->defname, "template") == 0)
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{
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sepgsql_context_info.createdb_dtemplate
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= strVal(defel->arg);
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break;
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}
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}
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break;
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case T_LoadStmt:
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/*
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* We reject LOAD command across the board on enforcing mode,
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* because a binary module can arbitrarily override hooks.
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*/
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if (sepgsql_getenforce())
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{
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("SELinux: LOAD is not permitted")));
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}
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break;
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default:
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/*
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* Right now we don't check any other utility commands,
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* because it needs more detailed information to make access
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* control decision here, but we don't want to have two parse
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* and analyze routines individually.
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*/
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break;
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}
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if (next_ProcessUtility_hook)
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(*next_ProcessUtility_hook) (pstmt, queryString, readOnlyTree,
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context, params, queryEnv,
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dest, qc);
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else
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standard_ProcessUtility(pstmt, queryString, readOnlyTree,
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context, params, queryEnv,
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dest, qc);
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}
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PG_FINALLY();
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{
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sepgsql_context_info = saved_context_info;
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}
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PG_END_TRY();
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}
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/*
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* Module load/unload callback
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*/
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void
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_PG_init(void)
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{
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/*
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* We allow to load the SE-PostgreSQL module on single-user-mode or
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* shared_preload_libraries settings only.
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*/
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if (IsUnderPostmaster)
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("sepgsql must be loaded via shared_preload_libraries")));
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/*
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* Check availability of SELinux on the platform. If disabled, we cannot
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* activate any SE-PostgreSQL features, and we have to skip rest of
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* initialization.
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*/
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if (is_selinux_enabled() < 1)
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{
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sepgsql_set_mode(SEPGSQL_MODE_DISABLED);
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return;
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}
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/*
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* sepgsql.permissive = (on|off)
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*
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* This variable controls performing mode of SE-PostgreSQL on user's
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* session.
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*/
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DefineCustomBoolVariable("sepgsql.permissive",
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"Turn on/off permissive mode in SE-PostgreSQL",
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NULL,
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&sepgsql_permissive,
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false,
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PGC_SIGHUP,
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GUC_NOT_IN_SAMPLE,
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NULL,
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NULL,
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NULL);
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/*
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* sepgsql.debug_audit = (on|off)
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*
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* This variable allows users to turn on/off audit logs on access control
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* decisions, independent from auditallow/auditdeny setting in the
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* security policy. We intend to use this option for debugging purpose.
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*/
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DefineCustomBoolVariable("sepgsql.debug_audit",
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"Turn on/off debug audit messages",
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NULL,
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&sepgsql_debug_audit,
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false,
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PGC_USERSET,
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GUC_NOT_IN_SAMPLE,
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NULL,
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NULL,
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NULL);
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/* Initialize userspace access vector cache */
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sepgsql_avc_init();
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/* Initialize security label of the client and related stuff */
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sepgsql_init_client_label();
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/* Security label provider hook */
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register_label_provider(SEPGSQL_LABEL_TAG,
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sepgsql_object_relabel);
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/* Object access hook */
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next_object_access_hook = object_access_hook;
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object_access_hook = sepgsql_object_access;
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/* DML permission check */
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next_exec_check_perms_hook = ExecutorCheckPerms_hook;
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ExecutorCheckPerms_hook = sepgsql_exec_check_perms;
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/* ProcessUtility hook */
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next_ProcessUtility_hook = ProcessUtility_hook;
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ProcessUtility_hook = sepgsql_utility_command;
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/* init contextual info */
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memset(&sepgsql_context_info, 0, sizeof(sepgsql_context_info));
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}
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