hooks.c
/* -------------------------------------------------------------------------
*
* contrib/sepgsql/hooks.c
*
* Entrypoints of the hooks in PostgreSQL, and dispatches the callbacks.
*
* Copyright (c) 2010-2019, PostgreSQL Global Development Group
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/dependency.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_class.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_proc.h"
#include "commands/seclabel.h"
#include "executor/executor.h"
#include "fmgr.h"
#include "miscadmin.h"
#include "tcop/utility.h"
#include "utils/guc.h"
#include "utils/queryenvironment.h"
#include "sepgsql.h"
PG_MODULE_MAGIC;
/*
* Declarations
*/
void _PG_init(void);
/*
* Saved hook entries (if stacked)
*/
static object_access_hook_type next_object_access_hook = NULL;
static ExecutorCheckPerms_hook_type next_exec_check_perms_hook = NULL;
static ProcessUtility_hook_type next_ProcessUtility_hook = NULL;
/*
* Contextual information on DDL commands
*/
typedef struct
{
NodeTag cmdtype;
/*
* Name of the template database given by users on CREATE DATABASE
* command. Elsewhere (including the case of default) NULL.
*/
const char *createdb_dtemplate;
} sepgsql_context_info_t;
static sepgsql_context_info_t sepgsql_context_info;
/*
* GUC: sepgsql.permissive = (on|off)
*/
static bool sepgsql_permissive;
bool
sepgsql_get_permissive(void)
{
return sepgsql_permissive;
}
/*
* GUC: sepgsql.debug_audit = (on|off)
*/
static bool sepgsql_debug_audit;
bool
sepgsql_get_debug_audit(void)
{
return sepgsql_debug_audit;
}
/*
* sepgsql_object_access
*
* Entrypoint of the object_access_hook. This routine performs as
* a dispatcher of invocation based on access type and object classes.
*/
static void
sepgsql_object_access(ObjectAccessType access,
Oid classId,
Oid objectId,
int subId,
void *arg)
{
if (next_object_access_hook)
(*next_object_access_hook) (access, classId, objectId, subId, arg);
switch (access)
{
case OAT_POST_CREATE:
{
ObjectAccessPostCreate *pc_arg = arg;
bool is_internal;
is_internal = pc_arg ? pc_arg->is_internal : false;
switch (classId)
{
case DatabaseRelationId:
Assert(!is_internal);
sepgsql_database_post_create(objectId,
sepgsql_context_info.createdb_dtemplate);
break;
case NamespaceRelationId:
Assert(!is_internal);
sepgsql_schema_post_create(objectId);
break;
case RelationRelationId:
if (subId == 0)
{
/*
* The cases in which we want to apply permission
* checks on creation of a new relation correspond
* to direct user invocation. For internal uses,
* that is creation of toast tables, index rebuild
* or ALTER TABLE commands, we need neither
* assignment of security labels nor permission
* checks.
*/
if (is_internal)
break;
sepgsql_relation_post_create(objectId);
}
else
sepgsql_attribute_post_create(objectId, subId);
break;
case ProcedureRelationId:
Assert(!is_internal);
sepgsql_proc_post_create(objectId);
break;
default:
/* Ignore unsupported object classes */
break;
}
}
break;
case OAT_DROP:
{
ObjectAccessDrop *drop_arg = (ObjectAccessDrop *) arg;
/*
* No need to apply permission checks on object deletion due
* to internal cleanups; such as removal of temporary database
* object on session closed.
*/
if ((drop_arg->dropflags & PERFORM_DELETION_INTERNAL) != 0)
break;
switch (classId)
{
case DatabaseRelationId:
sepgsql_database_drop(objectId);
break;
case NamespaceRelationId:
sepgsql_schema_drop(objectId);
break;
case RelationRelationId:
if (subId == 0)
sepgsql_relation_drop(objectId);
else
sepgsql_attribute_drop(objectId, subId);
break;
case ProcedureRelationId:
sepgsql_proc_drop(objectId);
break;
default:
/* Ignore unsupported object classes */
break;
}
}
break;
case OAT_POST_ALTER:
{
ObjectAccessPostAlter *pa_arg = arg;
bool is_internal = pa_arg->is_internal;
switch (classId)
{
case DatabaseRelationId:
Assert(!is_internal);
sepgsql_database_setattr(objectId);
break;
case NamespaceRelationId:
Assert(!is_internal);
sepgsql_schema_setattr(objectId);
break;
case RelationRelationId:
if (subId == 0)
{
/*
* A case when we don't want to apply permission
* check is that relation is internally altered
* without user's intention. E.g, no need to check
* on toast table/index to be renamed at end of
* the table rewrites.
*/
if (is_internal)
break;
sepgsql_relation_setattr(objectId);
}
else
sepgsql_attribute_setattr(objectId, subId);
break;
case ProcedureRelationId:
Assert(!is_internal);
sepgsql_proc_setattr(objectId);
break;
default:
/* Ignore unsupported object classes */
break;
}
}
break;
case OAT_NAMESPACE_SEARCH:
{
ObjectAccessNamespaceSearch *ns_arg = arg;
/*
* If stacked extension already decided not to allow users to
* search this schema, we just stick with that decision.
*/
if (!ns_arg->result)
break;
Assert(classId == NamespaceRelationId);
Assert(ns_arg->result);
ns_arg->result
= sepgsql_schema_search(objectId,
ns_arg->ereport_on_violation);
}
break;
case OAT_FUNCTION_EXECUTE:
{
Assert(classId == ProcedureRelationId);
sepgsql_proc_execute(objectId);
}
break;
default:
elog(ERROR, "unexpected object access type: %d", (int) access);
break;
}
}
/*
* sepgsql_exec_check_perms
*
* Entrypoint of DML permissions
*/
static bool
sepgsql_exec_check_perms(List *rangeTabls, bool abort)
{
/*
* If security provider is stacking and one of them replied 'false' at
* least, we don't need to check any more.
*/
if (next_exec_check_perms_hook &&
!(*next_exec_check_perms_hook) (rangeTabls, abort))
return false;
if (!sepgsql_dml_privileges(rangeTabls, abort))
return false;
return true;
}
/*
* sepgsql_utility_command
*
* It tries to rough-grained control on utility commands; some of them can
* break whole of the things if nefarious user would use.
*/
static void
sepgsql_utility_command(PlannedStmt *pstmt,
const char *queryString,
ProcessUtilityContext context,
ParamListInfo params,
QueryEnvironment *queryEnv,
DestReceiver *dest,
char *completionTag)
{
Node *parsetree = pstmt->utilityStmt;
sepgsql_context_info_t saved_context_info = sepgsql_context_info;
ListCell *cell;
PG_TRY();
{
/*
* Check command tag to avoid nefarious operations, and save the
* current contextual information to determine whether we should apply
* permission checks here, or not.
*/
sepgsql_context_info.cmdtype = nodeTag(parsetree);
switch (nodeTag(parsetree))
{
case T_CreatedbStmt:
/*
* We hope to reference name of the source database, but it
* does not appear in system catalog. So, we save it here.
*/
foreach(cell, ((CreatedbStmt *) parsetree)->options)
{
DefElem *defel = (DefElem *) lfirst(cell);
if (strcmp(defel->defname, "template") == 0)
{
sepgsql_context_info.createdb_dtemplate
= strVal(defel->arg);
break;
}
}
break;
case T_LoadStmt:
/*
* We reject LOAD command across the board on enforcing mode,
* because a binary module can arbitrarily override hooks.
*/
if (sepgsql_getenforce())
{
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("SELinux: LOAD is not permitted")));
}
break;
default:
/*
* Right now we don't check any other utility commands,
* because it needs more detailed information to make access
* control decision here, but we don't want to have two parse
* and analyze routines individually.
*/
break;
}
if (next_ProcessUtility_hook)
(*next_ProcessUtility_hook) (pstmt, queryString,
context, params, queryEnv,
dest, completionTag);
else
standard_ProcessUtility(pstmt, queryString,
context, params, queryEnv,
dest, completionTag);
}
PG_CATCH();
{
sepgsql_context_info = saved_context_info;
PG_RE_THROW();
}
PG_END_TRY();
sepgsql_context_info = saved_context_info;
}
/*
* Module load/unload callback
*/
void
_PG_init(void)
{
/*
* We allow to load the SE-PostgreSQL module on single-user-mode or
* shared_preload_libraries settings only.
*/
if (IsUnderPostmaster)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("sepgsql must be loaded via shared_preload_libraries")));
/*
* Check availability of SELinux on the platform. If disabled, we cannot
* activate any SE-PostgreSQL features, and we have to skip rest of
* initialization.
*/
if (is_selinux_enabled() < 1)
{
sepgsql_set_mode(SEPGSQL_MODE_DISABLED);
return;
}
/*
* sepgsql.permissive = (on|off)
*
* This variable controls performing mode of SE-PostgreSQL on user's
* session.
*/
DefineCustomBoolVariable("sepgsql.permissive",
"Turn on/off permissive mode in SE-PostgreSQL",
NULL,
&sepgsql_permissive,
false,
PGC_SIGHUP,
GUC_NOT_IN_SAMPLE,
NULL,
NULL,
NULL);
/*
* sepgsql.debug_audit = (on|off)
*
* This variable allows users to turn on/off audit logs on access control
* decisions, independent from auditallow/auditdeny setting in the
* security policy. We intend to use this option for debugging purpose.
*/
DefineCustomBoolVariable("sepgsql.debug_audit",
"Turn on/off debug audit messages",
NULL,
&sepgsql_debug_audit,
false,
PGC_USERSET,
GUC_NOT_IN_SAMPLE,
NULL,
NULL,
NULL);
/* Initialize userspace access vector cache */
sepgsql_avc_init();
/* Initialize security label of the client and related stuff */
sepgsql_init_client_label();
/* Security label provider hook */
register_label_provider(SEPGSQL_LABEL_TAG,
sepgsql_object_relabel);
/* Object access hook */
next_object_access_hook = object_access_hook;
object_access_hook = sepgsql_object_access;
/* DML permission check */
next_exec_check_perms_hook = ExecutorCheckPerms_hook;
ExecutorCheckPerms_hook = sepgsql_exec_check_perms;
/* ProcessUtility hook */
next_ProcessUtility_hook = ProcessUtility_hook;
ProcessUtility_hook = sepgsql_utility_command;
/* init contextual info */
memset(&sepgsql_context_info, 0, sizeof(sepgsql_context_info));
}
