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Commit0d2b1f3

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Invent start_proc parameters for PL/Tcl.
Define GUCs pltcl.start_proc and pltclu.start_proc. When set to anonempty value at the time a new Tcl interpreter is created, theparameterless pltcl or pltclu function named by the GUC is called toallow user-controlled initialization to occur within the interpreter.This is modeled on plv8's start_proc parameter, and also has much incommon with plperl's on_init feature. It allows users to fullyreplace the "modules" feature that was removed in commit817f2a5.Since an initializer function could subvert later Tcl code in nearlyarbitrary ways, mark both GUCs as SUSET for now. It would be niceto find a way to relax that someday; but the corresponding GUCs inplperl are also SUSET, and there's not been much complaint.Discussion:https://postgr.es/m/22067.1488046447@sss.pgh.pa.us
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‎doc/src/sgml/pltcl.sgml‎

Lines changed: 74 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -902,6 +902,80 @@ if {[catch { spi_exec $sql_command }]} {
902902
</para>
903903
</sect1>
904904

905+
<sect1 id="pltcl-config">
906+
<title>PL/Tcl Configuration</title>
907+
908+
<para>
909+
This section lists configuration parameters that
910+
affect <application>PL/Tcl</>.
911+
</para>
912+
913+
<variablelist>
914+
915+
<varlistentry id="guc-pltcl-start-proc" xreflabel="pltcl.start_proc">
916+
<term>
917+
<varname>pltcl.start_proc</varname> (<type>string</type>)
918+
<indexterm>
919+
<primary><varname>pltcl.start_proc</> configuration parameter</primary>
920+
</indexterm>
921+
</term>
922+
<listitem>
923+
<para>
924+
This parameter, if set to a nonempty string, specifies the name
925+
(possibly schema-qualified) of a parameterless PL/Tcl function that
926+
is to be executed whenever a new Tcl interpreter is created for
927+
PL/Tcl. Such a function can perform per-session initialization, such
928+
as loading additional Tcl code. A new Tcl interpreter is created
929+
when a PL/Tcl function is first executed in a database session, or
930+
when an additional interpreter has to be created because a PL/Tcl
931+
function is called by a new SQL role.
932+
</para>
933+
934+
<para>
935+
The referenced function must be written in the <literal>pltcl</>
936+
language, and must not be marked <literal>SECURITY DEFINER</>.
937+
(These restrictions ensure that it runs in the interpreter it's
938+
supposed to initialize.) The current user must have permission to
939+
call it, too.
940+
</para>
941+
942+
<para>
943+
If the function fails with an error it will abort the function call
944+
that caused the new interpreter to be created and propagate out to
945+
the calling query, causing the current transaction or subtransaction
946+
to be aborted. Any actions already done within Tcl won't be undone;
947+
however, that interpreter won't be used again. If the language is
948+
used again the initialization will be attempted again within a fresh
949+
Tcl interpreter.
950+
</para>
951+
952+
<para>
953+
Only superusers can change this setting. Although this setting
954+
can be changed within a session, such changes will not affect Tcl
955+
interpreters that have already been created.
956+
</para>
957+
</listitem>
958+
</varlistentry>
959+
960+
<varlistentry id="guc-pltclu-start-proc" xreflabel="pltclu.start_proc">
961+
<term>
962+
<varname>pltclu.start_proc</varname> (<type>string</type>)
963+
<indexterm>
964+
<primary><varname>pltclu.start_proc</> configuration parameter</primary>
965+
</indexterm>
966+
</term>
967+
<listitem>
968+
<para>
969+
This parameter is exactly like <varname>pltcl.start_proc</varname>,
970+
except that it applies to PL/TclU. The referenced function must
971+
be written in the <literal>pltclu</> language.
972+
</para>
973+
</listitem>
974+
</varlistentry>
975+
976+
</variablelist>
977+
</sect1>
978+
905979
<sect1 id="pltcl-procnames">
906980
<title>Tcl Procedure Names</title>
907981

‎src/pl/tcl/Makefile‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,7 @@ DATA = pltcl.control pltcl--1.0.sql pltcl--unpackaged--1.0.sql \
2828
pltclu.control pltclu--1.0.sql pltclu--unpackaged--1.0.sql
2929

3030
REGRESS_OPTS = --dbname=$(PL_TESTDB) --load-extension=pltcl
31-
REGRESS = pltcl_setup pltcl_queries pltcl_unicode
31+
REGRESS = pltcl_setup pltcl_queriespltcl_start_procpltcl_unicode
3232

3333
# Tcl on win32 ships with import libraries only for Microsoft Visual C++,
3434
# which are not compatible with mingw gcc. Therefore we need to build a
Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
1+
--
2+
-- Test start_proc execution
3+
--
4+
SET pltcl.start_proc = 'no_such_function';
5+
select tcl_int4add(1, 2);
6+
ERROR: function no_such_function() does not exist
7+
CONTEXT: processing pltcl.start_proc parameter
8+
select tcl_int4add(1, 2);
9+
ERROR: function no_such_function() does not exist
10+
CONTEXT: processing pltcl.start_proc parameter
11+
create function tcl_initialize() returns void as
12+
$$ elog NOTICE "in tcl_initialize" $$ language pltcl SECURITY DEFINER;
13+
SET pltcl.start_proc = 'public.tcl_initialize';
14+
select tcl_int4add(1, 2); -- fail
15+
ERROR: function "public.tcl_initialize" must not be SECURITY DEFINER
16+
CONTEXT: processing pltcl.start_proc parameter
17+
create or replace function tcl_initialize() returns void as
18+
$$ elog NOTICE "in tcl_initialize" $$ language pltcl;
19+
select tcl_int4add(1, 2);
20+
NOTICE: in tcl_initialize
21+
tcl_int4add
22+
-------------
23+
3
24+
(1 row)
25+
26+
select tcl_int4add(1, 2);
27+
tcl_int4add
28+
-------------
29+
3
30+
(1 row)
31+

‎src/pl/tcl/pltcl.c‎

Lines changed: 159 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@
1515

1616
#include"access/htup_details.h"
1717
#include"access/xact.h"
18+
#include"catalog/objectaccess.h"
1819
#include"catalog/pg_proc.h"
1920
#include"catalog/pg_type.h"
2021
#include"commands/event_trigger.h"
@@ -25,11 +26,14 @@
2526
#include"mb/pg_wchar.h"
2627
#include"miscadmin.h"
2728
#include"nodes/makefuncs.h"
29+
#include"parser/parse_func.h"
2830
#include"parser/parse_type.h"
31+
#include"pgstat.h"
2932
#include"tcop/tcopprot.h"
3033
#include"utils/builtins.h"
3134
#include"utils/lsyscache.h"
3235
#include"utils/memutils.h"
36+
#include"utils/regproc.h"
3337
#include"utils/rel.h"
3438
#include"utils/syscache.h"
3539
#include"utils/typcache.h"
@@ -226,6 +230,8 @@ typedef struct pltcl_call_state
226230
/**********************************************************************
227231
* Global data
228232
**********************************************************************/
233+
staticchar*pltcl_start_proc=NULL;
234+
staticchar*pltclu_start_proc=NULL;
229235
staticboolpltcl_pm_init_done= false;
230236
staticTcl_Interp*pltcl_hold_interp=NULL;
231237
staticHTAB*pltcl_interp_htab=NULL;
@@ -253,8 +259,11 @@ static const TclExceptionNameMap exception_name_map[] = {
253259
**********************************************************************/
254260
void_PG_init(void);
255261

256-
staticvoidpltcl_init_interp(pltcl_interp_desc*interp_desc,boolpltrusted);
257-
staticpltcl_interp_desc*pltcl_fetch_interp(boolpltrusted);
262+
staticvoidpltcl_init_interp(pltcl_interp_desc*interp_desc,
263+
Oidprolang,boolpltrusted);
264+
staticpltcl_interp_desc*pltcl_fetch_interp(Oidprolang,boolpltrusted);
265+
staticvoidcall_pltcl_start_proc(Oidprolang,boolpltrusted);
266+
staticvoidstart_proc_error_callback(void*arg);
258267

259268
staticDatumpltcl_handler(PG_FUNCTION_ARGS,boolpltrusted);
260269

@@ -441,14 +450,32 @@ _PG_init(void)
441450
&hash_ctl,
442451
HASH_ELEM |HASH_BLOBS);
443452

453+
/************************************************************
454+
* Define PL/Tcl's custom GUCs
455+
************************************************************/
456+
DefineCustomStringVariable("pltcl.start_proc",
457+
gettext_noop("PL/Tcl function to call once when pltcl is first used."),
458+
NULL,
459+
&pltcl_start_proc,
460+
NULL,
461+
PGC_SUSET,0,
462+
NULL,NULL,NULL);
463+
DefineCustomStringVariable("pltclu.start_proc",
464+
gettext_noop("PL/TclU function to call once when pltclu is first used."),
465+
NULL,
466+
&pltclu_start_proc,
467+
NULL,
468+
PGC_SUSET,0,
469+
NULL,NULL,NULL);
470+
444471
pltcl_pm_init_done= true;
445472
}
446473

447474
/**********************************************************************
448475
* pltcl_init_interp() - initialize a new Tcl interpreter
449476
**********************************************************************/
450477
staticvoid
451-
pltcl_init_interp(pltcl_interp_desc*interp_desc,boolpltrusted)
478+
pltcl_init_interp(pltcl_interp_desc*interp_desc,Oidprolang,boolpltrusted)
452479
{
453480
Tcl_Interp*interp;
454481
charinterpname[32];
@@ -462,7 +489,6 @@ pltcl_init_interp(pltcl_interp_desc *interp_desc, bool pltrusted)
462489
if ((interp=Tcl_CreateSlave(pltcl_hold_interp,interpname,
463490
pltrusted ?1 :0))==NULL)
464491
elog(ERROR,"could not create slave Tcl interpreter");
465-
interp_desc->interp=interp;
466492

467493
/************************************************************
468494
* Initialize the query hash table associated with interpreter
@@ -490,16 +516,35 @@ pltcl_init_interp(pltcl_interp_desc *interp_desc, bool pltrusted)
490516
pltcl_SPI_execute_plan,NULL,NULL);
491517
Tcl_CreateObjCommand(interp,"spi_lastoid",
492518
pltcl_SPI_lastoid,NULL,NULL);
519+
520+
/************************************************************
521+
* Call the appropriate start_proc, if there is one.
522+
*
523+
* We must set interp_desc->interp before the call, else the start_proc
524+
* won't find the interpreter it's supposed to use. But, if the
525+
* start_proc fails, we want to abandon use of the interpreter.
526+
************************************************************/
527+
PG_TRY();
528+
{
529+
interp_desc->interp=interp;
530+
call_pltcl_start_proc(prolang,pltrusted);
531+
}
532+
PG_CATCH();
533+
{
534+
interp_desc->interp=NULL;
535+
Tcl_DeleteInterp(interp);
536+
PG_RE_THROW();
537+
}
538+
PG_END_TRY();
493539
}
494540

495541
/**********************************************************************
496542
* pltcl_fetch_interp() - fetch the Tcl interpreter to use for a function
497543
*
498544
* This also takes care of any on-first-use initialization required.
499-
* Note: we assume caller has already connected to SPI.
500545
**********************************************************************/
501546
staticpltcl_interp_desc*
502-
pltcl_fetch_interp(boolpltrusted)
547+
pltcl_fetch_interp(Oidprolang,boolpltrusted)
503548
{
504549
Oiduser_id;
505550
pltcl_interp_desc*interp_desc;
@@ -515,12 +560,117 @@ pltcl_fetch_interp(bool pltrusted)
515560
HASH_ENTER,
516561
&found);
517562
if (!found)
518-
pltcl_init_interp(interp_desc,pltrusted);
563+
interp_desc->interp=NULL;
564+
565+
/* If we haven't yet successfully made an interpreter, try to do that */
566+
if (!interp_desc->interp)
567+
pltcl_init_interp(interp_desc,prolang,pltrusted);
519568

520569
returninterp_desc;
521570
}
522571

523572

573+
/**********************************************************************
574+
* call_pltcl_start_proc() - Call user-defined initialization proc, if any
575+
**********************************************************************/
576+
staticvoid
577+
call_pltcl_start_proc(Oidprolang,boolpltrusted)
578+
{
579+
char*start_proc;
580+
constchar*gucname;
581+
ErrorContextCallbackerrcallback;
582+
List*namelist;
583+
Oidfargtypes[1];/* dummy */
584+
OidprocOid;
585+
HeapTupleprocTup;
586+
Form_pg_procprocStruct;
587+
AclResultaclresult;
588+
FmgrInfofinfo;
589+
FunctionCallInfoDatafcinfo;
590+
PgStat_FunctionCallUsagefcusage;
591+
592+
/* select appropriate GUC */
593+
start_proc=pltrusted ?pltcl_start_proc :pltclu_start_proc;
594+
gucname=pltrusted ?"pltcl.start_proc" :"pltclu.start_proc";
595+
596+
/* Nothing to do if it's empty or unset */
597+
if (start_proc==NULL||start_proc[0]=='\0')
598+
return;
599+
600+
/* Set up errcontext callback to make errors more helpful */
601+
errcallback.callback=start_proc_error_callback;
602+
errcallback.arg= (void*)gucname;
603+
errcallback.previous=error_context_stack;
604+
error_context_stack=&errcallback;
605+
606+
/* Parse possibly-qualified identifier and look up the function */
607+
namelist=stringToQualifiedNameList(start_proc);
608+
procOid=LookupFuncName(namelist,0,fargtypes, false);
609+
610+
/* Current user must have permission to call function */
611+
aclresult=pg_proc_aclcheck(procOid,GetUserId(),ACL_EXECUTE);
612+
if (aclresult!=ACLCHECK_OK)
613+
aclcheck_error(aclresult,ACL_KIND_PROC,start_proc);
614+
615+
/* Get the function's pg_proc entry */
616+
procTup=SearchSysCache1(PROCOID,ObjectIdGetDatum(procOid));
617+
if (!HeapTupleIsValid(procTup))
618+
elog(ERROR,"cache lookup failed for function %u",procOid);
619+
procStruct= (Form_pg_proc)GETSTRUCT(procTup);
620+
621+
/* It must be same language as the function we're currently calling */
622+
if (procStruct->prolang!=prolang)
623+
ereport(ERROR,
624+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
625+
errmsg("function \"%s\" is in the wrong language",
626+
start_proc)));
627+
628+
/*
629+
* It must not be SECURITY DEFINER, either. This together with the
630+
* language match check ensures that the function will execute in the same
631+
* Tcl interpreter we just finished initializing.
632+
*/
633+
if (procStruct->prosecdef)
634+
ereport(ERROR,
635+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
636+
errmsg("function \"%s\" must not be SECURITY DEFINER",
637+
start_proc)));
638+
639+
/* A-OK */
640+
ReleaseSysCache(procTup);
641+
642+
/*
643+
* Call the function using the normal SQL function call mechanism. We
644+
* could perhaps cheat and jump directly to pltcl_handler(), but it seems
645+
* better to do it this way so that the call is exposed to, eg, call
646+
* statistics collection.
647+
*/
648+
InvokeFunctionExecuteHook(procOid);
649+
fmgr_info(procOid,&finfo);
650+
InitFunctionCallInfoData(fcinfo,&finfo,
651+
0,
652+
InvalidOid,NULL,NULL);
653+
pgstat_init_function_usage(&fcinfo,&fcusage);
654+
(void)FunctionCallInvoke(&fcinfo);
655+
pgstat_end_function_usage(&fcusage, true);
656+
657+
/* Pop the error context stack */
658+
error_context_stack=errcallback.previous;
659+
}
660+
661+
/*
662+
* Error context callback for errors occurring during start_proc processing.
663+
*/
664+
staticvoid
665+
start_proc_error_callback(void*arg)
666+
{
667+
constchar*gucname= (constchar*)arg;
668+
669+
/* translator: %s is "pltcl.start_proc" or "pltclu.start_proc" */
670+
errcontext("processing %s parameter",gucname);
671+
}
672+
673+
524674
/**********************************************************************
525675
* pltcl_call_handler- This is the only visible function
526676
* of the PL interpreter. The PostgreSQL
@@ -1319,7 +1469,8 @@ compile_pltcl_function(Oid fn_oid, Oid tgreloid,
13191469
/************************************************************
13201470
* Identify the interpreter to use for the function
13211471
************************************************************/
1322-
prodesc->interp_desc=pltcl_fetch_interp(prodesc->lanpltrusted);
1472+
prodesc->interp_desc=pltcl_fetch_interp(procStruct->prolang,
1473+
prodesc->lanpltrusted);
13231474
interp=prodesc->interp_desc->interp;
13241475

13251476
/************************************************************
Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,21 @@
1+
--
2+
-- Test start_proc execution
3+
--
4+
5+
SETpltcl.start_proc='no_such_function';
6+
7+
select tcl_int4add(1,2);
8+
select tcl_int4add(1,2);
9+
10+
createfunctiontcl_initialize() returns voidas
11+
$$ elog NOTICE"in tcl_initialize" $$ language pltcl SECURITY DEFINER;
12+
13+
SETpltcl.start_proc='public.tcl_initialize';
14+
15+
select tcl_int4add(1,2);-- fail
16+
17+
create or replacefunctiontcl_initialize() returns voidas
18+
$$ elog NOTICE"in tcl_initialize" $$ language pltcl;
19+
20+
select tcl_int4add(1,2);
21+
select tcl_int4add(1,2);

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