Custom scripts - Increasing limit beyond 255 chars?

[tiarnaigh]

Hi guys.
Custom scripts are something I use a lot in Zabbix UI (i.e. Administration/Scripts) to running remote command etc. on various servers. Currently, there appears to be a hard set limit of 255 characters per script/command, and I was hoping someone could advise on how I can increase this?

I have tried modifying the Zabbix database, "scripts" table as per below and changing the default "command" column from a "character varying(255)" type to say a "character varying(500)" type, but this doesn't seem to have made any difference.

Is there an easy way to do this?

Thanks in advance,
M

zabbix=# \d scripts;
Table "public.scripts"
Column | Type | Modifiers
--------------+------------------------+----------------------------------------
scriptid | bigint | not null
name | character varying(255) | not null default ''::character varying
command | character varying(255) | not null default ''::character varying
host_access | integer | not null default 2
usrgrpid | bigint |
groupid | bigint |
description | text | not null default ''::text
confirmation | character varying(255) | not null default ''::character varying
type | integer | not null default 0
execute_on | integer | not null default 1
Indexes:
"scripts_pkey" PRIMARY KEY, btree (scriptid)
"scripts_3" UNIQUE, btree (name)
"scripts_1" btree (usrgrpid)
"scripts_2" btree (groupid)
Foreign-key constraints:
"c_scripts_1" FOREIGN KEY (usrgrpid) REFERENCES usrgrp(usrgrpid)
"c_scripts_2" FOREIGN KEY (groupid) REFERENCES groups(groupid)
Referenced by:
TABLE "opcommand" CONSTRAINT "c_opcommand_2" FOREIGN KEY (scriptid) REFERENCES scripts(scriptid)

zabbix=# ALTER TABLE scripts ALTER COLUMN command TYPE character varying(500);
ALTER TABLE


zabbix=# \d scripts;
Table "public.scripts"
Column | Type | Modifiers
--------------+------------------------+----------------------------------------
scriptid | bigint | not null
name | character varying(255) | not null default ''::character varying
command | character varying(500) | not null default ''::character varying
host_access | integer | not null default 2
usrgrpid | bigint |
groupid | bigint |
description | text | not null default ''::text
confirmation | character varying(255) | not null default ''::character varying
type | integer | not null default 0
execute_on | integer | not null default 1
Indexes:
"scripts_pkey" PRIMARY KEY, btree (scriptid)
"scripts_3" UNIQUE, btree (name)
"scripts_1" btree (usrgrpid)
"scripts_2" btree (groupid)
Foreign-key constraints:
"c_scripts_1" FOREIGN KEY (usrgrpid) REFERENCES usrgrp(usrgrpid)
"c_scripts_2" FOREIGN KEY (groupid) REFERENCES groups(groupid)
Referenced by:
TABLE "opcommand" CONSTRAINT "c_opcommand_2" FOREIGN KEY (scriptid) REFERENCES scripts(scriptid)

[tiarnaigh]

I actually found this since, thanks to a related old post to do with triggers & upper limits (https://support.zabbix.com/browse/ZBX-4302). Solution was pretty simple in the end:

Updated DB as follows to increase the "command" column from 255 to 1024 (Can be increased to more I guess) as follows:

zabbix=# ALTER TABLE scripts ALTER COLUMN command TYPE character varying(1024);
ALTER TABLE

Once I did this, I then updated /var/www/html/zabbix/include/schema.inc.php for this specific field to correspond to new value as per below:

   1578         'scripts' => array(
   1579                 'key' => 'scriptid',
   1580                 'fields' => array(
   1581                         'scriptid' => array(
   1582                                 'null' => false,
   1583                                 'type' => DB::FIELD_TYPE_ID,
   1584                                 'length' => 20,
   1585                         ),
   1586                         'name' => array(
   1587                                 'null' => false,
   1588                                 'type' => DB::FIELD_TYPE_CHAR,
   1589                                 'length' => 255,
   1590                                 'default' => '',
   1591                         ),
   1592                         'command' => array(
   1593                                 'null' => false,
   1594                                 'type' => DB::FIELD_TYPE_CHAR,
   [B]1595                                 'length' => 1024,[/B]
   1596                                 'default' => '',
   1597                         ),
   1598                         'host_access' => array(
   1599                                 'null' => false,
   1600                                 'type' => DB::FIELD_TYPE_INT,
   1601                                 'length' => 10,
   1602                                 'default' => '2',
   1603                         ),

[NOB]

Good luck

This might be just one part of the story and in the end might break your server and/or agent !

Think about it:

What if the agent executing this command has a limit of 255 characters but does
not check if a longer command arrives and executes this ?
It might work once, it might work twice, but overwriting some data at
the end of the memory (stack) might be a problem you'll notice later.

A similar thing is true for the server.
If it just reads the whole command in the DB but has a limit of 255 characters
the same memory corruption might happen.

You should at least check those sources and fix them if required, too !

Kind regards
Norbert.

[tiarnaigh]

Fair point NOB.
Wasn't the allowed size of the remote agent execution command increased from Zabbix v2.x onwards though to 2048 bytes, or something along those lines? I ran a few tests like the below for instance using the zabbix_get & system.run commands, and I seem to be good up to over the 500 character mark:

/sys_apps_01/zabbix/bin/zabbix_get -s 10.157.192.127 -k system.run['echo "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa a" > /tmp/test','wait'];


I didn't make any changes on the agent side (Guessing I'd need to hack the c code for this and recompile etc.), but merely on the servers side, which was just an update to the table and a change to the php config file. PHp shouldn't enforce any hard set memory limits I'm guessing....