Archive for the 'Uncategorized' Category

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rsyslog: do not collect logs from some application

If there’s no settings in the application itself, you can configure rsyslog not to write apps logs.

CentOS 6.6, rsyslog 5.8.10-10.el6_6:
Asterisk is configured to write logs to remote syslog server (syslog02.core) but still writes not only there but also locally.
To prevent this:
create ‘/etc/rsyslog.d/10-asterisk.conf’ with lines

:syslogtag, contains, "asterisk" @syslog02.core
& stop

Debian 9.4 Stretch, rsyslog 8.24.0-1:
Asterisk is nt configured to write to remote syslog, but also writes everything to local rsyslog.
Create ‘/etc/rsyslog.d/10-asterisk.conf’:

if $programname == "asterisk" then {
stop
}

https://www.rsyslog.com/doc/v8-stable/configuration/filters.html
https://www.rsyslog.com/discarding-unwanted-messages/

Debian 9: permanent iptables rules

Just an example for Debian 9.

1. Install ‘iptables-persistent’ package. Agree during installation the rules to be saved to /etc/iptables/rules.v4 .

2. Add rules (e.g. from console):

iptables -P OUTPUDT DROP
iptables -A OUTPUT -d 192.168.0.1 -j ACCEPT

3. Save rules:

netfilter-persistent save

4. Reboot and enjoy.

5. If you need to add/delete/edit rules, edit /etc/iptables/rules.v4 and then run ‘netfilter-persistent start’ to re-read the file.

SIP flood vs OpenSIPS armed with pike.so, exec.so, ipset and iptables

Preface: the PIKE module itself blocks SIP requests (just stops sending any replies) in case of flood. This article is about going on – adding flooding IP addresses to ipset for further rejecting any traffic to the OpenSIPS server using iptables.

1. Create an ipset with auto removing addresses after 120 seconds and ability to add comments.

ipset create SIPFLOOD hash:ip timeout 120 comment

2. An iptables rule, which will drop incoming traffic from src IP addresses from created ipset table:

iptables -A INPUT -m set --match-set SIPFLOOD src -j DROP

3. Allow OpenSIPS’ run-user (usually ‘opensips’) executing ‘ipset’ command without a password (add this line to /etc/sudoers using ‘visudo’ command):

opensips ALL= NOPASSWD: /sbin/ipset

4. OpenSIPS configuration.

Part of modules section of config:

#### exec
loadmodule "exec.so"

#### antiflood module
loadmodule "pike.so"
modparam("pike", "sampling_time_unit", 2)
modparam("pike", "reqs_density_per_unit", 10)
modparam("pike", "remove_latency", 120)

Part of OpenSIPS script, assuming that somebody sends us too much OPTIONS requests:

if(is_method("OPTIONS")) {

    pike_check_req();
    switch($retcode) {
        case -2:    # detected once - simply drop the request
            exit;
        case -1:    # detected again - ban the IP and drop request
            exec("/usr/bin/sudo ipset -exist add SIPFLOOD $si");
            exit;
    }

    sl_send_reply("200", "OK");
    exit;
}

5. You may test all this with ‘sipp’ tool.

This is for generating 10 requests (-r) in 2 seconds (-rp 2000) and exiting sipp after sending 10 requests (-m):

sipp 172.16.0.222 -r 10 -rp 2000 -m 10 -sf OPTIONS.xml

This – for generating 70 requests (-r) in 2 seconds (-rp 2000) and exiting sipp after sending 70 requests (-m):

sipp 172.16.0.222 -r 70 -rp 2000 -m 70 -sf OPTIONS.xml

The OPTIONS.xml is as follows:

UPD 2019-july-30: pike writes log messages (at least in automatic mode, but I’m sure that also in the manual ):

 Jul 30 06:59:05 ... /opensips[15531]: PIKE - BLOCKing ip 46.166.151.117, node=0x7f6dec201c08
Jul 30 06:59:05 ... /opensips[15533]: PIKE - UNBLOCKing node 0x7f6dec201b38
Jul 30 06:59:07 ... /opensips[15531]: PIKE - BLOCKing ip 46.166.151.163, node=0x7f6dec201d40

If you do not need all these messages (in case of SIP flood it may be too many), just set the log_level for pike.so module:

modparam("pike", "pike_log_level", 3)

And then set the log_level for your OpenSIPS to be not so verbose (pike’s log_level must be greater than global):

opensips-cli -x mi log_level 2

… or/and in config file:

log_level=2

iptables: a rule with expiration

If you need an automated way of deleting iptables rules after some time, use this:


iptables -A INPUT -s 9.8.7.6 -j DROP && { echo "iptables -D INPUT -s 9.8.7.6 -j DROP" | at now + 1 min; }

This rule will be deleted in a 1 minute.

OpenBSD PF: limit incoming connections per time period

In iptables there is a nice module called hashlimit.

Being in love with OpenBSD and PF, I decided to find if this wonderful firewall has the same feature.

As a minimal example, you can use this rule to allow =< 2 SSH connections per 60 seconds:

pass in on $ext_if proto tcp from any to any port 22 keep state (max-src-conn-rate 2/60)

Note that you have to use parentheses, even using just one option (max-src-conn-rate), otherwise you’ll get an error while parsing the ruleset.
Keep in mind that one of keep state, modulate state, or synproxy state must be specified explicitly to apply this option to a rule.

For more information read the documentation for pf.conf syntax.

OpenBSD: lack of RAM, reordering libraries at boot time and pkg_add errors

Freshly installed (in VirtualBox) OpenBSD 6.2 spent too much time during boot, on the ‘reordering libraries’ step. Several minutes, not less.
I havent’ seen such a behavior in prior releases.

As usual, thanks to guys from daemonforums.org.
And here are some explanations from Theo de Raadt: https://marc.info/?l=openbsd-tech&m=146159002802803&w=2.

But the problem was in lack of free memory: the VM had only 64 mb (default value in VirtualBox setting for OBSD) and it was not enough.

After adding more memory the boot process became quicker.

pkg_add(1) and pkg_info(1) havent’ worked properly either, until I added extra memory to the configuration.

Lighttpd: mod_access

lighttpd_logo I faced a problem when it was needed to allow access to certain url (x.x.x.x/zabbix/) for 2 fixed IP-addresses and one /16 subnet, and deny to anybody else.

The old examples from the official documentation worked not so perfect as I wanted https://redmine.lighttpd.net/boards/2/topics/1279
But the users helped me in the same topic.

This is how it’s done:

$HTTP["url"] =~ "^/zabbix/" {
    $HTTP["remoteip"] == "55.222.0.0/16" {
    }
    else $HTTP["remoteip"] == "11.22.33.44" {
    }
    else $HTTP["remoteip"] == "55.66.77.88" {
    }
    else $HTTP["remoteip"] != "" {  # (dummy match everything)
        url.access-deny = ( "" )
    }
}

Now anybody accessing /zabbix/ will get “403” error except 11.22.33.44 , 55.66.77.88 and 55.222.0.0/16.

OpenSIPS battle: REGISTER requests vs permissions module

UPDATE: this post restricts access based on source IP address. A new article shows how to restrict access (registrations) based on username.

Sutuation: you have to check the source address of REGISTER messages, going to your OpenSIPS server and decide wether to allow them or to deny.

Use permissions module for this.

You can use it in two variants:

1. with OpenSIPS’ text config files register.allow and register.deny (similar to Unix hosts.allow and hosts.deny).
In this case you should use module’s function ‘allow_register

Example of blocking REGISTERs from 10.145.13.49 IP address:

register.deny file:

ALL : "^sip:.*10\.145\.13\.49"
ALL : "^sip:.*0*10\.145\.0*13\.0*49"   # this is to prevent bypassing
                                       # by the insertion of one or more '0' in the IP address

register.allow file is empty (allow everything except those in .deny file).

OpenSIPS script snippet:

	if ( is_method("REGISTER") ) {
		if (allow_register("register")) {
			save("location");
			exit;
		} else {
			sl_send_reply("403", "Forbidden registration from your IP v2");
			exit;
		}
	}

But this method has one big disadvantage – you need to restart OpenSIPS each time you edit register.allow/register.deny.
OpenSIPS ‘permissions’ module has a MI function ‘address_reload‘ but it reloads the table (see below), not the allow/deny files.
So, it’s more cool to use the second variant, go on reading!..

2. with DB table ‘address‘.
In this case you should use modules’ function ‘check_address

– register.allow and register.deny files are empty.
– add entries to ‘address’ table. In our case we’re using not real SQL DB but dbtext. So, this is how ‘/etc/opensips/dbtext/address’ file looks like:

voip-pbx-sbc ~ # cat /etc/opensips/dbtext/address 
id(int,auto) grp(int) ip(string) mask(int) port(int) proto(string) pattern(string,null) context_info(string,null)
1:0:10.84.2.0:24:0:any
2:0:10.145.13.5:32:0:any
3:0:10.145.13.49:32:0:any
4:0:10.145.14.0:24:0:any

WARNING: every time you add any new table, do not forget to add it’s version to another table ‘version’:

voip-pbx-sbc ~ # cat /etc/opensips/dbtext/version 
table_name(string) table_version(int) 
dispatcher:8
load_balancer:2
address:5

Firstly, I haven’t done it, and that’s why OpenSIPS could not start and I had this message in the system log:

ERROR:core:db_check_table_version: invalid version 0 for table address found, expected 5

So, the script snippet with the ‘check_address’ function:

	if ( is_method("REGISTER") ) {

		if(check_address("0","$si","0","any")) {
			save("location");
			exit;
		} else {
			sl_send_reply("403", "Forbidden registration from your IP v2");
			exit;
		}

	}

And here’s the magic! You may add IP-addresses or subnets to your DB or dbtext file and then run a MI command ‘address_reload‘ without restarting your high-loaded OpenSIPS.

Now the policy is “if address is in the table – allow it, otherwise block”. Look at the images below.

IP is not in the table – REGISTER is forbidden:

IP has been added to dbtext table and table reloaded – registrations passed successfully:

You can also look the table’s contents with MI commands ‘opensipsctl fifo address_dump‘ and ‘opensipsctl fifo subnet_dump‘.

UPD: OpenSIPS core developer’s answer to my question http://lists.opensips.org/pipermail/users/2017-October/038169.html .

Asterisk: count active calls on certain peers

Let’s imagine that you have a number of peers – both internal users and trunks with VoIP providers.
And you need to count active calls on trunks only. Or even on trunks with some concrete provider, but not the total ‘core show calls’. As an example, you may need to pass that integer to Zabbix.

root@pbx:~# asterisk -C /etc/asterisk/asterisk.conf -rx 'sip show inuse' 
Setting max files open to 1000
* Peer name               In use          Limit           
104                       0/0/0           10              
107                       0/0/0           10              
100                       0/0/0           10                            
voip-isp-london1          1/0/0           6      
voip-isp-london2          2/1/0           6      
root@pbx:~# 

In fact, all magic is done with grep and especially awk tool. Firstly, you need to grep ‘voip-isp’, then extract the second column (is done with awk ‘{print $2}’ ) and then extract the first digit from three ones (e.g. 2 from 2/1/0).
At this point, you’ll get a list of integers, one per line, corresponding to number of active calls on each grepped trunk.
Now it’s time to summarize them, and the best way to do it is also awk! (is done with awk -F\/ ‘{sum += $1} END {print sum}’ )

root@pbx:~# asterisk -C /etc/asterisk/asterisk.conf -rx 'sip show inuse' | grep voip | awk '{print $2}' | awk -F\/ '{sum += $1} END {print sum}'
3

PBX backup script

#!/bin/bash

#***************************************#
#*****http://alexeyka.zantsev.com/******#
#***************************************#

BACKUP_DIR=/home/user/PBX_BACKUPS
TAR="/bin/tar -czf"
DATE=$(date +%Y-%m-%d)
CDRDAY=$(date +%d)
SQLDUMP="/usr/bin/mysqldump"
SRVNAME=pbx_

#------------------------------------------------
# function for backup routine
bkuper ()
{
	# 1. cd to dir
	cd $BACKUP_DIR
	mkdir BACKUP

	# 2. copy mission-critical shit
	for i in /etc/asterisk/ /etc/lighttpd/lighttpd.conf /etc/odbc.ini /etc/odbcinst.ini /var/scripts/ ;
	do
		/bin/cp -r $i BACKUP/
	done

	# 3. CDR SQL dump on 28 day monthly
	if [ $CDRDAY == 28 ]
	then
		$SQLDUMP -u root -pRoOtPaSsWoRd db_asterisk_cdr > BACKUP/db_asterisk_cdr.$DATE.sql
	fi

	# 4. archivate
	$TAR $SRVNAME$DATE.tar.gz BACKUP/

	# 5. delete shit
	/bin/rm -rf BACKUP/
}
#------------------------------------------------

# fire!
if [ -d $BACKUP_DIR ]
    then
	bkuper
    else
	/bin/mkdir $BACKUP_DIR
	bkuper
fi

# remove older than 30 days old backups
find $BACKUP_DIR -type f -name "*z" -mtime +30 -execdir rm -f {} \;

exit $?