CHECK_NRPE: Receive header underflow - only 0 bytes received

[Yooshi]

Hello,

I've some difficult to use the NRPE plugin with nagios for monitor a windows server.

I've use this to install my NagiosCore/NagiosPlugins/NRPE :

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dpkg -l selinux*
apt-get update
apt-get install -y autoconf automake gcc libc6 libmcrypt-dev make libssl-dev wget unzip apache2 apache2-utils php libgd-dev bc gawk dc build-essential snmp libnet-snmp-perl gettext
cd /tmp
wget -O nagioscore.tar.gz https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.2.tar.gz
tar xzf nagioscore.tar.gz
cd /tmp/nagioscore-nagios-4.4.2/
./configure --with-httpd-conf=/etc/apache2/sites-enabled
make all
make install-groups-users
usermod -a -G nagios www-data
make install
make install-daemoninit
make install-commandmode
make install-config
make install-webconf
a2enmod rewrite
a2enmod cgi
iptables -I INPUT -p tcp --destination-port 80 -j ACCEPT
iptables -I INPUT -p tcp --destination-port 5666 -j ACCEPT
apt-get install -y iptables-persistent
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
systemctl restart apache2.service
systemctl start nagios.service
cd /tmp
wget --no-check-certificate -O nagios-plugins.tar.gz https://github.com/nagios-plugins/nagios-plugins/archive/release-2.2.1.tar.gz
tar zxf nagios-plugins.tar.gz
cd /tmp/nagios-plugins-release-2.2.1/
./tools/setup
./configure
make
make install
cd /tmp
wget --no-check-certificate -O nrpe.tar.gz https://github.com/NagiosEnterprises/nrpe/archive/nrpe-3.2.1.tar.gz
tar xzf nrpe.tar.gz
cd /tmp/nrpe-nrpe-3.2.1/
./configure --enable-command-args --disable-ssl
make all
make install-groups-users
make install
make install-config
echo >> /etc/services
echo '# Nagios services' >> /etc/services
echo 'nrpe    5666/tcp' >> /etc/services
make install-init
systemctl enable nrpe.service
sed -i '/^allowed_hosts=/s/$/,10.205.134.126,10.205.128.95/' /usr/local/nagios/etc/nrpe.cfg
sed -i 's/^dont_blame_nrpe=.*/dont_blame_nrpe=1/g' /usr/local/nagios/etc/nrpe.cfg
systemctl start nrpe.service

On my windows server, I've install NSClient++ (0.5.2.35 and 0.4.4.23 x64) and I installed it with the insecure legacy mode active and a blank password.

On my nagios server, when i run this command :

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/usr/local/nagios/libexec/check_nrpe -H 127.0.0.1

I've a correct answer : NRPE v3.2.1

But when i try with my windows server :

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/usr/local/nagios/libexec/check_nrpe -H 10.205.134.126

I've this : CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

I've already look a lot of topics but none can help me

You can find my nsclient.ini in attachment.

Thanks for ur help !

[tgriep]

The nsclient.ini file is missing some needed entries and that is causing the connection issue.
I attached a generic ini file to the post you can use to replace your copy with.
You will need to edit it and change the "allowed hosts" option and add the Nagios server's IP address to the list.
Make sure inbound port 5666 is allowed in on the Windows Firewall.
Save the file and restart NSClient++ on the Windows system and test it from the Nagios server.
If it fails, check the nsclient.log file on the Windows server for any errors and post them here.

[Yooshi]

Thanks for your help !

I will test that but i can't see your attachment ??

[tgriep]

I probably missed the upload so here it is again.

[Yooshi]

Its working !!! Thanks a lot tgriep for ur help !

First try doesn't work cause i've installed my NRPE on my Nagios with :

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--disable-ssl

But i've modify nsclient.ini and change this :

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use ssl = 1

to

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use ssl = 0

Now its working perfectly :

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root@nagios:/home/nagios# /usr/local/nagios/libexec/check_nrpe -H 10.205.128.95
I (0.5.2.35 2018-01-28) seem to be doing fine...

Thanks again for ur help !!

[tgriep]

Your very welcome. Glad it is working now. I'll close and mark the post for you but feel free to open a new post in the future for any new questions you may have.