Category: Sysadmin

Show which process/program is listening to what port using netstat and lsof

lsof -Pnl +M -i4
lsof -Pnl +M -i6

or

netstat -tulpn
netstat -npl

There are obviously a number of ways to accomplish this, but these variations will cover a lot of ground. You can also combine this with grep to filter out things you don’t need to see, or to only include specific processes and/or ports.

See post from @geek1968 on Instagram

Apache goodies for WordPress security

The list of things to do to harden a WordPress site with Apache is long, but some things that could be done include:

FileETag None                                                                                                                       
                                                                                                                                    
<Files wp-config.php>                                                                                                               
    Require all denied                                                                                                              
</Files>                                                                                                                            
                                                                                                                                    
<Files xmlrpc.php>                                                                                                                  
    Require all denied                                                                                                              
</Files>                                                                                                                            
                                                                                                                                    
<LocationMatch "/wp-content/uploads/.*(?i)\.php$">                                                                                  
    Require all denied                                                                                                              
</LocationMatch>

SSH tunnel to use other mailserver than localhost

Because I have a lot of virtual machines, laptops, work environments, and so on, I never seem to find the time to setup SMTP authentication everywhere. I typically use Linux for everything except hardcore gaming, so it’s only natural that I have some sort of mail server installed like Postfix. The problem in using that mail server to send e-mail is that I also quite often have dynamic IP addresses on these machines, which doesn’t work well with “e-mail protection” (well..) like SPF.

So instead of making my life very complicated, I have a trusted server on the Internet through which I send e-mail.

If you were looking for something fancy in this article, you can move along now, there’s nothing to see 🙂

To make all my Linux work instances believe they’re talking to an SMTP server locally, I simply setup a tunnel from the given Linux instance to this trusted server on the Internet using the ever so versatile OpenSSH / SSH. I know there are a lot of ways to do this, but this is what works for me:

Local machine or “where I work”

I have a private/public key keypair on all of these machines. The public key is placed in the /root/.ssh/authorized_keys file on the trusted server that is running the mail server.

On this machine, as root, I setup a tunnel that looks like this:

ssh -N -L 25:localhost:25 root@mail.example.org -p 2222

This will create a tunnel from “localhost” port 25 (where I work) to “localhost” port 25 on mail.example.org. It will connect the end point of the tunnel to mail.example.org on port 2222. If the mail.example.org server is running an SSH server on its standard port (22), you can remove the “-p 2222” part.

Mail server

On this server, I only need to put the public key from the local machine “where I work” into /root/.ssh/authorized_keys to allow the tunnel to come up.

When I access port 25 on my local machine “where I work”, it will be sent through the tunnel and then attempt to access “localhost” port 25 on the mail server. The mail server software, Postfix in my case, will never know this connection did not actually originate from “inside” the machine, but rather through the tunnel.

Closing thoughts

You can (obviously) make this somewhat more automated with tools like AutoSSH, init scripts, and what not. The above only intends to show how uncomplicated it is to create useful SSH/SMTP tunnels 🙂

 

Var är den oberoende och kompetenta myndigheten för IT?

Man kanske skall vara öppen med faktum att 2017 förmodligen INTE är det år som går till historien då flest snedtramp gjorts vad gäller IT och IT-driften hos myndigheter, riksdagen, osv. Snarare råkar vi, av “ren tur”, ha kommit på att detta skett och fortsätter att ske, med makthavarnas vetskap. Fortsätter det så här, så kanske vi skulle lägga upp samhällskritisk och i många fall hemlig information på en öppen server så att Google kan indexera det (göra det sökbart). Då riskerar vi i alla fall inte att tappa bort informationen och samtidigt sparar vi enorma mängder pengar. Win Win!

Men en större fråga tycker jag är: Varför har vi inte en oberoende myndighet som ansvarar för drift av och beslut gällande driften av IT-system inom offentlig förvaltning? Hur kommer det sig att vi 2017 får reda på att till och med regeringskansliet inte har någon som helst aning om vad de sysslar med och vilka risker man tar när man väljer att “lägga ut driften” eller “ta in kompetens”?

Även om jag principiellt inte är för att ytterligare komplicera och försvåra den redan ganska röriga byråkratin vi har, så känns det som att detta faktiskt skulle kunna vara motiverat. Det är för många dinosaurier, det är för många politiska tillsättningar och det saknas definitivt kunskaper.

Det kanske är dags att tillsätta en grupp människor och bilda en ny myndighet, där de tre yttersta kraven är IT-kunskap, sekretess och oberoende. När vi i de flesta andra situationer strävar efter att ha bäst kompetens på rätt plats, varför är det inte så när det gäller IT inom offentlig förvaltning?

Godtrohet är inte en giltig ursäkt för inkompetens.

Kanske skulle detta falla under MSBs ansvar, kanske inte.

Jag har sagt det tidigare och säger det igen: Vi har bara sett toppen på ett enormt isberg.

#svpol #fail #it #sakerhet

Forcing OutOfOffice response to always fire in Zimbra

We had a need to create an e-mail account in Zimbra that would always generate an automated response to incoming e-mails. So we activated the OutOfOffice functionality (or “Vacation Mode” as some people prefer to call it). This is great, and you do have some control from the ZWC (Zimbra Web Client) user interface.

The “problem” with the OOO functionality is that it is designed for human interaction. So, in an attempt to be somewhat “intelligent”, Zimbra will remember to whom it has sent an automated response message, and if a second message is received within nn time, it will not send another one. This makes sense, if I have sent an e-mail to John Doe, and Mr Doe is on vacation, I probably know this to be true even if I send him another message within a few hours or days. So I don’t want a second automated response.

We wanted it to send an automated response every time it received a message, zmprov to the rescue!

As the ‘zimbra’ user, from the CLI prompt, enter:

zmprov ma acct@tobemod.com zimbraPrefOutOfOfficeCacheDuration <value>

 

The default <value> in our installation was 7d, presumably that means seven days. So I set it to ‘1s’ and anyone sending e-mail to acct@tobemod.com now gets an automated response, even if they send several messages within a short period of time.

Troubles doing factory reset on a Ubiquiti EdgeRouter

If you’re having problems doing a factory reset on a Ubiquiti EdgeRouter, and can’t ping the router on 192.168.1.1 or connect to the admin web interface, you may want to check that you are connecting your computer to the eth0 port on the router. It’s not immediately obvious that this is where the admin interface is residing at https://192.168.1.1. Oh, and don’t forget to hardwire your own computer to the 192.168.1.0-network. This is really a no-brainer, but still not entirely obvious.

Slow SMTP sessions and SSH logins on your Zimbra server?

When upgrading a Zimbra server to a somewhat recent version (8.7.3 for example), it may attempt to install its own DNS Cache (zimbra-dnscache). It’s obvious that this may cause issues if you are running some other DNS caching service, or your own BIND, on the server. But these are rather obvious issues and not unique to Zimbra.

What is not, however, equally obvious is that you may think that zimbra-dnscache is actually running, and that it is actually doing what it is supposed to be doing.

My first hint that things weren’t as they appeared to be was extremely slow external SMTP sessions when clients like Thunderbird and other “client mailers”, as well as some web based Helpdesk applications were attempting to send e-mail via Zimbra.

The upgrade to Zimbra 8.7.3 had gone quite well, so it wasn’t an obvious place to start looking.

Until I noticed that SSH logins were also quite slow to this server. They had never been slow before. Checking the SSH configuration on the server did not reveal much other than the fact that it was indeed using reverse DNS lookups.

Checking /etc/resolv.conf made everything clear. Zimbra had, in attempt to use its own zimbra-dnscache, added “nameserver 127.0.0.1” to /etc/resolv.conf. In a perfect world, that may have been what I wanted …

After removing 127.0.0.1 from /etc/resolv.conf, inbound SMTP sessions from “client mailers” and web applications went from 7-10 seconds down to 0.5-0.1 seconds. Case closed.

I’m thinking Zimbra should add a post-installation sanity check. When all services are up and running, a DNS lookup to a known host (www.zimbra.com for example) should return within less than a second or two, anything else is an indication that the system may not function as intended.

#zimbra-dnscache