News items for tag english - Koos van den Hout

2021-11-20 Setting the right SPF records
In debugging mail from the shell server I noticed something in the headers:
Authentication-Results:; spf=none;
        dkim=pass; dmarc=pass
The shell server sees itself as and uses this on locally generated outgoing mail. I only had an SPF record for so setting one up for too can help fix things. I also need a DMARC policy allowing mail from subdomains of, with more specific DMARC policies for active subdomains.

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2021-11-20 Publishing the information about using DKIM: dmarc records
After getting DKIM signing running with sendmail and opendkim I generated DKIM keys for, configured them in the mailserver with opendkim and published them in DNS. The next thing to publish is a policy record showing that all outgoing mail for these domains should be signed.

I started with a policy that shows mail should be signed but to not reject it when it isn't, but report it to me as unsigned.
;      IN      TXT

;; ANSWER SECTION: 86400 IN      TXT     "v=DMARC1;p=none;sp=reject;pct=100;rua=mailto:dmarcreports at;"
With a similar policy for Mail with problems shouldn't be rejected yet: DNS propagation isn't instantaneous and testing first.

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2021-11-20 Trying to get DKIM running
My recent issues with getting my e-mail delivered made me look at DKIM signing of outgoing e-mail messages. To not break things I have started testing this with outgoing e-mail from which normally publishes it doesn't send mail at all, so the first steps were to change that policy: changing the MX record and SPF record.

I started reading into configuring sendmail with dkim and found OpenDKIM which can work as a sendmail milter.

Based on How to configure DKIM & SPF & DMARC on Sendmail for multiple domains on CentOS 7 I took the same steps for my Devuan installation.

In Devuan (and probably Debian/Ubuntu) there is a opendkim package for the service and a opendkim-tools package for the associated tools. I needed the second one to get the opendkim-genkey command. I can imagine keys being generated/managed on a different system than the actual signing server.

After configuring this for including generating a keypair and publishing the public key via DNS I started sending test messages but had no luck. It turned out the sending host has to be in the InternalHosts table of opendkim. I added the address ranges and after that things started to work.

After fixing that I got the results I wanted:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;
        s=gosper; t=1637408594;
And a verification:
Authentication-Results:; spf=pass;
I was wondering about roaming users who authenticate to my mailserver and send messages that way. In a first test those messages get signed too. That means I can start signing mail from and other production domain names!
Read the rest of Trying to get DKIM running

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2021-11-19 Attacks on new sites are fast!
I was working on a new site for a project and requested a certificate for it. The time between the certificate being generated and the first attack was 3 minutes and 7 seconds.

15:12:10 UTC: certificate generated and published on the certificate transparancy log
15:15:17 UTC: - - [19/Nov/2021:16:15:17 +0100] "GET /restapi.php HTTP/1.1" 404 1008 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0"
15:15:18 UTC: - - [19/Nov/2021:16:15:18 +0100] "POST /gate.php HTTP/1.1" 404 1008 "-" "Dalvik/2.1.0 (Linux; U; Android 6.0.1; SM-J700F Build/MMB29K)"

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2021-11-15 Blocking mail I can't answer
Someone mailed me a few days ago with an interesting question. So I typed a reasonably long answer. But upon sending this answer I received the following error message:
   ----- The following addresses had permanent fatal errors -----
    (reason: 550 5.7.1 Unfortunately, messages from [] weren't sent. Please contact your Internet [])

   ----- Transcript of session follows -----
... while talking to
>>> MAIL From:<?????? .at.> SIZE=4837 BODY=8BITMIME
<<< 550 5.7.1 Unfortunately, messages from [] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to []
554 5.0.0 Service unavailable
Trying to get my IPv4 address allowed didn't work. The form for getting IP addresses whitelisted did not allow for IPv6 addresses, but then again has no IPv6 addresses listed for its MX record. I would think microsoft would do something with IPv6 to support innovations in Internet but I guess they only do that to win contracts.

After a while I got a response with a ticket number and an hour later a response that looked like maybe a person had taken a look at it, with "Our investigation has determined that the above IP(s) do not qualify for mitigation." So that leaves me with possible mails from outlook[.]com that I can't answer, making me look bad because I don't seem to reply at all.

I'm convinced the mail setup is correct on my end. The domain has an SPF record and the mail was sent out via the approved route.

The only solution I can think of at the moment is blocking mail from at the protocol level with an error message pointing at a webpage what the problem is, so when someone sends an e-mail from outlook[.]com to one of my domains they will get an error message with an embedded hint what they should do, namely We cannot reply to your mail, please send us mail from a different domain, see for an explanation. About the same as microsoft does, although the careful reader might have noticed the error code S3150 is not mentioned at

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2021-11-01 I participated in the CQWW DX Contest SSB
Last weekend was the CQ Worldwide DX Contest SSB and I participated Saturday and Sunday. This is a 48-hour contest so I had multiple chances for making radio contacts between other things to do in the weekend.

I was planning to participate in this contest with the idea of getting some new countries in the log, but propagation decided to not cooperate very well. Looking back at the log I see a number of 'well-known' stations: other amateur radio stations that I see active in other contests.

In the end I made 81 contacts on the 20, 15 and 10 meter bands. Overview:
Band   160   80   40   20   15   10
QSO's    0    0    0   75    2    4
Cty      0    0    0   27    2    3
Zone     0    0    0    5    2    2
Pts: 96  Mul: 41 Score: 3936

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2021-10-23 More 10 meter openings, and another new country
Things are going well with amateur radio: today I managed to make contacts with Australia and Indonesia on the 10 meter band in FT8 mode. That was a nice opening to the east, probably with some greyline on their side. It was morning here, so after the greyline for me.

And later when 10 meter was silent I tried the 20 meter band, where a station from New Caledonia answered my call. I realized later that was a new country/entity for me, by that time the contact was already confirmed!

Update 2021-10-25: Actually looking at maps made me realize New Caledonia is quite far away: the distance was about 16330 kilometers! I will need to tweak the generated maps on a bit to actually show the worked gridsquares in New Zealand and New Caledonia.

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2021-10-23 Something weird with sendmail and Let's Encrypt
Encrypt all the things meme Noticed this in the logs:
Sep 30 14:02:04 wozniak sendmail[25878]: STARTTLS=client,, version=TLSv1.3, verify=OK, cipher=TLS_AES_256_GCM_SHA384, bits=256/256
Sep 30 15:02:04 wozniak sendmail[27149]: STARTTLS=client,, version=TLSv1.3, verify=OK, cipher=TLS_AES_256_GCM_SHA384, bits=256/256
Sep 30 16:02:04 wozniak sendmail[28400]: STARTTLS=client,, version=TLSv1.3, verify=FAIL, cipher=TLS_AES_256_GCM_SHA384, bits=256/256
Sep 30 17:02:04 wozniak sendmail[29654]: STARTTLS=client,, version=TLSv1.3, verify=FAIL, cipher=TLS_AES_256_GCM_SHA384, bits=256/256
This is exactly the expiry of the DST Root CA:
koos@wozniak:/usr/share/ca-certificates/mozilla$ openssl x509 -in DST_Root_CA_X3.crt -noout -startdate -enddate
notBefore=Sep 30 21:12:19 2000 GMT
notAfter=Sep 30 14:01:15 2021 GMT
But now to find out where this goes wrong...
Read the rest of Something weird with sendmail and Let's Encrypt

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2021-10-22 Naming interfaces used by libvirt virtual machines
The homeserver conway has an ever growing list of network interfaces, also due to adding a DMZ network.

This was starting to look a bit messy, with things like:
koos@conway:~$ /sbin/brctl show brwireless
bridge name     bridge id               STP enabled     interfaces
brwireless              8000.4ccc6a8efa4b       no              enp10s0.3
Solution: name the interfaces in the VM definitions, like:
    <interface type='bridge'>
      <source bridge='brdmz'/>
      <target dev='dmz-minsky'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
And now names are more logical:
koos@conway:~$ /sbin/brctl show brdmz
bridge name     bridge id               STP enabled     interfaces
brdmz           8000.4ccc6a8efa4b       no              dmz-minsky

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2021-10-18 Securing the home network: a separate DMZ network
I have a lot of control over the software that runs on systems at home but there are limits to what I can fix and sometimes things are insecure.

Things like the recent wordpress brute force attacks show that random 'loud' attackers who don't care about the chance of getting noticed will try. I sometimes do worry about the silent and more targeted attackers.

So recently I updated my home network and I now have a DMZ network. At this moment it is a purely virtual network as it doesn't leave the KVM server. Hosts in the DMZ have a default-deny firewall policy to the other inside networks. Specific services on specific hosts have been enabled.

I first moved the development webserver, which allowed me to tune those firewall rules and fix some other errors.

Now other webservers and other servers offering things to the outside world have moved.

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IPv6 check

Running test...
, reachable as PGP encrypted e-mail preferred. PGP key 5BA9 368B E6F3 34E4 local copy PGP key 5BA9 368B E6F3 34E4 via keyservers

Meningen zijn die van mezelf, wat ik schrijf is beschermd door auteursrecht. Sommige publicaties bevatten een expliciete vermelding dat ze ongevraagd gedeeld mogen worden.
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Other webprojects: Camp Wireless, wireless Internet access at campsites, The Virtual Bookcase, book reviews
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