I reported an insecure DKIM key to Deutsche Telekom / T-Systems.

[janet_catcus@hachyderm.io]

@buherator @badkeys @mcr314 probably done by an apprentice anyway

[badrihippo@fosstodon.org]

@Diziet never even thought this could be a thing!

So you're basically making it impossible to prove through DKIM signatures that a given email was actually sent from your server?

@badkeys

[linear@nya.social]

@badkeys@infosec.exchange just a few days ago i broke an rsa384 key using yafu on my home server (a ~6 year old dell poweredge, fairly decent spec) as a practice run for something, and it took under 5 minutes

[linear@nya.social]

@badkeys@infosec.exchange the yafu help describes using siqs for this, which would take that server 2 to 3 hours, but using nfs it took only minutes

[momo@social.linux.pizza]

@bekopharm
Ich konnte sie auf ein Kontaktformular runterhandeln, musste aber versichern, dass der Transport dann nicht per eMail erfolgt. Ich habe ne ntfy-Instanz auf einem meiner Server laufen, das Webformular generiert jetzt eine Notification auf mein Smartphone.

Eigentlich wollte ich den Zugriff per Firewall auf die Admin-Netzwerke der Telekom zumachen, aber das war für sie absolut inakzeptabel.

Aber bei jeder Gelegenheit seine eigenen Kunden in Geiselhaft nehmen und rumprotzen, dass sie der größte Provider Deutschlands sind und damit eigene Regeln festlegen können, an die sich jeder zu halten hat.

[m_berberich@chaos.social]

@oscherler @tanja

Or they did not understand the problem?

[yama@tech.lgbt]

@lunareclipse @badkeys "bad companies", so most of them by nature ?

[yama@tech.lgbt]

@badkeys RSA ?
You can literally get an API key for your python script to access a literal quantum computer. And someone already made shors alg. implementation exclusively for RSA cracking

If it were over 4096 bits its still Not Secure and crackable within seconds.
Literally Any modern post quantum algorirthm is orders of magnitude better...

[diziet@mastodon.me.uk]

@badrihippo @badkeys Yes.

Everyone should be doing the same (rotating DKIM keys and publishing the old private keys). Here's my blog post on the subject:

https://diziet.dreamwidth.org/16025.html

[x0r@mamot.fr]

@badkeys Modern DKIM implementations should not accept signatures made with RSA keys smaller than 1024 bits, nowadays, so it seems unlikely to me that you could do anything nefarious with a key this weak. The verifier would be equally faulty if it accepts weak keys.

See also: https://www.rfc-editor.org/rfc/rfc8301#section-3.2

[woffs@fe.disroot.org]

@badkeys hot take: dkim does not matter anyway

[wpalant@infosec.exchange]

@badkeys Way to go Telekom! Last time I found a 320 bit RSA key it was “protecting” people’s private information (https://palant.info/2023/01/25/ipinside-koreas-mandatory-spyware/#how-is-this-data-protected) and I even had a little difficulty finding a cryptography library that wouldn’t refuse working with a key so short.

[trpalesz@mastodon.social]

@16af93 @q @badkeys iirc BSA recommends at least 3000bits

[varx@infosec.exchange]

@yama @badkeys Out of curiosity, what year are you posting from?

[yama@tech.lgbt]

@varx @badkeys Im not arguing with internet strangers. Go dive off a bridge mate

[j_r@social.jugendhacker.de]

@momo @bekopharm das dreisteste ist es hängt scheinbar stark davon ab welchen Support Mitarbeiter man erreicht. Hab Jahre lang damit gelebt einfach keine E-Mails an t-online senden zu können. Wurde irgendwann dann aber doch zu nervig und ich habe sie nochmal kontaktiert. Dann haben sie ohne große Nachfrage einfach meine IP freigeschaltet

[momo@social.linux.pizza]

@j_r
War bei mir ähnlich. Wer seinen Mailkram dann bei der Telekom hatte, hatte halt Pech. Zwischendrin hatte ich deren ASN im Spamfilter geblockt, weil ja, dann halt auch in beide Richtungen. Dann schlug aber der WAF Alarm und da blieb mir keine Wahl mehr... ich hab aber dann wohl beim Support-Lotto das falsche Ticket, gezogen.

(WAF= Wife Acceptance Factor)
@bekopharm

[stellated@mastodon.sdf.org]

@Bebef @kkarhan @momo @badkeys
Do y'all have any docs on this you could link? Is it a blanket automated check a la DKIM and SPF or is it something that's reviewed when appealing an anti-spam listing? My search queries aren't turning up much.

[bebef@mastodon.social]

@stellated @kkarhan @momo @badkeys It works like this: send an email to a Telekom recipient. Mail bounces with

<xxxxx@t-online.de>: host mx03.t-online.de[194.25.134.73] refused to talk to

me: 554 IP=1.2.3.4 - None/bad reputation. Ask your postmaster for help

or to contact tobr@rx.t-online.de for reset. (NOWL)

Send an email to tobr@rx.t-online.de, hilarity ensues.

(They send a reply pointing you to https://postmaster.t-online.de/#t4.1)

[bebef@mastodon.social]

@stellated @kkarhan @momo @badkeys Bit more discussion in German to be found here: https://borncity.com/blog/2025/02/25/merkwuerdige-vorschriften-bei-der-telekom-fuer-e-mail-versand/