Terrapin SSH Attack

aldomoro

This post is deleted!

stephenw10

@jimp said in Terrapin SSH Attack:

After applying the patch, reboot or restart the SSH daemon:

/usr/local/bin/php-cgi -f /etc/sshd

Like that. ^

DominikHoffmann

I take it, pfSense 24.03 has fixed this. Am I correct?

stephenw10

Yes it was patched in openssh 9.6.

[24.03-RELEASE][admin@4200.stevew.lan]/root: ssh -V
OpenSSH_9.6p1, OpenSSL 3.0.13 24 Oct 2023

lifeboy

@stephenw10 I see that CE 2.7.2 doesn't have openssh 9.6 yet. Does one manually have to upgrade openssh?

stephenw10

There is a patch in the system patches package to disable the affected ciphers. Apply it.

willowen100

Hi

I know this is an old post, I'd like to add that I too am having problems connecting from a Windows client PC using OpenSSH.

With the below patch applied
Workaround for Terrapin SSH Attack (After applying the patch, reboot or restart the SSH daemon, FreeBSD-SA-23:19.openssh, Terrapin Attack)

I get an error connecting

PS C:\Users\Will> ssh admin@192.168.5.1
Corrupted MAC on input.
ssh_dispatch_run_fatal: Connection to 192.168.5.1 port 22: message authentication code incorrect

After listing the MAC algorithms with

PS C:\Users\Will> ssh -Q mac
hmac-sha1
hmac-sha1-96
hmac-sha2-256
hmac-sha2-512
hmac-md5
hmac-md5-96
umac-64@openssh.com
umac-128@openssh.com
hmac-sha1-etm@openssh.com
hmac-sha1-96-etm@openssh.com
hmac-sha2-256-etm@openssh.com
hmac-sha2-512-etm@openssh.com
hmac-md5-etm@openssh.com
hmac-md5-96-etm@openssh.com
umac-64-etm@openssh.com
umac-128-etm@openssh.com

If I try connecting with the first MAC algorithm I get a prompt to try different ones

PS C:\Users\Will> ssh admin@192.168.5.1 -m hmac-sha1
Unable to negotiate with 192.168.5.1 port 22: no matching MAC found. Their offer: hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com

The only way to connect to pfSense via SSH is with

ssh admin@192.168.5.1 -m hmac-sha2-512

Once in pfSense I'm able to get the OpenSSH version

[2.7.2-RELEASE][admin@pfSense.lan]/root: ssh -V
OpenSSH_9.4p1, OpenSSL 3.0.12 24 Oct 2023

Some more information can be found here at the link below
https://serverfault.com/questions/994646/ssh-on-windows-corrupted-mac-on-input

Is there any fix with this on the pfSense CE edition?

STLJonny

@willowen100 See my reply, above in this thread, for a fix from the windows side.

willowen100

@STLJonny That works perfectly!

STLJonny

@willowen100 It basically forces your ssh (on the Windows side) to utilize that encryption algorithm. You'll need to do that on any machine you ssh from.

I'd have rather found a more elegant workaround (preferably on the pfSense side, so the mod only has to be done in one location), but this works in a pinch.