SSH: Couldn't agree a key algorithm (available: curve25519-sha256@libssh.org)

RabidWolf9 · Aug 17, 2016, 11:15 PM

Putty 0.67 compiled on Debian Jessie 8.4 x64, will work on all Debian based variants, ie: Ubuntu, etc.
For Windows just download from Putty's website.

Will solve the issue "SSH: Couldn't agree a key algorithm (available: curve25519-sha256@libssh.org)"

http://www.legionit.net/downloads/putty_0.67-1_amd64.deb.tar.gz

Will compile FileZilla if any one needs it?

![Putty to pFsense - Couldnt agree on Key Exchange Algorith.png](/public/imported_attachments/1/Putty to pFsense - Couldnt agree on Key Exchange Algorith.png)
![Putty to pFsense - Couldnt agree on Key Exchange Algorith.png_thumb](/public/imported_attachments/1/Putty to pFsense - Couldnt agree on Key Exchange Algorith.png_thumb)

jimp · Aug 17, 2016, 11:20 PM

When it comes to security packages such as ssh clients, please only download them from official sources, check the hashes and signatures if possible. Don't download builds from random sources.

RabidWolf9 · Aug 17, 2016, 11:30 PM

Not having to compile in the first place would have been nice, however not offered on Putty's site and Git Hub is 0.63

However the Admin: jimp is right

MD5: be9fabbd1fd58e2b5dc4ff022400eadf

SHA1: b8e4b18743ed294d08220bbbb0b48105f0734850

SHA256: ec4092dc30c86679013e9e86ce949653a283e1000ab488bb40523b968970a850

nambi · Jan 6, 2017, 3:26 PM

No matter which version of putty I used it didn't work for my, strangely the same versions of putty work on my other pfsense box. I don't understand why? I tired clearing out he reg files but still no go, what DID work for me was using BITVISE ssh client. this worked without issues.

jimp · Jan 6, 2017, 3:35 PM

I have yet to see a case where updating PuTTY didn't work. Perhaps you are still running an old putty somehow (wrong shortcut/link, for example).

chrcoluk · Jan 6, 2017, 3:52 PM

@johnpoz:

yeah the issue I am having is with securecrt, you would think they would enabled chacha20 but not yet.. they just recently added ed25519..

But the dev version of putty has had both for quite some time.

That product director has driven me up the wall, her name maureen I think.

About a year or so ago I requested what I consider easy to adopt changes.

Support for chacha20
Support for gcm ciphers

To this day still no support.

Yet they have managed to do updates that affect the GUI design and some other stuff.

Seems their priority is making the program look pretty but not security enhancements.

https://forums.vandyke.com/showthread.php?t=12209
https://www.vandyke.com/products/securecrt/history.txt
https://s2-forums.vandyke.com/showthread.php?p=46666

very frustrating.

johnpoz · Jan 6, 2017, 5:28 PM

Yeah your right her name is Maureen from the thread.. Her last excuse

We have a fairly small develpment team and it can be a challenge to balance implementing new features, fixing bugs, and making sure our applications run on the latest version of the supported platforms.

My answer to that was putty has 1 guy coding ;) And it has had support pretty much since its been available ;)

I told her their product is dead to me.. Its completely useless if its not going to support modern ciphers and algo's.. The closest they have come is back in Jan of 2016 they added ECDSA and Ed25519 keys

doktornotor · Jan 7, 2017, 12:10 PM

For putty, really use the daily builds ONLY. ECDSA and Ed25519 is there as well. The stable release is not usable.

johnpoz · Jan 7, 2017, 3:16 PM

Yeah I use the dev bulds.. But as of late I just use kitty which is a fork of putty that supports everything as of a few updates back. Or I just use the windows build of openssh.. This is really the easiest way to know for sure your going to have full support of all the ciphers and algo's that openssh is using.

https://www.mls-software.com/opensshd.html

jimp · Jan 17, 2017, 11:13 PM

Good news, ChaCha20 is coming to SecureCRT

You previously requested support for the ChaCha20-Poly1305 cipher for SSH2
sessions. This has been implemented in a pre-beta version of SecureCRT and SecureFX.

If you would be interested in trying it, please let me know which product(s) and
platform(s) you need.

Products:

SecureCRT
SecureCRT and SecureFX

Platforms:

Windows (64-bit)
Windows (32-bit)
Mac OS X (10.11 and later)
Linux (Ubuntu 16.x, 64-bit)
Linux (Ubuntu 16.x, 32-bit)
Linux (Ubuntu 14.x and 15.x, 64-bit)
Linux (Ubuntu 14.x and 15.x, 32-bit)
Linux (RHEL 7.0)

johnpoz · Jan 19, 2017, 1:25 PM

Yeah I just emailed her, says on my thread to contact her for access to the prebeta ;)

chrcoluk · Jan 20, 2017, 12:48 AM

yeah she emailed me about it some days back, no GCM still but at least CHACHA is something.

johnpoz · Jan 20, 2017, 11:32 AM

So got the new secure beta.. And finally

[LOCAL] : Available Remote Send Ciphers = chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
[LOCAL] : Selected Send Cipher = chacha20-poly1305@openssh.com
[LOCAL] : Available Remote Recv Ciphers = chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
[LOCAL] : Selected Recv Cipher = chacha20-poly1305@openssh.com

Now they just need to add GCM ;)

riahc3 · Apr 20, 2017, 9:03 AM

@jimp:

FYI- We disabled some older, weaker, ssh key exchange algorithms. It won't be uncommon to find some older programs that use ssh directly or via things like libssh, that will need to be updated.

How do you reenable them?

johnpoz · Apr 20, 2017, 9:34 AM

Why would you need to re-enable them.. They have been disabled for a reason, ie not secure.. Update your client is the correct fix here..

riahc3 · Apr 20, 2017, 9:51 AM

@johnpoz:

Why would you need to re-enable them.. They have been disabled for a reason, ie not secure.. Update your client is the correct fix here..

Thats awesome.

How do you reenable them?

(For the record, yes, I am fully aware that many companies in 2016-2017, made SHA1 deprecated)

kpa · Apr 20, 2017, 9:53 AM

You re-enable them by rolling your own custom version of pfSense where you enable them in the openssh configuration. Oh and forget any official support if you follow that route.

riahc3 · Apr 20, 2017, 9:58 AM

@kpa:

You re-enable them by rolling your own custom version of pfSense where you enable them in the openssh configuration. Oh and forget any official support if you follow that route.

No.

From the posts in this thread, they were disabled not removed (ala PPTP). They should be able to be enabled (under your own responsability)

The issue for example is that PPTP was warned several months in advance that it was going to get removed. Maybe I missed it for SHA1 but…

The point is that this thread only talks about it is disabled, not removed so...

johnpoz · Apr 20, 2017, 10:39 AM

"How do you reenable them?"

You edit your sshd_conf to use the what you want.. But again I am going to stress they were disabled for a REASON!!!


[2.4.0-BETA][root@pfsense.local.lan]/etc/ssh: cat sshd_config 
# This file is automatically generated at startup
KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
Port 22
Protocol 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
Compression yes
ClientAliveInterval 30
PermitRootLogin yes
# Login via Key only
ChallengeResponseAuthentication no
PasswordAuthentication no
PubkeyAuthentication yes
UsePAM no
UseDNS no
LoginGraceTime 30s
VersionAddendum none
X11Forwarding no
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160,umac-128@openssh.com
# override default of no subsystems
Subsystem       sftp    /usr/libexec/sftp-server

Notice the part that says this file created at startup.. So you would have to edit sshd script that does the creation. Or you could use the sshd_extra file pretty sure..

I can not stress this enough - do not lower the security of your sshd, up the security of the client your using to access it. Putty is FREE it works just fine, they have a securecrt client closed beta you can get that supports the chacha stuff. You can use just the mls windows version of openssh, which is what I use all the time.. also FREE

You should never lower your security to "make something work"… This is just bad security 101..

What I did notice from this thread since I connected in with ssh -v into pfsense is they are behind on their ssh.. they are running 7.2 while 7.5 is current.

debug1: Local version string SSH-2.0-OpenSSH_7.5
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2
debug1: match: OpenSSH_7.2 pat OpenSSH* compat 0x04000000

riahc3 · Apr 20, 2017, 11:18 AM

@johnpoz:

"How do you reenable them?"

You edit your sshd_conf to use the what you want.. But again I am going to stress they were disabled for a REASON!!!
[2.4.0-BETA][root@pfsense.local.lan]/etc/ssh: cat sshd_config 
# This file is automatically generated at startup
KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
Port 22
Protocol 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
Compression yes
ClientAliveInterval 30
PermitRootLogin yes
# Login via Key only
ChallengeResponseAuthentication no
PasswordAuthentication no
PubkeyAuthentication yes
UsePAM no
UseDNS no
LoginGraceTime 30s
VersionAddendum none
X11Forwarding no
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160,umac-128@openssh.com
# override default of no subsystems
Subsystem       sftp    /usr/libexec/sftp-server
Notice the part that says this file created at startup.. So you would have to edit sshd script that does the creation. Or you could use the sshd_extra file pretty sure..

I can not stress this enough - do not lower the security of your sshd, up the security of the client your using to access it. Putty is FREE it works just fine, they have a securecrt client closed beta you can get that supports the chacha stuff. You can use just the mls windows version of openssh, which is what I use all the time.. also FREE

You should never lower your security to "make something work"… This is just bad security 101..

What I did notice from this thread since I connected in with ssh -v into pfsense is they are behind on their ssh.. they are running 7.2 while 7.5 is current.

debug1: Local version string SSH-2.0-OpenSSH_7.5
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2
debug1: match: OpenSSH_7.2 pat OpenSSH* compat 0x04000000

Quoted in case of removal.