How can I find a list of MACs, Ciphers, and KexAlgorithms that my openssh client supports?

Question

Is there a way to make ssh output what MACs, Ciphers, and KexAlgorithms that it supports?

I'd like to find out dynamically instead of having to look at the source.

score 117 · Accepted Answer · edited May 21 '18 at 21:00

117

Relevant OpenSSH man page: https://man.openbsd.org/ssh#Q

Ciphers: ssh -Q cipher
MACs: ssh -Q mac
KexAlgorithms: ssh -Q kex
PubkeyAcceptedKeyTypes: ssh -Q key

edited May 21 '18 at 21:00

jjlin

16,120

answered Jan 24 '15 at 20:05

nlu

1,421

eckes · Answer 2 · 2017-06-16T23:14:08.693

50

You can also remotely probe a ssh server for its supported ciphers with recent nmap versions:

nmap --script ssh2-enum-algos -sV -p <port> <host>

And there is an online service called sshcheck.com as well (and a pretty large number of similar scanner projects as I just found out).

edited Jun 16 '17 at 23:14

answered Jun 15 '17 at 22:37

eckes

1,330

score 18 · Answer 3 · edited Feb 19 '20 at 16:52

Some old versions of OpenSSH do not support the -Q option, but this works for any ssh and it has the benefit of showing both client and server options, without the need for any third party tools like nmap:

ssh -vv username@servername

Scan the output to see what ciphers, KEX algos, and MACs are supported...

by your client: "local client KEXINIT proposal"
by the server: "peer server KEXINIT proposal"

...
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
...
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
...

score 11 · Answer 4 · answered Jan 23 '18 at 03:42

Just a quick tip that if you want to compare 2 servers you can use @eckes method like this:

$ sdiff -bW <(nmap --script ssh2-enum-algos -sV -p 22 192.168.1.107) <(nmap --script ssh2-enum-algos -sV -p 22 192.168.1.10)

Starting Nmap 6.47 ( http://nmap.org ) at 2018-01-22 22:35 ES   Starting Nmap 6.47 ( http://nmap.org ) at 2018-01-22 22:35 ES
Nmap scan report for skinner.bubba.net (192.168.1.107)        | Nmap scan report for mulder.bubba.net (192.168.1.10)
Host is up (0.0037s latency).                                 | Host is up (0.0031s latency).
PORT   STATE SERVICE VERSION                                    PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 4.3 (protocol 2.0)               | 22/tcp open  ssh     OpenSSH 5.3 (protocol 2.0)
| ssh2-enum-algos:                                              | ssh2-enum-algos:
|   kex_algorithms: (3)                                       | |   kex_algorithms: (4)
                                                              > |       diffie-hellman-group-exchange-sha256
|       diffie-hellman-group-exchange-sha1                      |       diffie-hellman-group-exchange-sha1
|       diffie-hellman-group14-sha1                             |       diffie-hellman-group14-sha1
|       diffie-hellman-group1-sha1                              |       diffie-hellman-group1-sha1
|   server_host_key_algorithms: (2)                             |   server_host_key_algorithms: (2)
|       ssh-rsa                                                 |       ssh-rsa
|       ssh-dss                                                 |       ssh-dss
|   encryption_algorithms: (13)                                 |   encryption_algorithms: (13)
|       aes128-ctr                                              |       aes128-ctr
|       aes192-ctr                                              |       aes192-ctr
|       aes256-ctr                                              |       aes256-ctr
|       arcfour256                                              |       arcfour256
|       arcfour128                                              |       arcfour128
|       aes128-cbc                                              |       aes128-cbc
|       3des-cbc                                                |       3des-cbc
|       blowfish-cbc                                            |       blowfish-cbc
|       cast128-cbc                                             |       cast128-cbc
|       aes192-cbc                                              |       aes192-cbc
|       aes256-cbc                                              |       aes256-cbc
|       arcfour                                                 |       arcfour
|       rijndael-cbc@lysator.liu.se                             |       rijndael-cbc@lysator.liu.se
|   mac_algorithms: (6)                                       | |   mac_algorithms: (9)
|       hmac-md5                                                |       hmac-md5
|       hmac-sha1                                               |       hmac-sha1
                                                              > |       umac-64@openssh.com
                                                              > |       hmac-sha2-256
                                                              > |       hmac-sha2-512
|       hmac-ripemd160                                          |       hmac-ripemd160
|       hmac-ripemd160@openssh.com                              |       hmac-ripemd160@openssh.com
|       hmac-sha1-96                                            |       hmac-sha1-96
|       hmac-md5-96                                             |       hmac-md5-96
|   compression_algorithms: (2)                                 |   compression_algorithms: (2)
|       none                                                    |       none
|_      zlib@openssh.com                                        |_      zlib@openssh.com

Service detection performed. Please report any incorrect resu   Service detection performed. Please report any incorrect resu
Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds   | Nmap done: 1 IP address (1 host up) scanned in 0.22 seconds

In the above I'm showing a side-by-side diff of a CentOS 5.x and 6.x server.

$ ssh root@192.168.1.107 cat /etc/redhat-release
CentOS release 5.11 (Final)
$ ssh root@192.168.1.10 cat /etc/redhat-release
CentOS release 6.8 (Final)

The output shows you that you have 4 additional lines in the CentOS 6.x server vs. 5.x.

Reading the output

There's 1 additional kex_algorithm:

diffie-hellman-group-exchange-sha256

3 additional mac_algorithms:

umac-64@openssh.com
hmac-sha2-256
hmac-sha2-512

score 2 · Answer 5 · answered Oct 04 '22 at 12:03

2

# sudo sshd -T | egrep 'ciphers|macs|kexalgo'

answered Oct 04 '22 at 12:03

terrorclaw

31

How can I find a list of MACs, Ciphers, and KexAlgorithms that my openssh client supports?

5 Answers5

Reading the output