Как перечислить доступные алгоритмы ключей хоста для клиента SSH?

Кажется, никто -не читал документацию, касающуюся флага -Qдля ssh, должным образом.

man sshговорит:

-Q query_option
             Queries ssh for the algorithms supported for the specified version 2.  The available features are:
             cipher (supported symmetric ciphers), cipher-auth (supported symmetric ciphers that support authenti‐
             cated encryption), help (supported query terms for use with the -Q flag), mac (supported message integ‐
             rity codes), kex (key exchange algorithms), kex-gss (GSSAPI key exchange algorithms), key (key types),
             key-cert (certificate key types), key-plain (non-certificate key types), key-sig (all key types and sig‐
             nature algorithms), protocol-version (supported SSH protocol versions), and sig (supported signature al‐
             gorithms).  Alternatively, any keyword from ssh_config(5) or sshd_config(5) that takes an algorithm list
             may be used as an alias for the corresponding query_option.

Вот как использовать ssh -Qдля вывода всей доступной информации об установленной версии ssh:

for F in $(ssh -Q help); do 
  printf "=== $F ===\n"
  ssh -Q $F
  echo ""
done

Результат для меня был:

=== cipher ===
3des-cbc
aes128-cbc
aes192-cbc
aes256-cbc
rijndael-cbc@lysator.liu.se
aes128-ctr
aes192-ctr
aes256-ctr
aes128-gcm@openssh.com
aes256-gcm@openssh.com
chacha20-poly1305@openssh.com

=== cipher-auth ===
aes128-gcm@openssh.com
aes256-gcm@openssh.com
chacha20-poly1305@openssh.com

=== 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

=== kex ===
diffie-hellman-group1-sha1
diffie-hellman-group14-sha1
diffie-hellman-group14-sha256
diffie-hellman-group16-sha512
diffie-hellman-group18-sha512
diffie-hellman-group-exchange-sha1
diffie-hellman-group-exchange-sha256
ecdh-sha2-nistp256
ecdh-sha2-nistp384
ecdh-sha2-nistp521
curve25519-sha256
curve25519-sha256@libssh.org
sntrup4591761x25519-sha512@tinyssh.org

=== kex-gss ===
gss-gex-sha1-
gss-group1-sha1-
gss-group14-sha1-
gss-group14-sha256-
gss-group16-sha512-
gss-nistp256-sha256-
gss-curve25519-sha256-

=== key ===
ssh-ed25519
ssh-ed25519-cert-v01@openssh.com
sk-ssh-ed25519@openssh.com
sk-ssh-ed25519-cert-v01@openssh.com
ssh-rsa
ssh-dss
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
sk-ecdsa-sha2-nistp256@openssh.com
ssh-rsa-cert-v01@openssh.com
ssh-dss-cert-v01@openssh.com
ecdsa-sha2-nistp256-cert-v01@openssh.com
ecdsa-sha2-nistp384-cert-v01@openssh.com
ecdsa-sha2-nistp521-cert-v01@openssh.com
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com

=== key-cert ===
ssh-ed25519-cert-v01@openssh.com
sk-ssh-ed25519-cert-v01@openssh.com
ssh-rsa-cert-v01@openssh.com
ssh-dss-cert-v01@openssh.com
ecdsa-sha2-nistp256-cert-v01@openssh.com
ecdsa-sha2-nistp384-cert-v01@openssh.com
ecdsa-sha2-nistp521-cert-v01@openssh.com
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com

=== key-plain ===
ssh-ed25519
sk-ssh-ed25519@openssh.com
ssh-rsa
ssh-dss
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
sk-ecdsa-sha2-nistp256@openssh.com

=== key-sig ===
ssh-ed25519
ssh-ed25519-cert-v01@openssh.com
sk-ssh-ed25519@openssh.com
sk-ssh-ed25519-cert-v01@openssh.com
ssh-rsa
rsa-sha2-256
rsa-sha2-512
ssh-dss
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
sk-ecdsa-sha2-nistp256@openssh.com
ssh-rsa-cert-v01@openssh.com
rsa-sha2-256-cert-v01@openssh.com
rsa-sha2-512-cert-v01@openssh.com
ssh-dss-cert-v01@openssh.com
ecdsa-sha2-nistp256-cert-v01@openssh.com
ecdsa-sha2-nistp384-cert-v01@openssh.com
ecdsa-sha2-nistp521-cert-v01@openssh.com
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com

=== protocol-version ===
2

=== sig ===
ssh-ed25519
sk-ssh-ed25519@openssh.com
ssh-rsa
rsa-sha2-256
rsa-sha2-512
ssh-dss
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
sk-ecdsa-sha2-nistp256@openssh.com

При отладке может быть полезно запросить конфигурацию, которая фактически используется sshпри попытке подключения к хосту с использованием параметра -G. В нем будут перечислены все параметры конфигурации, включая выбранные значения параметров cipher, mac, hostKeyAlgorithmи KexAlgorithm.

ssh -G user@somehost.example.com

Вот типичный вывод:

user ubuntu
hostname 35.171.333.444
port 22
addkeystoagent false
addressfamily any
batchmode no
canonicalizefallbacklocal yes
canonicalizehostname false
challengeresponseauthentication yes
checkhostip yes
compression yes
controlmaster false
enablesshkeysign no
clearallforwardings no
exitonforwardfailure no
fingerprinthash SHA256
forwardx11 yes
forwardx11trusted yes
gatewayports no
gssapiauthentication yes
gssapikeyexchange no
gssapidelegatecredentials no
gssapitrustdns no
gssapirenewalforcesrekey no
gssapikexalgorithms gss-group14-sha256-,gss-group16-sha512-,gss-nistp256-sha256-,gss-curve25519-sha256-,gss-group14-sha1-,gss-gex-sha1-
hashknownhosts yes
hostbasedauthentication no
identitiesonly no
kbdinteractiveauthentication yes
nohostauthenticationforlocalhost no
passwordauthentication yes
permitlocalcommand no
proxyusefdpass no
pubkeyauthentication yes
requesttty auto
streamlocalbindunlink no
stricthostkeychecking ask
tcpkeepalive yes
tunnel false
verifyhostkeydns false
visualhostkey no
updatehostkeys false
canonicalizemaxdots 1
connectionattempts 1
forwardx11timeout 1200
numberofpasswordprompts 3
serveralivecountmax 3
serveraliveinterval 0
ciphers chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
hostkeyalgorithms ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-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,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com,ssh-ed25519,sk-ssh-ed25519@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
hostbasedkeytypes ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-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,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com,ssh-ed25519,sk-ssh-ed25519@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
ignoreunknown Password
kexalgorithms 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
casignaturealgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com,ssh-ed25519,sk-ssh-ed25519@openssh.com,rsa-sha2-512,rsa-sha2-256
loglevel INFO
macs 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
securitykeyprovider internal
pubkeyacceptedkeytypes ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-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,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com,ssh-ed25519,sk-ssh-ed25519@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
xauthlocation /usr/bin/xauth
identityfile ~/.ssh/rsa-2020-11-03
canonicaldomains
globalknownhostsfile /etc/ssh/ssh_known_hosts /etc/ssh/ssh_known_hosts2
userknownhostsfile ~/.ssh/known_hosts ~/.ssh/known_hosts2
sendenv LANG
sendenv LC_*
forwardagent yes
connecttimeout none
tunneldevice any:any
controlpersist no
escapechar ~
ipqos lowdelay throughput
rekeylimit 0 0
streamlocalbindmask 0177
syslogfacility USER

Поскольку этот вопрос является #1 ответом при поиске 'list ssh "алгоритмы обмена ключами"', я также предложу этот ответ:

Список алгоритмов обмена ключами ssh клиента :ssh -Q kex

Список алгоритмов обмена ключами ssh на сервере :sudo sshd -T | grep kex