Hi,
sorry for the answer in English.
SME Server 10 has limited access to only known secured ciphers and MACs algorithm. So this could be the issue you encounter.
Best way to debug your specific issue, is to
- first, read carefully the exact error offered by your client program ( Dall'errore di BackupAssist sembra che i sistemi non riescano a mettersi d'accordo sul modo di scambiarsi le informazioni di autorizzazione. )
- second, check your logs while trying to connect:
# tail -f /var/log/sshd/sshd.log
also here is the list of accepted ciphers and MACs :
KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
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,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
for information CentOS 7 default are
KexAlgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1, diffie-hellman-group1-sha1
Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-sha1-96,hmac-md5-96,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160@openssh.com
SME 9,8,7 allowed ciphers and encoding algorithms that are known to be insecure in 2021, so if your program does not allow one of the offered algorithm it might need to be updated.