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ssh won't ask for password unless i force PubkeyAuthentication=no (lemmy.ml)

submitted 2 months ago* (last edited 2 months ago) by [email protected] to c/[email protected]

15 comments fedilink hide all child comments

Lately I noticed that when I want to ssh to a server using a password I need to specify -o PubkeyAuthentication=no or I won't be asked for a password and the authentication will fail (well, for all I know, setting some other option may work too).

I use password authentication only once on freshly installed servers/vms, so it's not a huge deal, but... it still bothers me (mainly because I don't remember which option to set).

Do you guys have any idea what it may be?

client's ~/.ssh/config

Host 127.*.*.* 192.168.*.* 10.*.*.* 172.16.*.* 172.17.*.* 172.18.*.* 172.19.*.* 172.2?.*.* 172.30.*.* 172.31.*.*
  LogLevel quiet
  Stricthostkeychecking no
  Userknownhostsfile /dev/null

Host *
  ForwardAgent no
  AddKeysToAgent no
  Compression yes
  ServerAliveInterval 10
  ServerAliveCountMax 3
  HashKnownHosts no
  UserKnownHostsFile ~/.ssh/known_hosts
  ControlMaster no
  ControlPath ~/.ssh/master-%r@%n:%p
  ControlPersist no

server's /etc/ssh/sshd_config (it's from the nixos install iso)

AuthorizedPrincipalsFile none
Ciphers [email protected],[email protected],[email protected],aes256-ctr,aes192-ctr,aes128-ctr
GatewayPorts no
KbdInteractiveAuthentication yes
KexAlgorithms [email protected],curve25519-sha256,[email protected],diffie-hellman-group-exchange-sha256
LogLevel INFO
Macs [email protected],[email protected],[email protected]
PasswordAuthentication yes
PermitRootLogin yes
PrintMotd no
StrictModes yes
UseDns no
UsePAM yes
X11Forwarding no
Banner none
AddressFamily any
Port 22
Subsystem sftp /nix/store/78mv13w9mgh0s0rd7rnr6ff4d7a39bpd-openssh-9.7p1/libexec/sftp-server 
AuthorizedKeysFile %h/.ssh/authorized_keys /etc/ssh/authorized_keys.d/%u
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ed25519_key

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[–] [email protected] 2 points 2 months ago (2 children)

How would that improve security when all a bad actor has to do is add -o PubkeyAuthentication=no on their side?

Also, I'm pretty sure it used to just ask for a password?

[–] possiblylinux127 1 points 2 months ago

You would want to disable password authentication on the host.

I'm not part of the OpenSSH team so I don't know the rational of the defaults

[–] [email protected] 1 points 2 months ago

-o PubkeyAuthentication=no should only work if the server is configured to allow password auth at all. I believe the advice these days is to disable password auth completely for security.