SSH n'autorise les connexions distantes qu'après une connexion locale au serveur

Question

J'ai installé Ubuntu Server 16.04 32 bits sur mon ancien ordinateur portable avec connexion Internet (IP externe). Depuis le début, j'ai ajouté ufw et Fail2ban. Mais ensuite, j'ai découvert après un redémarrage que je ne pouvais pas entrer ssh sur le serveur à distance.

Après de nombreuses tentatives, j'ai finalement compris que ce n'était pas parce que j'avais configuré des exceptions sur Fail2ban ou parce que je désactivais ufw, le serveur ssh acceptait à nouveau les connexions distantes (temporairement jusqu'au prochain redémarrage).

Ce qui se passe dans mon cas, c'est que ssh ne commence à répondre qu'après une connexion locale au serveur.

Toute suggestion? Quelque chose lié au cryptage de mon répertoire utilisateur, peut-être?

SERVEUR AUTH.LOG

Feb 11 14:18:16 servername systemd-logind[1274]: System is rebooting.
Feb 11 14:19:14 servername CRON[1311]: pam_unix(cron:session): session opened for user root by (uid=0)
Feb 11 14:19:14 servername su[1374]: Successful su for noip by root
Feb 11 14:19:14 servername su[1374]: + ??? root:noip
Feb 11 14:19:14 servername su[1374]: pam_unix(su:session): session opened for user noip by (uid=0)
Feb 11 14:19:15 servername systemd-logind[1331]: New seat seat0.
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event3 (Power Button)
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event5 (Video Bus)
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event0 (Power Button)
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event1 (Lid Switch)
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event2 (Sleep Button)
Feb 11 14:19:15 servername systemd-logind[1331]: Watching system buttons on /dev/input/event9 (HP WMI hotkeys)
Feb 11 14:19:15 servername systemd: pam_unix(systemd-user:session): session opened for user noip by (uid=0)
Feb 11 14:19:15 servername systemd-logind[1331]: New session 1 of user noip.
Feb 11 14:19:15 servername su[1374]: pam_unix(su:session): session closed for user noip
Feb 11 14:19:16 servername sshd[1287]: Server listening on 0.0.0.0 port 22.
Feb 11 14:19:16 servername CRON[1311]: pam_unix(cron:session): session closed for user root
Feb 11 14:19:16 servername systemd-logind[1331]: Removed session 1.
Feb 11 14:19:16 servername systemd: pam_unix(systemd-user:session): session closed for user noip
Feb 11 14:19:44 servername sshd[1860]: Connection closed by x.x.x.x port 49743 [preauth]
Feb 11 14:20:01 servername login[1863]: pam_ecryptfs: Passphrase file wrapped
Feb 11 14:20:03 servername login[1410]: pam_unix(login:session): session opened for user noliva by LOGIN(uid=0)
Feb 11 14:20:03 servername systemd: pam_unix(systemd-user:session): session opened for user noliva by (uid=0)
Feb 11 14:20:03 servername systemd-logind[1331]: New session 2 of user noliva.
Feb 11 14:20:12 servername sshd[1942]: Accepted publickey for noliva from x.x.x.x port 49744 ssh2: RSA SHA256:yyyy
Feb 11 14:20:12 servername sshd[1942]: pam_unix(sshd:session): session opened for user noliva by (uid=0)
Feb 11 14:20:12 servername systemd-logind[1331]: New session 3 of user noliva.
Feb 11 14:20:25 servername Sudo:   noliva : TTY=pts/0 ; PWD=/home/noliva ; USER=root ; COMMAND=/usr/bin/vi /var/log/auth.log

CLIENT AVANT LA CONNEXION LOCALE AU SERVEUR:

iMac-de-noliva:log noliva$ ssh -v -v -v [email protected]
OpenSSH_7.3p1, LibreSSL 2.4.1
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 20: Applying options for *
debug2: resolving "x.x.x.x" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to x.x.x.x [x.x.x.x] port 22.
debug1: Connection established.
debug1: identity file /Users/noliva/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.1 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to x.x.x.x:22 as 'noliva'
debug3: hostkeys_foreach: reading file "/Users/noliva/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/noliva/.ssh/known_hosts:6
debug3: load_hostkeys: loaded 1 keys from x.x.x.x
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: Host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: Host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: [email protected]
debug1: kex: Host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server Host key: ecdsa-sha2-nistp256 SHA256:5KVog8lQVx18HDJnyjAqJTIyjfkbomRD75l817SPDXs
debug3: hostkeys_foreach: reading file "/Users/noliva/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/noliva/.ssh/known_hosts:6
debug3: load_hostkeys: loaded 1 keys from x.x.x.x
debug1: Host 'x.x.x.x' is known and matches the ECDSA Host key.
debug1: Found key in /Users/noliva/.ssh/known_hosts:6
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /Users/noliva/.ssh/id_rsa (0x7f94cf7000a0)
debug2: key: /Users/noliva/.ssh/id_dsa (0x0)
debug2: key: /Users/noliva/.ssh/id_ecdsa (0x0)
debug2: key: /Users/noliva/.ssh/id_ed25519 (0x0)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/noliva/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug1: Trying private key: /Users/noliva/.ssh/id_dsa
debug3: no such identity: /Users/noliva/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /Users/noliva/.ssh/id_ecdsa
debug3: no such identity: /Users/noliva/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /Users/noliva/.ssh/id_ed25519
debug3: no such identity: /Users/noliva/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).

CLIENT APRES LA CONNEXION LOCALE AU SERVEUR:

iMac-de-noliva:log noliva$ ssh -v -v -v [email protected]
OpenSSH_7.3p1, LibreSSL 2.4.1
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 20: Applying options for *
debug2: resolving "x.x.x.x" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to x.x.x.x [x.x.x.x] port 22.
debug1: Connection established.
debug1: identity file /Users/noliva/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/noliva/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.1 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to x.x.x.x:22 as 'noliva'
debug3: hostkeys_foreach: reading file "/Users/noliva/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/noliva/.ssh/known_hosts:6
debug3: load_hostkeys: loaded 1 keys from x.x.x.x
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: Host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: Host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: [email protected]
debug1: kex: Host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server Host key: ecdsa-sha2-nistp256 SHA256:5KVog8lQVx18HDJnyjAqJTIyjfkbomRD75l817SPDXs
debug3: hostkeys_foreach: reading file "/Users/noliva/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/noliva/.ssh/known_hosts:6
debug3: load_hostkeys: loaded 1 keys from x.x.x.x
debug1: Host 'x.x.x.x' is known and matches the ECDSA Host key.
debug1: Found key in /Users/noliva/.ssh/known_hosts:6
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /Users/noliva/.ssh/id_rsa (0x7fbebf420020)
debug2: key: /Users/noliva/.ssh/id_dsa (0x0)
debug2: key: /Users/noliva/.ssh/id_ecdsa (0x0)
debug2: key: /Users/noliva/.ssh/id_ed25519 (0x0)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/noliva/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug2: input_userauth_pk_ok: fp SHA256:yyyyy
debug3: sign_and_send_pubkey: RSA SHA256:xxxxx
Enter passphrase for key '/Users/noliva/.ssh/id_rsa': 

Answer 1

Le problème est que, tant que vous n'êtes pas connecté au système, votre dossier personnel est crypté et le fichier ~/.ssh/authorized_keys est inaccessible.

Une solution simple est décrite dans la section Dépannage de l'article SSH/OpenSSH/Keys de help.ubuntu.com .

Pour résoudre ce problème, créez un dossier en dehors de votre domicile nommé /etc/ssh/<username> (remplacez <username> par votre nom d'utilisateur actuel). Ce répertoire doit avoir 755 autorisations et être la propriété de l'utilisateur. Déplacez le fichier authorized_keys dans celui-ci. Le fichier authorized_keys doit avoir les autorisations 644 et être la propriété de l'utilisateur.

Puis éditez votre /etc/ssh/sshd_config et ajoutez:

AuthorizedKeysFile    /etc/ssh/%u/authorized_keys

---

Si vous voulez faire cela pour l'utilisateur actuel (et qu'il se trouve dans le groupe sudoers), la ligne de commande pourrait ressembler à ceci:

Sudo mkdir /etc/ssh/$USER
Sudo mv $HOME/.ssh/authorized_keys /etc/ssh/$USER/
Sudo chown -R $USER:$USER /etc/ssh/$USER
Sudo chmod 755 /etc/ssh/$USER
Sudo chmod 644 /etc/ssh/$USER/authorized_keys

^{* Où $USER et $HOME sont envvars et contiennent le nom d'utilisateur et le répertoire de base de l'utilisateur actuel.}

Editez ensuite votre /etc/ssh/sshd_config et modifiez la directive AuthorizedKeysFile de cette manière:

#AuthorizedKeysFile %h/.ssh/authorized_keys
AuthorizedKeysFile /etc/ssh/%u/authorized_keys

Redémarrez le serveur SSH:

Sudo systemctl restart ssh.service

C'est ça.

---

Références et autres approches:

• L'article "SSH/OpenSSH/Keys" de help.ubuntu.com
• question similaire dans Ask Ubunt
• ne réponse dans SuperUser
• Bug 362427 | L'authentification ssh de la clé publique ne fonctionne pas avec mon répertoire personnel crypté
• L'article "Répertoires personnels cryptés + Authentification par clé SSH" dans l'espace Stephen