EDITAR:
Al poner sshd en modo debug3, esto es lo que termina en:
lug 08 11:56:15 huaweipc sshd[113871]: Accepted publickey for paolo from 127.0.0.1 port 37762 ssh2: ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI
lug 08 11:56:15 huaweipc sshd[113871]: debug1: monitor_child_preauth: user paolo authenticated by privileged process
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_get_keystate: Waiting for new keys
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_receive_expect: entering, type 26
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_receive: entering
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_get_keystate: GOT new keys
lug 08 11:56:15 huaweipc sshd[113871]: debug1: auth_activate_options: setting new authentication options [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug2: userauth_pubkey: authenticated 1 pkalg ssh-ed25519 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: user_specific_delay: user specific delay 0.000ms [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: ensure_minimum_time_since: elapsed 7.204ms, delaying 6.530ms (requested 6.867ms) [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_do_pam_account entering [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_send: entering, type 102 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_receive_expect: entering, type 103 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_receive: entering [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_do_pam_account returning 1 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: send packet: type 52 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_request_send: entering, type 26 [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug3: mm_send_keystate: Finished sending state [preauth]
lug 08 11:56:15 huaweipc sshd[113871]: debug1: monitor_read_log: child log fd closed
lug 08 11:56:15 huaweipc sshd[113871]: debug3: ssh_sandbox_parent_finish: finished
lug 08 11:56:15 huaweipc sshd[113871]: debug1: PAM: establishing credentials
lug 08 11:56:15 huaweipc sshd[113871]: debug3: PAM: opening session
lug 08 11:56:15 huaweipc sshd[113871]: debug2: do_pam_session: auth information in SSH_AUTH_INFO_0
lug 08 11:56:15 huaweipc sshd[113871]: pam_unix(sshd:session): session opened for user paolo(uid=1000) by (uid=0)
¿Qué sucede después de la autenticación? ¿nada?
Tengo una pc xubuntu la cual no puedo conectar con ssh. Ya sea desde otros hosts o desde sí mismo (con ssh localhost), el proceso de autenticación está bien, pero ssh finaliza con un mensaje de tiempo de espera.
En modo detallado obtengo:
$ ssh -vvv localhost
OpenSSH_8.9p1 Ubuntu-3ubuntu0.1, OpenSSL 3.0.2 15 Mar 2022
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/home/paolo/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/home/paolo/.ssh/known_hosts2'
debug2: resolving "localhost" port 22
debug3: resolve_host: lookup localhost:22
debug3: ssh_connect_direct: entering
debug1: Connecting to localhost [127.0.0.1] port 22.
debug3: set_sock_tos: set socket 3 IP_TOS 0x10
debug1: Connection established.
debug1: identity file /home/paolo/.ssh/id_rsa type 0
debug1: identity file /home/paolo/.ssh/id_rsa-cert type -1
debug1: identity file /home/paolo/.ssh/id_ecdsa type -1
debug1: identity file /home/paolo/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/paolo/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/paolo/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/paolo/.ssh/id_ed25519 type 3
debug1: identity file /home/paolo/.ssh/id_ed25519-cert type -1
debug1: identity file /home/paolo/.ssh/id_ed25519_sk type -1
debug1: identity file /home/paolo/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/paolo/.ssh/id_xmss type -1
debug1: identity file /home/paolo/.ssh/id_xmss-cert type -1
debug1: identity file /home/paolo/.ssh/id_dsa type -1
debug1: identity file /home/paolo/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.9p1 Ubuntu-3ubuntu0.1
debug1: compat_banner: match: OpenSSH_8.9p1 Ubuntu-3ubuntu0.1 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to localhost:22 as 'paolo'
debug3: record_hostkey: found key type ED25519 in file /home/paolo/.ssh/known_hosts:38
debug3: load_hostkeys_file: loaded 1 keys from localhost
debug1: load_hostkeys: fopen /home/paolo/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug3: order_hostkeyalgs: have matching best-preference key type [email protected], using HostkeyAlgorithms verbatim
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: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,[email protected],diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],rsa-sha2-512,rsa-sha2-256
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],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: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,[email protected],diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256
debug2: host key algorithms: 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: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
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: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:PlciRlNWPOvPo2QAexfRn+Le/6tfdKK0RsFbqLsVsNs
debug3: record_hostkey: found key type ED25519 in file /home/paolo/.ssh/known_hosts:38
debug3: load_hostkeys_file: loaded 1 keys from localhost
debug1: load_hostkeys: fopen /home/paolo/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host 'localhost' is known and matches the ED25519 host key.
debug1: Found key in /home/paolo/.ssh/known_hosts:38
debug3: send packet: type 21
debug2: ssh_set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: ssh_set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: get_agent_identities: bound agent to hostkey
debug1: get_agent_identities: agent returned 2 keys
debug1: Will attempt key: /home/paolo/.ssh/id_ed25519 ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI agent
debug1: Will attempt key: /home/paolo/.ssh/id_rsa RSA SHA256:afMET60oaKoVI/jQUYhR/jBkouvf3KPnieBEUQH0V98 agent
debug1: Will attempt key: /home/paolo/.ssh/id_ecdsa
debug1: Will attempt key: /home/paolo/.ssh/id_ecdsa_sk
debug1: Will attempt key: /home/paolo/.ssh/id_ed25519_sk
debug1: Will attempt key: /home/paolo/.ssh/id_xmss
debug1: Will attempt key: /home/paolo/.ssh/id_dsa
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected]>
debug1: kex_input_ext_info: [email protected]=<0>
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,password
debug3: start over, passed a different list publickey,password
debug3: preferred gssapi-with-mic,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 public key: /home/paolo/.ssh/id_ed25519 ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI agent
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: /home/paolo/.ssh/id_ed25519 ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI agent
debug3: sign_and_send_pubkey: using [email protected] with ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI
debug3: sign_and_send_pubkey: signing using ssh-ed25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI
debug3: send packet: type 50
debug3: receive packet: type 52
Authenticated to localhost ([127.0.0.1]:22) using "publickey".
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: filesystem
Cada minuto se agrega una nueva línea:
debug3: send packet: type 80
El teclado no produce nada en la pantalla. Ctrl-c no interrumpe ssh
Después de 3 líneas de esas, obtengo
Timeout, server localhost not responding.
La configuración sshd es la predeterminada, tomada de /usr/share/openssh/sshd_config
sshd está activo y ejecutándose en el puerto 22:
$ sudo systemctl status ssh
● ssh.service - OpenBSD Secure Shell server
Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2023-07-08 10:33:51 AST; 14min ago
Docs: man:sshd(8)
man:sshd_config(5)
Process: 85624 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
Main PID: 85626 (sshd)
Tasks: 1 (limit: 8138)
Memory: 4.5M
CPU: 102ms
CGroup: /system.slice/ssh.service
└─85626 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"
lug 08 10:33:51 huaweipc systemd[1]: Stopped OpenBSD Secure Shell server.
lug 08 10:33:51 huaweipc systemd[1]: Starting OpenBSD Secure Shell server...
lug 08 10:33:51 huaweipc sshd[85626]: Server listening on 0.0.0.0 port 22.
lug 08 10:33:51 huaweipc systemd[1]: Started OpenBSD Secure Shell server.
lug 08 10:43:39 huaweipc sshd[92280]: Accepted publickey for paolo from 127.0.0.1 port 42416 ssh2: ED25519 SHA256:T6Dhpm0IYGrxJqUHUR7I44gdnrbBnPVET/DRC6wxaOI
lug 08 10:43:39 huaweipc sshd[92280]: pam_unix(sshd:session): session opened for user paolo(uid=1000) by (uid=0)
$ telnet localhost 22
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.1
$ netstat -l | grep ssh
tcp 0 0 0.0.0.0:ssh 0.0.0.0:* LISTEN
unix 2 [ ACC ] STREAM LISTENING 80364 /run/user/1000/gnupg/S.gpg-agent.ssh
unix 2 [ ACC ] STREAM LISTENING 396671 /tmp/ssh-XXXXXXFoIlQu/agent.35350
unix 2 [ ACC ] STREAM LISTENING 80533 /run/user/1000/keyring/ssh
unix 2 [ ACC ] STREAM LISTENING 102555 /run/user/1000/keyring/.ssh
Sin bloqueo de firewall:
$ sudo iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
$ sudo ufw status
State: inactive
La conexión a esta PC desde otra produce el mismo comportamiento de tiempo de espera.
¿Qué es este tiempo de espera?
Tengo otra pc xubuntu con la (aparentemente) misma configuración, pero ahí está todo ok.