Solucion de errores: SSH "Permission denied (publickey)". Luego de upgrade. Facil y rapido

En caso de que estes recibiendo el siguiente error al hacer un ssh:

"Permission denied (publickey)."

pero extrañamente venía funcionando todo quizás fue por un upgrade de openssh o del sistema operativo.

Lo primero que te recomiendo es realizar un ssh y con algo de debug (por ejemplo con el -v)

Quedarías así:

$ ssh -v -l alejandro miserver.com

Verás algo así:

$ ssh -v -l alejandro miserver.com

OpenSSH_7.6p1, LibreSSL 2.6.2

debug1: Reading configuration data /Users/alejandroacosta/.ssh/config

debug1: /Users/alejandroacosta/.ssh/config line 1: Applying options for *

debug1: Reading configuration data /etc/ssh/ssh_config

debug1: /etc/ssh/ssh_config line 49: Applying options for *

debug1: Connecting to miserver port 22.

debug1: Connection established.

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_rsa type -1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_rsa-cert type -1

debug1: identity file /Users/alejandroacosta/.ssh/id_dsa type 1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_dsa-cert type -1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_ecdsa type -1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_ecdsa-cert type -1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_ed25519 type -1

debug1: key_load_public: No such file or directory

debug1: identity file /Users/alejandroacosta/.ssh/id_ed25519-cert type -1

debug1: Local version string SSH-2.0-OpenSSH_7.6

debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8

debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8 pat OpenSSH_6.6.1* compat 0x04000000

debug1: Authenticating to miserver.com:22 as 'alejandro'

debug1: SSH2_MSG_KEXINIT sent

debug1: SSH2_MSG_KEXINIT received

debug1: kex: algorithm: curve25519-sha256@libssh.org

debug1: kex: host key algorithm: ecdsa-sha2-nistp256

debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: compression: none

debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: compression: none

debug1: expecting SSH2_MSG_KEX_ECDH_REPLY

debug1: Server host key: ecdsa-sha2-nistp256 SHA256:0CjzVIchz9571bMTChmp6cMZ+9QVogt9mHSaK8JA5VQ

debug1: Host '[miserver.com]:22' is known and matches the ECDSA host key.

debug1: Found key in /Users/alejandroacosta/.ssh/known_hosts:20

debug1: rekey after 134217728 blocks

debug1: SSH2_MSG_NEWKEYS sent

debug1: expecting SSH2_MSG_NEWKEYS

debug1: SSH2_MSG_NEWKEYS received

debug1: rekey after 134217728 blocks

debug1: Skipping ssh-dss key /Users/alejandroacosta/.ssh/id_dsa - not in PubkeyAcceptedKeyTypes

debug1: SSH2_MSG_SERVICE_ACCEPT received

debug1: Authentications that can continue: publickey

debug1: Next authentication method: publickey

debug1: Trying private key: /Users/alejandroacosta/.ssh/id_rsa

debug1: Trying private key: /Users/alejandroacosta/.ssh/id_ecdsa

debug1: Trying private key: /Users/alejandroacosta/.ssh/id_ed25519

debug1: No more authentication methods to try.

alejandro@miserver.com: Permission denied (publickey).

La linea mas importante es:

"debug1: Skipping ssh-dss key /Users/alejandroacosta/.ssh/id_dsa - not in PubkeyAcceptedKeyTypes"

Existen varias maneras de solucionarlo, muchas estan mencionadas en:

https://stackoverflow.com/questions/39715135/problems-deploying-code-with-capistrano-since-upgrading-to-macos-10-12-sierra

y

https://rolfje.wordpress.com/2016/11/12/macos-sierra-ssh-permission-denied/

Sin embargo si estas urgido, corriendo puedes solucionarlo inmediatamente haciendo esto:

Solución

echo "Host *" >> ~/.ssh/config

echo "PubkeyAcceptedKeyTypes=+ssh-dss" >> ~/.ssh/config

Mas información:

https://ro-che.info/articles/2015-12-21-permission-denied-publickey-ssh-update