SSH: Não é possível fazer o login com a chave depois de desativar a autenticação de senha

Question

Eu tenho um servidor Ubuntu no Amazon EC2. Antes eu costumava fazer o login com o arquivo de chave pem original gerado na hora do lançamento.

ssh -i /path/to/key.pem [email protected]

Eu tentei parar a autenticação de senha e fiz as seguintes alterações no sshd_config.

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no 

Boom. A chave de login parou de funcionar e me deu o erro 'Permission Denied (publicKey)'.

O engraçado é que eu criei uma chave rsa para um usuário não-root usando o ssh-keygen. Isso funciona mesmo agora. Mas o arquivo de chaves ec2 pem não funcionará.

Nota: Se eu mudar o UsePam para 'yes', a tecla pem começa a funcionar novamente. Eu sou capaz de reproduzir esse problema em outra máquina. No entanto, na primeira máquina, perdi a capacidade de obter privilégios de root porque o arquivo de chaves não funcionava. Portanto, não é possível fazer alterações no arquivo sshd_config.

O registro ssh é semelhante ao seguinte.

OpenSSH_5.9p1 Debian-5ubuntu1.1, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to ec2-xx.xx.us-west-2.compute.amazonaws.com    [xx.xx.xx.xx] port 22.
debug1: Connection established.
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/amitoj/.ssh/backupshard.pem" as a RSA1 public key
debug1: identity file /home/amitoj/.ssh/backupshard.pem type -1
debug1: identity file /home/amitoj/.ssh/backupshard.pem-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1Debian-        5ubuntu1.1
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1.1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1.1
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "ec2-xx.xx.xx.xx.us-          west-2.compute.amazonaws.com" from file "/home/amitoj/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/amitoj/.ssh/known_hosts:70
debug3: load_hostkeys: loaded 1 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-       [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-    sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],[email protected],[email protected],ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdhsha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA 2d:19:d0:63:49:d9:f7:30:26:3f:6e:ff:8e:63:4d:c5
debug3: load_hostkeys: loading entries for host "ec2-xx.xx.xx.uswest-2.compute.amazonaws.com" from file "/home/amitoj/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/amitoj/.ssh/known_hosts:70
debug3: load_hostkeys: loaded 1 keys
debug3: load_hostkeys: loading entries for host "xx.xx.xx.xx" from file "/home/amit/.ssh/known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /home/amitoj/.ssh/known_hosts:71
debug3: load_hostkeys: loaded 1 keys
debug1: Host 'ec2-xx.xx.xx.xx.us-west-2.compute.amazonaws.com' is known and matches the ECDSA host key.
debug1: Found key in /home/amitoj/.ssh/known_hosts:70
debug1: ssh_ecdsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/amitoj/.ssh/backupshard.pem ((nil))
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred gssapi-keyex,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: Trying private key: /home/amitoj/.ssh/backupshard.pem
debug1: read PEM private key done: type RSA
debug3: sign_and_send_pubkey: RSA 69:ff:93:01:27:57:00:23:6e:2b:90:72:16:15:65:bb
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey).

Alguma ideia de como obter acesso ao usuário root com o arquivo de chave 'pem'?

    

Answer 1

Na próxima instanciação, use um dos recursos 'CloudInit' e forneça um Script de dados do usuário que editará / corrija 'sshd_config'. Um simples comando 'sed' deve funcionar.