I tried to set up private/public key authentication on my server (CentOS). Here are the steps I made:
- Generated a public/private keypair with puttygen
- Copied the public key to the server and appended it with the cat command to the file /root/.ssh/authorized_keys
- Checked suggested file ownership and permissions for .ssh (700) and .ssh/authorized_keys (600)
- Restarted the sshd service
- In the Putty config under Connection > SSH > Auth, selected the privat key
But when I try to connect with Putty, I get the message "Server refused our key". I am prompted for password then, and that works.
I also raised the authentication log level, here is the output for a failed attempt:
Aug 30 12:55:01 localhost sshd[44558]: debug3: fd 5 is not O_NONBLOCK
Aug 30 12:55:01 localhost sshd[44558]: debug1: Forked child 44752.
Aug 30 12:55:01 localhost sshd[44558]: debug3: send_rexec_state: entering fd = 8 config len 803
Aug 30 12:55:01 localhost sshd[44558]: debug3: ssh_msg_send: type 0
Aug 30 12:55:01 localhost sshd[44558]: debug3: send_rexec_state: done
Aug 30 12:55:01 localhost sshd[44752]: debug3: oom_adjust_restore
Aug 30 12:55:01 localhost sshd[44752]: Set /proc/self/oom_score_adj to 0
Aug 30 12:55:01 localhost sshd[44752]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8
Aug 30 12:55:01 localhost sshd[44752]: debug1: inetd sockets after dupping: 3, 3
Aug 30 12:55:01 localhost sshd[44752]: Connection from 91.15.164.238 port 58557 on 82.165.78.188 port 22
Aug 30 12:55:01 localhost sshd[44752]: debug1: Client protocol version 2.0; client software version PuTTY_Release_0.70
Aug 30 12:55:01 localhost sshd[44752]: debug1: no match: PuTTY_Release_0.70
Aug 30 12:55:01 localhost sshd[44752]: debug1: Enabling compatibility mode for protocol 2.0
Aug 30 12:55:01 localhost sshd[44752]: debug1: Local version string SSH-2.0-OpenSSH_6.6.1
Aug 30 12:55:01 localhost sshd[44752]: debug2: fd 3 setting O_NONBLOCK
Aug 30 12:55:01 localhost sshd[44752]: debug3: ssh_sandbox_init: preparing rlimit sandbox
Aug 30 12:55:01 localhost sshd[44752]: debug2: Network child is on pid 44753
Aug 30 12:55:01 localhost sshd[44752]: debug3: preauth child monitor started
Aug 30 12:55:01 localhost sshd[44752]: debug1: SELinux support disabled [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: privsep user:group 74:74 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: permanently_set_uid: 74/74 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: list_hostkey_types: ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: SSH2_MSG_KEXINIT sent [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: SSH2_MSG_KEXINIT received [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [email protected],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 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: none,[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: none,[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: first_kex_follows 0 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: reserved 0 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,rsa2048-sha256,rsa1024-sha1,diffie-hellman-group1-sha1 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: ssh-rsa,ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-dss [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: aes256-ctr,aes256-cbc,[email protected],aes192-ctr,aes192-cbc,aes128-ctr,aes128-cbc,[email protected],blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc,arcfour256,arcfour128 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: aes256-ctr,aes256-cbc,[email protected],aes192-ctr,aes192-cbc,aes128-ctr,aes128-cbc,[email protected],blowfish-ctr,blowfish-cbc,3des-ctr,3des-cbc,arcfour256,arcfour128 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha1,hmac-sha1-96,hmac-md5,[email protected],[email protected],[email protected],[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha1,hmac-sha1-96,hmac-md5,[email protected],[email protected],[email protected],[email protected] [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: none,zlib [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: none,zlib [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: first_kex_follows 0 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_parse_kexinit: reserved 0 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: mac_setup: setup hmac-sha2-256 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: kex: client->server aes256-ctr hmac-sha2-256 none [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: mac_setup: setup hmac-sha2-256 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: kex: server->client aes256-ctr hmac-sha2-256 none [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: kex: [email protected] need=32 dh_need=32 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 120 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 121 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:01 localhost sshd[44752]: debug3: monitor_read: checking request 120
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 121
Aug 30 12:55:01 localhost sshd[44752]: debug1: kex: [email protected] need=32 dh_need=32 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 120 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 121 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:01 localhost sshd[44752]: debug3: monitor_read: checking request 120
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 121
Aug 30 12:55:01 localhost sshd[44752]: debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_key_sign entering [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 6 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 7 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:01 localhost sshd[44752]: debug3: monitor_read: checking request 6
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_answer_sign
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_answer_sign: signature 0x7f0b70e15390(271)
Aug 30 12:55:01 localhost sshd[44752]: debug3: mm_request_send entering: type 7
Aug 30 12:55:01 localhost sshd[44752]: debug2: monitor_read: 6 used once, disabling now
Aug 30 12:55:01 localhost sshd[44752]: debug2: kex_derive_keys [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: set_newkeys: mode 1 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: SSH2_MSG_NEWKEYS sent [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: expecting SSH2_MSG_NEWKEYS [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug2: set_newkeys: mode 0 [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: SSH2_MSG_NEWKEYS received [preauth]
Aug 30 12:55:01 localhost sshd[44752]: debug1: KEX done [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: userauth-request for user root service ssh-connection method none [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: attempt 0 failures 0 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_getpwnamallow entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 8 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 9 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 8
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_pwnamallow
Aug 30 12:55:04 localhost sshd[44752]: debug3: Trying to reverse map address 91.15.164.238.
Aug 30 12:55:04 localhost sshd[44752]: debug2: parse_server_config: config reprocess config len 803
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 9
Aug 30 12:55:04 localhost sshd[44752]: debug2: monitor_read: 8 used once, disabling now
Aug 30 12:55:04 localhost sshd[44752]: debug2: input_userauth_request: setting up authctxt for root [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_start_pam entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 100 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_inform_authserv entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 4 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_inform_authrole entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 80 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug2: input_userauth_request: try method none [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: userauth_finish: failure partial=0 next methods="publickey,gssapi-keyex,gssapi-with-mic,password" [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 100
Aug 30 12:55:04 localhost sshd[44752]: debug1: PAM: initializing for "root"
Aug 30 12:55:04 localhost sshd[44752]: debug1: PAM: setting PAM_RHOST to "p5b0fa4ee.dip0.t-ipconnect.de"
Aug 30 12:55:04 localhost sshd[44752]: debug1: PAM: setting PAM_TTY to "ssh"
Aug 30 12:55:04 localhost sshd[44752]: debug2: monitor_read: 100 used once, disabling now
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 4
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_authserv: service=ssh-connection, style=
Aug 30 12:55:04 localhost sshd[44752]: debug2: monitor_read: 4 used once, disabling now
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 80
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_authrole: role=
Aug 30 12:55:04 localhost sshd[44752]: debug2: monitor_read: 80 used once, disabling now
Aug 30 12:55:04 localhost sshd[44752]: debug1: userauth-request for user root service ssh-connection method publickey [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: attempt 1 failures 0 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug2: input_userauth_request: try method publickey [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: test whether pkalg/pkblob are acceptable [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_key_allowed entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 22 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_key_allowed: waiting for MONITOR_ANS_KEYALLOWED [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 23 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 22
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_keyallowed entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_keyallowed: key_from_blob: 0x7f0b70e1ca10
Aug 30 12:55:04 localhost sshd[44752]: debug1: temporarily_use_uid: 0/0 (e=0/0)
Aug 30 12:55:04 localhost sshd[44752]: debug1: trying public key file /root/.ssh/authorized_keys
Aug 30 12:55:04 localhost sshd[44752]: debug1: fd 4 clearing O_NONBLOCK
Aug 30 12:55:04 localhost sshd[44752]: debug2: key_type_from_name: unknown key type '----'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing keytype
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: '---- BEGIN SSH2 PUBLIC KEY ----\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug2: key_type_from_name: unknown key type 'BEGIN'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing keytype
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: 'BEGIN SSH2 PUBLIC KEY ----\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug2: key_type_from_name: unknown key type 'Comment:'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing keytype
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: 'Comment: "rsa-key-20170830"\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: '"rsa-key-20170830"\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: 'AAAAB3NzaC1yc2EAAAABJQAAAQEAkO9lXNIVuohGAOsCQy+NDIJv7a+a6z6ekmSp\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: 'HfFduHAvOadeX/HDidL1696CVOHjX8fJ7ITTCaFl2ljI06lobZ2baDAsezpMhut9\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: 'xmovTOmTJK3pOAI9E1S3Hmhum0QViFsE5oCiMHwZixLmWoeZt09ZwSZyQZAvtHTU\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: '73bviqiky/j2xYpG+5QKyViyCEAa6KbJKnGpLw8UTf0rEBhUES9wLBt4vU3AZuQd\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: 'evfZSr3lDBlCCdX3vyJJP8m4x3+8YMSvJSfKa9MErWpxjNE+4GMhyexNILSP+lgy\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: '5tqWIehpSekThkJLpi0KPvGiK/bm7oXMVNLN0KdLAf/MKUzB9w==\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing whitespace
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: ''
Aug 30 12:55:04 localhost sshd[44752]: debug2: key_type_from_name: unknown key type '----'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing keytype
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: check options: '---- END SSH2 PUBLIC KEY ----\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug2: key_type_from_name: unknown key type 'END'
Aug 30 12:55:04 localhost sshd[44752]: debug3: key_read: missing keytype
Aug 30 12:55:04 localhost sshd[44752]: debug2: user_key_allowed: advance: 'END SSH2 PUBLIC KEY ----\r\n'
Aug 30 12:55:04 localhost sshd[44752]: debug2: key not found
Aug 30 12:55:04 localhost sshd[44752]: debug1: restore_uid: 0/0
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_answer_keyallowed: key 0x7f0b70e1ca10 is not allowed
Aug 30 12:55:04 localhost sshd[44752]: Failed publickey for root from 91.15.164.238 port 58557 ssh2: RSA 4c:13:08:b4:06:eb:ea:98:54:69:50:3e:cf:22:9e:da
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 23
Aug 30 12:55:04 localhost sshd[44752]: debug2: userauth_pubkey: authenticated 0 pkalg ssh-rsa [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: userauth_finish: failure partial=0 next methods="publickey,gssapi-keyex,gssapi-with-mic,password" [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: userauth-request for user root service ssh-connection method gssapi-with-mic [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug1: attempt 2 failures 1 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug2: input_userauth_request: try method gssapi-with-mic [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 42 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive_expect entering: type 43 [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering [preauth]
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_receive entering
Aug 30 12:55:04 localhost sshd[44752]: debug3: monitor_read: checking request 42
Aug 30 12:55:04 localhost sshd[44752]: debug1: Unspecified GSS failure. Minor code may provide more information\nKey table file '/etc/krb5.keytab' not found\n
Aug 30 12:55:04 localhost sshd[44752]: debug3: mm_request_send entering: type 43
Aug 30 12:55:04 localhost sshd[44752]: debug3: userauth_finish: failure partial=0 next methods="publickey,gssapi-keyex,gssapi-with-mic,password" [preauth]
Here is the reason why it didn't work. As numerous step-by-step tutorials suggest, one should generate the public key file, copy it to the server and then append the public key to the authorized_keys file with the cat command like this:
cat id_rsa.mypublickey.pub >> ~/.ssh/authorized_keysIm my case I used PuTTYgen to generate the keys. But the resulting public key file (the one thats saved when you use the save button) was not syntactically applicable for appending to authorized_keys.
To get a correct formatted public key string, copy&paste the generated snippet from the PuTTYgen window to one new line in the ~/.ssh/authorized_keys file. A correct formatted line looks like this, however, the syntax allows comments and more, too:
To get the private key in a format that you can use with other ssh-agents than Putty, you can use PuTTYgen's Conversion option and save the key in OpenSSH format.
As user ilansch suggested, more comprehensive information is found here: How to convert SSH keypairs generated using PuttyGen(Windows) into key-pairs used by ssh-agent and KeyChain(Linux)