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Something strange with OS X SSH client while connecting to some Linux boxes. Now I'm trying to connect from my mac to remote Debian running in qemu behind the router. Unsuccessfully :( But if I'll try to connect from linux box to localhost, using the same key, it works, so I guess the problem is with os x ssh client configuration.

Configuration as follows:

OS X ssh client config:

#   $OpenBSD: ssh_config,v 1.28 2013/09/16 11:35:43 sthen Exp $

# This is the ssh client system-wide configuration file.  See
# ssh_config(5) for more information.  This file provides defaults for
# users, and the values can be changed in per-user configuration files
# or on the command line.

# Configuration data is parsed as follows:
#  1. command line options
#  2. user-specific file
#  3. system-wide file
# Any configuration value is only changed the first time it is set.
# Thus, host-specific definitions should be at the beginning of the
# configuration file, and defaults at the end.

# Site-wide defaults for some commonly used options.  For a comprehensive
# list of available options, their meanings and defaults, please see the
# ssh_config(5) man page.

# Apple:
 Host *
   SendEnv LANG LC_*
#   AskPassGUI yes


#   ForwardAgent no
#   ForwardX11 no
#   RhostsRSAAuthentication no
#   RSAAuthentication yes
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   BatchMode no
#   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
StrictHostKeyChecking no
#   IdentityFile ~/.ssh/identity
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   Port 22
#   Protocol 2,1
#   Cipher 3des
#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
#   ProxyCommand ssh -q -W %h:%p gateway.example.com
#   RekeyLimit 1G 1h

Debian ssh server config:

# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 120
PermitRootLogin without-password
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile      %h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
PasswordAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes

OS X ssh client log:

user-mac:~ user$ ssh -vvv -o PreferredAuthentications=pubkey -o PubkeyAuthentication=yes -i .ssh/id_rsa -o Port=48883 user@host
OpenSSH_6.9p1, LibreSSL 2.1.8
debug1: Reading configuration data /Users/user/.ssh/config
debug1: /Users/user/.ssh/config line 76: Applying options for host
debug1: /Users/user/.ssh/config line 100: Applying options for host
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to host [host_ip] port 48883.
debug1: Connection established.
debug1: identity file .ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file .ssh/id_rsa-cert type -1
debug1: identity file /Users/user/.ssh/anotherkey1 type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/user/.ssh/anotherkey1-cert type -1
debug1: identity file /Users/user/.ssh/anotherkey2 type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/user/.ssh/anotherkey2-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.7p1 Debian-5+deb8u3
debug1: match: OpenSSH_6.7p1 Debian-5+deb8u3 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to host:48883 as 'user'
debug3: put_host_port: [host]:48883
debug3: hostkeys_foreach: reading file "/Users/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/user/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from [host]:48883
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,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: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-ed25519,ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,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: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit: none,zlib@openssh.com
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug1: kex: server->client chacha20-poly1305@openssh.com <implicit> none
debug1: kex: client->server chacha20-poly1305@openssh.com <implicit> none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:J1eimCMdoDpHwjxxxxxxxxxxxxxm2MoZFCZM
debug3: put_host_port: [host_ip]:48883
debug3: put_host_port: [host]:48883
debug3: hostkeys_foreach: reading file "/Users/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/user/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from [host]:48883
debug3: hostkeys_foreach: reading file "/Users/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/user/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from [host_ip]:48883
debug1: Host '[host]:48883' is known and matches the ECDSA host key.
debug1: Found key in /Users/user/.ssh/known_hosts:37
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: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /Users/user/.ssh/anotherkey1 (0x7fc7b2500f00), explicit
debug2: key: /Users/user/.ssh/anotherkey2 (0x7fc7b2501040), explicit
debug2: key: /Users/user/.ssh/anotherkey3 (0x7fc7b26196c0),
debug2: key: /Users/user/.ssh/anotherkey4 (0x7fc7b2619800),
debug2: key: /Users/user/.ssh/anotherkey5 (0x7fc7b2619960),
debug2: key: /Users/user/.ssh/anotherkey6 (0x7fc7b2619ad0),
debug2: key: /Users/user/.ssh/anotherkey7 (0x7fc7b2619ef0),
debug2: key: /Users/user/.ssh/anotherkey8 (0x7fc7b261a050),
debug2: key: /Users/user/.ssh/anotherkey9 (0x7fc7b261a1b0),
debug2: key: anotherkey10 (0x7fc7b261a310),
debug2: key: .ssh/id_rsa (0x7fc7b27005c0), explicit
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred pubkey
debug1: No more authentication methods to try.
Permission denied (publickey).

Debian ssh server log:

root@host:~# /usr/sbin/sshd -ddd
debug2: load_server_config: filename /etc/ssh/sshd_config
debug2: load_server_config: done config len = 802
debug2: parse_server_config: config /etc/ssh/sshd_config len 802
debug3: /etc/ssh/sshd_config:5 setting Port 22
debug3: /etc/ssh/sshd_config:9 setting Protocol 2
debug3: /etc/ssh/sshd_config:11 setting HostKey /etc/ssh/ssh_host_rsa_key
debug3: /etc/ssh/sshd_config:12 setting HostKey /etc/ssh/ssh_host_dsa_key
debug3: /etc/ssh/sshd_config:13 setting HostKey /etc/ssh/ssh_host_ecdsa_key
debug3: /etc/ssh/sshd_config:14 setting HostKey /etc/ssh/ssh_host_ed25519_key
debug3: /etc/ssh/sshd_config:16 setting UsePrivilegeSeparation yes
debug3: /etc/ssh/sshd_config:19 setting KeyRegenerationInterval 3600
debug3: /etc/ssh/sshd_config:20 setting ServerKeyBits 1024
debug3: /etc/ssh/sshd_config:23 setting SyslogFacility AUTH
debug3: /etc/ssh/sshd_config:24 setting LogLevel INFO
debug3: /etc/ssh/sshd_config:27 setting LoginGraceTime 120
debug3: /etc/ssh/sshd_config:28 setting PermitRootLogin without-password
debug3: /etc/ssh/sshd_config:29 setting StrictModes yes
debug3: /etc/ssh/sshd_config:31 setting RSAAuthentication yes
debug3: /etc/ssh/sshd_config:32 setting PubkeyAuthentication yes
debug3: /etc/ssh/sshd_config:33 setting AuthorizedKeysFile %h/.ssh/authorized_keys
debug3: /etc/ssh/sshd_config:36 setting IgnoreRhosts yes
debug3: /etc/ssh/sshd_config:38 setting RhostsRSAAuthentication no
debug3: /etc/ssh/sshd_config:40 setting HostbasedAuthentication no
debug3: /etc/ssh/sshd_config:45 setting PermitEmptyPasswords no
debug3: /etc/ssh/sshd_config:49 setting ChallengeResponseAuthentication no
debug3: /etc/ssh/sshd_config:52 setting PasswordAuthentication no
debug3: /etc/ssh/sshd_config:64 setting X11Forwarding yes
debug3: /etc/ssh/sshd_config:65 setting X11DisplayOffset 10
debug3: /etc/ssh/sshd_config:66 setting PrintMotd no
debug3: /etc/ssh/sshd_config:67 setting PrintLastLog yes
debug3: /etc/ssh/sshd_config:68 setting TCPKeepAlive yes
debug3: /etc/ssh/sshd_config:75 setting AcceptEnv LANG LC_*
debug3: /etc/ssh/sshd_config:77 setting Subsystem sftp /usr/lib/openssh/sftp-server
debug3: /etc/ssh/sshd_config:88 setting UsePAM yes
debug1: sshd version OpenSSH_6.7, OpenSSL 1.0.1t  3 May 2016
debug1: private host key: #0 type 1 RSA
debug1: private host key: #1 type 2 DSA
debug1: private host key: #2 type 3 ECDSA
debug1: private host key: #3 type 4 ED25519
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-ddd'
debug3: oom_adjust_setup
Set /proc/self/oom_score_adj from 0 to -1000
debug2: fd 3 setting O_NONBLOCK
debug1: Bind to port 22 on 0.0.0.0.
Server listening on 0.0.0.0 port 22.
debug2: fd 4 setting O_NONBLOCK
debug3: sock_set_v6only: set socket 4 IPV6_V6ONLY
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug3: fd 5 is not O_NONBLOCK
debug1: Server will not fork when running in debugging mode.
debug3: send_rexec_state: entering fd = 8 config len 802
debug3: ssh_msg_send: type 0
debug3: send_rexec_state: done
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
Connection from client_ip port 3080 on host_internal_ip port 22
debug1: Client protocol version 2.0; client software version OpenSSH_6.9
debug1: match: OpenSSH_6.9 pat OpenSSH* compat 0x04000000
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.7p1 Debian-5+deb8u3
debug2: fd 3 setting O_NONBLOCK
debug2: Network child is on pid 5999
debug3: preauth child monitor started
debug3: privsep user:group 107:65534 [preauth]
debug1: permanently_set_uid: 107/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1 [preauth]
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com [preauth]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com [preauth]
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 [preauth]
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 [preauth]
debug2: kex_parse_kexinit: none,zlib@openssh.com [preauth]
debug2: kex_parse_kexinit: none,zlib@openssh.com [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,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]
debug2: kex_parse_kexinit: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-ed25519,ssh-rsa,ssh-dss [preauth]
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se [preauth]
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se [preauth]
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 [preauth]
debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 [preauth]
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib [preauth]
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug1: kex: client->server chacha20-poly1305@openssh.com <implicit> none [preauth]
debug1: kex: server->client chacha20-poly1305@openssh.com <implicit> none [preauth]
debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
debug3: mm_key_sign entering [preauth]
debug3: mm_request_send entering: type 6 [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 6
debug3: mm_answer_sign
debug3: mm_answer_sign: signature 0x7f20d48e0250(100)
debug3: mm_request_send entering: type 7
debug2: monitor_read: 6 used once, disabling now
debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth]
debug3: mm_request_receive_expect entering: type 7 [preauth]
debug3: mm_request_receive entering [preauth]
debug2: kex_derive_keys [preauth]
debug2: set_newkeys: mode 1 [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug2: set_newkeys: mode 0 [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user constructed service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug3: mm_getpwnamallow entering [preauth]
debug3: mm_request_send entering: type 8 [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 8
debug3: mm_answer_pwnamallow
debug3: Trying to reverse map address client_ip.
reverse mapping checking getaddrinfo for client_dns_name [client_ip] failed - POSSIBLE BREAK-IN ATTEMPT!
debug2: parse_server_config: config reprocess config len 802
debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1
debug3: mm_request_send entering: type 9
debug2: monitor_read: 8 used once, disabling now
debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth]
debug3: mm_request_receive_expect entering: type 9 [preauth]
debug3: mm_request_receive entering [preauth]
debug2: input_userauth_request: setting up authctxt for user [preauth]
debug3: mm_start_pam entering [preauth]
debug3: mm_request_send entering: type 100 [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 100
debug1: PAM: initializing for "user"
debug1: PAM: setting PAM_RHOST to "client_ip"
debug1: PAM: setting PAM_TTY to "ssh"
debug2: monitor_read: 100 used once, disabling now
debug3: mm_inform_authserv entering [preauth]
debug3: mm_request_send entering: type 4 [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 4
debug3: mm_answer_authserv: service=ssh-connection, style=, role=
debug2: monitor_read: 4 used once, disabling now
debug2: input_userauth_request: try method none [preauth]
debug3: userauth_finish: failure partial=0 next methods="publickey" [preauth]
Connection closed by client_ip [preauth]
debug1: do_cleanup [preauth]
debug3: PAM: sshpam_thread_cleanup entering [preauth]
debug1: monitor_read_log: child log fd closed
debug3: mm_request_receive entering
debug1: do_cleanup
debug1: PAM: cleanup
debug3: PAM: sshpam_thread_cleanup entering
debug1: Killing privsep child 5999

OS X client permissions

user-mac:~ user$ ls -la .ssh/
total 144
drwx------  19 user  staff    646 Sep 23 19:10 .
drwxr-xr-x+ 43 user  staff   1462 Sep 22 16:54 ..
-rw-------   1 user  staff   1679 Sep 23 19:10 id_rsa
-rw-r--r--   1 user  staff    409 Sep 23 19:10 id_rsa.pub
-rw-r--r--   1 user  staff  12009 Sep 23 19:36 known_hosts

Debian ssh daemon permissions

root@host:~# ls -la ~user/.ssh/
total 16
drwx------ 2 user user 4096 Sep 23 20:04 .
drwxr-xr-x 4 user user 4096 Sep 21 17:34 ..
-rw------- 1 user user 1844 Sep 23 19:11 authorized_keys

Authentication logs: With debug:

root@host:~# tailf /var/log/auth.log 
Sep 23 21:15:26 host sshd[3054]: debug1: private host key: #0 type 1 RSA
Sep 23 21:15:26 host sshd[3054]: debug1: private host key: #1 type 2 DSA
Sep 23 21:15:26 host sshd[3054]: debug1: private host key: #2 type 3 ECDSA
Sep 23 21:15:26 host sshd[3054]: debug1: private host key: #3 type 4 ED25519

In normal mode:

root@host:~# tailf /var/log/auth.log 
Sep 23 21:15:43 host sshd[3104]: Server listening on 0.0.0.0 port 22.
Sep 23 21:15:43 host sshd[3104]: Server listening on :: port 22.
Sep 23 21:15:51 host sshd[3113]: Connection closed by client_ip [preauth]

Any help is highly appreciated!

  • What about the logs? – Ryan Babchishin Sep 23 '16 at 19:07
  • Added logs, nothing special there.... – Roman Sep 23 '16 at 19:20
  • That's lame. On Ubuntu server side I get several lines per connection. One being the reason for failure: Sep 23 15:18:41 igor sshd[30903]: Failed password for root from 195.154.60.194 port 58088 ssh2 – Ryan Babchishin Sep 23 '16 at 19:24
  • Make sure your .ssh directory is chmod 700. – Ryan Babchishin Sep 23 '16 at 19:26
  • it is chmod 700, as you could see in my post – Roman Sep 23 '16 at 19:57

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