Ubuntu – RSA keys not authenticating

authenticationopensshserverssh

Just trying to get a basic setup of openSSH going on an Ubuntu box to work remotely. Main issue: RSA keys fail auth. ssh DOES work using the password for auth, but I would much rather limit it to only allow ssh keys for auth.

Note that I refer to desktop and laptop. Desktop: machine acting as server. Laptop: machine acting as client.

Things that I have tried:

  • verifying permissions
  • regenerating keys
  • transferring public keys using ssh-copy-id and directly via copy and paste
  • different client machines
  • running restorecon -Rv ~/.ssh (even though most posts say this applies mainly to CentOS, may as well try everything)
  • and a whole lot of googling that has led to here

The relevant things I can think to include are the -vvv when attempting to connect on the laptop, the permissions of ~/.ssh on both machines, sshd_config on desktop, relevant entries in var/log/auth.log on the desktop. Obviously, if there is anything else that I can include that could help anyone resolve this issue, I will gladly provide relevant info.

Here is the -vvv when trying to auth:

➜  /home/troy 
≫  ssh -vvv -i .ssh/id_rsa lenny@xxx.xxx.xxx.229 -p xxx40
OpenSSH_7.4p1, OpenSSL 1.0.2k  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "xxx.xxx.xxx.229" port xxx40
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to xxx.xxx.xxx.229 [xxx.xxx.xxx.229] port xxx40.
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 /home/troy/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/troy/.ssh/id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.1 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to xxx.xxx.xxx.229:xxx40 as 'lenny'
debug3: put_host_port: [xxx.xxx.xxx.229]:xxx40
debug3: hostkeys_foreach: reading file "/home/troy/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/troy/.ssh/known_hosts:5
debug3: load_hostkeys: loaded 1 keys from [xxx.xxx.xxx.229]:xxx40
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
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,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: 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-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: 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: MACs stoc: 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: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,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@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: MACs ctos: 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: MACs stoc: 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: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
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: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:M57GEOh/5elIh2RU446bRCamJ21QosRFOYaYx8u5Za4
debug3: put_host_port: [xxx.xxx.xxx.229]:xxx40
debug3: put_host_port: [xxx.xxx.xxx.229]:xxx40
debug3: hostkeys_foreach: reading file "/home/troy/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/troy/.ssh/known_hosts:5
debug3: load_hostkeys: loaded 1 keys from [xxx.xxx.xxx.229]:xxx40
debug3: hostkeys_foreach: reading file "/home/troy/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/troy/.ssh/known_hosts:5
debug3: load_hostkeys: loaded 1 keys from [xxx.xxx.xxx.229]:xxx40
debug1: Host '[xxx.xxx.xxx.229]:xxx40' is known and matches the ECDSA host key.
debug1: Found key in /home/troy/.ssh/known_hosts:5
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: .ssh/id_rsa (0x55a0c58221f0), explicit, agent
debug2: key: /home/troy/.ssh/id_rsa (0x55a0c582fe00), agent
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
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
debug3: start over, passed a different list publickey
debug3: preferred 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 RSA public key: .ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: /home/troy/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
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).

And here is ~/.ssh on the desktop:

lenny@Timubukuntu:~/.ssh$ ls -la
total 12
drwx------.  2 lenny lenny 4096 Feb 27 21:49 .
drwxr-x---. 21 lenny lenny 4096 Feb 27 22:16 ..
-rw-------.  1 lenny lenny 1146 Feb 27 20:35 authorized_keys

And the ~/.ssh on the laptop:

➜  /home/troy/.ssh 
≫  ls -la
total 20
drwx------  2 troy users 4096 Feb 27 21:53 .
drwx------ 30 troy users 4096 Feb 27 23:03 ..
-rw-------  1 troy users 1679 Feb 27 20:32 id_rsa
-rw-r--r--  1 troy users  394 Feb 27 20:32 id_rsa.pub
-rw-r--r--  1 troy users 1416 Feb 27 15:13 known_hosts

And the sshd_config on the desktop:

lenny@Timubukuntu:/etc/ssh$ cat sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port xxx40 
# 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 prohibit-password
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile  home/lenny/.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

And here is the relevant info in /var/log/auth.log on the desktop:

Feb 27 22:52:31 Timubukuntu sshd[1901]: Connection closed by 67.20.206.135 port 36566 [preauth]

Best Answer

  • The home directory can't be writable by anyone but the user for key permissions to work. The file will be ignored otherwise

    Try chown -R troy:troy /home/troy/

    Also I think you are missing a / in this part of sshd_config

    AuthorizedKeysFile home/lenny/.ssh/authorized_keys