Cfrgtkky

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]

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

In my case the issues was with the incorrect shell exec.

journalctl -f

....

Feb 25 11:45:54 59a02b89e0f6 sshd: User user not allowed because shell /usr/bin/env /bin/bash does not exist

....

Changed /etc/passwd file for that user

vi /etc/passwd 

....

user:x:1000:1000::/home/user:/bin/bash

....

I had this problem on CentOS 7. I am a regular Debian-based Linux user so I was a fish out of the water. I noticed that in some of the servers it worked and in just one it didn't. The audit.log said nothing useful and the secure.log did not give anything either.
I found that the only real difference was some security context differences on files and directories between those that worked and those that didn't. Get the security with

sudo ls -laZ <user-home>/.ssh

of the directory (I'm assuming a lot of defaults on sshd_config).

You should see some ssh_home_t and user_home_t attributes. If you don't, use the chcon command to add the missing attributes.

For example

home="$(getent passwd <user> | cut -d: -f6)"

sudo chcon -R unconfined_u:object_r:ssh_home_t:s0 "$home".ssh

sudo chcon unconfined_u:object_r:user_home_t:s0 "$home"

In my case, my suspicion is that the user was created in a non standard way. His home was a directory in /var/lib.

More info in: https://www.linuxquestions.org/questions/linux-security-4/selinux-preventing-ssh-login-with-~-ssh-authorized_keys-4175469538/