hoschi-it
Posts: 2
Joined: Wed Nov 18, 2015 10:10 am

RSA authenticated SSH not working

Sat Jan 14, 2017 3:53 pm

Hi all!

(Story behind it: I recently tried to install Snappy Ubuntu Core on my Pi 2 and need to SSH into it using rsa authentication to get into the system, create a user and so on.)

I have a key set up at my desktop pc under ~/.ssh/id_rsa and configured Ubuntu to add this to its trusted keys
Then from my desktop pc I tried:

Code: Select all

ssh  -2 hoschi-it@192.168.178.41
and it prompted for a password :?: .

Verbose output of the command is following:

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OpenSSH_7.2p2 Ubuntu-4ubuntu2.1, OpenSSL 1.0.2g  1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 192.168.178.41 [192.168.178.41] port 22.
debug1: Connection established.
debug1: identity file /home/janina/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/janina/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
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
debug1: Authenticating to 192.168.178.41:22 as 'hoschi-it'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
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
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:PxQH41D3g9rBw/y9DzS01fUSqMWu8cniZExcDNvNIvY
debug1: Host '192.168.178.41' is known and matches the ECDSA host key.
debug1: Found key in /home/janina/.ssh/known_hosts:2
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/janina/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Offering RSA public key: janina@JsNotebook
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/janina/.ssh/id_dsa
debug1: Trying private key: /home/janina/.ssh/id_ecdsa
debug1: Trying private key: /home/janina/.ssh/id_ed25519
debug1: Next authentication method: password
hoschi-it@192.168.178.41's password: 
This is the sshd_config of my Pi:

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# 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 prohibit-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 yes

# 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
Has anybody an idea where the problem is? Is the key authentication not working or is there something wrong with my config?

Thank you for reading this!
hoschi-it

User avatar
lmarmisa
Posts: 1268
Joined: Thu Feb 14, 2013 2:22 am
Location: Jávea, Spain

Re: RSA authenticated SSH not working

Sat Jan 14, 2017 6:02 pm

This feature works fine in Raspbian.

If the origin of the ssh session is a PC running Ubuntu, you have to store the private key in the file ~/.ssh/id_rsa of the origin account, just as you say.

If the target is a RPi, you have to append the public key to the file .ssh/authorized_keys (normally user pi; in your case the RPi user seems hoschi-it).

No other modification is needed.

https://help.ubuntu.com/community/SSH/OpenSSH/Keys

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