Cannot connect with public key

September 7, 2018 303 views
Development Ubuntu 16.04

I have been combing through stack exchange, ubuntu's forums, and digital ocean, but I can't seem to find out why I cannot connect to my server.

It's been almost a year since I've been on it, I never had any problems until yesterday. I tried to connect via ssh and it didn't work, so I decided to generate a new ssh key and add it in the security section.

After failing again with the newly generated key, I went to the web console and looked in authorizedkeys, only to find that it hadn't updated. I was able to copy about half my public key into the authorizedkeys file and then I had to do it by hand because the characters began changing.

This Failed once again, below is the output of ssh -vvv user@IP

OpenSSH7.6p1, LibreSSL 2.6.2
debug1: Reading configuration data /etc/ssh/ssh
config
debug1: /etc/ssh/sshconfig line 48: Applying options for *
debug1: /etc/ssh/ssh
config line 52: Applying options for *
debug2: sshconnectdirect: needpriv 0
debug1: Connecting to 45.55.137.106 port 22.
debug1: Connection established.
debug1: identity file /Users/brendan/.ssh/idrsa type 0
debug1: key
loadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/id
rsa-cert type -1
debug1: keyloadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/iddsa type -1
debug1: key
loadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/id
dsa-cert type -1
debug1: keyloadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/idecdsa type -1
debug1: key
loadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/id
ecdsa-cert type -1
debug1: keyloadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/ided25519 type -1
debug1: key
loadpublic: No such file or directory
debug1: identity file /Users/brendan/.ssh/id
ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH7.6
debug1: Remote protocol version 2.0, remote software version OpenSSH
7.2p2 Ubuntu-4ubuntu2.4
debug1: match: OpenSSH7.2p2 Ubuntu-4ubuntu2.4 pat OpenSSH* compat 0x04000000
debug3: fd 5 is O
NONBLOCK
debug1: Authenticating to 45.55.137.106:22 as 'root'
debug3: hostkeysforeach: reading file "/Users/brendan/.ssh/knownhosts"
debug3: recordhostkey: found key type ECDSA in file /Users/brendan/.ssh/knownhosts:4
debug3: loadhostkeys: loaded 1 keys from 45.55.137.106
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: SSH2MSGKEXINIT sent
debug3: receive packet: type 20
debug1: SSH2MSGKEXINIT 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
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,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: firstkexfollows 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: firstkexfollows 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 SSH2MSGKEXECDHREPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:CEfnZqyzQNOLTJXYcAeA+HnbiAeEKuVxn2iwW395O10
debug3: hostkeysforeach: reading file "/Users/brendan/.ssh/knownhosts"
debug3: recordhostkey: found key type ECDSA in file /Users/brendan/.ssh/knownhosts:4
debug3: loadhostkeys: loaded 1 keys from 45.55.137.106
debug1: Host '45.55.137.106' is known and matches the ECDSA host key.
debug1: Found key in /Users/brendan/.ssh/known
hosts:4
debug3: send packet: type 21
debug2: setnewkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2
MSGNEWKEYS sent
debug1: expecting SSH2
MSGNEWKEYS
debug3: receive packet: type 21
debug1: SSH2
MSGNEWKEYS received
debug2: set
newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /Users/brendan/.ssh/idrsa (0x7f8c226015d0)
debug2: key: /Users/brendan/.ssh/id
dsa (0x0)
debug2: key: /Users/brendan/.ssh/idecdsa (0x0)
debug2: key: /Users/brendan/.ssh/id
ed25519 (0x0)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2MSGEXTINFO received
debug1: kex
inputextinfo: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: serviceaccept: ssh-userauth
debug1: SSH2
MSGSERVICEACCEPT 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: authmethodlookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod
isenabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:ho8g2Zv19llDRt8FMoR96YyncSO521zKT7bEvaNlP4k /Users/brendan/.ssh/id
rsa
debug3: sendpubkeytest
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: Trying private key: /Users/brendan/.ssh/iddsa
debug3: no such identity: /Users/brendan/.ssh/id
dsa: No such file or directory
debug1: Trying private key: /Users/brendan/.ssh/idecdsa
debug3: no such identity: /Users/brendan/.ssh/id
ecdsa: No such file or directory
debug1: Trying private key: /Users/brendan/.ssh/ided25519
debug3: no such identity: /Users/brendan/.ssh/id
ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
root@45.55.137.106: Permission denied (publickey).

Can someone please help me parse through this error so we can at least get a little closer to a solution?

2 Answers

Hey friend!

While there are other things that can cause this, the most likely is just that your private key is not a matching pair with anything in authorized_keys for the user/server you are attempting to log in to. Given that you just created new keys and manually entered the public key from the console, I would suggest a typo is far easier to make than see afterward. I could be wrong, I'm just trying to deal in most likely given the variables.

It's interesting that characters kept changing for you. That was when you were pasting in our console? Paste is a new feature there, so I'm on the lookout for any situations to look over.

In the meantime I would perhaps enable password login to SSH via the console, restart the SSH server, then log in and paste in your public key to authorized_keys from your SSH client. If it still occurs, then we know the problem is related to keys but unlikely to be a case of mismatched pair.

Jarland

Same Error, it looks like they remove the underscores from the post by the way.

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