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My problem is that I need to establish passwordless SSH from a linux (RHEL 7.6) based system to a windows server(2012). I installed OpenSSH packages through the steps (https://github.com/PowerShell/Win32-OpenSSH/wiki/Install-Win32-OpenSSH). This works good for passwordless SSH from a Windows system to a linux system, but not the other way round.

I still see password prompts when I attempt to establish SSH to the windows system from the linux system. Any clues would be really appreciated, thanks! (Also I can't establish passwordless SSH to windows localhost from the same system, i am prompted for passwords everytime.)

(This works well for linux to linux passwordless SSH: https://www.tecmint.com/ssh-passwordless-login-using-ssh-keygen-in-5-easy-steps/ )

I followed the steps mentioned here for keys setup on windows server : https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_keymanagement

Result of command :   ssh -vvv Administrator@<remote_windows_machine_IP>


OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug2: resolving "<remote_windows_machine_IP>" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to <remote_windows_machine_IP> [<remote_windows_machine_IP>] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519-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_for_Windows_8.0
debug1: match: OpenSSH_for_Windows_8.0 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to <remote_windows_machine_IP>:22 as 'Administrator'
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /root/.ssh/known_hosts:4
debug3: load_hostkeys: loaded 1 keys from <remote_windows_machine_IP>
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,diffie-hellman-group1-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-dss-cert-v01@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ssh-dss
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,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-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: rsa-sha2-512,rsa-sha2-256,ssh-rsa,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
debug2: compression stoc: none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
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: kex: curve25519-sha256 need=64 dh_need=64
debug1: kex: curve25519-sha256 need=64 dh_need=64
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:sJuxCXKcyLFddWTtfwVPh3nHRl8TrqXfbeHzhMjASVc
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /root/.ssh/known_hosts:4
debug3: load_hostkeys: loaded 1 keys from <remote_windows_machine_IP>
debug1: Host '<remote_windows_machine_IP>' is known and matches the ECDSA host key.
debug1: Found key in /root/.ssh/known_hosts:4
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: /root/.ssh/id_rsa (0x561067fbcc20)
debug2: key: /root/.ssh/id_dsa ((nil))
debug2: key: /root/.ssh/id_ecdsa ((nil))
debug2: key: /root/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
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,password,keyboard-interactive
debug3: start over, passed a different list publickey,password,keyboard-interactive
debug3: preferred gssapi-keyex,gssapi-with-mic,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: /root/.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,password,keyboard-interactive
debug1: Trying private key: /root/.ssh/id_dsa
debug3: no such identity: /root/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /root/.ssh/id_ecdsa
debug3: no such identity: /root/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /root/.ssh/id_ed25519
debug3: no such identity: /root/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred:
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
Administrator@<remote_windows_machine_IP>'s password:



Relevant logs retrieved from /var/log/secure:


Aug 29 13:34:03 <linux_machine_a> sshd[15300]: pam_unix(sshd:session): session opened for user root by (uid=0)
Aug 29 13:35:15 <linux_machine_a> sshd[25116]: Received disconnect from <remote_windows_machine_IP> port 50334:11: disconnected by user
Aug 29 13:35:15 <linux_machine_a> sshd[25116]: Disconnected from <remote_windows_machine_IP> port 50334
Aug 29 13:35:15 <linux_machine_a> sshd[25116]: pam_unix(sshd:session): session closed for user root
Aug 29 13:35:32 <linux_machine_a> sshd[17289]: Accepted publickey for root from <remote_windows_machine_IP> port 50335 ssh2: RSA SHA256:mOdPOjLc0Tk8p2mF6danNTdSBI7o7ZnFQ5+IQgRCIyU
Aug 29 13:35:33 <linux_machine_a> sshd[17289]: pam_unix(sshd:session): session opened for user root by (uid=0)
Aug 29 13:35:44 <linux_machine_a> sshd[17289]: Received disconnect from <remote_windows_machine_IP> port 50335:11: disconnected by user
Aug 29 13:35:44 <linux_machine_a> sshd[17289]: Disconnected from <remote_windows_machine_IP> port 50335
Aug 29 13:35:44 <linux_machine_a> sshd[17289]: pam_unix(sshd:session): session closed for user root


Logs from ssh server on windows:
https://paste.ubuntu.com/p/9FBYcSjj92/
jainsha
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  • @MartinPrikryl Added the link to the logs (thanks for pointing out the location!) – jainsha Aug 29 '19 at 10:03
  • See [Logging into Windows 10 OpenSSH server with Administrator account and public key](https://superuser.com/q/1407020/213663). – Martin Prikryl Aug 29 '19 at 10:18
  • Windows host key stored under /root/.ssh/known_hosts is type ECDSA, but you only have type RSA id_rsa under /root/.ssh/id_rsa (0x561067fbcc20) and we can see below it that you did not generated the ECDSA type /root/.ssh/id_ecdsa ((nil)) is showing `nil` which means NULL. if you execut `ls -lah /root/.ssh/` you will see just the RSA type. Try either deleting the line 4 of `/root/.ssh/known_hosts` which is your window hostkey and it will autogenerate it again, or create a ECDSA key under `/root/.ssh/`, or configure windows to use RSA instead of ECDSA type. – Prado Aug 29 '19 at 10:57
  • @Prado `known_hosts` has nothing to do with private keys (`id_*`). It's perfectly valid to have RSA private key and use ECDSA host key. – Martin Prikryl Aug 29 '19 at 11:11
  • @jainsha Did you check the link I've posted above? Does it resolve your problem? – Martin Prikryl Aug 30 '19 at 06:31
  • @MartinPrikryl Your link helped me solve the authorization key issue. After that I followed another step mentioned by SNikalaichyk here : https://github.com/PowerShell/Win32-OpenSSH/issues/1306 These two steps solved my problem. Thanks! – jainsha Sep 05 '19 at 10:33
  • OK, so please accept that your question is duplicate. – Martin Prikryl Sep 05 '19 at 10:33
  • I've already suggested you to close it as a duplicate. I believe it is an *exact duplicate*. If you do not agree, do whatever you want. – Martin Prikryl Sep 05 '19 at 10:38
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    @MartinPrikryl ok, i'll mark it as duplicate – jainsha Sep 05 '19 at 10:47

1 Answers1

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The log says you sent the public key /root/.ssh/id_rsa, but it wasn't accepted by the windows machine. Check that this key's public key on the windows machine is correct and in the authorized_keys.

debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /root/.ssh/id_rsa
debug2: we sent a publickey packet, wait for reply
debug2: we did not send a packet, disable method
debug1: Next authentication method: keyboard-interactive

As Martin Prikryl mentioned, the solution is likely here: https://superuser.com/a/1407042/912095

nyov
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  • If you believe that the question is duplicate, please, vote to close the question as duplicate and do not post duplicate answers. – Martin Prikryl Aug 30 '19 at 08:52
  • @MartinPrikryl, I don't have the rep for that? – nyov Aug 30 '19 at 09:05
  • I pretty sure you can flag the question as duplicate with 126 reputation (I can do that on sites, where I have less than 126). And even if you could not, it's not an excuse for posting a duplicate question. – Martin Prikryl Aug 30 '19 at 09:21
  • @jainsha, I disagree. You admitted that it was exactly that, and your windows didn't accept the public key sent. How many hoops you have to go through to make windows _do that_, wasn't part of the Q (IMO). If you think different, it would be nice if you answered your own question with the relevant info, or added an answer to the duplicate, so that it may help other people with that problem. – nyov Sep 06 '19 at 10:20