Key created with WSL Linux 'Invalid Format'

[Greenwolf]

"OpenSSH for Windows" version

PS C:\Windows\system32> ssh -V
OpenSSH_for_Windows_8.0p1, LibreSSL 2.6.5

Server OperatingSystem
Linux myhost.mydomain.com 4.19.0-kali4-amd64 #1 SMP Debian 4.19.28-2kali1 (2019-03-18) x86_64 GNU/Linux

Client OperatingSystem
Microsoft Windows [Version 10.0.18362.418]

What is failing
After creating a SSH key on WSL Kali Linux, I move the keys to C:\Users\me.ssh

PS C:\Users\me\.ssh> dir


    Directory: C:\Users\me\.ssh


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----       21/10/2019     21:33           2654 id_rsa
-a----       21/10/2019     19:54            578 id_rsa.pub
-a----       21/10/2019     20:34            551 known_hosts

When connecting to the server, it never prompts me for my passphrase, and the output seems to show that the id_rsa key is in an invalid format.

It should be noted i have tried this with id_rsa and id_rsa.pub both converted to Linux EoL mode and Windows EoL mode with Notepad++, as suggested in this issue (#1315). However both have the same output.

Expected output

The expected output should prompt the user for the passphrase, this line:

Enter passphrase for key '/home/me/.ssh/id_rsa':

Full output:

me:~$ ssh root@myhost.mydomain.com -v
OpenSSH_8.0p1 Debian-7, OpenSSL 1.1.1c  28 May 2019
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to myhost.mydomain.com [2402:6540:110::1006] port 22.
debug1: Connection established.
debug1: identity file /home/me/.ssh/id_rsa type 0
debug1: identity file /home/me/.ssh/id_rsa-cert type -1
debug1: identity file /home/me/.ssh/id_dsa type -1
debug1: identity file /home/me/.ssh/id_dsa-cert type -1
debug1: identity file /home/me/.ssh/id_ecdsa type -1
debug1: identity file /home/me/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/me/.ssh/id_ed25519 type -1
debug1: identity file /home/me/.ssh/id_ed25519-cert type -1
debug1: identity file /home/me/.ssh/id_xmss type -1
debug1: identity file /home/me/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.0p1 Debian-7
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.9p1 Debian-10
debug1: match: OpenSSH_7.9p1 Debian-10 pat OpenSSH* compat 0x04000000
debug1: Authenticating to myhost.mydomain.com:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
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: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:jxxxYGexxx0GYxhBEUQ4vExxxP+WlhrxxxgdkHhtLk
debug1: Host 'myhost.mydomain.com' is known and matches the ECDSA host key.
debug1: Found key in /home/me/.ssh/known_hosts:1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /home/me/.ssh/id_rsa RSA SHA256:gUpmLxxx/q7dvl/C8mExxx0jCGz6xxxwUpxxxiTPk
debug1: Will attempt key: /home/me/.ssh/id_dsa
debug1: Will attempt key: /home/me/.ssh/id_ecdsa
debug1: Will attempt key: /home/me/.ssh/id_ed25519
debug1: Will attempt key: /home/me/.ssh/id_xmss
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>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/me/.ssh/id_rsa RSA SHA256:gUpxxxH5J/q7xxx/C8mxxxk0jCGzxxx/xxxgxxxiTPk
debug1: Server accepts key: /home/me/.ssh/id_rsa RSA SHA256:gUpxxxH5J/q7xxx/C8mE9qk0xxxz6sX/xxxxxx0iTPk
Enter passphrase for key '/home/me/.ssh/id_rsa':
debug1: Authentication succeeded (publickey).
Authenticated to myhost.mydomain.com ([2xxx:6xxx:110::1xxx]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Remote: /root/.ssh/authorized_keys:19: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /root/.ssh/authorized_keys:19: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
setsockopt IPV6_TCLASS 16: Operation not permitted:
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Linux myhost.mydomain.com 4.19.0-kali4-amd64 #1 SMP Debian 4.19.28-2kali1 (2019-03-18) x86_64

The programs included with the Kali GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Kali GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Mon Oct 21 18:15:59 2019 from 2xxx:6xxx:exxx:70::1xxx

Actual output

Output on windows showing it failing to load the id_rsa key due to an invalid format, but one that works on linux/WSL.

Load key "C:\\Users\\me/.ssh/id_rsa": invalid format

Full Output:

PS C:\Users\me\.ssh> & 'C:\Program Files\OpenSSH-Win64\ssh.exe' root@myhost.mydomain.com -v
OpenSSH_for_Windows_8.0p1, LibreSSL 2.6.5
debug1: Connecting to myhost.mydomain.com [2402:6540:110::1006] port 22.
debug1: Connection established.
debug1: identity file C:\\Users\\me/.ssh/id_rsa type 0
debug1: identity file C:\\Users\\me/.ssh/id_rsa-cert type -1
debug1: identity file C:\\Users\\me/.ssh/id_dsa type -1
debug1: identity file C:\\Users\\me/.ssh/id_dsa-cert type -1
debug1: identity file C:\\Users\\me/.ssh/id_ecdsa type -1
debug1: identity file C:\\Users\\me/.ssh/id_ecdsa-cert type -1
debug1: identity file C:\\Users\\me/.ssh/id_ed25519 type -1
debug1: identity file C:\\Users\\me/.ssh/id_ed25519-cert type -1
debug1: identity file C:\\Users\\me/.ssh/id_xmss type -1
debug1: identity file C:\\Users\\me/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_8.0
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.9p1 Debian-10
debug1: match: OpenSSH_7.9p1 Debian-10 pat OpenSSH* compat 0x04000000
debug1: Authenticating to myhost.mydomain.com:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
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: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:jxxxGeJexxxxhBEUQ4xxxZP+WlhrxxxHhtxxx
debug1: Host 'myhost.mydomain.com' is known and matches the ECDSA host key.
debug1: Found key in C:\\Users\\me/.ssh/known_hosts:3
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug1: Will attempt key: C:\\Users\\me/.ssh/id_rsa RSA SHA256:gxxxLcH5xxxdvl/C8mxxxk0jCxxxwUpgSi0xxx
debug1: Will attempt key: C:\\Users\\me/.ssh/id_dsa
debug1: Will attempt key: C:\\Users\\me/.ssh/id_ecdsa
debug1: Will attempt key: C:\\Users\\me/.ssh/id_ed25519
debug1: Will attempt key: C:\\Users\\me/.ssh/id_xmss
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>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: C:\\Users\\me/.ssh/id_rsa RSA SHA256:gxxxLcHxxxq7dxxx8mE9qkxxx6sX/wxxxi0iTPk
debug1: Server accepts key: C:\\Users\\me/.ssh/id_rsa RSA SHA256:gUpmLcxxxq7dvl/C8xxxqk0xxxz6sX/wUxxxi0iTPk
Load key "C:\\Users\\me/.ssh/id_rsa": invalid format
debug1: Trying private key: C:\\Users\\me/.ssh/id_dsa
debug1: Trying private key: C:\\Users\\me/.ssh/id_ecdsa
debug1: Trying private key: C:\\Users\\me/.ssh/id_ed25519
debug1: Trying private key: C:\\Users\\me/.ssh/id_xmss
debug1: No more authentication methods to try.
root@myhost.mydomain.com: Permission denied (publickey).

[CMCDragonkai]

I'm getting this on my RSA key that is password protected.

I have an AES-128-CBC rsa key that is password protected. I'm beginning to think the Windows ssh including Win32-OpenSSH just doesn't support this kind of key.

[troyfontaine]

Digging into this, if you password protect a key using Libressl on Windows the delimiter for the private key is drastically different from that used to protect a key using OpenSSL on Linux.

Windows is using OpenSSH 8.0 and the one I installed via Chocolatey was built with Libressl. Attempting to read in the key to Libressl results in the error 1204969060:error:02FFF002:system library:func(4095):No such file or directory:bio/bss_file.c:255:fopen.

Installing OpenSSL via Chocolatey I get version 1.1.1d and the error 20372:error:02001003:system library:fopen:No such process:crypto\bio\bss_file.c:69:fopen

Well, this is fun, I can open the file using openssl/libressl as long as I specify the path in Windows format exclusively. So that's a dead end. It looks like it is specifically an issue with ssh/ssh-add.

Meanwhile, Ubuntu WSL is using OpenSSH 7.6p1 built with OpenSSL 1.0.2n.

EDIT: Okay, looks like it comes down to a change that occurred in OpenSSH 7.8-they changed the format of the private keys, so this is a problem from upstream?

[maertendMSFT]

Can you try this on the latest version? Please open a new issue if you see this again.

[DavidHenri008]

I am getting this issue as well with version OpenSSH_for_Windows_8.1p1, LibreSSL 3.0.2.

OpenSSH_for_Windows_8.1p1, LibreSSL 3.0.2
debug1: Reading configuration data C:\\Users\\dxh06/.ssh/config
debug1: C:\\Users\\dxh06/.ssh/config line 5: Applying options for dcaf
debug1: C:\\Users\\dxh06/.ssh/config line 11: Applying options for *
debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2
debug2: resolve_canonicalize: hostname 192.168.2.11 is address
debug2: ssh_connect_direct
debug1: Connecting to dcaf [192.168.2.11] port 8101.
debug1: Connection established.
load pubkey "C:\\Users\\dxh06/.ssh/id_rsa": invalid format
debug1: identity file C:\\Users\\dxh06/.ssh/id_rsa type -1
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_rsa-cert error:2
debug1: identity file C:\\Users\\dxh06/.ssh/id_rsa-cert type 4
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_dsa error:2
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_dsa.pub error:2
debug1: identity file C:\\Users\\dxh06/.ssh/id_dsa type -1
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_dsa-cert error:2
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_dsa-cert.pub error:2
debug1: identity file C:\\Users\\dxh06/.ssh/id_dsa-cert type -1
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_ecdsa error:2
debug3: Failed to open file:C:/Users/dxh06/.ssh/id_ecdsa.pub error:2