Summary:

I want to SFTP a file from one server to another, authorizing with a private-key.

I believe the public key is installed correctly (WinSCP lets me log in with private key), and I deliberately did not create a passphrase when generating the key-pair…. but when I try to SFTP on the command line, I'm prompted for both the non-existent passphrase and the user password.

How can I SFTP with just the unwrapped private-key?

Details:

I have two servers:

• toServer123

• fromServer123

I want to SFTP a file from one server to another, using a private-key login.

1. I generate a public-private key pair using puttyGen:

   • after providing the prompted random movement, I save the public and private key
   • I leave the passphrase field blank and choose 'yes' when prompted about unencrypted private key

2. I install the public key on toServer123:

   • I create a user paultest with password 'password123'
   • I test that I can ssh into toServer123 as user paultest
   • I create /home/paultest/.ssh/authorized_keys and add the public key

   • The public key looks like:

     cat /home/paultest/.ssh/authorized_keys #=>

     ssh-rsa verylongstringoflettersandnumbersNoNewlines paultest@toServer123

   • I chmod permissions: authorized_keys (644), .ssh (700)

3. I install the private key on the fromServer123:

   • I create dir: /home/support_user/sftp_proc (chmod 700)

   • I upload my_private_key.ppk (chmod 600) to /sftp_proc

   • I create file text.txt in /sftp_proc which just contains "this is a test"

4. as support_user, I try to SFTP to toServer123 from fromServer123:

   sftp -oIdentityFile=./my_private_key.ppk paultest@toServer123
   

What I expect:

I get logged into the server without further prompt, since I'm logging in with an unwrapped key file.

What I get:

Connecting to toServer123...

Unauthorized access to or use of this system is prohibited.
All access and use may be monitored and recorded.

Enter passphrase for key './my_private_key.ppk':

I just hit enter, and get:

paultest@toServer123's password:

Debugging steps:

• If I provide the paultest password, the SFTP works – but I don't want to use a password, I want to log in with a private key

• If I try to log in using winSCP and provide the private key, I am able to log in with just that – I get no passphrase or password prompts.

Question:

What am I doing wrong, if my goal is to log in without providing a password, and without being prompted for the non-existing passphrase?

Edit

my_private_key.ppk looks like:

PuTTY-User-Key-File-2: ssh-rsa
Encryption: none
Comment: rsa-key-20190528
Public-Lines: 6
LOTSOFLETTERSabcSYMBOLS//++ANDNUMBERS123==
Private-Lines: 14
EVENEVENMORELOTSOFLETTERSabcSYMBOLS//++ANDNUMBERS123==
Private-MAC: cf6c5c786f51a623b28eabe226c98dd6faa09787