You can manually set up password-free SSH for the mosftpuser user.
remote server A 10.10.17.206
local server B 10.10.17.47
we need to login to remote server without inputing password.

Step 1 Generate key files.

Log in to an sftp client 10.10.17.47 as the root user and run the following commands:

#ssh-keygen -t rsa -N "" -f $HOME/.ssh/id_rsa

Step 2 Copy the public key to sftp server.

Login to remote server as mosftpuser user and create .ssh directory for public key.

#mkdir -p ~/.ssh && touch ~/.ssh/authorized_keys

#chmod 700 ~/.ssh && chmod 600 ~/.ssh/authorized_keys

Login to sftp client server as root user

#scp ~/.ssh/id_rsa.pub [email protected]:~/.ssh/authorized_keys

Or you can use others tool winscp to finishe the duplication.

Step 3 configure public key authentication on sftp server

Login to sftp server as mosftpuser then switch to root by using sudo su - root
#vim /etc/ssh/sshd_config
PermitRootLogin no
StrictModes no
PasswordAuthentication no
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile $HOME/.ssh/authorized_keys

Step 4 Test the connection.

Run the following command to verify that mutual trust has been successfully set up:
#ssh [email protected]