How to avoid password prompt with rsync (and without using public keys)?

Question

I need to execute rsync, without it prompting me for password.

I've seen in rsync manpage that it doesn't allow specifying the password as command line argument.
But I noticed that it allows specifying the password via the variable RSYNC_PASSWORD.

So I've tried exporting the variable, but rsync keeps asking me for password.

export RSYNC_PASSWORD="abcdef"
rsync [email protected]:/abc /def

What am I doing wrong?

Please consider:

• I understand that this is a bad idea from security aspect
• I must use only rsync, can't use other software
• I can't use key-based authentication
• I've already read many SE question, e.g.:
  how-to-pass-password-for-rsync-ssh-command @ stackoverflow.com
  rsync-cron-job-with-a-password @ superuser.com
  how-to-setup-rsync-without-password-with-ssh-on-unix-linux @ superuser.com

In other words, I need to have the RSYNC_PASSWORD approach working! :-)

Answer 1

If the rsync daemon isn't running on the target machine, and you don't care about exposing passwords to everyone on the local machine (Why shouldn't someone use passwords in the command line?), you can use sshpass:

 sshpass -p "password" rsync [email protected]:/abc /def

Note the space at the start of the command, in the bash shell this will stop the command (and the password) from being stored in the history. I don't recommend using the RSYNC_PASSWORD variable unless absolutely necessary (as per a previous edit to this answer), I recommend suppressing history storage or at least clearing history after. In addition, you can use tput reset to clear your terminal history.

Answer 2

This password environment variable appears only to be used when using the rsync protocol:

rsync rsync://[email protected]:/abc /def

For this to work, you need to run rsync as a daemon as well (--daemon option), which is often done using inetd.conf.

When using this protocol, abc should correspond to a target defined in /etc/rsyncd.conf. The user name should be present in a auth users line for this target, and a password file should be specified with the secrets file option.

It is this secrets file that contains mappings between user names and passwords in the following format:

username:password

And it is this password that you can specify using the RSYNC_PASSWORD environment variable.

Answer 3

Very useful for scripting is to use --password-file command line option.

• Create empty file called rsync_pass
• write in password to this file (nothing more)
• chmod 600 rsync_pass
• rsync $args --password-file=rsync_pass user@rsynchost::/share localdirectory

This can be used for scripting and allows to be more secure that just exporting password to system variable.

Answer 4

You can use standard ssh identities to do passwordless login. This is handled by default if you have a ~/.ssh/id_rsa or the like, but you can also hardcode your own path to the private key of an authorized keypair.

This allows batching/scripting without exposing passwords, and the public key can be remove from the target server if the private key is ever compromised.

rsync -e"ssh -i /path/to/privateKey" -avR $sourcedir ${ruser}@${rhost}:~/${rdir}/

You can also add arguments like -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null to not force remote host key verification. !Caution - that opens up man in the middle attacks and is general bad practice!

Answer 5

This seems to be an evergreen topic. Therefore I would like to propose the solution which worked best for me on an Ubuntu 20.04 machine.

My goal was to create a backup on a 1blu cloud drive, which did not allow SSH key login.

1. First, I created the file ~/.rsync_pass and wrote the password of the SSH user into it.

2. Then I used the sshpass command with parameter -f to read the password from this file and to pass it to rsync.

sshpass -f ~/.rsync_pass rsync -av /var/www/folder/ [email protected]:/backup

Answer 6

For rsyncd protocol, use process substitution for the option --password-file=FILE

rsync --password-file=<(echo "1233456") [email protected]::abc /def

Answer 7

I wrote my script inspired by the comments in this post, so I'll post it here as another source of inspiration. My requirements were, no rsyncd on remote, password login, no exposure of password in history or command line. That's actually not very difficult:

#!/bin/bash

HOST=mymachine.mydomain.com
USER=fms
LOCAL=/home/fms/Progetti/MyProject/src

read -s -p "Password for $USER@$HOST: " SSHPASS
echo

sshpass -e rsync -i -r --checksum --delete --chown=nginx:nginx -e "ssh -o PreferredAuthentications=password" $LOCAL/lavori_senato $USER@$HOST:/var/www/drupal/test/web/modules/custom

I needed to alter the default configuration of my ssh so that it wouldn't try public-key first. The echo after read is just a touch of formatting, since using -s even the end of line is not printed, and the output of rsync overlapped with the password prompt.

Answer 8

For me, it was as simple as ensuring that keys are added to the agent after first successful connection:

In my ~/.ssh/config, I have the following entry:

Host *
    AddKeysToAgent=yes

This ensures that for all hosts, the key is added to the agent after initial connect.

With this enabled, I no longer saw discrepancies between normal ssh and when rsync does its ssh

Answer 9

The only safe and feasible solution that I found over time consists of:

1. Generate a new ssh key specifically for passwordless backups only. Do not use a passphrase with it;

2. Upload it to the server as your normal ssh user. Do not create another user for it, or upload it as www-data as www-data must not be able to login to the system;

3. Change that uploaded key in authorized_keys to run a bash script rather than provide the user with a terminal on ssh login. An example would be to replace

   ssh-rsa AAAAB3Nza......k1y0=
   

   with something like this

   command="script.sh",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty ssh-rsa AAAAB3Nza......k1y0=
   

4. In script.sh, you would have something like this:

     if [[ "$SSH_ORIGINAL_COMMAND" == "rsync --server --sender -vlDtre.iLsfxCIvu /home/server/files ." ]] 
     then
          $SSH_ORIGINAL_COMMAND
     fi
   

   where "rsync --server --sender -vlDtre.iLsfxCIvu /home/server/files ." is an ssh digest you get from your server when you try to unsuccessfully login with

   rsync -av -e "ssh -i rsync_key" user@$7.7.7.7:/home/server/files /home/user
   

   Upon this unsuccessful login, the value of the digest (i.e. its string value) will be recorded in $SSH_ORIGINAL_COMMAND;

5. Things to consider: if you are backing up any webroot files which the standard ssh user does not have access to without sudo, add that user to group www-data

6. Things to consider: www-data user will need to have maximally restrictive configuration. Ideally we would want something like this:

    www-data:x:33:33:www-data:/nonexistent:/usr/sbin/nologin
   

   which is achievable by running

     sudo usermod -d /nonexistent $wwwuser -s /usr/sbin/nologin
   

7. Now you can ssh to the server to run a passwordless rsync backup

   rsync -av -e "ssh -i rsync_key" user@$7.7.7.7:/home/server/files /home/user