How to use scp in a bash script without specifying password?

Question

I am a bash newbie, and am writing a bash script that will allow transfer of files between two computers. BTW, is there a more secure alternative to scp?

Currently, I am doing this manually, by using scp. The remote server always prompts me for the password, and I supply that. I want to automate this (hence the bash script). However, I dont want to supply my password in plain text (or if at all - I was under the impression that open SSL does away with passwords and uses certificates etc?).

Can anyone please explain how I can automate my current process, without explicitly displaying my password.

I am running on Ubuntu 10.0.4

Answer 1

To login without password you need to setup key-based authentication. There are a number of tutorials out there - this one looks like a good place to start (edit: the original site fell of the Internet, this link is to the last copy archived by the WayBackMachine).

If you put a passphrase on your key (recommended) you will still need to provide that when you login but you can use ssh-agent to reduce the amount of times you have to provide it.

If you need scripts that use SSH/SCP to run unattended then you need to not have a passphrase on your key, but in this case you absolutely must keep that key file secure such that no-one else can read it otherwise they will be able to authenticate on that server as you without any password/passphrase.

Answer 2

supply a password to scp

Piping your password to the standard input of scp won't work:

echo "password" | scp file user@host:/dir/to/copy/to

because scp doesn't read from the standard input for security reasons.

Use the tool sshpass instead:

You may have to install sshpass as root since it is non standard.

sshpass -p 'mypassword' scp -r [email protected]:/home/a/moo.txt /home/b/bar.txt

Answer 3

If you use a key like .pem etc (so you wouldn't have to have a password) you could use this

here's bash code for SCP with a .pem key file. Just save it to a script.sh file then run with 'sh script.sh'

Enjoy

#!/bin/bash
#Error function
function die(){
echo "$1"
exit 1
}

Host=ec2-53-298-45-63.us-west-1.compute.amazonaws.com
User=ubuntu
#Directory at sent destination
SendDirectory=scp
#File to send at host
FileName=filetosend.txt
#Key file
Key=MyKeyFile.pem

echo "Aperture in Process...";

scp -i $Key $FileName $User@$Host:$SendDirectory || \
die "@@@@@@@Houston we have problem"

echo "########Aperture Complete#########";