Pass a password to ssh in pure bash

linux bash pipe
Liberat0r picture Liberat0r · Jun 27, 2014 · Viewed 156.5k times · Source

I want to pass a password to ssh using a bash script (Yes, I know that there are ssh keys that I could use, but this is not what I intend).

I found some solutions that were using expect but since it is not a standard bash tool I am wondering if I can do this using pipes.

Can someone explain to me, why exactly something like this:

echo "password\n" | ssh somehost.com

or

ssh somehost.com <(echo "password\n")

doesn't work? Is there any possibility to make it work? Maybe executing ssh as a different process, obtaining its PID and then sending a string directly to it?

Answer

CS Pei picture CS Pei · Jun 27, 2014

You can not specify the password from the command line but you can do either using ssh keys or using sshpass as suggested by John C. or using a expect script.

To use sshpass, you need to install it first. Then

sshpass -f <(printf '%s\n' your_password) ssh user@hostname

instead of using sshpass -p your_password. As mentioned by Charles Duffy in the comments, it is safer to supply the password from a file or from a variable instead of from command line.

BTW, a little explanation for the <(command) syntax. The shell executes the command inside the parentheses and replaces the whole thing with a file descriptor, which is connected to the command's stdout. You can find more from this answer https://unix.stackexchange.com/questions/156084/why-does-process-substitution-result-in-a-file-called-dev-fd-63-which-is-a-pipe

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