Pass a password to ssh in pure bash

Question

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  lt  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

User · Answer

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

User · Answer

Since there were no exact answers to my question  I made some investigation why my code doesn t work when there are other solutions that works  and decided to post what I found to complete the subject  As it turns out       ssh uses direct TTY access to make sure that the password is indeed   issued by an interactive keyboard user   sshpass manpage   which answers the question  why the pipes don t work in this case  The obvious solution was to create conditions so that ssh  thought  that it is run in the regular terminal and since it may be accomplished by simple posix functions  it is beyond what simple bash offers

[linux] Pass a password to ssh in pure bash

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