Creating an SSH Key Pair for User Authentication with Expect in Bash - bash

Question

I have tried the following steps to set ssh passwordless (SSH Key Pair Authentication)login.
Set ip and port in bash.
ip="xxxx"
port="xxxx"
Set ssh config file on client side
cat > $HOME/.ssh/config <<EOF
Host $ip
IdentityFile $HOME/.ssh/id_rsa
User root
EOF
Create a ssh key pair on client side
ssh-keygen -t rsa -f $HOME/.ssh/id_rsa -q -b 2048 -N ""
Push id_rsa into ssh server from client side.
Prepare for ssh server
ssh -p $port root#$ip "mkdir -p /root/.ssh"
Push authorized file into ssh server
scp -P $port id_rsa.pub root#$ip:/root/.ssh/authorized_keys
Set permission for authorized file
ssh -p $port root#$ip "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"
Succeeded!
Now i want to write all steps into a one-click bash script for the job.
Here is my try.
#! /bin/bash
ip="xxxx"
port="xxxx"
pass="yyyy"
cat > $HOME/.ssh/config <<EOF
Host $ip
IdentityFile $HOME/.ssh/id_rsa.bwg_root
User root
EOF
ssh-keygen -t rsa -f $HOME/.ssh/id_rsa.bwg_root -q -b 2048 -N ""
cd $HOME/.ssh
/usr/bin/expect <<EOF
spawn ssh -p $port root#$ip "mkdir -p /root/.ssh"
expect "password:"
send "$pass\r"
spawn scp -P $port id_rsa.pub root#$ip:/root/.ssh/authorized_keys
expect "password:"
send "$pass\r"
spawn ssh -p $port root#$ip "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"
expect "password:"
send "$pass\r"
EOF
It got the following output info:
spawn ssh -p xxxx root#yyyy mkdir -p /root/.ssh
root#yyyy's password: spawn scp -P xxxx id_rsa.bwg.pub root#yyyy:/root/.ssh/authorized_keys
root#yyyy's password: spawn ssh -p xxxx root#yyyy chmod 700 .ssh; chmod 640 .ssh/authorized_keys
Why and how to fix it?

Answer 1

I'd simplify it with sshpass.
#!/bin/bash
ip="x.x.x.x"
port="xx"
export SSHPASS="yyy"
cat >$HOME/.ssh/config <<EOF
Host $ip
IdentityFile $HOME/.ssh/id_rsa.bwg_root
User root
EOF
ssh-keygen -t rsa -f "$HOME/.ssh/id_rsa.bwg_root" -q -b 2048 -N ""
cd "$HOME/.ssh" || exit 1
sshpass -e ssh -oStrictHostKeyChecking=no -p "$port" "root#$ip" "mkdir -p -m 700 /root/.ssh"
sshpass -e scp -oStrictHostKeyChecking=no -P "$port" id_rsa.bwg_root.pub "root#$ip:/root/.ssh/authorized_keys"
sshpass -e ssh -oStrictHostKeyChecking=no -p "$port" "root#$ip" "chmod 640 .ssh/authorized_keys"
Btw: I replaced last id_rsa.pub with id_rsa.bwg_root.pub and added -m 700 to mkdir and removed chmod 700 .ssh.

Answer 2

Use ssh-copy-id to push the new key to the remote host. You'll need to enter the password for that login, of course, but it's the last time you'll have to use it.
#!/bin/bash
ip="x.x.x.x"
port="xx"
id_file=$HOME/.ssh/id_rsa_$ip
cat > $HOME/.ssh/config <<EOF
HOST $ip
IdentityFile $id_file
User root
EOF
ssh-keygen -t rsa -f "$HOME/.ssh/id_rsa_$ip" -q -b 2048 -N ""
ssh-copy-id -i "$id_file" -p "$port" root#"$ip"
As a general rule, always look for a non- (or less) interactive solution using existing tools before trying except.