#!/bin/bash
#
## -------------------------------=[ Info ]=--------------------------------- ##
#
# Generate letsencrypt cert on local server and scp to esxi target.
# Designed and tested on Ubuntu 16.04LTS.
# Assumes you have upnp control over local network. Tested with Ubiquiti USG.
#
# Dependencies:
# miniupnpc (sudo apt install miniupnpc)
# certbot (sudo apt install certbot)
#
## -=[ Author ]=------------------------------------------------------------- ##
#
# shr00mie
# 9.21.2018
# v0.4
#
## -=[ Use Case ]=----------------------------------------------------------- ##
#
# Allows for the generation of certificates on a separate host which can then
# be securely copied to target esxi host.
#
## -=[ Breakdown ]=---------------------------------------------------------- ##
#
# 1. Prompt for esxi target FQDN, reminder email, and esxi admin username
# 2. Check if ssh keys exist for target.
#     - If keys exist, continue.
#     - If keys don't exist:
#       - Silently generate 4096 RSA key, no passphrase, user@target as comment.
#       - Add key to ssh-agent
#       - Create target folder/file structure for scp automation
#       - Restart SSH service on target.
# 3. Enable port forwarding.
# 4. Generate 4096 bit letsencrypt cert
# 5. Backup existing cert with datetime suffix
# 6. Copy cert to target
# 7. Restart target services
# 8. Remove port forwarding
#
## -=[ To-Do ]=-------------------------------------------------------------- ##
#
# change: PermitRootLogin yes -> PermitRootLogin no
# add: ChallengeResponseAuthentication no
# add: PasswordAuthentication no
#
## -=[ Functions ]=---------------------------------------------------------- ##

# Usage: status "Status Text"
function status() {
  GREEN='\033[00;32m'
  RESTORE='\033[0m'
  echo -e "\n...${GREEN}$1${RESTORE}...\n"
}

# Usage: input "Prompt Text" "Variable Name"
function input() {
  GREEN='\033[00;32m'
  RESTORE='\033[0m'
  echo -en "\n...${GREEN}$1${RESTORE}: "
  read $2
  echo -e ""
}

function pressanykey(){
  GREEN='\033[00;32m'
  RESTORE='\033[0m'
  echo -en "\n...${GREEN}$1. Press any key to continue.${RESTORE}..."
  read -r -p "" -n 1
}

## ---------------------------=[ Script Start ]=----------------------------- ##

# Importing Variables
status "Importing Variables"

# Read ESXiHost
input "Enter the FQDN for the certificate/host in host.domain.tld format" "ESXiHost"

# Read Email
input "Enter the email for confirmation & renewal notifications" "Email"

# Read ESXiUser
input "Enter ESXi target admin username" "ESXiUser"

# Prompt user to confirm/enable SSH on ESXi target
pressanykey "Confirm/Enable SSH access on $ESXiHost."

# Check for existing ssh keys for esxi host
status "Checking for existing ssh keys for $ESXiHost"

if [[ -e ~/.ssh/$ESXiHost'_rsa' ]]
	then
    status "Keys for $ESXiHost exist. Continuing"
else
  status "Keys for $ESXiHost not found. Generating 4096 bit keys"
  # Generate 4096 bit key for user@target
	ssh-keygen -b 4096 -t rsa -f ~/.ssh/$ESXiHost'_rsa' -q -N "" -C "$ESXiUser@$HOSTNAME LetsEncrypt"
  status "Adding new key to ssh-agent"
  # Add key to agent
	eval `ssh-agent` && ssh-add ~/.ssh/$ESXiHost'_rsa'
  status "Configuring $ESXiHost for ssh access"
  # Store key as variable
  pubkey=`cat ~/.ssh/$ESXiHost'_rsa.pub'`
  # Create directory for authorized user, copy key to target, set permissions,
  # and restart ssh service on target.
  ssh $ESXiUser@$ESXiHost "mkdir -p /etc/ssh/keys-$ESXiUser &&
  echo $pubkey > /etc/ssh/keys-$ESXiUser/authorized_keys &&
  chmod 700 -R /etc/ssh/keys-$ESXiUser &&
  chmod 600 /etc/ssh/keys-$ESXiUser/authorized_keys &&
  chown -R $ESXiUser /etc/ssh/keys-$ESXiUser &&
  /etc/init.d/SSH restart"
fi

# Enable UPnP http(s) port forward for requesting device
status "Enabling http(s) port forwarding to client for letsencrypt verification"
upnpc -e "letsencrypt http" -r 80 tcp
upnpc -e "letsencrypt https" -r 443 tcp

# Acquire letsencrypt cert
status "Requesting 4096 bit certificate for $ESXiHost"
sudo certbot certonly --standalone --preferred-challenges tls-sni --agree-tos -m $Email -d $ESXiHost --rsa-key-size 4096

# Backup existing SSL components on ESXi target
status "Backing up existing certificates on $ESXiHost"
time=$(date +%Y.%m.%d_%H:%M:%S)
ssh $ESXiUser@$ESXiHost "cp /etc/vmware/ssl/castore.pem /etc/vmware/ssl/castore.pem.back.$time"
ssh $ESXiUser@$ESXiHost "cp /etc/vmware/ssl/rui.crt /etc/vmware/ssl/rui.crt.back.$time"
ssh $ESXiUser@$ESXiHost "cp /etc/vmware/ssl/rui.key /etc/vmware/ssl/rui.key.back.$time"

# Copy letsencrypt cert to ESXi target
status "Coping letsencrypt cert to $ESXiHost"
sudo scp /etc/letsencrypt/live/$ESXiHost/fullchain.pem $ESXiUser@$ESXiHost:/etc/vmware/ssl/castore.pem
sudo scp /etc/letsencrypt/live/$ESXiHost/cert.pem $ESXiUser@$ESXiHost:/etc/vmware/ssl/rui.crt
sudo scp /etc/letsencrypt/live/$ESXiHost/privkey.pem $ESXiUser@$ESXiHost:/etc/vmware/ssl/rui.key

# Restart services on ESXi target
status "Restarting services on $ESXiHost"
ssh $ESXiUser@$ESXiHost "services.sh restart"

# Disable UPnP http(s) port forward
status "Removing http(s) port forwarding"
upnpc -d 80 tcp
upnpc -d 443 tcp

# Prompt user to confirm/disable SSH on ESXi target
pressanykey "Remember to disable SSH service on $ESXiHost"