#!/bin/bash

####################################################################################################
#### author: SlickStack ############################################################################
#### link: https://slickstack.io ###################################################################
#### mirror: https://mirrors.slickstack.io/bash/ss-install-ubuntu-ssh.txt ##########################
#### path: /var/www/ss-install-ubuntu-ssh ##########################################################
#### destination: n/a (not a boilerplate) ##########################################################
#### purpose: Reinstalls the Ubuntu (OS) SSH daemon for SlickStack servers (idempotent) ############
#### module version: Ubuntu 22.04 LTS ##############################################################
#### sourced by: ss-install ########################################################################
#### bash aliases: ss install ubuntu ssh, ss install ssh ###########################################
####################################################################################################

## SS-CONFIG MUST BE PROPERLY CONFIGURED AND ON CURRENT BUILD BEFORE RUNNING SS-INSTALL ##
## ENSURE YOUR SS-CONFIG BUILD REMAINS CURRENT BY RUNNING SS-UPDATE OCCASIONALLY ##

## source ss-config ##
source /var/www/ss-config

## source ss-functions ##
source /var/www/ss-functions

## BELOW THIS RELIES ON SS-CONFIG AND SS-FUNCTIONS

####################################################################################################
#### TABLE OF CONTENTS (SS-Install-Ubuntu-SSH) #####################################################
####################################################################################################

## this is a brief summary of the different code snippets you will find in this script ##
## each section should be commented so you understand what is being accomplished ##

## A. Touch Timestamp File
## B. Message (Begin Script)
## C. Install SSH Daemon
## D. Generate Key Pair (If Not Exists)
## E. Reset Permissions (SSH)
## F. Restart Modules (SSH)

####################################################################################################
#### A. SS-Install-Ubuntu-SSH: Touch Timestamp File ################################################
####################################################################################################

## this is a dummy timestamp file that will remember the last time this script was run ##
## it can be useful for developer reference and is sometimes used by SlickStack ##

## script timestamp ##
ss_touch "${TIMESTAMP_SS_INSTALL_UBUNTU_SSH}"

####################################################################################################
#### B. SS-Install-Ubuntu-SSH: Message (Begin Script) ##############################################
####################################################################################################

## this is a simple message that announces to the shell the purpose of this bash script ##
## it will only be noticed by sudo users who manually call ss core bash scripts ##

## echo message ##
ss_echo "${COLOR_INFO}ss-install-ubuntu-ssh: Reinstalls the Linux OS SSH daemon for sudo access... ${COLOR_RESET}"

####################################################################################################
#### C. SS-Install-Ubuntu-SSH: Install SSH Daemon ##################################################
####################################################################################################

## here we use an optimized boilerplate to reinstall the SSH/SFTP daemon to your server ##
## keep in mind that the port number will change (and root disabled) after this ##

## download latest versions ##

    ## ubuntu 22.04 ##
    if [[ "${UBUNTU_VERSION}" == "22.04" ]]; then 
        ss_wget_slowest "${TMP_SSHD_CONFIG}" "${MIRROR_SSHD_CONFIG_2204}"
    fi
    
    ## ubuntu 20.04 ##
    if [[ "${UBUNTU_VERSION}" == "20.04" ]]; then 
        ss_wget_slowest "${TMP_SSHD_CONFIG}" "${MIRROR_SSHD_CONFIG_2004}"
    fi
    
    ## ubuntu 18.04 ##
    if [[ "${UBUNTU_VERSION}" == "18.04" ]]; then
        ss_wget_slowest "${TMP_SSHD_CONFIG}" "${MIRROR_SSHD_CONFIG_1804}"
    fi

## replace variables ##
ss_sed "s/@SUDO_USER/${SUDO_USER}/g" "$TMP_SSHD_CONFIG"
ss_sed "s/@SFTP_USER/${SFTP_USER}/g" "$TMP_SSHD_CONFIG"

## set SSH port number (optional) ##
ss_sed "s/@SSH_PORT/22/g" "$TMP_SSHD_CONFIG"

ss_sed "s|@PATH_SSH_AUTHORIZED_KEYS_FILE|${PATH_SSH_AUTHORIZED_KEYS_FILE}|g" "$TMP_SSHD_CONFIG"

## restrict sudo ip address if desired (we do not use hosts.allow file in case SFTP user wants to login from anywhere) ##
if [[ "${SSH_RESTRICT_IP}" == "true" ]]; then
    ss_sed "s|@SSH_IPV4|@${SSH_IPV4}|g" "${TMP_SSHD_CONFIG}"
else
    ss_sed "s|@SSH_IPV4||g" "${TMP_SSHD_CONFIG}"
fi

## enable/disable password authentication (depending on if SSH_KEYS is enabled) ##
if [[ "$SSH_KEYS" == "true" ]]; then 
    ss_sed "s/@SSH_PASSWORD_AUTHENTICATION/no/g" "$TMP_SSHD_CONFIG"
else 
    ss_sed "s/@SSH_PASSWORD_AUTHENTICATION/yes/g" "$TMP_SSHD_CONFIG"
fi

## enable/disable public key authentication (depending on if SSH_KEYS is enabled) ##
if [[ "$SSH_KEYS" == "true" ]]; then 
    ss_sed "s/@SSH_PUBKEY_AUTHENTICATION/yes/g" "$TMP_SSHD_CONFIG"
else 
    ss_sed "s/@SSH_PUBKEY_AUTHENTICATION/no/g" "$TMP_SSHD_CONFIG"
fi

## allow IPv6 SSH sessions (any) if no IPv4 address is detected on the server ##
# if [[ CURRENT IP ADDRESS IS IPV6 ONLY ]]; then 
#    ss_sed "s/AddressFamily inet/AddressFamily any/g" /tmp/sshd_config
# fi
## Ref: https://stackoverflow.com/questions/5281341/get-local-network-interface-addresses-using-only-proc
## Ref: https://stackoverflow.com/questions/39983121/how-to-detect-if-system-has-ipv6-enabled-in-a-unix-shell-script
## Ref: https://www.cyberciti.biz/faq/bash-shell-command-to-find-get-ip-address/

## copy files to their destinations ##
ss_mv "${TMP_SSHD_CONFIG}" "${PATH_SSHD_CONFIG}"

####################################################################################################
#### D. SS-Install-Ubuntu-SSH: Generate Key Pair (If Not Exists) ###################################
####################################################################################################

## SlickStack will automatically generate a public/private SSH key pair if you want it ##
## if you already have a preferred key pair then you must manually append it ##

## generate key pair (if not exists) ##
if [[ "$SSH_KEYS" == "true" ]] && [[ ! -f "$PATH_SSH_PUBLIC_KEY_FILE" ]]; then
    ssh-keygen -f "$PATH_SSH_PRIVATE_KEY_FILE" -b 4096 -t rsa -q -N ""
fi

## append any public key found to authorized_keys list ##
if [[ "$SSH_KEYS" == "true" ]] && [[ -f "$PATH_SSH_PUBLIC_KEY_FILE" ]]; then
    cat "$PATH_SSH_PUBLIC_KEY_FILE" >> "$PATH_SSH_AUTHORIZED_KEYS_FILE"
fi

####################################################################################################
#### E. SS-Install-Ubuntu-SSH: Reset Permissions (SSH) #############################################
####################################################################################################

## run ss-perms-ubuntu-ssh ##
source "${PATH_SS_PERMS_UBUNTU_SSH}"

####################################################################################################
#### F. SS-Install-Ubuntu-SSH: Restart Modules (SSH) ###############################################
####################################################################################################

## restart ssh service ##
ss_restart ssh

####################################################################################################
#### SlickStack: External References Used To Improve This Script (Thanks, Interwebz) ###############
####################################################################################################

## Ref: https://stackoverflow.com/questions/10767488/automate-ssh-keygen-t-rsa-so-it-does-not-ask-for-a-passphrase/39939070
## Ref: https://linuxize.com/post/how-to-set-up-ssh-keys-on-ubuntu-20-04/
## Ref: https://stackoverflow.com/questions/12392598/how-to-add-rsa-key-to-authorized-keys-file
## Ref: https://askubuntu.com/questions/46424/how-do-i-add-ssh-keys-to-authorized-keys-file
## Ref: https://www.redhat.com/sysadmin/passwordless-ssh
## Ref: https://unix.stackexchange.com/questions/69314/automated-ssh-keygen-without-passphrase-how
## Ref: https://www.fastly.com/blog/key-size-for-tls
## Ref: https://www.yubico.com/blog/big-debate-2048-4096-yubicos-stand/
## Ref: https://security.stackexchange.com/questions/65174/4096-bit-rsa-encryption-keys-vs-2048
## Ref: https://superuser.com/questions/421997/what-is-a-ssh-key-fingerprint-and-how-is-it-generated
## Ref: https://en.wikipedia.org/wiki/Public_key_fingerprint
## Ref: https://docs.rackspace.com/support/how-to/log-into-a-linux-server-with-an-ssh-private-key-on-windows/
## Ref: https://support.hostway.com/hc/en-us/articles/115001509884-How-To-Use-SSH-Keys-on-Windows-Clients-with-PuTTY-
## Ref: https://devops.ionos.com/tutorials/use-ssh-keys-with-putty-on-windows/
## Ref: https://gist.github.com/jesugmz/03951b52e9777edf2d4aed62cf003273
## Ref: https://www.digitalocean.com/community/questions/how-to-switch-from-password-to-ssh-key-authentication
## Ref: https://askubuntu.com/questions/311558/ssh-permission-denied-publickey
## Ref: https://linuxize.com/post/how-to-setup-passwordless-ssh-login/
## Ref: http://manpages.ubuntu.com/manpages/bionic/man1/ssh-keygen.1.html
## Ref: https://serverfault.com/questions/854208/ssh-suddenly-returning-invalid-format/960647
## Ref: https://jonmccune.wordpress.com/2017/07/09/setting-up-ssh-keys-with-the-chrome-os-secure-shell-extension/
## Ref: https://unix.stackexchange.com/questions/406245/limit-ssh-access-to-specific-clients-by-ip-address
## Ref: https://www.linuxquestions.org/questions/linux-security-4/can-i-allow-sftp-for-any-but-ssh-for-some-ip-address-820900/

## SS_EOF