Settings for a user behind a corporate MITM-style proxy on a Debian-based system

setup_proxy_script.sh

#! /bin/bash
#
# setup_proxy_script.sh
# Copyright (C) 2019 Ender Veiga Bueno <enderveigabueno@pm.me>
#
# Distributed under terms of the MIT license.
#

# Check that the script is being run as root (sudo ./setup_proxy_script.sh)
if [ "$EUID" -ne 0 ]
  then echo "Please run as root"
  exit
fi

#### SCRIPT VARIABLES ####
# Get the current user's home folder
user_home=$(getent passwd "$SUDO_USER" | cut -d: -f6)
# Check if .zshrc exists; if not, use default .bashrc
if [ -f "$USER_HOME/.zshrc" ]; then
  script_conf_file="$user_home/.zshrc
else
  script_conf_file="$user_home/.bashrc"
fi
# Apt's configuration file
apt_conf_file="/etc/apt/apt.conf"
# The proxy URL
proxy="INSERT PROXY URL HERE" # TODO
#### SCRIPT VARIABLES ####

# Copy all certificates to the folder where update-ca-certificates searches
for filename in certs/*; do
  if [ ! -f  "/usr/local/share/ca-certificates/{$filename##*/}" ]; then
    cp "$filename" "/usr/local/share/ca-certificates/${filename##*/}"
    chmod 644 "/usr/local/share/ca-certificates/${filename##*/}"
  fi
done

# Update certificates
# Necessary for curl/wget to work properly
update-ca-certificates

# Proxy settings for apt-get
echo "Acquire::http::proxy \"$proxy\";" >> "$apt_conf_file"

if [ "$HTTP_PROXY" == "" ]; then
  # Proxy settings system-wide
  {
    echo "export http_proxy=\"$proxy\""
    echo "export https_proxy=\"\$http_proxy\""
    echo "export ftp_proxy=\"\$http_proxy\""
    echo "export HTTP_PROXY=\"\$http_proxy\""
    echo "export HTTPS_PROXY=\"\$https_proxy\""
    echo "export FTP_PROXY=\"\$ftp_proxy\""
  } >> "$script_conf_file"
fi

source "$user_home/.bashrc"

This script should be run besides a "certs" folder, containing the proxy certificates.
Also, the "PROXY" variable should be set to the proxy URL.

It needs root permissions to setup certificates and Apt's proxy settings.

Certificates and apt should work system-wide after this script runs, but the proxy environment variables will only be set for the current user.