#!/usr/bin/env bash
#
# JbTecWiz Support Centre -- generated fix script
#
# Fault : sudo is broken -- "syntax error in /etc/sudoers" and no way back in
# Fix   : Repair it from the session you still have
# Source: https://jbtecwiz.com/support/lnx-sec-sudoers
#
# Run as     : An open root shell
# Expect     : 15 minutes
# Risk       : medium
# Reversible : yes
#
# WHEN THIS IS THE RIGHT FIX
#   You still have root somewhere. Do not close that session.
#
# HOW TO UNDO IT
#   visudo keeps the previous file until a valid one is saved.
#
# Walks the fix one step at a time and asks before each. Steps with no
# command are yours to do -- it prints those and waits. DRYRUN=1 prints
# without executing; UNATTENDED=1 does not ask.
#
# --------------------------------------------------------------------
# NO WARRANTY - USE AT YOUR OWN RISK
#
# This script is provided by JbTecWiz as-is and with no warranty of any
# kind, express or implied. You run it entirely at your own risk.
#
# JbTecWiz accepts no liability for any loss or damage arising from its
# use, including but not limited to data loss, downtime, or configuration
# changes that turn out to be wrong for your system.
#
# You are responsible for reading this script before running it, for
# satisfying yourself that it suits the machine in front of you, and for
# having a working backup first. Some steps cannot be undone.
# --------------------------------------------------------------------

set -uo pipefail
DRYRUN="${DRYRUN:-0}"
UNATTENDED="${UNATTENDED:-0}"
failed=0

if [ "$(id -u)" -ne 0 ]; then
  echo "  This fix is documented as needing root. Re-run with sudo." >&2
  exit 3
fi

rule() { printf "\n%s\n" "$(printf '-%.0s' $(seq 1 70))"; if [ $# -gt 0 ]; then echo "$1"; fi; }
prose() { echo "$1" | fold -s -w 74 | sed "s/^/  /"; }

# Returns 0 when the caller should run the command, 1 when it should not.
# A manual step always returns 1 -- there is nothing for the caller to run.
step() {  # step <n> <do> <why> <manual|cmd> [command lines...]
  local n="$1" dotext="$2" why="$3" mode="$4"; shift 4
  rule "  Step $n of 6"
  prose "$dotext"
  if [ -n "$why" ]; then echo; prose "$why"; fi
  if [ "$mode" = "manual" ]; then
    echo; echo "  -> Do this yourself, then press Enter to carry on."
    if [ "$UNATTENDED" = "0" ] && [ "$DRYRUN" = "0" ]; then read -r _; fi
    return 1
  fi
  echo; printf "    %s\n" "$@"; echo
  if [ "$DRYRUN" = "1" ]; then echo "  (dry run -- not executed)"; return 1; fi
  if [ "$UNATTENDED" = "0" ]; then
    read -r -p "  Run this step? [Y]es / [S]kip / [Q]uit " a
    case "$a" in
      [Qq]*) echo "  Stopped at your request."; exit 0 ;;
      [Ss]*) echo "  Skipped."; return 1 ;;
    esac
  fi
  return 0
}

rule
echo "  sudo is broken -- "syntax error in /etc/sudoers" and no way back in"
echo "  Repair it from the session you still have"
echo
echo "  Risk: medium   Reversible   15 minutes"
echo
prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.'
rule
echo
if [ "$UNATTENDED" = "0" ] && [ "$DRYRUN" = "0" ]; then
  read -r -p "  Ready? [y/N] " go
  case "$go" in [Yy]*) ;; *) echo "  Nothing was changed."; exit 0;; esac
fi

step 1 'Do not close the session. It is the only route in.' 'This is worth stating first because the instinctive response -- closing the terminal and opening a new one to test -- is what turns a five-minute fix into a trip to the console.' manual || true

if step 2 'Check what is wrong.' '' cmd 'visudo -c'; then
  visudo -c
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 2 failed. The rest of the fix may depend on it." >&2
  fi
fi

if step 3 'Fix the named file with visudo, which refuses to save a file that does not parse.' '' cmd 'visudo' 'visudo -f /etc/sudoers.d/90-custom'; then
  visudo
  visudo -f /etc/sudoers.d/90-custom
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 3 failed. The rest of the fix may depend on it." >&2
  fi
fi

if step 4 'Check the permissions, which sudo enforces strictly and which cause a refusal with no syntax error at all.' '' cmd 'ls -l /etc/sudoers /etc/sudoers.d/' 'chmod 440 /etc/sudoers' 'chmod 440 /etc/sudoers.d/*' 'chown root:root /etc/sudoers /etc/sudoers.d/*'; then
  ls -l /etc/sudoers /etc/sudoers.d/
  chmod 440 /etc/sudoers
  chmod 440 /etc/sudoers.d/*
  chown root:root /etc/sudoers /etc/sudoers.d/*
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 4 failed. The rest of the fix may depend on it." >&2
  fi
fi

step 5 'Note that files in sudoers.d with a dot or a tilde in the name are ignored entirely -- a file saved as 90-custom.bak is silently skipped, which is often the actual cause.' '' manual || true

if step 6 'Test from a second terminal before closing the first.' '' cmd 'sudo -l'; then
  sudo -l
  if [ $? -ne 0 ]; then
    failed=$((failed+1))
    echo "  Step 6 failed. The rest of the fix may depend on it." >&2
  fi
fi

rule "  Confirm it worked"
prose 'visudo -c reports the files parse, and sudo works from a fresh session.'
if [ "$DRYRUN" = "0" ]; then
  visudo -c && sudo -v && echo ok
fi

rule
if [ "$failed" -gt 0 ]; then
  echo "  Finished with $failed failed step(s)."
  echo "  Read the full write-up at https://jbtecwiz.com/support/lnx-sec-sudoers"
else
  echo "  Finished."
fi
echo
prose 'To undo: visudo keeps the previous file until a valid one is saved.'
rule