#!/bin/bash

# Copyright 2014,2015,2016,2017,2018,2019,2020,2021 Security Onion Solutions, LLC
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
{%- set ISAIRGAP = salt['pillar.get']('global:airgap', 'False') %}

echo "Starting to check for yara rule updates at $(date)..."

output_dir="/opt/so/saltstack/default/salt/strelka/rules"
mkdir -p $output_dir

repos="$output_dir/repos.txt"
ignorefile="$output_dir/ignore.txt"

deletecounter=0
newcounter=0
updatecounter=0

{% if ISAIRGAP is sameas true %}

echo "Airgap mode enabled."

clone_dir="/nsm/repo/rules/strelka"
repo_name="signature-base"
mkdir -p /opt/so/saltstack/default/salt/strelka/rules/signature-base

[ -f $clone_dir/LICENSE ] && cp $clone_dir/$repo_name/LICENSE $output_dir/$repo_name

# Copy over rules
for i in $(find $clone_dir/yara -name "*.yar*"); do
  rule_name=$(echo $i | awk -F '/' '{print $NF}')
  repo_sum=$(sha256sum $i | awk '{print $1}')

  # Check rules against those in ignore list -- don't copy if ignored.
  if ! grep -iq $rule_name $ignorefile; then
    existing_rules=$(find $output_dir/$repo_name/ -name $rule_name | wc -l)

    # For existing rules, check to see if they need to be updated, by comparing checksums
    if [ $existing_rules -gt 0 ];then
      local_sum=$(sha256sum $output_dir/$repo_name/$rule_name | awk '{print $1}')
      if [ "$repo_sum" != "$local_sum" ]; then
        echo "Checksums do not match!"
        echo "Updating $rule_name..."
        cp $i $output_dir/$repo_name;
        ((updatecounter++))
      fi
    else
      # If rule doesn't exist already, we'll add it
      echo "Adding new rule: $rule_name..."
      cp $i $output_dir/$repo_name
      ((newcounter++))
    fi
  fi;
done

# Check to see if we have any old rules that need to be removed
for i in $(find $output_dir/$repo_name -name "*.yar*" | awk -F '/' '{print $NF}'); do
  is_repo_rule=$(find $clone_dir -name "$i" | wc -l)
  if [ $is_repo_rule -eq 0 ]; then
    echo "Could not find $i in source $repo_name repo...removing from $output_dir/$repo_name..."
    rm $output_dir/$repo_name/$i
    ((deletecounter++))
  fi
done

echo "Done!"

if [ "$newcounter" -gt 0 ];then
  echo "$newcounter new rules added."
fi

if [ "$updatecounter" -gt 0 ];then
  echo "$updatecounter rules updated."
fi

if [ "$deletecounter" -gt 0 ];then
  echo "$deletecounter rules removed because they were deprecated or don't exist in the source repo."
fi

{% else %}

gh_status=$(curl -s -o /dev/null -w "%{http_code}" http://github.com)
clone_dir="/tmp"
if [ "$gh_status" == "200" ]  || [ "$gh_status" == "301" ]; then

  while IFS= read -r repo; do
    if ! $(echo "$repo" | grep -qE '^#'); then
      # Remove old repo if existing bc of previous error condition or unexpected disruption
      repo_name=`echo $repo | awk -F '/' '{print $NF}'`
      [ -d $repo_name ] && rm -rf $repo_name

      # Clone repo and make appropriate directories for rules

      git clone $repo $clone_dir/$repo_name
      echo "Analyzing rules from $clone_dir/$repo_name..."
      mkdir -p $output_dir/$repo_name
      [ -f $clone_dir/$repo_name/LICENSE ] && cp $clone_dir/$repo_name/LICENSE $output_dir/$repo_name

      # Copy over rules
      for i in $(find $clone_dir/$repo_name -name "*.yar*"); do
        rule_name=$(echo $i | awk -F '/' '{print $NF}')
        repo_sum=$(sha256sum $i | awk '{print $1}')

        # Check rules against those in ignore list -- don't copy if ignored.
        if ! grep -iq $rule_name $ignorefile; then
          existing_rules=$(find $output_dir/$repo_name/ -name $rule_name | wc -l)

          # For existing rules, check to see if they need to be updated, by comparing checksums
          if [ $existing_rules -gt 0 ];then
            local_sum=$(sha256sum $output_dir/$repo_name/$rule_name | awk '{print $1}')
            if [ "$repo_sum" != "$local_sum" ]; then
              echo "Checksums do not match!"
              echo "Updating $rule_name..."
              cp $i $output_dir/$repo_name;
              ((updatecounter++))
            fi
          else
            # If rule doesn't exist already, we'll add it
            echo "Adding new rule: $rule_name..."
            cp $i $output_dir/$repo_name
            ((newcounter++))
          fi
        fi;
        done

        # Check to see if we have any old rules that need to be removed
        for i in $(find $output_dir/$repo_name -name "*.yar*" | awk -F '/' '{print $NF}'); do
          is_repo_rule=$(find $clone_dir/$repo_name -name "$i" | wc -l)
          if [ $is_repo_rule -eq 0 ]; then
            echo "Could not find $i in source $repo_name repo...removing from $output_dir/$repo_name..."
            rm $output_dir/$repo_name/$i
            ((deletecounter++))
          fi
      done
      rm -rf $clone_dir/$repo_name
  fi
  done < $repos

  echo "Done!"

  if [ "$newcounter" -gt 0 ];then
    echo "$newcounter new rules added."
  fi

  if [ "$updatecounter" -gt 0 ];then
    echo "$updatecounter rules updated."
  fi

  if [ "$deletecounter" -gt 0 ];then
    echo "$deletecounter rules removed because they were deprecated or don't exist in the source repo."
  fi

else
  echo "Server returned $gh_status status code."
  echo "No connectivity to Github...exiting..."
  exit 1
fi
{% endif %}

echo "Finished rule updates at $(date)..."
