AbuseIPDB Integration for mailcow¶

(Community support only)

Introduction¶

AbuseIPDB is an online service dedicated to the identification and reporting of malicious IP addresses. It provides a platform where users can collect and share information about suspicious IP activities, aiding in the effective combat against cyber threats. The database is constantly updated with user submissions, allowing security professionals and network administrators to proactively safeguard their systems against potential attacks. With various API integrations and search functionalities, AbuseIPDB serves as a valuable resource for enhancing network security and preventing abuse from cybercriminal activities.

Prerequisites¶

Create a free AbuseIPDB account¶

To use the AbuseIPDB API, you must create a free account: https://www.abuseipdb.com/register

After successful registration, you can create a new API key in the login area under the "API" tab. This key is required for the script below.

Required packages¶

The packages "jq" and "ipset" have to be installed on your mailcow system

Script¶

The API key collected above is then used in the corresponding variable "ABUSEIP_API_KEY" a in the following script. (Find the latest version in the GitHub Repo: https://github.com/DocFraggle/mailcow-scripts/blob/main/abuseipdb.sh, please check the code before using it.)

#!/bin/bash

# Adjust the values of the following variables
ABUSEIP_API_KEY="XXXXXXXXXXXXXXXXXXXXXXXXXXX"
ABUSEIPDB_LIST="/tmp/abuseipdb_blacklist.txt"

show_help() {
  echo "Usage: $0 [OPTIONS]"
  echo
  echo "Options:"
  echo "  --skip-abuseipdb     Skip AbuseIPDB call, use last output file"
  echo "  --enable-log         Add an iptables LOG rule to show drops in journald/syslog"
  echo "  -h, --help           Show this help message"
}

SKIP_ABUSEIPDB=false
ENABLE_LOG=false

for arg in "$@"; do
  case $arg in
    --skip-abuseipdb)
      SKIP_ABUSEIPDB=true
      ;;
    --enable-log)
      ENABLE_LOG=true
      ;;
    -h|--help)
      show_help
      exit 0
      ;;
    *)
      echo "Unknown option: $arg"
      show_help
      exit 1
      ;;
  esac
done

# Check if ipset installed
if ! command -v ipset >/dev/null 2>&1; then
  echo "ipset binary NOT found, please install package"
  exit 1
fi

if [ "$SKIP_ABUSEIPDB" = false ]
then
  echo "Retrieve IPs from AbuseIPDB"
  curl -sG https://api.abuseipdb.com/api/v2/blacklist \
    -d confidenceMinimum=90 \
    -d plaintext \
    -H "Key: $ABUSEIP_API_KEY" \
    -H "Accept: application/json" \
    -o $ABUSEIPDB_LIST

  # Capture the exit code from curl
  exit_code=$?

  # Check if curl encountered an error
  if [ $exit_code -ne 0 ]; then
    echo "Curl encountered an error with exit code $exit_code while rertieving the AbuseIPDB IPs"
    exit 1
  fi
else
  if [ -f $ABUSEIPDB_LIST ]
  then
    echo "Skipping AbuseIPDB call"
  else
    echo "Option to skip AbuseIPDB call was chosen, but file $ABUSEIPDB_LIST does not exist"
    exit 1
  fi
fi

IPSET_V4="abuseipdb_blacklist_v4"
IPSET_V6="abuseipdb_blacklist_v6"

echo "Ensure the ipsets exist"
# Create IPv4 ipset if missing
if ! ipset list $IPSET_V4 &>/dev/null; then
  echo "Creating ipset $IPSET_V4"
  ipset create $IPSET_V4 hash:ip family inet
fi
# Create IPv6 ipset if missing
if ! ipset list $IPSET_V6 &>/dev/null; then
  echo "Creating ipset $IPSET_V6"
  ipset create $IPSET_V6 hash:ip family inet6
fi

echo "Flush existing ipset entries"
ipset flush $IPSET_V4
ipset flush $IPSET_V6

echo "Process each IP and add it to the appropriate ipset"
while IFS= read -r ip; do
  [[ -z "$ip" ]] && continue  # Skip empty lines
  if [[ "$ip" =~ : ]]
  then
    ipset add $IPSET_V6 "$ip" 2>/dev/null
  else
    ipset add $IPSET_V4 "$ip" 2>/dev/null
  fi
done < $ABUSEIPDB_LIST

echo "Ensure iptables/ip6tables rules exist at the top"

ensure_rule_at_top() {
  local chain=$1
  local rule=$2
  local cmd=$3  # iptables or ip6tables
  local log=$4

  if ! $cmd -S $chain | grep -q -- "$rule"; then
    eval "$cmd -I $chain 1 $rule"  # Add rule if missing
  else
    FIRST_RULE=$($cmd -S $chain | sed -n '2p')
    if [[ "$FIRST_RULE" != *"$rule"* ]]; then

      for line in $($cmd -nL MAILCOW --line-numbers | grep 'MAILCOW-DROP' | awk '{print $1}' | sort -rn); do
        $cmd -D MAILCOW "$line"
      done
      eval "$cmd -D $chain $rule"  # Remove old rule
      eval "$cmd -I $chain 1 $rule"  # Reinsert at the top
    fi
  fi
}

# iptables variables
CHAIN_NAME="MAILCOW" # DO NOT CHANGE THIS UNTIL YOU KNOW WHAT YOU'RE DOING! :)
LOG_PREFIX="MAILCOW-DROP: " # Change this to your liking

IPTABLES_RULE_V4="-m set --match-set $IPSET_V4 src -j DROP"
IPTABLES_RULE_V6="-m set --match-set $IPSET_V6 src -j DROP"

ensure_rule_at_top "$CHAIN_NAME" "$IPTABLES_RULE_V4" "iptables"
ensure_rule_at_top "$CHAIN_NAME" "$IPTABLES_RULE_V6" "ip6tables"

if [ "$ENABLE_LOG" = true ]
then
  IPTABLES_RULE_V4_LOG="-m set --match-set abuseipdb_blacklist_v4 src -j LOG --log-prefix '$LOG_PREFIX' --log-level 4"
  IPTABLES_RULE_V6_LOG="-m set --match-set abuseipdb_blacklist_v6 src -j LOG --log-prefix '$LOG_PREFIX' --log-level 4"

  # Remove all LOG rules
  for cmd in iptables ip6tables
  do
    for line in $($cmd -nL $CHAIN_NAME --line-numbers | grep '$LOG_PREFIX' | awk '{print $1}' | sort -rn)
    do
      $cmd -D $CHAIN_NAME "$line" >/dev/null
    done
  done

  ensure_rule_at_top "$CHAIN_NAME" "$IPTABLES_RULE_V4_LOG" "iptables"
  ensure_rule_at_top "$CHAIN_NAME" "$IPTABLES_RULE_V6_LOG" "ip6tables"
else
  # Remove all potential LOG rules as argument wasn't specified
  for cmd in iptables ip6tables
  do
    for line in $($cmd -nL $CHAIN_NAME --line-numbers | grep '$LOG_PREFIX' | awk '{print $1}' | sort -rn)
    do
      $cmd -D $CHAIN_NAME "$line" >/dev/null
    done
  done
fi

# Save ipset rules to persist across reboots
ipset save > /etc/ipset.rules

echo -e "\n\nAll done, have fun.\n\nCheck your current iplist entries with 'ipset list | less'"

You can run the script via a cron job up to 5 times a day, which is the limit set for the free AbuseIPDB account. In the following example, the cron job runs every 5 hours at 0, 5, 10, 15, and 20 o'clock.

0 */5 * * * /path/to/the/above/script

If the script is run with --skip-abuseipdb, the retrieval of IPs from AbuseIPDB is skipped. This can be useful to avoid reaching the daily limit, for example, when reinserting the iptables rule after a mailcow restart.

If the script is run with --enable-log, addtitional LOG rules are created. Logs can be found in journalctl/syslog, depending on the system.