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Filename : check_exim_spam.sh
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#!/bin/bash
# -----------------------------------------------------------------------------------------------
# Script name: check_exim_spam.sh
# Description: This script extracts Exim mail logs from the past hour and analyzes user activity.
#              It identifies users who have sent more than the specified threshold of emails
#              during that time period and perform action (suspend/stop/open ticket)
# Author: Tsvetan Gerov <tsvetan@worldhost.group>
# Version: 0.2
# Copyright (C) 2025 Hosting.Com
# All rights reserved.
# Dependencies: curl dig awk
# Changelog:
# Fri Jul  4 08:46:43 EEST 2025 - v0.2
# - Added --threshold argument to set the threshold for spam detection
# - Improved error handling for invalid threshold input
# - Converted to nagios check
# Thu Mar 20 10:46:09 EET 2025 - v0.1
# - Initial version / research
# ----------------------------------------------------------------------------------------------

# Global variables
HOSTNAME=$(hostname -f)
HOSTNAME_IP=$(dig +short $HOSTNAME)
EXTIP=$(curl -s ipv4.icanhazip.com)
EXTIP_PTR=$(dig +short -x $EXTIP |  sed 's/\.$//')
OSRELEASE=$(cat /etc/redhat-release  | tr -dc '0-9.'|cut -d \. -f1)

# Initialize flags and error message
CRITICAL=false
WARNING=false
ERROR_MESSAGE=""

check_deps(){
    DEPS="curl dig awk"
    for DEP in $DEPS; do
        if [ ! -f "/usr/bin/${DEP}" ]; then
            echo "[UNKNOWN] Please install $DEP"
            exit 3
        fi
    done
}


check_spam() {
    EXIM_LOG="/var/log/exim_mainlog"
    TMPFILE=$(mktemp)
    DATA=$(mktemp)
    THRESHOLD="50"

    # Parse arguments (from parent script, not from function)
    while [[ $# -gt 0 ]]; do
        case $1 in
            --threshold)
                if [[ -n $2 && $2 =~ ^[0-9]+$ ]]; then
                    THRESHOLD="$2"
                    shift
                else
                    echo "[ERROR] --threshold requires a numeric argument" >&2
                    exit 1
                fi
                ;;
            *)
                # Unknown option
                ;;
        esac
        shift
    done

    # Check if exim log exists
    if [ ! -f "$EXIM_LOG" ]; then
        WARNING=true
        ERROR_MESSAGE+="Exim log $EXIM_LOG not found, skipping spam check. "
        return
    fi

    # Declare array
    declare -A data_array

    # Get exim for the past hour
    grep "$(date --date="-1 hours" '+%Y-%m-%d %H:')" $EXIM_LOG >> $TMPFILE

    # Generate data
    grep -E '\scwd=\/home[^[:space:]]*\s' $TMPFILE | awk '{print$3}' | cut -f 2 -d = | sort | uniq -c | sort -n | sed 's/^ *//' >> $DATA
    grep -E '\sA=dovecot_(login|plain):([^\s]+)\s' $TMPFILE | grep -o 'A=[^ ]*' | cut -f 2 -d : | sort | uniq -c | sort -n | sed 's/^ *//' >> $DATA

    SMTP_LIST=$(cat $DATA)
    while IFS=' ' read -r value path; do
        data_array["$path"]="$value"
    done <<< "$SMTP_LIST"

    for path in "${!data_array[@]}"; do
        if [ "${data_array[$path]}" -gt "$THRESHOLD" ]; then
            # TODO: Action (stop/block/suspend/ticket)
            CRITICAL=true
            ERROR_MESSAGE+="$path Value: ${data_array[$path]}, "
        fi
    done
}

# Perform dep checks
check_deps

# Pass all script arguments to check_spam
check_spam "$@"


# Return final state
if [ "$CRITICAL" = true ]; then
    echo "[CRITICAL] Possible spam: ${ERROR_MESSAGE%, }"
    exit 2
elif [ "$WARNING" = true ]; then
    echo "[WARNING] ${ERROR_MESSAGE%, }"
    exit 1
else
    echo "[OK] All services are running correctly."
    exit 0
fi