First commit
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171
dns-debunk.sh
Executable file
171
dns-debunk.sh
Executable file
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#!/usr/bin/env bash
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# dns_bpf_correlate.sh
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# Usage: sudo ./dns_bpf_correlate.sh
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#
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# Requires: bpftrace, tcpdump, date (GNU)
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# Purpose: correlate DNS packets (tcpdump) with the process that issued them using bpftrace syscall tracing.
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set -u
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DOMAIN=$1
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WINDOW_MS=2000 # how many ms back to search for matching bpftrace events
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BASE_TS="$(date +%Y%m%d_%H%M%S)"
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DNSLOG="${DOMAIN}_${BASE_TS}_dns.log"
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BPFLOG="bpftrace_${BASE_TS}.log"
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INCIDENT_DIR="incidents_${BASE_TS}"
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mkdir -p "$INCIDENT_DIR"
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RED="\e[31m"; GREEN="\e[32m"; YELLOW="\e[33m"; BLUE="\e[34m"; RESET="\e[0m"
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TCPDUMP_PID=""
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BPF_PID=""
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now_ms() { date +%s%3N; } # epoch milliseconds (GNU date)
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cleanup() {
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echo -e "${BLUE}[*] Stopping background processes...${RESET}"
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[[ -n "$TCPDUMP_PID" ]] && sudo kill "$TCPDUMP_PID" 2>/dev/null || true
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[[ -n "$BPF_PID" ]] && sudo kill "$BPF_PID" 2>/dev/null || true
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sleep 0.1
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echo -e "${BLUE}[*] Done.${RESET}"
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exit 0
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}
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trap cleanup SIGINT SIGTERM
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echo -e "${BLUE}[*] Domain: ${YELLOW}$DOMAIN${RESET}"
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echo -e "${BLUE}[*] DNS log: ${YELLOW}$DNSLOG${RESET}"
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echo -e "${BLUE}[*] bpftrace log: ${YELLOW}$BPFLOG${RESET}"
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echo -e "${BLUE}[*] Incidents directory: ${YELLOW}$INCIDENT_DIR${RESET}"
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echo -e "${BLUE}[*] Window for correlation: ${YELLOW}${WINDOW_MS} ms${RESET}"
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echo ""
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# Start tcpdump -> DNSLOG (writes raw tcpdump lines)
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sudo tcpdump -n -i any port 53 -s0 -ttt -l 2>/dev/null >> "$DNSLOG" &
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TCPDUMP_PID=$!
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echo -e "${GREEN}[*] tcpdump started (PID $TCPDUMP_PID)${RESET}"
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# Start bpftrace inline printing epoch seconds + ms and PID/COMM/FD
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# We print: <epoch_s>.<ms> PID=<pid> COMM=<comm> FD=<fd>
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# Use time (seconds since epoch) and nsecs to produce ms fraction.
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sudo bpftrace -e '
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tracepoint:syscalls:sys_enter_sendto
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{
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$s = time; // seconds since epoch
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$ms = (nsecs/1000000) % 1000;
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printf("%d.%03d PID=%d COMM=%s FD=%d\n", $s, $ms, pid, comm, args->fd);
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}
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' > "$BPFLOG" 2>/dev/null &
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BPF_PID=$!
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sleep 0.2
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# Quick liveness check for bpftrace log (it may stay empty until events occur, but we ensure process exists)
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if ! kill -0 "$BPF_PID" 2>/dev/null; then
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echo -e "${YELLOW}[!] bpftrace failed to start (process exited). Check bpftrace availability and permissions.${RESET}"
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echo -e "${YELLOW} Try: sudo bpftrace -e 'tracepoint:syscalls:sys_enter_sendto { printf(\"hi\\n\"); }'${RESET}"
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cleanup
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fi
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# Wait a short moment and check file is being appended to (if no events yet file may be empty - warn instead of failing)
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sleep 1
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if [[ ! -s "$BPFLOG" ]]; then
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echo -e "${YELLOW}[!] Note: bpftrace log is currently empty (no sendto events observed yet). This is normal until a process performs sendto().${RESET}"
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fi
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echo -e "${GREEN}[*] bpftrace started (PID $BPF_PID) -- logging to $BPFLOG${RESET}"
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echo ""
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# Helper: gather proc info for PID
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proc_info_for_pid() {
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local pid="$1"
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if [[ -r "/proc/$pid/cmdline" ]]; then
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local exe
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exe=$(sudo readlink -f "/proc/$pid/exe" 2>/dev/null || true)
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local cmd
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cmd=$(sudo tr '\0' ' ' < "/proc/$pid/cmdline" 2>/dev/null || true)
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echo "pid=$pid exe=${exe:-N/A} cmdline='${cmd:-N/A}'"
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else
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echo "pid=$pid (no /proc info)"
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fi
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}
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# Tail dns log and correlate with bpftrace by timestamp
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tail -Fn0 "$DNSLOG" | while IFS= read -r dnsline; do
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# case-insensitive match for domain
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if echo "$dnsline" | grep -qi -- "$DOMAIN"; then
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detect_ms=$(now_ms)
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echo -e "${RED}[!] Suspicious DNS request detected @ ${YELLOW}${detect_ms}${RESET}"
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echo -e "${YELLOW}$dnsline${RESET}"
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echo ""
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INCIDENT_TS="$(date +%Y%m%d_%H%M%S_%3N)"
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INCIDENT_FILE="${INCIDENT_DIR}/incident_${INCIDENT_TS}.txt"
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{
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echo "=== INCIDENT ${INCIDENT_TS} ==="
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echo "dns_line: $dnsline"
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echo "detected_at_ms: $detect_ms"
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} > "$INCIDENT_FILE"
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# extract src token (token after IP token)
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src_tok=$(echo "$dnsline" | awk '{for(i=1;i<=NF;i++) if($i=="IP" || $i=="IP6"){print $(i+1); exit}}' || true)
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if [[ -n "$src_tok" ]]; then
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srcPort="${src_tok##*.}"
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srcIP="${src_tok%.*}"
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echo -e "${GREEN}[+] Extracted source: IP=${YELLOW}${srcIP}${RESET} PORT=${YELLOW}${srcPort}${RESET}"
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echo "extracted_src_ip: $srcIP" >> "$INCIDENT_FILE"
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echo "extracted_src_port: $srcPort" >> "$INCIDENT_FILE"
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else
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echo -e "${YELLOW}[!] Could not extract source IP/port from tcpdump line${RESET}"
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echo "extracted_src_ip: N/A" >> "$INCIDENT_FILE"
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echo "extracted_src_port: N/A" >> "$INCIDENT_FILE"
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fi
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# Search BPFLOG for events within WINDOW_MS before detection
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# BPF lines start like: 1600000000.123 PID=123 COMM=foo FD=...
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low_ms=$((detect_ms - WINDOW_MS))
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high_ms=$((detect_ms))
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awk -v low="$low_ms" -v high="$high_ms" '
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BEGIN{FS=" "; OFS=" "}
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{
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# parse first token as seconds.ms
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if ($1 ~ /^[0-9]+\.[0-9]{3}$/) {
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split($1, a, ".")
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t_s = a[1]; t_ms = a[2]
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t = t_s * 1000 + t_ms
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if (t >= low && t <= high) print $0
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}
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}' "$BPFLOG" | tee -a "$INCIDENT_FILE" > /tmp/_bpf_matches.$$ || true
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if [[ -s /tmp/_bpf_matches.$$ ]]; then
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echo -e "${GREEN}[+] bpftrace events found within ${WINDOW_MS} ms:${RESET}"
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sed 's/^/ /' /tmp/_bpf_matches.$$
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echo "" >> "$INCIDENT_FILE"
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echo "bpftrace_matches:" >> "$INCIDENT_FILE"
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cat /tmp/_bpf_matches.$$ >> "$INCIDENT_FILE"
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# extract PIDs
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pids=$(sed -n 's/.*PID=\([0-9]\+\).*/\1/p' /tmp/_bpf_matches.$$ | sort -u)
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if [[ -n "$pids" ]]; then
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echo -e "${GREEN}[+] Candidate PIDs: ${YELLOW}$pids${RESET}"
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echo "" >> "$INCIDENT_FILE"
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echo "candidate_pids:" >> "$INCIDENT_FILE"
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for pid in $pids; do
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info=$(proc_info_for_pid "$pid")
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echo " - $info"
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echo " - $info" >> "$INCIDENT_FILE"
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done
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fi
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else
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echo -e "${YELLOW}[!] No bpftrace events found in window (this can happen if syscall happened >${WINDOW_MS}ms before tcpdump line or bpftrace didn't capture).${RESET}"
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echo "bpftrace_matches: NONE in ${WINDOW_MS}ms window" >> "$INCIDENT_FILE"
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fi
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# append an ss snapshot for context
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echo "" >> "$INCIDENT_FILE"
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echo "ss_snapshot:" >> "$INCIDENT_FILE"
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sudo ss -tulpn 2>/dev/null >> "$INCIDENT_FILE" || true
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echo -e "${GREEN}[+] Incident saved to ${YELLOW}${INCIDENT_FILE}${RESET}"
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echo -e "${BLUE}------------------------------------------------------${RESET}"
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echo ""
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rm -f /tmp/_bpf_matches.$$
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fi
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done
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