1 files changed, 95 insertions, 0 deletions
diff --git a/cmd/anubis/internal/dnsbl/dnsbl.go b/cmd/anubis/internal/dnsbl/dnsbl.go
new file mode 100644
index 0000000..60edd5c
--- /dev/null
+++ b/cmd/anubis/internal/dnsbl/dnsbl.go
@@ -0,0 +1,95 @@
+package dnsbl
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+)
+
+//go:generate go tool golang.org/x/tools/cmd/stringer -type=DroneBLResponse
+
+type DroneBLResponse byte
+
+const (
+	AllGood               DroneBLResponse = 0
+	IRCDrone              DroneBLResponse = 3
+	Bottler               DroneBLResponse = 5
+	UnknownSpambotOrDrone DroneBLResponse = 6
+	DDOSDrone             DroneBLResponse = 7
+	SOCKSProxy            DroneBLResponse = 8
+	HTTPProxy             DroneBLResponse = 9
+	ProxyChain            DroneBLResponse = 10
+	OpenProxy             DroneBLResponse = 11
+	OpenDNSResolver       DroneBLResponse = 12
+	BruteForceAttackers   DroneBLResponse = 13
+	OpenWingateProxy      DroneBLResponse = 14
+	CompromisedRouter     DroneBLResponse = 15
+	AutoRootingWorms      DroneBLResponse = 16
+	AutoDetectedBotIP     DroneBLResponse = 17
+	Unknown               DroneBLResponse = 255
+)
+
+func Reverse(ip net.IP) string {
+	if ip.To4() != nil {
+		return reverse4(ip)
+	}
+
+	return reverse6(ip)
+}
+
+func reverse4(ip net.IP) string {
+	splitAddress := strings.Split(ip.String(), ".")
+
+	// swap first and last octet
+	splitAddress[0], splitAddress[3] = splitAddress[3], splitAddress[0]
+	// swap middle octets
+	splitAddress[1], splitAddress[2] = splitAddress[2], splitAddress[1]
+
+	return strings.Join(splitAddress, ".")
+}
+
+func reverse6(ip net.IP) string {
+	ipBytes := []byte(ip)
+	var sb strings.Builder
+
+	for i := len(ipBytes) - 1; i >= 0; i-- {
+		// Split the byte into two nibbles
+		highNibble := ipBytes[i] >> 4
+		lowNibble := ipBytes[i] & 0x0F
+
+		// Append the nibbles in reversed order
+		sb.WriteString(fmt.Sprintf("%x.%x.", lowNibble, highNibble))
+	}
+
+	return sb.String()[:len(sb.String())-1]
+}
+
+func Lookup(ipStr string) (DroneBLResponse, error) {
+	ip := net.ParseIP(ipStr)
+	if ip == nil {
+		return Unknown, errors.New("dnsbl: input is not an IP address")
+	}
+
+	revIP := Reverse(ip) + ".dnsbl.dronebl.org"
+
+	ips, err := net.LookupIP(revIP)
+	if err != nil {
+		var dnserr *net.DNSError
+		if errors.As(err, &dnserr) {
+			if dnserr.IsNotFound {
+				return AllGood, nil
+			}
+		}
+
+		return Unknown, err
+	}
+
+	if len(ips) != 0 {
+		for _, ip := range ips {
+			return DroneBLResponse(ip.To4()[3]), nil
+		}
+	}
+
+	return UnknownSpambotOrDrone, nil
+}