add PTR/rDNS match check and ASN/org lookup via WHOIS

- DNS: reverse DNS lookup on A record IPs to verify PTR configuration

- Infra: ASN and organization lookup via whois.radb.net

- Refactor checkARecords to return resolved IPs for downstream use

Signed-off-by: Blake Ridgway <blake@blakeridgway.com>

internal/infra/checker.go

@@ -1,6 +1,7 @@
 package infra
 
 import (
+	"bufio"
 	"fmt"
 	"net"
 	"strings"
@@ -72,6 +73,20 @@ func Run(domain string, resolvedIPs []string) types.InfraResult {
 	}
 	result.CDN = cdn
 
+	// ASN / org lookup via WHOIS
+	asn, org := lookupASN(targetIP)
+	if asn != "" {
+		result.ASN = asn
+		result.Org = org
+		msg := fmt.Sprintf("ASN: %s", asn)
+		if org != "" {
+			msg += fmt.Sprintf(" (%s)", org)
+		}
+		result.Checks = append(result.Checks, types.CheckResult{
+			Status: types.StatusInfo, Message: msg,
+		})
+	}
+
 	// Common ports check
 	result.Checks = append(result.Checks, checkPorts(targetIP)...)
 
@@ -107,6 +122,42 @@ func detectCDN(ip string) string {
 	return ""
 }
 
+// lookupASN queries whois.radb.net for the ASN and organization of an IP.
+func lookupASN(ip string) (asn, org string) {
+	conn, err := net.DialTimeout("tcp", "whois.radb.net:43", 5*time.Second)
+	if err != nil {
+		return "", ""
+	}
+	defer conn.Close()
+
+	// Set a deadline for the entire WHOIS exchange.
+	conn.SetDeadline(time.Now().Add(10 * time.Second))
+
+	fmt.Fprintf(conn, "%s\r\n", ip)
+
+	scanner := bufio.NewScanner(conn)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if asn == "" && strings.HasPrefix(line, "origin:") {
+			asn = strings.TrimSpace(strings.TrimPrefix(line, "origin:"))
+			asn = strings.ToUpper(asn)
+		}
+		if org == "" && strings.HasPrefix(line, "descr:") {
+			org = strings.TrimSpace(strings.TrimPrefix(line, "descr:"))
+		}
+		if asn != "" && org != "" {
+			break
+		}
+	}
+
+	// Trim long descriptions to keep output readable.
+	if len(org) > 80 {
+		org = org[:77] + "..."
+	}
+
+	return asn, org
+}
+
 func checkPorts(ip string) []types.CheckResult {
 	var checks []types.CheckResult
 	var mu sync.Mutex