Add script 'resolve-spf-ips.sh'.

resolve-spf-ips.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+#
+# resolve-spf-ips.sh
+# ------------------
+# Holt alle ip4:/ip6:-Einträge aus dem SPF-TXT-Record
+# einer Domain (z.B. spf.crsend.com).
+#
+# Usage:
+#   resolve-spf-ips.sh spf.crsend.com
+
+set -e
+
+DOMAIN="$1"
+
+if [[ -z "$DOMAIN" ]]; then
+    echo "Usage: $0 <domain>" >&2
+    exit 1
+fi
+
+dig +short TXT "$DOMAIN" \
+  | tr -d '"' \
+  | sed -n 's/.*v=spf1 //p' \
+  | tr ' ' '\n' \
+  | grep -E '^(ip4|ip6):' \
+  | sed -E 's/^ip[46]://' \
+  | sort -u