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IPv6 Basic theory ​

Networks ​

IPv6 addresses are structured to enhance network organization and device interaction. An IPv6 address is divided into:

  1. Network Prefix: The initial 48 bits, determining the network segment.
  2. Subnet ID: Following 16 bits, used for defining specific subnets within the network.
  3. Interface Identifier: The concluding 64 bits, uniquely identifying a device within the subnet.

While IPv6 omits the ARP protocol found in IPv4, it introduces ICMPv6 with two primary messages:

  • Neighbor Solicitation (NS): Multicast messages for address resolution.
  • Neighbor Advertisement (NA): Unicast responses to NS or spontaneous announcements.

IPv6 also incorporates special address types:

  • Loopback Address (::1): Equivalent to IPv4's 127.0.0.1, for internal communication within the host.
  • Link-Local Addresses (FE80::/10): For local network activities, not for internet routing. Devices on the same local network can discover each other using this range.

Practical Usage of IPv6 in Network Commands ​

To interact with IPv6 networks, you can use various commands:

  • Ping Link-Local Addresses: Check the presence of local devices using ping6.
  • Neighbor Discovery: Use ip neigh to view devices discovered at the link layer.
  • alive6: An alternative tool for discovering devices on the same network.

Below are some command examples:

bash
ping6 –I eth0 -c 5 ff02::1 > /dev/null 2>&1
ip neigh | grep ^fe80

# Alternatively, use alive6 for neighbor discovery
alive6 eth0

IPv6 addresses can be derived from a device's MAC address for local communication. Here's a simplified guide on how to derive the Link-local IPv6 address from a known MAC address, and a brief overview of IPv6 address types and methods to discover IPv6 addresses within a network.

Given a MAC address 12:34:56:78:9a:bc, you can construct the Link-local IPv6 address as follows:

  1. Convert MAC to IPv6 format: 1234:5678:9abc
  2. Prepend fe80:: and insert fffe in the middle: fe80::1234:56ff:fe78:9abc
  3. Invert the seventh bit from the left, changing 1234 to 1034: fe80::1034:56ff:fe78:9abc

IPv6 Address Types ​

  • Unique Local Address (ULA): For local communications, not meant for public internet routing. Prefix: FEC00::/7
  • Multicast Address: For one-to-many communication. Delivered to all interfaces in the multicast group. Prefix: FF00::/8
  • Anycast Address: For one-to-nearest communication. Sent to the closest interface as per routing protocol. Part of the 2000::/3 global unicast range.

Address Prefixes ​

  • fe80::/10: Link-Local addresses (similar to 169.254.x.x)
  • fc00::/7: Unique Local-Unicast (similar to private IPv4 ranges like 10.x.x.x, 172.16.x.x, 192.168.x.x)
  • 2000::/3: Global Unicast
  • ff02::1: Multicast All Nodes
  • ff02::2: Multicast Router Nodes

Discovering IPv6 Addresses within a Network ​

  1. Obtain the MAC address of a device within the network.
  2. Derive the Link-local IPv6 address from the MAC address.

Way 2: Using Multicast ​

  1. Send a ping to the multicast address ff02::1 to discover IPv6 addresses on the local network.
bash
service ufw stop # Stop the firewall
ping6 -I <IFACE> ff02::1 # Send a ping to multicast address
ip -6 neigh # Display the neighbor table

IPv6 Man-in-the-Middle (MitM) Attacks ​

Several techniques exist for executing MitM attacks in IPv6 networks, such as:

  • Spoofing ICMPv6 neighbor or router advertisements.
  • Using ICMPv6 redirect or "Packet Too Big" messages to manipulate routing.
  • Attacking mobile IPv6 (usually requires IPSec to be disabled).
  • Setting up a rogue DHCPv6 server.

Identifying IPv6 Addresses in the eild ​

Exploring Subdomains ​

A method to find subdomains that are potentially linked to IPv6 addresses involves leveraging search engines. For instance, employing a query pattern like ipv6.* can be effective. Specifically, the following search command can be used in Google:

bash
site:ipv6./

Utilizing DNS Queries ​

To identify IPv6 addresses, certain DNS record types can be queried:

  • AXFR: Requests a complete zone transfer, potentially uncovering a wide range of DNS records.
  • AAAA: Directly seeks out IPv6 addresses.
  • ANY: A broad query that returns all available DNS records.

Probing with Ping6 ​

After pinpointing IPv6 addresses associated with an organization, the ping6 utility can be used for probing. This tool helps in assessing the responsiveness of identified IPv6 addresses, and might also assist in discovering adjacent IPv6 devices.

References ​

Learn AWS hacking from zero to hero with htARTE (HackTricks AWS Red Team Expert)!

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