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dtlspipe

Generic DTLS wrapper for UDP sessions. Like stunnel, but for UDP. Suitable for wrapping Wireguard or UDP OpenVPN or any other connection-oriented UDP sessions.

"Client" receives plaintest UDP traffic and forwards it to "Server" via encrypted DTLS connection. "Server" listens UDP port and accepts encrypted DTLS sessions, forwarding messages from each session as a separate UDP connection to plaintext UDP port.

Features

Cross-platform (Windows/Mac OS/Linux/Android/*BSD)
Uses proven DTLS crypto for secure datagram tunneling
Simple configuration: just pre-shared key, listen address and forward address.

Installation

Binaries

Pre-built binaries are available here.

Build from source

Alternatively, you may install dtlspipe from source. Run the following command within the source directory:

make install

Usage

Generic case

Let's assume you have following setup: you have server with public IP address 203.0.113.11, running some UDP service on port 514. You want to access this service securely and have UDP datagrams between you and this service encrypted and authenticated.

Generate pre-shared key with command dtlspipe genpsk
Run dtlspipe-server on server machine: dtlspipe -psk xxxxxxxxxxxx server 0.0.0.0:2815 127.0.0.1:514
Run dtlspipe-client on your machine: dtlspipe -psk xxxxxxxxxxxx client 127.0.0.1:2816 203.0.113.11:2815
Use address 127.0.0.1:2816 instead of 203.0.113.11:514 for communication with the service.

Few notes:

You may use any ports instead of 2815 and 2816.
Use of localhost address 127.0.0.1 for port bind is optional too and used in example to restrict port access from localhost only. Use 0.0.0.0 to allow network access from outside.
PSK can be also specified via DTLSPIPE_PSK environment variable.

Wireguard

dtlspipe setup can be done using example for generic case, but more specifically, dtlspipe server should point to the wireguard server port and wireguard client should communicate with port of dtlspipe client.

You need to make following adjustments to wireguard client config:

Use bind address of the dtlspipe client as endpoint for client's wireguard connection.
Use smaller MTU for wireguard tunnel, add MTU = 1280 to the [Peer] section of wireguard client and server tunnel config.
Exclude dtlspipe server address from AllowedIPs in the wireguard client config. This calculator may help you. Example for server address 203.0.113.11:

AllowedIPs = 0.0.0.0/1, 128.0.0.0/2, 192.0.0.0/5, 200.0.0.0/7, 202.0.0.0/8, 203.0.0.0/18, 203.0.64.0/19, 203.0.96.0/20, 203.0.112.0/24, 203.0.113.0/29, 203.0.113.8/31, 203.0.113.10/32, 203.0.113.12/30, 203.0.113.16/28, 203.0.113.32/27, 203.0.113.64/26, 203.0.113.128/25, 203.0.114.0/23, 203.0.116.0/22, 203.0.120.0/21, 203.0.128.0/17, 203.1.0.0/16, 203.2.0.0/15, 203.4.0.0/14, 203.8.0.0/13, 203.16.0.0/12, 203.32.0.0/11, 203.64.0.0/10, 203.128.0.0/9, 204.0.0.0/6, 208.0.0.0/4, 224.0.0.0/3, ::/0

Additional notes

dtlspipe server skips HelloVerify message by default in order to workaround some DPI systems. It's associated with some DoS security risks. Please add server option -skip-hello-verify=false if such behavior is undesirable. Alternatively such risks may be mitigated with firewall, restricting sessions count on server port.

Synopsis

$ dtlspipe -h
Usage:

dtlspipe [OPTION]... server <BIND ADDRESS> <REMOTE ADDRESS>

  Run server listening on BIND ADDRESS for DTLS datagrams and forwarding decrypted UDP datagrams to REMOTE ADDRESS.

dtlspipe [OPTION]... client <BIND ADDRESS> <REMOTE ADDRESS>

  Run client listening on BIND ADDRESS for UDP datagrams and forwarding encrypted DTLS datagrams to REMOTE ADDRESS.

dtlspipe [OPTION]... hoppingclient <BIND ADDRESS> <ENDPOINT GROUP> [ENDPOINT GROUP]...

  Run client listening on BIND ADDRESS for UDP datagrams and forwarding encrypted DTLS datagrams to a random chosen endpoints.

  Endpoints are specified by a list of one or more ENDPOINT GROUP. ENDPOINT GROUP syntax is defined by following ABNF:

    ENDPOINT-GROUP = address-term *( "," address-term ) ":" Port
    address-term = Domain / IP-range / IP-prefix / IP-address
    Domain = <Defined in Section 4.1.2 of [RFC5321]>
    IP-range = ( IPv4address ".." IPv4address ) / ( IPv6address ".." IPv6address )
    IP-prefix = IP-address "/" 1*DIGIT
    IP-address = IPv6address / IPv4address
    IPv4address = <Defined in Section 4.1 of [RFC5954]>
    IPv6address = <Defined in Section 4.1 of [RFC5954]>

  Endpoint is chosen randomly as follows.
  First, random ENDPOINT GROUP is chosen with equal probability.
  Next, address is chosen from address sets specified by that group, with probability
  proportional to size of that set. Domain names and single addresses condidered 
  as sets having size 1, ranges and prefixes have size as count of addresses in it.

  Example: 'example.org:20000-50000' '192.168.0.0/16,10.0.0.0/8,172.16.0.0-172.31.255.255:50000-60000'

dtlspipe [OPTION]... genpsk

  Generate and output PSK.

dtlspipe ciphers

  Print list of supported ciphers and exit.

dtlspipe curves

  Print list of supported elliptic curves and exit.

dtlspipe version

  Print program version and exit.

Options:
  -cid
    	enable connection_id extension (default true)
  -ciphers value
    	colon-separated list of ciphers to use
  -cpuprofile string
    	write cpu profile to file
  -curves value
    	colon-separated list of curves to use
  -identity string
    	client identity sent to server
  -idle-time duration
    	max idle time for UDP session (default 30s)
  -key-length uint
    	generate key with specified length (default 16)
  -mtu int
    	MTU used for DTLS fragments (default 1400)
  -psk string
    	hex-encoded pre-shared key. Can be generated with genpsk subcommand
  -rate-limit value
    	limit for incoming connections rate. Format: <limit>/<time duration> or empty string to disable (default 20/1m0s)
  -skip-hello-verify
    	(server only) skip hello verify request. Useful to workaround DPI (default true)
  -stale-mode value
    	which stale side of connection makes whole session stale (both, either, left, right) (default either)
  -time-limit duration
    	limit for each session duration. Use single value X for fixed limit or range X-Y for randomized limit
  -timeout duration
    	network operation timeout (default 10s)