246 lines
9.8 KiB
Markdown
246 lines
9.8 KiB
Markdown
# proxy-packer
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| Sponsored by [ppl](https://ppl.family) |
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"The M-PROXY Protocol" for node.js
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A strategy for packing and unpacking multiplexed streams.
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<small>Where you have distinct clients on one side trying to reach distinct servers on the other.</small>
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```
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Browser <--\ /--> Device
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Browser <---- M-PROXY Service ----> Device
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Browser <--/ \--> Device
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```
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<small>Many clients may connect to a single device. A single client may connect to many devices.</small>
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It's the kind of thing you'd use to build a poor man's VPN, or port-forward router.
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The M-PROXY Protocol
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===================
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This is similar to "The PROXY Protocol" (a la HAProxy), but desgined for multiplexed tls, http, tcp, and udp
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tunneled over arbitrary streams (such as WebSockets).
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It also has a backchannel for communicating with the proxy itself.
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Each message has a header with a socket identifier (family, addr, port), and may have additional information.
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```
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<version><headerlen><family>,<address>,<port>,<datalen>,<service>,<port>,<name>
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```
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```
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<254><45>IPv4,127.0.1.1,4321,199,https,443,example.com
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```
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```
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version (8 bits) 254 is version 1
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header length (8 bits) the remaining length of the header before data begins
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These values are used to identify a specific client among many
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socket family (string) the IPv4 or IPv6 connection from a client
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socket address (string) the x.x.x.x remote address of the client
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socket port (string) the 1-65536 source port of the remote client
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data length (string) the number of bytes in the wrapped packet, in case the network re-chunks the packet
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These optional values can be very useful at the start of a new connection
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service name (string) Either a standard service name (port + protocol), such as 'https'
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as listed in /etc/services, otherwise 'tls', 'tcp', or 'udp' for generics
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Also used for messages with the proxy (i.e. authentication)
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* 'control' for authentication, etc
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* 'error' for a specific client
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* 'pause' to pause upload to a specific client (not the whole tunnel)
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* 'resume' to resume upload to a specific client (not the whole tunnel)
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service port (string) The listening port, such as 443. Useful for non-standard or dynamic services.
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host or server name (string) Useful for services that can be routed by name, such as http, https, smtp, and dns.
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```
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Tunneled TCP SNI Packet
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-----------------------
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You should see that the result is simply all of the original packet with a leading header.
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Note that `16 03 01 00` starts at the 29th byte (at index 28 or 0x1C) instead of at index 0:
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```
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0 1 2 3 4 5 6 7 8 9 A B C D D F
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0000000 fe 1a 49 50 76 34 2c 31 32 37 2e 30 2e 31 2e 31 <-- 0xfe = v1, 0x1a = 26 more bytes for header
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0000010 2c 34 34 33 2c 31 39 39 2c 66 6f 6f
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16 03 01 00 <-- first 4 bytes of tcp packet
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0000020 c2 01 00 00 be 03 03 57 e3 76 50 66 03 df 99 76
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0000030 24 c8 31 e6 e8 08 34 6b b4 7b bb 2c f3 17 aa 5c
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0000040 ec 09 da da 83 5a b2 00 00 56 00 ff c0 24 c0 23
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0000050 c0 0a c0 09 c0 08 c0 28 c0 27 c0 14 c0 13 c0 12
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0000060 c0 26 c0 25 c0 05 c0 04 c0 03 c0 2a c0 29 c0 0f
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0000070 c0 0e c0 0d 00 6b 00 67 00 39 00 33 00 16 00 3d
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0000080 00 3c 00 35 00 2f 00 0a c0 07 c0 11 c0 02 c0 0c
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0000090 00 05 00 04 00 af 00 ae 00 8d 00 8c 00 8a 00 8b
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00000a0 01 00 00 3f 00 00 00 19 00 17 00 00 14 70 6f 6b
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00000b0 65 6d 61 70 2e 68 65 6c 6c 61 62 69 74 2e 63 6f
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00000c0 6d 00 0a 00 08 00 06 00 17 00 18 00 19 00 0b 00
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00000d0 02 01 00 00 0d 00 0c 00 0a 05 01 04 01 02 01 04
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00000e0 03 02 03
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00000e3
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```
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The v1 header uses strings for address and service descriptor information,
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but future versions may be binary.
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API
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===
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```js
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var Packer = require('proxy-packer');
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```
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```js
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unpacker = Packer.create(handlers); // Create a state machine for unpacking
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handlers.oncontrol = function (tun) { } // for communicating with the proxy
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// tun.data is an array
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// '[ -1, "[Error] bad hello" ]'
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// '[ 0, "[Error] out-of-band error message" ]'
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// '[ 1, "hello", 254, [ "add_token", "delete_token" ] ]'
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// '[ 1, "add_token" ]'
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// '[ 1, "delete_token" ]'
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handlers.onmessage = function (tun) { } // a client has sent a message
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// tun = { family, address, port, data
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// , service, serviceport, name };
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handlers.onpause = function (tun) { } // proxy requests to pause upload to a client
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// tun = { family, address, port };
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handlers.onresume = function (tun) { } // proxy requests to resume upload to a client
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// tun = { family, address, port };
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handlers.onend = function (tun) { } // proxy requests to close a client's socket
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// tun = { family, address, port };
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handlers.onerror = function (err) { } // proxy is relaying a client's error
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// err = { message, family, address, port };
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```
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<!--
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TODO
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handlers.onconnect = function (tun) { } // a new client has connected
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-->
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```js
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var chunk = Packer.pack(tun, data); // Add M-PROXY header to data
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// tun = { family, address, port
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// , service, serviceport, name }
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var addr = Packer.socketToAddr(socket); // Probe raw, raw socket for address info
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var id = Packer.addrToId(address); // Turn M-PROXY address info into a deterministic id
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var id = Packer.socketToId(socket); // Turn raw, raw socket info into a deterministic id
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```
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## API Helpers
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```js
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var socket = Packer.Stream.wrapSocket(socketOrStream); // workaround for https://github.com/nodejs/node/issues/8854
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// which was just closed recently, but probably still needs
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// something more like this (below) to work as intended
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// https://github.com/findhit/proxywrap/blob/master/lib/proxywrap.js
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```
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```js
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var myTransform = Packer.Transform.create({
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address: {
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family: '...'
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, address: '...'
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, port: '...'
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}
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// hint at the service to be used
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, service: 'https'
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});
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```
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# Testing an implementation
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If you want to write a compatible packer, just make sure that for any given input
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you get the same output as the packer does.
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```bash
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node test/pack.js input.json output.bin
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hexdump output.bin
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```
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Where `input.json` looks something like this:
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`input.json`:
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```
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{ "version": 1
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, "address": {
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"family": "IPv4"
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, "address": "127.0.1.1"
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, "port": 4321
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, "service": "foo"
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, "serviceport": 443
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, "name": 'example.com'
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}
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, "filepath": "./sni.tcp.bin"
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}
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```
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Raw TCP SNI Packet
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------------------
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and `sni.tcp.bin` is any captured tcp packet, such as this one with a tls hello:
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`sni.tcp.bin`:
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```
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0 1 2 3 4 5 6 7 8 9 A B C D D F
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0000000 16 03 01 00 c2 01 00 00 be 03 03 57 e3 76 50 66
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0000010 03 df 99 76 24 c8 31 e6 e8 08 34 6b b4 7b bb 2c
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0000020 f3 17 aa 5c ec 09 da da 83 5a b2 00 00 56 00 ff
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0000030 c0 24 c0 23 c0 0a c0 09 c0 08 c0 28 c0 27 c0 14
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0000040 c0 13 c0 12 c0 26 c0 25 c0 05 c0 04 c0 03 c0 2a
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0000050 c0 29 c0 0f c0 0e c0 0d 00 6b 00 67 00 39 00 33
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0000060 00 16 00 3d 00 3c 00 35 00 2f 00 0a c0 07 c0 11
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0000070 c0 02 c0 0c 00 05 00 04 00 af 00 ae 00 8d 00 8c
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0000080 00 8a 00 8b 01 00 00 3f 00 00 00 19 00 17 00 00
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0000090 14 70 6f 6b 65 6d 61 70 2e 68 65 6c 6c 61 62 69
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00000a0 74 2e 63 6f 6d 00 0a 00 08 00 06 00 17 00 18 00
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00000b0 19 00 0b 00 02 01 00 00 0d 00 0c 00 0a 05 01 04
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00000c0 01 02 01 04 03 02 03
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00000c7
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```
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Tunneled TCP SNI Packet
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-----------------------
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You should see that the result is simply all of the original packet with a leading header.
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Note that `16 03 01 00` starts at the 29th byte (at index 28 or 0x1C) instead of at index 0:
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```
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0 1 2 3 4 5 6 7 8 9 A B C D D F
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0000000 fe 1a 49 50 76 34 2c 31 32 37 2e 30 2e 31 2e 31 <-- 0xfe = v1, 0x1a = 26 more bytes for header
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0000010 2c 34 34 33 2c 31 39 39 2c 66 6f 6f
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16 03 01 00 <-- first 4 bytes of tcp packet
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0000020 c2 01 00 00 be 03 03 57 e3 76 50 66 03 df 99 76
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0000030 24 c8 31 e6 e8 08 34 6b b4 7b bb 2c f3 17 aa 5c
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0000040 ec 09 da da 83 5a b2 00 00 56 00 ff c0 24 c0 23
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0000050 c0 0a c0 09 c0 08 c0 28 c0 27 c0 14 c0 13 c0 12
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0000060 c0 26 c0 25 c0 05 c0 04 c0 03 c0 2a c0 29 c0 0f
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0000070 c0 0e c0 0d 00 6b 00 67 00 39 00 33 00 16 00 3d
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0000080 00 3c 00 35 00 2f 00 0a c0 07 c0 11 c0 02 c0 0c
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0000090 00 05 00 04 00 af 00 ae 00 8d 00 8c 00 8a 00 8b
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00000a0 01 00 00 3f 00 00 00 19 00 17 00 00 14 70 6f 6b
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00000b0 65 6d 61 70 2e 68 65 6c 6c 61 62 69 74 2e 63 6f
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00000c0 6d 00 0a 00 08 00 06 00 17 00 18 00 19 00 0b 00
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00000d0 02 01 00 00 0d 00 0c 00 0a 05 01 04 01 02 01 04
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00000e0 03 02 03
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00000e3
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```
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