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## Protocol <p align="center">
<img
src="https://user-images.githubusercontent.com/6550035/31846899-2b8a7034-b5cf-11e7-9643-afe552226c59.png"
width="100%" border="0" alt="croc">
<br>
<a href="https://github.com/schollz/croc/releases/latest"><img src="https://img.shields.io/badge/version-3.0.0-brightgreen.svg?style=flat-square" alt="Version"></a>
<a href="https://saythanks.io/to/schollz"><img src="https://img.shields.io/badge/Say%20Thanks-!-yellow.svg?style=flat-square" alt="Go Report Card"></a>
</p>
Every GET/POST request should check the IP address and make sure that there are never more than 2 IP addresses using a single channel. Once two IP addresses are in, then the channel is *full*.
<p align="center">Easily and securely transfer stuff from one computer to another.</p>
*croc* allows any two computers to directly and securely transfer files and folders. When sending a file, *croc* generates a random code phrase which must be shared with the recipient so they can receive the file. The code phrase encrypts all data and metadata and also serves to authorize the connection between the two computers in a intermediary relay. The relay connects the TCP ports between the two computers and does not store any information (and all information passing through it is encrypted).
**New version released June 24th, 2018 - please upgrade if you are using the public relay.**
I hear you asking, *Why another open-source peer-to-peer file transfer utilities?* [There](https://github.com/cowbell/sharedrop) [are](https://github.com/webtorrent/instant.io) [great](https://github.com/kern/filepizza) [tools](https://github.com/warner/magic-wormhole) [that](https://github.com/zerotier/toss) [already](https://github.com/ipfs/go-ipfs) [do](https://github.com/zerotier/toss) [this](https://github.com/nils-werner/zget). But, after review, [I found it was useful to make another](https://schollz.github.io/sending-a-file/). Namely, *croc* has no dependencies (just [download a binary and run](https://github.com/schollz/croc/releases/latest)), it works on any operating system, and its blazingly fast because it does parallel transfer over multiple TCP ports.
# Example
_These two gifs should run in sync if you force-reload (Ctl+F5)_
**Sender:**
![send](https://raw.githubusercontent.com/schollz/croc/master/logo/sender2.gif)
**Receiver:**
![receive](https://raw.githubusercontent.com/schollz/croc/master/logo/receiver2.gif)
**Sender:**
```
$ croc -send some-file-or-folder
Sending 4.4 MB file named 'some-file-or-folder'
Code is: cement-galaxy-alpha
Your public key: ecad-bakery-cup-unlit-roam-fetid-arulo-updike
Recipient public key: bike-cokery-casina-donut-field-farrow-mega-shine
ok? (y/n): y
Sending (->[1]63982)..
89% |███████████████████████████████████ | [12s:1s]
File sent (2.6 MB/s)
```
**Receiver:**
```
$ croc
Enter receive code: cement-galaxy-alpha
Receiving file (4.4 MB) into: some-file-or-folder
Your public key: bike-cokery-casina-donut-field-farrow-mega-shine
Recipient public key: ecad-bakery-cup-unlit-roam-fetid-arulo-updike
ok? (y/n): y
Receiving (<-[1]63975)..
97% |██████████████████████████████████████ | [13s:0s]
Received file written to some-file-or-folder (2.6 MB/s)
```
Note, by default, you don't need any arguments for receiving! This makes it possible for you to just double click the executable to run (nice for those of us that aren't computer wizards).
## Using *croc* in pipes
You can easily use *croc* in pipes when you need to send data through stdin or get data from stdout.
**Sender:**
```
$ cat some_file_or_folder | croc
```
In this case *croc* will automatically use the stdin data and send and assign a filename like "croc-stdin-123456789".
**Receiver:**
```
$ croc --code code-phrase --yes --stdout | more
```
Here the reciever specified the code (`--code`) so it will not be prompted, and also specified `--yes` so the file will be automatically accepted. The output goes to stdout when flagged with `--stdout`.
# Install
[Download the latest release for your system](https://github.com/schollz/croc/releases/latest).
Or, you can [install Go](https://golang.org/dl/) and build from source with `go get github.com/schollz/croc`.
# How does it work?
![Protocol](https://camo.githubusercontent.com/b85a5f63469a2f986ce4d280862b46b00ff6605c/68747470733a2f2f692e696d6775722e636f6d2f73376f515756502e706e67)
*croc* is similar to [magic-wormhole](https://github.com/warner/magic-wormhole#design) in spirit. Like *magic-wormhole*, *croc* generates a code phrase for you to share with your friend which allows secure end-to-end transferring of files and folders through a intermediary relay that connects the TCP ports between the two computers. The standard relay is on a public IP address (default `ws://croc3.schollz.com`), but before transmitting the file the two instances of *croc* send out UDP broadcasts to determine if they are both on the local network, and use a local relay instead of the cloud relay in the case that they are both local.
## Run your own relay
*croc* relies on a TCP relay to staple the parallel incoming and outgoing connections. The relay temporarily stores connection information and the encrypted meta information. The default uses a public relay at, `cowyo.com`, which has a 30-day uptime of 99.989% ([click here to check the current status of the public relay](https://stats.uptimerobot.com/lOwJYIgRm)).
You can also run your own relay, it is very easy. On your server, `your-server.com`, just run
```
$ croc -relay
```
Now, when you use *croc* to send and receive you should add `-server your-server.com` to use your relay server. Make sure to open up TCP ports 27001-27009.
# Contribute
I am awed by all the [great contributions](#acknowledgements) made! If you feel like contributing, in any way, by all means you can send an Issue, a PR, ask a question, or tweet me ([@yakczar](http://ctt.ec/Rq054)).
# Protocol
1. **Sender** requests new channel and receives empty channel from **Relay**, or obtains the channel they request (or an error if it is already occupied). 1. **Sender** requests new channel and receives empty channel from **Relay**, or obtains the channel they request (or an error if it is already occupied).
2. **Sender** generates *u* using PAKE from secret *pw*.
POST /join 3. **Sender** sends *u* to **Relay** and the type of curve being used. Returns error if channel is already occupied by sender, otherwise it uses it.
{
"channel": "...", // optional
"curve": "pxxx", // optional
"role": "sender"
}
2. **Sender** generates *X* using PAKE from secret *pw*.
3. **Sender** sends *X* to **Relay** and the type of curve being used. Returns error if channel is already occupied by sender, otherwise it uses it.
POST /channel { "x": "..." }
Note: posting to channel always requires UUID and channel for validation.
4. **Sender** communicates channel + secret *pw* to **Recipient** (human interaction). 4. **Sender** communicates channel + secret *pw* to **Recipient** (human interaction).
5. **Recipient** connects to channel and receives UUID. 5. **Recipient** connects to channel and receives UUID.
6. **Recipient** requests *u* from **Relay** using the channel. Returns error if it doesn't exist yet.
5. **Recipient** requests *X* from **Relay** using the channel. Returns error if it doesn't exist yet. 7. **Recipient** generates *v*, session key *k_B*, and hashed session key *H(k_B)* using PAKE from secret *pw*.
8. **Recipient** sends *v*, *H(H(k_B))* to **Relay**.
POST /channel (returns current state) 9. **Sender** requests *v*, *H(H(k_B))* from **Relay**.
10. **Sender** uses *v* to generate its session key *k_A* and *H(k_A)*, and checks *H(H(k_A))*==*H(H(k_B))*. **Sender** aborts here if it is incorrect.
6. **Recipient** generates *Y*, session key *k_B*, and hashed session key *H(k_B)* using PAKE from secret *pw*. 11. **Sender** gives the **Relay** authentication *H(k_A)*.
12. **Recipient** requests *H(k_A)* from relay and checks against its own. If it doesn't match, then bail.
7. **Recipient** sends *Y*, *H(H(k_B))* to **Relay**. 13. **Sender** connects to **Relay** tcp ports and identifies itself using channel+UUID.
14. **Sender** encrypts data with *k*.
POST /channel { "y": "...", "hh_k": "..." } 15. **Recipient** connects to **Relay** tcp ports and identifies itself using channel+UUID.
16. **Relay** realizes it has both recipient and sender for the same channel so it staples their connections. Sets *stapled* to `true`.
8. **Sender** requests *Y*, *H(H(k_B))* from **Relay**. 17. **Sender** asks **Relay** whether connections are stapled.
18. **Sender** sends data over TCP.
POST /channel 19. **Recipient** closes relay when finished. Anyone participating in the channel can close the relay at any time. Any of the routes except the first ones will return errors if stuff doesn't exist.
8. **Sender** uses *Y* to generate its session key *k_A* and *H(k_A)*, and checks *H(H(k_A))*==*H(H(k_B))*. **Sender** aborts here if it is incorrect.
9. **Sender** gives the **Relay** authentication *H(k_A)*.
POST /channel { "h_k": "..." }
10. **Recipient** requests *H(k_A)* from relay and checks against its own. If it doesn't match, then bail.
POST /channel
11. **Sender** connects to **Relay** tcp ports and identifies itself using channel+UUID.
12. **Sender** encrypts data with *k*.
13. **Recipient** connects to **Relay** tcp ports and identifies itself using channel+UUID.
14. **Relay** realizes it has both recipient and sender for the same channel so it staples their connections. Sets *stapled* to `true`.
16. **Sender** asks **Relay** whether connections are stapled.
POST /channel
17. **Sender** sends data over TCP.
18. **Recipient** closes relay when finished. Anyone participating in the channel can close the relay at any time. Any of the routes except the first ones will return errors if stuff doesn't exist.
POST /channel { "close": true }
### Conditions of state
The websocket implementation means that each client and relay follows their specific state machine conditions.
#### Sender
# Notes
https://play.golang.org/p/1_dfm6us8Nx
https://git.tws.website/t/thesis
https://github.com/tscholl2/siec
*croc* as a library
- use functional options
- every GET/POST request should check the IP address and make sure that there are never more than 2 IP addresses using a single channel
https://medium.com/@simplyianm/why-gos-structs-are-superior-to-class-based-inheritance-b661ba897c67
croc.New()
croc.SetX().... Set parameters
croc.Send(file)
croc.Receive()
# Conditions of state
## Sender
*Initialize* *Initialize*
@ -105,7 +157,7 @@ croc.Receive()
*Is Y and Bcrypt(k_B) available?* *Is Y and Bcrypt(k_B) available?*
- Use *Y* to generate its session key *k_A*. - Use *v* to generate its session key *k_A*.
- Check that Bcrypt(k_B) comes from k_A. Abort here if it is incorrect. - Check that Bcrypt(k_B) comes from k_A. Abort here if it is incorrect.
- Encrypts data using *k_A*. - Encrypts data using *k_A*.
- Connect to TCP ports of Relay. - Connect to TCP ports of Relay.
@ -116,7 +168,7 @@ croc.Receive()
- Send data over TCP - Send data over TCP
## Recipient #### Recipient
*Initialize* *Initialize*
@ -124,7 +176,7 @@ croc.Receive()
*Is X available?* *Is X available?*
- Generate *Y*, session key *k_B*, and hashed session key *H(k_B)* using PAKE from secret *pw*. - Generate *v*, session key *k_B*, and hashed session key *H(k_B)* using PAKE from secret *pw*.
- Send the Relay *Bcrypt(k_B)* - Send the Relay *Bcrypt(k_B)*
*Is Bcrypt(k_A) available?* *Is Bcrypt(k_A) available?*
@ -134,9 +186,24 @@ croc.Receive()
- Once file is received, Send close signal to Relay. - Once file is received, Send close signal to Relay.
## Relay #### Relay
*Is there a listener for sender and recipient?* *Is there a listener for sender and recipient?*
- Staple connections. - Staple connections.
- Send out to all parties that connections are stapled. - Send out to all parties that connections are stapled.
# License
MIT
# Acknowledgements
Thanks...
- ...[@warner](https://github.com/warner) for the [idea](https://github.com/warner/magic-wormhole).
- ...[@tscholl2](https://github.com/tscholl2) for the [encryption gists](https://gist.github.com/tscholl2/dc7dc15dc132ea70a98e8542fefffa28).
- ...[@skorokithakis](https://github.com/skorokithakis) for [code on proxying two connections](https://www.stavros.io/posts/proxying-two-connections-go/).
- ...for making pull requests [@Girbons](https://github.com/Girbons), [@techtide](https://github.com/techtide), [@heymatthew](https://github.com/heymatthew), [@Lunsford94](https://github.com/Lunsford94), [@lummie](https://github.com/lummie), [@jesuiscamille](https://github.com/jesuiscamille), [@threefjord](https://github.com/threefjord), [@marcossegovia](https://github.com/marcossegovia), [@csleong98](https://github.com/csleong98), [@afotescu](https://github.com/afotescu), [@callmefever](https://github.com/callmefever), [@El-JojA](https://github.com/El-JojA), [@anatolyyyyyy](https://github.com/anatolyyyyyy), [@goggle](https://github.com/goggle), [@smileboywtu](https://github.com/smileboywtu)!