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README.md

xx network Client

pipeline status coverage report

The client is a library and related command-line tool that facilitates making full-featured xx clients for all platforms. It interfaces with the cMix system, enabling access to all xx network messaging features, including end-to-end encryption and metadata protection.

This repository contains everything necessary to implement all of the xx network messaging features. It also contains features to extend the base messaging protocols.

The command-line tool accompanying the client library can be built for any platform supported by golang. The libraries are built for iOS and Android using gomobile.

For library writers, the client requires a writable folder to store data, functions for receiving and approving requests for creating secure end-to-end messaging channels, for discovering users, and for receiving different types of messages. Details for implementing these features are in the Library Overview section below.

The client is open-source software released under the simplified BSD License.

Command Line Usage

The command-line tool is intended for testing xx network functionality and not for regular user use.

These instructions assume that you have Go 1.17.X installed, and GCC installed for Cgo (such as build-essential on Debian or Ubuntu).

Compilation steps:

git clone https://gitlab.com/elixxir/client.git client
cd client
go mod vendor -v
go mod tidy
go test ./...
# Linux 64 bit binary
GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -ldflags '-w -s' -o client.linux64 main.go
# Windows 64 bit binary
GOOS=windows GOARCH=amd64 CGO_ENABLED=0 go build -ldflags '-w -s' -o client.win64 main.go
# Windows 32 big binary
GOOS=windows GOARCH=386 CGO_ENABLED=0 go build -ldflags '-w -s' -o release/client.win32 main.go
# Mac OSX 64 bit binary (intel)
GOOS=darwin GOARCH=amd64 CGO_ENABLED=0 go build -ldflags '-w -s' -o release/client.darwin64 main.go

Fetching an NDF

All actions performed with the client require a current NDF. The NDF is downloadable from the command line or via an access point in the Client API.

Use the getndf command to fetch the NDF via the command line. getndf enables command-line users to poll the NDF from a network gateway without any pre-established client connection:

// Fetch NDF (example usage for Gateways, assumes you are running a gateway locally)
$ go run main.go getndf --gwhost localhost:8440 --cert certfile.pem | jq . >ndf.json

You can also download an NDF directly for different environments by using the --env flag:

$ go run main.go getndf --env mainnet | jq . >ndf.json
// Or, run via the binary (assuming 64-bit Windows): 
$ ./client.win64 getndf --env mainnet | jq . >ndf.json

Sample content of ndf.json:

{
  "Timestamp": "2021-01-29T01:19:49.227246827Z",
  "Gateways": [
    {
      "Id": "BRM+Iotl6ujIGhjRddZMBdauapS7Z6jL0FJGq7IkUdYB",
      "Address": ":8440",
      "Tls_certificate": "-----BEGIN CERTIFICATE-----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\n6m52PyzMNV+2N21IPppKwA==\n-----END CERTIFICATE-----\n"
    },
    {
      "Id": "JCBd9mAQb2BW8hc8H9avy1ubcjUAa7MHrPp0dBU/VqQB",
	  .....

Sending safe messages between 2 users

To send messages with end-to-end encryption, you must first establish a connection or authenticated channel with the other user:

# Get user contact jsons for each client
$ client --password user1-password --ndf ndf.json -l client1.log -s user1session --writeContact user1-contact.json --unsafe -m "Hi to me, without E2E Encryption"
$ client --password user2-password --ndf ndf.json -l client2.log -s user2session --writeContact user2-contact.json --unsafe -m "Hi to me, without E2E Encryption"

# Request authenticated channel from another client. Note that the receiving client
# is expected to confirm the request before any specified timeout (default 120s)
$ client --password password --ndf ndf.json -l client.log -s session-directory --destfile user2-contact.json --waitTimeout 360 --unsafe-channel-creation --send-auth-request
WARNING: unsafe channel creation enabled
Adding authenticated channel for: Qm40C5hRUm7uhp5aATVWhSL6Mt+Z4JVBQrsEDvMORh4D
Message received:
Sending to Qm40C5hRUm7uhp5aATVWhSL6Mt+Z4JVBQrsEDvMORh4D:
Received 1

# Alternatively, to accept an authenticated channel request implicitly
# (should be within the timeout window of requesting client, or the request will need to be resent):
$ client --password "password" --ndf ndf.json -l client.log -s session-directory --destfile user2-contact.json" --unsafe-channel-creation --waitTimeout 200
Authentication channel request from: o+QpswTmnsuZve/QRz0j0RYNWqjgx4R5pACfO00Pe0cD
Sending to o+QpswTmnsuZve/QRz0j0RYNWqjgx4R5pACfO00Pe0cD:
Message received:
Received 1

# Send E2E Messages
$ client --password user1-password --ndf ndf.json -l client1.log -s user1session --destfile user2-contact.json -m "Hi User 2, from User 1 with E2E Encryption"
Sending to Qm40C5hRUm7uhp5aATVWhSL6Mt+Z4JVBQrsEDvMORh4D: Hi User 2, from User 1 with E2E Encryption
Timed out!
Received 0

$ client --password user2-password --ndf ndf.json -l client1.log -s user2session --destfile user1-contact.json -m "Hi User 1, from User 2 with E2E Encryption"
Sending to o+QpswTmnsuZve/QRz0j0RYNWqjgx4R5pACfO00Pe0cD: Hi User 1, from User 2 with E2E Encryption
Timed out!
Received 0
  • --password: The password used to encrypt and load the session.
  • --ndf: The network definition file.
  • -l: The file to write logs (user messages are still printed to stdout).
  • -s: The storage directory for client session data.
  • --writeContact: Output the user's contact information to this file.
  • --destfile is used to specify the recipient. You can also use --destid b64:... using the user's base64 id which is printed in the logs.
  • --unsafe: Send message without encryption (necessary whenever you have not already established an e2e channel).
  • --unsafe-channel-creation Auto-create and auto-accept channel requests.
  • -m: The message to send.

Note that the client defaults to sending to itself when a destination is not supplied. This is why we've used the --unsafe flag when creating the user contact jsons. However, when sending between users it is dropped in exchange for --unsafe-channel-creation.

For the authenticated channel creation to be considered "safe" the user should be prompted. You can do this on the command line by explicitly accepting the channel creation when sending a request with --send-auth-request and/or explicitly accepting a request with --accept-channel:

$ client --password user-password --ndf ndf.json -l client.log -s session-directory --destfile user-contact.json --accept-channel
Authentication channel request from: yYAztmoCoAH2VIr00zPxnj/ZRvdiDdURjdDWys0KYI4D
Sending to yYAztmoCoAH2VIr00zPxnj/ZRvdiDdURjdDWys0KYI4D:
Message received:
Received 1

Full usage of client can be found with client --help:

$ ./client --help
Runs a client for cMix anonymous communication platform

Usage:
  client [flags]
  client [command]

Available Commands:
  fileTransfer Send and receive file for cMix client
  generate     Generates version and dependency information for the Elixxir binary
  getndf       Download the network definition file from the network and print it.
  group        Group commands for cMix client
  help         Help about any command
  init         Initialize a user ID but do not connect to the network
  single       Send and respond to single-use messages.
  ud           Register for and search users using the xx network user discovery service.
  version      Print the version and dependency information for the Elixxir binary

Flags:
      --accept-channel            Accept the channel request for the corresponding recipient ID
      --auth-timeout uint         The number of seconds to wait for an authentication channelto confirm (default 120)
      --delete-all-requests       Delete the all contact requests, both sent and received.
      --backupIn string           Path to load backup client from
      --backupOut string          Path to output backup client.
      --backupPass string         Passphrase to encrypt/decrypt backup
      --delete-channel            Delete the channel information for the corresponding recipient ID
      --delete-receive-requests   Delete the all received contact requests.
      --delete-sent-requests      Delete the all sent contact requests.
      --destfile string           Read this contact file for the destination id
  -d, --destid string             ID to send message to (if below 40, will be precanned. Use '0x' or 'b64:' for hex and base64 representations) (default "0")
      --e2eMaxKeys uint           Max keys used before blocking until a rekey completes (default 800)
      --e2eMinKeys uint           Minimum number of keys used before requesting rekey (default 500)
      --e2eNumReKeys uint         Number of rekeys reserved for rekey operations (default 16)
      --e2eRekeyThreshold float64 Number between 0 an 1. Percent of keys used before a rekey is started
      --forceHistoricalRounds     Force all rounds to be sent to historical round retrieval
      --forceMessagePickupRetry   Enable a mechanism which forces a 50% chance of no message pickup, instead triggering the message pickup retry mechanism
  -h, --help                      help for client
  -l, --log string                Path to the log output path (- is stdout) (default "-")
  -v, --logLevel uint             Verbose mode for debugging
  -m, --message string            Message to send
  -n, --ndf string                Path to the network definition JSON file (default "ndf.json")
  -p, --password string           Password to the session file
      --profile-cpu string        Enable cpu profiling to this file
      --protoUserOut string       Path to which a normally constructed client will write proto user JSON file
      --protoUserPath string      Path to proto user JSON file containing cryptographic primitives the client will load
      --receiveCount uint         How many messages we should wait for before quitting (default 1)
      --regcode string            Identity code (optional)
      --send-auth-request         Send an auth request to the specified destination and waitfor confirmation
      --sendCount uint            The number of times to send the message (default 1)
      --sendDelay uint            The delay between sending the messages in ms (default 500)
      --sendid uint               Use precanned user id (must be between 1 and 40, inclusive)
  -s, --session string            Sets the initial storage directory for client session data
      --slowPolling               Enables polling for unfiltered network updates with RSA signatures
      --unsafe                    Send raw, unsafe messages without e2e encryption.
      --unsafe-channel-creation   Turns off the user identity authenticated channel check, automatically approving authenticated channels
      --verboseRoundTracking      Verbose round tracking, keeps track and prints all rounds the client was aware of while running. Defaults to false if not set.
      --verify-sends              Ensure successful message sending by checking for round completion
      --waitTimeout uint          The number of seconds to wait for messages to arrive (default 15)
  -w, --writeContact string       Write contact information, if any, to this file,  defaults to stdout (default "-")

Use "client [command] --help" for more information about a command.

Note: The client cannot be used on the betanet with precanned user ids.

Library Overview

The xx client is designed to be used as a go library (and by extension a c library).

Support is also present for go mobile to build Android and iOS libraries. We bind all exported symbols from the bindings package for use on mobile platforms.

Implementation Notes

Clients need to perform the same actions in the same order as shown in cmd/root.go. Specifically, certain handlers need to be registered and set up before starting network threads. Additionally, you cannot perform certain actions until the network connection reaches a "healthy" state.

See main.go for relevant code listings on when and how to perform these actions. The Getting Started guide provides further detail.

You can also visit the API Quick Reference for information on the types and functions exposed by the Client API.

The main entry point for developing with the client is api/client (or bindings/client). We recommend using go doc to explore:

go doc -all ./api
go doc -all ./interfaces

Looking at the API will, for example, show you there is a RoundEvents callback registration function, which lets your client see round events:

func (c *Client) GetRoundEvents() interfaces.RoundEvents
    RegisterRoundEventsCb registers a callback for round events.

and then inside interfaces:

type RoundEvents interface {
        // designates a callback to call on the specified event
        // rid is the id of the round the event occurs on
        // callback is the callback the event is triggered on
        // timeout is the amount of time before an error event is returned
        // valid states are the states which the event should trigger on
        AddRoundEvent(rid id.Round, callback ds.RoundEventCallback,
                timeout time.Duration, validStates ...states.Round) *ds.EventCallback

        // designates a go channel to signal the specified event
        // rid is the id of the round the event occurs on
        // eventChan is the channel the event is triggered on
        // timeout is the amount of time before an error event is returned
        // valid states are the states which the event should trigger on
        AddRoundEventChan(rid id.Round, eventChan chan ds.EventReturn,
                timeout time.Duration, validStates ...states.Round) *ds.EventCallback

        //Allows the un-registration of a round event before it triggers
        Remove(rid id.Round, e *ds.EventCallback)
}

Which, when investigated, yields the following prototype:

// Callbacks must use this function signature
type RoundEventCallback func(ri *pb.RoundInfo, timedOut bool)

showing that you can receive a full RoundInfo object for any round event received by the client library on the network.

Building the Library for iOS and Android

To set up Gomobile for Android, install the NDK and pass the -ndk flag to $ gomobile init. Other repositories that use Gomobile for binding should include a shell script that creates the bindings. For iOS, gomobile must be run on an OS X machine with Xcode installed.

Important reference info:

  1. Setting up Gomobile and subcommands
  2. Reference cycles, type restrictions

To clone and build:

# Go mobile install
go get -u golang.org/x/mobile/cmd/gomobile
go get -u golang.org/x/mobile/bind
gomobile init... # Note this line will be different depending on sdk/target!
# Get and test code
git clone https://gitlab.com/elixxir/client.git client
cd client
go mod vendor -v
go mod tidy
go test ./...
# Android
gomobile bind -target android -androidapi 21 gitlab.com/elixxir/client/bindings
# iOS
gomobile bind -target ios gitlab.com/elixxir/client/bindings
zip -r iOS.zip Bindings.framework

You can verify that all symbols got bound by unzipping bindings-sources.jar and inspecting the resulting source files.

Every time you make a change to the client or bindings, you must rebuild the client bindings into a .aar or iOS.zip to propagate those changes to the app. There's a script that runs gomobile for you in the bindings-integration repository.

Roadmap

See the larger network documentation for more, but there are 2 specific parts of the roadmap that are intended for the client:

  • Ephemeral IDs - Sending messages to users with temporal/ephemeral recipient user identities.
  • User Discovery - A bot that will allow the user to look for others on the network.
  • Notifications - An optional notifications system which uses firebase
  • Efficiency improvements - mechanisms for message pickup and network tracking
  • will evolve to allow tradeoffs and options for use

We are also always looking at simplifying and improving the library interface.