flashlight

README

flashlight   

WARNING: The flashlight server will refuse to serve domain fronted traffic through most non-censored countries. See https://github.com/getlantern/flashlight-build/pull/141 for more details.

Lightweight host-spoofing web proxy written in go.

flashlight runs in one of two modes:

client - meant to run locally to wherever the browser is running, forwards requests to the server

server - handles requests from a flashlight client proxy and actually proxies them to the final destination

Using CloudFlare (and other CDNS), flashlight has the ability to masquerade as running on a different domain than it is. The client simply specifies the "masquerade" flag with a value like "thehackernews.com". flashlight will then use that masquerade host for the DNS lookup and will also specify it as the ServerName for SNI (though this is not actually necessary on CloudFlare). The Host header of the HTTP request will actually contain the correct host (e.g. getiantem.org), which causes CloudFlare to route the request to the correct host.

Flashlight uses enproxy to encapsulate data from/to the client as http request/response pairs. This allows it to tunnel regular HTTP as well as HTTPS traffic over CloudFlare. In fact, it can tunnel any TCP traffic.

Usage

Usage of flashlight:
  -addr="": ip:port on which to listen for requests. When running as a client proxy, we'll listen with http, when running as a server proxy we'll listen with https (required)
  -cloudconfig="": optional http(s) URL to a cloud-based source for configuration updates
  -cloudconfigca="": optional PEM encoded certificate used to verify TLS connections to fetch cloudconfig
  -configaddr="": if specified, run an http-based configuration server at this address
  -configdir="": directory in which to store configuration, including flashlight.yaml (defaults to current directory)
  -country="xx": 2 digit country code under which to report stats. Defaults to xx.
  -cpuprofile="": write cpu profile to given file
  -frontfqdns="": YAML string representing a map from the name of each front provider to a FQDN that will reach this particular server via that provider (e.g. '{cloudflare: fl-001.getiantem.org, cloudfront: blablabla.cloudfront.net}')
  -headless=false: if true, lantern will run with no ui
  -help=false: Get usage help
  -httptest.serve="": if non-empty, httptest.NewServer serves on this address and blocks
  -instanceid="": instanceId under which to report stats to statshub. If not specified, no stats are reported.
  -memprofile="": write heap profile to given file
  -parentpid=0: the parent process's PID, used on Windows for killing flashlight when the parent disappears
  -portmap=0: try to map this port on the firewall to the port on which flashlight is listening, using UPnP or NAT-PMP. If mapping this port fails, flashlight will exit with status code 50
  -proxyall=false: set to true to proxy all traffic through Lantern network
  -registerat="": base URL for peer DNS registry at which to register (e.g. https://peerscanner.getiantem.org)
  -role="": either 'client' or 'server' (required)
  -statshub="pure-journey-3547.herokuapp.com": address of statshub server
  -statsperiod=0: time in seconds to wait between reporting stats. If not specified, stats are not reported. If specified, statshub, instanceid and statshubAddr must also be specified.
  -test.bench="": regular expression to select benchmarks to run
  -test.benchmem=false: print memory allocations for benchmarks
  -test.benchtime=1s: approximate run time for each benchmark
  -test.blockprofile="": write a goroutine blocking profile to the named file after execution
  -test.blockprofilerate=1: if >= 0, calls runtime.SetBlockProfileRate()
  -test.coverprofile="": write a coverage profile to the named file after execution
  -test.cpu="": comma-separated list of number of CPUs to use for each test
  -test.cpuprofile="": write a cpu profile to the named file during execution
  -test.memprofile="": write a memory profile to the named file after execution
  -test.memprofilerate=0: if >=0, sets runtime.MemProfileRate
  -test.outputdir="": directory in which to write profiles
  -test.parallel=1: maximum test parallelism
  -test.run="": regular expression to select tests and examples to run
  -test.short=false: run smaller test suite to save time
  -test.timeout=0: if positive, sets an aggregate time limit for all tests
  -test.v=false: verbose: print additional output
  -uiaddr="": if specified, indicates host:port the UI HTTP server should be started on
  -unencrypted=false: set to true to run server in unencrypted mode (no TLS)

Example Client:

./flashlight -addr localhost:10080 -role client

Example Server:

./flashlight -addr :443 -role server

Example Curl Test:

curl -x localhost:10080 http://www.google.com/humans.txt
Google is built by a large team of engineers, designers, researchers, robots, and others in many different sites across the globe. It is updated continuously, and built with more tools and technologies than we can shake a stick at. If you'd like to help us out, see google.com/careers.

On the client, you should see something like this for every request:

Handling request for: http://www.google.com/humans.txt

Configuration Management

The configuration that will be fed to clients is managed using utilities in the genconfig/ subfolder.

Setup

You need the s3cmd tool installed and set up. To install on Ubuntu:

sudo apt-get install s3cmd

On OS X:

brew install s3cmd

And then run s3cmd --configure and follow the on-screen instructions. You can get AWS credentials that are good for uploading to S3 in too-many-secrets/lantern_aws/aws_credential.

Managing masquerade hosts

The file domains.txt contains the list of masquerade hosts we use, and blacklist.txt contains a list of blacklisted domains that we exclude even if present in domains.txt.

To alter the list of domains or blacklist:

1. Edit domains.txt and/or blacklist.txt
2. go run genconfig.go -domains domains.txt -blacklist blacklist.txt.
3. Commit the changed masquerades.go and cloud.yaml to git if you want.
4. Upload cloud.yaml to s3 using udpateyaml.bash if you want.

Managing proxied sites

Lists of proxied sites are expected to live as text files in a directory, one domain per line. You provide this directory to genconfig with the -proxiedsites argument.

Managing chained proxies

The IPs, access tokens, and other details that clients need in order to connect to the chained (that is, non-fronted) proxies we run are contained in a JSON file that normally lives in genconfig/fallbacks.json and is fed to genconfig with the optional -fallbacks argument.

You only to concern yourself with this when the list of chained proxies changes (e.g., when we launch or kill some server). To learn how to reenerate the fallbacks.json file in that case, see the relevant section of the README of the lantern_aws project.

Uploading to redis

To add a bunch of servers to the queue of a datacenter, so they'll get pulled by the config server as necessary,

• Compile a fallbacks.json that only includes the given servers. The quickest way to do this would be to generate the fallbacks.json with a prefix that only includes these servers.

• Generate a cloud.yaml from this fallbacks.json, as explained above.

• In the genconfig directory, run ./cfg2redis.py cloud.yaml <dc>, where <dc> is the datacenter where the servers are located. Current values are 'doams3' for the Digital Ocean Amsterdam 3 datacenter, and 'vltok1' for the Vulture Tokyo datacenter. Add the --dc option if you want to upload the datacenter configuration too (e.g., if this is a new datacenter), but of course make sure the cloud.yaml contains the right configuration for that datacenter (e.g. the right fronted round robin(s)).

The cfg2redis has some prerequisites. Just try it and it will tell you how to fulfill any missing ones.

If you only want to update the datacenter configuration you may say

echo "[]" > fallbacks.json
./genconfig.bash
./cfg2redis.py --dc cloud.yaml doams3

Documentation

Index

• Constants
• Variables
• func Run(httpProxyAddr string, socksProxyAddr string, configDir string, ...) error

Constants

const (
	// While in development mode we probably would not want auto-updates to be
	// applied. Using a big number here prevents such auto-updates without
	// disabling the feature completely. The "make package-*" tool will take care
	// of bumping this version number so you don't have to do it by hand.
	DefaultPackageVersion = "9999.99.99"
)

Variables

var (
	PackageVersion = bestPackageVersion()

	Version      string
	RevisionDate string // The revision date and time that is associated with the version string.
	BuildDate    string // The actual date and time the binary was built.

)

Functions

func Run

func Run(httpProxyAddr string,
	socksProxyAddr string,
	configDir string,
	stickyConfig bool,
	proxyAll func() bool,
	flagsAsMap map[string]interface{},
	beforeStart func(cfg *config.Config) bool,
	afterStart func(cfg *config.Config),
	onConfigUpdate func(cfg *config.Config),
	onError func(err error)) error

Run runs a client proxy. It blocks as long as the proxy is running.