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Wednesday, 30 March 2016

flashlight- Lightweight domain fronting web proxy written in go

WARNING: The flashlight server will refuse to serve domain fronted traffic through most non-censored countries. See 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 "". 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., 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 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:, cloudfront:}')
  -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.
  -role="": either 'client' or 'server' (required)
  -statshub="": 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"": 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
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On the client, you should see something like this for every request:
Handling request for:

Configuration Management

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


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.