smart

README

Smart Dialer

The Smart Dialer searches for a strategy that unblocks DNS and TLS for a given list of test domains. It takes a config describing multiple strategies to pick from.

JSON config for the Smart Dialer

The config that the Smart Dialer takes is in a JSON format. Here is an example:

{
  "dns": [
      {"system": {}},
      {"https": {"name": "8.8.8.8"}},
      {"https": {"name": "9.9.9.9"}}
  ],
  "tls": [
      "",
      "split:2",
      "tlsfrag:1"
  ]
}

DNS Configuration

• The dns field specifies a list of DNS resolvers to test.
• Each DNS resolver can be one of the following types:
  • system: Use the system resolver. Specify with an empty object.
  • https: Use an encrypted DNS over HTTPS (DoH) resolver.
  • tls: Use an encrypted DNS over TLS (DoT) resolver.
  • udp: Use a UDP resolver.
  • tcp: Use a TCP resolver.

DNS-over-HTTPS Resolver (DoH)

{
  "https": {
    "name": "dns.google",
    "address": "8.8.8.8"
  }
}

• name: The domain name of the DoH server.
• address: The host:port of the DoH server. Defaults to name:443.

DNS-over-TLS Resolver (DoT)

{
  "tls": {
    "name": "dns.google",
    "address": "8.8.8.8"
  }
}

• name: The domain name of the DoT server.
• address: The host:port of the DoT server. Defaults to name:853.

UDP Resolver

{
  "udp": {
    "address": "8.8.8.8"
  }
}

• address: The host:port of the UDP resolver.

TCP Resolver

{
  "tcp": {
    "address": "8.8.8.8"
  }
}

• address: The host:port of the TCP resolver.

TLS Configuration

• The tls field specifies a list of TLS transports to test.
• Each TLS transport is a string that specifies the transport to use.
• For example, override:host=cloudflare.net|tlsfrag:1 specifies a transport that uses domain fronting with Cloudflare and TLS fragmentation. See the config documentation for details.

Using the Smart Dialer

To use the Smart Dialer, create a StrategyFinder object and call the NewDialer method, passing in the list of test domains and the JSON config. The NewDialer method will return a transport.StreamDialer that can be used to create connections using the found strategy. For example:

finder := &smart.StrategyFinder{
    TestTimeout:  5 * time.Second,
    LogWriter:   os.Stdout,
    StreamDialer: &transport.TCPDialer{},
    PacketDialer: &transport.UDPDialer{},
}

configBytes := []byte(`
{
  "dns": [
      {"system": {}},
      {"https": {"name": "8.8.8.8"}},
      {"https": {"name": "9.9.9.9"}}
  ],
  "tls": [
      "",
      "split:2",
      "tlsfrag:1"
  ]
}
`)

dialer, err := finder.NewDialer(context.Background(), []string{"www.google.com"}, configBytes)
if err != nil {
    // Handle error.
}

// Use dialer to create connections.

Please note that this is a basic example and may need to be adapted for your specific use case.

Documentation

Overview

Package smart provides utilities to dynamically find serverless strategies for circumvention.

Index

• type StrategyFinder
  • func (f *StrategyFinder) NewDialer(ctx context.Context, testDomains []string, configBytes []byte) (transport.StreamDialer, error)

Types

type StrategyFinder

type StrategyFinder struct {
	TestTimeout  time.Duration
	LogWriter    io.Writer
	StreamDialer transport.StreamDialer
	PacketDialer transport.PacketDialer
	// contains filtered or unexported fields
}

func (*StrategyFinder) NewDialer

func (f *StrategyFinder) NewDialer(ctx context.Context, testDomains []string, configBytes []byte) (transport.StreamDialer, error)

NewDialer uses the config in configBytes to search for a strategy that unblocks DNS and TLS for all of the testDomains, returning a dialer with the found strategy. It returns an error if no strategy was found that unblocks the testDomains. The testDomains must be domains with a TLS service running on port 443.