Nager.PublicSuffix (PSL)

With so many different endings for domain names, it's hard to know if they're valid or not. This project uses a list from publicsuffix.org, which keeps track of all the common endings like .com or .org. It checks domain names against this list to see if they're okay. Then, it splits the domain into three parts: the ending (like .com), the main part (like google), and any subparts (like www). You can find the list on GitHub under publicsuffix list repository.

Features

• High performance
• CacheProvider
• Async support
• Hot reload of rule data

Use cases

• Cookie restriction for browsers
• Domain highlighting in the URL bar of browsers
• DMARC E-Mail Security
• Certificate requests (ACME)
• Determining Valid Wildcard Certificates
• Two-factor authentication (FIDO)

Parts of a Domain

| Fully Qualified Domain Name (FQDN) | Top Level Domain (TLD) | Domain | Subdomain | |---------------------------- | ------------------------------ | ---------- | --------- | | blog.google.com | com | google | blog | | 22.cn | cn | 22 | | | www.volkswagen.de | de | volkswagen | www | | www.amazon.co.uk | co.uk | amazon | www | | www.wikipedia.org | org | wikipedia | www |

Installation

The package is available on NuGet

PM> install-package Nager.PublicSuffix

Usage Examples

Automatic rule provider

Automatically downloads the public suffix list:

var ruleProvider = new SimpleHttpRuleProvider();
await ruleProvider.BuildAsync();

var domainParser = new DomainParser(ruleProvider);

var domainInfo = domainParser.Parse("sub.test.co.uk");

Analyze domain

var ruleProvider = new LocalFileRuleProvider("public_suffix_list.dat");
await ruleProvider.BuildAsync();

var domainParser = new DomainParser(ruleProvider);

var domainInfo = domainParser.Parse("sub.test.co.uk");
//domainInfo.Domain = "test";
//domainInfo.FullyQualifiedDomainName = "sub.test.co.uk";
//domainInfo.RegistrableDomain = "test.co.uk";
//domainInfo.Subdomain = "sub";
//domainInfo.TopLevelDomain = "co.uk";

Check is a valid domain

var ruleProvider = new LocalFileRuleProvider("public_suffix_list.dat");
await ruleProvider.BuildAsync();

var domainParser = new DomainParser(ruleProvider);

var isValid = domainParser.IsValidDomain("sub.test.co.uk");

asp.net Intergration

// after -> var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHttpClient(); //Required for CachedHttpRuleProvider
builder.Services.AddSingleton<ICacheProvider, LocalFileSystemCacheProvider>();
builder.Services.AddSingleton<IRuleProvider, CachedHttpRuleProvider>();
builder.Services.AddSingleton<IDomainParser, DomainParser>();

// after -> var app = builder.Build();
var ruleProvider = app.Services.GetService<IRuleProvider>();
if (ruleProvider != null)
{
    await ruleProvider.BuildAsync();
}

// minimal api
app.MapGet("/DomainInfo/{domain}", (string domain, IDomainParser domainParser) =>
{
    domain = HttpUtility.UrlEncode(domain);

    var domainInfo = domainParser.Parse(domain);
    return domainInfo;
})
.WithName("DomainInfo")
.WithOpenApi();

Console App Integration

var httpClient = new HttpClient();
var cacheProvider = new Nager.PublicSuffix.RuleProviders.CacheProviders.LocalFileSystemCacheProvider();
var ruleProvider = new CachedHttpRuleProvider(cacheProvider, httpClient);

await ruleProvider.BuildAsync();

var domainParser = new DomainParser(ruleProvider);
var domainInfo = domainParser.Parse("example.com");

Use only ICANN Rules

var ruleProvider = new SimpleHttpRuleProvider(tldRuleDivisionFilter: TldRuleDivisionFilter.ICANNOnly);
await ruleProvider.BuildAsync();

var domainParser = new DomainParser(ruleProvider);

var domainInfo = domainParser.Parse("sub.test.co.uk");