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.

Changes to version 3

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• Add Support for .NET8
• Allow hot reload of rule data over the IRuleProvider
• Optimize Dependency Injection support
• Remove obsolete methods
• Fix UriDomainNormalizer bug with http://
• Cleanup project structure
• Optimize code documentation
• Add ILogger interface for logging issues
• Allow inject HttpClient for CachedHttpRuleProvider
• Error handling with TLD domains improved
• Optimize custom exception logic, use default message of exception class

Breaking changes

• Some namespaces have changed
• DomainInfo->Hostname renamed to DomainInfo->FullyQualifiedDomainName

Previous code for V2

The source code of version 2 can be found here

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

nuget

The package is available on nuget

PM> install-package Nager.PublicSuffix

Features

• High performance
• CacheProvider
• Async support

Code Examples

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");