/fido2-net-lib

FIDO2 .NET library for FIDO2 / WebAuthn Attestation and Assertion using .NET

Primary LanguageC#MIT LicenseMIT

FIDO2 .NET Library (WebAuthn)

A working implementation library + demo for FIDO2 and WebAuthn using .NET

Build status Test Status

Purpose

To provide a developer friendly and well tested .NET FIDO2 Server / WebAuthn relying party library for the easy validation of registration (attestation) and authentication (assertion) of FIDO2 / WebAuthn credentials, in order to increase the adoption of the technology, ultimately defeating phishing attacks.

Install-Package Fido2 -Version 1.0.0-preview3

Demo

What is FIDO2?

The passwordless web is coming.
FIDO2 / WebAuthn is a new open authentication standard, supported by browsers and many large tech companies such as Microsoft, Google etc. The main driver is to allow a user to login without passwords, creating passwordless flows or strong MFA for user signup/login on websites. The standard is not limited to web applications with support coming to Active Directory and native apps. The technology builds on public/private keys, allowing authentication to happen without sharing a secret between the user & platform. This brings many benefits, such as easier and safer logins and makes phishing attempts extremely hard.

Read more:

Supported features

  • ✅ Attestation API & verification (Register and verify credentials/authenticators)
  • ✅ Assertion API & verification (Authenticate users)
  • ✅ 100% pass rate in conformance testing (results)
  • ✅ FIDO2 security keys aka roaming authenticators (spec), like SoloKeys Solo, Yubico YubiKey, and Feitian BioPass FIDO2)
  • ✅ Device embedded authenticators aka platform authenticators (spec), like Android Key and TPM)
  • ✅ Backwards compatibility with FIDO U2F authenticators (spec)
  • ✅ Windows Hello
  • ✅ All currently referenced cryptographic algorithms for FIDO2 Server (spec)
  • ✅ All current attestation formats: "packed", "tpm", "android-key", "android-safetynet", "fido-u2f", and "none" (spec)
  • ✅ FIDO2 Server attestation validation via FIDO Metadata Service (spec)
  • ✅ WebAuthn extensions (spec)
  • ✅ Examples & demos
  • ✅ Intellisense documentation
  • 💤 Formal documentation
  • 💤 Recommended usage patterns

Configuration

Only some options are mentioned here, see the Configuration class for all options

  • fido2:MDSAccessKey - App Secret / environment variable that holds the FIDO2 MDS AccessKey. Required when using the default MetadataService provider.
  • fido2:MDSCacheDirPath - App Secret / environment variable that sets the cache path for the MDS. Required when using the default MetadataService provider.

Examples

See the demo controller for full examples of both attestation and assertion.

See the test controller for examples of how to pass the conformance tests.

See the Active Directory Store information and example credential store for ideas on how to integrate this library with an on-premises Active Directory.

Create attestation Options

To add FIDO2 credentials to an existing user account, we we perform a attestation process. It starts with returning options to the client.

// file: Controller.cs
// 1. Get user from DB by username (in our example, auto create missing users)
var user = DemoStorage.GetOrAddUser(username, () => new User
{
    DisplayName = "Display " + username,
    Name = username,
    Id = Encoding.UTF8.GetBytes(username) // byte representation of userID is required
});

// 2. Get user existing keys by username
List<PublicKeyCredentialDescriptor> existingKeys = DemoStorage.GetCredentialsByUser(user).Select(c => c.Descriptor).ToList();

// 3. Create options
var options = _lib.RequestNewCredential(user, existingKeys, AuthenticatorSelection.Default, AttestationConveyancePreference.Parse(attType));

// 4. Temporarily store options, session/in-memory cache/redis/db
HttpContext.Session.SetString("fido2.attestationOptions", options.ToJson());

// 5. return options to client
return Json(options);

Register credentials

When the client returns a response, we verify and register the credentials.

// file: Controller.cs
// 1. get the options we sent the client
var jsonOptions = HttpContext.Session.GetString("fido2.attestationOptions");
var options = CredentialCreateOptions.FromJson(jsonOptions);

// 2. Create callback so that lib can verify credential id is unique to this user
IsCredentialIdUniqueToUserAsyncDelegate callback = async (IsCredentialIdUniqueToUserParams args) =>
{
    List<User> users = await DemoStorage.GetUsersByCredentialIdAsync(args.CredentialId);
    if (users.Count > 0) return false;

    return true;
};

// 2. Verify and make the credentials
var success = await _lib.MakeNewCredentialAsync(attestationResponse, options, callback);

// 3. Store the credentials in db
DemoStorage.AddCredentialToUser(options.User, new StoredCredential
{
    Descriptor = new PublicKeyCredentialDescriptor(success.Result.CredentialId),
    PublicKey = success.Result.PublicKey,
    UserHandle = success.Result.User.Id
});

// 4. return "ok" to the client
return Json(success);

Create Assertion options

When a user wants to log a user in, we do an assertion based on the registered credentials.

First we create the assertion options and return to the client.

// file: Controller.cs
// 1. Get user from DB
var user = DemoStorage.GetUser(username);
if (user == null) return NotFound("username was not registered");

// 2. Get registered credentials from database
List<PublicKeyCredentialDescriptor> existingCredentials = DemoStorage.GetCredentialsByUser(user).Select(c => c.Descriptor).ToList();

// 3. Create options
var options = _lib.GetAssertionOptions(
    existingCredentials,
    UserVerificationRequirement.Discouraged
);

// 4. Temporarily store options, session/in-memory cache/redis/db
HttpContext.Session.SetString("fido2.assertionOptions", options.ToJson());

// 5. Return options to client
return Json(options);

Verify the assertion response

When the client returns a response, we verify it and accepts the login.

// 1. Get the assertion options we sent the client
var jsonOptions = HttpContext.Session.GetString("fido2.assertionOptions");
var options = AssertionOptions.FromJson(jsonOptions);

// 2. Get registered credential from database
StoredCredential creds = DemoStorage.GetCredentialById(clientResponse.Id);

// 3. Get credential counter from database
var storedCounter = creds.SignatureCounter;

// 4. Create callback to check if userhandle owns the credentialId
IsUserHandleOwnerOfCredentialIdAsync callback = async (args) =>
{
    List<StoredCredential> storedCreds = await DemoStorage.GetCredentialsByUserHandleAsync(args.UserHandle);
    return storedCreds.Exists(c => c.Descriptor.Id.SequenceEqual(args.CredentialId));
};

// 5. Make the assertion
var res = await _lib.MakeAssertionAsync(clientResponse, options, creds.PublicKey, storedCounter, callback);

// 6. Store the updated counter
DemoStorage.UpdateCounter(res.CredentialId, res.Counter);

// 7. return OK to client
return Json(res);

Nuget package

Install-Package Fido2 -Version 1.0.0-preview

https://www.nuget.org/packages/Fido2/

Contributing

To run the project locally

Start Fido2Demo (preferably https, expected url https://localhost:44329) and open https://localhost:44329/ in the browser. You also need to either set the MetadataService to null or add the applicationSettings as described below.

The HTML and javascript is copied (and then updated) from WebAuthn.io.

Feedback, issues and pull requests are VERY welcome.

Build

Build status Test Status

All PR's and the master branch is built with Azure Devops.

Scripts to build, pack and publish a nuget package are located in ./scripts/

Conformance testing tool

To run a suit of test of different verifications and attestation formats, register and download the FIDO Test tools

Other

A complimentary blog post with some lessons learned since starting this library