README

java-webauthn-server
====================
:toc:
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:toc-title:

image:https://github.com/Yubico/java-webauthn-server/workflows/build/badge.svg["Build Status", link="https://github.com/Yubico/java-webauthn-server/actions"]
image:https://coveralls.io/repos/github/Yubico/java-webauthn-server/badge.svg["Coverage Status", link="https://coveralls.io/github/Yubico/java-webauthn-server"]

Server-side https://www.w3.org/TR/webauthn/[Web Authentication] library for
Java. Provides implementations of the
https://www.w3.org/TR/webauthn/#rp-operations[Relying Party operations] required
for a server to support Web Authentication. This includes registering
authenticators and authenticating registered authenticators.


toc::[]


== Dependency configuration

Maven:

----------
<dependency>
  <groupId>com.yubico</groupId>
  <artifactId>webauthn-server-core</artifactId>
  <version>1.9.1</version>
  <scope>compile</scope>
</dependency>
----------

Gradle:

----------
compile 'com.yubico:webauthn-server-core:1.9.1'
----------

=== Semantic versioning

This library uses link:https://semver.org/[semantic versioning].
The public API consists of all public classes, methods and fields in the `com.yubico.webauthn` package and its subpackages,
i.e., everything covered by the
link:https://developers.yubico.com/java-webauthn-server/JavaDoc/webauthn-server-core/latest/com/yubico/webauthn/package-summary.html[Javadoc].

Package-private classes and methods are NOT part of the public API.
The `com.yubico:yubico-util` module is NOT part of the public API.
Breaking changes to these will NOT be reflected in version numbers.


=== Additional modules

In addition to the main `webauthn-server-core` module, there are also:

- `webauthn-server-attestation`: A simple implementation of the
  link:https://developers.yubico.com/java-webauthn-server/JavaDoc/webauthn-server-core/latest/com/yubico/webauthn/attestation/MetadataService.html[`MetadataService`]
  interface, which by default comes preloaded with attestation metadata for Yubico devices.

- `webauthn-server-core-minimal`: Alternative distribution of `webauthn-server-core`,
  without a dependency on BouncyCastle.
  If depending on this module instead of `webauthn-server-core`,
  you may have to add your own JCA providers to support some signature algorithms.
  In particular, OpenJDK 14 and earlier does not include providers for the EdDSA family of algorithms.


== Features

- Generates request objects suitable as parameters to
  `navigator.credentials.create()` and `.get()`
- Performs all necessary
  https://www.w3.org/TR/webauthn/#rp-operations[validation logic] on the
  response from the client
- No mutable state or side effects - everything (except builders) is thread safe
- Optionally integrates with a "metadata service" to verify
  https://www.w3.org/TR/webauthn/#sctn-attestation[authenticator attestations]
  and annotate responses with additional authenticator metadata
- Reproducible builds: release signatures match fresh builds from source. See
  [Building](#Building) below.


=== Non-features

This library has no concept of accounts, sessions, permissions or identity
federation, and it's not an authentication framework; it only deals with
executing the WebAuthn authentication mechanism. Sessions, account management
and other higher level concepts can make use of this authentication mechanism,
but the authentication mechanism alone does not make a security system.


== Documentation

See the
link:https://developers.yubico.com/java-webauthn-server/JavaDoc/webauthn-server-core/latest/com/yubico/webauthn/package-summary.html[Javadoc]
for in-depth API documentation.


== Quick start

Implement the
link:https://developers.yubico.com/java-webauthn-server/JavaDoc/webauthn-server-core/latest/com/yubico/webauthn/CredentialRepository.html[`CredentialRepository`]
interface with your database access logic. See
link:https://github.com/Yubico/java-webauthn-server/blob/master/webauthn-server-demo/src/main/java/demo/webauthn/InMemoryRegistrationStorage.java[`InMemoryRegistrationStorage`]
for an example.

Instantiate the
link:https://developers.yubico.com/java-webauthn-server/JavaDoc/webauthn-server-core/latest/com/yubico/webauthn/RelyingParty.html[`RelyingParty`]
class:

[source,java]
----------
RelyingPartyIdentity rpIdentity = RelyingPartyIdentity.builder()
    .id("example.com")
    .name("Example Application")
    .build();

RelyingParty rp = RelyingParty.builder()
    .identity(rpIdentity)
    .credentialRepository(new MyCredentialRepository())
    .build();
----------


=== Registration

Initiate a registration ceremony:

[source,java]
----------
byte[] userHandle = new byte[64];
random.nextBytes(userHandle);

PublicKeyCredentialCreationOptions request = rp.startRegistration(StartRegistrationOptions.builder()
    .user(UserIdentity.builder()
        .name("alice")
        .displayName("Alice Hypothetical")
        .id(new ByteArray(userHandle))
        .build())
    .build());
----------

Serialize `request` to JSON and send it to the client:

[source,java]
----------
import com.fasterxml.jackson.databind.ObjectMapper;

ObjectMapper jsonMapper = new ObjectMapper()
    .configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false)
    .setSerializationInclusion(Include.NON_ABSENT)
    .registerModule(new Jdk8Module());

String json = jsonMapper.writeValueAsString(request);
return json;
----------

Get the response from the client:

[source,java]
----------
String responseJson = /* ... */;
PublicKeyCredential<AuthenticatorAttestationResponse, ClientRegistrationExtensionOutputs> pkc =
    PublicKeyCredential.parseRegistrationResponseJson(responseJson);
----------

Validate the response:

[source,java]
----------
try {
    RegistrationResult result = rp.finishRegistration(FinishRegistrationOptions.builder()
        .request(request)
        .response(pkc)
        .build());
} catch (RegistrationFailedException e) { /* ... */ }
----------

Update your database:

[source,java]
----------
storeCredential("alice", result.getKeyId(), result.getPublicKeyCose());
----------


=== Authentication

Initiate an authentication ceremony:


[source,java]
----------
AssertionRequest request = rp.startAssertion(StartAssertionOptions.builder()
    .username(Optional.of("alice"))
    .build());
String json = jsonMapper.writeValueAsString(request);
return json;
----------

Validate the response:

[source,java]
----------
String responseJson = /* ... */;

PublicKeyCredential<AuthenticatorAssertionResponse, ClientAssertionExtensionOutputs> pkc =
    PublicKeyCredential.parseAssertionResponseJson(responseJson);

try {
    AssertionResult result = rp.finishAssertion(FinishAssertionOptions.builder()
        .request(request)
        .response(pkc)
        .build());

    if (result.isSuccess()) {
        return result.getUsername();
    }
} catch (AssertionFailedException e) { /* ... */ }
throw new RuntimeException("Authentication failed");
----------

For more detailed example usage, see
link:webauthn-server-demo[`webauthn-server-demo`] for a complete demo server.


== Architecture

The library tries to place as few requirements on the overall application
architecture as possible. For this reason it is stateless and free from side
effects, and does not directly interact with any database. This means it is
database agnostic and thread safe. The following diagram illustrates an example
architecture for an application using the library.

image::https://raw.githubusercontent.com/Yubico/java-webauthn-server/master/docs/img/demo-architecture.svg?sanitize=true["Example application architecture",align="center"]

The application manages all state and database access, and communicates with the
library via POJO representations of requests and responses. The following
diagram illustrates the data flow during a WebAuthn registration or
authentication ceremony.

image::https://raw.githubusercontent.com/Yubico/java-webauthn-server/master/docs/img/demo-sequence-diagram.svg?sanitize=true["WebAuthn ceremony sequence diagram",align="center"]

In this diagram, the *Client* is the user's browser and the application's
client-side scripts. The *Server* is the application and its business logic, the
*Library* is this library, and the *Users* database stores registered WebAuthn
credentials.

. The client requests to start the ceremony, for example by submitting a form.
  The `username` may or may not be known at this point. For example, the user
  might be requesting to create a new account, or we might be using
  username-less authentication.

. If the user does not already have a
  https://www.w3.org/TR/webauthn/#user-handle[user handle], the application
  creates one in some application-specific way.

. The application may choose to authenticate the user with a password or the
  like before proceeding.

. The application calls one of the library's "start" methods to generate a
  parameter object to be passed to `navigator.credentials.create()` or `.get()`
  on the client.

. The library generates a random challenge and an assortment of other arguments
  depending on configuration set by the application.

. If the `username` is known, the library uses a read-only database adapter
  provided by the application to look up the user's credentials.

. The returned list of https://www.w3.org/TR/webauthn/#credential-id[credential
  IDs] is used to populate the
  https://www.w3.org/TR/webauthn/#dom-publickeycredentialcreationoptions-excludecredentials[`excludeCredentials`]
  or
  https://www.w3.org/TR/webauthn/#dom-publickeycredentialrequestoptions-allowcredentials[`allowCredentials`]
  parameter.

. The library returns a `request` object which can be serialized to JSON and
  passed as the `publicKey` argument to `navigator.credentials.create()` or
  `.get()`. For registration ceremonies this will be a
  https://www.w3.org/TR/webauthn/#dictdef-publickeycredentialcreationoptions[`PublicKeyCredentialCreationOptions`],
  and for authentication ceremonies it will be a
  https://www.w3.org/TR/webauthn/#dictdef-publickeycredentialrequestoptions[`PublicKeyCredentialRequestOptions`].
  The application stores the `request` in temporary storage.

. The application's client-side script runs `navigator.credentials.create()` or
  `.get()` with `request` as the `publicKey` argument.

. The user confirms the operation and the client returns a
  https://www.w3.org/TR/webauthn/#public-key-credential[`PublicKeyCredential`]
  object `response` to the application.

. The application retrieves the `request` from temporary storage and passes
  `request` and `response` to one of the library's "finish" methods to run the
  response validation logic.

. The library verifies that the `response` contents - challenge, origin, etc. -
  are valid.

. If this is an authentication ceremony, the library uses the database adapter
  to look up the public key for the credential named in `response.id`.

. The database adapter returns the public key.

. The library verifies the authentication signature.

. The library returns a POJO representation of the result of the ceremony. For
  registration ceremonies, this will include the credential ID and public key of
  the new credential. The application may opt in to also getting
  information about the authenticator model and whether the authenticator
  attestation is trusted. For authentication ceremonies, this will include the
  username and user handle, the credential ID of the credential used, and the
  new https://www.w3.org/TR/webauthn/#signature-counter[signature counter] value
  for the credential.

. The application inspects the result object and takes any appropriate actions
  as defined by its business logic.

. If the result is not satisfactory, the application reports failure to the
  client.

. If the result is satisfactory, the application proceeds with storing the new
  credential if this is a registration ceremony.

. If this is an authentication ceremony, the application updates the signature
  counter stored in the database for the credential.

. Finally, the application reports success and resumes its business logic.


== Building

Use the included
https://docs.gradle.org/current/userguide/gradle_wrapper.html[Gradle wrapper] to
build the `.jar` artifact:

----------
$ ./gradlew :webauthn-server-core:jar
----------

The output is built in the `webauthn-server-core/build/libs/` directory, and the
version is derived from the most recent Git tag. Builds done on a tagged commit
will have a plain `x.y.z` version number, while a build on any other commit will
result in a version number containing the abbreviated commit hash.

Starting in version `1.4.0-RC2`, artifacts are built reproducibly. Fresh builds from
tagged commits should therefore be verifiable by signatures from Maven Central
and GitHub releases:

```
$ git checkout 1.4.0-RC2
$ ./gradlew :webauthn-server-core:jar

$ wget https://repo1.maven.org/maven2/com/yubico/webauthn-server-core/1.4.0-RC2/webauthn-server-core-1.4.0-RC2.jar.asc
$ gpg --verify webauthn-server-core-1.4.0-RC2.jar.asc webauthn-server-core/build/libs/webauthn-server-core-1.4.0-RC2.jar

$ wget https://github.com/Yubico/java-webauthn-server/releases/download/1.4.0-RC2/webauthn-server-core-1.4.0-RC2.jar.asc
$ gpg --verify webauthn-server-core-1.4.0-RC2.jar.asc webauthn-server-core/build/libs/webauthn-server-core-1.4.0-RC2.jar
```

Note that building with a different JDK may produce a different artifact. To
ensure binary reproducibility, please build with the same JDK as specified in
the release notes. Reproducible builds also require building from a Git
repository, since the build embeds version number and Git commit ID into the
built artifacts.

Official Yubico software signing keys are listed on the
https://developers.yubico.com/Software_Projects/Software_Signing.html[Yubico
Developers site].


To run the tests:

----------
$ ./gradlew check
----------

To run the http://pitest.org/[PIT mutation tests] (this may take upwards of 30
minutes):

----------
$ ./gradlew pitest
----------