6.12.4 Connecting Using Web Authentication (WebAuthn) Authentication

Web Authentication (WebAuthn) enables user authentication for MySQL Server using devices such as smart cards, security keys, and biometric readers. WebAuthn enables passwordless authentication, and can be used for MySQL accounts that use multifactor authentication. It is supported by MySQL Enterprise Edition and Connector/J since release 8.2.0—see WebAuthn Pluggable Authentication for details.

The following explains how to use WebAuthn authentication with Connector/J. It assumes there is a MySQL server running and configured to support WebAuthn authentication, with the authentication plugin authentication_webauthn loaded and the system variable authentication_webauthn_rp_id properly configured. Although not always the case, FIDO authentication often works with multifactor authentication, so additional configuration might be necessary but, typically, a default MySQL installation is multifactor authentication ready.

Create a MySQL User

Create the MySQL user to be linked to the FIDO device. Use the mysql client with a root user:

mysql > CREATE USER 'johndoe'@'%' IDENTIFIED WITH caching_sha2_password BY 's3cr3t' AND IDENTIFIED WITH authentication_webauthn;
Query OK, 0 rows affected (0,02 sec)

Register the FIDO device by the user you just created. This is accomplished by running the mysql client on the same system the device is installed, which might require installing the mysql client in your working machine or moving the FIDO device to the system where the MySQL Server is running. In either case, issue the following command (additional command options to connect to the right server might be needed):

$ mysql --user=johndoe --password1 --register-factor=2
Enter password: <type "s3cr3t">
Please insert FIDO device and follow the instruction.  Depending on the device, you may have to perform gesture action multiple times.
1. Perform gesture action (Skip this step if you are prompted to enter device PIN).
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 8.2.0-commercial MySQL Enterprise Server - Commercial

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Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql >

Get 3rd-party Dependencies

MySQL Connector/J is a JDBC Type 4 driver, which is a 100% pure Java implementation, However, there is no pure Java library supporting the authentication devices that Connector/J can use. Therefore, developers need to implement the code that handles the interaction with the authentication devices, for which the following 3rd-party libraries are needed.

• The libfido2 native library, which must be installed in the system where the application will run.

• Some Java bindings, for example Java Native Interface (JNI) or Java Native Access (JNA). In the following example, Java Native Access (JNA) is used to implement our minimal Java bindings over the libfido2 library.

Implement the Native Bindings

Create a simple class (called FidoAssertion below) that implements the minimal set of bindings between Java and the libfido2 native library (consult the libfido2 manuals if needed):

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.PointerType;
import com.sun.jna.ptr.IntByReference;
import com.sun.jna.ptr.PointerByReference;

public class FidoAssertion {

    private interface LibFido2 extends Library {
        public static int FIDO_OK = 0;
        static class FidoAssertT extends PointerType {}
        static class FidoDevInfoT extends PointerType {}
        static class FidoDevT extends PointerType {}
        LibFido2 INSTANCE = Native.load("fido2", LibFido2.class);
        int fido_assert_allow_cred(FidoAssertT assrt, byte[] ptr, int len);
        int fido_assert_authdata_len(FidoAssertT assrt, int idx);
        Pointer fido_assert_authdata_ptr(FidoAssertT assrt, int idx);
        void fido_assert_free(PointerByReference assrt);
        FidoAssertT fido_assert_new();
        int fido_assert_count(FidoAssertT assrt);
        int fido_assert_set_clientdata_hash(FidoAssertT assrt, byte[] ptr, int len);
        int fido_assert_set_rp(FidoAssertT assrt, String id);
        int fido_assert_sig_len(FidoAssertT assrt, int idx);
        Pointer fido_assert_sig_ptr(FidoAssertT assrt, int idx);
        int fido_dev_close(FidoDevT dev);
        void fido_dev_free(PointerByReference dev);
        int fido_dev_get_assert(FidoDevT dev, FidoAssertT assrt, String pin);
        void fido_dev_info_free(PointerByReference devlist, int n);
        int fido_dev_info_manifest(FidoDevInfoT devlist, int ilen, IntByReference olen);
        FidoDevInfoT fido_dev_info_new(int n);
        String fido_dev_info_path(FidoDevInfoT di);
        FidoDevInfoT fido_dev_info_ptr(FidoDevInfoT devList, int size);
        FidoDevT fido_dev_new();
        int fido_dev_open(FidoDevT dev, String path);
        boolean fido_dev_supports_credman(FidoDevT dev);
        void fido_init(int flags);
    }

    private LibFido2.FidoAssertT fidoAssert;
    private LibFido2.FidoDevT fidoDev;
    private byte[] clientDataHash;
    private String relyingPartyId;
    private byte[] credentialId;
    private boolean supportsCredMan = false;

    public FidoAssertion() {
        LibFido2.INSTANCE.fido_init(0);
        initializeFidoDevice();
    }

    private void initializeFidoDevice() {
        LibFido2.FidoDevInfoT fidoDevInfo = LibFido2.INSTANCE.fido_dev_info_new(1);
        IntByReference olen = new IntByReference();
        int r = LibFido2.INSTANCE.fido_dev_info_manifest(fidoDevInfo, 1, olen);
        if (r != LibFido2.FIDO_OK) {
            throw new RuntimeException("Failed locating FIDO devices.");
        }
        LibFido2.FidoDevInfoT dev = LibFido2.INSTANCE.fido_dev_info_ptr(fidoDevInfo, 0);
        String path = LibFido2.INSTANCE.fido_dev_info_path(dev);

        LibFido2.INSTANCE.fido_dev_info_free(new PointerByReference(fidoDevInfo.getPointer()), 1);

        this.fidoDev = LibFido2.INSTANCE.fido_dev_new();
        r = LibFido2.INSTANCE.fido_dev_open(this.fidoDev, path);
        if (r != LibFido2.FIDO_OK) {
            throw new RuntimeException("Failed opening the FIDO device.");
        }

        this.supportsCredMan = LibFido2.INSTANCE.fido_dev_supports_credman(this.fidoDev);
    }

    boolean supportsCredentialManagement() {
        return this.supportsCredMan;
    }

    void setClienDataHash(byte[] clientDataHash) {
        this.clientDataHash = clientDataHash;
    }

    void setRelyingPartyId(String relyingPartyId) {
        this.relyingPartyId = relyingPartyId;
    }

    void setCredentialId(byte[] credentialId) {
        this.credentialId = credentialId;
    }

    void computeAssertions() {
        int r;
        this.fidoAssert = LibFido2.INSTANCE.fido_assert_new();

        // Set the Relying Party Id.
        r = LibFido2.INSTANCE.fido_assert_set_rp(this.fidoAssert, this.relyingPartyId);
        if (r != LibFido2.FIDO_OK) {
            throw new RuntimeException("Failed setting the relying party id.");
        }

        // Set the Client Data Hash.
        r = LibFido2.INSTANCE.fido_assert_set_clientdata_hash(this.fidoAssert, this.clientDataHash, this.clientDataHash.length);
        if (r != LibFido2.FIDO_OK) {
            throw new RuntimeException("Failed setting the client data hash.");
        }

        // Set the Credential Id. Not applicable when resident keys are used.
        if (this.credentialId.length > 0) {
            r = LibFido2.INSTANCE.fido_assert_allow_cred(this.fidoAssert, this.credentialId, this.credentialId.length);
            if (r != LibFido2.FIDO_OK) {
                throw new RuntimeException("Failed setting the credential id.");
            }
        }

        // Obtain the assertion(s) from the FIDO device.
        r = LibFido2.INSTANCE.fido_dev_get_assert(this.fidoDev, this.fidoAssert, null);
        if (r != LibFido2.FIDO_OK) {
            throw new RuntimeException("Failed obtaining the assertion(s) from the FIDO device.");
        }
    }

    public int getAssertCount() {
        int assertCount = LibFido2.INSTANCE.fido_assert_count(this.fidoAssert);
        return assertCount;
    }

    public byte[] getAuthenticatorData(int idx) {
        int authDataLen = LibFido2.INSTANCE.fido_assert_authdata_len(this.fidoAssert, idx);
        Pointer authData = LibFido2.INSTANCE.fido_assert_authdata_ptr(this.fidoAssert, idx);
        byte[] authenticatorData = authData.getByteArray(0, authDataLen);
        return authenticatorData;
    }

    public byte[] getSignature(int idx) {
        int sigLen = LibFido2.INSTANCE.fido_assert_sig_len(this.fidoAssert, idx);
        Pointer sigData = LibFido2.INSTANCE.fido_assert_sig_ptr(this.fidoAssert, idx);
        byte[] signature = sigData.getByteArray(0, sigLen);
        return signature;
    }

    public void freeResources() {
        LibFido2.INSTANCE.fido_dev_close(this.fidoDev);
        LibFido2.INSTANCE.fido_dev_free(new PointerByReference(this.fidoDev.getPointer()));
        LibFido2.INSTANCE.fido_assert_free(new PointerByReference(this.fidoAssert.getPointer()));
    }
}

Compile the class with a Java 8 compiler (or above).

$ javac -classpath *:. FidoAssertion.java

Implement the Authentication Callback

MySQL Connector/J uses a pluggable callback class that exchanges data between the authentication process and the interaction with the authentication device. This class must be an instance of the interface com.mysql.cj.callback.MysqlCallbackHandler, which defines one single method: void handle(MysqlCallback cb);. The MysqlCallback argument this method takes is an instance of com.mysql.cj.callback.WebAuthnAuthenticationCallback and it contains all the data required by the FIDO assertion code implemented earlier. Likewise, it also takes the output from the FIDO device (authenticator data and signatures) to the running authentication process.

Here is one possible implementation of the WebAuthnAuthenticationCallback.

import com.mysql.cj.callback.MysqlCallback;
import com.mysql.cj.callback.MysqlCallbackHandler;
import com.mysql.cj.callback.WebAuthnAuthenticationCallback;

public class AuthenticationWebAuthnCallbackHandler implements MysqlCallbackHandler {
    @Override
    public void handle(MysqlCallback cb) {
        if (!WebAuthnAuthenticationCallback.class.isAssignableFrom(cb.getClass())) {
            return;
        }

        WebAuthnAuthenticationCallback webAuthnAuthCallback = (WebAuthnAuthenticationCallback) cb;

        FidoAssertion libFido2Assertion = new FidoAssertion();
        webAuthnAuthCallback.setSupportsCredentialManagement(libFido2Assertion.supportsCredentialManagement());

        libFido2Assertion.setClienDataHash(webAuthnAuthCallback.getClientDataHash());
        libFido2Assertion.setRelyingPartyId(webAuthnAuthCallback.getRelyingPartyId());
        libFido2Assertion.setCredentialId(webAuthnAuthCallback.getCredentialId());

        System.out.println("Please perform the gesture action on your FIDO device.");
        libFido2Assertion.computeAssertions();

        for (int i = 0; i < libFido2Assertion.getAssertCount(); i++) {
            webAuthnAuthCallback.addAuthenticatorData(libFido2Assertion.getAuthenticatorData(i));
            webAuthnAuthCallback.addSignature(libFido2Assertion.getSignature(i));
        }

        libFido2Assertion.freeResources();
    }
}

Notice how this implementation is responsible for asking the user to perform the gesture action. In a real use case, this would eventually trigger an event that would, for example, open a pop-up message to the user.

Compile this code:

$ javac -classpath *:.  AuthenticationWebAuthnCallbackHandler.java

The name of this class must be supplied to Connector/J through the connection property authenticationWebAuthnCallbackHandler.

Implement the Application

Implement the client application. The following implementation is just a proof of concept that creates a MySQL connection to the MySQL server with the user created earlier and checks if the connection was established successfully. Notice that FIDO authentication requires some sort of human interactions, so this is not a solution to apply for a typical three-tier architecture, where there is usually a single database user configured in the application server and connections to the database are established from a remote machine.

Here is a simple client application code:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.util.Properties;

import com.mysql.cj.conf.PropertyKey;

public class AuthenticationWebAuthnApp {
    private static final String HOST = "localhost";
    private static final String PORT = "3306";
    private static final String USER = "johndoe";
    private static final String PASS = "s3cr3t";

    public static void main(String[] args) throws Exception {
        Properties props = new Properties();
        props.setProperty(PropertyKey.authenticationWebAuthnCallbackHandler.getKeyName(), AuthenticationWebAuthnCallbackHandler.class.getName());

        String url = "jdbc:mysql://" + USER + ":" + PASS + "@" + HOST + ":" + PORT + "/";

        try (Connection conn = DriverManager.getConnection(url, props)) {
            ResultSet rs = conn.createStatement().executeQuery("SELECT CURRENT_USER()");
            rs.next();
            System.out.println(rs.getString(1) + " AUTHENTICATED SUCCESSFULLY!");
        }
    }
}

Compile the code:

$ javac -classpath *:.  AuthenticationWebAuthnApp.java

Run the code:

$ /usr/lib/jvm/jdk-17/bin/java -classpath *:. AuthenticationWebAuthnApp 
Please perform the gesture action on your FIDO device.
johndoe@% AUTHENTICATED SUCCESSFULLY!