Add support for credProtect extension

NEWS

@@ -1,5 +1,6 @@
 == Version 2.7.0 (unreleased) ==
 
+* Added support for the CTAP2 `credProtect` extension.
 * (Experimental) Added a new suite of interfaces, starting with
   `CredentialRepositoryV2`. `RelyingParty` can now be configured with a
   `CredentialRepositoryV2` instance instead of a `CredentialRepository`

webauthn-server-core/src/main/java/com/yubico/webauthn/FinishRegistrationSteps.java

@@ -39,6 +39,7 @@
 import com.yubico.webauthn.data.ByteArray;
 import com.yubico.webauthn.data.ClientRegistrationExtensionOutputs;
 import com.yubico.webauthn.data.CollectedClientData;
+import com.yubico.webauthn.data.Extensions;
 import com.yubico.webauthn.data.PublicKeyCredential;
 import com.yubico.webauthn.data.PublicKeyCredentialCreationOptions;
 import com.yubico.webauthn.data.PublicKeyCredentialParameters;
@@ -337,7 +338,7 @@ public Step16 nextStep() {
   }
 
   @Value
-  class Step16 implements Step<Step18> {
+  class Step16 implements Step<Step17> {
     private final ByteArray clientDataJsonHash;
     private final AttestationObject attestation;
 
@@ -368,14 +369,28 @@ public void validate() {
       }
     }
 
+    @Override
+    public Step17 nextStep() {
+      return new Step17(clientDataJsonHash, attestation);
+    }
+  }
+
+  @Value
+  class Step17 implements Step<Step18> {
+    private final ByteArray clientDataJsonHash;
+    private final AttestationObject attestation;
+
+    @Override
+    public void validate() {
+      Extensions.CredentialProtection.validateExtensionOutput(request, response);
+    }
+
     @Override
     public Step18 nextStep() {
       return new Step18(clientDataJsonHash, attestation);
     }
   }
 
-  // Nothing to do for step 17
-
   @Value
   class Step18 implements Step<Step19> {
     private final ByteArray clientDataJsonHash;

webauthn-server-core/src/main/java/com/yubico/webauthn/RegistrationResult.java

@@ -39,8 +39,10 @@
 import com.yubico.webauthn.data.AuthenticatorResponse;
 import com.yubico.webauthn.data.ByteArray;
 import com.yubico.webauthn.data.ClientRegistrationExtensionOutputs;
+import com.yubico.webauthn.data.Extensions;
 import com.yubico.webauthn.data.PublicKeyCredential;
 import com.yubico.webauthn.data.PublicKeyCredentialDescriptor;
+import com.yubico.webauthn.data.RegistrationExtensionInputs;
 import java.io.IOException;
 import java.security.NoSuchAlgorithmException;
 import java.security.PublicKey;
@@ -367,6 +369,40 @@ public Optional<Boolean> isDiscoverable() {
         .flatMap(credProps -> credProps.getRk());
   }
 
+  /**
+   * Retrieve the <code>credProtect</code> extension policy that was set for the credential, if
+   * available.
+   *
+   * <p>If accessing this, you most likely also want to set the {@link
+   * RegistrationExtensionInputs.RegistrationExtensionInputsBuilder#credProtect(Extensions.CredentialProtection.CredentialProtectionInput)
+   * credProtect} extension input in the {@link
+   * StartRegistrationOptions.StartRegistrationOptionsBuilder#extensions(RegistrationExtensionInputs)
+   * extensions} parameter of {@link StartRegistrationOptions}.
+   *
+   * <p>This output is signed by the authenticator, and thus its trustworthiness may be evaluated
+   * using <a
+   * href="https://developers.yubico.com/java-webauthn-server/#using_attestation">authenticator
+   * attestation</a>.
+   *
+   * @return the <code>credProtect</code> extension policy that was set for the credential, if
+   *     available.
+   * @see
+   *     StartRegistrationOptions.StartRegistrationOptionsBuilder#extensions(RegistrationExtensionInputs)
+   * @see
+   *     RegistrationExtensionInputs.RegistrationExtensionInputsBuilder#credProtect(Extensions.CredentialProtection.CredentialProtectionInput)
+   * @see <a
+   *     href="https://fidoalliance.org/specs/fido-v2.1-ps-20210615/fido-client-to-authenticator-protocol-v2.1-ps-20210615.html#sctn-credProtect-extension">CTAP2
+   *     §12.1. Credential Protection (credProtect)</a>
+   * @see <a href="https://developers.yubico.com/java-webauthn-server/#using_attestation">Using
+   *     attestation</a>
+   */
+  @JsonIgnore
+  public Optional<Extensions.CredentialProtection.CredentialProtectionPolicy>
+      getCredProtectPolicy() {
+    return getAuthenticatorExtensionOutputs()
+        .flatMap(AuthenticatorRegistrationExtensionOutputs::getCredProtect);
+  }
+
   /**
    * The <a
    * href="https://www.w3.org/TR/2021/REC-webauthn-2-20210408/#attestation-trust-path">attestation

webauthn-server-core/src/main/java/com/yubico/webauthn/data/AuthenticatorRegistrationExtensionOutputs.java

@@ -61,11 +61,15 @@
 public final class AuthenticatorRegistrationExtensionOutputs
     implements AuthenticatorExtensionOutputs {
 
+  private final Extensions.CredentialProtection.CredentialProtectionPolicy credProtect;
   private final List<Extensions.Uvm.UvmEntry> uvm;
 
   @JsonCreator
   private AuthenticatorRegistrationExtensionOutputs(
+      @JsonProperty("credProtect")
+          Extensions.CredentialProtection.CredentialProtectionPolicy credProtect,
       @JsonProperty("uvm") List<Extensions.Uvm.UvmEntry> uvm) {
+    this.credProtect = credProtect;
     this.uvm = uvm == null ? null : CollectionUtil.immutableList(uvm);
   }
 
@@ -107,6 +111,8 @@ public static Optional<AuthenticatorRegistrationExtensionOutputs> fromAuthentica
   static Optional<AuthenticatorRegistrationExtensionOutputs> fromCbor(CBORObject cbor) {
     AuthenticatorRegistrationExtensionOutputsBuilder b = builder();
 
+    Extensions.CredentialProtection.parseAuthenticatorExtensionOutput(cbor)
+        .ifPresent(b::credProtect);
     Extensions.Uvm.parseAuthenticatorExtensionOutput(cbor).ifPresent(b::uvm);
 
     AuthenticatorRegistrationExtensionOutputs result = b.build();
@@ -122,12 +128,30 @@ static Optional<AuthenticatorRegistrationExtensionOutputs> fromCbor(CBORObject c
   @EqualsAndHashCode.Include
   public Set<String> getExtensionIds() {
     HashSet<String> ids = new HashSet<>();
+    if (credProtect != null) {
+      ids.add(Extensions.CredentialProtection.EXTENSION_ID);
+    }
     if (uvm != null) {
       ids.add(Extensions.Uvm.EXTENSION_ID);
     }
     return ids;
   }
 
+  /**
+   * @return The <a
+   *     href="https://www.w3.org/TR/2021/REC-webauthn-2-20210408/#authenticator-extension-output">authenticator
+   *     extension output</a> for the <a
+   *     href="https://fidoalliance.org/specs/fido-v2.1-ps-20210615/fido-client-to-authenticator-protocol-v2.1-ps-20210615.html#sctn-credProtect-extension">Credential
+   *     Protection (credProtect) extension</a>, if any. This indicates the credential protection
+   *     policy that was set for the credential.
+   * @see <a
+   *     href="https://fidoalliance.org/specs/fido-v2.1-ps-20210615/fido-client-to-authenticator-protocol-v2.1-ps-20210615.html#sctn-credProtect-extension">CTAP2
+   *     §12.1. Credential Protection (credProtect)</a>
+   */
+  public Optional<Extensions.CredentialProtection.CredentialProtectionPolicy> getCredProtect() {
+    return Optional.ofNullable(credProtect);
+  }
+
   /**
    * @return The <a
    *     href="https://www.w3.org/TR/2021/REC-webauthn-2-20210408/#authenticator-extension-output">authenticator