com.google.firebase.auth.internal.FirebaseTokenFactory Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of firebase-admin Show documentation
This is the official Firebase Admin Java SDK. Build extraordinary native JVM apps in minutes with Firebase. The Firebase platform can power your app’s backend, user authentication, static hosting, and more.
The newest version!
/*
 * Copyright 2017 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.firebase.auth.internal;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.api.client.json.GenericJson;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.webtoken.JsonWebSignature;
import com.google.api.client.util.Base64;
import com.google.api.client.util.Clock;
import com.google.api.client.util.StringUtils;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Strings;
import com.google.firebase.auth.FirebaseAuthException;
import com.google.firebase.internal.Nullable;

import java.io.IOException;
import java.util.Collection;
import java.util.Map;

/**
 * Provides helper methods to simplify the creation of Firebase custom auth tokens.
 *
 * This class is designed to hide underlying implementation details from a Firebase developer.
 */
public class FirebaseTokenFactory {

  private final JsonFactory jsonFactory;
  private final Clock clock;
  private final CryptoSigner signer;
  private final String tenantId;

  public FirebaseTokenFactory(
      JsonFactory jsonFactory, Clock clock, CryptoSigner signer, @Nullable String tenantId) {
    this.jsonFactory = checkNotNull(jsonFactory);
    this.clock = checkNotNull(clock);
    this.signer = checkNotNull(signer);
    this.tenantId = tenantId;
  }

  @VisibleForTesting
  FirebaseTokenFactory(JsonFactory jsonFactory, Clock clock, CryptoSigner signer) {
    this(jsonFactory, clock, signer, null);
  }

  String createSignedCustomAuthTokenForUser(String uid) throws FirebaseAuthException {
    return createSignedCustomAuthTokenForUser(uid, null);
  }

  public String createSignedCustomAuthTokenForUser(
      String uid, Map developerClaims) throws FirebaseAuthException {
    checkArgument(!Strings.isNullOrEmpty(uid), "Uid must be provided.");
    checkArgument(uid.length() <= 128, "Uid must be shorter than 128 characters.");

    JsonWebSignature.Header header = new JsonWebSignature.Header().setAlgorithm("RS256");

    final long issuedAt = clock.currentTimeMillis() / 1000;
    FirebaseCustomAuthToken.Payload payload =
        new FirebaseCustomAuthToken.Payload()
            .setUid(uid)
            .setIssuer(signer.getAccount())
            .setSubject(signer.getAccount())
            .setAudience(FirebaseCustomAuthToken.FIREBASE_AUDIENCE)
            .setIssuedAtTimeSeconds(issuedAt)
            .setExpirationTimeSeconds(issuedAt + FirebaseCustomAuthToken.TOKEN_DURATION_SECONDS);
    if (!Strings.isNullOrEmpty(tenantId)) {
      payload.setTenantId(tenantId);
    }

    if (developerClaims != null) {
      Collection reservedNames = payload.getClassInfo().getNames();
      for (String key : developerClaims.keySet()) {
        if (reservedNames.contains(key)) {
          throw new IllegalArgumentException(
              String.format("developerClaims must not contain a reserved key: %s", key));
        }
      }

      GenericJson jsonObject = new GenericJson();
      jsonObject.putAll(developerClaims);
      payload.setDeveloperClaims(jsonObject);
    }

    return signPayload(header, payload);
  }

  private String signPayload(
      JsonWebSignature.Header header,
      FirebaseCustomAuthToken.Payload payload) throws FirebaseAuthException {
    String content = encodePayload(header, payload);
    byte[] contentBytes = StringUtils.getBytesUtf8(content);
    String signature = Base64.encodeBase64URLSafeString(signer.sign(contentBytes));
    return content + "." + signature;
  }

  private String encodePayload(
      JsonWebSignature.Header header, FirebaseCustomAuthToken.Payload payload) {
    try {
      String headerString = Base64.encodeBase64URLSafeString(jsonFactory.toByteArray(header));
      String payloadString = Base64.encodeBase64URLSafeString(jsonFactory.toByteArray(payload));
      return headerString + "." + payloadString;
    } catch (IOException e) {
      throw new IllegalArgumentException(
          "Failed to encode JWT with the given claims: " + e.getMessage(), e);
    }
  }
}