Make the session id not depend on fetching the fid

Author: mrober

firebase-crashlytics/src/androidTest/java/com/google/firebase/crashlytics/internal/common/IdManagerTest.java

@@ -14,6 +14,7 @@
 
 package com.google.firebase.crashlytics.internal.common;
 
+import static com.google.common.truth.Truth.assertThat;
 import static com.google.firebase.crashlytics.internal.common.DataCollectionArbiterTest.MOCK_ARBITER_DISABLED;
 import static com.google.firebase.crashlytics.internal.common.DataCollectionArbiterTest.MOCK_ARBITER_ENABLED;
 import static org.mockito.Mockito.mock;
@@ -209,4 +210,32 @@ public void testInstanceIdRotatesWithDataCollectionFlag() {
     cachedFid = prefs.getString(IdManager.PREFKEY_FIREBASE_IID, null);
     assertEquals(cachedFid, originalFid);
   }
+
+  public void testIdForEntropy() {
+    prefs.edit().putString(IdManager.PREFKEY_INSTALLATION_UUID, "Seveneves").apply();
+    IdManager idManager = createIdManager(null, MOCK_ARBITER_ENABLED);
+
+    assertThat(idManager.getIdForEntropy()).isEqualTo(CommonUtils.sha1("Seveneves"));
+  }
+
+  public void testIdForEntropy_arbiterDisabled() {
+    prefs.edit().putString(IdManager.PREFKEY_INSTALLATION_UUID, "Seveneves").apply();
+    IdManager idManager = createIdManager(null, MOCK_ARBITER_DISABLED);
+
+    // Don't use the Crashlytics id, since data collection is disabled.
+    assertThat(idManager.getIdForEntropy()).isNotEqualTo(CommonUtils.sha1("Seveneves"));
+    assertThat(idManager.getIdForEntropy()).hasLength(32); // Length of random uuid.
+  }
+
+  public void testIdForEntropy_arbiterDisabled_syntheticFid() {
+    prefs
+        .edit()
+        .putString(IdManager.PREFKEY_INSTALLATION_UUID, "Seveneves")
+        .putString(IdManager.PREFKEY_FIREBASE_IID, "SYN_") // Synthetic fid
+        .apply();
+    IdManager idManager = createIdManager(null, MOCK_ARBITER_ENABLED);
+
+    // Do use the cached Crashlytics id, since the cached fid is synthetic.
+    assertThat(idManager.getIdForEntropy()).isEqualTo(CommonUtils.sha1("Seveneves"));
+  }
 }

firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/internal/common/CLSUUID.java

@@ -40,9 +40,7 @@ class CLSUUID {
     this.populateSequenceNumber(bytes);
     this.populatePID(bytes);
 
-    // sha1 it to ensure the string is long enough, has only valid hex characters, and to
-    // increase entropy.
-    final String idSha = CommonUtils.sha1(idManager.getInstallIds().getCrashlyticsInstallId());
+    final String idSha = idManager.getIdForEntropy();
     final String timeSeqPid = CommonUtils.hexify(bytes);
 
     _clsId =

firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/internal/common/IdManager.java

@@ -55,6 +55,9 @@ public class IdManager implements InstallIdProvider {
   // Stores a Crashlytics-specific install id, and Firebase installation id.
   private InstallIds installIds;
 
+  /** Stores a hash of an arbitrary id, for use in increasing entropy in session ids. */
+  private String idForEntropy;
+
   /**
    * @param appContext Application {@link Context}
    * @param appIdentifier the value to return as the App identifier (usually a package name), must
@@ -148,6 +151,29 @@ public synchronized InstallIds getInstallIds() {
     return installIds;
   }
 
+  /** Returns a hash of an arbitrary id, for use in increasing entropy in session ids. */
+  synchronized String getIdForEntropy() {
+    if (idForEntropy != null) {
+      return idForEntropy;
+    }
+
+    SharedPreferences prefs = CommonUtils.getSharedPrefs(appContext);
+    String cachedFid = prefs.getString(PREFKEY_FIREBASE_IID, null);
+    String cachedUuid = prefs.getString(PREFKEY_INSTALLATION_UUID, null);
+
+    // If the fid is synthetic, or data collection is enabled, use the cached uuid.
+    // The cached uuid is good enough, even if it's not current, to create enough entropy.
+    if ((isSyntheticFid(cachedFid) || dataCollectionArbiter.isAutomaticDataCollectionEnabled())
+        && cachedUuid != null) {
+      idForEntropy = CommonUtils.sha1(cachedUuid);
+    } else {
+      // Otherwise, generate a new uuid just for this process.
+      idForEntropy = formatId(UUID.randomUUID().toString());
+    }
+
+    return idForEntropy;
+  }
+
   /**
    * Returns true if we have not cached an InstallIds, or should force refresh the fid.
    *
@@ -213,7 +239,9 @@ private synchronized String createAndCacheCrashlyticsInstallId(
     return iid;
   }
 
-  /** @return the package name that identifies this App. */
+  /**
+   * @return the package name that identifies this App.
+   */
   public String getAppIdentifier() {
     return appIdentifier;
   }