am d2a0d233: Use consistent device-id even the device is wiped.

Merge commit 'd2a0d23380a2751d82f9d1f955a812f94a301e2a' into froyo-plus-aosp

* commit 'd2a0d23380a2751d82f9d1f955a812f94a301e2a':
  Use consistent device-id even the device is wiped.

src/com/android/email/Utility.java

@@ -32,8 +32,11 @@ import android.content.res.TypedArray;
 import android.database.Cursor;
 import android.graphics.drawable.Drawable;
 import android.os.AsyncTask;
+import android.security.MessageDigest;
+import android.telephony.TelephonyManager;
 import android.text.Editable;
 import android.util.Base64;
+import android.util.Log;
 import android.widget.TextView;
 
 import java.io.IOException;
@@ -43,6 +46,7 @@ import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.charset.Charset;
+import java.security.NoSuchAlgorithmException;
 import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
@@ -527,4 +531,45 @@ public class Utility {
             task.cancel(mayInterruptIfRunning);
         }
     }
+
+    /**
+     * @return Device's unique ID if available.  null if the device has no unique ID.
+     */
+    public static String getConsistentDeviceId(Context context) {
+        final String deviceId;
+        try {
+            TelephonyManager tm =
+                    (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
+            if (tm == null) {
+                return null;
+            }
+            deviceId = tm.getDeviceId();
+            if (deviceId == null) {
+                return null;
+            }
+        } catch (Exception e) {
+            Log.d(Email.LOG_TAG, "Error in TelephonyManager.getDeviceId(): " + e.getMessage());
+            return null;
+        }
+        final MessageDigest sha;
+        try {
+            sha = MessageDigest.getInstance("SHA-1");
+        } catch (NoSuchAlgorithmException impossible) {
+            return null;
+        }
+        sha.update(Utility.toUtf8(deviceId));
+        final int hash = getSmallHashFromSha1(sha.digest());
+        return Integer.toString(hash);
+    }
+
+    /**
+     * @return a non-negative integer generated from 20 byte SHA-1 hash.
+     */
+    /* package for testing */ static int getSmallHashFromSha1(byte[] sha1) {
+        final int offset = sha1[19] & 0xf; // SHA1 is 20 bytes.
+        return ((sha1[offset]  & 0x7f) << 24)
+                | ((sha1[offset + 1] & 0xff) << 16)
+                | ((sha1[offset + 2] & 0xff) << 8)
+                | ((sha1[offset + 3] & 0xff));
+    }
 }

src/com/android/exchange/SyncManager.java

@@ -20,6 +20,7 @@ package com.android.exchange;
 import com.android.email.AccountBackupRestore;
 import com.android.email.Email;
 import com.android.email.SecurityPolicy;
+import com.android.email.Utility;
 import com.android.email.mail.MessagingException;
 import com.android.email.mail.transport.SSLUtils;
 import com.android.email.provider.EmailContent;
@@ -968,16 +969,19 @@ public class SyncManager extends Service implements Runnable {
     }
 
     static public synchronized String getDeviceId(Context context) throws IOException {
-        SyncManager syncManager = INSTANCE;
-        if (sDeviceId != null) {
-            return sDeviceId;
-        } else if (syncManager == null && context == null) {
+        if (sDeviceId == null) {
+            sDeviceId = getDeviceIdInternal(context);
+        }
+        return sDeviceId;
+    }
+
+    static private String getDeviceIdInternal(Context context) throws IOException {
+        if (INSTANCE == null && context == null) {
             throw new IOException("No context for getDeviceId");
         } else if (context == null) {
-            context = syncManager;
+            context = INSTANCE;
         }
 
-        // Otherwise, we'll read the id file or create one if it's not found
         try {
             File f = context.getFileStreamPath("deviceName");
             BufferedReader rdr = null;
@@ -986,14 +990,18 @@ public class SyncManager extends Service implements Runnable {
                 rdr = new BufferedReader(new FileReader(f), 128);
                 id = rdr.readLine();
                 rdr.close();
-                sDeviceId = id;
                 return id;
             } else if (f.createNewFile()) {
                 BufferedWriter w = new BufferedWriter(new FileWriter(f), 128);
-                id = "android" + System.currentTimeMillis();
+                final String consistentDeviceId = Utility.getConsistentDeviceId(context);
+                if (consistentDeviceId != null) {
+                    // Use different prefix from random IDs.
+                    id = "androidc" + consistentDeviceId;
+                } else {
+                    id = "android" + System.currentTimeMillis();
+                }
                 w.write(id);
                 w.close();
-                sDeviceId = id;
                 return id;
             }
         } catch (IOException e) {

tests/src/com/android/email/UtilityUnitTests.java

@@ -20,9 +20,11 @@ import com.android.email.provider.EmailContent.Mailbox;
 
 import android.content.Context;
 import android.graphics.drawable.Drawable;
+import android.telephony.TelephonyManager;
 import android.test.AndroidTestCase;
 import android.test.MoreAsserts;
 import android.test.suitebuilder.annotation.SmallTest;
+import android.util.Log;
 
 import java.util.HashSet;
 import java.util.Set;
@@ -170,4 +172,37 @@ public class UtilityUnitTests extends AndroidTestCase {
         assertEquals("\r\n\r\n\r\n", Utility.replaceBareLfWithCrlf("\n\n\n"));
         assertEquals("A\r\nB\r\nC\r\nD", Utility.replaceBareLfWithCrlf("A\nB\r\nC\nD"));
     }
+
+    public void testGetConsistentDeviceId() {
+        TelephonyManager tm =
+                (TelephonyManager) getContext().getSystemService(Context.TELEPHONY_SERVICE);
+        if (tm == null) {
+            Log.w(Email.LOG_TAG, "TelephonyManager not supported.  Skipping.");
+            return;
+        }
+        final String deviceId = Utility.getConsistentDeviceId(getContext());
+        assertNotNull(deviceId);
+
+        final String deviceId2 = Utility.getConsistentDeviceId(getContext());
+        // Should be consistent.
+        assertEquals(deviceId, deviceId2);
+    }
+
+    public void testGetSmallSha1() {
+        byte[] sha1 = new byte[20];
+
+        // White box test.  Not so great, but to make sure it may detect careless mistakes...
+        assertEquals(0, Utility.getSmallHashFromSha1(sha1));
+
+        for (int i = 0; i < sha1.length; i++) {
+            sha1[i] = (byte) 0xFF;
+        }
+        assertEquals(Integer.MAX_VALUE, Utility.getSmallHashFromSha1(sha1));
+
+        // Boundary check
+        for (int i = 0; i < 16; i++) {
+            sha1[19] = (byte) i;
+            Utility.getSmallHashFromSha1(sha1);
+        }
+    }
 }