Adapt to underlying changes in the PBKDF2 implementation

We need to specify "PBKDF2WithHmacSHA1And8bit" now in order to get precisely
the same output as was previously generated with "PBKDF2WithHmacSHA1".  We
also now try both when it's ambiguous which was used to generate the archive
checksums.

Bug 12494407

Change-Id: I5443f31a5e13c24f44445768b6e9a6eea221ede6

1 files changed, 169 insertions, 84 deletions

diff --git a/services/backup/java/com/android/server/backup/BackupManagerService.java b/services/backup/java/com/android/server/backup/BackupManagerService.java
index 9277cce..1e7c18a 100644
--- a/services/backup/java/com/android/server/backup/BackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/BackupManagerService.java
@@ -83,7 +83,6 @@ import com.android.internal.backup.BackupConstants;
 import com.android.internal.backup.IBackupTransport;
 import com.android.internal.backup.IObbBackupService;
 import com.android.server.EventLogTags;
-import com.android.server.SystemService;
 import com.android.server.backup.PackageManagerBackupAgent.Metadata;
 
 import java.io.BufferedInputStream;
@@ -142,11 +141,16 @@ public class BackupManagerService extends IBackupManager.Stub {
     private static final boolean DEBUG = true;
     private static final boolean MORE_DEBUG = false;
 
+    // Historical and current algorithm names
+    static final String PBKDF_CURRENT = "PBKDF2WithHmacSHA1";
+    static final String PBKDF_FALLBACK = "PBKDF2WithHmacSHA1And8bit";
+
     // Name and current contents version of the full-backup manifest file
     static final String BACKUP_MANIFEST_FILENAME = "_manifest";
     static final int BACKUP_MANIFEST_VERSION = 1;
     static final String BACKUP_FILE_HEADER_MAGIC = "ANDROID BACKUP\n";
-    static final int BACKUP_FILE_VERSION = 1;
+    static final int BACKUP_FILE_VERSION = 2;
+    static final int BACKUP_PW_FILE_VERSION = 2;
     static final boolean COMPRESS_FULL_BACKUPS = true; // should be true in production
 
     static final String SHARED_BACKUP_AGENT_PACKAGE = "com.android.sharedstoragebackup";
@@ -452,6 +456,8 @@ public class BackupManagerService extends IBackupManager.Stub {
     private final SecureRandom mRng = new SecureRandom();
     private String mPasswordHash;
     private File mPasswordHashFile;
+    private int mPasswordVersion;
+    private File mPasswordVersionFile;
     private byte[] mPasswordSalt;
 
     // Configuration of PBKDF2 that we use for generating pw hashes and intermediate keys
@@ -812,6 +818,27 @@ public class BackupManagerService extends IBackupManager.Stub {
         }
         mDataDir = Environment.getDownloadCacheDirectory();
 
+        mPasswordVersion = 1;       // unless we hear otherwise
+        mPasswordVersionFile = new File(mBaseStateDir, "pwversion");
+        if (mPasswordVersionFile.exists()) {
+            FileInputStream fin = null;
+            DataInputStream in = null;
+            try {
+                fin = new FileInputStream(mPasswordVersionFile);
+                in = new DataInputStream(fin);
+                mPasswordVersion = in.readInt();
+            } catch (IOException e) {
+                Slog.e(TAG, "Unable to read backup pw version");
+            } finally {
+                try {
+                    if (in != null) in.close();
+                    if (fin != null) fin.close();
+                } catch (IOException e) {
+                    Slog.w(TAG, "Error closing pw version files");
+                }
+            }
+        }
+
         mPasswordHashFile = new File(mBaseStateDir, "pwhash");
         if (mPasswordHashFile.exists()) {
             FileInputStream fin = null;
@@ -1112,13 +1139,13 @@ public class BackupManagerService extends IBackupManager.Stub {
         }
     }
 
-    private SecretKey buildPasswordKey(String pw, byte[] salt, int rounds) {
-        return buildCharArrayKey(pw.toCharArray(), salt, rounds);
+    private SecretKey buildPasswordKey(String algorithm, String pw, byte[] salt, int rounds) {
+        return buildCharArrayKey(algorithm, pw.toCharArray(), salt, rounds);
     }
 
-    private SecretKey buildCharArrayKey(char[] pwArray, byte[] salt, int rounds) {
+    private SecretKey buildCharArrayKey(String algorithm, char[] pwArray, byte[] salt, int rounds) {
         try {
-            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
+            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(algorithm);
             KeySpec ks = new PBEKeySpec(pwArray, salt, rounds, PBKDF2_KEY_SIZE);
             return keyFactory.generateSecret(ks);
         } catch (InvalidKeySpecException e) {
@@ -1129,8 +1156,8 @@ public class BackupManagerService extends IBackupManager.Stub {
         return null;
     }
 
-    private String buildPasswordHash(String pw, byte[] salt, int rounds) {
-        SecretKey key = buildPasswordKey(pw, salt, rounds);
+    private String buildPasswordHash(String algorithm, String pw, byte[] salt, int rounds) {
+        SecretKey key = buildPasswordKey(algorithm, pw, salt, rounds);
         if (key != null) {
             return byteArrayToHex(key.getEncoded());
         }
@@ -1158,13 +1185,13 @@ public class BackupManagerService extends IBackupManager.Stub {
         return result;
     }
 
-    private byte[] makeKeyChecksum(byte[] pwBytes, byte[] salt, int rounds) {
+    private byte[] makeKeyChecksum(String algorithm, byte[] pwBytes, byte[] salt, int rounds) {
         char[] mkAsChar = new char[pwBytes.length];
         for (int i = 0; i < pwBytes.length; i++) {
             mkAsChar[i] = (char) pwBytes[i];
         }
 
-        Key checksum = buildCharArrayKey(mkAsChar, salt, rounds);
+        Key checksum = buildCharArrayKey(algorithm, mkAsChar, salt, rounds);
         return checksum.getEncoded();
     }
 
@@ -1176,7 +1203,7 @@ public class BackupManagerService extends IBackupManager.Stub {
     }
 
     // Backup password management
-    boolean passwordMatchesSaved(String candidatePw, int rounds) {
+    boolean passwordMatchesSaved(String algorithm, String candidatePw, int rounds) {
         // First, on an encrypted device we require matching the device pw
         final boolean isEncrypted;
         try {
@@ -1220,7 +1247,7 @@ public class BackupManagerService extends IBackupManager.Stub {
         } else {
             // hash the stated current pw and compare to the stored one
             if (candidatePw != null && candidatePw.length() > 0) {
-                String currentPwHash = buildPasswordHash(candidatePw, mPasswordSalt, rounds);
+                String currentPwHash = buildPasswordHash(algorithm, candidatePw, mPasswordSalt, rounds);
                 if (mPasswordHash.equalsIgnoreCase(currentPwHash)) {
                     // candidate hash matches the stored hash -- the password matches
                     return true;
@@ -1235,11 +1262,37 @@ public class BackupManagerService extends IBackupManager.Stub {
         mContext.enforceCallingOrSelfPermission(android.Manifest.permission.BACKUP,
                 "setBackupPassword");
 
-        // If the supplied pw doesn't hash to the the saved one, fail
-        if (!passwordMatchesSaved(currentPw, PBKDF2_HASH_ROUNDS)) {
+        // When processing v1 passwords we may need to try two different PBKDF2 checksum regimes
+        final boolean pbkdf2Fallback = (mPasswordVersion < BACKUP_PW_FILE_VERSION);
+
+        // If the supplied pw doesn't hash to the the saved one, fail.  The password
+        // might be caught in the legacy crypto mismatch; verify that too.
+        if (!passwordMatchesSaved(PBKDF_CURRENT, currentPw, PBKDF2_HASH_ROUNDS)
+                && !(pbkdf2Fallback && passwordMatchesSaved(PBKDF_FALLBACK,
+                        currentPw, PBKDF2_HASH_ROUNDS))) {
             return false;
         }
 
+        // Snap up to current on the pw file version
+        mPasswordVersion = BACKUP_PW_FILE_VERSION;
+        FileOutputStream pwFout = null;
+        DataOutputStream pwOut = null;
+        try {
+            pwFout = new FileOutputStream(mPasswordVersionFile);
+            pwOut = new DataOutputStream(pwFout);
+            pwOut.writeInt(mPasswordVersion);
+        } catch (IOException e) {
+            Slog.e(TAG, "Unable to write backup pw version; password not changed");
+            return false;
+        } finally {
+            try {
+                if (pwOut != null) pwOut.close();
+                if (pwFout != null) pwFout.close();
+            } catch (IOException e) {
+                Slog.w(TAG, "Unable to close pw version record");
+            }
+        }
+
         // Clearing the password is okay
         if (newPw == null || newPw.isEmpty()) {
             if (mPasswordHashFile.exists()) {
@@ -1257,7 +1310,7 @@ public class BackupManagerService extends IBackupManager.Stub {
         try {
             // Okay, build the hash of the new backup password
             byte[] salt = randomBytes(PBKDF2_SALT_SIZE);
-            String newPwHash = buildPasswordHash(newPw, salt, PBKDF2_HASH_ROUNDS);
+            String newPwHash = buildPasswordHash(PBKDF_CURRENT, newPw, salt, PBKDF2_HASH_ROUNDS);
 
             OutputStream pwf = null, buffer = null;
             DataOutputStream out = null;
@@ -1300,6 +1353,19 @@ public class BackupManagerService extends IBackupManager.Stub {
         }
     }
 
+    private boolean backupPasswordMatches(String currentPw) {
+        if (hasBackupPassword()) {
+            final boolean pbkdf2Fallback = (mPasswordVersion < BACKUP_PW_FILE_VERSION);
+            if (!passwordMatchesSaved(PBKDF_CURRENT, currentPw, PBKDF2_HASH_ROUNDS)
+                    && !(pbkdf2Fallback && passwordMatchesSaved(PBKDF_FALLBACK,
+                            currentPw, PBKDF2_HASH_ROUNDS))) {
+                if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");
+                return false;
+            }
+        }
+        return true;
+    }
+
     // Maintain persistent state around whether need to do an initialize operation.
     // Must be called with the queue lock held.
     void recordInitPendingLocked(boolean isPending, String transportName) {
@@ -2721,11 +2787,9 @@ public class BackupManagerService extends IBackupManager.Stub {
 
                 // Verify that the given password matches the currently-active
                 // backup password, if any
-                if (hasBackupPassword()) {
-                    if (!passwordMatchesSaved(mCurrentPassword, PBKDF2_HASH_ROUNDS)) {
-                        if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");
-                        return;
-                    }
+                if (!backupPasswordMatches(mCurrentPassword)) {
+                    if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");
+                    return;
                 }
 
                 // Write the global file header.  All strings are UTF-8 encoded; lines end
@@ -2733,7 +2797,7 @@ public class BackupManagerService extends IBackupManager.Stub {
                 // final '\n'.
                 //
                 // line 1: "ANDROID BACKUP"
-                // line 2: backup file format version, currently "1"
+                // line 2: backup file format version, currently "2"
                 // line 3: compressed?  "0" if not compressed, "1" if compressed.
                 // line 4: name of encryption algorithm [currently only "none" or "AES-256"]
                 //
@@ -2841,7 +2905,7 @@ public class BackupManagerService extends IBackupManager.Stub {
                 OutputStream ofstream) throws Exception {
             // User key will be used to encrypt the master key.
             byte[] newUserSalt = randomBytes(PBKDF2_SALT_SIZE);
-            SecretKey userKey = buildPasswordKey(mEncryptPassword, newUserSalt,
+            SecretKey userKey = buildPasswordKey(PBKDF_CURRENT, mEncryptPassword, newUserSalt,
                     PBKDF2_HASH_ROUNDS);
 
             // the master key is random for each backup
@@ -2888,7 +2952,7 @@ public class BackupManagerService extends IBackupManager.Stub {
             // stated number of PBKDF2 rounds
             IV = c.getIV();
             byte[] mk = masterKeySpec.getEncoded();
-            byte[] checksum = makeKeyChecksum(masterKeySpec.getEncoded(),
+            byte[] checksum = makeKeyChecksum(PBKDF_CURRENT, masterKeySpec.getEncoded(),
                     checksumSalt, PBKDF2_HASH_ROUNDS);
 
             ByteArrayOutputStream blob = new ByteArrayOutputStream(IV.length + mk.length
@@ -3231,11 +3295,9 @@ public class BackupManagerService extends IBackupManager.Stub {
             FileInputStream rawInStream = null;
             DataInputStream rawDataIn = null;
             try {
-                if (hasBackupPassword()) {
-                    if (!passwordMatchesSaved(mCurrentPassword, PBKDF2_HASH_ROUNDS)) {
-                        if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");
-                        return;
-                    }
+                if (!backupPasswordMatches(mCurrentPassword)) {
+                    if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");
+                    return;
                 }
 
                 mBytes = 0;
@@ -3256,8 +3318,12 @@ public class BackupManagerService extends IBackupManager.Stub {
                 if (Arrays.equals(magicBytes, streamHeader)) {
                     // okay, header looks good.  now parse out the rest of the fields.
                     String s = readHeaderLine(rawInStream);
-                    if (Integer.parseInt(s) == BACKUP_FILE_VERSION) {
-                        // okay, it's a version we recognize
+                    final int archiveVersion = Integer.parseInt(s);
+                    if (archiveVersion <= BACKUP_FILE_VERSION) {
+                        // okay, it's a version we recognize.  if it's version 1, we may need
+                        // to try two different PBKDF2 regimes to compare checksums.
+                        final boolean pbkdf2Fallback = (archiveVersion == 1);
+
                         s = readHeaderLine(rawInStream);
                         compressed = (Integer.parseInt(s) != 0);
                         s = readHeaderLine(rawInStream);
@@ -3265,7 +3331,8 @@ public class BackupManagerService extends IBackupManager.Stub {
                             // no more header to parse; we're good to go
                             okay = true;
                         } else if (mDecryptPassword != null && mDecryptPassword.length() > 0) {
-                            preCompressStream = decodeAesHeaderAndInitialize(s, rawInStream);
+                            preCompressStream = decodeAesHeaderAndInitialize(s, pbkdf2Fallback,
+                                    rawInStream);
                             if (preCompressStream != null) {
                                 okay = true;
                             }
@@ -3325,7 +3392,71 @@ public class BackupManagerService extends IBackupManager.Stub {
             return buffer.toString();
         }
 
-        InputStream decodeAesHeaderAndInitialize(String encryptionName, InputStream rawInStream) {
+        InputStream attemptMasterKeyDecryption(String algorithm, byte[] userSalt, byte[] ckSalt,
+                int rounds, String userIvHex, String masterKeyBlobHex, InputStream rawInStream,
+                boolean doLog) {
+            InputStream result = null;
+
+            try {
+                Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
+                SecretKey userKey = buildPasswordKey(algorithm, mDecryptPassword, userSalt,
+                        rounds);
+                byte[] IV = hexToByteArray(userIvHex);
+                IvParameterSpec ivSpec = new IvParameterSpec(IV);
+                c.init(Cipher.DECRYPT_MODE,
+                        new SecretKeySpec(userKey.getEncoded(), "AES"),
+                        ivSpec);
+                byte[] mkCipher = hexToByteArray(masterKeyBlobHex);
+                byte[] mkBlob = c.doFinal(mkCipher);
+
+                // first, the master key IV
+                int offset = 0;
+                int len = mkBlob[offset++];
+                IV = Arrays.copyOfRange(mkBlob, offset, offset + len);
+                offset += len;
+                // then the master key itself
+                len = mkBlob[offset++];
+                byte[] mk = Arrays.copyOfRange(mkBlob,
+                        offset, offset + len);
+                offset += len;
+                // and finally the master key checksum hash
+                len = mkBlob[offset++];
+                byte[] mkChecksum = Arrays.copyOfRange(mkBlob,
+                        offset, offset + len);
+
+                // now validate the decrypted master key against the checksum
+                byte[] calculatedCk = makeKeyChecksum(algorithm, mk, ckSalt, rounds);
+                if (Arrays.equals(calculatedCk, mkChecksum)) {
+                    ivSpec = new IvParameterSpec(IV);
+                    c.init(Cipher.DECRYPT_MODE,
+                            new SecretKeySpec(mk, "AES"),
+                            ivSpec);
+                    // Only if all of the above worked properly will 'result' be assigned
+                    result = new CipherInputStream(rawInStream, c);
+                } else if (doLog) Slog.w(TAG, "Incorrect password");
+            } catch (InvalidAlgorithmParameterException e) {
+                if (doLog) Slog.e(TAG, "Needed parameter spec unavailable!", e);
+            } catch (BadPaddingException e) {
+                // This case frequently occurs when the wrong password is used to decrypt
+                // the master key.  Use the identical "incorrect password" log text as is
+                // used in the checksum failure log in order to avoid providing additional
+                // information to an attacker.
+                if (doLog) Slog.w(TAG, "Incorrect password");
+            } catch (IllegalBlockSizeException e) {
+                if (doLog) Slog.w(TAG, "Invalid block size in master key");
+            } catch (NoSuchAlgorithmException e) {
+                if (doLog) Slog.e(TAG, "Needed decryption algorithm unavailable!");
+            } catch (NoSuchPaddingException e) {
+                if (doLog) Slog.e(TAG, "Needed padding mechanism unavailable!");
+            } catch (InvalidKeyException e) {
+                if (doLog) Slog.w(TAG, "Illegal password; aborting");
+            }
+
+            return result;
+        }
+
+        InputStream decodeAesHeaderAndInitialize(String encryptionName, boolean pbkdf2Fallback,
+                InputStream rawInStream) {
             InputStream result = null;
             try {
                 if (encryptionName.equals(ENCRYPTION_ALGORITHM_NAME)) {
@@ -3342,59 +3473,13 @@ public class BackupManagerService extends IBackupManager.Stub {
                     String masterKeyBlobHex = readHeaderLine(rawInStream); // 9
 
                     // decrypt the master key blob
-                    Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
-                    SecretKey userKey = buildPasswordKey(mDecryptPassword, userSalt,
-                            rounds);
-                    byte[] IV = hexToByteArray(userIvHex);
-                    IvParameterSpec ivSpec = new IvParameterSpec(IV);
-                    c.init(Cipher.DECRYPT_MODE,
-                            new SecretKeySpec(userKey.getEncoded(), "AES"),
-                            ivSpec);
-                    byte[] mkCipher = hexToByteArray(masterKeyBlobHex);
-                    byte[] mkBlob = c.doFinal(mkCipher);
-
-                    // first, the master key IV
-                    int offset = 0;
-                    int len = mkBlob[offset++];
-                    IV = Arrays.copyOfRange(mkBlob, offset, offset + len);
-                    offset += len;
-                    // then the master key itself
-                    len = mkBlob[offset++];
-                    byte[] mk = Arrays.copyOfRange(mkBlob,
-                            offset, offset + len);
-                    offset += len;
-                    // and finally the master key checksum hash
-                    len = mkBlob[offset++];
-                    byte[] mkChecksum = Arrays.copyOfRange(mkBlob,
-                            offset, offset + len);
-
-                    // now validate the decrypted master key against the checksum
-                    byte[] calculatedCk = makeKeyChecksum(mk, ckSalt, rounds);
-                    if (Arrays.equals(calculatedCk, mkChecksum)) {
-                        ivSpec = new IvParameterSpec(IV);
-                        c.init(Cipher.DECRYPT_MODE,
-                                new SecretKeySpec(mk, "AES"),
-                                ivSpec);
-                        // Only if all of the above worked properly will 'result' be assigned
-                        result = new CipherInputStream(rawInStream, c);
-                    } else Slog.w(TAG, "Incorrect password");
+                    result = attemptMasterKeyDecryption(PBKDF_CURRENT, userSalt, ckSalt,
+                            rounds, userIvHex, masterKeyBlobHex, rawInStream, false);
+                    if (result == null && pbkdf2Fallback) {
+                        result = attemptMasterKeyDecryption(PBKDF_FALLBACK, userSalt, ckSalt,
+                                rounds, userIvHex, masterKeyBlobHex, rawInStream, true);
+                    }
                 } else Slog.w(TAG, "Unsupported encryption method: " + encryptionName);
-            } catch (InvalidAlgorithmParameterException e) {
-                Slog.e(TAG, "Needed parameter spec unavailable!", e);
-            } catch (BadPaddingException e) {
-                // This case frequently occurs when the wrong password is used to decrypt
-                // the master key.  Use the identical "incorrect password" log text as is
-                // used in the checksum failure log in order to avoid providing additional
-                // information to an attacker.
-                Slog.w(TAG, "Incorrect password");
-            } catch (IllegalBlockSizeException e) {
-                Slog.w(TAG, "Invalid block size in master key");
-            } catch (NoSuchAlgorithmException e) {
-                Slog.e(TAG, "Needed decryption algorithm unavailable!");
-            } catch (NoSuchPaddingException e) {
-                Slog.e(TAG, "Needed padding mechanism unavailable!");
-            } catch (InvalidKeyException e) {
-                Slog.w(TAG, "Illegal password; aborting");
             } catch (NumberFormatException e) {
                 Slog.w(TAG, "Can't parse restore data header");
             } catch (IOException e) {