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Commit 28c8cfd7 authored by Christopher Tate's avatar Christopher Tate
Browse files

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

Cherry-pick from master.

Change-Id: I2d6081dd62f50f7d493045150b327ed120de7abd
parent 4ef0aabe

services/java/com/android/server/BackupManagerService.java

+170 −84
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ import android.util.StringBuilderPrinter; 
import com.android.internal.backup.BackupConstants;

import com.android.internal.backup.IBackupTransport;

import com.android.internal.backup.IObbBackupService;

import com.android.internal.backup.LocalTransport;

import com.android.server.EventLogTags;

import com.android.server.PackageManagerBackupAgent.Metadata;



import java.io.BufferedInputStream;
@@ -140,11 +140,16 @@ 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";
@@ -450,6 +455,8 @@ 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
@@ -810,6 +817,27 @@ 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;
@@ -1110,13 +1138,13 @@ 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) {
@@ -1127,8 +1155,8 @@ 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());

        }
@@ -1156,13 +1184,13 @@ 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();

    }
@@ -1174,7 +1202,7 @@ 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 {
@@ -1217,7 +1245,7 @@ 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;
@@ -1232,9 +1260,35 @@ 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
@@ -1254,7 +1308,7 @@ 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;
@@ -1297,6 +1351,19 @@ 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) {
@@ -2717,19 +2784,17 @@ 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 (!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

                // with a '\n' byte.  Actual backup data begins immediately following the

                // 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"]

                //
@@ -2837,7 +2902,7 @@ 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
@@ -2884,7 +2949,7 @@ 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
@@ -3227,12 +3292,10 @@ class BackupManagerService extends IBackupManager.Stub { 
            FileInputStream rawInStream = null;

            DataInputStream rawDataIn = null;

            try {

                if (hasBackupPassword()) {

                    if (!passwordMatchesSaved(mCurrentPassword, PBKDF2_HASH_ROUNDS)) {

                if (!backupPasswordMatches(mCurrentPassword)) {

                    if (DEBUG) Slog.w(TAG, "Backup password mismatch; aborting");

                    return;

                }

                }



                mBytes = 0;

                byte[] buffer = new byte[32 * 1024];
@@ -3252,8 +3315,12 @@ 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);
@@ -3261,7 +3328,8 @@ 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;

                            }
@@ -3321,25 +3389,14 @@ 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 {

                if (encryptionName.equals(ENCRYPTION_ALGORITHM_NAME)) {



                    String userSaltHex = readHeaderLine(rawInStream); // 5

                    byte[] userSalt = hexToByteArray(userSaltHex);



                    String ckSaltHex = readHeaderLine(rawInStream); // 6

                    byte[] ckSalt = hexToByteArray(ckSaltHex);



                    int rounds = Integer.parseInt(readHeaderLine(rawInStream)); // 7

                    String userIvHex = readHeaderLine(rawInStream); // 8



                    String masterKeyBlobHex = readHeaderLine(rawInStream); // 9



                    // decrypt the master key blob

            try {

                Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");

                    SecretKey userKey = buildPasswordKey(mDecryptPassword, userSalt,

                SecretKey userKey = buildPasswordKey(algorithm, mDecryptPassword, userSalt,

                        rounds);

                byte[] IV = hexToByteArray(userIvHex);

                IvParameterSpec ivSpec = new IvParameterSpec(IV);
@@ -3365,7 +3422,7 @@ class BackupManagerService extends IBackupManager.Stub { 
                        offset, offset + len);



                // now validate the decrypted master key against the checksum

                    byte[] calculatedCk = makeKeyChecksum(mk, ckSalt, rounds);

                byte[] calculatedCk = makeKeyChecksum(algorithm, mk, ckSalt, rounds);

                if (Arrays.equals(calculatedCk, mkChecksum)) {

                    ivSpec = new IvParameterSpec(IV);

                    c.init(Cipher.DECRYPT_MODE,
@@ -3373,24 +3430,53 @@ class BackupManagerService extends IBackupManager.Stub { 
                            ivSpec);

                    // Only if all of the above worked properly will 'result' be assigned

                    result = new CipherInputStream(rawInStream, c);

                    } else Slog.w(TAG, "Incorrect password");

                } else Slog.w(TAG, "Unsupported encryption method: " + encryptionName);

                } else if (doLog) Slog.w(TAG, "Incorrect password");

            } catch (InvalidAlgorithmParameterException e) {

                Slog.e(TAG, "Needed parameter spec unavailable!", 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.

                Slog.w(TAG, "Incorrect password");

                if (doLog) Slog.w(TAG, "Incorrect password");

            } catch (IllegalBlockSizeException e) {

                Slog.w(TAG, "Invalid block size in master key");

                if (doLog) Slog.w(TAG, "Invalid block size in master key");

            } catch (NoSuchAlgorithmException e) {

                Slog.e(TAG, "Needed decryption algorithm unavailable!");

                if (doLog) Slog.e(TAG, "Needed decryption algorithm unavailable!");

            } catch (NoSuchPaddingException e) {

                Slog.e(TAG, "Needed padding mechanism unavailable!");

                if (doLog) Slog.e(TAG, "Needed padding mechanism unavailable!");

            } catch (InvalidKeyException e) {

                Slog.w(TAG, "Illegal password; aborting");

                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)) {



                    String userSaltHex = readHeaderLine(rawInStream); // 5

                    byte[] userSalt = hexToByteArray(userSaltHex);



                    String ckSaltHex = readHeaderLine(rawInStream); // 6

                    byte[] ckSalt = hexToByteArray(ckSaltHex);



                    int rounds = Integer.parseInt(readHeaderLine(rawInStream)); // 7

                    String userIvHex = readHeaderLine(rawInStream); // 8



                    String masterKeyBlobHex = readHeaderLine(rawInStream); // 9



                    // decrypt the master key blob

                    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 (NumberFormatException e) {

                Slog.w(TAG, "Can't parse restore data header");

            } catch (IOException e) {

tests/LegacyRestoreTest/README

0 → 100644
+18 −0
Original line number Diff line number Diff line 
The file "jbmr2-encrypted-settings-abcd.ab" in this directory is an encrypted

"adb backup" archive of the settings provider package.  It was generated on a

Nexus 4 running Android 4.3 (API 18), and so predates the Android 4.4 changes

to the PBKDF2 implementation.  The archive's encryption password, entered on-screen,

is "abcd" (with no quotation marks).



'adb restore' decrypts and applies the restored archive successfully on a device

running Android 4.3, but fails to restore correctly on a device running Android 4.4,

reporting an invalid password in logcat.  This is the situation reported in bug

<https://code.google.com/p/android/issues/detail?id=63880>.



The file "kk-fixed-encrypted-settings-abcd.ab" is a similar encrypted "adb backup"

archive, using the same key, generated on a Nexus 4 running Android 4.4 with a fix

to this bug in place.  This archive should be successfully restorable on any

version of Android which incorporates the fix.



These archives can be used as an ongoing test to verify that historical encrypted

archives from various points in Android's history can be successfully restored.

tests/LegacyRestoreTest/jbmr2-encrypted-settings-abcd.ab

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tests/LegacyRestoreTest/kk-fixed-encrypted-settings-abcd.ab

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