The Tor Browser: mobile/android/base/sync/crypto/PBKDF2.java@fc2d59ddac77

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 package org.mozilla.gecko.sync.crypto;

     7 import java.security.GeneralSecurityException;

     8 import java.util.Arrays;

    10 import javax.crypto.Mac;

    11 import javax.crypto.ShortBufferException;

    12 import javax.crypto.spec.SecretKeySpec;

    14 public class PBKDF2 {

    15   public static byte[] pbkdf2SHA256(byte[] password, byte[] salt, int c, int dkLen)

    16       throws GeneralSecurityException {

    17     final String algorithm = "HmacSHA256";

    18     SecretKeySpec keyspec = new SecretKeySpec(password, algorithm);

    19     Mac prf = Mac.getInstance(algorithm);

    20     prf.init(keyspec);

    22     int hLen = prf.getMacLength();

    24     byte U_r[] = new byte[hLen];

    25     byte U_i[] = new byte[salt.length + 4];

    26     byte scratch[] = new byte[hLen];

    28     int l = Math.max(dkLen, hLen);

    29     int r = dkLen - (l - 1) * hLen;

    30     byte T[] = new byte[l * hLen];

    31     int ti_offset = 0;

    32     for (int i = 1; i <= l; i++) {

    33       Arrays.fill(U_r, (byte) 0);

    34       F(T, ti_offset, prf, salt, c, i, U_r, U_i, scratch);

    35       ti_offset += hLen;

    36     }

    38     if (r < hLen) {

    39       // Incomplete last block.

    40       byte DK[] = new byte[dkLen];

    41       System.arraycopy(T, 0, DK, 0, dkLen);

    42       return DK;

    43     }

    45     return T;

    46   }

    48   private static void F(byte[] dest, int offset, Mac prf, byte[] S, int c, int blockIndex, byte U_r[], byte U_i[], byte[] scratch)

    49       throws ShortBufferException, IllegalStateException {

    50     final int hLen = prf.getMacLength();

    52     // U0 = S || INT (i);

    53     System.arraycopy(S, 0, U_i, 0, S.length);

    54     INT(U_i, S.length, blockIndex);

    56     for (int i = 0; i < c; i++) {

    57       prf.update(U_i);

    58       prf.doFinal(scratch, 0);

    59       U_i = scratch;

    60       xor(U_r, U_i);

    61     }

    63     System.arraycopy(U_r, 0, dest, offset, hLen);

    64   }

    66   private static void xor(byte[] dest, byte[] src) {

    67     for (int i = 0; i < dest.length; i++) {

    68       dest[i] ^= src[i];

    69     }

    70   }

    72   private static void INT(byte[] dest, int offset, int i) {

    73     dest[offset + 0] = (byte) (i / (256 * 256 * 256));

    74     dest[offset + 1] = (byte) (i / (256 * 256));

    75     dest[offset + 2] = (byte) (i / (256));

    76     dest[offset + 3] = (byte) (i);

    77   }

    78 }

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