com.google.gerrit.server.account.HashedPassword.java Source code

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Here is the source code for com.google.gerrit.server.account.HashedPassword.java

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// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gerrit.server.account;

import com.google.common.base.Preconditions;
import com.google.common.io.BaseEncoding;
import com.google.common.primitives.Ints;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import org.apache.commons.codec.DecoderException;
import org.bouncycastle.crypto.generators.BCrypt;
import org.bouncycastle.util.Arrays;

/**
 * Holds logic for salted, hashed passwords. It uses BCrypt from BouncyCastle, which truncates
 * passwords at 72 bytes.
 */
public class HashedPassword {
    private static final String ALGORITHM_PREFIX = "bcrypt:";
    private static final SecureRandom secureRandom = new SecureRandom();
    private static final BaseEncoding codec = BaseEncoding.base64();

    // bcrypt uses 2^cost rounds. Since we use a generated random password, no need
    // for a high cost.
    private static final int DEFAULT_COST = 4;

    /**
     * decodes a hashed password encoded with {@link #encode}.
     *
     * @throws DecoderException if input is malformed.
     */
    public static HashedPassword decode(String encoded) throws DecoderException {
        if (!encoded.startsWith(ALGORITHM_PREFIX)) {
            throw new DecoderException("unrecognized algorithm");
        }

        String[] fields = encoded.split(":");
        if (fields.length != 4) {
            throw new DecoderException("want 4 fields");
        }

        Integer cost = Ints.tryParse(fields[1]);
        if (cost == null) {
            throw new DecoderException("cost parse failed");
        }

        if (!(cost >= 4 && cost < 32)) {
            throw new DecoderException("cost should be 4..31 inclusive, got " + cost);
        }

        byte[] salt = codec.decode(fields[2]);
        if (salt.length != 16) {
            throw new DecoderException("salt should be 16 bytes, got " + salt.length);
        }
        return new HashedPassword(codec.decode(fields[3]), salt, cost);
    }

    private static byte[] hashPassword(String password, byte[] salt, int cost) {
        byte[] pwBytes = password.getBytes(StandardCharsets.UTF_8);

        return BCrypt.generate(pwBytes, salt, cost);
    }

    public static HashedPassword fromPassword(String password) {
        byte[] salt = newSalt();

        return new HashedPassword(hashPassword(password, salt, DEFAULT_COST), salt, DEFAULT_COST);
    }

    private static byte[] newSalt() {
        byte[] bytes = new byte[16];
        secureRandom.nextBytes(bytes);
        return bytes;
    }

    private byte[] salt;
    private byte[] hashed;
    private int cost;

    private HashedPassword(byte[] hashed, byte[] salt, int cost) {
        this.salt = salt;
        this.hashed = hashed;
        this.cost = cost;

        Preconditions.checkState(cost >= 4 && cost < 32);

        // salt must be 128 bit.
        Preconditions.checkState(salt.length == 16);
    }

    /**
     * Serialize the hashed password and its parameters for persistent storage.
     *
     * @return one-line string encoding the hash and salt.
     */
    public String encode() {
        return ALGORITHM_PREFIX + cost + ":" + codec.encode(salt) + ":" + codec.encode(hashed);
    }

    public boolean checkPassword(String password) {
        // Constant-time comparison, because we're paranoid.
        return Arrays.areEqual(hashPassword(password, salt, cost), hashed);
    }
}