com.fastchar.pay.wx.FastWxPKCS7 Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of fastchar-pay Show documentation
FastChar-Pay is a FastChar plugin.
The newest version!
package com.fastchar.pay.wx;

import com.fastchar.utils.FastBase64Utils;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;

/**
 * @author 沈建（Janesen）
 * @date 2021/2/19 10:32
 */
public class FastWxPKCS7 {
    private static final Charset CHARSET = StandardCharsets.UTF_8;
    private static final int BLOCK_SIZE = 32;

    /**
     * 获得对明文进行补位填充的字节.
     *
     * @param count
     *            需要进行填充补位操作的明文字节个数
     * @return 补齐用的字节数组
     */
    private static byte[] encode(int count) {
        // 计算需要填充的位数
        int amountToPad = BLOCK_SIZE - (count % BLOCK_SIZE);
        if (amountToPad == 0) {
            amountToPad = BLOCK_SIZE;
        }
        // 获得补位所用的字符
        char padChr = chr(amountToPad);
        String tmp = new String();
        for (int index = 0; index < amountToPad; index++) {
            tmp += padChr;
        }
        return tmp.getBytes(CHARSET);
    }

    /**
     * 删除解密后明文的补位字符
     *
     * @param decrypted
     *            解密后的明文
     * @return 删除补位字符后的明文
     */
    private static byte[] decode(byte[] decrypted) {
        int pad = decrypted[decrypted.length - 1];
        if (pad < 1 || pad > 32) {
            pad = 0;
        }
        return Arrays.copyOfRange(decrypted, 0, decrypted.length - pad);
    }


    /**
     * 将数字转化成ASCII码对应的字符，用于对明文进行补码
     *
     * @param a
     *            需要转化的数字
     * @return 转化得到的字符
     */
    private static char chr(int a) {
        byte target = (byte) (a & 0xFF);
        return (char) target;
    }


    /**
     * 解密数据
     */
    public static String decrypt(String encryptedData, String sessionKey, String iv) {
        try {
            FastWxAES aes = new FastWxAES();
            byte[] resultByte = aes.decrypt(FastBase64Utils.decodeToBytes(encryptedData),
                    FastBase64Utils.decodeToBytes(sessionKey), FastBase64Utils.decodeToBytes(iv));
            if (null != resultByte && resultByte.length > 0) {
                return new String(decode(resultByte));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}