/**
* 对密文进行解密.
*
* @param text 需要解密的密文
* @return 解密得到的明文
* @throws AesException aes解密失败
*/
String decrypt(String text) throws AesException {
byte[] original;
try {
// 设置解密模式为AES的CBC模式
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
SecretKeySpec key_spec = new SecretKeySpec(aesKey, "AES");
IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(aesKey, 0, 16));
cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);
// 使用BASE64对密文进行解码
byte[] encrypted = Base64.decodeBase64(text);
// 解密
original = cipher.doFinal(encrypted);
} catch (Exception e) {
e.printStackTrace();
throw new AesException(AesException.DecryptAESError);
}
String xmlContent, from_appid;
try {
// 去除补位字符
byte[] bytes = PKCS7Encoder.decode(original);
// 分离16位随机字符串,网络字节序和AppId
byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);
int xmlLength = recoverNetworkBytesOrder(networkOrder);
xmlContent = new String(Arrays.copyOfRange(bytes, 20, 20 + xmlLength), CHARSET);
from_appid = new String(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length), CHARSET);
} catch (Exception e) {
e.printStackTrace();
throw new AesException(AesException.IllegalBuffer);
}
// appid不相同的情况
if (!from_appid.equals(appId)) {
throw new AesException(AesException.ValidateAppidError);
}
return xmlContent;
}
/**
* 对AES消息解密
*
* @param appId
* @param encodingAesKey aes加密的密钥
* @param encryptContent 加密的消息体
* @return 解密后的字符
* @throws WeixinException
*/
public static String aesDecrypt(String appId, String encodingAesKey, String encryptContent)
throws WeixinException {
byte[] aesKey = Base64.decodeBase64(encodingAesKey + "=");
byte[] original;
try {
// 设置解密模式为AES的CBC模式
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
SecretKeySpec key_spec = new SecretKeySpec(aesKey, Consts.AES);
IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(aesKey, 0, 16));
cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);
// 使用BASE64对密文进行解码
byte[] encrypted = Base64.decodeBase64(encryptContent);
// 解密
original = cipher.doFinal(encrypted);
} catch (Exception e) {
throw new WeixinException("-40007", "AES解密失败" + e.getMessage());
}
String xmlContent, fromAppId;
try {
// 去除补位字符
byte[] bytes = PKCS7Encoder.decode(original);
// 获取表示xml长度的字节数组
byte[] lengthByte = Arrays.copyOfRange(bytes, 16, 20);
// 获取xml消息主体的长度(byte[]2int)
// http://my.oschina.net/u/169390/blog/97495
int xmlLength =
lengthByte[3] & 0xff
| (lengthByte[2] & 0xff) << 8
| (lengthByte[1] & 0xff) << 16
| (lengthByte[0] & 0xff) << 24;
xmlContent = StringUtil.newStringUtf8(Arrays.copyOfRange(bytes, 20, 20 + xmlLength));
fromAppId = StringUtil.newStringUtf8(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length));
} catch (Exception e) {
throw new WeixinException("-40008", "xml内容不合法" + e.getMessage());
}
// 校验appId是否一致
if (!fromAppId.trim().equals(appId)) {
throw new WeixinException(
"-40005", "校验AppID失败,expect " + appId + ",but actual is " + fromAppId);
}
return xmlContent;
}
