微信支付回调 敏感信息解密 v3 php

今天博主用了一波微信的v3版本的支付，支付成功后发现回调跟v2的完全不一样，于是去看了了一波v3的文档，发现信息是经过加密的，需要解密才能获取的到

但是最悲催的是文档上没写怎么解密的，经过了一下午的百度，找论坛，终于找到了文档地址，成功的拿到了我想要的信息，记录分享一波

1.支付成功，拿到回调信息后，转成数组后信息如下

$xml = ['id' => 'xxx',
            'create_time' => '2020-08-19T12:16:56+08:00',
            'resource_type' => 'xxx',
            'event_type' => 'TRANSACTION.SUCCESS',
            'summary' => '支付成功',
            'resource' => [
                'original_type' => 'xxxx',
                'algorithm' => 'AEAD_AES_256_GCM',
                'ciphertext' => 'xxx',
                'associated_data' => 'xxxx',
                'nonce' => 'xxx',]
        ];

2.你想要的信息在 resource 里面，但是是经过加密的，接下来需要解密一波

先创建一个 AesUtil.php，复制以下代码粘进去

<?php

class AesUtil
{
    /**
     * AES key
     *
     * @var string
     */
    private $aesKey;

    const KEY_LENGTH_BYTE = 32;
    const AUTH_TAG_LENGTH_BYTE = 16;

    /**
     * Constructor
     */
    public function __construct($aesKey)
    {
        if (strlen($aesKey) != self::KEY_LENGTH_BYTE) {
            throw new InvalidArgumentException('无效的ApiV3Key，长度应为32个字节');
        }
        $this->aesKey = $aesKey;
    }

    /**
     * Decrypt AEAD_AES_256_GCM ciphertext
     *
     * @param string    $associatedData     AES GCM additional authentication data
     * @param string    $nonceStr           AES GCM nonce
     * @param string    $ciphertext         AES GCM cipher text
     *
     * @return string|bool      Decrypted string on success or FALSE on failure
     */
    public function decryptToString($associatedData, $nonceStr, $ciphertext)
    {
        $ciphertext = \base64_decode($ciphertext);
        if (strlen($ciphertext) <= self::AUTH_TAG_LENGTH_BYTE) {
            return false;
        }

        // ext-sodium (default installed on >= PHP 7.2)
        if (function_exists('\sodium_crypto_aead_aes256gcm_is_available') &&
            \sodium_crypto_aead_aes256gcm_is_available()) {
            return \sodium_crypto_aead_aes256gcm_decrypt($ciphertext, $associatedData, $nonceStr, $this->aesKey);
        }

        // ext-libsodium (need install libsodium-php 1.x via pecl)
        if (function_exists('\Sodium\crypto_aead_aes256gcm_is_available') &&
            \Sodium\crypto_aead_aes256gcm_is_available()) {
            return \Sodium\crypto_aead_aes256gcm_decrypt($ciphertext, $associatedData, $nonceStr, $this->aesKey);
        }

        // openssl (PHP >= 7.1 support AEAD)
        if (PHP_VERSION_ID >= 70100 && in_array('aes-256-gcm', \openssl_get_cipher_methods())) {
            $ctext = substr($ciphertext, 0, -self::AUTH_TAG_LENGTH_BYTE);
            $authTag = substr($ciphertext, -self::AUTH_TAG_LENGTH_BYTE);

            return \openssl_decrypt($ctext, 'aes-256-gcm', $this->aesKey, \OPENSSL_RAW_DATA, $nonceStr,
                $authTag, $associatedData);
        }

        throw new \RuntimeException('AEAD_AES_256_GCM需要PHP 7.1以上或者安装libsodium-php');
    }
}

3.接下来就是解密了

var_dump((new AesUtil('你的APIv3秘钥'))->decryptToString($xml['resource']['associated_data'],$xml['resource']['nonce'],$xml['resource']['ciphertext']));

文档地址：https://wechatpay-api.gitbook.io/wechatpay-api-v3/qian-ming-zhi-nan-1/zheng-shu-he-hui-tiao-bao-wen-jie-mi