结论：

方案1【2020-07-04更新】【厂商码失效】【https://api-mifit-cn.huami.com】被华米替换成了【https://api-mifit-cn2.huami.com】

小米手环5 NFC可以通过修改HTTPS的POST 数据来自定义NFC卡片的所有扇区数据；

方案2

1. 先手环复制一张没有加密的实体门禁卡（实体门禁卡卡号要提前写成自己想要的卡号），并且启用。
2. 然后通过电脑+NFC读卡器（ACR122U）直接修改这张卡的数据。除去0扇区第0行外，其它所有数据都可以修改。因为0扇区第0行包含卡号、校验码和厂商码，所以小米手环不允许改。

着重介绍一下方案1：

方案1的实现：

我们利用小米手环NFC（3，4和5代）进行门卡模拟，需要读取一张非加密门禁卡。读取成功后，手机会将这张卡的卡号（uid）和所有数据(blockContent)上传至服务器，所有的手环指令都由服务器生成，再下发到手机，手机通过蓝牙将指令传给手环。这些指令我全都看不懂，也没办法自己生成手环指令。但是我可以在手机将卡号（uid）和所有数据(blockContent)上传至服务器前进行更改成自己想要的，然后由小米服务器自己去生成指令即可成功。

可以借鉴我以前的小米手环3 NFC数据修改的方式借鉴电脑抓包和改包。
https://www.jianshu.com/p/8f944a7ac8d1

抓包改包软件很多，自行选择。

接下来，介绍两个关键请求和上传参数

第一个api和参数：【2020-07-04更新】【https://api-mifit-cn.huami.com】被华米替换成了【https://api-mifit-cn2.huami.com】

https://api-mifit-cn.huami.com/nfc/accessCard/script/init?r=A07A0065-DAC1-4C29-82DA-C30B664A37FA&t=1592767900198

Request Body为：
{
"fareCardType": 0,
"fetch_adpu_mode": "SYNC",
"product_sub_type": "",
"sak": "08",
"uid": "12345678",
"aid": "",
"atqa": "0400",
"size": 1024,
"action_type": "copyFareCard",
"blockContent": "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"
}

第二个api和参数：【2020-07-04更新】【https://api-mifit-cn.huami.com】被华米替换成了【https://api-mifit-cn2.huami.com】

https://api-mifit-cn.huami.com/nfc/accessCard/script/request?r=A07A0065-DAC1-4C29-82DA-C30B664A37FA&t=1592767901974

Request Body为：

{
"uid": "12345678",
"fareCardType": 0,
"product_sub_type": "",
"blockContent": "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",
"fetch_adpu_mode": "SYNC",
"session": "3581-547405239-44086875137",
"size": 1024,
"atqa": "0400",
"current_step": "1",
"sak": "08",
"command_results": {
"succeed": true,
"results": [
{
"result": "6F108408A000000151000000A5049F6501FF9000",
"checker": "^(9000|6283)",
"command": "8050200008691C3B013B3EED18",
"index": "2"
}
]
},
"aid": "",
"action_type": "copyFareCard"
}

你的任务：

1. 首先手机处于被抓包的状态，然后点击复制门禁卡（需要未加密的门禁卡，后面的api才会被触发）
2. 利用抓包和改包工具，在Request请求前，拦截这两个API请求，并修改这两个请求体的两个参数：uid和blockContent，最后复制成功后的卡就是你自定义的NFC数据了。
3. 安卓我不确定能不能抓包，安卓系统信任证书太严格了。iOS绝对有效，我写了一个thor脚本，会用thor的应该能明白怎么去自定义数据了。
   里面涉及较多电脑相关知识，无法做到一一解释，不懂可以搜百度。

iPhone 演示 NFC全部数据模拟【视频已经被B站下架了】

https://t.bilibili.com/404738669802148832

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