java – NTAG212 Mifare Ultralight与身份验证

2019-09-28 21:13:15 阅读：337 来源： 互联网

标签：android java authentication nfc mifare

我是NFC Android的新手,我已经坚持了几天试图通过身份验证获得NTAG212 Mifare Ultralight的第7页,我已经有了PWD和PACK来完成基于NTAG212文档的PWD_AUTH.

我这样做…

//assume password as array of bytes
//assume pack as array of bytes
try{
nfc.connect();
byte[] cmd1 = nfc.transceive(new byte[]{ (byte) 0x30, (byte) 0x00 }); //read the page 0     to make the NFC active
nfc.transceive(new byte[]{
   (byte) 0x1B, //command for PWD_AUTH
   pass[0],
   pass[1],
   pass[2],
   pass[3]
});
byte[] cmd4 = nfc.transceive(new byte[]{ (byte) 0x30, (byte) 0x04 }); //read the page 4
}catch(TagLostException e){
  e.printStackTrace();
}catch(IOException e){
  e.printStachTrace();
}finally{
    try{
        nfc.close();
    }catch(Exception e){
      //display failed to close
    }
}

我总是收到android.nfc.TagLostException：标签丢失了.将PWD_AUTH命令发送到NFC后出错.有人能告诉我我做错了什么吗？我的方法是否正确？请帮忙.

注意：我已经多次阅读过NTAG212的文档,搜索了google,stackoverflow和所有可能的资源.

TIA,
Kenster

解决方法:

您发送到标记的PWD_AUTH命令没有多大意义.

PWD_AUTH命令的想法是,如果使用正确的密码进行身份验证,则发送密码(4字节值)并且标签以其密码确认(PACK)值(2字节值)进行响应.然后,您可以根据预期密码确认来验证PACK值,以“验证”标签.

所以正确的命令是：

byte[] response = nfc.transceive(new byte[] {
    (byte) 0x1B, // PWD_AUTH
    pass[0], pass[1], pass[2], pass[3]
});
if ((response != null) && (response.length >= 2)) {
   byte[] pack = Arrays.copyOf(response, 2);
   // TODO: verify PACK to confirm that tag is authentic (not really,
   // but that whole PWD_AUTH/PACK authentication mechanism was not
   // really meant to bring much security, I hope; same with the
   // NTAG signature btw.)
}

您需要什么才能启用密码保护(在NTAG212上)：

>将PWD(第39页)设置为所需的密码(默认值为0xFFFFFFFF).

byte[] response = nfc.transceive(new byte[] {
    (byte) 0xA2, // WRITE
    (byte) 39,   // page address
    pass[0], pass[1], pass[2], pass[3]
});

>将PACK(第40页,字节0-1)设置为所需的密码确认(默认值为0x0000).

byte[] response = nfc.transceive(new byte[] {
    (byte) 0xA2, // WRITE
    (byte) 40,   // page address
    pack[0], pack[1],   // bytes 0-1 are PACK value
    (byte) 0, (byte) 0  // other bytes are RFU and must be written as 0
});

>将AUTHLIM(第38页,字节0,位2-0)设置为最大失败密码验证尝试次数(将此值设置为0将允许无限次数的PWD_AUTH尝试).
>将PROT(第38页,字节0,位7)设置为所需的值(0 =仅在写访问时需要PWD_AUTH,1 =读和写访问需要PWD_AUTH).

byte[] response = nfc.transceive(new byte[] {
    (byte) 0x30, // READ
    (byte) 38    // page address
});
if ((response != null) && (response.length >= 16)) {  // read always returns 4 pages
    boolean prot = false;  // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
    int authlim = 0; // value between 0 and 7
    response = nfc.transceive(new byte[] {
        (byte) 0xA2, // WRITE
        (byte) 38,   // page address
        (byte) ((response[0] & 0x078) | (prot ? 0x080 : 0x000) | (authlim & 0x007)),
        response[1], response[2], response[3]  // keep old value for bytes 1-3, you could also simply set them to 0 as they are currently RFU and must always be written as 0 (response[1], response[2], response[3] will contain 0 too as they contain the read RFU value)
    });
}

>将AUTH0(第37页,字节3)设置为应该要求密码验证的第一页.

byte[] response = nfc.transceive(new byte[] {
    (byte) 0x30, // READ
    (byte) 37    // page address
});
if ((response != null) && (response.length >= 16)) {  // read always returns 4 pages
    boolean prot = false;  // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
    int auth0 = 0; // first page to be protected, set to a value between 0 and 37 for NTAG212
    response = nfc.transceive(new byte[] {
        (byte) 0xA2, // WRITE
        (byte) 37,   // page address
        response[0], // keep old value for byte 0
        response[1], // keep old value for byte 1
        response[2], // keep old value for byte 2
        (byte) (auth0 & 0x0ff)
    });
}

如果您使用MifareUltralight标记技术,而不是直接使用收发方法,您还可以使用readPages和writePage方法：

> READ命令

byte[] response = nfc.transceive(new byte[] {
    (byte) 0x30,                  // READ
    (byte) (pageAddress & 0x0ff)  // page address
});

是等价的

byte[] response = nfc.readPages(pageAddress);

> WRITE命令

byte[] data = { (byte)..., (byte)..., (byte)..., (byte)... };
byte[] response = nfc.transceive(new byte[] {
    (byte) 0xA2,                  // WRITE
    (byte) (pageAddress & 0x0ff), // page address
    data[0], data[1], data[2], data[3]
});

是等价的

nfc.writePage(pageAddress, data);

标签：android,java,authentication,nfc,mifare
来源： https://codeday.me/bug/20190928/1829257.html

本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享；
2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关；
3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关；
4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除；
5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。

ICode9

java – NTAG212 Mifare Ultralight与身份验证