那些遇到过的问题

解码 base45 字符串，生成 cbor 压缩文件

Sh4*_*dow 3 javascript qr-code zlib certificate cbor

你好，我正在尝试读取我的绿通证书，我知道当你扫描二维码时，它会出现类似 HC1:NHFDFGDF...... 的内容，我也知道这是编码为 base45 的，所以我做了一个小小的 javascript 解码器，这是我的代码：

\n
const base45 = require(\'base45\');\n\n//of course my personal HC1: isnt here\nconst encodedData = \'C0C9BQF2LVU.TMBX4KDL*XD/GPWBILC9GGBYPLR-SAG1CSQ6U7SSQY%SJWLK34JWLG56H0API0TUL:12>\'\n\nconst decodedData = base45.decode(encodedData).toString(\'utf-8\');\n\nconsole.log(decodedData);\n
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这是回应：

\n
x\xda\xbb\xef\xbf\xbd\xe2\xbb\x88Q\xef\xbf\xbd\xef\xbf\xbdC#?\xef\xbf\xbd\xef\xbf\xbd-E\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdK\xef\xbf\xbdBX\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xd6\xb3I%|\xef\xbf\xbdzl\xef\xbf\xbd\xc8\xbc\xef\xbf\xbdqIbY\xe3\xaa\xa4\xef\xbf\xbd\xef\xbf\xbd\n\xef\xbf\xbd\xd2\xa2<\xef\xbf\xbd\xd2\xb2\xef\xbf\xbdL\xef\xbf\xbd\xef\xbf\xbd ?\xef\xbf\xbd\xef\xbf\xbd0gO+C\xef\xbf\xbd\xef\xbf\xbd+\xef\xbf\xbd`\xef\xbf\xbd\xef\xbf\xbd`\xd7\x800\xef\xbf\xbdH\'W\xef\xbf\xbdP\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdWwe\xcf\xa4\xef\xbf\xbd|\xef\xbf\xbd\xef\xbf\xbdI)yLI)%YFF\xef\xbf\xbd\xef\xbf\xbdf\xef\xbf\xbdFfI\xef\xbf\xbd\xc5\xa5\xef\xbf\xbd\xef\xbf\xbdy\xef\xbf\xbd\xef\xbf\xbd%\xef\xbf\xbdWe\xef\xbf\xbd+\xef\xbf\xbd$*\'\xde\x95\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdkh\xef\xbf\xbdf\xef\xbf\xbd\xef\xbf\xbdI\xef\xbf\xbd9\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdF\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdF\xef\xbf\xbdI\xef\xbf\xbd)LI%\xef\xbf\xbd&\xef\xbf\xbd\xc6\x96fIeY\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd)\xef\xbf\xbdIY\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdF {\n                                                                                                                                            \xef\xbf\xbdsVp\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd*8\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdz\xef\xbf\xbd8*\xef\xbf\xbd\xef\xbf\xbd:;\'\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\n     pMN\xef\xbf\xbd+*\xef\xbf\xbd\xef\xbf\xbd*\xef\xbf\xbd+JN\xef\xbf\xbd+\xef\xbf\xbd\xef\xbf\xbd  \xef\xbf\xbd\n                         \xef\xbf\xbd\xef\xbf\xbd**K-J5\xef\xbf\xbd3\xef\xbf\xbd3\xef\xbf\xbdp8\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdyM]\xef\xbf\xbdo\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbdE\xef\xbf\xbd_\xef\xbf\xbd\xef\xbf\xbdO.\xef\xbf\xbd\xcf\xa9\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\n\xef\xbf\xbdg\xef\xbf\xbd\xcb\xbd\xef\xbf\xbd\xef\xbf\xbd\\\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd="\xef\xbf\xbd\xef\xbf\xbd]\xdb\xb7\n\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd\xef\xbf\xbd{\xef\xbf\xbd\xef\xbf\xbdKq \xef\xbf\xbd\xef\xbf\xbd\n
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我读到的是，它的 base45 解码将导致 zlib 压缩文件，其中解压将导致 CBOR Web 令牌，但我卡住了，你能帮助我吗？这个结果正常吗？我还在学习

\n

jum*_*ack 5

我仅使用浏览器资源（没有node.js）解决了问题；我还找到了一些解释、测试数据、现场解码的官方来源（见答案末尾）：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <meta name="generator" content="PSPad editor, www.pspad.com">
  <title></title>
  </head>
  <body>
  <textarea id="encoded" name="encoded" cols=100 rows=10></textarea><br>
  <textarea id="decoded" name="decoded" cols=100 rows=10 value = "prova">hello</textarea><br>
  <span id="plain1" name="plain1">-</span> --&gt;
  <span id ="cod" name="cod">-</span> --&gt;
  <span id="plain2" name="plain2">-</span><br>
  <button onclick="test()">Test</button><br>
  <button onclick="vai()">Vai</button><br>
  <script src="pako.min.js"></script>
  <script src="my_base45_2.js"></script>
  <script src="cbor.js" type="text/javascript"></script>

<script>

// https://dev.to/lmillucci/javascript-how-to-decode-the-greenpass-qr-code-3dh0

function convert(decoded) {
    text="";
    for (var i = 0; i < decoded.length; i++) {
        text +=  String.fromCharCode(decoded[i]);
    }
    console.log("Text=",text);
    values = text.split(",");
    console.log("values: " ,values);
    final = "";
    for (var i=0; i<values.length; i++) {
        final += String.fromCharCode(values[i])
    }
    return final;
}

function test() {

    source = document.getElementById("decoded").value;
    console.log("source=",source);
    document.getElementById("plain1").innerHTML = source;

    var enc = new TextEncoder();
    buff= enc.encode(source);
    console.log("buff:" , buff);

    encoded2 = encode(buff);
    console.log("encoded2:" , encoded2);
    document.getElementById("cod").innerHTML = encoded2;

    source = encoded2;
    console.log("Encoded source=",source);
    decoded = decode(source).enc;
    converted = convert(decoded);

    console.log("Decoded=", decoded);
    console.log("converted=", converted);

    document.getElementById("plain2").innerHTML = converted;
}


function buf2hex(buffer) {
// /sf/ask/2401699191/
    var u = new Uint8Array(buffer),
        a = new Array(u.length),
        i = u.length;
    while (i--) // map to hex
        a[i] = (u[i] < 16 ? '0' : '') + u[i].toString(16);
    u = null; // free memory
    return a.join('');
};


function typedArrayToBuffer(array) {
// /sf/ask/2605979981/
    return array.buffer.slice(array.byteOffset, array.byteLength + array.byteOffset)
}


function vai() {
    source = document.getElementById("encoded").value;
    console.log("Encoded source=",source);

    // Decode BASE45:
    decoded = decode(source).enc;

    // Unzip the decoded:
    COSEbin =  pako.inflate(decode(source).raw);
        COSE = buf2hex(COSEbin);

        var typedArray = new Uint8Array(COSE.match(/[\da-f]{2}/gi).map(function (h) {
          return parseInt(h, 16)
        })) // /sf/ask/3019186971/
        var unzipped = typedArray.buffer;

        [headers1, headers2, cbor_data, signature] = CBOR.decode(unzipped);
        cbor_dataArr = typedArrayToBuffer(cbor_data);
        greenpassData  = CBOR.decode(cbor_dataArr);

        console.log(greenpassData);
}
</script>
  </body>
</html>
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关键是“双CBOR解码”：一次是不够的：

CBOR解码：

[headers1, headers2, cbor_data, signature] = CBOR.decode(unzipped);
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转换为数组：

cbor_dataArr = typedArrayToBuffer(cbor_data);
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进一步的 CBOR 转换：

greenpassData  = CBOR.decode(cbor_dataArr);
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我的base45解码器版本（“my_base45_2.js”），改编自node.js版本：

 function encode(uint8array) {
    var output = [];

    for (var i = 0, length = uint8array.length; i < length; i+=2) {
      if (uint8array.length -i > 1) {
         var x = (uint8array[i]<<8)+ uint8array[i+1]
         var [ e, x ]  = divmod(x, 45*45)
         var [ d, c ] = divmod(x, 45)
         output.push(fromCharCode(c) + fromCharCode(d) + fromCharCode(e))
     } else {
         var x = uint8array[i]
         var [ d, c ] = divmod(x, 45)
         output.push(fromCharCode(c) + fromCharCode(d))
     }
    }
    return output.join('')
  };

  var divmod = function divmod(a,b) {
    var remainder = a
    var quotient = 0
    if (a >= b) {
        remainder = a % b
    quotient = (a - remainder) / b
    }
    return [ quotient, remainder ]
  }

  const BASE45_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:"
  var fromCharCode = function fromCharCode(c) {
    return BASE45_CHARSET.charAt(c);
  };

function decode(str) {
    var output = []
    var buf = []

    for(var i = 0, length=str.length; i < length; i++) {
//console.log(i);    
       var j = BASE45_CHARSET.indexOf(str[i])
       if (j < 0)
                console.log('Base45 decode: unknown character n.', i, j);
              //throw new Error('Base45 decode: unknown character');
       buf.push(j)
    }

    for(var i = 0, length=buf.length; i < length; i+=3) {
       var x = buf[i] + buf[i + 1] * 45
       if (length - i >= 3) {
          var [d, c] = divmod(x + buf[i + 2] * 45 * 45,256)
          output.push(d)
          output.push(c)
       } else {
         output.push(x)
       }
    }
console.log("output",output);    
    var enc = new TextEncoder();
    return {"enc" : enc.encode(output), "raw" : output};
    //return Buffer.from(output);
  };
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这些是解码步骤：

QR 码 --> QR DECODER --> RAW QR 解码字符串 --> BASE45 解码器--> zlib 压缩字符串 --> pako 库 --> COSE 字符串 --> CBOR 解码器 --> CBOR 字符串 --> CBOR解码器--> 最终 JSON 文件

我的绿色通行证解码参考指南：

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