高校教务系统登录页面JS分析——华南理工大学

高校教务系统密码加密逻辑及JS逆向

本文将介绍高校教务系统的密码加密逻辑以及使用JavaScript进行逆向分析的过程。通过本文，你将了解到密码加密的基本概念、常用加密算法以及如何通过逆向分析来破解密码。

本文仅供交流学习，勿用于非法用途。

一、密码加密基本概念

密码加密是一种保护信息安全的技术手段，它通过将明文（原始信息）转换为密文（加密后的信息），以防止未经授权的访问和篡改。常见的密码加密算法有MD5、SHA-1、SHA-256等。

1.1 加密过程

加密过程通常包括以下步骤：

1. 密钥扩展：将密钥扩展为多个轮值，每个轮值都与明文的一部分有关。
2. 初始轮值生成：将扩展后的密钥与轮常数进行某种运算，生成第一轮加密的密文。
3. 多轮迭代：对密文进行多轮迭代操作，每轮操作都包括非线性函数、模运算和轮常数的变换。
4. 最终密文：经过多轮迭代后，得到最终的密文。

1.2 解密过程

解密过程与加密过程相反，通过反向操作来恢复原始明文。通常需要知道加密时使用的密钥和算法。

二、高校教务系统密码加密逻辑分析

2.1 抓包

我们首先打开教务系统的登录页面，我们可以看到，只有学号和密码，有的高校会有验证码，或者有的高校是错误一次密码，会验证验证码。

我们打开开发者工具，尝试登录抓包，网页会返回这样的数据接口。我们用户名和密码都是默认输入1234，你也可以输入其他的。

2.2 分析加密参数

我们接下来，就是来分析这个密码是怎么加密的。我们全局搜索rsa。定位到加密的位置。我们这里只有这个参数被加密了。我们猜想密码相关信息都包含在这个里面。

我们可以看到这里，定义了rsa是怎么生成的，是把u+p+lt拼接了在一起，这个还是第一次遇到。

三、JS逆向分析方法

逆向分析是指从已知的加密文本或程序中还原出原始信息的过程。在本例中，我们将使用JavaScript编写一个简单的逆向分析工具，用于逆向高校教务系统的密码。

环境使用

• python 3.9
• pycharm
• node

我们全局搜索strEnc，我们就很容易定位到一个函数，我们不难发现其加密原理。

function strEnc(data,firstKey,secondKey,thirdKey){  
  
 var leng = data.length;  
 var encData = "";  
 var firstKeyBt,secondKeyBt,thirdKeyBt,firstLength,secondLength,thirdLength;  
 if(firstKey != null && firstKey != ""){      
   firstKeyBt = getKeyBytes(firstKey);  
   firstLength = firstKeyBt.length;  
 }  
 if(secondKey != null && secondKey != ""){  
   secondKeyBt = getKeyBytes(secondKey);  
   secondLength = secondKeyBt.length;  
 }  
 if(thirdKey != null && thirdKey != ""){  
   thirdKeyBt = getKeyBytes(thirdKey);  
   thirdLength = thirdKeyBt.length;  
 }    
   

1. 首先，函数会接受两个参数：数据字符串data和密钥key。
2. 然后，通过CryptoJS.enc.Utf8.parse(key)将密钥从普通的字符串转换为CryptoJS可以处理的二进制格式。
3. 接着，使用CryptoJS.AES.encrypt(data, key, {mode: CryptoJS.mode.ECB, padding: CryptoJS.pad.Pkcs7})对数据进行加密。这里使用了ECB模式和PKCS7填充方式。
4. 最后，通过调用.toString()将加密后的数据对象转换为字符串形式并返回。 

代码实现

/**
* DES加密解密
* @Copyright Copyright (c) 2006
* @author Guapo
* @see DESCore
*/

/*
* encrypt the string to string made up of hex
* return the encrypted string
*/
function strEnc(data,firstKey,secondKey,thirdKey){

 var leng = data.length;
 var encData = "";
 var firstKeyBt,secondKeyBt,thirdKeyBt,firstLength,secondLength,thirdLength;
 if(firstKey != null && firstKey != ""){
   firstKeyBt = getKeyBytes(firstKey);
   firstLength = firstKeyBt.length;
 }
 if(secondKey != null && secondKey != ""){
   secondKeyBt = getKeyBytes(secondKey);
   secondLength = secondKeyBt.length;
 }
 if(thirdKey != null && thirdKey != ""){
   thirdKeyBt = getKeyBytes(thirdKey);
   thirdLength = thirdKeyBt.length;
 }

 if(leng > 0){
   if(leng < 4){
     var bt = strToBt(data);
     var encByte ;
     if(firstKey != null && firstKey !="" && secondKey != null && secondKey != "" && thirdKey != null && thirdKey != ""){
       var tempBt;
       var x,y,z;
       tempBt = bt;
       for(x = 0;x < firstLength ;x ++){
         tempBt = enc(tempBt,firstKeyBt[x]);
       }
       for(y = 0;y < secondLength ;y ++){
         tempBt = enc(tempBt,secondKeyBt[y]);
       }
       for(z = 0;z < thirdLength ;z ++){
         tempBt = enc(tempBt,thirdKeyBt[z]);
       }
       encByte = tempBt;
     }else{
       if(firstKey != null && firstKey !="" && secondKey != null && secondKey != ""){
         var tempBt;
         var x,y;
         tempBt = bt;
         for(x = 0;x < firstLength ;x ++){
           tempBt = enc(tempBt,firstKeyBt[x]);
         }
         for(y = 0;y < secondLength ;y ++){
           tempBt = enc(tempBt,secondKeyBt[y]);
         }
         encByte = tempBt;
       }else{
         if(firstKey != null && firstKey !=""){
           var tempBt;
           var x = 0;
           tempBt = bt;
           for(x = 0;x < firstLength ;x ++){
             tempBt = enc(tempBt,firstKeyBt[x]);
           }
           encByte = tempBt;
         }
       }
     }
     encData = bt64ToHex(encByte);
   }else{
     var iterator = parseInt(leng/4);
     var remainder = leng%4;
     var i=0;
     for(i = 0;i < iterator;i++){
       var tempData = data.substring(i*4+0,i*4+4);
       var tempByte = strToBt(tempData);
       var encByte ;
       if(firstKey != null && firstKey !="" && secondKey != null && secondKey != "" && thirdKey != null && thirdKey != ""){
         var tempBt;
         var x,y,z;
         tempBt = tempByte;
         for(x = 0;x < firstLength ;x ++){
           tempBt = enc(tempBt,firstKeyBt[x]);
         }
         for(y = 0;y < secondLength ;y ++){
           tempBt = enc(tempBt,secondKeyBt[y]);
         }
         for(z = 0;z < thirdLength ;z ++){
           tempBt = enc(tempBt,thirdKeyBt[z]);
         }
         encByte = tempBt;
       }else{
         if(firstKey != null && firstKey !="" && secondKey != null && secondKey != ""){
           var tempBt;
           var x,y;
           tempBt = tempByte;
           for(x = 0;x < firstLength ;x ++){
             tempBt = enc(tempBt,firstKeyBt[x]);
           }
           for(y = 0;y < secondLength ;y ++){
             tempBt = enc(tempBt,secondKeyBt[y]);
           }
           encByte = tempBt;
         }else{
           if(firstKey != null && firstKey !=""){
             var tempBt;
             var x;
             tempBt = tempByte;
             for(x = 0;x < firstLength ;x ++){
               tempBt = enc(tempBt,firstKeyBt[x]);
             }
             encByte = tempBt;
           }
         }
       }
       encData += bt64ToHex(encByte);
     }
     if(remainder > 0){
       var remainderData = data.substring(iterator*4+0,leng);
       var tempByte = strToBt(remainderData);
       var encByte ;
       if(firstKey != null && firstKey !="" && secondKey != null && secondKey != "" && thirdKey != null && thirdKey != ""){
         var tempBt;
         var x,y,z;
         tempBt = tempByte;
         for(x = 0;x < firstLength ;x ++){
           tempBt = enc(tempBt,firstKeyBt[x]);
         }
         for(y = 0;y < secondLength ;y ++){
           tempBt = enc(tempBt,secondKeyBt[y]);
         }
         for(z = 0;z < thirdLength ;z ++){
           tempBt = enc(tempBt,thirdKeyBt[z]);
         }
         encByte = tempBt;
       }else{
         if(firstKey != null && firstKey !="" && secondKey != null && secondKey != ""){
           var tempBt;
           var x,y;
           tempBt = tempByte;
           for(x = 0;x < firstLength ;x ++){
             tempBt = enc(tempBt,firstKeyBt[x]);
           }
           for(y = 0;y < secondLength ;y ++){
             tempBt = enc(tempBt,secondKeyBt[y]);
           }
           encByte = tempBt;
         }else{
           if(firstKey != null && firstKey !=""){
             var tempBt;
             var x;
             tempBt = tempByte;
             for(x = 0;x < firstLength ;x ++){
               tempBt = enc(tempBt,firstKeyBt[x]);
             }
             encByte = tempBt;
           }
         }
       }
       encData += bt64ToHex(encByte);
     }
   }
 }
 return encData;
}

/*
* decrypt the encrypted string to the original string
*
* return  the original string
*/
function strDec(data,firstKey,secondKey,thirdKey){
 var leng = data.length;
 var decStr = "";
 var firstKeyBt,secondKeyBt,thirdKeyBt,firstLength,secondLength,thirdLength;
 if(firstKey != null && firstKey != ""){
   firstKeyBt = getKeyBytes(firstKey);
   firstLength = firstKeyBt.length;
 }
 if(secondKey != null && secondKey != ""){
   secondKeyBt = getKeyBytes(secondKey);
   secondLength = secondKeyBt.length;
 }
 if(thirdKey != null && thirdKey != ""){
   thirdKeyBt = getKeyBytes(thirdKey);
   thirdLength = thirdKeyBt.length;
 }

 var iterator = parseInt(leng/16);
 var i=0;
 for(i = 0;i < iterator;i++){
   var tempData = data.substring(i*16+0,i*16+16);
   var strByte = hexToBt64(tempData);
   var intByte = new Array(64);
   var j = 0;
   for(j = 0;j < 64; j++){
     intByte[j] = parseInt(strByte.substring(j,j+1));
   }
   var decByte;
   if(firstKey != null && firstKey !="" && secondKey != null && secondKey != "" && thirdKey != null && thirdKey != ""){
     var tempBt;
     var x,y,z;
     tempBt = intByte;
     for(x = thirdLength - 1;x >= 0;x --){
       tempBt = dec(tempBt,thirdKeyBt[x]);
     }
     for(y = secondLength - 1;y >= 0;y --){
       tempBt = dec(tempBt,secondKeyBt[y]);
     }
     for(z = firstLength - 1;z >= 0 ;z --){
       tempBt = dec(tempBt,firstKeyBt[z]);
     }
     decByte = tempBt;
   }else{
     if(firstKey != null && firstKey !="" && secondKey != null && secondKey != ""){
       var tempBt;
       var x,y,z;
       tempBt = intByte;
       for(x = secondLength - 1;x >= 0 ;x --){
         tempBt = dec(tempBt,secondKeyBt[x]);
       }
       for(y = firstLength - 1;y >= 0 ;y --){
         tempBt = dec(tempBt,firstKeyBt[y]);
       }
       decByte = tempBt;
     }else{
       if(firstKey != null && firstKey !=""){
         var tempBt;
         var x,y,z;
         tempBt = intByte;
         for(x = firstLength - 1;x >= 0 ;x --){
           tempBt = dec(tempBt,firstKeyBt[x]);
         }
         decByte = tempBt;
       }
     }
   }
   decStr += byteToString(decByte);
 }
 return decStr;
}
/*
* chang the string into the bit array
*
* return bit array(it's length % 64 = 0)
*/
function getKeyBytes(key){
 var keyBytes = new Array();
 var leng = key.length;
 var iterator = parseInt(leng/4);
 var remainder = leng%4;
 var i = 0;
 for(i = 0;i < iterator; i ++){
   keyBytes[i] = strToBt(key.substring(i*4+0,i*4+4));
 }
 if(remainder > 0){
   keyBytes[i] = strToBt(key.substring(i*4+0,leng));
 }
 return keyBytes;
}

/*
* chang the string(it's length <= 4) into the bit array
*
* return bit array(it's length = 64)
*/
function strToBt(str){
 var leng = str.length;
 var bt = new Array(64);
 if(leng < 4){
   var i=0,j=0,p=0,q=0;
   for(i = 0;ij;m--){
         pow *= 2;
       }
       bt[16*i+j]=parseInt(k/pow)%2;
     }
   }
   for(p = leng;p<4;p++){
     var k = 0;
     for(q=0;q<16;q++){
       var pow=1,m=0;
       for(m=15;m>q;m--){
         pow *= 2;
       }
       bt[16*p+q]=parseInt(k/pow)%2;
     }
   }
 }else{
   for(i = 0;i<4;i++){
     var k = str.charCodeAt(i);
     for(j=0;j<16;j++){
       var pow=1;
       for(m=15;m>j;m--){
         pow *= 2;
       }
       bt[16*i+j]=parseInt(k/pow)%2;
     }
   }
 }
 return bt;
}

/*
* chang the bit(it's length = 4) into the hex
*
* return hex
*/
function bt4ToHex(binary) {
 var hex;
 switch (binary) {
   case "0000" : hex = "0"; break;
   case "0001" : hex = "1"; break;
   case "0010" : hex = "2"; break;
   case "0011" : hex = "3"; break;
   case "0100" : hex = "4"; break;
   case "0101" : hex = "5"; break;
   case "0110" : hex = "6"; break;
   case "0111" : hex = "7"; break;
   case "1000" : hex = "8"; break;
   case "1001" : hex = "9"; break;
   case "1010" : hex = "A"; break;
   case "1011" : hex = "B"; break;
   case "1100" : hex = "C"; break;
   case "1101" : hex = "D"; break;
   case "1110" : hex = "E"; break;
   case "1111" : hex = "F"; break;
 }
 return hex;
}

/*
* chang the hex into the bit(it's length = 4)
*
* return the bit(it's length = 4)
*/
function hexToBt4(hex) {
 var binary;
 switch (hex) {
   case "0" : binary = "0000"; break;
   case "1" : binary = "0001"; break;
   case "2" : binary = "0010"; break;
   case "3" : binary = "0011"; break;
   case "4" : binary = "0100"; break;
   case "5" : binary = "0101"; break;
   case "6" : binary = "0110"; break;
   case "7" : binary = "0111"; break;
   case "8" : binary = "1000"; break;
   case "9" : binary = "1001"; break;
   case "A" : binary = "1010"; break;
   case "B" : binary = "1011"; break;
   case "C" : binary = "1100"; break;
   case "D" : binary = "1101"; break;
   case "E" : binary = "1110"; break;
   case "F" : binary = "1111"; break;
 }
 return binary;
}

/*
* chang the bit(it's length = 64) into the string
*
* return string
*/
function byteToString(byteData){
 var str="";
 for(i = 0;i<4;i++){
   var count=0;
   for(j=0;j<16;j++){
     var pow=1;
     for(m=15;m>j;m--){
       pow*=2;
     }
     count+=byteData[16*i+j]*pow;
   }
   if(count != 0){
     str+=String.fromCharCode(count);
   }
 }
 return str;
}

function bt64ToHex(byteData){
 var hex = "";
 for(i = 0;i<16;i++){
   var bt = "";
   for(j=0;j<4;j++){
     bt += byteData[i*4+j];
   }
   hex+=bt4ToHex(bt);
 }
 return hex;
}

function hexToBt64(hex){
 var binary = "";
 for(i = 0;i<16;i++){
   binary+=hexToBt4(hex.substring(i,i+1));
 }
 return binary;
}

/*
* the 64 bit des core arithmetic
*/

function enc(dataByte,keyByte){
 var keys = generateKeys(keyByte);
 var ipByte   = initPermute(dataByte);
 var ipLeft   = new Array(32);
 var ipRight  = new Array(32);
 var tempLeft = new Array(32);
 var i = 0,j = 0,k = 0,m = 0, n = 0;
 for(k = 0;k < 32;k ++){
   ipLeft[k] = ipByte[k];
   ipRight[k] = ipByte[32+k];
 }
 for(i = 0;i < 16;i ++){
   for(j = 0;j < 32;j ++){
     tempLeft[j] = ipLeft[j];
     ipLeft[j] = ipRight[j];
   }
   var key = new Array(48);
   for(m = 0;m < 48;m ++){
     key[m] = keys[i][m];
   }
   var  tempRight = xor(pPermute(sBoxPermute(xor(expandPermute(ipRight),key))), tempLeft);
   for(n = 0;n < 32;n ++){
     ipRight[n] = tempRight[n];
   }

 }


 var finalData =new Array(64);
 for(i = 0;i < 32;i ++){
   finalData[i] = ipRight[i];
   finalData[32+i] = ipLeft[i];
 }
 return finallyPermute(finalData);
}

function dec(dataByte,keyByte){
 var keys = generateKeys(keyByte);
 var ipByte   = initPermute(dataByte);
 var ipLeft   = new Array(32);
 var ipRight  = new Array(32);
 var tempLeft = new Array(32);
 var i = 0,j = 0,k = 0,m = 0, n = 0;
 for(k = 0;k < 32;k ++){
   ipLeft[k] = ipByte[k];
   ipRight[k] = ipByte[32+k];
 }
 for(i = 15;i >= 0;i --){
   for(j = 0;j < 32;j ++){
     tempLeft[j] = ipLeft[j];
     ipLeft[j] = ipRight[j];
   }
   var key = new Array(48);
   for(m = 0;m < 48;m ++){
     key[m] = keys[i][m];
   }

   var  tempRight = xor(pPermute(sBoxPermute(xor(expandPermute(ipRight),key))), tempLeft);
   for(n = 0;n < 32;n ++){
     ipRight[n] = tempRight[n];
   }
 }


 var finalData =new Array(64);
 for(i = 0;i < 32;i ++){
   finalData[i] = ipRight[i];
   finalData[32+i] = ipLeft[i];
 }
 return finallyPermute(finalData);
}

function initPermute(originalData){
 var ipByte = new Array(64);
 for (i = 0, m = 1, n = 0; i < 4; i++, m += 2, n += 2) {
   for (j = 7, k = 0; j >= 0; j--, k++) {
     ipByte[i * 8 + k] = originalData[j * 8 + m];
     ipByte[i * 8 + k + 32] = originalData[j * 8 + n];
   }
 }
 return ipByte;
}

function expandPermute(rightData){
 var epByte = new Array(48);
 for (i = 0; i < 8; i++) {
   if (i == 0) {
     epByte[i * 6 + 0] = rightData[31];
   } else {
     epByte[i * 6 + 0] = rightData[i * 4 - 1];
   }
   epByte[i * 6 + 1] = rightData[i * 4 + 0];
   epByte[i * 6 + 2] = rightData[i * 4 + 1];
   epByte[i * 6 + 3] = rightData[i * 4 + 2];
   epByte[i * 6 + 4] = rightData[i * 4 + 3];
   if (i == 7) {
     epByte[i * 6 + 5] = rightData[0];
   } else {
     epByte[i * 6 + 5] = rightData[i * 4 + 4];
   }
 }
 return epByte;
}

function xor(byteOne,byteTwo){
 var xorByte = new Array(byteOne.length);
 for(i = 0;i < byteOne.length; i ++){
   xorByte[i] = byteOne[i] ^ byteTwo[i];
 }
 return xorByte;
}

function sBoxPermute(expandByte){

   var sBoxByte = new Array(32);
   var binary = "";
   var s1 = [
       [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7],
       [0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8],
       [4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0],
       [15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 ]];

       /* Table - s2 */
   var s2 = [
       [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10],
       [3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5],
       [0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15],
       [13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 ]];

       /* Table - s3 */
   var s3= [
       [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8],
       [13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1],
       [13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7],
       [1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 ]];
       /* Table - s4 */
   var s4 = [
       [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15],
       [13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9],
       [10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4],
       [3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 ]];

       /* Table - s5 */
   var s5 = [
       [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9],
       [14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6],
       [4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14],
       [11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 ]];

       /* Table - s6 */
   var s6 = [
       [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11],
       [10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8],
       [9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6],
       [4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 ]];

       /* Table - s7 */
   var s7 = [
       [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1],
       [13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6],
       [1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2],
       [6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12]];

       /* Table - s8 */
   var s8 = [
       [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7],
       [1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2],
       [7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8],
       [2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11]];

   for(m=0;m<8;m++){
   var i=0,j=0;
   i = expandByte[m*6+0]*2+expandByte[m*6+5];
   j = expandByte[m * 6 + 1] * 2 * 2 * 2
     + expandByte[m * 6 + 2] * 2* 2
     + expandByte[m * 6 + 3] * 2
     + expandByte[m * 6 + 4];
   switch (m) {
     case 0 :
       binary = getBoxBinary(s1[i][j]);
       break;
     case 1 :
       binary = getBoxBinary(s2[i][j]);
       break;
     case 2 :
       binary = getBoxBinary(s3[i][j]);
       break;
     case 3 :
       binary = getBoxBinary(s4[i][j]);
       break;
     case 4 :
       binary = getBoxBinary(s5[i][j]);
       break;
     case 5 :
       binary = getBoxBinary(s6[i][j]);
       break;
     case 6 :
       binary = getBoxBinary(s7[i][j]);
       break;
     case 7 :
       binary = getBoxBinary(s8[i][j]);
       break;
   }
   sBoxByte[m*4+0] = parseInt(binary.substring(0,1));
   sBoxByte[m*4+1] = parseInt(binary.substring(1,2));
   sBoxByte[m*4+2] = parseInt(binary.substring(2,3));
   sBoxByte[m*4+3] = parseInt(binary.substring(3,4));
 }
 return sBoxByte;
}

function pPermute(sBoxByte){
 var pBoxPermute = new Array(32);
 pBoxPermute[ 0] = sBoxByte[15];
 pBoxPermute[ 1] = sBoxByte[ 6];
 pBoxPermute[ 2] = sBoxByte[19];
 pBoxPermute[ 3] = sBoxByte[20];
 pBoxPermute[ 4] = sBoxByte[28];
 pBoxPermute[ 5] = sBoxByte[11];
 pBoxPermute[ 6] = sBoxByte[27];
 pBoxPermute[ 7] = sBoxByte[16];
 pBoxPermute[ 8] = sBoxByte[ 0];
 pBoxPermute[ 9] = sBoxByte[14];
 pBoxPermute[10] = sBoxByte[22];
 pBoxPermute[11] = sBoxByte[25];
 pBoxPermute[12] = sBoxByte[ 4];
 pBoxPermute[13] = sBoxByte[17];
 pBoxPermute[14] = sBoxByte[30];
 pBoxPermute[15] = sBoxByte[ 9];
 pBoxPermute[16] = sBoxByte[ 1];
 pBoxPermute[17] = sBoxByte[ 7];
 pBoxPermute[18] = sBoxByte[23];
 pBoxPermute[19] = sBoxByte[13];
 pBoxPermute[20] = sBoxByte[31];
 pBoxPermute[21] = sBoxByte[26];
 pBoxPermute[22] = sBoxByte[ 2];
 pBoxPermute[23] = sBoxByte[ 8];
 pBoxPermute[24] = sBoxByte[18];
 pBoxPermute[25] = sBoxByte[12];
 pBoxPermute[26] = sBoxByte[29];
 pBoxPermute[27] = sBoxByte[ 5];
 pBoxPermute[28] = sBoxByte[21];
 pBoxPermute[29] = sBoxByte[10];
 pBoxPermute[30] = sBoxByte[ 3];
 pBoxPermute[31] = sBoxByte[24];
 return pBoxPermute;
}

function finallyPermute(endByte){
 var fpByte = new Array(64);
 fpByte[ 0] = endByte[39];
 fpByte[ 1] = endByte[ 7];
 fpByte[ 2] = endByte[47];
 fpByte[ 3] = endByte[15];
 fpByte[ 4] = endByte[55];
 fpByte[ 5] = endByte[23];
 fpByte[ 6] = endByte[63];
 fpByte[ 7] = endByte[31];
 fpByte[ 8] = endByte[38];
 fpByte[ 9] = endByte[ 6];
 fpByte[10] = endByte[46];
 fpByte[11] = endByte[14];
 fpByte[12] = endByte[54];
 fpByte[13] = endByte[22];
 fpByte[14] = endByte[62];
 fpByte[15] = endByte[30];
 fpByte[16] = endByte[37];
 fpByte[17] = endByte[ 5];
 fpByte[18] = endByte[45];
 fpByte[19] = endByte[13];
 fpByte[20] = endByte[53];
 fpByte[21] = endByte[21];
 fpByte[22] = endByte[61];
 fpByte[23] = endByte[29];
 fpByte[24] = endByte[36];
 fpByte[25] = endByte[ 4];
 fpByte[26] = endByte[44];
 fpByte[27] = endByte[12];
 fpByte[28] = endByte[52];
 fpByte[29] = endByte[20];
 fpByte[30] = endByte[60];
 fpByte[31] = endByte[28];
 fpByte[32] = endByte[35];
 fpByte[33] = endByte[ 3];
 fpByte[34] = endByte[43];
 fpByte[35] = endByte[11];
 fpByte[36] = endByte[51];
 fpByte[37] = endByte[19];
 fpByte[38] = endByte[59];
 fpByte[39] = endByte[27];
 fpByte[40] = endByte[34];
 fpByte[41] = endByte[ 2];
 fpByte[42] = endByte[42];
 fpByte[43] = endByte[10];
 fpByte[44] = endByte[50];
 fpByte[45] = endByte[18];
 fpByte[46] = endByte[58];
 fpByte[47] = endByte[26];
 fpByte[48] = endByte[33];
 fpByte[49] = endByte[ 1];
 fpByte[50] = endByte[41];
 fpByte[51] = endByte[ 9];
 fpByte[52] = endByte[49];
 fpByte[53] = endByte[17];
 fpByte[54] = endByte[57];
 fpByte[55] = endByte[25];
 fpByte[56] = endByte[32];
 fpByte[57] = endByte[ 0];
 fpByte[58] = endByte[40];
 fpByte[59] = endByte[ 8];
 fpByte[60] = endByte[48];
 fpByte[61] = endByte[16];
 fpByte[62] = endByte[56];
 fpByte[63] = endByte[24];
 return fpByte;
}

function getBoxBinary(i) {
 var binary = "";
 switch (i) {
   case 0 :binary = "0000";break;
   case 1 :binary = "0001";break;
   case 2 :binary = "0010";break;
   case 3 :binary = "0011";break;
   case 4 :binary = "0100";break;
   case 5 :binary = "0101";break;
   case 6 :binary = "0110";break;
   case 7 :binary = "0111";break;
   case 8 :binary = "1000";break;
   case 9 :binary = "1001";break;
   case 10 :binary = "1010";break;
   case 11 :binary = "1011";break;
   case 12 :binary = "1100";break;
   case 13 :binary = "1101";break;
   case 14 :binary = "1110";break;
   case 15 :binary = "1111";break;
 }
 return binary;
}
/*
* generate 16 keys for xor
*
*/
function generateKeys(keyByte){
 var key   = new Array(56);
 var keys = new Array();

 keys[ 0] = new Array();
 keys[ 1] = new Array();
 keys[ 2] = new Array();
 keys[ 3] = new Array();
 keys[ 4] = new Array();
 keys[ 5] = new Array();
 keys[ 6] = new Array();
 keys[ 7] = new Array();
 keys[ 8] = new Array();
 keys[ 9] = new Array();
 keys[10] = new Array();
 keys[11] = new Array();
 keys[12] = new Array();
 keys[13] = new Array();
 keys[14] = new Array();
 keys[15] = new Array();
 var loop = [1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1];

 for(i=0;i<7;i++){
   for(j=0,k=7;j<8;j++,k--){
     key[i*8+j]=keyByte[8*k+i];
   }
 }

 var i = 0;
 for(i = 0;i < 16;i ++){
   var tempLeft=0;
   var tempRight=0;
   for(j = 0; j < loop[i];j ++){
     tempLeft = key[0];
     tempRight = key[28];
     for(k = 0;k < 27 ;k ++){
       key[k] = key[k+1];
       key[28+k] = key[29+k];
     }
     key[27]=tempLeft;
     key[55]=tempRight;
   }
   var tempKey = new Array(48);
   tempKey[ 0] = key[13];
   tempKey[ 1] = key[16];
   tempKey[ 2] = key[10];
   tempKey[ 3] = key[23];
   tempKey[ 4] = key[ 0];
   tempKey[ 5] = key[ 4];
   tempKey[ 6] = key[ 2];
   tempKey[ 7] = key[27];
   tempKey[ 8] = key[14];
   tempKey[ 9] = key[ 5];
   tempKey[10] = key[20];
   tempKey[11] = key[ 9];
   tempKey[12] = key[22];
   tempKey[13] = key[18];
   tempKey[14] = key[11];
   tempKey[15] = key[ 3];
   tempKey[16] = key[25];
   tempKey[17] = key[ 7];
   tempKey[18] = key[15];
   tempKey[19] = key[ 6];
   tempKey[20] = key[26];
   tempKey[21] = key[19];
   tempKey[22] = key[12];
   tempKey[23] = key[ 1];
   tempKey[24] = key[40];
   tempKey[25] = key[51];
   tempKey[26] = key[30];
   tempKey[27] = key[36];
   tempKey[28] = key[46];
   tempKey[29] = key[54];
   tempKey[30] = key[29];
   tempKey[31] = key[39];
   tempKey[32] = key[50];
   tempKey[33] = key[44];
   tempKey[34] = key[32];
   tempKey[35] = key[47];
   tempKey[36] = key[43];
   tempKey[37] = key[48];
   tempKey[38] = key[38];
   tempKey[39] = key[55];
   tempKey[40] = key[33];
   tempKey[41] = key[52];
   tempKey[42] = key[45];
   tempKey[43] = key[41];
   tempKey[44] = key[49];
   tempKey[45] = key[35];
   tempKey[46] = key[28];
   tempKey[47] = key[31];
   switch(i){
     case 0: for(m=0;m < 48 ;m++){ keys[ 0][m] = tempKey[m]; } break;
     case 1: for(m=0;m < 48 ;m++){ keys[ 1][m] = tempKey[m]; } break;
     case 2: for(m=0;m < 48 ;m++){ keys[ 2][m] = tempKey[m]; } break;
     case 3: for(m=0;m < 48 ;m++){ keys[ 3][m] = tempKey[m]; } break;
     case 4: for(m=0;m < 48 ;m++){ keys[ 4][m] = tempKey[m]; } break;
     case 5: for(m=0;m < 48 ;m++){ keys[ 5][m] = tempKey[m]; } break;
     case 6: for(m=0;m < 48 ;m++){ keys[ 6][m] = tempKey[m]; } break;
     case 7: for(m=0;m < 48 ;m++){ keys[ 7][m] = tempKey[m]; } break;
     case 8: for(m=0;m < 48 ;m++){ keys[ 8][m] = tempKey[m]; } break;
     case 9: for(m=0;m < 48 ;m++){ keys[ 9][m] = tempKey[m]; } break;
     case 10: for(m=0;m < 48 ;m++){ keys[10][m] = tempKey[m]; } break;
     case 11: for(m=0;m < 48 ;m++){ keys[11][m] = tempKey[m]; } break;
     case 12: for(m=0;m < 48 ;m++){ keys[12][m] = tempKey[m]; } break;
     case 13: for(m=0;m < 48 ;m++){ keys[13][m] = tempKey[m]; } break;
     case 14: for(m=0;m < 48 ;m++){ keys[14][m] = tempKey[m]; } break;
     case 15: for(m=0;m < 48 ;m++){ keys[15][m] = tempKey[m]; } break;
   }
 }
 return keys;
}
var u = '1234'
var p = '1234'
var lt = ' LT-318507-wymVTnxdHIivdYhDVasTwXTNEKnqTI-cas'
var rsa =strEnc(u+p+lt , '1' , '2' , '3')

console.log(rsa)

我这里直接把代码给大家，大家感兴趣可以先尝试直接去写，可以和我写的做比较。 

实现效果

C1BB5938DF9F2190C1BB5938DF9F21906C47B718205114E97CBA49C9BE760421885CBED73DBA20760A8CE596669EA996ECAE08DFB1001AFC0C53B6B482DC1A450D45FA2BFB9C2F07AEF9D3E23DE6C7061D6814B8F1D6CEBC279B336B204A11587914575B59A84A0FB2DA8880EA270330

 我们可以发现，这个结果和网页的结果一样的，说明我们逆向成功了。

四、总结

本文介绍了高校教务系统的密码加密逻辑以及使用JavaScript进行逆向分析的方法。通过学习这些知识，你可以更好地理解密码加密技术的原理，并掌握一定的逆向分析技巧。请注意，逆向分析可能涉及到法律问题，请在合法范围内进行研究和实践。

五、累计更新

争取到到底早日更新30所高校，大家可以在评论区留言。前期更的可能会多一点，有的学校教务系统都没有加密，我这里就不写了，还有，部分学校的教务系统已经和我之前写的是一样的，我也不重复赘述了。

往期作品可以查看专栏

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