1）博主最近想写一个类似小视频的webApp项目
爬取美拍的时候发现竟然找不到video标签，这样就影响了我获取视频地址啊
仔细看看网页源码发现发现原来视频地址藏在元素身上了
image.png
但是这个视频地址是加密了的？怎么办？看看美拍的请求，发现解密方法藏在js中，也就是说 解密是靠前端解密的
var d = a("jquery")
, e = a("support")
, f = a("constants")
, g = a("base64")
, h = "substring"
, i = "split"
, j = "replace"
, k = "substr";
b.decodeMp4 = {
getHex: function(a) {
return {
str: a[h](4),
hex: a[h](0, 4)[i]("").reverse().join("")
}
},
getDec: function(a) {
var b = parseInt(a, 16).toString();
return {
pre: b[h](0, 2)[i](""),
tail: b[h](2)[i]("")
}
},
substr: function(a, b) {
var c = a[h](0, b[0])
, d = a[k](b[0], b[1]);
return c + a[h](b[0])[j](d, "")
},
getPos: function(a, b) {
return b[0] = a.length - b[0] - b[1],
b
},
decode: function(a) {
var b = this.getHex(a)
, c = this.getDec(b.hex)
, d = this[k](b.str, c.pre);
return g.atob(this[k](d, this.getPos(d, c.tail)))
}
};
后期经过加工改造
;(function(base64){
var substring='substring',
split='split',
reverse='reverse',
join='join',
toString='toString',
substr='substr',
replace='replace',
fn={
getHex: function(str) {//获取前4位标记数字
return {
str: str[substring](4),//排除前4位字符串
hex: str[substring](0, 4)[split]("")[reverse]()[join]("")//前4位倒序
}
},
getDec: function(str) {//获取混淆字符位置坐标
str = parseInt(str, 16)[toString]();//前4位倒序的16进制
//str[substring](0, 2)[split]("");
return {
pre: str[substring](0, 2)[split](""),//前面坐标
tail: str[substring](2)[split]("")//后面坐标
}
},
delStr: function(str, pos) {//混淆的字符抽取
var s = str[substring](0, pos[0]),
del = str[substr](pos[0], pos[1]);//需替换的字符
return s + str[substring](pos[0])[replace](del, "");//返回替换完成后的base64字符串
},
getPos: function(str, pos) {
return [str.length - pos[0] - pos[1],pos[1]];
},
decode: function(str) {//解密
var sh = this.getHex(str),//获取前4位标记数字
pos = this.getDec(sh.hex),//获取混淆位置坐标
d = this.delStr(sh.str, pos.pre);//前面混淆的字符抽取
d=this.delStr(d, this.getPos(d, pos.tail));
return decodeURIComponent(escape(this.atob(d)));//base64转成utf-8(兼容中文) atob
},
encode:function(str){//加密
var base64=this.btoa(unescape(encodeURIComponent(str))),//转换成base64格式
random=this.getRanNum(base64),//获取16进制是4位数的随机字符
pos = this.getDec(random);//获取混淆位置坐标
base64 = this.addStr(base64, pos);//插入混淆字符
//console.log(random,pos)
return random[toString]()[split]("")[reverse]()[join]("")+base64;
},
addStr: function(str, pos) {//混淆的字符插入
var r1=this.getRanStr(pos.pre[1]),//获取随机字符串(前)
r2=this.getRanStr(pos.tail[1]),//获取随机字符串(后)
pre=this.insertStr(str,r1,pos.pre[0]),//插入随机字符串(前)
tail=pre.length - pos.tail[0];
str=this.insertStr(pre,r2,tail);//插入随机字符串(后)
return str;
},
atob:function(src){//解密
//用一个数组来存放解码后的字符。
var str=new Array();
var ch1, ch2, ch3, ch4;
var pos=0;
//过滤非法字符，并去掉'='。
src=src.replace(/[^A-Za-z0-9\+\/]/g, '');
//decode the source string in partition of per four characters.
while(pos+4<=src.length){
ch1=this.deKey[src.charCodeAt(pos++)];
ch2=this.deKey[src.charCodeAt(pos++)];
ch3=this.deKey[src.charCodeAt(pos++)];
ch4=this.deKey[src.charCodeAt(pos++)];
str.push(String.fromCharCode(
(ch1<<2&0xff)+(ch2>>4), (ch2<<4&0xff)+(ch3>>2), (ch3<<6&0xff)+ch4));
}
//给剩下的字符进行解码。
if(pos+1<src.length){
ch1=this.deKey[src.charCodeAt(pos++)];
ch2=this.deKey[src.charCodeAt(pos++)];
if(pos<src.length){
ch3=this.deKey[src.charCodeAt(pos)];
str.push(String.fromCharCode((ch1<<2&0xff)+(ch2>>4), (ch2<<4&0xff)+(ch3>>2)));
}else{
str.push(String.fromCharCode((ch1<<2&0xff)+(ch2>>4)));
}
}
//组合各解码后的字符，连成一个字符串。
return str.join('');
},
btoa:function(src){//加密
//用一个数组来存放编码后的字符，效率比用字符串相加高很多。
var str=new Array();
var ch1, ch2, ch3;
var pos=0;
//每三个字符进行编码。
while(pos+3<=src.length){
ch1=src.charCodeAt(pos++);
ch2=src.charCodeAt(pos++);
ch3=src.charCodeAt(pos++);
str.push(this.enKey.charAt(ch1>>2), this.enKey.charAt(((ch1<<4)+(ch2>>4))&0x3f));
str.push(this.enKey.charAt(((ch2<<2)+(ch3>>6))&0x3f), this.enKey.charAt(ch3&0x3f));
}
//给剩下的字符进行编码。
if(pos<src.length){
ch1=src.charCodeAt(pos++);
str.push(this.enKey.charAt(ch1>>2));
if(pos<src.length){
ch2=src.charCodeAt(pos);
str.push(this.enKey.charAt(((ch1<<4)+(ch2>>4))&0x3f));
str.push(this.enKey.charAt(ch2<<2&0x3f), '=');
}else{
str.push(this.enKey.charAt(ch1<<4&0x3f), '==');
}
}
//组合各编码后的字符，连成一个字符串。
return str.join('');
},
insertStr:function(str,addstr,pos){//往指定位置插入字符串
return str[substring](0,pos)+addstr+str[substring](pos);
},
getRanNum:function(str){//获取16进制是4位数的4位随机字符
var ranArr=[];
;(function(){
var n='',
length=str.length;
/** 4101开始16进制是4位数 **/
for(var i=4101;i<=9999;i++){//找出所有符合要求的16进制4位数
n=i[toString](16);//10转成16
if(length>=8&&!(Math.floor(i/100)%10===0||i%10===0)&&n.length===4){
//正常的base64编码长度大于8才前后加混淆字符
//console.log(i,n);
if(Math.floor(i/1000)<=length/2&&Math.floor(i%100/10)<=length/2){//混淆位置不能大于长度一半
ranArr.push(n);
}
}else if(i%100===0&&n.length===4){//只在前面插入混淆字符
if(Math.floor(i/1000)<=length){//混淆位置不能大于长度
ranArr.push(n);
}
}
}
}());
var length=ranArr.length,
ran = Math.round(Math.random()*(length-1));
return ranArr[ran];
},
enKey:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
deKey: new Array(
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
),
getRanStr:function(num){//获取指定个数随机字符串
var key=this.enKey.split("");
length=key.length,
res = "";
for(; num-- ;) {
var id = Math.round(Math.random()*(length-1));
res += key[id];
}
return res;
}
}
base64.tranCode=fn;
window.base64=base64;
}(window.base64||{}));
此方法包括 解密以及加密
window.base64.tranCode.decode(str) //解密
image.png
