用python做youtube自动化下载器 思路
用python做youtube自动化下载器
- 0. 思路
- 1.准备
-
- i.savfrom.net
- 2. 探索并规划获取方式
-
- i.总览
- ii. 获取该网页取到下载url的请求
- iii. 在本地获取请求
- iv.解析请求结果
- v.解析解密后的结果
根据 savefrom条例
本实例及教程只用于学习交流用，权利归savefrom.net所有
0. 思路
使用python从savefrom平台上获取指定youtube视频下载链接进行下载，不过savefrom的数据是用javascript加密的，这也是难度所在
本教程主要介绍制作思路，下一篇会介绍制作python
本教程根据stakoverflow 回答制作
1.准备
i.savfrom.net
一个网站可以免费下载youtube视频
2. 探索并规划获取方式
i.总览
打开https://en.savefrom.net/1-youtube-video-downloader-4/可以看见页面主要就一个from表单输入框和提交按钮组成
ii. 获取该网页取到下载url的请求
在chrome或其他浏览器按F12打开开发者控制台，点开Network选项卡
接下来模拟正常的用户流程，在输入框输入一个youtube视频地址，比如这个https://www.youtube.com/watch?v=IjJmTeBSEzU，然后点击Download提交url获取下载url，然后我们可以发现下面已经出现了下载链接。然后我们在network选项卡内可以发现一个特殊的申请saveform.php(如果没发现可以多提交几次，就会发现每次提交都有这个请求或者看html里的form元素的src地址就是savform.php)
我们就可以确定关于下载链接会出现在这个请求的返回值内。
iii. 在本地获取请求
在本地用IDE的http工具或者python构建出post请求代码，笔者用的是pycharm的httpClient(按2下左Shift，然后输入Tools，然后回车进入菜单，然后点击httpClient下的第一个)
把请求里第二个headers的内容全部复制然后格式化然后构建post请求
然后把下面的formdata的参数也复制进来，记得和headers换行
POST https://en.savefrom.net/savefrom.php
cache-Control: no-cache
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
accept-encoding: gzip, deflate, br
accept-language: zh-CN,zh;q=0.9,en;q=0.8
content-type: application/x-www-form-urlencoded
cookie: lang=en; country=CN; uid=fd94a82a406a8dd4; sfHelperDist=72; reference=14; clickads-e2=90; poropellerAdsPush-e=63; promoBlock=64; helperWidget=92; helperBanner=42; framelessHdConverter=68; inpagePush2=68; popupInOutput=9; _ga=GA1.2.799702638.1610248969; _gid=GA1.2.628904587.1610248969; PHPSESSID=4aojkm49oj7h3de65pekqii337; x-requested-with=; PHPSESSUD=122fb7e10af37e23d99e896fd188744f; _gat_helperWidget=1; _gat_inpagePush2=1
origin: https://en.savefrom.net
pragma: no-cache
referer: https://en.savefrom.net/1-youtube-video-downloader-4/
sec-ch-ua: "Google Chrome";v="87", " Not;A Brand";v="99", "Chromium";v="87"
sec-ch-ua-mobile: ?0
sec-fetch-dest: iframe
sec-fetch-mode: navigate
sec-fetch-site: same-origin
sec-fetch-user: ?1
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36
sf_url=https://www.youtube.com/watch?v=YPvtz1lHRiw&sf_submit=&new=1&lang=en&app=&country=cn&os=Windows&browser=Chrome
如果配置没错，这个时候你运行后会显示出和在浏览器里一样的结果，然后可以发现参数里的sf_url就是需要下载的youtube地址
iv.解析请求结果
把取到的结果保存在本地然后在浏览器打开保存的本地文件，然后弹出一个弹窗后会发现这个页面什么都没有，但其实如果你在console输入window会发现有很多变量和函数，其中就有我们需要的加密后的url和解密函数
经过弹窗提示我们可以发现是这个html的js发现了我们不在他的网站上然后删除了显示下载url的代码所以我们才什么都看不到，打开source选项卡或者用IDE打开源代码查看
扫一下这个源代码，我们可以看见一些加密解密函数，被加密的乱码信息，哈希对照表，和一些奇怪的赋值操作，如图
我们可以看见，js部分由一个大闭包组成
- 第3行到第9行是声明函数
- 第10行是给
$b赋值this也就是window - 第11到第13行是赋值3个变量
- 第14，15行是对变量执行一些操作，这个也是我们重点关注的，毕竟执行加密，解密方法只可能在这
第14，15行格式化后如下
this.$d = $d;
this.$a = $a;
this.$e = $e;
this.$k = $k;
this.$c = $c;
$c = _q($c);
$c = _b($c);
_m($b, $c);
去掉前5行没有意义的变量互换值，加密解密函数存在的范围就在最后3行
$c = _q($c);
$c = _b($c);
_m($b, $c);
然后开始一个个试
先在console里输入第一行
然后就出现了明文，所以我们就确定这个是我们需要的解密函数
接下来输入第二行
发现出现了和上面一模一样的明文，所以这个也是解密函数
接下来输入第三行
发现这个执行了那段代码，这个应该是执行函数，所以我们现在就找到了解密函数位于js部分的最后几行
v.解析解密后的结果
把console里用解密函数解密出的结果复制出来会得到一个JavaScript脚本
(function(){
function del(){while(document.body.firstChild){document.body.removeChild(document.body.firstChild);}};
if(window.location.hostname.search(/(?:^|\.|@)(savefrom\.net|sfrom\.net|savefrom\.com\.au|51\.159\.57\.158|(?:fe\d*|test)-front\.sf-apps\.com)$/i) == -1)
{
alert('Please go to http://savefrom.net/ to get direct links');
del();
return;
}
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var success = false;
try
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var d = window.parent.document;
if(d && d.getElementById)
{
var e = d.getElementById('sf_result');
if(e && e.innerHTML)
{
window.parent.sf.finishRequest(true);;
e.innerHTML = '';
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showResult();
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catch (err) {
showResult();
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})();
我们可以发现里面有个del()删除函数，这就是为什么我们看不到这一段代码在执行后
因为被window.location.hostname.search(/(?:^|\.|@)(savefrom\.net|sfrom\.net|savefrom\.com\.au|51\.159\.57\.158|(?:fe\d*|test)-front\.sf-apps\.com)$/i) == -1检查出不是在他的网站上跑的所以就执行弹窗和del()把解密后的东西删除了
仔细检查这段代码可以发现这一行
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这里面有一长串json文本然后里面就包含我们要的下载链接和其他杂七杂八的东西，在json格式化平台(比如bejson)把这一段json文本输入
可以发现meta主要是视频消息，然后url下就是不同分辨率的视频下载链接了
下一章会讲怎么制作自动python程序