源码地址：https://github.com/Myron1024/m3u8_download
今年上网课很流行，有些在线的课程视频想下载下来到本地看，发现视频的链接是m3u8格式的，下载下来后，提取出视频切片的各个.ts文件的链接，把这些视频片段下载到本地后，却播放不了。于是就花点时间研究研究。网上了解了一下情况，知道视频是加密的， 不过搜了一大圈，都是讲的加密方式为 METHOD=AES-128 的解密方法，可我下载的m3u8文件打开看是 METHOD=QINIU-PROTECTION-10
了解到解密视频需要key和IV， 我们可以看到 IV在m3u8文件里有，每一个.ts文件都有一个对应的IV，#EXT-X-KEY:后面的 IV=**** 就是我们需要用到的 IV了， 可是key却没有，那就只能从网页上找找了，打开控制台，重新加载页面，发现一个 qiniu-web-player.js 在控制台输出了一些配置信息和日志记录，其中 hls.DRMKey 引起了我的注意
数组长度也是16位，刚好加解密用到的key的长度也是16位,, 所以这个应该就是AES加解密要用到的key了，不过需要先转换一下。。
网上的方法 转换步骤为：把数组里每一位数字转换成16进制字符串，然后把16进制字符串转为ASCII码，最终拼接出来的结果就是AES的key了。
C#代码：
private static string getAESKey(string key) { string[] arr = key.Split(","); string aesKey = ""; for (int i = 0; i < arr.Length; i++) { string tmp = int.Parse(arr[i].Trim()).ToString("X"); //10进制转16进制 tmp = HexStringToASCII(tmp); aesKey += tmp; } return aesKey; } /// <summary> /// 十六进制字符串转换为ASCII /// </summary> /// <param name="hexstring">一条十六进制字符串</param> /// <returns>返回一条ASCII码</returns> public static string HexStringToASCII(string hexstring) { byte[] bt = HexStringToBinary(hexstring); string lin = ""; for (int i = 0; i < bt.Length; i++) { lin = lin + bt[i] + " "; } string[] ss = lin.Trim().Split(new char[] { \' \' }); char[] c = new char[ss.Length]; int a; for (int i = 0; i < c.Length; i++) { a = Convert.ToInt32(ss[i]); c[i] = Convert.ToChar(a); } string b = new string(c); return b; }
把js获取的DRMKey数组内容当做字符串传入，获取AES的key
string DRMKey = "11, 22, 33, 44, 55, 66, 77, 88, 99, 00, 111, 111, 111, 111, 111, 111"; string aesKey = getAESKey(DRMKey); Console.WriteLine("aesKey:" + aesKey);
现在AES_KEY和IV都有了，可以加解密了，不过这个IV有点特殊，是32位的，我们需要进行切片取前16位，16位是固定位数，必须这么取。
通过分析页面js代码得知这种AES的加密模式为CBC模式，PaddingMode采用PKCS7.
加密模式、补码方式、key、IV都有了，剩下的就是编码测试了。
下面是C#版的完整代码， Java版请看这里
using System; using System.Collections.Generic; using System.IO; using System.Linq; using System.Net; using System.Security.Cryptography; using System.Text; using System.Text.RegularExpressions; namespace VideoDownload { class Program { private static List<string> error_arr = new List<string>(); static void Main(string[] args) { string DRMKey = "11, 22, 33, 44, 55, 66, 77, 88, 99, 00, 111, 111, 111, 111, 111, 111"; //DRMKey string m3u8Url = "https://XXXXXXX/123.m3u8"; //m3u8在线地址 string savePath = "D:\\VIDEO\\"; //保存的本地路径 string saveFileName = "VIDEO_FILE_NAME"; //保存的文件（夹）名称，如果为空 则使用默认m3u8文件名 try { // 创建本地保存目录 int index = m3u8Url.LastIndexOf("/"); string dirName = string.IsNullOrEmpty(saveFileName) ? m3u8Url.Substring(index + 1) : saveFileName; string finalSavePath = savePath + dirName + "\\"; if (!Directory.Exists(finalSavePath)) { Directory.CreateDirectory(finalSavePath); } // 读取m3u8文件内容 string m3u8Content = HttpGet(m3u8Url); //string m3u8Content = File.ReadAllText("D:/test.m3u8"); string aesKey = getAESKey(DRMKey); //Console.WriteLine("aesKey:" + aesKey); Uri uri = new Uri(m3u8Url); string domain = uri.Scheme + "://" + uri.Authority; //Console.WriteLine("m3u8域名为：" + domain); List<string> tsList = Regex.Matches(m3u8Content, @"\n(.*?.ts)").Select(m => m.Value).ToList(); List<string> ivList = Regex.Matches(m3u8Content, @"IV=(.*?)\n").Select(m => m.Value).ToList(); if (tsList.Count != ivList.Count || tsList.Count == 0) { Console.WriteLine("m3u8Content 解析失败"); } else { Console.WriteLine("m3u8Content 解析完成，共有 " + ivList.Count + " 个ts文件"); for (int i = 0; i < tsList.Count; i++) { string ts = tsList[i].Replace("\n", ""); string iv = ivList[i].Replace("\n", ""); iv = iv.Replace("IV=0x", ""); iv = iv.Substring(0, 16); //去除前缀，取IV前16位 int idx = ts.LastIndexOf("/"); string tsFileName = ts.Substring(idx + 1); try { string saveFilepath = finalSavePath + tsFileName; if (!File.Exists(saveFilepath)) { Console.WriteLine("开始下载ts: " + domain + ts); byte[] encByte = HttpGetByte(domain + ts); if (encByte != null) { Console.WriteLine("开始解密, IV -> " + iv); byte[] decByte = null; try { decByte = AESDecrypt(encByte, aesKey, iv); } catch (Exception e1) { error_arr.Add(tsFileName); Console.WriteLine("解密ts文件异常。" + e1.Message); } if (decByte != null) { //保存视频文件 File.WriteAllBytes(saveFilepath, decByte); Console.WriteLine(tsFileName + " 下载完成"); } } else { error_arr.Add(tsFileName); Console.WriteLine("HttpGetByte 结果返回null"); } } else { Console.WriteLine($"文件 {saveFilepath} 已存在"); } } catch (Exception ee) { error_arr.Add(tsFileName); Console.WriteLine("发生异常。" + ee); } } } } catch (Exception ex) { Console.WriteLine("发生异常。" + ex); } Console.WriteLine("所有操作已完成. 保存目录 " + savePath); if (error_arr.Count > 0) { List<string> list = error_arr.Distinct().ToList(); Console.WriteLine($"其中 共有{error_arr.Count}个文件下载失败："); list.ForEach(x => { Console.WriteLine(x); }); } Console.ReadKey(); } private static string getAESKey(string key) { string[] arr = key.Split(","); string aesKey = ""; for (int i = 0; i < arr.Length; i++) { string tmp = int.Parse(arr[i].Trim()).ToString("X"); //10进制转16进制 tmp = HexStringToASCII(tmp); aesKey += tmp; } return aesKey; } /// <summary> /// 十六进制字符串转换为ASCII /// </summary> /// <param name="hexstring">一条十六进制字符串</param> /// <returns>返回一条ASCII码</returns> public static string HexStringToASCII(string hexstring) { byte[] bt = HexStringToBinary(hexstring); string lin = ""; for (int i = 0; i < bt.Length; i++) { lin = lin + bt[i] + " "; } string[] ss = lin.Trim().Split(new char[] { \' \' }); char[] c = new char[ss.Length]; int a; for (int i = 0; i < c.Length; i++) { a = Convert.ToInt32(ss[i]); c[i] = Convert.ToChar(a); } string b = new string(c); return b; } /// <summary> /// 16进制字符串转换为二进制数组 /// </summary> /// <param name="hexstring">用空格切割字符串</param> /// <returns>返回一个二进制字符串</returns> public static byte[] HexStringToBinary(string hexstring) { string[] tmpary = hexstring.Trim().Split(\' \'); byte[] buff = new byte[tmpary.Length]; for (int i = 0; i < buff.Length; i++) { buff[i] = Convert.ToByte(tmpary[i], 16); } return buff; } /// <summary> /// AES解密 /// </summary> /// <param name="cipherText"></param> /// <param name="Key"></param> /// <param name="IV"></param> /// <returns></returns> public static byte[] AESDecrypt(byte[] cipherText, string Key, string IV) { // Check arguments. if (cipherText == null || cipherText.Length <= 0) throw new ArgumentNullException("cipherText"); if (Key == null || Key.Length <= 0) throw new ArgumentNullException("Key"); if (IV == null || IV.Length <= 0) throw new ArgumentNullException("IV"); // Declare the string used to hold // the decrypted text. byte[] res = null; // Create an AesManaged object // with the specified key and IV. using (AesManaged aesAlg = new AesManaged()) { aesAlg.Key = Encoding.ASCII.GetBytes(Key); aesAlg.IV = Encoding.ASCII.GetBytes(IV); aesAlg.Mode = CipherMode.CBC; aesAlg.Padding = PaddingMode.PKCS7; // Create a decrytor to perform the stream transform. ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV); // Create the streams used for decryption. using (MemoryStream msDecrypt = new MemoryStream(cipherText)) { using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read)) { byte[] tmp = new byte[cipherText.Length + 32]; int len = csDecrypt.Read(tmp, 0, cipherText.Length + 32); byte[] ret = new byte[len]; Array.Copy(tmp, 0, ret, 0, len); res = ret; } } } return res; } public static string HttpGet(string url) { try { HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url); request.Timeout = 20000; var response = (HttpWebResponse)request.GetResponse(); using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8)) { return reader.ReadToEnd(); } } catch (Exception ex) { Console.Write("HttpGet 异常，" + ex.Message); Console.Write(ex); return ""; } } public static byte[] HttpGetByte(string url) { try { byte[] arraryByte = null; HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url); request.Timeout = 20000; request.Method = "GET"; using (WebResponse wr = request.GetResponse()) { int length = (int)wr.ContentLength; using (StreamReader reader = new StreamReader(wr.GetResponseStream(), Encoding.UTF8)) { HttpWebResponse response = wr as HttpWebResponse; Stream stream = response.GetResponseStream(); //读取到内存 MemoryStream stmMemory = new MemoryStream(); byte[] buffer1 = new byte[length]; int i; //将字节逐个放入到Byte 中 while ((i = stream.Read(buffer1, 0, buffer1.Length)) > 0) { stmMemory.Write(buffer1, 0, i); } arraryByte = stmMemory.ToArray(); stmMemory.Close(); } } return arraryByte; } catch (Exception ex) { Console.Write("HttpGetByte 异常，" + ex.Message); Console.Write(ex); return null; } } } }
新建个控制台应用，代码复制过去，改一下最上面的四个参数值就可以运行。本来想做个桌面应用程序的，结果嫌麻烦，费时间就没做了。哪位看官要是有时间可以做个桌面程序方便操作，另外可以加上多线程去下载会快一些。下载解密完之后的ts文件后，使用其他工具合并ts文件或者用windows自带cmd执行以下命令也可以合并文件
copy /b D:\VIDEO\*.ts D:\VIDEO\newFile.ts
参考资料：
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