[C#/Java] 針對 QINIU-PROTECTION-10 的m3u8視頻文件解密

源碼地址：https://github.com/Myron1024/m3u8_download

 

今年上網課很流行，有些在線的課程視頻想下載下來到本地看，發現視頻的鏈接是m3u8格式的，下載下來后，提取出視頻切片的各個.ts文件的鏈接，把這些視頻片段下載到本地后，卻播放不了。於是就花點時間研究研究。網上了解了一下情況，知道視頻是加密的， 不過搜了一大圈，都是講的加密方式為 METHOD=AES-128 的解密方法，可我下載的m3u8文件打開看是 METHOD=QINIU-PROTECTION-10

 

了解到解密視頻需要key和IV， 我們可以看到 IV在m3u8文件里有，每一個.ts文件都有一個對應的IV，#EXT-X-KEY:后面的 IV=**** 就是我們需要用到的 IV了， 可是key卻沒有，那就只能從網頁上找找了，打開控制台，重新加載頁面，發現一個 qiniu-web-player.js 在控制台輸出了一些配置信息和日志記錄，其中 hls.DRMKey 引起了我的注意

 

  

數組長度也是16位，剛好加解密用到的key的長度也是16位,, 所以這個應該就是AES加解密要用到的key了，不過需要先轉換一下。。

網上的方法 轉換步驟為：把數組里每一位數字轉換成16進制字符串，然后把16進制字符串轉為ASCII碼，最終拼接出來的結果就是AES的key了。

C#代碼：

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進制轉16進制
        tmp = HexStringToASCII(tmp);
        aesKey += tmp;
    }
    return aesKey;
}

/// <summary>
/// 十六進制字符串轉換為ASCII
/// </summary>
/// <param name="hexstring">一條十六進制字符串</param>
/// <returns>返回一條ASCII碼</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獲取的DRMKey數組內容當做字符串傳入，獲取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);

 

現在AES_KEY和IV都有了，可以加解密了，不過這個IV有點特殊，是32位的，我們需要進行切片取前16位，16位是固定位數，必須這么取。

通過分析頁面js代碼得知這種AES的加密模式為CBC模式，PaddingMode采用PKCS7.

加密模式、補碼方式、key、IV都有了，剩下的就是編碼測試了。

 

下面是C#版的完整代碼， Java版請看這里

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在線地址
            string savePath = "D:\\VIDEO\\";                //保存的本地路徑
            string saveFileName = "VIDEO_FILE_NAME";        //保存的文件（夾）名稱，如果為空 則使用默認m3u8文件名

            try
            {
                // 創建本地保存目錄
                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);
                }

                // 讀取m3u8文件內容
                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域名為：" + 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 解析失敗");
                }
                else
                {
                    Console.WriteLine("m3u8Content 解析完成，共有 " + ivList.Count + " 個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);   //去除前綴，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("開始下載ts: " + domain + ts);
                                byte[] encByte = HttpGetByte(domain + ts);
                                if (encByte != null)
                                {
                                    Console.WriteLine("開始解密, IV -> " + iv);
                                    byte[] decByte = null;
                                    try
                                    {
                                        decByte = AESDecrypt(encByte, aesKey, iv);
                                    }
                                    catch (Exception e1)
                                    {
                                        error_arr.Add(tsFileName);
                                        Console.WriteLine("解密ts文件異常。" + e1.Message);
                                    }
                                    if (decByte != null)
                                    {
                                        //保存視頻文件
                                        File.WriteAllBytes(saveFilepath, decByte);
                                        Console.WriteLine(tsFileName + " 下載完成");
                                    }
                                }
                                else
                                {
                                    error_arr.Add(tsFileName);
                                    Console.WriteLine("HttpGetByte 結果返回null");
                                }
                            }
                            else
                            {
                                Console.WriteLine($"文件 {saveFilepath} 已存在");
                            }
                        }
                        catch (Exception ee)
                        {
                            error_arr.Add(tsFileName);
                            Console.WriteLine("發生異常。" + ee);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("發生異常。" + ex);
            }

            Console.WriteLine("所有操作已完成. 保存目錄 " + savePath);
            if (error_arr.Count > 0)
            {
                List<string> list = error_arr.Distinct().ToList();
                Console.WriteLine($"其中 共有{error_arr.Count}個文件下載失敗：");
                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進制轉16進制
                tmp = HexStringToASCII(tmp);
                aesKey += tmp;
            }
            return aesKey;
        }

        /// <summary>
        /// 十六進制字符串轉換為ASCII
        /// </summary>
        /// <param name="hexstring">一條十六進制字符串</param>
        /// <returns>返回一條ASCII碼</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進制字符串轉換為二進制數組
        /// </summary>
        /// <param name="hexstring">用空格切割字符串</param>
        /// <returns>返回一個二進制字符串</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 異常，" + 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();
                        //讀取到內存
                        MemoryStream stmMemory = new MemoryStream();
                        byte[] buffer1 = new byte[length];
                        int i;
                        //將字節逐個放入到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 異常，" + ex.Message);
                Console.Write(ex);
                return null;
            }
        }
    }
}

新建個控制台應用，代碼復制過去，改一下最上面的四個參數值就可以運行。本來想做個桌面應用程序的，結果嫌麻煩，費時間就沒做了。哪位看官要是有時間可以做個桌面程序方便操作，另外可以加上多線程去下載會快一些。下載解密完之后的ts文件后，使用其他工具合並ts文件或者用windows自帶cmd執行以下命令也可以合並文件

copy /b D:\VIDEO\*.ts D:\VIDEO\newFile.ts

 

參考資料：

python爬蟲---破解m3u8 加密