如何解密AES-128加密的m3u8 TS文件 [英] How to decrypt AES-128 encrypted m3u8 TS files

问题描述

我们要解密 AES-128 加密的 m3u8 TS 文件.这是我们的 .m3u8 文件

we want to decrypt AES-128 encrypted m3u8 TS files. here is our .m3u8 file

#EXTM3U
#EXT-X-TARGETDURATION:12
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-KEY:METHOD=AES-128,URI="enc.key?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk"
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:6.000,
s-1-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:6.000,
s-2-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:6.000,
s-3-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:12.000,
s-4-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk

我们有 enc.key 文件和对 'enc.key' 的服务器响应，即 DVQpuWrxZLd2nCTTxAysIg==

we have both enc.key file and the server response to 'enc.key' that is DVQpuWrxZLd2nCTTxAysIg==

我们正在使用这些 C# 函数进行解密，但我们不知道如何找到盐或块大小?或者基本上我们是在以正确的方式做这件事?

we are using these C# functions for decryption but we don't know how to find salt or block size ? or basically we are doing it in correct way ?

 public static void  DecryptFile(string inputFile, string output,string password)
        {

            byte[] bytesToBeDecrypted = File.ReadAllBytes(inputFile);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
            byte[] bytesDecrypted = AES_Decrypt(bytesToBeDecrypted, passwordBytes);


            File.Delete(inputFile);


            File.WriteAllBytes(output, bytesDecrypted);
        }


        public static byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;

            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.
            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 128;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;
                    AES.Padding = PaddingMode.PKCS7;
                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

推荐答案

这里已经有一个类似的问题(找不回来了)

There was already a similar quesion here (unable to find it back)

如何找到盐或块大小

查看您的 EXT-X-KEY 标头.它指出 AES-128，因此您必须使用 AES-128(这是密钥大小，块大小始终为 128 位).

Look at your EXT-X-KEY header. It states AES-128, so you will have to use AES-128 (it's the key size, block size is always 128 bit).

根据 RFC，默认使用带有 Pkcs7 填充的 CBC 模式.

According to the RFC by default CBC mode with Pkcs7 padding is used.

4.3.2.4 部分.EXT-X-KEY进一步说明:初始化向量(IV)属性值或媒体序列号作为IV

所以 IV 应该出现在 EXT-X-KEY 标头中.如果不是，则使用序列号(这对 CBC 来说是个糟糕的主意，但事实就是如此).

So the IV should be present in the EXT-X-KEY header. If not, the sequence number is used (which is terrible idea for CBC, but this is how it is).

或者基本上我们正在以正确的方式进行

or basically we are doing it in correct way

基本上看起来没问题(除了盐和钥匙).我不确定什么是加密密钥.来自服务器的编码响应有 16 位(128 位)，所以我认为这可能是关键(您必须自己找出)

Basically it looks ok (except the salt and key). I am not sure what is the encryption key. The encoded response from the server has 16 bites (128 bits) so I'd assume that can be the key (that you will have to find out yourself)

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