C#•2y ago

❔ ✅ AES - Padding is invalid and cannot be removed

I am attempting to quickly encrypt a set of files using AES, but I'm getting the above error when decrypting. I'm not sure if it's encryption or decryption that's wrong, but I've tried and googled everything I can think of, but nothing seems to works. Can anyone tell me what's wrong with this code: (also tried reading one-byte at a time, but with the same results)

17 Replies

Arch Leaders•2y ago

public static Task Encrypt(string key, string path, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
{
    using Aes aes = Aes.Create();
    byte[] aesKey = SHA256.HashData(Encoding.UTF8.GetBytes(key));
    ICryptoTransform transform = aes.CreateEncryptor(aesKey, "nkar9l.u&tal-/a4"u8.ToArray());

    return Parallel.ForEachAsync(Directory.EnumerateFiles(path, searchPattern, searchOption), (file, cancellationToken) => {
        using (FileStream fs = File.OpenRead(file)) {
            using FileStream wfs = File.Create(EncodePath(path, file));
            using CryptoStream encryptor = new(wfs, transform, CryptoStreamMode.Write);
            byte[] buffer = new byte[0x400];
            int read = 0;

            while ((read = fs.Read(buffer, 0, buffer.Length)) > 0) {
                encryptor.Write(buffer, 0, read);
            }
        }

        File.Delete(file);
        _ = Task.Run(() => Console.WriteLine($"-> '{file}'"), cancellationToken);
        return new();
    });
}

public static Task Encrypt(string key, string path, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
{
    using Aes aes = Aes.Create();
    byte[] aesKey = SHA256.HashData(Encoding.UTF8.GetBytes(key));
    ICryptoTransform transform = aes.CreateEncryptor(aesKey, "nkar9l.u&tal-/a4"u8.ToArray());

    return Parallel.ForEachAsync(Directory.EnumerateFiles(path, searchPattern, searchOption), (file, cancellationToken) => {
        using (FileStream fs = File.OpenRead(file)) {
            using FileStream wfs = File.Create(EncodePath(path, file));
            using CryptoStream encryptor = new(wfs, transform, CryptoStreamMode.Write);
            byte[] buffer = new byte[0x400];
            int read = 0;

            while ((read = fs.Read(buffer, 0, buffer.Length)) > 0) {
                encryptor.Write(buffer, 0, read);
            }
        }

        File.Delete(file);
        _ = Task.Run(() => Console.WriteLine($"-> '{file}'"), cancellationToken);
        return new();
    });
}

public static Task Decrypt(string key, string path, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
{
    using Aes aes = Aes.Create();
    byte[] aesKey = SHA256.HashData(Encoding.UTF8.GetBytes(key));
    ICryptoTransform transform = aes.CreateDecryptor(aesKey, "nkar9l.u&tal-/a4"u8.ToArray());

    return Parallel.ForEachAsync(Directory.EnumerateFiles(path, searchPattern, searchOption), (file, cancellationToken) => {
        using (FileStream fs = File.OpenRead(file)) {
            using FileStream wfs = File.Create(DecodePath(path, file));
            using CryptoStream decryptor = new(fs, transform, CryptoStreamMode.Read);
            byte[] buffer = new byte[0x400];
            int read = 0;

            while ((read = decryptor.Read(buffer, 0, buffer.Length)) > 0) { // <- error occurs here, usually part way through a file
                wfs.Write(buffer, 0, read);
            }
        }

        File.Delete(file);
        _ = Task.Run(() => Console.WriteLine($"-> '{file}'"), cancellationToken);
        return new();
    });
}

public static Task Decrypt(string key, string path, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
{
    using Aes aes = Aes.Create();
    byte[] aesKey = SHA256.HashData(Encoding.UTF8.GetBytes(key));
    ICryptoTransform transform = aes.CreateDecryptor(aesKey, "nkar9l.u&tal-/a4"u8.ToArray());

    return Parallel.ForEachAsync(Directory.EnumerateFiles(path, searchPattern, searchOption), (file, cancellationToken) => {
        using (FileStream fs = File.OpenRead(file)) {
            using FileStream wfs = File.Create(DecodePath(path, file));
            using CryptoStream decryptor = new(fs, transform, CryptoStreamMode.Read);
            byte[] buffer = new byte[0x400];
            int read = 0;

            while ((read = decryptor.Read(buffer, 0, buffer.Length)) > 0) { // <- error occurs here, usually part way through a file
                wfs.Write(buffer, 0, read);
            }
        }

        File.Delete(file);
        _ = Task.Run(() => Console.WriteLine($"-> '{file}'"), cancellationToken);
        return new();
    });
}

Scratch•2y ago

did you just share your hardcoded encryption key?

mtreit•2y ago

That's the IV I think

Scratch•2y ago

oh okay I don't aes @Arch Leaders what are you trying to make with this? from our perspective it sure looks like ransomware

mtreit•2y ago

Although you should probably use aes.IV and not something hardcoded Anyway...

Arch Leaders•2y ago

Just personal encryption of files and some practice for a security model I'm working on elsewhere. Didn't really understand it, so I just put 16 random bytes there xD

Arch Leaders•2y ago

Here's the entire project if it helps with that concern ~~with my super secret key totally visible this time~~ I can also plop it on github if need be, just want to solve this weird issue.

mtreit•2y ago

@Arch Leaders you are hitting that error because the code is not thread safe. You can't share the ICryptoTransform across multiple threads concurrently. Give each parallel task it's own instance of ICryptoTransform and it should fix it. Also just as an aside, if you want to do this more "correctly" the right thing to do is to store the IV along with the ciphertext and then calculate an HMAC on the combined ciphertext + IV and then store that as well. Then validate the HMAC on decrypt.

Arch Leaders•2y ago

Ah splendid, thanks!! Ah good to know thanks, I'll look into that 👍

Unknown User•2y ago

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mtreit•2y ago

lol

Unknown User•2y ago

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mtreit•2y ago

Because AES and RSA are not even remotely the same thing

Unknown User•2y ago

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mtreit•2y ago

You would never use RSA for encrypting arbitrary files so I doubt it's relevant for the OP scenario

Unknown User•2y ago

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Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ✅ AES - Padding is invalid and cannot be removed