Can't extract encrypted 7z LZMA2 files

[ciriousjoker]

I have an encrypted 7zip archive (linked below) encrypted with the password "dontgoout", but whenever I try to extract it, it throws an error at MoveToNextEntry.

Here's a screenshot of the stack trace: https://gyazo.com/6fb0b0c0731d6e23d04a26e301cc2dbe

I created the archive using the 7zip client for Windows using these settings: https://gyazo.com/ca4e67e6a259d79cdf0675dc42fd8268

Original name was 0.tmp, but Github only allows zip files. 0.tmp.encrypted.zip

Extracting the same archive without any password works perfectly fine and I can extract the encrypted 7z archive using the 7zip desktop client, so this has to be a bug in the library (Or I'm just too dumb for life and I missed something I should have done)

Here's the code I used to extract that archive:

SharpCompress.Readers.ReaderOptions test = new SharpCompress.Readers.ReaderOptions();
test.LookForHeader = true;
test.LeaveStreamOpen = false;
test.Password = "dontgoout";

var archive = SevenZipArchive.Open(filename, test);

if (!archive.IsComplete)
{
    MessageBox.Show("One of the downloaded resources is corrupt, please try again.");
    return;
}

long totalbytes = archive.TotalUncompressSize;
long processedbytes = 0;

var reader = archive.ExtractAllEntries();

while (reader.MoveToNextEntry()) // <-- Here it crashes
{
    if (!reader.Entry.IsDirectory)
    {

[adamhathcock]

I was about to say "sharpcompress doesn't support encrypted 7zip files" but honestly I can't remember.

However, the error you got is fixable because it's using a stream that doesn't support seeking though 7zip requires seeking.

[ciriousjoker]

But if the library requires seekable streams (which totally makes sense the way 7z works), why did it work with unencrypted files? I mean they'd have to be seekable too, right?

[ciriousjoker]

Woops

[adamhathcock]

It must be that the decryption code just needs to know the length for some reason and it's using a different stream class.

The class with the error is one I wrote for the purpose of ensuring no seekable stream was used in other parts of the code.

I haven't done much with the 7zip code personally. I really hate the 7zip archive format.

[ciriousjoker]

Can you point me in the right direction please? I tried using your API examples, but they only seem to work with zip archives ..

(Aka replacing var archive = ...; with var archive = ArchiveFactory.Open(...); doesn't work either)

SevenZipArchive.Open(new FileStream(...)); also didn't work

[adamhathcock]

It's not going to work without a code change. You're going to get the exception you posted always with that encrypted 7zip file

[ciriousjoker]

So I'd have to fix your library? Or are you saying that my encrypted 7zip file is broken?

By the way, no matter what 7zip file I use (encrypted or not doesn't matter), I get this weird thing in the locals tab:

https://gyazo.com/363d6b37b9dd0ff79df69d602d04fa52

Not sure if it has something to do with this error, but it always throws that error. However, with unencrypted 7z files it still extracts the whole thing

[adamhathcock]

I have a feeling encrypted 7zip just isn't supported. I don't recall putting that in the supported formats matrix

[ciriousjoker]

Ye, I just assumed that encrypted 7zips wouldn't make a difference to the 7z.dll ...

Anyway, I "fixed" it now by encrypting the final 7z with AES. For my purposes that's acceptable

[adamhathcock]

This code doesn't used the 7z dll. That's why he behavior is different than other libraries as others do use the native dll.