large files silently truncated when encrypting/decrypting concurrently

[dean-long]

Steps to reproduce (Windows 10):
0. mount cryptomator volume Z:

1. create large file (about 1GB in my case) on local disk, T:\local1.dat
2. copy T:\local1.dat to Z:\
3. rename Z:\local1.dat to Z:\local2.dat
4. copy Z:\local2.dat to T:\ and copy T:\local1.dat to Z:\ at the same time, causing concurrent encryption and decryption
5. local decrypted file T:\local2.dat should be the same as original local1.dat, but is often truncated, with no error in cryptomator.log. Truncated size seems unpredictable. I get a different size every time.

[overheadhunter]

Thanks for reporting, this is obviously a bug, not a feature ;)

Another thing to be retested on the layered-io branch.

[markuskreusch]

I am sorry but I could not reproduce the problem on my local machine. Did you have anything else in your setup which could be considered "special" or did you really just copy from a local hard disk to a cryptomator vault which also resides on your local hard disk?

[dean-long]

Hi Markus, I did a clean install of the 0.10 x64 binary from cryptomator.org on a different machine. The problem reproduces on the new machine. Here is the script I used:

dd if=/dev/zero of=xxx.dat bs=1024k count=500
rm -f Z:/yyy.dat
cp xxx.dat Z:/yyy.dat
rm -f Z:/zzz.dat
cp xxx.dat Z:/zzz.dat &
sleep 15 # wait for encryption to get started
cp Z:/yyy.dat .
cmp xxx.dat yyy.dat

The key to reproducing seems to be making sure that the encryption and decryption are happening at the same time. On the first machine, I reproduced it in WIndows Explorer, pausing the decryption until the encryption showed up in throughput graph, then resume the decryption so they ran concurrently.

[dean-long]

Could it have been fixed by this commit:
c03bdd8

[overheadhunter]

@markuskreusch: Did you test after c03bdd8?
@atodtoa: I assume you tested using some 0.10.x release? Can I send you a download link to our current HEAD? (How can I contact you?) Or can you build the software from sources yourself?

[dean-long]

@overheadhunter: Yes, it was 0.10.1. I'm having trouble building it myself, so please send me a download link. I joined Gitter chat.

[overheadhunter]

@atodtoa confirms this isn't reproducable any longer. Thus I will close this now and change milestone to 1.0