I am trying to extract a password protected .zip which has a .txt document (Say Congrats.txt for this case). Now Congrats.txt has text in it thus its not 0kb in size. Its placed in a .zip (For the sake of the thread lets name this .zip zipv1.zip) with the password dominique for the sake of this thread. That password is stored among other words and names within another .txt (Which we'll name it as file.txt for the sake of this question).
Now if I run the code below by doing python Program.py -z zipv1.zip -f file.txt (Assuming all these files are in the same folder as Program.py) my program displays dominique as the correct password for the zipv1.zip among the other words/passwords in file.txt and extracts the zipv1.zip but the Congrats.txt is empty and has the size of 0kb.
Traktor 2 Crack Zip Password --
So to solve this I tried reading zipfile's documentation where I found out that if a password doesn't match the .zip it throws a RuntimeError. So I did changed except: in the code to except RuntimeError: and got this error when trying to unzip zipv1.zip:
The same results happpen though; password was found in file.txt, zipv1.zip was extracted but Congrats.txt was empty and 0kb in size. So I ran the program again, but for zipv2.zip this time and got this as a result:
Now after implementing with zipfile.ZipFile(zip_filename, 'r') as zip_file: for some unknown and weird reason; the program can read/process a small word list/password list/dictionary but can't if its large(?).
What I mean by that is that say a .txt document is present in zipv1.zip; named Congrats.txt with the text You have cracked the .zip!. The same .txt is present in zipv2.zip aswell, but this time placed in a folder named ZIP Contents then zipped/password protected. The password is dominique for both of the zips.
This continues to occur regardless of different word/password lists. Tried generating more .zips with the same Congrats.txt but with different passwords from different word lists/password lists/dictionaries. Same method; a larger and smaller version of the .txt was used and same results as above were achieved.
BUT I did find out that if I cut out the first 2k words in John The Ripper.txt and make a new .txt; say John The Ripper v2.txt; the .zip is extracted successfully, Extracted folder appears and Congrats.txt is present with the text inside it. So I believe it has to do with the lines after the password is at. So in this case Line 1968; where the script doesn't stop after Line 1968? I am not sure why does this work though. It isn't a solution but a step towards the solution I guess...
Looking at ZipFile.extractall code, it tries to extract all the members. The 1st raises an exception, so it starts to be clearer why it behaves the way it does. But why the behavioral difference, when attempting to extract items using 2 wrong passwords? As seen in the tracebacks of the 2 different thrown exception types, the answer lies somewhere at the end of ZipFile.open.
Before encrypting a file in the archive, 12 random bytes are first prepended to its compressedcontents and the resulting bytestream is then encrypted. Upon decryption, the first 12 bytesneed to be discarded. According to the specification, this is done in order to render a plaintextattack on the data ineffective.The specification also states that out of the 12 prepended bytes, only the first 11 are actuallyrandom, the last byte is equal to the high order byte of the CRC-32 of the uncompressedcontents of the file. This gives the ability to quickly verify whether a given password is correctby comparing the last byte of the decrypted 12 byte header to the high order byte of the actualCRC-32 value that is included in the local file header. This can be done before decrypting therest of the file.
The algorithm weakness: due to the fact that differentiation is done on one byte only, for 256 different (and carefully chosen) wrong passwords, there will be one (at least) that will generate the same number as the correct password.
I've submitted [GitHub]: python/cpython - [3.6] bpo-36247: zipfile - extract truncates (existing) file when bad password provided (zip encryption weakness) which was closed for branch 3.6 (which is in security fixes only mode). Not sure what its outcome it's going to be (in other branches), but anyway, it won't be available anytime soon (in the next months, let's say).
Last month I wrote a column in which I discussed my attempts at cracking passwords in a lab environment. I had intended for the blog post to be a thought exercise. I constantly hear people recommending the use of long and complex passwords, and I wanted to find out just how much of a difference length and complexity made. I wasn't just interested in mathematical theory, but also in real-world practicality.
Shortly after that particular blog post went live, it was flooded with comments from people stating that the exercise was not representative of real -world cracking because tools and methods exist that do away with the need for a brute force crack. Many of these comments specifically referenced rainbow tables.
I have always tried to keep the content in my blog posts honest, so I have to confess that I had never heard of rainbow tables. It kind of makes sense if you stop and think about it though. Much of my IT education has come from Microsoft certification classes and Microsoft isn't about to include techniques for cracking Windows passwords in their curriculum.
Most brute-force cracking utilities generate passwords one at a time and use those passwords in sequential cracking attempts. As you probably saw in my previous article, this approach is extremely computationally intensive and time consuming.
Another approach that has been used is to generate all of the possible password combinations ahead of time and then store them in a table. That way the cracking utility can simply reference the table rather than having to go through the effort of a brute force crack. While this approach sounds good in theory, there are a couple of problems with it. First, it can take a long time to create the table entries. Second, it could take an impossibly large amount of space to store the table data.
Rainbow tables are something of a compromise between these two techniques. Rainbow tables are based on the idea that many systems store passwords in a database. Of course storing the passwords in plain text would not be very secure, so the passwords are stored as non-reversible hashes.
Rainbow tables are arranged in columns of chains (which aren't actually stored anywhere). Because of the way that these columns are arranged it is simple to tell whether a password hash exists within any of the columns. Once the correct column is located then deriving the password is simply a matter of working through the hash and reduction functions for that column. This process allows complex passwords to be cracked very quickly.
What Got Overlooked?Most of the comments that I got in relation to my previous article seemed to assume that I based the article on Windows passwords. I didn't. The article was based on the idea of performing a brute force crack on a ZIP file, not on a Windows password. I wanted to get a general feel for the impact that password length and complexity had on a brute force crack. Even so, I think that it is fair to consider the impact that rainbow tables might have on cracking zip file passwords.
Rainbow tables don't work for ZIP files for one very simple reason. Rainbow tables work because the password hash is stored on the system that is being cracked. This hash is the key to making the whole thing work.
Zip files do not store their passwords as a hash. Password-protected ZIP files are encrypted, and the password is the encryption key. As such, rainbow tables do not work for cracking ZIP files because there is no password hash that can be retrieved. 2ff7e9595c
Comments