The libzc library is a simple zip cracking library. It also comes with a command line tool called 'yazc' (Yet Another Zip Cracker).
The following packages are required (following example is for Ubuntu):
sudo apt install -y autoconf libtool zlib1g-dev pkg-config
Unit tests require linking with libcheck
Just clone, configure, compile and install.
git clone https://github.com/mferland/libzc.git
cd libzc
./autogen.sh
./configure CFLAGS='-O3 -ffast-math -march=native -mtune=native'
make
sudo make install
There are currently 3 attack modes available:
This mode tries all possible passwords from the given character set. It supports multi-threading.
-c, --charset allows you to specify the character set you want. For
example, -c abc123 will try all combinations of characters 'a', 'b',
'c', '1', '2' and '3' up the a maximum length (default is 8).
-i, --initial allows you to specify the initial password, the first
password to be tried. By default the initial password is the first
character of the character set (so if your character set is 'abc' the
first password that will be tested is 'a', then 'b', then 'c', then
'aa', etc). This is usefull to skip part of the password 'space'.
-l, length allows you to specify a maximum password length. Once all
passwords between 1 and length have been tested, the program will
stop.
-a, --alpha use characters [a-z].
-A, --alpha-caps use characters [A-Z].
-n, --numeric use characters [0-9].
-s, --special use special characters. These are the special,
printable, ASCII characters.
-t, --threads number of threads to start. By default, this is the
number of online CPUs, aka the number returned by
sysconf(_SC_NPROCESSORS_ONLN).
-S, --stats prints different statistics.
Try all passwords in [a-z0-9] up to 8 characters with 4 threads:
yazc bruteforce -a -n -l8 -t4 archive.zip
This mode tries all passwords from the given dictionary file. If no password file is given as argument it reads from stdin.
-d, --dictionary read passwords from the specified file.
-S, --stats prints different statistics.
Try all password from words.dict:
cat words.dict | yazc dictionary archive.zip
yazc dictionary -d words.dict archive.zip
Use John The Ripper to generate more passwords:
john --wordlist=words.dict --rules --stdout | yazc dictionary archive.zip
This mode uses a known vulnerability in the pkzip stream cipher to find the internal representation of the encryption key. Once the internal representation of the key has been found, we try to find the actual (or an equivalent) password.
-o, --offset use offsets instead of the zip file entry names. Using
this mode, you can map plaintext bytes from anywhere in any file to
the ciphertext bytes in another file. Note that the number of bytes
must match. This option can be usefull if only part of the zip entries
can be used. For example, try to find archive.zip password by using
plaintext bytes from plain.bin (map bytes 100-650 of plain.bin to
bytes 112-662 of archive.zip, first cipher byte is at offset 64):
yazc plaintext -o plain.bin 100 650 archive.zip 112 662 64
-f, --file use plaintext bytes from plaintextfile and map them to
the bytes from cipherfile. We assume that the first 12 bytes from
cipherfile is the encryption header. If some bytes cannot be mapped,
they are ignored (can happen if either the plaintext or the cipher
file is smaller). Example
yazc plaintext -f plaintextfile cipherfile
-i, --password-from-internal-rep find the password from the provided
internal representation (see section 3.6 of the Biham & Kocher paper
for more information about the internal representation). For example:
yazc plaintext -i 0x777095c0 0xc1764180 0xf5d5b494
-p, --password from a text passowrd, caculate the internal password
representation. For example:
yazc plaintext -p pAssW0Rd
-t, --threads number of threads to start. By default, this is the
number of online CPUs, aka the number returned by
sysconf(_SC_NPROCESSORS_ONLN).
-S, --stats prints different statistics.
The info sub-command lists the content of the zip file. It can help
you get the needed information needed for the plaintext or other
attack modes. Example:
yazc info data/noradi.zip
Result:
INDEX NAME OFFSETS SIZE CSIZE ENCRYPTED HEADER
0 TEXT1.TXT 39 51 155 110 116 875dee36d843e98819faae48
1 TEXT2.TXT 194 206 302 99 108 4fa3648cd55cdbdc071bfae1
2 TEXT3.TXT 341 353 439 88 98 0d9507f1cd95d217c8cadb11
- The first column (INDEX) is the index of the file in the archive.
- The second column (NAME) is the name of the file taken from the zip header.
- The third column (OFFSETS) are some interesting indexes for the plaintext attack (when using the offset '-o' option). The first number is the index of the first byte of the encrypted header, the second number is the first byte of the compressed file and the third number is the index of the last byte of the compressed file.
- The fourth column (SIZE) is the original file size in bytes.
- The fifth column (CSIZE) is the compressed file size including the encrypted header (always 12 bytes).
- The sixth column (ENCRYPTED HEADER) is the encrypted header.
This sub-command is provided to facilitate exploring the content of
zip files. Another tool you can use is zipinfo.
Distributed under the GPLv3+ license. See COPYING for more information.
Marc Ferland - [email protected]
