Unpack, pack, list, test and mount Unreal Engine 4 .pak archives.
NOTE: I've wrote an alternative version of this in Rust and compiled a self-contained binary for Windows users. So there is no hassle with installing Python, plus it adds a way to supply command line arguments via a file that you can associate with the binary so you only need to double click that. It is also faster, mainly because it uses multi-threading. (Note that it's command line arguments are sligthly different.)
Basic usage:
u4pak.py info <archive> - print archive summary info
u4pak.py list <archive> - list contens of .pak archive
u4pak.py test <archive> - test archive integrity
u4pak.py unpack <archive> - extract .pak archive
u4pak.py pack <archive> <files> - create .pak archive
u4pak.py mount <archive> <mount-point> - mount archive as read-only file system
For unpacking only unencryped archives of version 1, 2, 3, 4, and 7 are supported, for packing only version 1, 2, and 3.
NOTE: If you know (cheap) games that use other archive versions please tell me! Especially if its 5 or 6. There is a change in how certain offsets are handled at some point, but since I only have an example file of version 7 I don't know if it happened in version 5, 6, or 7.
The mount command depends on the llfuse
Python package. If it's not available the rest is still working.
This script is compatible with Python 3.7.
If you get errors saying anything about 'utf8' codec can't decode byte [...] try to
use another encoding by passing --encoding=iso-8859-1 or similar.
If you get an error message about an illegal file magic try to pass --ignore-magic.
If you get an error message about the archive version being 0 try to pass
--force-version=1 (or a higher number).
Byte order is little endian and the character encoding of file names seems to be ASCII (or ISO-8859-1/UTF-8 that coincidentally only uses ASCII compatiple characters).
Offsets and sizes seem to be 64bit or at least unsigned 32bit integers. If interpreted as 32bit integers all sizes (except the size of file names) and offsets are followed by another 32bit integer of the value 0, which makes me guess these are 64bit values. Also some values exceed the range of signed 32bit integers, so they have to be at least unsigned 32bit integers. This information was reverse engineered from the Elemental Demo for Linux (which contains a 2.5 GB .pak file).
Basic layout:
- Data Records
- Index
- Index Header
- Index Records
- Footer
In order to parse a file you need to read the footer first. The footer contains an offset pointer to the start of the index records. The index records then contain offset pointers to the data records.
Some games seem to zero out parts of the file. In particular the footer, which makes it pretty much impossible to read the file without manual analysis and guessing. I suspect these games have the footer included somewhere in the game binary. If it's not obfuscated one might be able to find it using the file magic (given that the file magic is even included)?
Offset Size Type Description
0 8 uint64_t offset
8 8 uint64_t size (N)
16 8 uint64_t uncompressed size
24 4 uint32_t compression method:
0x00 ... none
0x01 ... zlib
0x10 ... bias memory
0x20 ... bias speed
if version <= 1
28 8 uint64_t timestamp
end
? 20 uint8_t[20] data sha1 hash
if version >= 3
if compression method != 0x00
?+20 4 uint32_t block count (M)
?+24 M*16 CB[M] compression blocks
end
? 1 uint8_t is encrypted
?+1 4 uint32_t The uncompressed size of each compression block.
end The last block can be smaller, of course.
Size: 16 bytes
Offset Size Type Description
0 8 uint64_t compressed data block start offset.
version <= 4: offset is absolute to the file
version 7: offset is relative to the offset
field in the corresponding Record
8 8 uint64_t compressed data block end offset.
There may or may not be a gap between blocks.
version <= 4: offset is absolute to the file
version 7: offset is relative to the offset
field in the corresponding Record
Offset Size Type Description
0 ? Record file metadata (offset field is 0, N = compressed_size)
? N uint8_t[N] file data
Offset Size Type Description
0 4 uint32_t file name size (S)
4 S char[S] file name (includes terminating null byte)
4+S ? Record file metadata
Offset Size Type Description
0 4 uint32_t mount point size (S)
4 S char[S] mount point (includes terminating null byte)
S+4 4 uint32_t record count (N)
S+8 ? IndexRecord[N] records
Size: 44 bytes
Offset Size Type Description
0 4 uint32_t magic: 0x5A6F12E1
4 4 uint32_t version: 1, 2, 3, 4, or 7
8 8 uint64_t index offset
16 8 uint64_t index size
24 20 uint8_t[20] index sha1 hash
- fezpak: pack, unpack, list and mount FEZ .pak archives
- psypkg: pack, unpack, list and mount Psychonauts .pkg archives
- bgebf: unpack, list and mount Beyond Good and Evil .bf archives
- unvpk: extract, list, check and mount Valve .vpk archives
- rust-vpk: Rust rewrite of the above
- t2fbq: unpack, list and mount Trine 2 .fbq archives
- rust-u4pak: not yet finished Rust rewrite of this script
Copyright (c) 2014-2019 Mathias Panzenböck
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