Solved
After interesting/insightful inputs from different users, here are the takeaways:
- It doesn’t have some critical or dangerous impact or implications when extracted
- It contains the tared parent folder (see below for some neat tricks)
- It only overwrites the owner/permission if
./
itself is included in the tar file as a directory. - Tarbombs are specially crafted tar archives with absolute paths
/
(by default (GNU) tar strips absolute paths and will throw a warning except if used with a special option–absolute-names or -P
) - Interesting read: Path-traversal vulnerability (
../
)
Some neat trick I learned from the post
Temporarily created subshell with its own environment:
Let’s say you’re in the home directory that’s called /home/joe. You could go something like:
> (cd bin && pwd) && pwd
/home/joe/bin
/home/joe
Exclude parent folder and ./
./file
from tar
There are probably a lot of different ways to achieve that expected goal:
(cd mydir/
find mydir/ -printf "%P\n" | tar -czf mytar.tgz --no-recursion -C mydir/ -T -
source
The absolute path could overwrite my directory structure (tarbomb) source
Will overwrite permission/owner to the current directory if extracted. source
I’m sorry if my question wasn’t clear enough, I’m really doing my best to be as comprehensible as possible :/
Hi everyone !
I’m playing a bit around with tar to understand how it works under the hood. While poking around and searching through the web I couldn’t find an actual answer, on what are the implication of ./
and ./file
structure in the tar archive.
Output 1
sudo find ./testar -maxdepth 1 -type d,f -printf "%P\n" | sudo tar -czvf ./xtractar/tar1/testbackup1.tgz -C ./testar -T -
#output
> tar tf tar1/testbackup1.tgz
text.tz
test
my
file.txt
.testzero
test01/
test01/never.xml
test01/file.exe
test01/file.tar
test01/files
test01/.testfiles
My test folder.txt
Output 2
sudo find ./testar -maxdepth 1 -type d,f | sudo tar -czvf ./xtractar/tar2/testbackup2.tgz -C ./testar -T -
#output
>tar tf tar2/testbackup2.tgz
./testar/
./testar/text.tz
./testar/test
./testar/my
./testar/file.txt
./testar/.testzero
./testar/test01/
./testar/test01/never.xml
./testar/test01/file.exe
./testar/test01/file.tar
./testar/test01/files
./testar/test01/.testfiles
./testar/My test folder.txt
./testar/text.tz
./testar/test
./testar/my
./testar/file.txt
./testar/.testzero
./testar/test01/
./testar/test01/never.xml
./testar/test01/file.exe
./testar/test01/file.tar
./testar/test01/files
./testar/test01/.testfiles
./testar/My test folder.txt
The outputs are clearly different and if I extract them both the only difference I see is that the second outputs the parent folder. But reading here and here this is not a good solution? But nobody actually says why?
Has anyone a good explanation why the second way is bad practice? Or not recommended?
Thank you :)
Hey :) Thanks for your input but after some insight from other users I actually found out it could overwrite my folder structure (tarbomb) and also overwrite the permission/owner to the current directory (see my edited post for source). My example is probably really bad because it doesn’t contain any absolute path, but the permission/owner change still holds in the current directory.
Sorry if my question was badly written.
I believe you’d only overwrite ownership/permission of
./
if that was included in your tar.Also,
./
is a relative path. Absolute paths start with/
.The source you linked about tarbombs is talking about a tar that doesn’t use a subdirectory, not one that uses
./
prefixes.