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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

source

Exclude parent folder and ./ ./file from tar

There are probably a lot of different ways to achieve that expected goal:

(cd mydir/ && tar -czvf mydir.tgz *)

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 :)

  • DefederateLemmyMl@feddit.nl
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    8 months ago

    If my tar contains the following folder ./home/user/ and I extract it in my current home folder (which would be kinda stupid but It happens) this will overwrite the home folder

    No it will not. It will extract your files to /home/user/home/user, so a nested home directory inside your home directory (yo dawg).

    The man page section you quote is about absolute paths. That is, paths that start with a / without a leading dot. They indeed can be dangerous, but by default (GNU) tar strips absolute paths and will throw a warning like:

    # tar -cf test.tar /etc/hosts
                       ^leading slash
    tar: Removing leading `/' from member names
    
    # tar -tvf test.tar
    -rw-r--r-- root/root       184 2022-12-08 20:27 etc/hosts
                                                   ^no leading slash
    
    
    • N0x0n@lemmy.mlOP
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      8 months ago

      Thank you very much for the clarification ! That’s exactly the kind of input I was looking for ! I tried it out and your absolutely right ! I will edit my post.

    • N0x0n@lemmy.mlOP
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      8 months ago

      Thanks after a long sleep I edited my post to avoid misinformation and errors due of my lacked knowledge ! Thanks for your time and clarifications on that specific point !