After tar extract, Changing Permissions - php

Question

Just a Question Regarding unix and PHP today.
What I am doing on my PHP is using the Unix system to untar a tarred file.
exec("tar -xzf foo.tar.gz");
Generally everything works fine until I run into this particular foo.tar.gz, which has a file system as follows:
Applications/
Library/
Systems/
After running the tar command, it seems that the file permissions get changed to 644 (instead of 755).
This causes Permission denied (errno 13) and therefore disabling most of my code. (I'm guessing from lack of privileges)
Any way I can stop this tar command completely ruining my permissions?
Thanks.
Oh and this seems to only happen when I have a foo.tar.gz file that Has this particular file system. Anything else and I'm good.

Answer 1

If you want to keep the permissions on files then you have to add the -p (or --preserve-permissions or --same-permissions) switch when extracting the tarball. From the tar man pages :
--preserve-permissions
--same-permissions
-p
When `tar' is extracting an archive, it normally subtracts the
users' umask from the permissions specified in the archive and
uses that number as the permissions to create the destination
file. Specifying this option instructs `tar' that it should use
the permissions directly from the archive.
So PHP code should be :
exec("tar -xzfp foo.tar.gz");

Answer 2

Edit: --delay-directory-restore solved the problem below about being unable to untar a file. The permissions of pwd are still altered, so the problem of the original poster might not be solved.
Not really an answer, but a way to reproduce the error.
First create some files and directories. Remove write access to the directories:
mkdir hello
mkdir hello/world
echo "bar" > hello/world/foo.txt
chmod -w hello/world
chmod -w hello
Next, create the tar file from within the directory, preserving permissions.
cd hello
tar -cpf ../hw.tar --no-recursion ./ world world/foo.txt
cd ..
Listing the archive:
tar -tvf hw.tar
# dr-xr-xr-x ./
# dr-xr-xr-x world/
# -rw-r--r-- world/foo.txt
So far, I've been unable to untar the archive as a normal user due to the "Permission denied"-error. The archive can't be untarred naively. The permissions of the local directory change as well.
mkdir untar
cd untar
ls -ld .
# drwxr-xr-x ./
tar -xvf ../hw.tar
# ./
# world/
# tar: world: Cannot mkdir: Permission denied
# world/foo.txt
# tar: world/foo.txt: Cannot open: No such file or directory
# tar: Exiting with failure status due to previous errors
ls -ld .
# dr-xr-xr-x ./
Experimenting with umask and/or -p did not help. However, adding --delay-directory-restore does help untarring:
tar -xv --delay-directory-restore -f ../hw.tar
# ./
# world/
# world/foo.txt
ls -ld .
# dr-xr-xr-x ./
chmod +w .
It is also possible to untar the file as root. What suprised me most is that tar apparently can change the permissions of pwd, which is still unsolved.
By the way, I originally got into this problem by creating a tarball for / with
tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --one-file-system /
as root (pwd=/) and untarring it as a normal user to create a linux container.