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Let's say user wants to execute a script test.sh but ls -l test.sh gives
-rwxrwxr-- 1 root root 96 Feb 25 21:44 test.sh
Now if user doesn't want to make a copy of test.sh (on which he does chmod +x), he can simply do
sh test.sh
to execute test.sh.
Is there an analogue way to execute binary programs which one doesn't have execute permissions?
Basically this is the same thing as one of the very famous UNIX technical interview questions, known for ages:
Assume someone with root access ran a command chmod -R 444 / and made the chmod binary non-executable. How do you recover from it ?
There is a perl answer and there is this one, which basically is running a non-executable program, chmod in this case:
/lib/ld-linux.so /bin/chmod +x /bin/chmod
I think you can apply it to any other program that you know is executable. Otherwise be ready to embrace the disaster, which may ensue
PS> /lib/ld-linux.so might differ in name. So if the direct match is not available, look around for similarly named so's. For instance on my CentOS 6 server, it is /lib/ld-linux.so.2 which is a symlink pointing to /lib/ld-2.12.so. So, your mileage may vary.
chmod -R 444 /, then /lib/ld-linux.so won't be executable either. If your (still running) shell is zsh, you can do zmodload zsh/files which gives you a builtin chmod. If it's ksh93, you can do command /opt/ast/bin/chmod to get a builtin chmod as well.
Feb 25, 2016 at 21:28
file returns the same ELF format on both files.
/lib/x86_64-linux-gnu/ld-2.19.so /bin/ls instead. The version in /lib is for 32-bit executables.
If the user doesn't have execute permission and cannot or is not willing to have it changed, then they must execute it as a group or user who does have execute permission.
If they know the root password then:
su -c <executable>
If they don't know the root password, but are trusted with sudo then:
sudo <executable>
If they don't know the root password and are not trusted with sudo privileges, then there is a reason why they should run the executable.
sudo <program>- seeman sudochmod, same result when the exec bits are unset. Perhaps this behaviour is controlled by asudosetting?-rwxrwxr-- root root 86 Feb 25 21:44 testin/usr/bin. Userdoedoesn't have execute permission for this, but can run it withsudo test. Or have I misread the question?