How to mark things I download automatically executable?

Question

I spend a lot of time downloading things that I am going to execute, without a doubt, after having downloaded them. Out of the 900-ish files in my download folder right now, roughly a third is stuff that I did download and then execute because it's the reason I downloaded them for in the first place.

Every time though, I have to do the little tiring dance of chmod +x'ing them, which is a complete waste of time as I am not downloading them just for the fun of it. Right now I have a dozen small scripts I am going to download in the next half hour and I shudder to the thought of having to chmod them all.

What can I do to make Linux either:

• ignore the x permission altogether and just do what I tell it to do without questions and without second-guessing me, as the owner, administrator, eternal deity etc etc, of my own, personal computer?
• automatically mark downloaded files as executable if they match an ELF, shell, python, etc.. file signature?

Answer 1

This is perhaps not a good idea for security and future readers should think carefully about whether it's right for them. However you have described a pretty specific use case for this, so I'll offer an option.

Probably the easiest thing you could do is setup a background script to monitor your ~/Downloads directory with inotify-wait (Ubuntu inotify-tools package) and immediately change file permissions on the file as it's been closed by whatever program has written it (IE after it's downloaded):

#!/bin/bash
inotify-wait -m ~/Downloads -e close_write --format %f | while IFS= read -r line ; do
 chmod u+x ~/Downloads/"$file"
done

Of course this will change every file added to your ~/Downloads directory, not just the ELF, shell, python scripts. For that you'd need to add in additional rules to determine the file name and be selective. For example you could use the file to identify the files you are interested in.

Answer 2

I agree with Philip Couling and would go a step further: downloading files and then executing them without doing any inspection, validation or verification is somewhat reckless from a security perspective.  But, if you trust the source without reservation, and you’re just working on your own personal computer, it’s your decision.

1. You ask what you can do to make Linux ignore the x permission altogether and just do what you tell it to do.  Well, if the file is a shell script, you can type

   sh   filename arg1 arg2 arg3 …

   or

   bash filename arg1 arg2 arg3 …

   If it’s a python script, you can type

   python  filename arg1 arg2 arg3 …

   or

   python2 filename arg1 arg2 arg3 …

   or

   python3 filename arg1 arg2 arg3 …

   as appropriate.  Notes:
   • These will fail if the script tries to call itself recursively in the normal way, i.e., assuming that the x bit is set.
   • I don’t know of any equivalent command for binary executable files, like ELF files.

   I really advise against downloading files and then executing them without even knowing what type they are.

2. You shudder at the thought of having to chmod a dozen scripts.  I don’t understand.  Is typing the nine characters c h m o d   + x   such a hardship?

   Do you know about aliases?  In Bash (i.e., in your ~/.bashrc), you can say

   alias '+x'='chmod +x'
   

   Then you can use

   +x filename(s)

   to chmod your files (less typing).  And, as roaima indicated, you can use wildcards (globs) with the chmod command, so +x *.sh works.

   To save one more character, use x as the alias name instead of +x.

3. A combination of the above ideas: create a shell function

   run()
   {
           chmod +x "$1"  &&  "$@"
   }
   

   Then you can type

   run filename arg1 arg2 arg3 …

   to chmod your file and execute it in one command.  (You might want to do type run to check whether there is a command called run on your computer, and, if there is, use a different name.)

Answer 3

I think the best thing to do is to keep things simple. If your downloading scripts to just test them out once or twice, why make them executable at all.

Just do this, shell cmd. Just invoke the shell the script uses. In this case a bash script.

bash DownloadedScript.sh

Leaving a lot of executable scripts that you're not using that much in your Downloads is not a good idea. Leaving them as not executable is better for system security.

Answer 4

I run as root in a closed system, so security is not an issue.

I made a .Desktop file in KDE service menu labled "make executable" and right click (context menu for right handed mouse) to change perms.

======================================== [Desktop Entry] Type=Service ServiceTypes=KonqPopupMenu/Plugin MimeType=application/x-shellscript;application/x-ruby;text/x-python;application/x-executable Icon=application-x-shellscript X-KDE-Priority=TopLevel X-KDE-StartupNotify=false X-KDE-Submenu=Make executable - Copy to /usr/bin

Actions=me;cp;

[Desktop Action me] Name=Make executable Icon=system-run Exec=chmod +x "%f"

[Desktop Action cp] Name=Copy to /usr/bin Icon=password-copy Exec=kdesu -d --noignorebutton -c 'sudo cp "%f" /usr/bin/'

It also can copy to /usr/bin if you want.

Easy as pie.

Sorry, I was unable to understand the "code" aspect of posting. No offence intended. Will try to get it right.

Vic

Answer 5

For your particular use-case, where you are cyclically downloading from the same URL and running what are actually different versions, perhaps something like this:

while
    printf 'Press enter to download and run:'
    read -r
do
    curl "$URL" >| tmpexec &&
    chmod +x tmpexec &&
    ./tmpexec
done

(I hope this also side-steps the security concerns many would have about downloading from a random public site, which are not relevant here.)