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In short, howto run a bash compressed script?, but can this be done with a binary, instead of a shell script?

Suppose I have a binary which is compressed into a .gz. I can unzip to a pipe and examine the contents thus:

$ gzip -d --stdout hello.gz | file -
/dev/stdin: ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), dynamically linked (uses shared libs), not stripped
$

Instead of piping this output to a command, is there any way I can actually execute the contents of the pipe itself, without writing it to a file?

I considered using a named pipe, but this doesn't seem to work:

$ mkfifo execpipe
$ chmod 777 execpipe
$ gzip -d --stdout hello.gz > execpipe &
[3] 30034
$ ./execpipe 
bash: ./execpipe: Permission denied
$ [3]+  Broken pipe             gzip -d --stdout hello.gz >execpipe

$

Is there a way to execute the contents of a pipe without creating an actual file?

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Digital Trauma
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  • `Permission denied` what if you try to sudo? – Thomas Ayoub Nov 12 '13 at 00:24
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    Whatever pgm you are piping it into would have to be more or less the equivalent of the OS loader that loads pgms, resolves, addresses, sets ups memory segments, etc. – Duck Nov 12 '13 at 00:29
  • @Samoth - `sudo` fails with "sudo: ./execpipe: command not found". Running under `su` also fails with "bash: ./execpipe: Permission denied" – Digital Trauma Nov 12 '13 at 00:36
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    Best you can do is dump it into a file in a ramfs or tmpfs and execute it. – Zan Lynx Nov 12 '13 at 00:54

1 Answers1

9

I believe the answer is no.

You can execute a file manually by passing it to the Linux loader, which will be named something like /lib/ld-linux.so.* It needs an actual file, though. It can't execute a pipe or stdin; it needs to be able to mmap() the file.

$ /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 /bin/true
$ /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 - < /bin/true
-: error while loading shared libraries: -: cannot open shared object file: No such file or directory
$ /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 <(cat /bin/true)
/dev/fd/63: error while loading shared libraries: /dev/fd/63: invalid ELF header

* On my Red Hat machine it's /lib/ld-linux.so.2 (32-bit) or /lib64/ld-linux-x86-64.so.2 (64-bit). On my Ubuntu machine it's /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2.

John Kugelman
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