fchmodexec mode fd ... -- cmd ...
LD_PRELOAD=libdisablefchmod.so command ...
fchmodexec - fchmod(2) inherited file descriptors before exec(3)'ing a command
fchmodexec runs as part of an exec chain to change the permissions of
any file descriptors inherited from the parent process before executing
a program.
libdisablefchmod: Disables use of fchmod(2) on stdin and stdout by dynamically linked executables.
$ umask 077; (fchmodexec 644 1 -- ls -al out) > out
$ cat out
-rw-r--r-- 1 msantos msantos 0 Mar 18 07:32 out
$ ls -al out
-rw-r--r-- 1 msantos msantos 48 Mar 18 07:32 out
$ umask 022; (LD_PRELOAD=libdisablefchmod.so fchmodexec 111 1 -- ls -al out) > out
$ cat out
-rw-r--r-- 1 msantos msantos 0 Mar 18 07:32 out
$ ls -al out
-rw-r--r-- 1 msantos msantos 48 Mar 18 07:32 out
None.
make
# also build libdisablefchmod
make all
# statically linked executable
./musl-make
exec(3), fchmod(2)