FS setuid python

fssetuid.py

from cffi import FFI
import os
ffi = FFI()

ffi.cdef("""
int setfsuid(int fsuid);
int getgroups(int fsuid, int[]);
int setgroups(int size, const int *list);
""")

sys = ffi.dlopen(None)

def setfsuid(uid):
    return sys.setfsuid(ffi.cast("int", uid))

def getgroups():
    ptr = ffi.new("int[]", [])
    size = sys.getgroups(ffi.cast("int", 0), ptr)
    ret_val = ffi.new("int[]", size)
    sys.getgroups(size, ret_val)
    return ret_val


def setgroups(groups):
    new_groups = ffi.new("const int[]", groups)
    size = sys.setgroups(len(new_groups), new_groups)
    return size

setfsuid(1000)
setfsuid(1000)
print(os.getuid())
print(os.getgroups())
print(getgroups())

setgroups([1000, 1001])
print(os.getgroups())
print(getgroups())