def _exec(binary, mycommand, opt_name, fd_pipes, env, gid, groups, uid, umask,
cwd, pre_exec, close_fds, unshare_net, unshare_ipc, unshare_mount,
unshare_pid, unshare_flags, cgroup):
"""
Execute a given binary with options
@param binary: Name of program to execute
@type binary: String
@param mycommand: Options for program
@type mycommand: String
@param opt_name: Name of process (defaults to binary)
@type opt_name: String
@param fd_pipes: Mapping pipes to destination; { 0:0, 1:1, 2:2 }
@type fd_pipes: Dictionary
@param env: Key,Value mapping for Environmental Variables
@type env: Dictionary
@param gid: Group ID to run the process under
@type gid: Integer
@param groups: Groups the Process should be in.
@type groups: List
@param uid: User ID to run the process under
@type uid: Integer
@param umask: an int representing a unix umask (see man chmod for umask details)
@type umask: Integer
@param cwd: Current working directory
@type cwd: String
@param pre_exec: A function to be called with no arguments just prior to the exec call.
@type pre_exec: callable
@param unshare_net: If True, networking will be unshared from the spawned process
@type unshare_net: Boolean
@param unshare_ipc: If True, IPC will be unshared from the spawned process
@type unshare_ipc: Boolean
@param unshare_mount: If True, mount namespace will be unshared and mounts will
be private to the namespace
@type unshare_mount: Boolean
@param unshare_pid: If True, PID ns will be unshared from the spawned process
@type unshare_pid: Boolean
@param unshare_flags: Flags for the unshare(2) function
@type unshare_flags: Integer
@param cgroup: CGroup path to bind the process to
@type cgroup: String
@rtype: None
@return: Never returns (calls os.execve)
"""
# If the process we're creating hasn't been given a name
# assign it the name of the executable.
if not opt_name:
if binary is portage._python_interpreter:
# NOTE: PyPy 1.7 will die due to "libary path not found" if argv[0]
# does not contain the full path of the binary.
opt_name = binary
else:
opt_name = os.path.basename(binary)
# Set up the command's argument list.
myargs = [opt_name]
myargs.extend(mycommand[1:])
# Avoid a potential UnicodeEncodeError from os.execve().
myargs = [
_unicode_encode(x, encoding=_encodings['fs'], errors='strict')
for x in myargs
]
# Use default signal handlers in order to avoid problems
# killing subprocesses as reported in bug #353239.
signal.signal(signal.SIGINT, signal.SIG_DFL)
signal.signal(signal.SIGTERM, signal.SIG_DFL)
# Unregister SIGCHLD handler and wakeup_fd for the parent
# process's event loop (bug 655656).
signal.signal(signal.SIGCHLD, signal.SIG_DFL)
try:
wakeup_fd = signal.set_wakeup_fd(-1)
if wakeup_fd > 0:
os.close(wakeup_fd)
except (ValueError, OSError):
pass
# Quiet killing of subprocesses by SIGPIPE (see bug #309001).
signal.signal(signal.SIGPIPE, signal.SIG_DFL)
# Avoid issues triggered by inheritance of SIGQUIT handler from
# the parent process (see bug #289486).
signal.signal(signal.SIGQUIT, signal.SIG_DFL)
_setup_pipes(fd_pipes, close_fds=close_fds, inheritable=True)
# Add to cgroup
# it's better to do it from the child since we can guarantee
# it is done before we start forking children
if cgroup:
with open(os.path.join(cgroup, 'cgroup.procs'), 'a') as f:
f.write('%d\n' % portage.getpid())
# Unshare (while still uid==0)
if unshare_net or unshare_ipc or unshare_mount or unshare_pid:
filename = find_library("c")
if filename is not None:
libc = LoadLibrary(filename)
if libc is not None:
try:
# Since a failed unshare call could corrupt process
# state, first validate that the call can succeed.
# The parent process should call _unshare_validate
# before it forks, so that all child processes can
# reuse _unshare_validate results that have been
# cached by the parent process.
errno_value = _unshare_validate(unshare_flags)
if errno_value == 0 and libc.unshare(unshare_flags) != 0:
errno_value = ctypes.get_errno()
if errno_value != 0:
involved_features = []
if unshare_ipc:
involved_features.append('ipc-sandbox')
if unshare_mount:
involved_features.append('mount-sandbox')
if unshare_net:
involved_features.append('network-sandbox')
if unshare_pid:
involved_features.append('pid-sandbox')
writemsg(
"Unable to unshare: %s (for FEATURES=\"%s\")\n" %
(errno.errorcode.get(errno_value, '?'),
' '.join(involved_features)),
noiselevel=-1)
else:
if unshare_pid:
main_child_pid = os.fork()
if main_child_pid == 0:
# The portage.getpid() cache may need to be updated here,
# in case the pre_exec function invokes portage APIs.
portage._ForkWatcher.hook(portage._ForkWatcher)
# pid namespace requires us to become init
binary, myargs = portage._python_interpreter, [
portage._python_interpreter,
os.path.join(portage._bin_path,
'pid-ns-init'),
_unicode_encode(
'' if uid is None else str(uid)),
_unicode_encode(
'' if gid is None else str(gid)),
_unicode_encode(
'' if groups is None else ','.join(
str(group) for group in groups)),
_unicode_encode(
'' if umask is None else str(umask)),
_unicode_encode(','.join(
str(fd) for fd in fd_pipes)), binary
] + myargs
uid = None
gid = None
groups = None
umask = None
else:
# Execute a supervisor process which will forward
# signals to init and forward exit status to the
# parent process. The supervisor process runs in
# the global pid namespace, so skip /proc remount
# and other setup that's intended only for the
# init process.
binary, myargs = portage._python_interpreter, [
portage._python_interpreter,
os.path.join(portage._bin_path,
'pid-ns-init'),
str(main_child_pid)
]
os.execve(binary, myargs, env)
if unshare_mount:
# mark the whole filesystem as slave to avoid
# mounts escaping the namespace
s = subprocess.Popen(
['mount', '--make-rslave', '/'])
mount_ret = s.wait()
if mount_ret != 0:
# TODO: should it be fatal maybe?
writemsg("Unable to mark mounts slave: %d\n" %
(mount_ret, ),
noiselevel=-1)
if unshare_pid:
# we need at least /proc being slave
s = subprocess.Popen(
['mount', '--make-slave', '/proc'])
mount_ret = s.wait()
if mount_ret != 0:
# can't proceed with shared /proc
writemsg("Unable to mark /proc slave: %d\n" %
(mount_ret, ),
noiselevel=-1)
os._exit(1)
# mount new /proc for our namespace
s = subprocess.Popen(
['mount', '-n', '-t', 'proc', 'proc', '/proc'])
mount_ret = s.wait()
if mount_ret != 0:
writemsg("Unable to mount new /proc: %d\n" %
(mount_ret, ),
noiselevel=-1)
os._exit(1)
if unshare_net:
# use 'localhost' to avoid hostname resolution problems
try:
# pypy3 does not implement socket.sethostname()
new_hostname = b'localhost'
if hasattr(socket, 'sethostname'):
socket.sethostname(new_hostname)
else:
if libc.sethostname(
new_hostname,
len(new_hostname)) != 0:
errno_value = ctypes.get_errno()
raise OSError(errno_value,
os.strerror(errno_value))
except Exception as e:
writemsg(
"Unable to set hostname: %s (for FEATURES=\"network-sandbox\")\n"
% (e, ),
noiselevel=-1)
_configure_loopback_interface()
except AttributeError:
# unshare() not supported by libc
pass
# Set requested process permissions.
if gid:
# Cast proxies to int, in case it matters.
os.setgid(int(gid))
if groups:
os.setgroups(groups)
if uid:
# Cast proxies to int, in case it matters.
os.setuid(int(uid))
if umask:
os.umask(umask)
if cwd is not None:
os.chdir(cwd)
if pre_exec:
pre_exec()
# And switch to the new process.
os.execve(binary, myargs, env)
