8000 gh-94518: [_posixsubprocess] Replace variable validity flags with reserved values by arhadthedev · Pull Request #94687 · python/cpython · GitHub
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gh-94518: [_posixsubprocess] Replace variable validity flags with reserved values #94687

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Merged
merged 14 commits into from
Jan 14, 2023
Merged

gh-94518: [_posixsubprocess] Replace variable validity flags with reserved values #94687

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1b3250e
Replace call_setgid/call_setuid in _posixsubprocess with gid/uid==-1
arhadthedev Jul 8, 2022
c292331
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Jul 22, 2022
7d431a3
Add a NEWS entry
arhadthedev Jul 22, 2022
06f2a01
Address Gregory's review in gh-94519
arhadthedev Jul 26, 2022
aaec16e
Use negative groups_size for "don't call setgroups"
arhadthedev Jul 27, 2022
c9bf4f6
Check num_groups for emptiness, not groups_list
arhadthedev Jul 27, 2022
069d769
Restore assertions in do_fork_exec()
arhadthedev Jul 27, 2022
6a236e5
Tighten scope of relevant short lived variables
arhadthedev Jul 27, 2022
8c06be1
Fix `PermissionError: [Errno 1] Operation not permitted` exception
arhadthedev Jul 27, 2022
3ccdb78
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Oct 6, 2022
d3c0e6c
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Oct 29, 2022
cfdf639
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Nov 14, 2022
0e997c0
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Nov 29, 2022
66c836b
Merge branch 'main' into posixsubprocess-no-callsetxid
arhadthedev Jan 14, 2023
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Replace call_setgid/call_setuid in _posixsubprocess with gid/uid==-1
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@arhadthedev
arhadthedev committed Jul 8, 2022
commit 1b3250e96bd3398f6a79ed85258250fa375f916c
48 changes: 22 additions & 26 deletions Modules/_posixsubprocess.c
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10000
Original file line number Diff line number Diff line change
Expand Up @@ -476,6 +476,10 @@ reset_signal_handlers(const sigset_t *child_sigmask)
#endif /* VFORK_USABLE */


/* To avoid signeness churn on platforms where gid and uid are unsigned. */
#define RESERVED_GID (gid_t)-1
#define RESERVED_UID (uid_t)-1

/*
* This function is code executed in the child process immediately after
* (v)fork to set things up and call exec().
Expand Down Expand Up @@ -518,9 +522,9 @@ child_exec(char *const exec_array[],
int errpipe_read, int errpipe_write,
int close_fds, int restore_signals,
int call_setsid, pid_t pgid_to_set,
int call_setgid, gid_t gid,
int call_setgroups, size_t groups_size, const gid_t *groups,
int call_setuid, uid_t uid, int child_umask,
gid_t gid,
size_t groups_size, const gid_t *groups,
uid_t uid, int child_umask,
const void *child_sigmask,
PyObject *py_fds_to_keep,
PyObject *preexec_fn,
Expand Down Expand Up @@ -619,17 +623,17 @@ child_exec(char *const exec_array[],
#endif

#ifdef HAVE_SETGROUPS
if (call_setgroups)
if (groups)
POSIX_CALL(setgroups(groups_size, groups));
#endif /* HAVE_SETGROUPS */

#ifdef HAVE_SETREGID
if (call_setgid)
if (gid != RESERVED_GID)
POSIX_CALL(setregid(gid, gid));
#endif /* HAVE_SETREGID */

#ifdef HAVE_SETREUID
if (call_setuid)
if (uid != RESERVED_UID)
POSIX_CALL(setreuid(uid, uid));
#endif /* HAVE_SETREUID */

Expand Down Expand Up @@ -724,9 +728,9 @@ do_fork_exec(char *const exec_array[],
int errpipe_read, int errpipe_write,
int close_fds, int restore_signals,
int call_setsid, pid_t pgid_to_set,
int call_setgid, gid_t gid,
int call_setgroups, size_t groups_size, const gid_t *groups,
int call_setuid, uid_t uid, int child_umask,
gid_t gid,
size_t groups_size, const gid_t *groups,
uid_t uid, int child_umask,
const void *child_sigmask,
PyObject *py_fds_to_keep,
PyObject *preexec_fn,
Expand All @@ -737,10 +741,7 @@ do_fork_exec(char *const exec_array[],

#ifdef VFORK_USABLE
if (child_sigmask) {
/* These are checked by our caller; verify them in debug builds. */
assert(!call_setuid);
assert(!call_setgid);
assert(!call_setgroups);
/* Checked by our caller; verify this in debug builds. */
assert(preexec_fn == Py_None);

pid = vfork();
Expand Down Expand Up @@ -777,8 +778,8 @@ do_fork_exec(char *const exec_array[],
p2cread, p2cwrite, c2pread, c2pwrite,
errread, errwrite, errpipe_read, errpipe_write,
close_fds, restore_signals, call_setsid, pgid_to_set,
call_setgid, gid, call_setgroups, groups_size, groups,
call_setuid, uid, child_umask, child_sigmask,
gid, groups_size, groups,
uid, child_umask, child_sigmask,
py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);
_exit(255);
return 0; /* Dead code to avoid a potential compiler warning. */
Expand All @@ -799,9 +800,7 @@ subprocess_fork_exec(PyObject *module, PyObject *args)
int errpipe_read, errpipe_write, close_fds, restore_signals;
int call_setsid;
pid_t pgid_to_set = -1;
int call_setgid = 0, call_setgroups = 0, call_setuid = 0;
uid_t uid;
gid_t gid, *groups = NULL;
gid_t *groups = NULL;
int child_umask;
PyObject *cwd_obj, *cwd_obj2 = NULL;
const char *cwd;
Expand Down Expand Up @@ -951,34 +950,31 @@ subprocess_fork_exec(PyObject *module, PyObject *args)
}
Py_DECREF(elem);
}
call_setgroups = 1;

#else /* HAVE_SETGROUPS */
PyErr_BadInternalCall();
goto cleanup;
#endif /* HAVE_SETGROUPS */
}

gid_t gid = RESERVED_GID;
if (gid_object != Py_None) {
#ifdef HAVE_SETREGID
if (!_Py_Gid_Converter(gid_object, &gid))
goto cleanup;

call_setgid = 1;

#else /* HAVE_SETREGID */
PyErr_BadInternalCall();
goto cleanup;
#endif /* HAVE_SETREUID */
}

uid_t uid = RESERVED_UID;
if (uid_object != Py_None) {
#ifdef HAVE_SETREUID
if (!_Py_Uid_Converter(uid_object, &uid))
goto cleanup;

call_setuid = 1;

#else /* HAVE_SETREUID */
PyErr_BadInternalCall();
goto cleanup;
Expand All @@ -1002,7 +998,7 @@ subprocess_fork_exec(PyObject *module, PyObject *args)
/* Use vfork() only if it's safe. See the comment above child_exec(). */
sigset_t old_sigs;
if (preexec_fn == Py_None && allow_vfork &&
!call_setuid && !call_setgid && !call_setgroups) {
uid == RESERVED_UID && gid == RESERVED_GID && groups_list == Py_None) {
/* Block all signals to ensure that no signal handlers are run in the
* child process while it shares memory with us. Note that signals
* used internally by C libraries won't be blocked by
Expand All @@ -1025,8 +1021,8 @@ subprocess_fork_exec(PyObject *module, PyObject *args)
p2cread, p2cwrite, c2pread, c2pwrite,
errread, errwrite, errpipe_read, errpipe_write,
close_fds, restore_signals, call_setsid, pgid_to_set,
call_setgid, gid, call_setgroups, num_groups, groups,
call_setuid, uid, child_umask, old_sigmask,
gid, num_groups, groups_list != Py_None ? groups : NULL,
uid, child_umask, old_sigmask,
py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);

/* Parent (original) process */
Expand Down
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