static int give_capabilities (pid_t pid)
{
cap_t caps = cap_init();
const unsigned caps_size = 4;
cap_value_t cap_list[] =
{ CAP_SETPCAP, CAP_SYS_NICE, CAP_SYS_RESOURCE, CAP_IPC_LOCK} ;
if (caps == NULL) {
fprintf (stderr, "jackstart: could not allocate capability working storage\n");
return -1;
}
cap_clear(caps);
if (capgetp (pid, caps)) {
fprintf (stderr, "jackstart: could not get capabilities for process %d\n", pid);
cap_clear(caps);
}
cap_set_flag(caps, CAP_EFFECTIVE, caps_size, cap_list , CAP_SET);
cap_set_flag(caps, CAP_INHERITABLE, caps_size, cap_list , CAP_SET);
cap_set_flag(caps, CAP_PERMITTED, caps_size, cap_list , CAP_SET);
if (capsetp (pid, caps)) {
fprintf (stderr, "jackstart: could not give capabilities: %s\n", strerror (errno));
cap_free (caps);
return -1;
}
cap_free (caps);
return 0;
}
static PyObject *
strcaps_set_process(PyObject *self, PyObject *args) { // (str) caps, (int) pid or None
char *strcaps; int pid = 0;
if (!PyArg_ParseTuple(args, "et|i",
Py_FileSystemDefaultEncoding, &strcaps, &pid)) return NULL;
cap_t caps;
if ((caps = cap_from_text(strcaps)) == NULL) {
PyErr_SetString(PyExc_ValueError, "Invalid capability specification");
PyMem_Free(strcaps);
return NULL; }
PyMem_Free(strcaps);
int err;
if (!pid) err = cap_set_proc(caps);
else err = capsetp(pid, caps);
if (err) {
PyErr_SetFromErrno(PyExc_OSError);
cap_free(caps);
return NULL; }
cap_free(caps);
Py_RETURN_NONE; };
/**
* Drop all capabilities.
*/
void setup_drop_caps()
{
cap_t empty;
empty = cap_init();
if (!empty) {
SYSERROR("cap_init() failed");
throw -1;
}
if ( capsetp(0, empty) ) {
SYSERROR("capsetp() failed");
throw -1;
}
if ( cap_free(empty) ) {
SYSERROR("cap_free() failed");
throw -1;
}
DEBUG("capabilities has been dropped");
}
int main(int argc, char **argv)
{
cap_t old_caps;
uid_t uid;
pid_t pid, parent_pid;
gid_t gid;
int pipe_fds[2];
/* this program should not be made setuid-0 */
if (getuid() && !geteuid()) {
usage();
}
/* check that we have at least 3 arguments */
if (argc < 4) {
usage();
}
/* Convert username to uid */
{
struct passwd *pw = getpwnam(argv[1]);
if (!pw) {
fprintf(stderr, "sucap: No such user: %s\n", argv[1]);
exit(1);
}
uid = pw->pw_uid;
}
/* Convert groupname to gid */
{
struct group *gr = getgrnam(argv[2]);
if (!gr) {
fprintf(stderr, "sucap: No such group: %s\n", argv[2]);
exit(1);
}
gid = gr->gr_gid;
}
/* set process group to current pid */
if (setpgid(0, getpid())) {
perror("sucap: Failed to set process group");
exit(1);
}
if (pipe(pipe_fds)) {
perror("sucap: pipe() failed");
exit(1);
}
parent_pid = getpid();
old_caps = cap_init();
if (capgetp(0, old_caps)) {
perror("sucap: capgetp");
exit(1);
}
{
ssize_t x;
printf("Caps: %s\n", cap_to_text(old_caps, &x));
}
/* fork off a child to do the hard work */
fflush(NULL);
pid = fork();
if (pid == -1) {
perror("sucap: fork failed");
exit(1);
}
/* 1. mother process sets gid and uid
* 2. child process sets capabilities of mother process
* 3. mother process execs whatever is to be executed
*/
if (pid) {
/* Mother process. */
close(pipe_fds[0]);
/* Get rid of any supplemental groups */
if (!getuid() && setgroups(0, 0)) {
perror("sucap: setgroups failed");
exit(1);
}
/* Set gid and uid (this probably clears capabilities) */
setregid(gid, gid);
setreuid(uid, uid);
{
ssize_t x;
cap_t cap = cap_init();
capgetp(0, cap);
printf("Caps: %s\n", cap_to_text(cap, &x));
}
printf("[debug] uid:%d, real uid:%d\n", geteuid(), getuid());
/* Signal child that we want our privileges updated */
close(pipe_fds[1]); /* Child hangs in blocking read */
/* Wait for child process to set our privileges */
{
int status = 0;
if (wait(&status) == -1) {
perror("sucap: wait failed");
}
if (!WIFEXITED(status) || WEXITSTATUS(status)) {
fprintf(stderr, "sucap: child did not exit cleanly.\n");
exit(1);
}
}
{
ssize_t x;
cap_t cap = cap_init();
capgetp(0, cap);
printf("Caps: %s\n", cap_to_text(cap, &x));
}
/* printf("[debug] uid:%d, real uid:%d\n", geteuid(), getuid()); */
/* exec the program indicated by args 2 ... */
execvp(argv[3], argv+3);
/* if we fall through to here, our exec failed -- announce the fact */
fprintf(stderr, "Unable to execute command: %s\n", strerror(errno));
usage();
} else {
/* Child process */
close(pipe_fds[1]);
/* Wait for mother process to setuid */
wait_on_fd(pipe_fds[0]);
/* Set privileges on mother process */
if (capsetp(parent_pid, old_caps)) {
perror("sucaps: capsetp");
_exit(1);
}
/* exit to signal mother process that we are ready */
_exit(0);
}
return 0;
}
