src/libelogind/sd-bus/bus-container.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2013 Lennart Poettering
   4 ***/
   5
   6 #include <fcntl.h>
   7 #include <unistd.h>
   8
   9 #include "bus-container.h"
  10 #include "bus-internal.h"
  11 #include "bus-socket.h"
  12 #include "fd-util.h"
  13 #include "process-util.h"
  14 #include "util.h"
  15
  16 int bus_container_connect_socket(sd_bus *b) {
  17         _cleanup_close_pair_ int pair[2] = { -1, -1 };
  18         _cleanup_close_ int pidnsfd = -1, mntnsfd = -1, usernsfd = -1, rootfd = -1;
  19         int r, error_buf = 0;
  20         pid_t child;
  21         ssize_t n;
  22
  23         assert(b);
  24         assert(b->input_fd < 0);
  25         assert(b->output_fd < 0);
  26         assert(b->nspid > 0 || b->machine);
  27
  28         if (b->nspid <= 0) {
  29                 r = container_get_leader(b->machine, &b->nspid);
  30                 if (r < 0)
  31                         return r;
  32         }
  33
  34         r = namespace_open(b->nspid, &pidnsfd, &mntnsfd, NULL, &usernsfd, &rootfd);
  35         if (r < 0)
  36                 return r;
  37
  38         b->input_fd = socket(b->sockaddr.sa.sa_family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
  39         if (b->input_fd < 0)
  40                 return -errno;
  41
  42         b->input_fd = fd_move_above_stdio(b->input_fd);
  43
  44         b->output_fd = b->input_fd;
  45
  46         bus_socket_setup(b);
  47
  48         if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, pair) < 0)
  49                 return -errno;
  50
  51         r = safe_fork("(sd-buscntr)", FORK_RESET_SIGNALS|FORK_DEATHSIG, &child);
  52         if (r < 0)
  53                 return r;
  54         if (r == 0) {
  55                 pid_t grandchild;
  56
  57                 pair[0] = safe_close(pair[0]);
  58
  59                 r = namespace_enter(pidnsfd, mntnsfd, -1, usernsfd, rootfd);
  60                 if (r < 0)
  61                         _exit(EXIT_FAILURE);
  62
  63                 /* We just changed PID namespace, however it will only
  64                  * take effect on the children we now fork. Hence,
  65                  * let's fork another time, and connect from this
  66                  * grandchild, so that SO_PEERCRED of our connection
  67                  * comes from a process from within the container, and
  68                  * not outside of it */
  69
  70                 r = safe_fork("(sd-buscntr2)", FORK_RESET_SIGNALS|FORK_DEATHSIG, &grandchild);
  71                 if (r < 0)
  72                         _exit(EXIT_FAILURE);
  73                 if (r == 0) {
  74
  75                         r = connect(b->input_fd, &b->sockaddr.sa, b->sockaddr_size);
  76                         if (r < 0) {
  77                                 /* Try to send error up */
  78                                 error_buf = errno;
  79                                 (void) write(pair[1], &error_buf, sizeof(error_buf));
  80                                 _exit(EXIT_FAILURE);
  81                         }
  82
  83                         _exit(EXIT_SUCCESS);
  84                 }
  85
  86                 r = wait_for_terminate_and_check("(sd-buscntr2)", grandchild, 0);
  87                 if (r < 0)
  88                         _exit(EXIT_FAILURE);
  89
  90                 _exit(r);
  91         }
  92
  93         pair[1] = safe_close(pair[1]);
  94
  95         r = wait_for_terminate_and_check("(sd-buscntr)", child, 0);
  96         if (r < 0)
  97                 return r;
  98         if (r != EXIT_SUCCESS)
  99                 return -EPROTO;
 100
 101         n = read(pair[0], &error_buf, sizeof(error_buf));
 102         if (n < 0)
 103                 return -errno;
 104
 105         if (n > 0) {
 106                 if (n != sizeof(error_buf))
 107                         return -EIO;
 108
 109                 if (error_buf < 0)
 110                         return -EIO;
 111
 112                 if (error_buf == EINPROGRESS)
 113                         return 1;
 114
 115                 if (error_buf > 0)
 116                         return -error_buf;
 117         }
 118
 119         return bus_socket_start_auth(b);
 120 }