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

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