summaryrefslogtreecommitdiff
path: root/pkg/rootless/rootless_linux.c
blob: 84fac238f9fe4496874f01808743bb3664dfa0ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <limits.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>

static int
syscall_clone (unsigned long flags, void *child_stack)
{
  return (int) syscall (__NR_clone, flags, child_stack);
}

static char **
get_cmd_line_args (pid_t pid)
{
  int fd;
  char path[PATH_MAX];
  char *buffer;
  size_t allocated;
  size_t used = 0;
  int ret;
  int i, argc = 0;
  char **argv;

  sprintf (path, "/proc/%d/cmdline", pid);
  fd = open (path, O_RDONLY);
  if (fd < 0)
    return NULL;

  allocated = 512;
  buffer = malloc (allocated);
  if (buffer == NULL)
    return NULL;
  for (;;)
    {
      do
        ret = read (fd, buffer + used, allocated - used);
      while (ret < 0 && errno == EINTR);
      if (ret < 0)
        return NULL;

      if (ret == 0)
        break;

      used += ret;
      if (allocated == used)
        {
          allocated += 512;
          buffer = realloc (buffer, allocated);
          if (buffer == NULL)
            return NULL;
        }
    }
  close (fd);

  for (i = 0; i < used; i++)
    if (buffer[i] == '\0')
      argc++;

  argv = malloc (sizeof (char *) * (argc + 1));
  if (argv == NULL)
    return NULL;
  argc = 0;

  argv[argc++] = buffer;
  for (i = 0; i < used - 1; i++)
    if (buffer[i] == '\0')
      argv[argc++] = buffer + i + 1;

  argv[argc] = NULL;

  return argv;
}

int
reexec_in_user_namespace(int ready)
{
  int ret;
  pid_t pid;
  char b;
  pid_t ppid = getpid ();
  char **argv;
  char uid[16];

  sprintf (uid, "%d", geteuid ());

  pid = syscall_clone (CLONE_NEWUSER|CLONE_NEWNS|SIGCHLD, NULL);
  if (pid)
    return pid;

  argv = get_cmd_line_args (ppid);
  if (argv == NULL)
    _exit (EXIT_FAILURE);

  setenv ("_LIBPOD_USERNS_CONFIGURED", "init", 1);
  setenv ("_LIBPOD_ROOTLESS_UID", uid, 1);

  do
    ret = read (ready, &b, 1) < 0;
  while (ret < 0 && errno == EINTR);
  if (ret < 0)
    _exit (EXIT_FAILURE);
  close (ready);

  if (setresgid (0, 0, 0) < 0 ||
      setresuid (0, 0, 0) < 0)
    _exit (EXIT_FAILURE);

  execvp (argv[0], argv);

  _exit (EXIT_FAILURE);
}

int
reexec_in_user_namespace_wait (int pid)
{
  pid_t p;
  int status;

  do
    p = waitpid (pid, &status, 0);
  while (p < 0 && errno == EINTR);

  if (p < 0)
    return -1;

  if (WIFEXITED (status))
    return WEXITSTATUS (status);
  if (WIFSIGNALED (status))
    return 128 + WTERMSIG (status);
  return -1;
}