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
|
/*
* Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/StringView.h>
#include <LibCore/ArgsParser.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char** argv)
{
int flags = -1;
uid_t chroot_user = 0;
gid_t chroot_group = 0;
const char* path = nullptr;
const char* program = "/bin/Shell";
const char* userspec = "0:0";
Core::ArgsParser args_parser;
args_parser.set_general_help(
"Run a program in a chroot sandbox. During execution, the program "
"sees the given path as '/', and cannot access files outside of it.");
args_parser.add_positional_argument(path, "New root directory", "path");
args_parser.add_positional_argument(program, "Program to run", "program", Core::ArgsParser::Required::No);
Core::ArgsParser::Option userspec_option {
true,
"The uid:gid to use",
"userspec",
'u',
"userpec",
[&userspec](const char* s) {
Vector<StringView> parts = StringView(s).split_view(':', true);
if (parts.size() != 2)
return false;
userspec = s;
return true;
}
};
args_parser.add_option(move(userspec_option));
Core::ArgsParser::Option mount_options {
true,
"Mount options",
"options",
'o',
"options",
[&flags](const char* s) {
flags = 0;
Vector<StringView> parts = StringView(s).split_view(',');
for (auto& part : parts) {
if (part == "defaults")
continue;
else if (part == "nodev")
flags |= MS_NODEV;
else if (part == "noexec")
flags |= MS_NOEXEC;
else if (part == "nosuid")
flags |= MS_NOSUID;
else if (part == "ro")
flags |= MS_RDONLY;
else if (part == "remount")
flags |= MS_REMOUNT;
else if (part == "bind")
warnln("Ignoring -o bind, as it doesn't make sense for chroot");
else
return false;
}
return true;
}
};
args_parser.add_option(move(mount_options));
args_parser.parse(argc, argv);
if (chroot_with_mount_flags(path, flags) < 0) {
perror("chroot");
return 1;
}
if (chdir("/") < 0) {
perror("chdir(/)");
return 1;
}
// Failed parsing will silently fail open (uid=0; gid=0);
// 0:0 is also the default when no --userspec argument is provided.
auto parts = String(userspec).split(':', true);
chroot_user = (uid_t)strtol(parts[0].characters(), nullptr, 10);
chroot_group = (uid_t)strtol(parts[1].characters(), nullptr, 10);
if (setresgid(chroot_group, chroot_group, chroot_group)) {
perror("setgid");
return 1;
}
if (setresuid(chroot_user, chroot_user, chroot_user)) {
perror("setuid");
return 1;
}
execl(program, program, nullptr);
perror("execl");
return 1;
}
|
