1 // Copyright 2015 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "sandbox/linux/services/namespace_utils.h"
6
7 #include <fcntl.h>
8 #include <sched.h>
9 #include <stddef.h>
10 #include <sys/stat.h>
11 #include <sys/types.h>
12 #include <unistd.h>
13
14 #include <string>
15
16 #include "base/files/file_path.h"
17 #include "base/files/file_util.h"
18 #include "base/files/scoped_file.h"
19 #include "base/logging.h"
20 #include "base/posix/eintr_wrapper.h"
21 #include "base/process/launch.h"
22 #include "base/strings/safe_sprintf.h"
23 #include "third_party/valgrind/valgrind.h"
24
25 namespace sandbox {
26
27 namespace {
IsRunningOnValgrind()28 bool IsRunningOnValgrind() {
29 return RUNNING_ON_VALGRIND;
30 }
31
32 const char kProcSelfSetgroups[] = "/proc/self/setgroups";
33 } // namespace
34
35 // static
WriteToIdMapFile(const char * map_file,generic_id_t id)36 bool NamespaceUtils::WriteToIdMapFile(const char* map_file, generic_id_t id) {
37 // This function needs to be async-signal-safe, as it may be called in between
38 // fork and exec.
39
40 int fd = HANDLE_EINTR(open(map_file, O_WRONLY));
41 if (fd == -1) {
42 return false;
43 }
44
45 const generic_id_t inside_id = id;
46 const generic_id_t outside_id = id;
47
48 char mapping[64];
49 const ssize_t len =
50 base::strings::SafeSPrintf(mapping, "%d %d 1\n", inside_id, outside_id);
51 const ssize_t rc = HANDLE_EINTR(write(fd, mapping, len));
52 RAW_CHECK(IGNORE_EINTR(close(fd)) == 0);
53 return rc == len;
54 }
55
56 // static
KernelSupportsUnprivilegedNamespace(int type)57 bool NamespaceUtils::KernelSupportsUnprivilegedNamespace(int type) {
58 // Valgrind will let clone(2) pass-through, but doesn't support unshare(),
59 // so always consider namespaces unsupported there.
60 if (IsRunningOnValgrind()) {
61 return false;
62 }
63
64 // As of Linux 3.8, /proc/self/ns/* files exist for all namespace types. Since
65 // user namespaces were added in 3.8, it is OK to rely on the existence of
66 // /proc/self/ns/*.
67 if (!base::PathExists(base::FilePath("/proc/self/ns/user"))) {
68 return false;
69 }
70
71 const char* path;
72 switch (type) {
73 case CLONE_NEWUSER:
74 return true;
75 case CLONE_NEWIPC:
76 path = "/proc/self/ns/ipc";
77 break;
78 case CLONE_NEWNET:
79 path = "/proc/self/ns/net";
80 break;
81 case CLONE_NEWNS:
82 path = "/proc/self/ns/mnt";
83 break;
84 case CLONE_NEWPID:
85 path = "/proc/self/ns/pid";
86 break;
87 case CLONE_NEWUTS:
88 path = "/proc/self/ns/uts";
89 break;
90 default:
91 NOTREACHED();
92 return false;
93 }
94
95 return base::PathExists(base::FilePath(path));
96 }
97
98 // static
KernelSupportsDenySetgroups()99 bool NamespaceUtils::KernelSupportsDenySetgroups() {
100 return base::PathExists(base::FilePath(kProcSelfSetgroups));
101 }
102
103 // static
DenySetgroups()104 bool NamespaceUtils::DenySetgroups() {
105 // This function needs to be async-signal-safe.
106 int fd = HANDLE_EINTR(open(kProcSelfSetgroups, O_WRONLY));
107 if (fd == -1) {
108 return false;
109 }
110
111 static const char kDeny[] = "deny";
112 const ssize_t len = sizeof(kDeny) - 1;
113 const ssize_t rc = HANDLE_EINTR(write(fd, kDeny, len));
114 RAW_CHECK(IGNORE_EINTR(close(fd)) == 0);
115 return rc == len;
116 }
117
118 } // namespace sandbox
119