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
|
package validate
import (
"fmt"
"os"
"reflect"
"strings"
"github.com/opencontainers/runc/libcontainer/configs"
)
var (
geteuid = os.Geteuid
getegid = os.Getegid
)
func (v *ConfigValidator) rootless(config *configs.Config) error {
if err := rootlessMappings(config); err != nil {
return err
}
if err := rootlessMount(config); err != nil {
return err
}
// Currently, cgroups cannot effectively be used in rootless containers.
// The new cgroup namespace doesn't really help us either because it doesn't
// have nice interactions with the user namespace (we're working with upstream
// to fix this).
if err := rootlessCgroup(config); err != nil {
return err
}
// XXX: We currently can't verify the user config at all, because
// configs.Config doesn't store the user-related configs. So this
// has to be verified by setupUser() in init_linux.go.
return nil
}
func rootlessMappings(config *configs.Config) error {
rootuid, err := config.HostRootUID()
if err != nil {
return fmt.Errorf("failed to get root uid from uidMappings: %v", err)
}
if euid := geteuid(); euid != 0 {
if !config.Namespaces.Contains(configs.NEWUSER) {
return fmt.Errorf("rootless containers require user namespaces")
}
if rootuid != euid {
return fmt.Errorf("rootless containers cannot map container root to a different host user")
}
}
rootgid, err := config.HostRootGID()
if err != nil {
return fmt.Errorf("failed to get root gid from gidMappings: %v", err)
}
// Similar to the above test, we need to make sure that we aren't trying to
// map to a group ID that we don't have the right to be.
if rootgid != getegid() {
return fmt.Errorf("rootless containers cannot map container root to a different host group")
}
// We can only map one user and group inside a container (our own).
if len(config.UidMappings) != 1 || config.UidMappings[0].Size != 1 {
return fmt.Errorf("rootless containers cannot map more than one user")
}
if len(config.GidMappings) != 1 || config.GidMappings[0].Size != 1 {
return fmt.Errorf("rootless containers cannot map more than one group")
}
return nil
}
// cgroup verifies that the user isn't trying to set any cgroup limits or paths.
func rootlessCgroup(config *configs.Config) error {
// Nothing set at all.
if config.Cgroups == nil || config.Cgroups.Resources == nil {
return nil
}
// Used for comparing to the zero value.
left := reflect.ValueOf(*config.Cgroups.Resources)
right := reflect.Zero(left.Type())
// This is all we need to do, since specconv won't add cgroup options in
// rootless mode.
if !reflect.DeepEqual(left.Interface(), right.Interface()) {
return fmt.Errorf("cannot specify resource limits in rootless container")
}
return nil
}
// mount verifies that the user isn't trying to set up any mounts they don't have
// the rights to do. In addition, it makes sure that no mount has a `uid=` or
// `gid=` option that doesn't resolve to root.
func rootlessMount(config *configs.Config) error {
// XXX: We could whitelist allowed devices at this point, but I'm not
// convinced that's a good idea. The kernel is the best arbiter of
// access control.
for _, mount := range config.Mounts {
// Check that the options list doesn't contain any uid= or gid= entries
// that don't resolve to root.
for _, opt := range strings.Split(mount.Data, ",") {
if strings.HasPrefix(opt, "uid=") && opt != "uid=0" {
return fmt.Errorf("cannot specify uid= mount options in rootless containers where argument isn't 0")
}
if strings.HasPrefix(opt, "gid=") && opt != "gid=0" {
return fmt.Errorf("cannot specify gid= mount options in rootless containers where argument isn't 0")
}
}
}
return nil
}
|
