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
|
/*
* privileges.go - Functions for managing users and privileges.
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
// Package security manages:
// - Cache clearing (cache.go)
// - Keyring Operations (keyring.go)
// - Privilege manipulation (privileges.go)
// - Maintaining the link between the root and user keyrings.
package security
import (
"log"
"os"
"os/user"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
"github.com/google/fscrypt/util"
)
// SetThreadPrivileges temporarily drops the privileges of the current thread to
// have the effective uid/gid of the target user. The privileges can be changed
// again with another call to SetThreadPrivileges.
func SetThreadPrivileges(target *user.User) error {
euid := util.AtoiOrPanic(target.Uid)
egid := util.AtoiOrPanic(target.Gid)
if os.Geteuid() == euid {
log.Printf("Privileges already set to %q", target.Username)
return nil
}
log.Printf("Setting privileges to %q", target.Username)
// If setting privs to root, we want to set the uid first, so we will
// then have the necessary permissions to perform the other actions.
if euid == 0 {
if err := setUids(-1, euid); err != nil {
return err
}
}
if err := setGids(-1, egid); err != nil {
return err
}
if err := setGroups(target); err != nil {
return err
}
// If not setting privs to root, we want to avoid dropping the uid
// util the very end.
if euid != 0 {
if err := setUids(-1, euid); err != nil {
return err
}
}
return nil
}
func setUids(ruid, euid int) error {
err := unix.Setreuid(ruid, euid)
log.Printf("Setreuid(%d, %d) = %v", ruid, euid, err)
return errors.Wrapf(err, "setting uids")
}
func setGids(rgid, egid int) error {
err := unix.Setregid(rgid, egid)
log.Printf("Setregid(%d, %d) = %v", rgid, egid, err)
return errors.Wrapf(err, "setting gids")
}
func setGroups(target *user.User) error {
groupStrings, err := target.GroupIds()
if err != nil {
return util.SystemError(err.Error())
}
gids := make([]int, len(groupStrings))
for i, groupString := range groupStrings {
gids[i] = util.AtoiOrPanic(groupString)
}
err = unix.Setgroups(gids)
log.Printf("Setgroups(%v) = %v", gids, err)
return errors.Wrapf(err, "setting groups")
}
|
