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
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
|
// +build linux
package chrootuser
import (
"bufio"
"errors"
"flag"
"fmt"
"io"
"os"
"os/exec"
"os/user"
"strconv"
"strings"
"sync"
"github.com/containers/storage/pkg/reexec"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)
const (
openChrootedCommand = "chrootuser-open"
)
func init() {
reexec.Register(openChrootedCommand, openChrootedFileMain)
}
func openChrootedFileMain() {
status := 0
flag.Parse()
if len(flag.Args()) < 1 {
os.Exit(1)
}
// Our first parameter is the directory to chroot into.
if err := unix.Chdir(flag.Arg(0)); err != nil {
fmt.Fprintf(os.Stderr, "chdir(): %v", err)
os.Exit(1)
}
if err := unix.Chroot(flag.Arg(0)); err != nil {
fmt.Fprintf(os.Stderr, "chroot(): %v", err)
os.Exit(1)
}
// Anything else is a file we want to dump out.
for _, filename := range flag.Args()[1:] {
f, err := os.Open(filename)
if err != nil {
fmt.Fprintf(os.Stderr, "open(%q): %v", filename, err)
status = 1
continue
}
_, err = io.Copy(os.Stdout, f)
if err != nil {
fmt.Fprintf(os.Stderr, "read(%q): %v", filename, err)
}
f.Close()
}
os.Exit(status)
}
func openChrootedFile(rootdir, filename string) (*exec.Cmd, io.ReadCloser, error) {
// The child process expects a chroot and one or more filenames that
// will be consulted relative to the chroot directory and concatenated
// to its stdout. Start it up.
cmd := reexec.Command(openChrootedCommand, rootdir, filename)
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, nil, err
}
err = cmd.Start()
if err != nil {
return nil, nil, err
}
// Hand back the child's stdout for reading, and the child to reap.
return cmd, stdout, nil
}
var (
lookupUser, lookupGroup sync.Mutex
// ErrNoSuchUser indicates that the user provided by the caller does not
// exist in /etc/passws
ErrNoSuchUser = errors.New("user does not exist in /etc/passwd")
)
type lookupPasswdEntry struct {
name string
uid uint64
gid uint64
}
type lookupGroupEntry struct {
name string
gid uint64
user string
}
func readWholeLine(rc *bufio.Reader) ([]byte, error) {
line, isPrefix, err := rc.ReadLine()
if err != nil {
return nil, err
}
for isPrefix {
// We didn't get a whole line. Keep reading chunks until we find an end of line, and discard them.
for isPrefix {
logrus.Debugf("discarding partial line %q", string(line))
_, isPrefix, err = rc.ReadLine()
if err != nil {
return nil, err
}
}
// That last read was the end of a line, so now we try to read the (beginning of?) the next line.
line, isPrefix, err = rc.ReadLine()
if err != nil {
return nil, err
}
}
return line, nil
}
func parseNextPasswd(rc *bufio.Reader) *lookupPasswdEntry {
line, err := readWholeLine(rc)
if err != nil {
return nil
}
fields := strings.Split(string(line), ":")
if len(fields) < 7 {
return nil
}
uid, err := strconv.ParseUint(fields[2], 10, 32)
if err != nil {
return nil
}
gid, err := strconv.ParseUint(fields[3], 10, 32)
if err != nil {
return nil
}
return &lookupPasswdEntry{
name: fields[0],
uid: uid,
gid: gid,
}
}
func parseNextGroup(rc *bufio.Reader) *lookupGroupEntry {
line, err := readWholeLine(rc)
if err != nil {
return nil
}
fields := strings.Split(string(line), ":")
if len(fields) < 4 {
return nil
}
gid, err := strconv.ParseUint(fields[2], 10, 32)
if err != nil {
return nil
}
return &lookupGroupEntry{
name: fields[0],
gid: gid,
user: fields[3],
}
}
func lookupUserInContainer(rootdir, username string) (uid uint64, gid uint64, err error) {
cmd, f, err := openChrootedFile(rootdir, "/etc/passwd")
if err != nil {
return 0, 0, err
}
defer func() {
_ = cmd.Wait()
}()
rc := bufio.NewReader(f)
defer f.Close()
lookupUser.Lock()
defer lookupUser.Unlock()
pwd := parseNextPasswd(rc)
for pwd != nil {
if pwd.name != username {
pwd = parseNextPasswd(rc)
continue
}
return pwd.uid, pwd.gid, nil
}
return 0, 0, user.UnknownUserError(fmt.Sprintf("error looking up user %q", username))
}
func lookupGroupForUIDInContainer(rootdir string, userid uint64) (username string, gid uint64, err error) {
cmd, f, err := openChrootedFile(rootdir, "/etc/passwd")
if err != nil {
return "", 0, err
}
defer func() {
_ = cmd.Wait()
}()
rc := bufio.NewReader(f)
defer f.Close()
lookupUser.Lock()
defer lookupUser.Unlock()
pwd := parseNextPasswd(rc)
for pwd != nil {
if pwd.uid != userid {
pwd = parseNextPasswd(rc)
continue
}
return pwd.name, pwd.gid, nil
}
return "", 0, ErrNoSuchUser
}
func lookupAdditionalGroupsForUIDInContainer(rootdir string, userid uint64) (gid []uint32, err error) {
// Get the username associated with userid
username, _, err := lookupGroupForUIDInContainer(rootdir, userid)
if err != nil {
return nil, err
}
cmd, f, err := openChrootedFile(rootdir, "/etc/group")
if err != nil {
return nil, err
}
defer func() {
_ = cmd.Wait()
}()
rc := bufio.NewReader(f)
defer f.Close()
lookupGroup.Lock()
defer lookupGroup.Unlock()
grp := parseNextGroup(rc)
for grp != nil {
if strings.Contains(grp.user, username) {
gid = append(gid, uint32(grp.gid))
}
grp = parseNextGroup(rc)
}
return gid, nil
}
func lookupGroupInContainer(rootdir, groupname string) (gid uint64, err error) {
cmd, f, err := openChrootedFile(rootdir, "/etc/group")
if err != nil {
return 0, err
}
defer func() {
_ = cmd.Wait()
}()
rc := bufio.NewReader(f)
defer f.Close()
lookupGroup.Lock()
defer lookupGroup.Unlock()
grp := parseNextGroup(rc)
for grp != nil {
if grp.name != groupname {
grp = parseNextGroup(rc)
continue
}
return grp.gid, nil
}
return 0, user.UnknownGroupError(fmt.Sprintf("error looking up group %q", groupname))
}
|
