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
|
package binder
import (
"fmt"
"io"
"log/slog"
"net"
"os"
"os/user"
"strconv"
"syscall"
g "gobang"
)
type _CLIArgs struct {
fromAddr string
toAddr string
}
const _USER = "nobody"
var emitActiveConnection = g.MakeGauge("active-connections")
func dropPrivileges(username string) {
g.Info("Dropping privileges", "drop-root-init")
user, err := user.Lookup(username)
g.FatalIf(err)
gid, err := strconv.Atoi(user.Gid)
g.FatalIf(err)
uid, err := strconv.Atoi(user.Uid)
g.FatalIf(err)
err = syscall.Setgid(gid)
g.FatalIf(err)
err = syscall.Setgroups([]int{})
g.FatalIf(err)
err = syscall.Setuid(uid)
g.FatalIf(err)
g.Info("Privileges dropped", "drop-root-end")
}
func isRunningAsRoot() bool {
return os.Geteuid() == 0
}
func dropRoot() {
if isRunningAsRoot() {
dropPrivileges(_USER)
if isRunningAsRoot() {
panic("Failed to drop privileges")
}
}
}
func parseArgs(args []string) _CLIArgs {
if len(args) != 3 {
fmt.Fprintf(
os.Stderr,
"Usage: %s FROM-ADDRESS TO-ADDRESS\n",
args[0],
)
os.Exit(2)
}
return _CLIArgs {
fromAddr: args[1],
toAddr: args[2],
}
}
func listen(fromAddr string) net.Listener {
listener, err := net.Listen("tcp", fromAddr)
g.FatalIf(err)
g.Info("Started listening", "listen-start", "from-address", fromAddr)
return listener
}
func copyData(c chan struct {}, from io.Reader, to io.WriteCloser) {
io.Copy(to, from)
c <- struct {} {}
}
func start(toAddr string, listener net.Listener) {
for {
connFrom, err := listener.Accept()
if err != nil {
g.Warning(
"Error accepting connection",
"accept-connection-error",
"err", err,
)
continue
}
defer connFrom.Close()
emitActiveConnection.Inc()
connTo, err := net.Dial("unix", toAddr)
if err != nil {
g.Warning(
"Error dialing connection",
"dial-connection-error",
"err", err,
)
connFrom.Close()
continue
}
defer connTo.Close()
c := make(chan struct {})
go copyData(c, connFrom, connTo)
go copyData(c, connTo, connFrom)
go func() {
<- c
emitActiveConnection.Dec()
}()
}
}
func Main() {
g.Init(slog.Group("versions", "gobang", g.Version, "this", Version))
args := parseArgs(os.Args)
listener := listen(args.fromAddr)
dropRoot()
start(args.toAddr, listener)
}
|
