go-tg-screenshot-bot

1
// The UnixCredentials system call is currently only implemented on Linux
2
// http://golang.org/src/pkg/syscall/sockcmsg_linux.go
3
// https://golang.org/s/go1.4-syscall
4
// http://code.google.com/p/go/source/browse/unix/sockcmsg_linux.go?repo=sys
5

6
// Local implementation of the UnixCredentials system call for DragonFly BSD
7

8
package dbus
9

10
/*
11
#include <sys/ucred.h>
12
*/
13
import "C"
14

15
import (
16
	"io"
17
	"os"
18
	"syscall"
19
	"unsafe"
20
)
21

22
// http://golang.org/src/pkg/syscall/ztypes_linux_amd64.go
23
// http://golang.org/src/pkg/syscall/ztypes_dragonfly_amd64.go
24
type Ucred struct {
25
	Pid int32
26
	Uid uint32
27
	Gid uint32
28
}
29

30
// http://golang.org/src/pkg/syscall/types_linux.go
31
// http://golang.org/src/pkg/syscall/types_dragonfly.go
32
// https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/ucred.h
33
const (
34
	SizeofUcred = C.sizeof_struct_ucred
35
)
36

37
// http://golang.org/src/pkg/syscall/sockcmsg_unix.go
38
func cmsgAlignOf(salen int) int {
39
	// From http://golang.org/src/pkg/syscall/sockcmsg_unix.go
40
	//salign := sizeofPtr
41
	// NOTE: It seems like 64-bit Darwin and DragonFly BSD kernels
42
	// still require 32-bit aligned access to network subsystem.
43
	//if darwin64Bit || dragonfly64Bit {
44
	//	salign = 4
45
	//}
46
	salign := 4
47
	return (salen + salign - 1) & ^(salign - 1)
48
}
49

50
// http://golang.org/src/pkg/syscall/sockcmsg_unix.go
51
func cmsgData(h *syscall.Cmsghdr) unsafe.Pointer {
52
	return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(syscall.SizeofCmsghdr)))
53
}
54

55
// http://golang.org/src/pkg/syscall/sockcmsg_linux.go
56
// UnixCredentials encodes credentials into a socket control message
57
// for sending to another process. This can be used for
58
// authentication.
59
func UnixCredentials(ucred *Ucred) []byte {
60
	b := make([]byte, syscall.CmsgSpace(SizeofUcred))
61
	h := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
62
	h.Level = syscall.SOL_SOCKET
63
	h.Type = syscall.SCM_CREDS
64
	h.SetLen(syscall.CmsgLen(SizeofUcred))
65
	*((*Ucred)(cmsgData(h))) = *ucred
66
	return b
67
}
68

69
// http://golang.org/src/pkg/syscall/sockcmsg_linux.go
70
// ParseUnixCredentials decodes a socket control message that contains
71
// credentials in a Ucred structure. To receive such a message, the
72
// SO_PASSCRED option must be enabled on the socket.
73
func ParseUnixCredentials(m *syscall.SocketControlMessage) (*Ucred, error) {
74
	if m.Header.Level != syscall.SOL_SOCKET {
75
		return nil, syscall.EINVAL
76
	}
77
	if m.Header.Type != syscall.SCM_CREDS {
78
		return nil, syscall.EINVAL
79
	}
80
	ucred := *(*Ucred)(unsafe.Pointer(&m.Data[0]))
81
	return &ucred, nil
82
}
83

84
func (t *unixTransport) SendNullByte() error {
85
	ucred := &Ucred{Pid: int32(os.Getpid()), Uid: uint32(os.Getuid()), Gid: uint32(os.Getgid())}
86
	b := UnixCredentials(ucred)
87
	_, oobn, err := t.UnixConn.WriteMsgUnix([]byte{0}, b, nil)
88
	if err != nil {
89
		return err
90
	}
91
	if oobn != len(b) {
92
		return io.ErrShortWrite
93
	}
94
	return nil
95
}
96