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 FreeBSD
7

8
package dbus
9

10
/*
11
const int sizeofPtr = sizeof(void*);
12
#define _WANT_UCRED
13
#include <sys/types.h>
14
#include <sys/ucred.h>
15
*/
16
import "C"
17

18
import (
19
	"io"
20
	"os"
21
	"syscall"
22
	"unsafe"
23
)
24

25
// http://golang.org/src/pkg/syscall/ztypes_linux_amd64.go
26
// https://golang.org/src/syscall/ztypes_freebsd_amd64.go
27
type Ucred struct {
28
	Pid int32
29
	Uid uint32
30
	Gid uint32
31
}
32

33
// http://golang.org/src/pkg/syscall/types_linux.go
34
// https://golang.org/src/syscall/types_freebsd.go
35
// https://github.com/freebsd/freebsd/blob/master/sys/sys/ucred.h
36
const (
37
	SizeofUcred = C.sizeof_struct_ucred
38
)
39

40
// http://golang.org/src/pkg/syscall/sockcmsg_unix.go
41
func cmsgAlignOf(salen int) int {
42
	salign := C.sizeofPtr
43

44
	return (salen + salign - 1) & ^(salign - 1)
45
}
46

47
// http://golang.org/src/pkg/syscall/sockcmsg_unix.go
48
func cmsgData(h *syscall.Cmsghdr) unsafe.Pointer {
49
	return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(syscall.SizeofCmsghdr)))
50
}
51

52
// http://golang.org/src/pkg/syscall/sockcmsg_linux.go
53
// UnixCredentials encodes credentials into a socket control message
54
// for sending to another process. This can be used for
55
// authentication.
56
func UnixCredentials(ucred *Ucred) []byte {
57
	b := make([]byte, syscall.CmsgSpace(SizeofUcred))
58
	h := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
59
	h.Level = syscall.SOL_SOCKET
60
	h.Type = syscall.SCM_CREDS
61
	h.SetLen(syscall.CmsgLen(SizeofUcred))
62
	*((*Ucred)(cmsgData(h))) = *ucred
63
	return b
64
}
65

66
// http://golang.org/src/pkg/syscall/sockcmsg_linux.go
67
// ParseUnixCredentials decodes a socket control message that contains
68
// credentials in a Ucred structure. To receive such a message, the
69
// SO_PASSCRED option must be enabled on the socket.
70
func ParseUnixCredentials(m *syscall.SocketControlMessage) (*Ucred, error) {
71
	if m.Header.Level != syscall.SOL_SOCKET {
72
		return nil, syscall.EINVAL
73
	}
74
	if m.Header.Type != syscall.SCM_CREDS {
75
		return nil, syscall.EINVAL
76
	}
77
	ucred := *(*Ucred)(unsafe.Pointer(&m.Data[0]))
78
	return &ucred, nil
79
}
80

81
func (t *unixTransport) SendNullByte() error {
82
	ucred := &Ucred{Pid: int32(os.Getpid()), Uid: uint32(os.Getuid()), Gid: uint32(os.Getgid())}
83
	b := UnixCredentials(ucred)
84
	_, oobn, err := t.UnixConn.WriteMsgUnix([]byte{0}, b, nil)
85
	if err != nil {
86
		return err
87
	}
88
	if oobn != len(b) {
89
		return io.ErrShortWrite
90
	}
91
	return nil
92
}
93