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unix: drop dummy byte for oob in unixgram SendmsgN

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This commit relaxes SendmsgN behavior of introducing a dummy 1-byte
payload when sending ancillary-only messages.
The fake payload is not needed for SOCK_DGRAM type sockets, and actually
breaks interoperability with other fd-passing software (journald is one
known example). This introduces an additional check to avoid injecting
dummy payload in such case.

Backport of https://go.googlesource.com/go/+/93da0b6e66f24c4c307e0df37ceb102a33306174
Full reference at https:/golang.org/issue/6476#issue-51285243

Change-Id: I7cf00a1c7cde75fe62e00b98ccba6ac8469b0493
Reviewed-on: https://go-review.googlesource.com/60190
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Luca Bruno
2017-08-30 13:42:02 +00:00
committed by Ian Lance Taylor
parent ab9e364efd
commit bb24a47a89
2 changed files with 112 additions and 87 deletions
Download Patch File Download Diff File Expand all files Collapse all files
unix/creds_test.go
+100 -85
View File
@@ -21,101 +21,116 @@ import (
// sockets. The SO_PASSCRED socket option is enabled on the sending // sockets. The SO_PASSCRED socket option is enabled on the sending
// socket for this to work. // socket for this to work.
func TestSCMCredentials(t *testing.T) { func TestSCMCredentials(t *testing.T) {
fds, err := unix.Socketpair(unix.AF_LOCAL, unix.SOCK_STREAM, 0) socketTypeTests := []struct {
if err != nil { socketType int
t.Fatalf("Socketpair: %v", err) dataLen int
} }{
defer unix.Close(fds[0]) {
defer unix.Close(fds[1]) unix.SOCK_STREAM,
1,
err = unix.SetsockoptInt(fds[0], unix.SOL_SOCKET, unix.SO_PASSCRED, 1) }, {
if err != nil { unix.SOCK_DGRAM,
t.Fatalf("SetsockoptInt: %v", err) 0,
},
} }
srvFile := os.NewFile(uintptr(fds[0]), "server") for _, tt := range socketTypeTests {
defer srvFile.Close() fds, err := unix.Socketpair(unix.AF_LOCAL, tt.socketType, 0)
srv, err := net.FileConn(srvFile) if err != nil {
if err != nil { t.Fatalf("Socketpair: %v", err)
t.Errorf("FileConn: %v", err) }
return defer unix.Close(fds[0])
} defer unix.Close(fds[1])
defer srv.Close()
cliFile := os.NewFile(uintptr(fds[1]), "client") err = unix.SetsockoptInt(fds[0], unix.SOL_SOCKET, unix.SO_PASSCRED, 1)
defer cliFile.Close() if err != nil {
cli, err := net.FileConn(cliFile) t.Fatalf("SetsockoptInt: %v", err)
if err != nil { }
t.Errorf("FileConn: %v", err)
return srvFile := os.NewFile(uintptr(fds[0]), "server")
} defer srvFile.Close()
defer cli.Close() srv, err := net.FileConn(srvFile)
if err != nil {
t.Errorf("FileConn: %v", err)
return
}
defer srv.Close()
cliFile := os.NewFile(uintptr(fds[1]), "client")
defer cliFile.Close()
cli, err := net.FileConn(cliFile)
if err != nil {
t.Errorf("FileConn: %v", err)
return
}
defer cli.Close()
var ucred unix.Ucred
if os.Getuid() != 0 {
ucred.Pid = int32(os.Getpid())
ucred.Uid = 0
ucred.Gid = 0
oob := unix.UnixCredentials(&ucred)
_, _, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
if op, ok := err.(*net.OpError); ok {
err = op.Err
}
if sys, ok := err.(*os.SyscallError); ok {
err = sys.Err
}
if err != syscall.EPERM {
t.Fatalf("WriteMsgUnix failed with %v, want EPERM", err)
}
}
var ucred unix.Ucred
if os.Getuid() != 0 {
ucred.Pid = int32(os.Getpid()) ucred.Pid = int32(os.Getpid())
ucred.Uid = 0 ucred.Uid = uint32(os.Getuid())
ucred.Gid = 0 ucred.Gid = uint32(os.Getgid())
oob := unix.UnixCredentials(&ucred) oob := unix.UnixCredentials(&ucred)
_, _, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
if op, ok := err.(*net.OpError); ok { // On SOCK_STREAM, this is internally going to send a dummy byte
err = op.Err n, oobn, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
if err != nil {
t.Fatalf("WriteMsgUnix: %v", err)
} }
if sys, ok := err.(*os.SyscallError); ok { if n != 0 {
err = sys.Err t.Fatalf("WriteMsgUnix n = %d, want 0", n)
} }
if err != syscall.EPERM { if oobn != len(oob) {
t.Fatalf("WriteMsgUnix failed with %v, want EPERM", err) t.Fatalf("WriteMsgUnix oobn = %d, want %d", oobn, len(oob))
} }
}
ucred.Pid = int32(os.Getpid()) oob2 := make([]byte, 10*len(oob))
ucred.Uid = uint32(os.Getuid()) n, oobn2, flags, _, err := srv.(*net.UnixConn).ReadMsgUnix(nil, oob2)
ucred.Gid = uint32(os.Getgid()) if err != nil {
oob := unix.UnixCredentials(&ucred) t.Fatalf("ReadMsgUnix: %v", err)
}
if flags != 0 {
t.Fatalf("ReadMsgUnix flags = 0x%x, want 0", flags)
}
if n != tt.dataLen {
t.Fatalf("ReadMsgUnix n = %d, want %d", n, tt.dataLen)
}
if oobn2 != oobn {
// without SO_PASSCRED set on the socket, ReadMsgUnix will
// return zero oob bytes
t.Fatalf("ReadMsgUnix oobn = %d, want %d", oobn2, oobn)
}
oob2 = oob2[:oobn2]
if !bytes.Equal(oob, oob2) {
t.Fatal("ReadMsgUnix oob bytes don't match")
}
// this is going to send a dummy byte scm, err := unix.ParseSocketControlMessage(oob2)
n, oobn, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil) if err != nil {
if err != nil { t.Fatalf("ParseSocketControlMessage: %v", err)
t.Fatalf("WriteMsgUnix: %v", err) }
} newUcred, err := unix.ParseUnixCredentials(&scm[0])
if n != 0 { if err != nil {
t.Fatalf("WriteMsgUnix n = %d, want 0", n) t.Fatalf("ParseUnixCredentials: %v", err)
} }
if oobn != len(oob) { if *newUcred != ucred {
t.Fatalf("WriteMsgUnix oobn = %d, want %d", oobn, len(oob)) t.Fatalf("ParseUnixCredentials = %+v, want %+v", newUcred, ucred)
} }
oob2 := make([]byte, 10*len(oob))
n, oobn2, flags, _, err := srv.(*net.UnixConn).ReadMsgUnix(nil, oob2)
if err != nil {
t.Fatalf("ReadMsgUnix: %v", err)
}
if flags != 0 {
t.Fatalf("ReadMsgUnix flags = 0x%x, want 0", flags)
}
if n != 1 {
t.Fatalf("ReadMsgUnix n = %d, want 1 (dummy byte)", n)
}
if oobn2 != oobn {
// without SO_PASSCRED set on the socket, ReadMsgUnix will
// return zero oob bytes
t.Fatalf("ReadMsgUnix oobn = %d, want %d", oobn2, oobn)
}
oob2 = oob2[:oobn2]
if !bytes.Equal(oob, oob2) {
t.Fatal("ReadMsgUnix oob bytes don't match")
}
scm, err := unix.ParseSocketControlMessage(oob2)
if err != nil {
t.Fatalf("ParseSocketControlMessage: %v", err)
}
newUcred, err := unix.ParseUnixCredentials(&scm[0])
if err != nil {
t.Fatalf("ParseUnixCredentials: %v", err)
}
if *newUcred != ucred {
t.Fatalf("ParseUnixCredentials = %+v, want %+v", newUcred, ucred)
} }
} }
unix/syscall_linux.go
+12 -2
View File
@@ -931,8 +931,13 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
} }
var dummy byte var dummy byte
if len(oob) > 0 { if len(oob) > 0 {
var sockType int
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
if err != nil {
return
}
// receive at least one normal byte // receive at least one normal byte
if len(p) == 0 { if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy iov.Base = &dummy
iov.SetLen(1) iov.SetLen(1)
} }
@@ -978,8 +983,13 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
} }
var dummy byte var dummy byte
if len(oob) > 0 { if len(oob) > 0 {
var sockType int
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
if err != nil {
return 0, err
}
// send at least one normal byte // send at least one normal byte
if len(p) == 0 { if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy iov.Base = &dummy
iov.SetLen(1) iov.SetLen(1)
} }