syscall: drop dummy byte for oob in unixgram SendmsgN
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.
Full reference at https:/golang.org/issue/6476#issue-51285243
Fixes #6476
Change-Id: I19a974b4e7920e002bd0556259ab766572358520
Reviewed-on: https://go-review.googlesource.com/45872
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/syscall/creds_test.go b/src/syscall/creds_test.go
index 7c6ab1d..524689a 100644
--- a/src/syscall/creds_test.go
+++ b/src/syscall/creds_test.go
@@ -19,101 +19,116 @@
// sockets. The SO_PASSCRED socket option is enabled on the sending
// socket for this to work.
func TestSCMCredentials(t *testing.T) {
- fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
- if err != nil {
- t.Fatalf("Socketpair: %v", err)
- }
- defer syscall.Close(fds[0])
- defer syscall.Close(fds[1])
-
- err = syscall.SetsockoptInt(fds[0], syscall.SOL_SOCKET, syscall.SO_PASSCRED, 1)
- if err != nil {
- t.Fatalf("SetsockoptInt: %v", err)
+ socketTypeTests := []struct {
+ socketType int
+ dataLen int
+ }{
+ {
+ syscall.SOCK_STREAM,
+ 1,
+ }, {
+ syscall.SOCK_DGRAM,
+ 0,
+ },
}
- srvFile := os.NewFile(uintptr(fds[0]), "server")
- defer srvFile.Close()
- srv, err := net.FileConn(srvFile)
- if err != nil {
- t.Errorf("FileConn: %v", err)
- return
- }
- defer srv.Close()
+ for _, tt := range socketTypeTests {
+ fds, err := syscall.Socketpair(syscall.AF_LOCAL, tt.socketType, 0)
+ if err != nil {
+ t.Fatalf("Socketpair: %v", err)
+ }
+ defer syscall.Close(fds[0])
+ defer syscall.Close(fds[1])
- 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()
+ err = syscall.SetsockoptInt(fds[0], syscall.SOL_SOCKET, syscall.SO_PASSCRED, 1)
+ if err != nil {
+ t.Fatalf("SetsockoptInt: %v", err)
+ }
- var ucred syscall.Ucred
- if os.Getuid() != 0 {
+ srvFile := os.NewFile(uintptr(fds[0]), "server")
+ defer srvFile.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 syscall.Ucred
+ if os.Getuid() != 0 {
+ ucred.Pid = int32(os.Getpid())
+ ucred.Uid = 0
+ ucred.Gid = 0
+ oob := syscall.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)
+ }
+ }
+
ucred.Pid = int32(os.Getpid())
- ucred.Uid = 0
- ucred.Gid = 0
+ ucred.Uid = uint32(os.Getuid())
+ ucred.Gid = uint32(os.Getgid())
oob := syscall.UnixCredentials(&ucred)
- _, _, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
- if op, ok := err.(*net.OpError); ok {
- err = op.Err
+
+ // On SOCK_STREAM, this is internally going to send a dummy byte
+ 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 {
- err = sys.Err
+ if n != 0 {
+ t.Fatalf("WriteMsgUnix n = %d, want 0", n)
}
- if err != syscall.EPERM {
- t.Fatalf("WriteMsgUnix failed with %v, want EPERM", err)
+ if oobn != len(oob) {
+ t.Fatalf("WriteMsgUnix oobn = %d, want %d", oobn, len(oob))
}
- }
- ucred.Pid = int32(os.Getpid())
- ucred.Uid = uint32(os.Getuid())
- ucred.Gid = uint32(os.Getgid())
- oob := syscall.UnixCredentials(&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 != 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
- n, oobn, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
- if err != nil {
- t.Fatalf("WriteMsgUnix: %v", err)
- }
- if n != 0 {
- t.Fatalf("WriteMsgUnix n = %d, want 0", n)
- }
- if oobn != len(oob) {
- t.Fatalf("WriteMsgUnix oobn = %d, want %d", oobn, len(oob))
- }
-
- 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 := syscall.ParseSocketControlMessage(oob2)
- if err != nil {
- t.Fatalf("ParseSocketControlMessage: %v", err)
- }
- newUcred, err := syscall.ParseUnixCredentials(&scm[0])
- if err != nil {
- t.Fatalf("ParseUnixCredentials: %v", err)
- }
- if *newUcred != ucred {
- t.Fatalf("ParseUnixCredentials = %+v, want %+v", newUcred, ucred)
+ scm, err := syscall.ParseSocketControlMessage(oob2)
+ if err != nil {
+ t.Fatalf("ParseSocketControlMessage: %v", err)
+ }
+ newUcred, err := syscall.ParseUnixCredentials(&scm[0])
+ if err != nil {
+ t.Fatalf("ParseUnixCredentials: %v", err)
+ }
+ if *newUcred != ucred {
+ t.Fatalf("ParseUnixCredentials = %+v, want %+v", newUcred, ucred)
+ }
}
}
diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index 4d5a5e1..3c7d378 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -537,8 +537,13 @@
}
var dummy byte
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
- if len(p) == 0 {
+ if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy
iov.SetLen(1)
}
@@ -584,8 +589,13 @@
}
var dummy byte
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
- if len(p) == 0 {
+ if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy
iov.SetLen(1)
}
