]> Cypherpunks repositories - gostls13.git/commitdiff
syscall: drop dummy byte for oob in unixgram SendmsgN
authorLuca Bruno <luca.bruno@coreos.com>
Thu, 15 Jun 2017 11:35:43 +0000 (11:35 +0000)
committerIan Lance Taylor <iant@golang.org>
Tue, 29 Aug 2017 23:30:21 +0000 (23:30 +0000)
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>

src/syscall/creds_test.go
src/syscall/syscall_linux.go

index 7c6ab1de1de3fa5064ee95be7155cba07fb3b1f5..524689ae2d233902018914c4bbb510ba08aa0105 100644 (file)
@@ -19,101 +19,116 @@ import (
 // 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)
+       socketTypeTests := []struct {
+               socketType int
+               dataLen    int
+       }{
+               {
+                       syscall.SOCK_STREAM,
+                       1,
+               }, {
+                       syscall.SOCK_DGRAM,
+                       0,
+               },
        }
-       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)
-       }
+       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])
 
-       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()
+               err = syscall.SetsockoptInt(fds[0], syscall.SOL_SOCKET, syscall.SO_PASSCRED, 1)
+               if err != nil {
+                       t.Fatalf("SetsockoptInt: %v", err)
+               }
 
-       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()
+               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)
+                       }
+               }
 
-       var ucred syscall.Ucred
-       if os.Getuid() != 0 {
                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)
-
-       // 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")
-       }
+               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")
+               }
 
-       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)
+               }
        }
 }
index 4d5a5e12d321b10a186d19c2d27e854baf05c3c4..3c7d378d7184582c25b958b092a0a88c2bb9c76a 100644 (file)
@@ -537,8 +537,13 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
        }
        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 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
        }
        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)
                }