syscall: allow \x00-prefixed unix abstract socket to use full path length

src/net/unixsock_linux_test.go

@@ -49,6 +49,24 @@ func TestUnixAutobindClose(t *testing.T) {
 	ln.Close()
 }
 
+func TestUnixAbstractLongNameeNullStart(t *testing.T) {
+	addr := "\x00abstract_test"
+	rsu := syscall.RawSockaddrUnix{}
+	paddedAddr := make([]byte, len(rsu.Path))
+	copy(paddedAddr, "\x00abstract_test")
+	addr = string(paddedAddr)
+
+	la, err := ResolveUnixAddr("unix", addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := ListenUnix("unix", la)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+}
+
 func TestUnixgramLinuxAbstractLongName(t *testing.T) {
 	if !testableNetwork("unixgram") {
 		t.Skip("abstract unix socket long name test")

src/net/unixsock_windows_test.go

@@ -10,6 +10,7 @@ import (
 	"internal/syscall/windows"
 	"os"
 	"reflect"
+	"syscall"
 	"testing"
 )
 
@@ -69,6 +70,28 @@ func TestUnixConnLocalWindows(t *testing.T) {
 	}
 }
 
+func TestUnixAbstractLongNameNullStart(t *testing.T) {
+	if !windows.SupportUnixSocket() {
+		t.Skip("unix test")
+	}
+
+	addr := "\x00abstract_test"
+	rsu := syscall.RawSockaddrUnix{}
+	paddedAddr := make([]byte, len(rsu.Path))
+	copy(paddedAddr, "\x00abstract_test")
+	addr = string(paddedAddr)
+
+	la, err := ResolveUnixAddr("unix", addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := ListenUnix("unix", la)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+}
+
 func TestModeSocket(t *testing.T) {
 	if !windows.SupportUnixSocket() {
 		t.Skip("unix test")

src/syscall/syscall_linux.go

@@ -554,7 +554,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > len(sa.raw.Path) {
 		return nil, 0, EINVAL
 	}
-	if n == len(sa.raw.Path) && name[0] != '@' {
+	isAbstract := n > 0 && (name[0] == '@' || name[0] == '\x00')
+	if n == len(sa.raw.Path) && !isAbstract {
 		return nil, 0, EINVAL
 	}
 	sa.raw.Family = AF_UNIX
@@ -566,8 +567,7 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > 0 {
 		sl += _Socklen(n) + 1
 	}
-	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
-		// Check sl > 3 so we don't change unnamed socket behavior.
+	if isAbstract {
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--

src/syscall/syscall_windows.go

@@ -856,7 +856,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
 	if n > len(sa.raw.Path) {
 		return nil, 0, EINVAL
 	}
-	if n == len(sa.raw.Path) && name[0] != '@' {
+	isAbstract := n > 0 && (name[0] == '@' || name[0] == '\x00')
+	if n == len(sa.raw.Path) && !isAbstract {
 		return nil, 0, EINVAL
 	}
 	sa.raw.Family = AF_UNIX
@@ -868,8 +869,7 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
 	if n > 0 {
 		sl += int32(n) + 1
 	}
-	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
-		// Check sl > 3 so we don't change unnamed socket behavior.
+	if isAbstract {
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--