win32: fake file ownership on FAT filesystems

busybox-w32 tries to display the ownership of files by comparing
the security identifier (SID) of the current user with that of the
file on disk.  For filesystems that don't support SIDs this resulted
in files being listed as owned by root.

It appears that filesystems without support for file ownership
return a null SID.  In such cases pretend the file belongs to the
current user.

GitHub issue #241.

1 files changed, 11 insertions, 5 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 06da37040..f34ea1102 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -488,9 +488,14 @@ static uid_t file_owner(HANDLE fh)
         uid_t uid = 0;
         DWORD *ptr;
         unsigned char prefix[] = {
-                        0x01, 0x05, 0x00, 0x00,
-                        0x00, 0x00, 0x00, 0x05,
-                        0x15, 0x00, 0x00, 0x00
+                0x01, 0x05, 0x00, 0x00,
+                0x00, 0x00, 0x00, 0x05,
+                0x15, 0x00, 0x00, 0x00
+        };
+        unsigned char nullsid[] = {
+                0x01, 0x01, 0x00, 0x00,
+                0x00, 0x00, 0x00, 0x01,
+                0x00, 0x00, 0x00, 0x00
         };
 
         /*  get SID of current user */
@@ -520,8 +525,9 @@ static uid_t file_owner(HANDLE fh)
 
         if (EqualSid(pSidOwner, user->User.Sid)) {
                 uid = DEFAULT_UID;
-        }
-        else if (memcmp(pSidOwner, prefix, sizeof(prefix)) == 0) {
+        } else if (memcmp(pSidOwner, nullsid, sizeof(nullsid)) == 0) {
+                uid = DEFAULT_UID;
+        } else if (memcmp(pSidOwner, prefix, sizeof(prefix)) == 0) {
                 /* for local or domain users use the RID as uid */
                 ptr = (DWORD *)pSidOwner;
                 if (ptr[6] >= 500 && ptr[6] < DEFAULT_UID)