* fhandler_disk_file.cc (fhandler_disk_file::fchown): Catch an

	error when changing the user account on a standalone Samba server.
	Explain why.
	* sec_acl.cc (setacl): Accommodate additional parameter to set_file_sd.
	* sec_helper.cc (SECURITY_SAMBA_UNIX_AUTHORITY): Define.
	(well_known_samba_unix_user_fake_sid): Define.
	* security.cc (set_file_sd): Take additional parameter if ownership
	should be changed.  Restrict requested permissions accordingly.
	(set_file_attribute): Accommodate additional parameter to set_file_sd.
	* security.h (well_known_samba_unix_user_fake_sid): Declare.
	(set_file_sd): Align declaration to above change.

6 files changed, 56 insertions, 8 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 594efbd..76564cd 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,17 @@
+2009-04-09  Corinna Vinschen  <corinna@vinschen.de>
+
+	* fhandler_disk_file.cc (fhandler_disk_file::fchown): Catch an
+	error when changing the user account on a standalone Samba server.
+	Explain why.
+	* sec_acl.cc (setacl): Accommodate additional parameter to set_file_sd.
+	* sec_helper.cc (SECURITY_SAMBA_UNIX_AUTHORITY): Define.
+	(well_known_samba_unix_user_fake_sid): Define.
+	* security.cc (set_file_sd): Take additional parameter if ownership
+	should be changed.  Restrict requested permissions accordingly.
+	(set_file_attribute): Accommodate additional parameter to set_file_sd.
+	* security.h (well_known_samba_unix_user_fake_sid): Declare.
+	(set_file_sd): Align declaration to above change.
+
 2009-04-07  Corinna Vinschen  <corinna@vinschen.de>
 
 	* include/stdint.h (int_least32_t): Define as int.
diff --git a/winsup/cygwin/fhandler_disk_file.cc b/winsup/cygwin/fhandler_disk_file.cc
index 0ac4ed4..c4c36cc 100644
--- a/winsup/cygwin/fhandler_disk_file.cc
+++ b/winsup/cygwin/fhandler_disk_file.cc
@@ -24,6 +24,7 @@ details. */
 #include "ntdll.h"
 #include "tls_pbuf.h"
 #include "nfs.h"
+#include "pwdgrp.h"
 #include <winioctl.h>
 
 #define _COMPILING_NEWLIB
@@ -870,7 +871,8 @@ fhandler_disk_file::fchown (__uid32_t uid, __gid32_t gid)
   mode_t attrib = 0;
   if (pc.isdir ())
     attrib |= S_IFDIR;
-  int res = get_file_attribute (get_handle (), pc, &attrib, NULL, NULL);
+  __uid32_t old_uid;
+  int res = get_file_attribute (get_handle (), pc, &attrib, &old_uid, NULL);
   if (!res)
     {
       /* Typical Windows default ACLs can contain permissions for one
@@ -883,6 +885,29 @@ fhandler_disk_file::fchown (__uid32_t uid, __gid32_t gid)
       if (pc.issymlink ())
 	attrib = S_IFLNK | STD_RBITS | STD_WBITS;
       res = set_file_attribute (get_handle (), pc, uid, gid, attrib);
+      /* If you're running a Samba server which has no winbidd running, the
+         uid<->SID mapping is disfunctional.  Even trying to chown to your
+	 own account fails since the account used on the server is the UNIX
+	 account which gets used for the standard user mapping.  This is a
+	 default mechanism which doesn't know your real Windows SID.
+	 There are two possible error codes in different Samba releases for
+	 this situation, one of them is unfortunately the not very significant
+	 STATUS_ACCESS_DENIED.  Instead of relying on the error codes, we're
+	 using the below very simple heuristic.  If set_file_attribute failed,
+	 and the original user account was either already unknown, or one of
+	 the standard UNIX accounts, we're faking success. */
+      if (res == -1 && pc.fs_is_samba ())
+	{
+	  cygsid sid;
+
+	  if (old_uid == ILLEGAL_UID
+	      || (sid.getfrompw (internal_getpwuid (old_uid))
+		  && EqualPrefixSid (sid, well_known_samba_unix_user_fake_sid)))
+	    {
+	      debug_printf ("Faking chown worked on standalone Samba");
+	      res = 0;
+	    }
+	}
     }
   if (oret)
     close_fs ();
diff --git a/winsup/cygwin/sec_acl.cc b/winsup/cygwin/sec_acl.cc
index 2496ce0..2a9b4fc 100644
--- a/winsup/cygwin/sec_acl.cc
+++ b/winsup/cygwin/sec_acl.cc
@@ -225,7 +225,7 @@ setacl (HANDLE handle, path_conv &pc, int nentries, __aclent32_t *aclbufp,
       return -1;
     }
   debug_printf ("Created SD-Size: %d", sd_ret.size ());
-  return set_file_sd (handle, pc, sd_ret);
+  return set_file_sd (handle, pc, sd_ret, false);
 }
 
 /* Temporary access denied bits */
diff --git a/winsup/cygwin/sec_helper.cc b/winsup/cygwin/sec_helper.cc
index 1e1657e..63be25c 100644
--- a/winsup/cygwin/sec_helper.cc
+++ b/winsup/cygwin/sec_helper.cc
@@ -67,6 +67,10 @@ MKSID (mandatory_high_integrity_sid, "S-1-16-12288",
        SECURITY_MANDATORY_LABEL_AUTHORITY, 1, SECURITY_MANDATORY_HIGH_RID);
 MKSID (mandatory_system_integrity_sid, "S-1-16-16384",
        SECURITY_MANDATORY_LABEL_AUTHORITY, 1, SECURITY_MANDATORY_SYSTEM_RID);
+/* UNIX accounts on a Samba server have the SID prefix "S-1-22-1" */
+#define SECURITY_SAMBA_UNIX_AUTHORITY {0,0,0,0,0,22}
+MKSID (well_known_samba_unix_user_fake_sid, "S-1-22-1-0",
+       SECURITY_SAMBA_UNIX_AUTHORITY, 2, 1, 0);
 
 bool
 cygpsid::operator== (const char *nsidstr) const
diff --git a/winsup/cygwin/security.cc b/winsup/cygwin/security.cc
index c9de92b..a7d4a56 100644
--- a/winsup/cygwin/security.cc
+++ b/winsup/cygwin/security.cc
@@ -83,7 +83,7 @@ get_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd)
 }
 
 LONG
-set_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd)
+set_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd, bool is_chown)
 {
   NTSTATUS status = STATUS_SUCCESS;
   int retry = 0;
@@ -93,7 +93,10 @@ set_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd)
     {
       if (fh)
 	{
-	  status = NtSetSecurityObject (fh, ALL_SECURITY_INFORMATION, sd);
+	  status = NtSetSecurityObject (fh,
+					is_chown ? ALL_SECURITY_INFORMATION
+						 : DACL_SECURITY_INFORMATION,
+					sd);
 	  if (NT_SUCCESS (status))
 	    {
 	      res = 0;
@@ -104,8 +107,7 @@ set_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd)
 	{
 	  OBJECT_ATTRIBUTES attr;
 	  IO_STATUS_BLOCK io;
-
-	  status = NtOpenFile (&fh, WRITE_OWNER | WRITE_DAC,
+	  status = NtOpenFile (&fh, (is_chown ? WRITE_OWNER  : 0) | WRITE_DAC,
 			       pc.get_object_attr (attr, sec_none_nih),
 			       &io, FILE_SHARE_VALID_FLAGS,
 			       FILE_OPEN_FOR_BACKUP_INTENT
@@ -712,7 +714,8 @@ set_file_attribute (HANDLE handle, path_conv &pc,
 
       if (!get_file_sd (handle, pc, sd)
 	  && alloc_sd (pc, uid, gid, attribute, sd))
-	ret = set_file_sd (handle, pc, sd);
+	ret = set_file_sd (handle, pc, sd,
+			   uid != ILLEGAL_UID || gid != ILLEGAL_GID);
     }
   else
     ret = 0;
diff --git a/winsup/cygwin/security.h b/winsup/cygwin/security.h
index f186597..9d306fe 100644
--- a/winsup/cygwin/security.h
+++ b/winsup/cygwin/security.h
@@ -327,6 +327,7 @@ extern cygpsid fake_logon_sid;
 extern cygpsid mandatory_medium_integrity_sid;
 extern cygpsid mandatory_high_integrity_sid;
 extern cygpsid mandatory_system_integrity_sid;
+extern cygpsid well_known_samba_unix_user_fake_sid;
 
 bool privilege_luid (const PWCHAR pname, LUID *luid);
 
@@ -345,7 +346,8 @@ int __stdcall set_file_attribute (HANDLE, path_conv &,
 				  __uid32_t, __gid32_t, int);
 int __stdcall get_reg_attribute (HKEY hkey, mode_t *, __uid32_t *, __gid32_t *);
 LONG __stdcall get_file_sd (HANDLE fh, path_conv &, security_descriptor &sd);
-LONG __stdcall set_file_sd (HANDLE fh, path_conv &, security_descriptor &sd);
+LONG __stdcall set_file_sd (HANDLE fh, path_conv &, security_descriptor &sd,
+			    bool is_chown);
 bool __stdcall add_access_allowed_ace (PACL acl, int offset, DWORD attributes, PSID sid, size_t &len_add, DWORD inherit);
 bool __stdcall add_access_denied_ace (PACL acl, int offset, DWORD attributes, PSID sid, size_t &len_add, DWORD inherit);
 int __stdcall check_file_access (path_conv &, int);