diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 95f7d5efd..fc0a07ad9 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,15 @@
+2002-06-05  Corinna Vinschen  <corinna@vinschen.de>
+
+	* grp.cc (read_etc_group): When emulating nonexisting group file on
+	NT systems, read primary group SID from process token.  Use that info
+	to create correct group entry.  On error or on 9x systems fallback
+	to emulating Administrators group as before.
+	(read_etc_passwd): When emulating nonexisting passwd file on NT systems,
+	read user and primary group SID from process token.  Use that info to
+	create correct passwd entry.  On error or on 9x systems fallback to
+	emulating user with Administrator user id and Administrators group
+	as before.
+
 2002-06-05  Corinna Vinschen  <corinna@vinschen.de>
 
 	* grp.cc (etc_group): Removed.
diff --git a/winsup/cygwin/grp.cc b/winsup/cygwin/grp.cc
index 13f74dd64..25d2ff864 100644
--- a/winsup/cygwin/grp.cc
+++ b/winsup/cygwin/grp.cc
@@ -171,19 +171,49 @@ read_etc_group ()
 	  SID_NAME_USE acType;
 	  static char linebuf [200];
 
-	  debug_printf ("Emulating /etc/group");
-	  strncpy (group_name, "Administrators", sizeof (group_name));
-	  if (! LookupAccountSidA (NULL, well_known_admins_sid, group_name,
-				   &group_name_len, domain_name,
-				   &domain_name_len, &acType))
+	  if (wincap.has_security ())
 	    {
-	      strcpy (group_name, "unknown");
-	      debug_printf ("Failed to get local admins group name. %E");
+	      HANDLE ptok;
+	      cygsid tg;
+	      DWORD siz;
+
+	      if (OpenProcessToken (GetCurrentProcess (), TOKEN_QUERY, &ptok))
+	        {
+		  if (GetTokenInformation (ptok, TokenPrimaryGroup, &tg,
+					   sizeof tg, &siz)
+		      && LookupAccountSidA (NULL, tg, group_name,
+					    &group_name_len, domain_name,
+				            &domain_name_len, &acType))
+		    {
+		      char strbuf[100];
+		      snprintf (linebuf, sizeof (linebuf), "%s:%s:%u:",
+		      		group_name, 
+				tg.string (strbuf),
+				*GetSidSubAuthority(tg,
+				             *GetSidSubAuthorityCount(tg) - 1));
+		      debug_printf ("Emulating /etc/group: %s", linebuf);
+		      add_grp_line (linebuf);
+		      group_state = emulated;
+		    }
+		  CloseHandle (ptok);
+		}
+	    }
+	  if (group_state != emulated)
+	    {
+	      strncpy (group_name, "Administrators", sizeof (group_name));
+	      if (!LookupAccountSidA (NULL, well_known_admins_sid, group_name,
+				      &group_name_len, domain_name,
+				      &domain_name_len, &acType))
+		{
+		  strcpy (group_name, "unknown");
+		  debug_printf ("Failed to get local admins group name. %E");
+		}
+	      snprintf (linebuf, sizeof (linebuf), "%s::%u:", group_name,
+			(unsigned) DEFAULT_GID);
+	      debug_printf ("Emulating /etc/group: %s", linebuf);
+	      add_grp_line (linebuf);
+	      group_state = emulated;
 	    }
-	  snprintf (linebuf, sizeof (linebuf), "%s::%u:\n", group_name,
-		    (unsigned) DEFAULT_GID);
-	  add_grp_line (linebuf);
-	  group_state = emulated;
 	}
     }
 
diff --git a/winsup/cygwin/passwd.cc b/winsup/cygwin/passwd.cc
index ac1ecf8f0..b251264b7 100644
--- a/winsup/cygwin/passwd.cc
+++ b/winsup/cygwin/passwd.cc
@@ -160,14 +160,46 @@ read_etc_passwd ()
 	}
       else
 	{
-	  static char linebuf[400];
+	  static char linebuf[1024];
 
-	  debug_printf ("Emulating /etc/passwd");
-	  snprintf (linebuf, sizeof (linebuf), "%s::%u:%u::%s:/bin/sh",
-	  	    cygheap->user.name (), (unsigned) DEFAULT_UID,
-		    (unsigned) DEFAULT_GID, getenv ("HOME") ?: "/");
-	  add_pwd_line (linebuf);
-	  passwd_state = emulated;
+	  if (wincap.has_security ())
+	    {
+	      HANDLE ptok;
+	      cygsid tu, tg;
+	      DWORD siz;
+
+	      if (OpenProcessToken (GetCurrentProcess (), TOKEN_QUERY, &ptok))
+	        {
+		  if (GetTokenInformation (ptok, TokenUser, &tu, sizeof tu,
+		                           &siz)
+		      && GetTokenInformation (ptok, TokenPrimaryGroup, &tg,
+					      sizeof tg, &siz))
+		    {
+		      char strbuf[100];
+		      snprintf (linebuf, sizeof (linebuf),
+				"%s::%u:%u:%s:%s:/bin/sh",
+				cygheap->user.name (),
+				*GetSidSubAuthority(tu,
+				             *GetSidSubAuthorityCount(tu) - 1),
+				*GetSidSubAuthority(tg,
+				             *GetSidSubAuthorityCount(tg) - 1),
+				tu.string (strbuf), getenv ("HOME") ?: "/");
+		      debug_printf ("Emulating /etc/passwd: %s", linebuf);
+		      add_pwd_line (linebuf);
+		      passwd_state = emulated;
+		    }
+		  CloseHandle (ptok);
+	        }
+	    }
+	  if (passwd_state != emulated)
+	    {
+	      snprintf (linebuf, sizeof (linebuf), "%s::%u:%u::%s:/bin/sh",
+			cygheap->user.name (), (unsigned) DEFAULT_UID,
+			(unsigned) DEFAULT_GID, getenv ("HOME") ?: "/");
+	      debug_printf ("Emulating /etc/passwd: %s", linebuf);
+	      add_pwd_line (linebuf);
+	      passwd_state = emulated;
+	    }
 	}
 
     }