exec after seteuid

[Pierre A. Humblet]

At 10:04 PM 6/7/2003 +0200, Corinna Vinschen wrote:
>I just had a look into the current login.c implementation on NetBSD.
>It is using setuid/setgid.  Actually it's using setusercontext(3)
>but with all options set which implies setuid/setgid.  Yes, using
>only seteuid/setegid in login has to be considered an error which
>just didn't matter so far.

Corinna, 

here is the patch.

It seems to work fine but it requires login.exe changes. It's
not just a question of security. ash does not setuid, while bash 
setuid(getuid()), i.e. just the opposite of what we need.

While I was looking at the most recent login.c I saw that you have
added a seteuid (priv_uid). Ideally, shouldn't it still be effective 
while calling dolastlog()? It's weird that the Berkeley code didn't do
that. There is also the issue raised by Takashi Yano on the list.

I have thrown in the little exceptions.cc quoting patch.
 
2003-06-09  Pierre Humblet  <pierre.humblet@ieee.org>

	* spawn.cc (spawn_guts): Call CreateProcess while impersonated, 
	when the real {u,g}ids and the groups are original.
	Move RevertToSelf and ImpersonateLoggedOnUser to the main line.
	* uinfo.cc (uinfo_init): Reorganize. If CreateProcess was called 
	while impersonated, preserve the uids and gids and call
 	ImpersonateLoggedOnUser. Preserve the uids and gids on Win9X.

	* exceptions.cc (error_start_init): Quote the pgm in the command.
-------------- next part --------------
Index: spawn.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/spawn.cc,v
retrieving revision 1.122
diff -u -p -r1.122 spawn.cc
--- spawn.cc	3 Jun 2003 02:32:49 -0000	1.122
+++ spawn.cc	8 Jun 2003 15:59:10 -0000
@@ -622,7 +622,13 @@ spawn_guts (const char * prog_arg, const
   cygbench ("spawn-guts");

   cygheap->fdtab.set_file_pointers_for_exec ();
-  if (!cygheap->user.issetuid ())
+  RevertToSelf ();
+  /* FIXME. If ruid != euid and ruid != orig_uid we currently give
+     up on ruid. The new process will have ruid = euid */
+  if (!cygheap->user.issetuid ()
+      || (cygheap->user.orig_uid == cygheap->user.real_uid
+	  && cygheap->user.orig_gid == cygheap->user.real_gid
+	  && !cygheap->user.groups.issetgroups ()))
     {
       PSECURITY_ATTRIBUTES sec_attribs = sec_user_nih (sa_buf);
       ciresrv.moreinfo->envp = build_env (envp, envblock, ciresrv.moreinfo->envc,
@@ -646,11 +652,8 @@ spawn_guts (const char * prog_arg, const
       /* Set security attributes with sid */
       PSECURITY_ATTRIBUTES sec_attribs = sec_user_nih (sa_buf, sid);

-      RevertToSelf ();
-
       /* Load users registry hive. */
       load_registry_hive (sid);
-
       /* allow the child to interact with our window station/desktop */
       HANDLE hwst, hdsk;
       SECURITY_INFORMATION dsi = DACL_SECURITY_INFORMATION;
@@ -682,11 +685,11 @@ spawn_guts (const char * prog_arg, const
 		       0,		/* use current drive/directory */
 		       &si,
 		       &pi);
-      /* Restore impersonation. In case of _P_OVERLAY this isn't
-	 allowed since it would overwrite child data. */
-      if (mode != _P_OVERLAY)
-	ImpersonateLoggedOnUser (cygheap->user.token);
     }
+  /* Restore impersonation. In case of _P_OVERLAY this isn't
+     allowed since it would overwrite child data. */
+  if (mode != _P_OVERLAY && cygheap->user.issetuid ())
+    ImpersonateLoggedOnUser (cygheap->user.token);

   MALLOC_CHECK;
   if (envblock)
Index: uinfo.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/uinfo.cc,v
retrieving revision 1.112
diff -u -p -r1.112 uinfo.cc
--- uinfo.cc	27 Feb 2003 17:41:15 -0000	1.112
+++ uinfo.cc	8 Jun 2003 16:02:23 -0000
@@ -103,18 +103,33 @@ internal_getlogin (cygheap_user &user)
 void
 uinfo_init ()
 {
-  if (!child_proc_info || cygheap->user.token != INVALID_HANDLE_VALUE)
+  if (child_proc_info && cygheap->user.token == INVALID_HANDLE_VALUE)
+    return;
+
+  if (!child_proc_info)
+    internal_getlogin (cygheap->user); /* Set the cygheap->user. */
+  else if (!cygheap->user.issetuid ())
     {
-      if (!child_proc_info)
-	internal_getlogin (cygheap->user); /* Set the cygheap->user. */
-      else
-	CloseHandle (cygheap->user.token);
-      cygheap->user.set_orig_sid ();	/* Update the original sid */
-      cygheap->user.token = INVALID_HANDLE_VALUE; /* No token present */
+      CloseHandle (cygheap->user.token);
+      cygheap->user.token = INVALID_HANDLE_VALUE;
+      return;
     }
-  /* Real and effective uid/gid are identical on process start up. */
+  /* Conditions must match those in spawn */
+  else if (cygheap->user.orig_uid == cygheap->user.real_uid
+	   && cygheap->user.orig_gid == cygheap->user.real_gid
+	   && !cygheap->user.groups.issetgroups ())
+    {
+      if (!ImpersonateLoggedOnUser (cygheap->user.token))
+	system_printf ("ImpersonateLoggedOnUser: %E");
+      return;
+    }
+  else
+    CloseHandle (cygheap->user.token);
+
   cygheap->user.orig_uid = cygheap->user.real_uid = myself->uid;
   cygheap->user.orig_gid = cygheap->user.real_gid = myself->gid;
+  cygheap->user.set_orig_sid ();	/* Update the original sid */
+  cygheap->user.token = INVALID_HANDLE_VALUE; /* No token present */
 }

 extern "C" char *
Index: exceptions.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/exceptions.cc,v
retrieving revision 1.147
diff -u -p -r1.147 exceptions.cc
--- exceptions.cc	30 May 2003 15:01:33 -0000	1.147
+++ exceptions.cc	8 Jun 2003 20:47:20 -0000
@@ -154,7 +154,7 @@ error_start_init (const char *buf)
   for (char *p = strchr (pgm, '\\'); p; p = strchr (p, '\\'))
     *p = '/';

-  __small_sprintf (debugger_command, "%s %s", buf, pgm);
+  __small_sprintf (debugger_command, "%s \"%s\"", buf, pgm);
 }

 static void