X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fchown.c;h=b851cbc4c0bf13e7e88854bd93fb6ac0675c628e;hb=9faf3d43bdbdab2aa0df10f3470208f260d51dcd;hp=452fdfcac6ef41b488fc25ce25745bb9ebf5d653;hpb=89f2b4892655a929a506eff123c9126a88e2c8eb;p=gnulib.git

diff --git a/lib/chown.c b/lib/chown.c
index 452fdfcac..b851cbc4c 100644
--- a/lib/chown.c
+++ b/lib/chown.c
@@ -1,11 +1,12 @@
 /* provide consistent interface to chown for systems that don't interpret
    an ID of -1 as meaning `don't change the corresponding ID'.
-   Copyright (C) 1997 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   Copyright (C) 1997, 2004-2007, 2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -13,36 +14,47 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* written by Jim Meyering */
 
 #include <config.h>
 
-/* Disable the definition of chown to rpl_chown (from config.h) in this
-   file.  Otherwise, we'd get conflicting prototypes for rpl_chown on
-   most systems.  */
-#undef chown
+/* Specification.  */
+#include <unistd.h>
 
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#if HAVE_UNISTD_H
-# include <unistd.h>
-#endif
+#include <fcntl.h>
+#include <errno.h>
+
+/* Below we refer to the system's chown().  */
+#undef chown
+
+/* The results of open() in this file are not used with fchdir,
+   therefore save some unnecessary work in fchdir.c.  */
+#undef open
+#undef close
 
-/* FIXME: describe.  */
+/* Provide a more-closely POSIX-conforming version of chown on
+   systems with one or both of the following problems:
+   - chown doesn't treat an ID of -1 as meaning
+   `don't change the corresponding ID'.
+   - chown doesn't dereference symlinks.  */
 
 int
 rpl_chown (const char *file, uid_t uid, gid_t gid)
 {
+#if HAVE_CHOWN
+# if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
   if (gid == (gid_t) -1 || uid == (uid_t) -1)
     {
       struct stat file_stats;
 
       /* Stat file to get id(s) that should remain unchanged.  */
       if (stat (file, &file_stats))
-	return 1;
+	return -1;
 
       if (gid == (gid_t) -1)
 	gid = file_stats.st_gid;
@@ -50,6 +62,48 @@ rpl_chown (const char *file, uid_t uid, gid_t gid)
       if (uid == (uid_t) -1)
 	uid = file_stats.st_uid;
     }
+# endif
+
+# if CHOWN_MODIFIES_SYMLINK
+  {
+    /* Handle the case in which the system-supplied chown function
+       does *not* follow symlinks.  Instead, it changes permissions
+       on the symlink itself.  To work around that, we open the
+       file (but this can fail due to lack of read or write permission) and
+       use fchown on the resulting descriptor.  */
+    int open_flags = O_NONBLOCK | O_NOCTTY;
+    int fd = open (file, O_RDONLY | open_flags);
+    if (0 <= fd
+	|| (errno == EACCES
+	    && 0 <= (fd = open (file, O_WRONLY | open_flags))))
+      {
+	int result = fchown (fd, uid, gid);
+	int saved_errno = errno;
+
+	/* POSIX says fchown can fail with errno == EINVAL on sockets,
+	   so fall back on chown in that case.  */
+	struct stat sb;
+	bool fchown_socket_failure =
+	  (result != 0 && saved_errno == EINVAL
+	   && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
+
+	close (fd);
+
+	if (! fchown_socket_failure)
+	  {
+	    errno = saved_errno;
+	    return result;
+	  }
+      }
+    else if (errno != EACCES)
+      return -1;
+  }
+# endif
 
   return chown (file, uid, gid);
+
+#else /* !HAVE_CHOWN */
+  errno = ENOSYS;
+  return -1;
+#endif
 }