util-vserver-0.30.208

[util-vserver.git] / lib_internal / unify-unify.c

diff --git a/lib_internal/unify-unify.c b/lib_internal/unify-unify.c
new file mode 100644 (file)
index 0000000..e17b2fb
--- /dev/null
+++ b/lib_internal/unify-unify.c
@@ -0,0 +1,121 @@
+// $Id: unify-unify.c,v 1.9 2005/03/24 00:12:23 ensc Exp $    --*- c -*--
+
+// Copyright (C) 2004 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
+//  
+// 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; version 2 of the License.
+//  
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// 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.
+
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include "unify.h"
+#include "vserver.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+bool
+Unify_unify(char const *src, struct stat const UNUSED *src_stat,
+           char const *dst, bool ignore_zero)
+{
+  size_t       l = strlen(dst);
+  char         tmpfile[l + sizeof(";XXXXXX")];
+  int          fd;
+  bool         res = false;
+  struct stat  st;
+  bool         lstat_succeeded;
+  sigset_t     mask_new, mask_old;
+  int          old_errno;
+
+  // at first, set the ILI flags on 'src'
+  if (vc_set_iattr(src,
+                  0,
+                  VC_IATTR_IUNLINK|VC_IATTR_IMMUTABLE,
+                  VC_IATTR_IUNLINK|VC_IATTR_IMMUTABLE)==-1) {
+    perror("vc_set_iattr()");
+    return false;
+  }
+
+  lstat_succeeded = lstat(dst, &st)==0;
+
+  sigfillset(&mask_new);
+  if (sigprocmask(SIG_SETMASK, &mask_new, &mask_old)==-1) {
+    perror("sigprocmask()");
+    return false;
+  }
+    
+  
+  // check if 'dst' already exists
+  // when ignore_zero is true, do not make backups of empty destinations
+  if (lstat_succeeded && (st.st_size>0 || !ignore_zero)) {
+      // now, create a temporary filename
+    memcpy(tmpfile,   dst, l);
+    memcpy(tmpfile+l, ";XXXXXX", 8);
+    fd = mkstemp(tmpfile);
+    close(fd);
+
+    if (fd==-1) {
+      perror("mkstemp()");
+      tmpfile[0] = '\0';
+      goto err;
+    }
+
+      // and rename the old file to this name
+
+      // NOTE: this rename() is race-free; when an attacker makes 'tmpfile' a
+      // directory, the operation would fail; when making it a symlink to a file
+      // or directory, the symlink but not the file/directory would be overridden
+    if (rename(dst, tmpfile)==-1) {
+      perror("rename()");
+      goto err;
+    }
+  }
+  else {
+    if (lstat_succeeded) unlink(dst);  
+    tmpfile[0] = '\0';
+  }
+
+  // now, link the src-file to dst
+  if (link(src, dst)==-1) {
+    perror("link()");
+
+    unlink(dst);
+    if (tmpfile[0]!='\0' &&
+       rename(tmpfile, dst)==-1) {
+      perror("FATAL error in rename()");
+      _exit(1);
+    }
+    goto err;
+  }
+
+  res = true;
+
+  err:
+  old_errno = errno;
+
+  if (tmpfile[0]!='\0')
+    unlink(tmpfile);
+
+  if (sigprocmask(SIG_SETMASK, &mask_old, 0)==-1)
+    perror("sigprocmask()");
+
+  errno     = old_errno;
+  return res;
+}