New file, mostly from euidaccess.c.

2026-07-26 02:30:35 +02:00 · 2005-11-20 08:51:10 +00:00
parent c0c83656d2
commit e88132fa06
1 changed files with 145 additions and 0 deletions
@@ -0,0 +1,145 @@
+/* euidaccess-stat -- check if effective user id can access lstat'd file
+   This function is probably useful only for choosing whether to issue
+   a prompt in an implementation of POSIX-specified rm.
+
+   Copyright (C) 2005 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.
+
+   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Adapted for use in GNU remove.c by Jim Meyering.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "euidaccess-stat.h"
+
+#include <unistd.h>
+
+#ifndef F_OK
+# define F_OK 0
+# define X_OK 1
+# define W_OK 2
+# define R_OK 4
+#endif
+
+#include "group-member.h"
+#include "stat-macros.h"
+
+/* Return true if the current user has permission of type MODE
+   on the file from which stat buffer *ST was obtained, ignoring
+   ACLs, attributes, `read-only'ness, etc...
+   Otherwise, return false.
+
+   Like the reentrant version of euidaccess, but starting with
+   a stat buffer rather than a file name.  Hence, this function
+   never calls access or accessx, and doesn't take into account
+   whether the file has ACLs or other attributes, or resides on
+   a read-only file system.  */
+
+bool
+euidaccess_stat (struct stat const *st, int mode)
+{
+  uid_t euid;
+  unsigned int granted;
+
+  /* Convert the mode to traditional form, clearing any bogus bits.  */
+  if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
+    mode &= 7;
+  else
+    mode = ((mode & R_OK ? 4 : 0)
+	    + (mode & W_OK ? 2 : 0)
+	    + (mode & X_OK ? 1 : 0));
+
+  if (mode == 0)
+    return true;		/* The file exists.  */
+
+  euid = geteuid ();
+
+  /* The super-user can read and write any file, and execute any file
+     that anyone can execute.  */
+  if (euid == 0 && ((mode & X_OK) == 0
+		    || (st->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
+    return true;
+
+  /* Convert the file's permission bits to traditional form.  */
+  if (   S_IRUSR == (4 << 6)
+      && S_IWUSR == (2 << 6)
+      && S_IXUSR == (1 << 6)
+      && S_IRGRP == (4 << 3)
+      && S_IWGRP == (2 << 3)
+      && S_IXGRP == (1 << 3)
+      && S_IROTH == (4 << 0)
+      && S_IWOTH == (2 << 0)
+      && S_IXOTH == (1 << 0))
+    granted = st->st_mode;
+  else
+    granted = (  (st->st_mode & S_IRUSR ? 4 << 6 : 0)
+	       + (st->st_mode & S_IWUSR ? 2 << 6 : 0)
+	       + (st->st_mode & S_IXUSR ? 1 << 6 : 0)
+	       + (st->st_mode & S_IRGRP ? 4 << 3 : 0)
+	       + (st->st_mode & S_IWGRP ? 2 << 3 : 0)
+	       + (st->st_mode & S_IXGRP ? 1 << 3 : 0)
+	       + (st->st_mode & S_IROTH ? 4 << 0 : 0)
+	       + (st->st_mode & S_IWOTH ? 2 << 0 : 0)
+	       + (st->st_mode & S_IXOTH ? 1 << 0 : 0));
+
+  if (euid == st->st_uid)
+    granted >>= 6;
+  else
+    {
+      gid_t egid = getegid ();
+      if (egid == st->st_gid || group_member (st->st_gid))
+	granted >>= 3;
+    }
+
+  if ((mode & ~granted) == 0)
+    return true;
+
+  return false;
+}
+
+
+#ifdef TEST
+# include <errno.h>
+# include <stdio.h>
+# include <stdlib.h>
+
+# include "error.h"
+# define _(msg) msg
+
+char *program_name;
+
+int
+main (int argc, char **argv)
+{
+  char *file;
+  int mode;
+  bool ok;
+  struct stat st;
+
+  program_name = argv[0];
+  if (argc < 3)
+    abort ();
+  file = argv[1];
+  mode = atoi (argv[2]);
+  if (lstat (file, &st) != 0)
+    error (EXIT_FAILURE, errno, _("cannot stat %s"), file);
+
+  ok = euidaccess_stat (&st, mode);
+  printf ("%s: %s\n", file, ok ? "y" : "n");
+  exit (0);
+}
+#endif