1 files changed, 97 insertions, 0 deletions
diff --git a/lib/unlink.c b/lib/unlink.c
new file mode 100644
index 0000000..b7daa7c
--- /dev/null
+++ b/lib/unlink.c
@@ -0,0 +1,97 @@
+/* Work around unlink bugs.
+
+   Copyright (C) 2009-2020 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 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
+   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, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include "dosname.h"
+
+#undef unlink
+
+/* Remove file NAME.
+   Return 0 if successful, -1 if not.  */
+
+int
+rpl_unlink (char const *name)
+{
+  /* Work around Solaris 9 bug where unlink("file/") succeeds.  */
+  size_t len = strlen (name);
+  int result = 0;
+  if (len && ISSLASH (name[len - 1]))
+    {
+      /* We can't unlink(2) something if it doesn't exist.  If it does
+         exist, then it resolved to a directory, due to the trailing
+         slash, and POSIX requires that the unlink attempt to remove
+         that directory (which would leave the symlink dangling).
+         Unfortunately, Solaris 9 is one of the platforms where the
+         root user can unlink directories, and we don't want to
+         cripple this behavior on real directories, even if it is
+         seldom needed (at any rate, it's nicer to let coreutils'
+         unlink(1) give the correct errno for non-root users).  But we
+         don't know whether name was an actual directory, or a symlink
+         to a directory; and due to the bug of ignoring trailing
+         slash, Solaris 9 would end up successfully unlinking the
+         symlink instead of the directory.  Technically, we could use
+         realpath to find the canonical directory name to attempt
+         deletion on.  But that is a lot of work for a corner case; so
+         we instead just use an lstat on the shortened name, and
+         reject symlinks with trailing slashes.  The root user of
+         unlink(1) will just have to live with the rule that they
+         can't delete a directory via a symlink.  */
+      struct stat st;
+      result = lstat (name, &st);
+      if (result == 0)
+        {
+          /* Trailing NUL will overwrite the trailing slash.  */
+          char *short_name = malloc (len);
+          if (!short_name)
+            {
+              errno = EPERM;
+              return -1;
+            }
+          memcpy (short_name, name, len);
+          while (len && ISSLASH (short_name[len - 1]))
+            short_name[--len] = '\0';
+          if (len && (lstat (short_name, &st) || S_ISLNK (st.st_mode)))
+            {
+              free (short_name);
+              errno = EPERM;
+              return -1;
+            }
+          free (short_name);
+        }
+    }
+  if (!result)
+    {
+#if UNLINK_PARENT_BUG
+      if (len >= 2 && name[len - 1] == '.' && name[len - 2] == '.'
+          && (len == 2 || ISSLASH (name[len - 3])))
+        {
+          errno = EISDIR; /* could also use EPERM */
+          return -1;
+        }
+#endif
+      result = unlink (name);
+    }
+  return result;
+}