cp: make it a bit closer to POSIX, but still refuse to open and

write to dest which is a symlink.

diff --git a/libbb/copy_file.c b/libbb/copy_file.c
index 86449f27c853b0b654939a07d0243479e4ce1db6..3da8a353195e6f812ba9b016a11934350f2f7ccd 100644 (file)
--- a/libbb/copy_file.c
+++ b/libbb/copy_file.c
@@ -141,6 +141,8 @@ int copy_file(const char *source, const char *dest, int flags)
                                bb_error_msg("target '%s' is not a directory", dest);
                                return -1;
                        }
+                       /* race here: user can substitute a symlink between
+                        * this check and actual creation of files inside dest */
                } else {
                        mode_t mode;
                        saved_umask = umask(0);
@@ -247,13 +249,13 @@ int copy_file(const char *source, const char *dest, int flags)
                        return -1;
 
                /* POSIX way is a security problem versus symlink attacks,
-                * we do it only for dest's which are device nodes,
-                * and only for non-recursive, non-interactive cp. NB: it is still racy
-                * for "cp file /home/bad_user/device_node" case
-                * (user can rm device_node and create link to /etc/passwd) */
+                * we do it only for non-symlinks, and only for non-recursive,
+                * non-interactive cp. NB: it is still racy
+                * for "cp file /home/bad_user/file" case
+                * (user can rm file and create a link to /etc/passwd) */
                if (DO_POSIX_CP
                 || (dest_exists && !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
-                    && (S_ISBLK(dest_stat.st_mode) || S_ISCHR(dest_stat.st_mode)))
+                    && !S_ISLNK(dest_stat.st_mode))
                ) {
                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, source_stat.st_mode);
                } else  /* safe way: */