cp: fix -i for POSIX mode. Closes 9106

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/libbb/copy_file.c b/libbb/copy_file.c
index 7801b58c7..23c0f8320 100644
--- a/libbb/copy_file.c
+++ b/libbb/copy_file.c
@@ -296,11 +296,16 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
                 if (!S_ISREG(source_stat.st_mode))
                         new_mode = 0666;
 
-                // POSIX way is a security problem versus (sym)link attacks
-                if (!ENABLE_FEATURE_NON_POSIX_CP) {
-                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
-                } else { /* safe way: */
+                if (ENABLE_FEATURE_NON_POSIX_CP || (flags & FILEUTILS_INTERACTIVE)) {
+                        /*
+                         * O_CREAT|O_EXCL: require that file did not exist before creation
+                         */
                         dst_fd = open(dest, O_WRONLY|O_CREAT|O_EXCL, new_mode);
+                } else { /* POSIX, and not "cp -i" */
+                        /*
+                         * O_CREAT|O_TRUNC: create, or truncate (security problem versus (sym)link attacks)
+                         */
+                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
                 }
                 if (dst_fd == -1) {
                         ovr = ask_and_unlink(dest, flags);