Work around a bug in some clients by never returning raw directory

contents in reply to a RETR command.  Such clients consider RETR
as a way to tell a file from a directory.  Mozilla is an example.

PR:		bin/62232
Submitted by:	Bob Finch <bob+freebsd <at> nas <dot> com>
MFC after:	1 week

1 files changed, 8 insertions, 1 deletions

diff --git a/libexec/ftpd/ftpd.c b/libexec/ftpd/ftpd.c
index 68899dd..27182de 100644
--- a/libexec/ftpd/ftpd.c
+++ b/libexec/ftpd/ftpd.c
@@ -1653,7 +1653,14 @@ retrieve(char *cmd, char *name)
 			goto done;
 		}
 		if (!S_ISREG(st.st_mode)) {
-			if (guest) {
+			/*
+			 * Never sending a raw directory is a workaround
+			 * for buggy clients that will attempt to RETR
+			 * a directory before listing it, e.g., Mozilla.
+			 * Preventing a guest from getting irregular files
+			 * is a simple security measure.
+			 */
+			if (S_ISDIR(st.st_mode) || guest) {
 				reply(550, "%s: not a plain file.", name);
 				goto done;
 			}