Add a new sysctl: kern.tty_inq_flush_secure.

When enabled all TTY input queue buffers are zeroed when flushing or
closing the TTY. Because TTY input queues are also used to store filled
in passwords, this may be an interesting switch to enable for security
minded people.

1 files changed, 8 insertions, 14 deletions

diff --git a/sys/kern/tty_inq.c b/sys/kern/tty_inq.c
index 60a13de..0ef4079 100644
--- a/sys/kern/tty_inq.c
+++ b/sys/kern/tty_inq.c
@@ -68,6 +68,9 @@ SYSCTL_ULONG(_kern, OID_AUTO, tty_inq_nfast, CTLFLAG_RD,
 static unsigned long ttyinq_nslow = 0;
 SYSCTL_ULONG(_kern, OID_AUTO, tty_inq_nslow, CTLFLAG_RD,
 	&ttyinq_nslow, 0, "Buffered reads to userspace on input");
+static int ttyinq_flush_secure = 0;
+SYSCTL_INT(_kern, OID_AUTO, tty_inq_flush_secure, CTLFLAG_RW,
+	&ttyinq_flush_secure, 0, "Zero buffers while flushing");
 
 #define TTYINQ_QUOTESIZE	(TTYINQ_DATASIZE / BMSIZE)
 #define BMSIZE			32
@@ -376,28 +379,19 @@ ttyinq_findchar(struct ttyinq *ti, const char *breakc, size_t maxlen,
 void
 ttyinq_flush(struct ttyinq *ti)
 {
+	struct ttyinq_block *tib = ti->ti_lastblock;
 
 	ti->ti_begin = 0;
 	ti->ti_linestart = 0;
 	ti->ti_reprint = 0;
 	ti->ti_end = 0;
-}
-
-#if 0
-void
-ttyinq_flush_safe(struct ttyinq *ti)
-{
-	struct ttyinq_block *tib;
-
-	ttyinq_flush(ti);
 
-	/* Zero all data in the input queue to make it more safe */
-	TAILQ_FOREACH(tib, &ti->ti_list, tib_list) {
-		bzero(&tib->tib_quotes, sizeof tib->tib_quotes);
-		bzero(&tib->tib_data, sizeof tib->tib_data);
+	/* Zero all data in the input queue to get rid of passwords. */
+	if (ttyinq_flush_secure) {
+		for (tib = ti->ti_firstblock; tib != NULL; tib = tib->tib_next)
+			bzero(&tib->tib_data, sizeof tib->tib_data);
 	}
 }
-#endif
 
 int
 ttyinq_peekchar(struct ttyinq *ti, char *c, int *quote)