From 5fa67fe940e0ff8de826d049aaa127a059b31782 Mon Sep 17 00:00:00 2001
From: Markus Friedl <markus@cvs.openbsd.org>
Date: Wed, 28 Feb 2001 21:27:49 +0000
Subject: use ignore message to simulate a SSH2_MSG_CHANNEL_DATA message use
 random content in ignore messages.

---
 usr.bin/ssh/channels.c   | 12 ++++++------
 usr.bin/ssh/packet.c     | 16 ++++++++++++----
 usr.bin/ssh/packet.h     |  5 ++++-
 usr.bin/ssh/serverloop.c |  6 ++----
 4 files changed, 24 insertions(+), 15 deletions(-)

(limited to 'usr.bin')

diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c
index d0ba993af68..cb1e3d8334d 100644
--- a/usr.bin/ssh/channels.c
+++ b/usr.bin/ssh/channels.c
@@ -40,7 +40,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: channels.c,v 1.94 2001/02/28 12:55:07 markus Exp $");
+RCSID("$OpenBSD: channels.c,v 1.95 2001/02/28 21:27:48 markus Exp $");
 
 #include <openssl/rsa.h>
 #include <openssl/dsa.h>
@@ -768,6 +768,7 @@ channel_handle_rfd(Channel *c, fd_set * readset, fd_set * writeset)
 int
 channel_handle_wfd(Channel *c, fd_set * readset, fd_set * writeset)
 {
+	struct termios tio;
 	int len;
 
 	/* Send buffered output data to the socket. */
@@ -789,16 +790,15 @@ channel_handle_wfd(Channel *c, fd_set * readset, fd_set * writeset)
 			return -1;
 		}
 		if (compat20 && c->isatty) {
-			struct termios tio;
 			if (tcgetattr(c->wfd, &tio) == 0 &&
 			    !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 				/*
 				 * Simulate echo to reduce the impact of
-				 * traffic analysis.
+				 * traffic analysis. We need too match the
+				 * size of a SSH2_MSG_CHANNEL_DATA message
+				 * (4 byte channel id + data)
 				 */
-				packet_start(SSH2_MSG_IGNORE);
-				memset(buffer_ptr(&c->output), 0, len);
-				packet_put_string(buffer_ptr(&c->output), len);
+				packet_send_ignore(4 + len);
 				packet_send();
 			}
 		}
diff --git a/usr.bin/ssh/packet.c b/usr.bin/ssh/packet.c
index c47f950a3be..67bbd83323f 100644
--- a/usr.bin/ssh/packet.c
+++ b/usr.bin/ssh/packet.c
@@ -37,7 +37,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: packet.c,v 1.53 2001/02/28 09:57:06 markus Exp $");
+RCSID("$OpenBSD: packet.c,v 1.54 2001/02/28 21:27:47 markus Exp $");
 
 #include "xmalloc.h"
 #include "buffer.h"
@@ -1315,8 +1315,7 @@ packet_set_maxsize(int s)
 void
 packet_inject_ignore(int sumlen)
 {
-	u_int32_t rand = 0;
-	int i, blocksize, padlen, have, need, nb, mini, nbytes;
+	int blocksize, padlen, have, need, nb, mini, nbytes;
 	Enc *enc = NULL;
 
 	if (use_ssh2_packet_format == 0)
@@ -1344,7 +1343,16 @@ packet_inject_ignore(int sumlen)
 
 	/* enqueue current message and append a ignore message */
 	packet_send();
-	packet_start(SSH2_MSG_IGNORE);
+	packet_send_ignore(nbytes);
+}
+
+void
+packet_send_ignore(int nbytes)
+{
+	u_int32_t rand = 0;
+	int i;
+
+	packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
 	packet_put_int(nbytes);
 	for(i = 0; i < nbytes; i++) {
 		if (i % 4 == 0)
diff --git a/usr.bin/ssh/packet.h b/usr.bin/ssh/packet.h
index 059bb27a0fb..e5432714e90 100644
--- a/usr.bin/ssh/packet.h
+++ b/usr.bin/ssh/packet.h
@@ -11,7 +11,7 @@
  * called by a name other than "ssh" or "Secure Shell".
  */
 
-/* RCSID("$OpenBSD: packet.h,v 1.20 2001/02/28 09:57:07 markus Exp $"); */
+/* RCSID("$OpenBSD: packet.h,v 1.21 2001/02/28 21:27:47 markus Exp $"); */
 
 #ifndef PACKET_H
 #define PACKET_H
@@ -215,6 +215,9 @@ void	packet_set_ssh2_format(void);
 int	packet_remaining(void);
 
 /* append an ignore message */
+void	packet_send_ignore(int nbytes);
+
+/* add an ignore message and make sure size (current+ignore) = n*sumlen */
 void	packet_inject_ignore(int sumlen);
 
 #endif				/* PACKET_H */
diff --git a/usr.bin/ssh/serverloop.c b/usr.bin/ssh/serverloop.c
index a89627bd570..8abefe2d880 100644
--- a/usr.bin/ssh/serverloop.c
+++ b/usr.bin/ssh/serverloop.c
@@ -35,7 +35,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: serverloop.c,v 1.51 2001/02/23 15:34:53 markus Exp $");
+RCSID("$OpenBSD: serverloop.c,v 1.52 2001/02/28 21:27:48 markus Exp $");
 
 #include "xmalloc.h"
 #include "packet.h"
@@ -345,9 +345,7 @@ process_output(fd_set * writeset)
 				 * Simulate echo to reduce the impact of
 				 * traffic analysis
 				 */
-				packet_start(SSH_MSG_IGNORE);
-				memset(buffer_ptr(&stdin_buffer), 0, len);
-				packet_put_string(buffer_ptr(&stdin_buffer), len);
+				packet_send_ignore(len);
 				packet_send();
 			}
 			/* Consume the data from the buffer. */
-- 
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