- markus@cvs.openbsd.org 2001/02/28 21:27:48

     [channels.c packet.c packet.h serverloop.c]
     use ignore message to simulate a SSH2_MSG_CHANNEL_DATA message
     use random content in ignore messages.

5 files changed, 29 insertions, 16 deletions

diff --git a/ChangeLog b/ChangeLog
index a2eaf69b..2cdd9997 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -85,6 +85,10 @@
    - markus@cvs.openbsd.org 2001/02/28 21:21:41
      [sshd.c]
      generate a fake session id, too
+   - markus@cvs.openbsd.org 2001/02/28 21:27:48
+     [channels.c packet.c packet.h serverloop.c]
+     use ignore message to simulate a SSH2_MSG_CHANNEL_DATA message
+     use random content in ignore messages.
 
 20010304
  - (bal) Remove make-ssh-known-hosts.1 since it's no longer valid.
@@ -4277,4 +4281,4 @@
  - Wrote replacements for strlcpy and mkdtemp
  - Released 1.0pre1
 
-$Id: ChangeLog,v 1.876 2001/03/05 06:25:23 mouring Exp $
+$Id: ChangeLog,v 1.877 2001/03/05 06:28:06 mouring Exp $
diff --git a/channels.c b/channels.c
index d1c90b4a..defe5ecb 100644
--- a/channels.c
+++ b/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/packet.c b/packet.c
index 26abf0e1..a1a5d8a7 100644
--- a/packet.c
+++ b/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"
@@ -1321,8 +1321,7 @@ 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)
@@ -1350,7 +1349,16 @@ 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/packet.h b/packet.h
index 059bb27a..e5432714 100644
--- a/packet.h
+++ b/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/serverloop.c b/serverloop.c
index 651d3feb..285f314e 100644
--- a/serverloop.c
+++ b/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. */