diff --git a/ChangeLog b/ChangeLog
index eceda670e..3504e5674 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -25,6 +25,9 @@
      [auth.c]
      Populate host for log message for logins denied by AllowUsers and
      DenyUsers (bz #999); ok markus@
+   - markus@cvs.openbsd.org 2005/03/14 11:46:56
+     [buffer.c buffer.h channels.c]
+     limit input buffer size for channels; bugzilla #896; with and ok dtucker@
 
 20050313
  - (dtucker) [contrib/cygwin/ssh-host-config] Makes the query for the
@@ -2359,4 +2362,4 @@
    - (djm) Trim deprecated options from INSTALL. Mention UsePAM
    - (djm) Fix quote handling in sftp; Patch from admorten AT umich.edu
 
-$Id: ChangeLog,v 1.3717 2005/03/14 12:17:27 dtucker Exp $
+$Id: ChangeLog,v 1.3718 2005/03/14 12:22:25 dtucker Exp $
diff --git a/buffer.c b/buffer.c
index 1a25004ba..487e08105 100644
--- a/buffer.c
+++ b/buffer.c
@@ -12,7 +12,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: buffer.c,v 1.22 2004/10/29 23:56:17 djm Exp $");
+RCSID("$OpenBSD: buffer.c,v 1.23 2005/03/14 11:46:56 markus Exp $");
 
 #include "xmalloc.h"
 #include "buffer.h"
@@ -78,7 +78,7 @@ buffer_append_space(Buffer *buffer, u_int len)
 	u_int newlen;
 	void *p;
 
-	if (len > 0x100000)
+	if (len > BUFFER_MAX_CHUNK)
 		fatal("buffer_append_space: len %u not supported", len);
 
 	/* If the buffer is empty, start using it from the beginning. */
@@ -97,7 +97,7 @@ restart:
 	 * If the buffer is quite empty, but all data is at the end, move the
 	 * data to the beginning and retry.
 	 */
-	if (buffer->offset > buffer->alloc / 2) {
+	if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
 		memmove(buffer->buf, buffer->buf + buffer->offset,
 			buffer->end - buffer->offset);
 		buffer->end -= buffer->offset;
@@ -107,7 +107,7 @@ restart:
 	/* Increase the size of the buffer and retry. */
 
 	newlen = buffer->alloc + len + 32768;
-	if (newlen > 0xa00000)
+	if (newlen > BUFFER_MAX_LEN)
 		fatal("buffer_append_space: alloc %u not supported",
 		    newlen);
 	buffer->buf = xrealloc(buffer->buf, newlen);
diff --git a/buffer.h b/buffer.h
index 9c09d4f43..2b20eed52 100644
--- a/buffer.h
+++ b/buffer.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: buffer.h,v 1.12 2004/10/29 23:56:17 djm Exp $	*/
+/*	$OpenBSD: buffer.h,v 1.13 2005/03/14 11:46:56 markus Exp $	*/
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -23,6 +23,9 @@ typedef struct {
 	u_int	 end;		/* Offset of last byte containing data. */
 }       Buffer;
 
+#define	BUFFER_MAX_CHUNK	0x100000
+#define	BUFFER_MAX_LEN		0xa00000
+
 void	 buffer_init(Buffer *);
 void	 buffer_clear(Buffer *);
 void	 buffer_free(Buffer *);
diff --git a/channels.c b/channels.c
index 4bd9af8e6..3f6db60c6 100644
--- a/channels.c
+++ b/channels.c
@@ -39,7 +39,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: channels.c,v 1.213 2005/03/10 22:01:05 deraadt Exp $");
+RCSID("$OpenBSD: channels.c,v 1.214 2005/03/14 11:46:56 markus Exp $");
 
 #include "ssh.h"
 #include "ssh1.h"
@@ -58,6 +58,8 @@ RCSID("$OpenBSD: channels.c,v 1.213 2005/03/10 22:01:05 deraadt Exp $");
 
 /* -- channel core */
 
+#define CHAN_RBUF	16*1024
+
 /*
  * Pointer to an array containing all allocated channels.  The array is
  * dynamically extended as needed.
@@ -712,6 +714,9 @@ channel_pre_open(Channel *c, fd_set * readset, fd_set * writeset)
 {
 	u_int limit = compat20 ? c->remote_window : packet_get_maxsize();
 
+	/* check buffer limits */
+	limit = MIN(limit, (BUFFER_MAX_LEN - BUFFER_MAX_CHUNK - CHAN_RBUF));
+
 	if (c->istate == CHAN_INPUT_OPEN &&
 	    limit > 0 &&
 	    buffer_len(&c->input) < limit)
@@ -1360,7 +1365,7 @@ channel_post_connecting(Channel *c, fd_set * readset, fd_set * writeset)
 static int
 channel_handle_rfd(Channel *c, fd_set * readset, fd_set * writeset)
 {
-	char buf[16*1024];
+	char buf[CHAN_RBUF];
 	int len;
 
 	if (c->rfd != -1 &&
@@ -1454,7 +1459,7 @@ channel_handle_wfd(Channel *c, fd_set * readset, fd_set * writeset)
 static int
 channel_handle_efd(Channel *c, fd_set * readset, fd_set * writeset)
 {
-	char buf[16*1024];
+	char buf[CHAN_RBUF];
 	int len;
 
 /** XXX handle drain efd, too */