- markus@cvs.openbsd.org 2001/10/07 17:49:40

     [channels.c channels.h]
     avoid possible FD_ISSET overflow for channels established
     during channnel_after_select() (used for dynamic channels).

1 files changed, 28 insertions, 8 deletions

diff --git a/channels.c b/channels.c
index 758ea506d..1ec6074b5 100644
--- a/channels.c
+++ b/channels.c
@@ -39,7 +39,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: channels.c,v 1.136 2001/10/04 15:05:40 markus Exp $");
+RCSID("$OpenBSD: channels.c,v 1.137 2001/10/07 17:49:40 markus Exp $");
 
 #include "ssh.h"
 #include "ssh1.h"
@@ -241,6 +241,7 @@ channel_new(char *ctype, int type, int rfd, int wfd, int efd,
         }
         /* Initialize and return new channel. */
         c = channels[found] = xmalloc(sizeof(Channel));
+        memset(c, 0, sizeof(Channel));
         buffer_init(&c->input);
         buffer_init(&c->output);
         buffer_init(&c->extended);
@@ -974,7 +975,7 @@ channel_pre_dynamic(Channel *c, fd_set * readset, fd_set * writeset)
         int have, ret;
 
         have = buffer_len(&c->input);
-
+        c->delayed = 0;
         debug2("channel %d: pre_dynamic: have %d", c->self, have);
         /* buffer_dump(&c->input); */
         /* check if the fixed size part of the packet is in buffer. */
@@ -1133,11 +1134,18 @@ channel_post_port_listener(Channel *c, fd_set * readset, fd_set * writeset)
                     "to %.100s port %d requested.",
                     c->listening_port, c->path, c->host_port);
 
-                rtype = (c->type == SSH_CHANNEL_RPORT_LISTENER) ?
-                    "forwarded-tcpip" : "direct-tcpip";
-                nextstate = (c->host_port == 0 &&
-                    c->type != SSH_CHANNEL_RPORT_LISTENER) ?
-                    SSH_CHANNEL_DYNAMIC : SSH_CHANNEL_OPENING;
+                if (c->type == SSH_CHANNEL_RPORT_LISTENER) {
+                        nextstate = SSH_CHANNEL_OPENING;
+                        rtype = "forwarded-tcpip";
+                } else {
+                        if (c->host_port == 0) {
+                                nextstate = SSH_CHANNEL_DYNAMIC;
+                                rtype = "direct-tcpip";
+                        } else {
+                                nextstate = SSH_CHANNEL_OPENING;
+                                rtype = "direct-tcpip";
+                        }
+                }
 
                 addrlen = sizeof(addr);
                 newsock = accept(c->sock, &addr, &addrlen);
@@ -1158,8 +1166,16 @@ channel_post_port_listener(Channel *c, fd_set * readset, fd_set * writeset)
                 nc->host_port = c->host_port;
                 strlcpy(nc->path, c->path, sizeof(nc->path));
 
-                if (nextstate != SSH_CHANNEL_DYNAMIC)
+                if (nextstate == SSH_CHANNEL_DYNAMIC) {
+                        /*
+                         * do not call the channel_post handler until
+                         * this flag has been reset by a pre-handler.
+                         * otherwise the FD_ISSET calls might overflow
+                         */
+                        nc->delayed = 1;
+                } else {
                         port_open_helper(nc, rtype);
+                }
         }
 }
 
@@ -1409,6 +1425,8 @@ channel_check_window(Channel *c)
 static void
 channel_post_open_1(Channel *c, fd_set * readset, fd_set * writeset)
 {
+        if (c->delayed)
+                return;
         channel_handle_rfd(c, readset, writeset);
         channel_handle_wfd(c, readset, writeset);
 }
@@ -1416,6 +1434,8 @@ channel_post_open_1(Channel *c, fd_set * readset, fd_set * writeset)
 static void
 channel_post_open_2(Channel *c, fd_set * readset, fd_set * writeset)
 {
+        if (c->delayed)
+                return;
         channel_handle_rfd(c, readset, writeset);
         channel_handle_wfd(c, readset, writeset);
         channel_handle_efd(c, readset, writeset);