commit fb432f3f783bdbfdcb5b99a2cdb8e10ef8f6ae3f
author Salvador Fandino <sfandino-/E1597aS9LQAvxtiuMwx3w@public.gmane.org> Wed Aug 26 14:21:44 2015 +0200
committer Daniel Stenberg <daniel@haxx.se> Tue Sep 29 09:48:36 2015 +0200
tree 9b05aa0d58e2a317029894c4cfc51586ca71d02e
parent fc4a969a0512e226de9b821496d20b9ddf53b741

channel: Detect bad usage of libssh2_channel_process_startup

A common novice programmer error (at least among those using the
wrapping Perl module Net::SSH2), is to try to reuse channels.

This patchs detects that incorrect usage and fails with a
LIBSSH2_ERROR_BAD_USE error instead of hanging.

Signed-off-by: Salvador Fandino <sfandino-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>

src/channel.c

diff --git a/src/channel.c b/src/channel.c
index cb0d818..32d914d 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -1252,6 +1252,11 @@
         { SSH_MSG_CHANNEL_SUCCESS, SSH_MSG_CHANNEL_FAILURE, 0 };
     int rc;
 
+    if (channel->process_state == libssh2_NB_state_end) {
+        return _libssh2_error(session, LIBSSH2_ERROR_BAD_USE,
+                              "Channel can not be reused");
+    }
+
     if (channel->process_state == libssh2_NB_state_idle) {
         /* 10 = packet_type(1) + channel(4) + request_len(4) + want_reply(1) */
         channel->process_packet_len = request_len + 10;
@@ -1298,7 +1303,7 @@
         else if (rc) {
             LIBSSH2_FREE(session, channel->process_packet);
             channel->process_packet = NULL;
-            channel->process_state = libssh2_NB_state_idle;
+            channel->process_state = libssh2_NB_state_end;
             return _libssh2_error(session, rc,
                                   "Unable to send channel request");
         }
@@ -1320,14 +1325,14 @@
         if (rc == LIBSSH2_ERROR_EAGAIN) {
             return rc;
         } else if (rc) {
-            channel->process_state = libssh2_NB_state_idle;
+            channel->process_state = libssh2_NB_state_end;
             return _libssh2_error(session, rc,
                                   "Failed waiting for channel success");
         }
 
         code = data[0];
         LIBSSH2_FREE(session, data);
-        channel->process_state = libssh2_NB_state_idle;
+        channel->process_state = libssh2_NB_state_end;
 
         if (code == SSH_MSG_CHANNEL_SUCCESS)
             return 0;

src/libssh2_priv.h

diff --git a/src/libssh2_priv.h b/src/libssh2_priv.h
index 0ef6e1a..78d4ced 100644
--- a/src/libssh2_priv.h
+++ b/src/libssh2_priv.h
@@ -216,7 +216,8 @@
     libssh2_NB_state_jump2,
     libssh2_NB_state_jump3,
     libssh2_NB_state_jump4,
-    libssh2_NB_state_jump5
+    libssh2_NB_state_jump5,
+    libssh2_NB_state_end
 } libssh2_nonblocking_states;
 
 typedef struct packet_require_state_t