Patrik Ek created SSHD-968:
------------------------------
Summary: SshClient times out during keep-alive, when
SSH_MSG_GLOBAL_REQUEST is replies with SSH_MSG_UNSUPPORTED
Key: SSHD-968
URL: https://issues.apache.org/jira/browse/SSHD-968
Project: MINA SSHD
Issue Type: Improvement
Affects Versions: 2.3.0
Environment: Windows 10
Reporter: Patrik Ek
In case SSH_MSG_GLOBAL_REQUEST is not supported by the remote SSH server, the
keep-alive heartbeat times out. The reason for this is SSH_MSG_UNIMPLEMENTED is
only logged in
{color:#172b4d}org.apache.sshd.common.session.helpers{color}.AbstractSession
The method identifying the SSH_MSG_UNIMPLEMENTED is called
AbstractSession.doHandleMessage()
The consequense is that no reply is received and the heartbeat times out
instead of calling AbstractSession.requestFailure(). Which in turn leads to the
session terminates.
According to RFC 4253 sect. 11.4
({color:#004000}https://tools.ietf.org/html/rfc4253#section-11.4{color}) the
SSH_MSG_UNIMPLEMENTED is meant to be ignored, but this makes little sense for a
heartbeat, as even SSH_MSG_UNIMPLEMENTED is good enough to count as a reply for
this. This is for example the case in OpenSSH, where SSH_MSG_UNIMPLEMENTED
replies for heartbeat, does not lead to a termination of the SSH session.
There is a workaround released in 2.1.1, to use ReservedSessionMessagesHandler
for handling replies, but this does not allow access to the method
AbstractSession.requestFailure() (without using reflection so to say). Further,
the heartbeat is ongoing in the background, so there is no good solution to
this problem from outside of the framework.
https://issues.apache.org/jira/browse/SSHD-887?jql=project%20%3D%20SSHD%20AND%20fixVersion%20%3D%202.1.1
Would this be possible to fix? The reason I write it here is because the bug
seems to existing up to some version of libssh, even for the SSHv2 protocol, so
just writing a bug report on the particular server will not solve the problems
for already existing implementations using libssh.
The following config is used,
SshClient client =
SshClient.setUpDefaultClient(){color:#cc7832};{color}{color:#808080}
{color} {color:#172b4d}PropertyResolverUtils.updateProperty(client,
ClientFactoryManager.HEARTBEAT_INTERVAL, 15000);
PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REPLY_WAIT,
30000);
PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REQUEST,
"keepal...@openssh.com");{color}
{color:#cc7832}{color:#172b4d}BR{color}
{color:#172b4d}Patrik{color}
{color}
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