Thomas Wolf created SSHD-1158:
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Summary: Channel closed by peer: extra SSH_MSG_CHANNEL_EOF sent
Key: SSHD-1158
URL: https://issues.apache.org/jira/browse/SSHD-1158
Project: MINA SSHD
Issue Type: Bug
Affects Versions: 2.6.0, 2.7.0
Reporter: Thomas Wolf
I observe the following:
{code:java}
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
ChannelExec:528 - handleClose(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])
SSH_MSG_CHANNEL_CLOSE
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
ChannelExec:533 - handleClose(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22]) prevent
sending EOF
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
ChannelExec:107 - close(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22]) Closing
gracefully
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
ChannelExec:666 - close(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22]) prevent
sending EOF
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3 Window:356
- Closing Window[client/local](ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3 Window:356
- Closing Window[client/remote](ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
ChannelExec:901 - sendEof(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])
SSH_MSG_CHANNEL_EOF (state=Graceful)
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
JGitClientSession:1215 -
encode(JGitClientSession[g...@bitbucket.org/104.192.141.1:22]) packet #14
sending command=96[SSH_MSG_CHANNEL_EOF] len=5
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
Nio2Session:171 - writeBuffer(Nio2Session[local=/192.168.2.83:58913,
remote=bitbucket.org/104.192.141.1:22]) writing 68 bytes
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
AbstractChannel$GracefulChannelCloseable:594 - close(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])[immediately=false]
processing
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
AbstractChannel$GracefulChannelCloseable:602 - close(ChannelExec[id=0,
recipient=0]-JGitClientSession[g...@bitbucket.org/104.192.141.1:22])[immediately=false]
send SSH_MSG_CHANNEL_CLOSE
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
JGitClientSession:1215 -
encode(JGitClientSession[g...@bitbucket.org/104.192.141.1:22]) packet #15
sending command=97[SSH_MSG_CHANNEL_CLOSE] len=5
2021-04-30 17:03:39 DEBUG sshd-JGitSshClient[7c440ee8]-nio2-thread-3
Nio2Session:171 - writeBuffer(Nio2Session[local=/192.168.2.83:58913,
remote=bitbucket.org/104.192.141.1:22]) writing 68 bytes
{code}
* Client receives a SSH_MSG_CHANNEL_CLOSE from the server
* Client logs (twice) is wouldn't send an EOF
* Client sends SSH_MSG_CHANNEL_EOF all the same
* Client sends SSH_MSG_CHANNEL_CLOSE
In my reading of [RFC 4254, section
5.3|https://tools.ietf.org/html/rfc4254#section-5.3], this is wrong; the RFC
says:
{quote}Upon receiving this message, a party *MUST* send back an
SSH_MSG_CHANNEL_CLOSE unless it has already sent this message for the channel.
[...] A party MAY send SSH_MSG_CHANNEL_CLOSE without having sent or received
SSH_MSG_CHANNEL_EOF.
{quote}
I take this to mean that on reception of a CLOSE one needs to reply CLOSE, not
EOF followed by CLOSE.
IMO {{AbstractChannel.handleClose()}} should not call {{isEofSent()}} but use
{{eofSent.getAndSet(true)}} instead to really prevent sending the EOF.
That code got changed in SSHD-836 (commit
[bba23bf70|https://github.com/apache/mina-sshd/commit/bba23bf70bcd7e4d5a972806a9df62669e7cda81#diff-e9d125fde1660adf395b423e4e0831b4ad9092ddf73fe8285a9706fa4b74d030R540]).
What was the reason for that? [~gnodet], do you remember?
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