Low Description
Summary
"BufferException: Underflow" warning is frequently logged out of SSHD server in Bamboo:
Steps to Reproduce
At this stage the cause and steps to reproduce this issue are unknown.
Excepted Results
Exception is well-handled.
Actual Results
Under certain circumstances the following errors are found in atlassian-bamboo.log:
atlassian-bamboo.log
2016-06-01 17:25:01,742 WARN [sshd-SshServer[491791c4]-nio2-thread-4] [ServerSessionImpl] exceptionCaught(ServerSessionImpl[72c0dd86-6efb-4b44-b39a-e05979b1b8f1@/127.0.0.1:49136])[state=Opened] BufferException: Underflow
TRACE log:
atlassian-bamboo.log
2016-06-01 13:08:17,433 TRACE [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] decode(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543]) packet #11 [chunk #1](5/5) 61 00 00 00 00 2016-06-01 13:08:17,434 TRACE [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] doHandleMessage(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543]) process SSH_MSG_CHANNEL_CLOSE 2016-06-01 13:08:17,434 TRACE [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] decode(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543]) packet #12 [chunk #1](29/29) 01 00 00 00 0b 00 00 00 14 64 69 73 63 6f 6e 6e 65 63 74 65 64 20 62 79 20 75 73 65 72 2016-06-01 13:08:17,434 TRACE [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] doHandleMessage(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543]) process SSH_MSG_DISCONNECT 2016-06-01 13:08:17,434 WARN [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] exceptionCaught(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543])[state=Opened] BufferException: Underflow 2016-06-01 13:08:17,434 DEBUG [sshd-SshServer[7a2cdaa7]-nio2-thread-7] [ServerSessionImpl] exceptionCaught(ServerSessionImpl[a55d4e4f-46a4-4da2-b33e-5737fb3e399e@/127.0.0.1:45543])[state=Opened] details org.apache.sshd.common.util.buffer.BufferException: Underflow at org.apache.sshd.common.util.buffer.Buffer.ensureAvailable(Buffer.java:411) at org.apache.sshd.common.util.buffer.Buffer.getUInt(Buffer.java:155) at org.apache.sshd.common.util.buffer.Buffer.getInt(Buffer.java:150) at org.apache.sshd.common.util.buffer.ByteArrayBuffer.getString(ByteArrayBuffer.java:160) at org.apache.sshd.common.util.buffer.Buffer.getString(Buffer.java:180) at org.apache.sshd.common.session.helpers.AbstractSession.handleDisconnect(AbstractSession.java:641) at org.apache.sshd.common.session.helpers.AbstractSession.doHandleMessage(AbstractSession.java:493) at org.apache.sshd.common.session.helpers.AbstractSession.handleMessage(AbstractSession.java:463) at org.apache.sshd.common.session.helpers.AbstractSession.decode(AbstractSession.java:1325) at org.apache.sshd.common.session.helpers.AbstractSession.messageReceived(AbstractSession.java:424) at org.apache.sshd.common.session.helpers.AbstractSessionIoHandler.messageReceived(AbstractSessionIoHandler.java:67) at org.apache.sshd.common.io.nio2.Nio2Session.handleReadCycleCompletion(Nio2Session.java:285) at org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:265) at org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:262) at org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:37) at java.security.AccessController.doPrivileged(Native Method) at org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:34) at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) at sun.nio.ch.Invoker$2.run(Invoker.java:218) at sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745)
Notes
To our knowledge there is no known impact or user-visible effect from these exceptions, and ssh-related behavior is otherwise normal.
Workaround
It's possible that if running an older version of OpenSSH (pre 5.5), upgrading OpenSSH may help.