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hierynomus / sshj

ssh, scp and sftp for java

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Remote port forwarding, dynamic port allocation fails w. BufferException: underflow

anderserik opened this issue · comments

commented

java version "1.7.0_95"
OpenJDK Runtime Environment (IcedTea 2.6.4) (7u95-2.6.4-0ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 24.95-b01, mixed mode)
sshj version: 0.15.0
OpenSSH version: SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7

--- Connection establishment ---
then:

int localPort = 9999;
InetSocketAddress socketAddress = new InetSocketAddress(LOCALHOST, localPort);
RemotePortForwarder remotePortForwarder = sshClient.getRemotePortForwarder();
remotePortForwarder.bind(new Forward(0), new SocketForwardingConnectListener(socketAddress));

Fails with BufferException: underflow

See trace:

10:22:37.345 {main} INFO  c.e.nsta.utils.console.SSHConsole - Succesfully connected to 10.64.77.30:22
10:22:37.348 {main} DEBUG n.s.sshj.connection.ConnectionImpl - Attaching opener for `forwarded-tcpip` channels: net.schmizz.sshj.connection.channel.forwarded.RemotePortForwarder@76639310
10:22:37.350 {main} DEBUG n.s.sshj.connection.ConnectionImpl - Making global request for `tcpip-forward`
10:22:37.351 {main} TRACE net.schmizz.sshj.transport.Encoder - Encoding packet #10: 50 00 00 00 0d 74 63 70 69 70 2d 66 6f 72 77 61 72 64 01 00 00 00 00 00 00 00 00
10:22:37.351 {main} DEBUG net.schmizz.concurrent.Promise - Awaiting <<global req for tcpip-forward>>
10:22:37.353 {reader} TRACE net.schmizz.sshj.transport.Decoder - Received packet #14: 51 00 00 a1 4d
10:22:37.354 {reader} TRACE n.s.sshj.transport.TransportImpl - Received packet REQUEST_SUCCESS
10:22:37.355 {reader} DEBUG net.schmizz.concurrent.Promise - Setting <<global req for tcpip-forward>> to `Buffer [rpos=6, wpos=10, size=1024]`
Exception in thread "main" net.schmizz.sshj.connection.ConnectionException: Underflow
    at net.schmizz.sshj.connection.channel.forwarded.RemotePortForwarder.bind(RemotePortForwarder.java:175)
    at com.ericsson.nsta.utils.console.SSHConsole.createRemoteTunnel(SSHConsole.java:405)
    at SSHPortForwardDemo.main(SSHPortForwardDemo.java:22)
Caused by: net.schmizz.sshj.common.Buffer$BufferException: Underflow
    at net.schmizz.sshj.common.Buffer.ensureAvailable(Buffer.java:131)
    at net.schmizz.sshj.common.Buffer.readUInt32(Buffer.java:296)
    at net.schmizz.sshj.common.Buffer.readUInt32AsInt(Buffer.java:291)
    at net.schmizz.sshj.connection.channel.forwarded.RemotePortForwarder.bind(RemotePortForwarder.java:173)
    ... 2 more
commented

Hi,

Thanks for the bug report, I've managed to reproduce this in a testcase in commit ca49ca3.

commented

Ok! I've found it, it was a race condition (debugging didn't trigger the exception) 😄