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x/crypto/ssh: unexpected packet #6169

gopherbot opened this issue Aug 16, 2013 · 9 comments

x/crypto/ssh: unexpected packet #6169

gopherbot opened this issue Aug 16, 2013 · 9 comments


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@gopherbot gopherbot commented Aug 16, 2013


What steps will reproduce the problem?
If possible, include a link to a program on
1. Run this test in sshpool:

What is the expected output?

The session should fail (due to the timeout) with a well-understood error

What do you see instead?

This will hit this unexpected code path in ssh/channel.go:

Which compiler are you using (5g, 6g, 8g, gccgo)?


Which operating system are you using?

Ubuntu 13.04 / Linux 3.8.0-27 x86_64

Which version are you using?  (run 'go version')

go version devel +01810e5c68e9 Mon Jun 03 13:20:17 2013 +0400 linux/amd64
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@robpike robpike commented Aug 17, 2013

Comment 1:

Labels changed: added priority-later, removed priority-triage, go1.2maybe.

Status changed to Accepted.

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@hanwen hanwen commented Aug 21, 2013

Comment 2:

I can't reproduce this on 
go version devel +cddeaea05b11 Wed Aug 21 18:51:37 2013 +0400 linux/amd64
parent: 142:1e7a3e301825 tip
 openpgp: Implement compressed data packets & add support for compressing data during symmetric encryption.
I'm on ubuntu 12.04.
$ go test -v 
=== RUN TestOpenReuse
--- PASS: TestOpenReuse (0.09 seconds)
=== RUN TestSessionTimeout
--- PASS: TestSessionTimeout (0.17 seconds)
=== RUN TestOpenDistinct
--- PASS: TestOpenDistinct (0.16 seconds)
=== RUN TestOpenFirstError
--- PASS: TestOpenFirstError (0.00 seconds)
=== RUN TestOpenRetry
--- PASS: TestOpenRetry (0.10 seconds)
=== RUN TestOpenSecondError
--- PASS: TestOpenSecondError (0.08 seconds)
ok   0.761s
can you see if what part of your environment causes this?
alternatively, it would be helpful to know the packet type, eg. changing the SSH error
to fmt.Errorf("%T", msg)
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@gopherbot gopherbot commented Aug 22, 2013

Comment 3 by

Sorry if I wasn't clear: this *doesn't* actually visibly manifest when you run the test
suite, because we've made `sshpool` more resilient to errors. But it *is* triggered;
that is, the "unexpected packet" error I mentioned above in `channel.go` is hit (it's
just that sshpool now works around it, like it works around connectivity errors).
I filed a bug because "unexpected packet" presumably means that a violation of some
internal contract is being hit: this doesn't seem like an error that a user should ever
see with a well-behaved client.
I'll tweak a branch of sshpool to actually print this error.
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@gopherbot gopherbot commented Aug 22, 2013

Comment 4 by

Ok, it looks like the current version of sshpool no longer triggers it due to some
reconnection logic changes. If I go back to `f7f9e575cb90c1cb120028cc228b4e458053c227`
in sshpool and make the following change to `channel.go` in the `ssh` package:
maciek@gamera:~/code/go/src/$ hg diff .
diff -r 9c36e9eca3b5 ssh/channel.go
--- a/ssh/channel.go    Mon Jul 29 15:32:19 2013 -0400
+++ b/ssh/channel.go    Thu Aug 22 13:51:10 2013 -0700
@@ -485,6 +485,8 @@
        return nil
    case *channelOpenFailureMsg:
        return errors.New(safeString(msg.Message))
+   default:
+       fmt.Printf("ssh: unexpected packet %v\n", msg)
    return errors.New("ssh: unexpected packet")
I see that the unexpected packet is actually `nil`:
ssh: unexpected packet <nil>
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@rsc rsc commented Nov 27, 2013

Comment 5:

Labels changed: added go1.3maybe.

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@dsymonds dsymonds commented Dec 4, 2013

Comment 6:

Labels changed: added packagebug, removed priority-later.

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@rsc rsc commented Dec 4, 2013

Comment 7:

Labels changed: added release-none, removed go1.3maybe.

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@rsc rsc commented Dec 4, 2013

Comment 8:

Labels changed: added repo-crypto.

@mikioh mikioh changed the title go.crypto/ssh: unexpected packet in go.crypto/ssh ssh: unexpected packet Jan 7, 2015
@rsc rsc added this to the Unplanned milestone Apr 10, 2015
@rsc rsc removed release-none labels Apr 10, 2015
@rsc rsc changed the title ssh: unexpected packet x/crypto/ssh: unexpected packet Apr 14, 2015
@rsc rsc modified the milestones: Unreleased, Unplanned Apr 14, 2015
@rsc rsc removed the repo-crypto label Apr 14, 2015
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@hanwen hanwen commented Aug 12, 2015

this is from before the big rewrite. This can be closed.


@hanwen hanwen closed this Aug 13, 2015
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