Bug 498514 – net-misc/openssh-6.4_p1[hpn]: bad packet length when connecting with another openssh 6.4 client (server on arm)

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Stefan Langenmaier 2014-01-19 02:44:32 UTC]

After a recent update locally and on the server I could no longer connect via ssh. I always received:

Bad packet length 3050708630.
Disconnecting: Packet corrupt 


Reproducible: Always

Steps to Reproduce:
1. connect with a openssh 6.4 client to openssh 6.4 server with hpn useflag enabled
2. enter password

Actual Results:  
receive error message

Expected Results:  
get logged in successfully


I could connect before I updated the client and I can still from other computers that have an older version, like 5.9, installed.

I tried on the client with hpn useflag enabled and disabled. Both times with the same errors.

When I choose specifically another cipher like arcfour I could create the connection to the server. (ssh -o "Ciphers=arcfour256" user@server) 

After I disabled the hpn useflag on the server I could again connect without setting explicitly a Cipher.

The content of

cat /etc/ssh/ssh_config | grep Ciphers
#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc

The server is an arm v5.
The client is a x86 Atom N270.

I'm not really sure how to further debug this or where to post this as I'm unsure if "hpn" is an official part of openssh.

[Comment 1 Andreas K. Hüttel 2014-03-17 09:40:35 UTC]

I can confirm this, and interestingly the server is also here arm5

The problem occurred after upgrading the server; new client and old server worked fine.

[Comment 2 Markus Meier 2014-03-17 22:21:11 UTC]

IIRC this is an unaligned memory access. echo 3 > /proc/cpu/alignment should work around the "Bad packed length" issue.

[Comment 3 SpanKY 2014-03-18 01:42:02 UTC]

please retest w/openssh-6.5_p1-r1