C2/B2-Series f/w 5.02.14.0002 Reboots with "sshd_undoquit / kex_dh_hash" Backtraces in Log

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Article ID: 14479 

Products
C2-Series, firmware 5.02.10.0003 through 5.02.17.0006
B2-Series, firmware 4.02.10.0003 through 4.02.17.0006 

Changes
Attempted an SSH management session from linux SSH client version OpenSSH_5.9p1, OpenSSH_6.2p2, or OpenSSH_6.2p3. 

Symptoms
Unit lockup, then reset.
Diagnostics include "sshd_undoquit" and "kex_dh_hash" BackTraces seen in the current.log (5487). 

For example:
<57> FEB 14 16:46:04 2012 STK1 BOOT[268430848]: bootos.c(1338) 22 %%
Start of Code - Build:04.02.10.0003 Date:Tue Aug 24 10:09:03 2010
BackTrace-0x00022928: sysReboot (0x22928) + 0x0
BackTrace-0x000318a8: SwitchReset (0x31800) + 0xa8
BackTrace-0x0002a728: log_error_nvram (0x2a62c) + 0xfc
BackTrace-0x00044534: osapiMalloc_track (0x44354) + 0x1e0
BackTrace-0x00cdead4: buffer_expand (0xcdea1c) + 0xb8
BackTrace-0x00cdedd4: buf_put_nbytes (0xcdeda4) + 0x30
BackTrace-0x00d1c21c: kex_dh_hash (0xd1c130) + 0xec
BackTrace-0x00d17fd4: v2ssh_init_transport (0xd128b4) + 0x5720
BackTrace-0x00d15edc: v2ssh_init_transport (0xd128b4) + 0x3628
BackTrace-0x00cf1648: dispatch_v2_server_msg (0xcf0dec) + 0x85c
BackTrace-0x00d0ea68: ssh_recv_thread (0xd0e194) + 0x8d4
BackTrace-0x00ce866c: sshd_undoquit (0xce7c3c) + 0xa30
BackTrace-0x00ce89cc: sshd_undoquit (0xce7c3c) + 0xd90
BackTrace-0x01094780: vxTaskEntry (0x1094718) + 0x68
BackTrace-symbol not found for 0x0
<110> FEB 14 16:46:34 2012 STK1 BOOT[203871872]: edb_bxs.c(948) 38 %%
Last switch reset caused by osapi.c(1168): Error code 0x002a5000,
after 12383112 second
Cause
During the key exchange init process, the unit freezes and resets due to non-availability of memory. 

Solution/Workaround
For the C2, upgrade to firmware 5.02.18.0002 or higher.
For the B2, upgrade to firmware 4.02.18.0002 or higher.
Version x.02.15.0002 release notes state, in the 'Firmware Changes and Enhancements' section:
16248    Addressed an issue whereby logging to the switch via OpenSSH_5.9p1 SSH client could potentially cause the unit to lock up or reset.
Version x.02.18.0002 release notes state, in the 'Firmware Changes and Enhancements' section:
18575   Corrected an interoperability issue with Openssh-client 1:6.2p2-3, that caused the switch to hang. This SSH client incorrectly has Clientkex length as a negative value. This client will not be supported.

Workaround: Upon new error message "hash mismatch - key_verify failed for server_host_key", use a different SSH Client application or version.
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Posted 5 years ago

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