- Access using regular OpenSSH client works fine.
- Access using libssh2 script works fine with other switch vendors (Arista, Brocade tested) and regular linux OpenSSH servers.
The problem was traced back to the fact that libssh2 uses an ssh banner of this form "SSH-2.0-libssh2_1.7.0_DEV" while a regular OpenSSH client has a banner of this form "SSH-2.0-OpenSSH_5.3”.
When the libssh2 script is tailored to send "SSH-2.0-OpenSSH_5.3” banner (pretending to be a regular OpenSSH client) the access works just fine.
EXOS sshd servers seems to somehow have a bug when dealing with some banners (or has a hard coded whitelist/blacklist of banners)
The issue is reproducible at will (with any version of EXOS supporting ssh). Just git clone the libssh2 repo, build the lib and use the ssh2 binary provided in the "examples" directory (against an ssh enabled Extreme switch)
I did'nt have any luck getting debug/verbose logging from the sshd process on the switch, the only events related to that process are never triggered (exsshd.DebugData, exsshd.DebugVerbose, exsshd.RejctConnAccessDeny)