module

SSH Username Enumeration

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Disclosed
N/A
Created
2018-05-30

Description

This module uses a malformed packet or timing attack to enumerate users on
an OpenSSH server.

The default action sends a malformed (corrupted) SSH_MSG_USERAUTH_REQUEST
packet using public key authentication (must be enabled) to enumerate users.

On some versions of OpenSSH under some configurations, OpenSSH will return a
"permission denied" error for an invalid user faster than for a valid user,
creating an opportunity for a timing attack to enumerate users.

Testing note: invalid users were logged, while valid users were not. YMMV.

Authors

kenkeiras
Dariusz Tytko
Michal Sajdak
Qualys
wvu wvu@metasploit.com

References

Module Options

To display the available options, load the module within the Metasploit console and run the commands ‘show options’ or ‘show advanced’:


    msf > use auxiliary/scanner/ssh/ssh_enumusers
    msf auxiliary(ssh_enumusers) > show actions
        ...actions...
    msf auxiliary(ssh_enumusers) > set ACTION < action-name >
    msf auxiliary(ssh_enumusers) > show options
        ...show and set options...
    msf auxiliary(ssh_enumusers) > run
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