extensions.conf

[incoming]
exten => s,1,LookupBlacklist(j)
exten => s,2,Dial(SIP/101,15)
exten => s,3,Answer
exten => s,4,Wait(1)
exten => s,6,Voicemail(u1)
exten => s,7,Hangup
exten => s,102,Goto(authenticate,s,1) 

[authenticate]
exten => s,1,Answer 
exten => s,2,Authenticate(/etc/asterisk/passwdfile) 
exten => s,3,System(/usr/local/bin/opendoor) 

To use this users numbers must be added to the blacklist db. The following was pulled from voip-info wiki:

To insert a number into the Black list from the CLI
database put blacklist <name/number> 1
eg. database put blacklist 0123456789 1
Stores 0123456789 as a blackilsted CallerID

To delete a number from the blacklist using the CLI
database del blacklist <name/number>
eg. database del blacklist 0123456789
Deletes 0123456789 from the blacklist database 

pin codes must be added one per line in /etc/asterisk/passwdfile