[thestig]

Oh, and the curl output - running with -I made it return "empty response" no matter if I fed it basic or digest creds, or what endpoint I hit.  But -vv gave what I think you wanted to see (using netrc to provide user/pass, and below I obscured sensitive info with italics):

curl -vv  -n   "http://CAMERA/cgi-bin/alarm.cgi?action=getOutSlots"
*   Trying CAMERAIP...
* TCP_NODELAY set
* Connected to CAMERA (CAMERAIP) port 80 (#0)
* Server auth using Basic with user 'MYUSER'
> GET /cgi-bin/alarm.cgi?action=getOutSlots HTTP/1.1
> Host: CAMERA
> Authorization: Basic YWRtaW46bGlidGFyZGk1
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 401 Unauthorized
< WWW-Authenticate: Digest realm="Login to FACTORYHOSTNAME",qop="auth",nonce="1484076709",opaque="8b4b92bf58d158222eca1dbf57140fe6c0b92f06"
< Connection: close
< CONTENT-LENGTH: 0
<
* Closing connection 0

If I append --digest to the arguments everything works.