I have tried using check_http but I get success even if the website is redirected to an error page
This can be solved with check_http --expect. Here is the documentation from check_http --help:
-e, --expect=STRING
Comma-delimited list of strings, at least one of them is expected in
the first (status) line of the server response (default: HTTP/1.)
If specified skips all other status line logic (ex: 3xx, 4xx, 5xx
processing)
The following example will return an 'OK' for a 200 OK HTTP response code, but will give a critical error for a 302 redirect.
host % check_http --expect=200
HTTP CRITICAL - Invalid HTTP response received from host: HTTP/1.0 301 OK
For a secure website (over SSL), and authentication, also check out the check_http --ssl and the --authorization flags.
-S, --ssl Connect via SSL. Port
defaults to 443
-a, --authorization=AUTH_PAIR
Username:password on sites with basic authentication
Or, perhaps you don't actually want to log into the system but just want to make sure that the page requires a username/password, because that username/password can become a security concern. In that case, try something like the following/ 401 is the HTTP response code for 'Unauthorized' or 'Authorization Required'-- the 401 is mandatory, the text string afterwards is optional and may say one of several different things, so I just tell Nagios to expect 401.
check_http --expect="401"
Best Answer
If you don't need to parse JSON output or the like, check_http, bundled in Nagios Core, could be the right tool for the job.
It has SNI support, HTTP methods, PKI certificates support, headers string check, response string/regex check.
Just give a look to all the switches invoking
check_http -h.