error handling + support offlinehttp in flow templates

[tarunKoyalwar]

Proposed Changes

• support for offlinehttp /passive mode in flow executer
  • in flow http is represented by http() but offlinehttp was represented by offlinehttp() hence flow engine / templates were not working in passive mode
• this is resolved now in addition to extra error handling
• closes nuclei panic when using with passive mode #4652

[tarunKoyalwar]

example offline response

GET / HTTP/1.1
Host: hm.baidu.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.41 Safari/537.36 Edg/101.0.1210.26
Accept-Charset: utf-8
Accept-Encoding: gzip

HTTP/1.1 200 OK
Connection: close
Content-Type: text/plain; charset=utf-8
Date: Wed, 17 Jan 2024 11:01:36 GMT
Server: apache
Strict-Transport-Security: max-age=172800
Content-Length: 0




https://hm.baidu.com

example nuclei run

$ ./nuclei -passive -u hm.baidu.com.response.txt -v -id ruijie-rg-eg-web-mis-rce -debug

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.1.5

		projectdiscovery.io

[WRN] Excluded 34 template[s] with known weak matchers / tags excluded from default run using .nuclei-ignore
[INF] Current nuclei version: v3.1.5 (latest)
[INF] Current nuclei-templates version: v9.7.4 (latest)
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 6
[INF] Templates loaded for current scan: 1
[INF] Executing 1 signed templates from projectdiscovery/nuclei-templates
[INF] Targets loaded for current scan: 1
[INF] [ruijie-rg-eg-web-mis-rce] Dumped offline-http request for hm.baidu.com.response.txt
GET / HTTP/1.1
Host: hm.baidu.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.41 Safari/537.36 Edg/101.0.1210.26
Accept-Charset: utf-8
Accept-Encoding: gzip

HTTP/1.1 200 OK
Connection: close
Content-Type: text/plain; charset=utf-8
Date: Wed, 17 Jan 2024 11:01:36 GMT
Server: apache
Strict-Transport-Security: max-age=172800
Content-Length: 0




https://hm.baidu.com
[INF] No results found. Better luck next time!