Server-policy access failure

1. Check if FortiWeb is accessible:

   • Check the network connectivity stated in Diagnosing server-policy connectivity issues to guarantee that FortiWeb can be accessed from the client

   • Check if DNS can be resolved successfully and correctly specified to the VIP of server-policy;

   • Bypass CDN/DNS (set a host entry in local machine/pc) and check if FortiWeb VIP is accessible;

     Add a host entry in local machine/pc:

     Win: C:\Windows\System32\drivers\etc\hosts

     Linux: /etc/hosts

     Or visit with curl --resolve:

     curl -I HTTP://<domain> --resolve <domain>:<port>:<IP address>

2. Check configuration on FortiWeb:

   • Check the opmode in show system settings; (different modes may have special limitation or requirement)

   • If HTTP & HTTPS are all enabled;

   • If HTTP/HTTPS service ports are correctly configured or can be successfully accessed;

   • If Redirect HTTP to HTTPS is enabled; (if yes, you may disable it and try whether HTTP and HTTPS access has different response);

   • If back-end server is correctly configured: pay special attention to port & SSL, single-server mode;

   • If HTTP2 is enabled; (if yes, you may disable it and test again);

   • If Cache&Compression are enabled; (if yes, you may disable it and test again);

   • If Machine-Learning is enabled; (if yes, you may disable it and test again);

3. Check back-end server status:

   • If health check is ON, check if back-end server status is up & stable;

   • If health check is OFF or it’s configured as single-server, visit the back-end server from a client or from the backend shell of FortiWeb to check the actual status of back-end server;

4. Capture packets on FortiWeb:

   Use GUI > System > Network > Packet Capture or tcpdump under CLI/root (or diagnose network sniffer) to check:

   • The request from client is correctly received by FortiWeb and forwarded to back-end servers;

   • The TCP packets can be received and TCP connection is established;

   • The SSL handshakes are successful. (Refer to SSL/TLS for detailed troubleshooting methods)

   • Check HTTP traffic. (Refer to SSL/TLS for how to decrypt SSL/TLS packets)

5. Check if the access is blocked by WAF modules:

   • Check attack logs to see why a request is blocked: main&sub types, signature types&ID, message details&matched pattern.

   • Remove the web protection profile or features included from the server-policy, and visit again;

   • Set noparse enable in server-policy policy to bypass WAF functions.

     Notes: this option applies to Reverse Proxy or True Transparent Proxy mode only, and please do not enable it on content routing, otherwise content routing will not work.

6. Collect diagnose output&debug logs for further analysis:

   • Turn on traffic-log with enable packet-log option to check HTTP request packet details;

   • Diagnose debug flow to check traffic flow processing details;

   • Capture traffic on FortiWeb at the same time and download the pcap files;

   • Turn /proc/tproxy/debug levels and check packets process in kernels:

   • Export configuration files and download debug logs via GUI.