Appendix - Common Testing Commands¶
The following are some simple, but powerful commands that are useful in developing and troubleshooting SSL visibility projects.
Control the SSLFWD certificate cache
The behavior of the SSL Forward Proxy changes after a certificate is cached, which will make it difficult to troubleshoot some issues. The following allows you to both list and delete the certificates in the cache.
tmsh show ltm clientssl-proxy cached-certs clientssl-profile [CLIENTSSL PROFILE] virtual [INGRESS TCP VIP] tmsh delete ltm clientssl-proxy cached-certs clientssl-profile [CLIENTSSL PROFILE] virtual [INGRESS TCP VIP]
Isolate SSLO traffic
Any given website will be full of images, scripts, style sheets, and very often references to document objects on other sites (like a CDN). This can make troubleshooting very complex. The following cURL commands allow you to isolate traffic to a single request and response.
curl -vk https://www.bing.com curl -vk --proxy 10.30.0.150:3128 https://www.bing.com curl -vk --proxy 10.30.0.150:3128 --location https://www.bing.com
Optionally, between each cURL test, delete the certificate cache and start logging:
tmsh delete ltm clientssl-proxy cached-certs clientssl-profile [CLIENTSSL PROFILE] virtual [INGRESS TCP VIP] && tail –f /var/log/apm
There is simply nothing better than debug logging for troubleshooting SSL intercept issues. The SSL Orchestrator in debug mode pumps out an enormous set of logs, describing every step along a connection’s path. Remember to never leave debug logging enabled.
tail –f /var/log/apm
Second only to debug logging, packet captures are crucial to troubleshooting any network-dependent issue.
tcpdump –lnni [VLAN] [-Xs0]
In-line services create “source” (S) and “destination” (D) VLANs, and ICAP and receive-only services attach to existing VLANs. Drop a probe at each point in the path and observe flow.
ssldump –AdNd –i [VLAN] port 443 <and additional filters> tcpdump –i 0.0:nnn –nn –Xs0 –vv –w <file.pcap> <and additional filters> ssldump –nr <file.pcap> -H –S crypto > text-file.txt
TLS is rarely the issue, but a sight or configuration error may render some sites inaccessible.
Control the URL Filtering database
To show the current status of the database:
tmsh list sys url-db download-result
To initiate (force) the URL DB to update:
tmsh modify sys url-db download-schedule all status true download-now true
To verify that the URL DB is actively updating:
tcpdump -lnni 0.0 port 80 and host 126.96.36.199*
Plug the site’s address into SSLLabs.com server test site at https://www.ssllabs.com/ssltest/ to see if the site has any unusual SSL/TLS requirements.