Define SIP Message Blocklist/Allowlist
It's recommended to configure SIP message policy rules for blocking (blocklist) unwanted incoming SIP messages or allowing (allowlist) receipt of desired messages. This allows you to define legal and illegal characteristics of a SIP message.
SIP message policy is helpful against VoIP fuzzing (also known as robustness testing), which sends different types of packets to its "victims" for finding bugs and vulnerabilities. For example, the attacker might try sending a SIP message containing an oversized parameter or too many occurrences of a parameter.
Each SIP message policy rule can be configured with, for example, maximum message length, header length, body length, number of headers, and number of bodies. Each rule is then set as a blocklist or allowlist.
| ➢ | To configure SIP message blocklists and allowlists: |
| 1. | Open the Message Policies table (Setup menu > Signaling & Media tab > Message Manipulation folder > Message Policies). |
| 2. | Click New to configure a rule. |
The following displays an example of a configured rule that defines maximum SIP messages to 32,768 characters, maximum header length to 512 characters, and bodies to 1024 characters. Invalid requests are rejected. Only INVITE and BYE requests are permitted.
Configuring Message Policy Rule
