The Customer Edge Router (CER) must filter inbound AS-SIP-TLS traffic addressed to the local Session Border Controller (SBC) based on the source address of the signaling messages.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-19664	VVoIP 6215	SV-21805r2_rule		Low

Description
The CER (premise or perimeter) router is the first line of defense at the gateway to the enclave or LAN. The data firewall and SBC functions are the second line of defense. The SBC processes VVoIP traffic in the form of AS-SIP-TLS and SRTP/SRTCP packets, and the CER must forward these packets to the SBC. A filter performed by the CER to prevent a denial-of-service is to filter the AS-SIP-TLS packets based on their source address. Within the DISN IPVS network, Local Session Controllers (LSC) only signal to their assigned Soft Switch (SS) and its backup. SSs are only to signal with their assigned LSCs, for which they are primary or backup, and other SSs. To support this, the SBC is required to authenticate the source of, and validate the integrity of, the signaling packets it receives and only process authenticated and valid packets, thereby only signaling with the appropriate devices. Still, the SBC could be flooded and overloaded with too many unauthenticated or invalid signaling packets. The CER can help prevent this by preventing signaling packets that are not sourced from authorized devices from ever reaching the SBC.

Description

The CER (premise or perimeter) router is the first line of defense at the gateway to the enclave or LAN. The data firewall and SBC functions are the second line of defense. The SBC processes VVoIP traffic in the form of AS-SIP-TLS and SRTP/SRTCP packets, and the CER must forward these packets to the SBC. A filter performed by the CER to prevent a denial-of-service is to filter the AS-SIP-TLS packets based on their source address. Within the DISN IPVS network, Local Session Controllers (LSC) only signal to their assigned Soft Switch (SS) and its backup. SSs are only to signal with their assigned LSCs, for which they are primary or backup, and other SSs. To support this, the SBC is required to authenticate the source of, and validate the integrity of, the signaling packets it receives and only process authenticated and valid packets, thereby only signaling with the appropriate devices. Still, the SBC could be flooded and overloaded with too many unauthenticated or invalid signaling packets. The CER can help prevent this by preventing signaling packets that are not sourced from authorized devices from ever reaching the SBC.

STIG	Date
Voice/Video over Internet Protocol (VVoIP) STIG	2017-04-05

Details

Check Text ( C-24034r2_chk )
Review site documentation to confirm the CER filters inbound AS-SIP-TLS traffic addressed to the local SBC based on the source address of the signaling messages. This supports the VVoIP system connecting to the DISN WAN for VVoIP transport between enclaves and the system providing Assured Services to any Command and Control (C2) user (Special-C2, C2, or C2-R). Permit inbound signaling messages sourced as follows: - When the enclave contains one or more Local Session Controllers (LSCs), filter on the IP addresses of the SBCs fronting the primary and secondary Soft Switches (SSs) associated with the enclave. - When the enclave contains an SS filter based on IP addresses of SBCs fronting the LSCs associated with the SS. If the CER does not filter inbound AS-SIP-TLS traffic addressed to the local SBC based on the source address of the signaling messages, this is a finding.

Check Text ( C-24034r2_chk )

Review site documentation to confirm the CER filters inbound AS-SIP-TLS traffic addressed to the local SBC based on the source address of the signaling messages. This supports the VVoIP system connecting to the DISN WAN for VVoIP transport between enclaves and the system providing Assured Services to any Command and Control (C2) user (Special-C2, C2, or C2-R). Permit inbound signaling messages sourced as follows:
- When the enclave contains one or more Local Session Controllers (LSCs), filter on the IP addresses of the SBCs fronting the primary and secondary Soft Switches (SSs) associated with the enclave.
- When the enclave contains an SS filter based on IP addresses of SBCs fronting the LSCs associated with the SS.

If the CER does not filter inbound AS-SIP-TLS traffic addressed to the local SBC based on the source address of the signaling messages, this is a finding.

Fix Text (F-20370r2_fix)
Implement the CER to filter inbound AS-SIP-TLS traffic addressed to the local SBC based on the source address of the signaling messages.