Inserting Customized SIP Headers in an Outgoing INVITE

When the Oracle Communications Session Border Controller establishes a new TLS connection, it caches the following peer certificate attributes:

• Certificate Subject Name
• Certificate Subject Alternative Name (only DNS)

The Oracle Communications Session Border Controller constructs a customized P-Certificate-Subject-Common-Name SIP header and inserts the header into the outgoing INVITE with the Certificate Subject Name. The Oracle Communications Session Border Controller also constructs and inserts in the outgoing INVITE one or more P-Certificate-Subject-Alternative-Name SIP headers.

If you enable this capability and the incoming INVITE already has P-Certificate-Subject-Common-Name and P-Certificate-Subject-Alternative-Name headers, the Oracle Communications Session Border Controller strips them before inserting the new customized ones. It does so to avoid the risk of any attempt to spoof the headers and thereby gain unauthorized access to the UM server.

The following diagram shows a scenario where the calling party establishes a TLS connection with the Oracle Communications Session Border Controller. Because mutual authentication is enabled, the Oracle Communications Session Border Controller receives the peer certificate and caches required information from it. This information is inserted in the outgoing INVITE.

The peer certificate from the calling party during the TLS handshake with the Oracle Communications Session Border Controller looks like the following example.

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 9 (0x9)
        Signature Algorithm: sha1WithRSAEncryption
        Issuer: C=US, ST=MA, L=Woburn, O=Smith Securities, OU=Certificate Authority Dept, CN=Smith Certificate Authority/emailAddress=[e-mail]
        Validity
            Not Before: Dec 10 21:14:56 2009 GMT
            Not After : Jul 11 21:14:56 2019 GMT
        Subject: C=US, ST=MA, L=Burlington, O=Acme Packet, OU=Certificate Authority Dept, CN=*.acme.com/emailAddress=[e-mail]
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (2048 bit)
        X509v3 extensions:
            X509v3 Basic Constraints:
            CA:FALSE
            X509v3 Issuer Alternative Name:
            email:[e-mail]
            X509v3 Subject Alternative Name:
            DNS:gw1.acme.com, DNS:gw3.ano.com, DNS:gw2.some.com
            X509v3 Key Usage: critical
            Digital Signature, Key Encipherment
    Signature Algorithm: sha1WithRSAEncryption

The outgoing SIP INVITE (INVITE 2 in the diagram) looks like the following sample. Bold text shows where the Oracle Communications Session Border Controller uses information from the certificate.

INVITE sip:[e-mail]:5060 SIP/2.0
Via: SIP/2.0/UDP 172.16.27.113:5060;branch=z9hG4bK4jmg29cmm8l0cg7smmrn85o4q7
From: 111111 <sip:[e-mail]>;tag=_ph1_tag
To: 222222 <sip:[e-mail]>
Call-ID: [e-mail]-1-
CSeq: 1 INVITE
Contact: <sip:111111@172.16.27.113:5060;transport=udp>
P-Certificate-Subject-Common-Name: *.acme.com
P-Certificate-Subject-Alternative-Name: gw1.acme.com
P-Certificate-Subject-Alternative-Name: gw3.ano.com
P-Certificate-Subject-Alternative-Name: gw2.some.com
Max-Forwards: 69
Subject: TBD
Content-Type: application/sdp
Content-Length: 138
Route: <sip:222222@172.16.27.188:5060;lr>
v=0
o=user1 53655765 2353687637 IN IP4 172.16.27.113
s=-
c=IN IP4 172.16.27.113
t=0 0
m=audio 20000 RTP/AVP 0
a=rtpmap:0 PCMU/8000