SIPCORE Working Group C. Holmberg
Internet-Draft Ericsson
Intended status: Standards Track J. Jiang
Expires: June 6, 2017 China Mobile
December 3, 2016
Session Initiation Protocol (SIP) Via header field parameter to indicate
received realm
draft-holmberg-dispatch-received-realm-12.txt
Abstract
This specification defines a new Session Initiation Protocol (SIP)
Via header field parameter, "received-realm", which allows a SIP
entity acting as an entry point to a transit network to indicate from
which adjacent upstream network a SIP request is received, using a
network realm value associated with the adjacent network.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 6, 2017.
Copyright Notice
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document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Use-Case: Transit Network Application Services . . . . . 3
1.3. Use-Case: Transit Network Routing . . . . . . . . . . . . 3
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Via 'received-realm' header field parameter . . . . . . . . . 5
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Operator Identifier . . . . . . . . . . . . . . . . . . . 5
5.3. JWS Header . . . . . . . . . . . . . . . . . . . . . . . 5
5.4. JWS Payload . . . . . . . . . . . . . . . . . . . . . . . 6
5.5. JWS Serialization . . . . . . . . . . . . . . . . . . . . 7
5.6. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.6.1. General . . . . . . . . . . . . . . . . . . . . . . . 7
5.6.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . 7
5.7. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. User Agent and Proxy behavior . . . . . . . . . . . . . . . . 8
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Behavior of a SIP entity acting as a network entry point 8
6.3. Behavior of a SIP entity consuming the received-network
value . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. 'received-realm' Via header field parameter . . . . . . . 9
8.2. JSON Web Token Claims Registration . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
1.1. General
When Session Initiation Protocol (SIP) [RFC3261] sessions are
established between networks belonging to different operators, or
between interconnected networks belonging to the same operator (or
enterprise), the SIP requests associated with the session might
traverse transit networks.
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Such transit networks might provide different kinds of services. In
order to provide such services, a transit network often needs to know
to which operator (or enterprise) the adjacent upstream network from
which the SIP session initiation request is received belongs.
This specification defines a new Session Initiation Protocol (SIP)
Via header field parameter, "received-realm", which allows a SIP
entity acting as an entry point to a transit network to indicate from
which adjacent upstream network a SIP request is received, using a
network realm value associated with the adjacent network.
NOTE: As the adjacent network can be an enterprise network, an Inter
Operator Identifier (IOI) cannot be used to identity the network, as
IOIs are not defined for enterprise networks.
The following sections describe use-cases where the information is
needed.
1.2. Use-Case: Transit Network Application Services
The 3rd Generation Partnership Project (3GPP) TS 23.228
[TS.3GPP.23.228] specifies how an IP Multimedia Subsystem (IMS)
network can be used to provide transit functionality. An operator
can use its IMS network to provide transit functionality e.g., to
non-IMS customers, to enterprise networks, and to other network
operators.
The transit network operator can provide application services to the
networks for which it is providing transit functionality. Transit
application services are typically not provided on a per user basis,
as the transit network does not have access to the user profiles of
the networks for which the application services are provided.
Instead, the application services are provided per served network.
When a SIP entity that provides application services (e.g., an
Application Server) within a transit network receives a SIP request,
in order to apply the correct services, it needs to know the adjacent
upstream network from which the SIP request is received.
1.3. Use-Case: Transit Network Routing
A transit network operator normally interconnects to many different
operators, including other transit network operators, and provides
transit routing of SIP requests received from one operator network
towards the destination. The destination can be within an operator
network to which the transit network operator has a direct
interconnect, or within an operator network that only can be reached
via one or more interconnected transit operators.
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For each customer, i.e., interconnected network operator, for which
the transit network operator routes SIP requests towards the
requested destination, a set of transit routing polices are defined.
These policies are used to determine how a SIP request shall be
routed towards the requested destination to meet the agreement the
transit network operator has with its customer.
When a SIP entity that performs the transit routing functionality
receives a SIP request, in order to apply the correct set of transit
routing policies, it needs to know from which of its customers, i.e.,
adjacent upstream network, the SIP request is received.
2. Applicability
The mechanism defined in this specification MUST only be used by SIP
entities that are able to verify from which adjacent upstream network
a SIP request is received.
The mechanism for verifying from which adjacent upstream network a
SIP request is received is outside the scope of this specification.
Such mechanism might be based for instance on receiving the SIP
request on an authenticated Virtual Private Network (VPN), receiving
the SIP request on a specific IP address, or on a specific network
access.
3. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
4. Definitions
SIP entity: SIP User Agent (UA), or SIP proxy, as defined in RFC
3261.
Adjacent upstream SIP network: The adjacent SIP network in the
direction from which a SIP request is received.
Network entry point: A SIP entity on the border of network, which
receives SIP requests from adjacent upstream networks.
Inter Operator Identifier (IOI): A globally unique identifier to
correlate billing information generated within the IP Multimedia
Subsystem (IMS).
JWS: JSON Web Signature, as defined in [RFC7515].
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5. Via 'received-realm' header field parameter
5.1. General
The Via 'received-realm' header field parameter value is represented
as a combination of an operator identifier, whose value represents
the adjacent network, and a serialized JSON Web Signature (JWS)
[RFC7515]. The JWS Payload consists of the operator identifier and
other SIP information element values.
The procedures for encoding the JWS and calculating the signature are
defined in [RFC7515]. As the JWS Payload information is found in
other SIP information elements, the JWS Payload is detached from the
serialized JWS conveyed in the header field parameter, as described
in Appendix F of [RFC7515]. The operator identifier and the
serialized JWS are separated using a colon character.
5.2. Operator Identifier
The Operator Identifier is a token value that represents the adjacent
operator. The scope of the value is only within the network that
inserts the value.
The Operator Identifier value is case-insensitive.
5.3. JWS Header
The following header parameters MUST be included in the JWS.
o The "typ" parameter MUST have a "JWT" value.
o The "alg" parameter MUST have the value of the algorithm used to
calculate the JWS.
NOTE: Operators need to agree on the set of supported algorithms for
calculating the JWT signature.
NOTE: The "alg" parameter values for specific algorithms are listed
in the IANA JSON Web Signature and Encryption Algorithms sub-registry
of the JSON Object Signing and Encryption (JOSE) registry. Operators
need to use algorithms for which an associated "alg" parameter value
has been registered. The procedures for defining new values are
defined in [RFC7518].
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Example:
{
"typ":"JWT",
"alg":"HS256"
}
5.4. JWS Payload
The following claims MUST be included in the JWS Payload:
o The "sip_from_tag" claim has the value of the From 'tag' header
field parameter of the SIP message.
o The "sip_date" claim has the value of the Date header field in the
SIP message, encoded in JSON NumericDate format [RFC7519].
o The "sip_callid" claim has have value of the Call-ID header field
in the SIP message.
o The "sip_cseq_num" claim has the numeric value of the CSeq header
field in the SIP message.
o the "sip_via_branch" claim has value of the Via branch header
field parameter of the Via header field, in the SIP message, to
which the received-realm header field parameter is attached.
o the "sip_via_opid" claim has value of the operator identifier part
of the Via received-realm header field parameter of the Via header
field, in the SIP message, to which the received-realm header
field parameter is attached.
Example:
{
"sip_from_tag":"1928301774",
"sip_date":1472815523,
"sip_callid":"a84b4c76e66710@pc33.atlanta.com",
"sip_cseq_num":"314159",
"sip_via_branch":"z9hG4bK776asdhds",
"sip_via_opid":"myoperator"
}
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5.5. JWS Serialization
As the JWS Payload is not carried in the received-realm parameter, in
order to make sure that the sender and the receiver construct the JWS
Payload object in the same way, the JSON representation of the JWS
Payload object it MUST be computed as follows:
o All claims MUST be encoded using lower case characters.
o The claims MUST be in the same order as listed in [Section 5.4].
o All claims except "sip_date" MUST be encoded as StringOrURI JSON
string value [RFC7519].
o The "sip_date" claim MUST be encoded as a JSON NumericDate value
[RFC7519].
o The JWS Payload MUST follow the rules for the construction of the
thumbprint of a JSON Web Key (JWK) as defined in [RFC7638]
Section 3 Step 1 only.
Example:
NOTE: Line breaks for display purpose only
{"sip_from_tag":"1928301774","sip_date":1472815523,
"sip_callid":"a84b4c76e66710@pc33.atlanta.com","sip_cseq_num":"314159",
"sip_via_branch":"z9hG4bK776asdhds","sip_via_opid":"myoperator"}
5.6. Syntax
This section describes the syntax extensions to the ABNF syntax
defined in [RFC3261], by defining a new Via header field parameter,
"received-realm". The ABNF defined in this specification is
conformant to RFC 5234 [RFC5234]. "EQUAL", "LDQUOT", "RDQUOT" and
"ALPHA" are defined in [RFC3261]. "DIGIT" is defined in [RFC5234].
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via-params =/ received-realm
received-realm = "received-realm" EQUAL LDQUOT op-id COLON jws RDQUOT
op-id = token
jws = header ".." signature
header = 1*base64-char
signature = 1*base64-char
base64-char = ALPHA / DIGIT / "/" / "+"
EQUAL, COLON, token, LDQUOT, RDQUOT, ALPHA and DIGIT
as defined in [RFC3261].
NOTE: The two adjacent dots in the jws part is due to the detached
payload being replaced by an empty string [RFC7515].
5.7. Example
Via: SIP/2.0/UDP pc33.example.com;branch=z9hG4bK776;
received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1N..
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
NOTE: Line breaks for display purpose only
6. User Agent and Proxy behavior
6.1. General
This section describes how a SIP entity, acting as an entry point to
a network, uses the "received-realm" Via header field parameter.
6.2. Behavior of a SIP entity acting as a network entry point
When a SIP entity, acting as a network entry point, forwards a SIP
request, or initiates a SIP request on its own (e.g., a PSTN
gateway), the SIP entity adds a Via header field to the SIP request,
according to the procedures in RFC 3261 [RFC3261]. In addition, if
the SIP entity is able to assert the adjacent upstream network, and
if the SIP entity is aware of a network realm value defined for that
network, the SIP entity can add a "received-realm" Via header field
parameter, conveying the network realm value as the operator
identifier (Section 5.2) part of the header field parameter, to the
Via header field added to the SIP request.
In addition the SIP entity MUST also calculate a JWS (Section 5.4)
and add the calculated JWS Header and JWS Signature as the jws part
of the Via header field parameter.
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6.3. Behavior of a SIP entity consuming the received-network value
When a SIP entity receives a Via 'received-network' header field
parameter, and intends to perform actions based on the header field
parameter value, it MUST first re-calculate the JWS and check whether
the result matches the JWS received. If there is not a match, the
SIP entity MUST discard the received 'received-network' header field
parameter. The SIP entity MAY take also take additional actions
(e.g., rejecting the SIP request) based on local policy.
7. Example
Operator 1 T_EP T_AS
- INVITE ------>
Via: SIP/2.0/UDP IP_UA
-- INVITE ---------------------------->
Via: SIP/2.0/UDP IP_TEP;branch=z9hG4bK776;
received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJh
bGciOiJIUzI1N..dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW
1gFWFOEjXk"
Via: SIP/2.0/UDP IP_UA; received=IP_UA
<- 200 OK ----------------------------
Via: SIP/2.0/UDP IP_TEP;branch=z9hG4bK776;
received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJh
bGciOiJIUzI1N..dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW
1gFWFOEjXk"
Via: SIP/2.0/UDP IP_UA; received=IP_UA
<- 200 OK------
Via: SIP/2.0/UDP IP_UA; received=IP_UA
8. IANA Considerations
8.1. 'received-realm' Via header field parameter
This specification defines a new Via header field parameter called
received-realm in the "Header Field Parameters and Parameter Values"
sub-registry as per the registry created by [RFC3968]. The syntax is
defined in Section 5.6. The required information is:
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Predefined
Header Field Parameter Name Values Reference
---------------------- --------------------- ---------- ---------
Via received-realm No RFCXXXX
8.2. JSON Web Token Claims Registration
This specification defines new JSON Web Token claims in the "JSON Web
Token Claims" sub-registry as per the registry created by [RFC7519].
Claim Name: "sip_from_tag"
Claim : SIP From tag header field parameter value
Change Controller: IESG
Specification Document(s): RFC XXXX, RFC 3261
Claim Name: "sip_date"
Claim Description: SIP Date header field value
Change Controller: IESG
Specification Document(s): RFC XXXX, RFC 3261
Claim Name: "sip_callid"
Claim Description: SIP Call-Id header field value
Change Controller: IESG
Specification Document(s): RFC XXXX, RFC 3261
Claim Name: "sip_cseq_num"
Claim Description: SIP CSeq numeric header field parameter value
Change Controller: IESG
Specification Document(s): RFC XXXX, RFC 3261
Claim Name: "sip_via_branch"
Claim Description: SIP Via branch header field parameter value
Change Controller: IESG
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Specification Document(s): RFC XXXX, RFC 3261
9. Security Considerations
As the received-realm Via header field parameter can be used to
trigger applications, it is important to ensure that the parameter
has not been added to the SIP message by an unauthorized SIP entity.
The received-realm Via header field parameter is inserted, signed,
verified and consumed within an operator network. The operator MUST
discard parameters received from another network, and the parameter
MUST only be inserted by SIP entities that are able to verify from
which adjacent upstream network a SIP request is received.
The operator also needs to take great care in ensuring that the key
used to calculate the JWS signature value is only known by the
network entities signing and adding the JWS signature to the
received-realm Via header field parameter of a SIP message, and to
network entities verifying and consuming the parameter value.
The operator MUST use a key management policy that protects agains
unauthorised access to the stored keys within nodes where they keys
associated with the JWS signature are stored, and that protects
against crypto analysis attacks using captured data sent on the wire.
A SIP entity MUST NOT use the adjacent network information if there
is a mismatch between the JWS signature received in the SIP header
field and the JWS signature calculated by the receiving entity.
Generic security considerations for JWS are defined in [RFC7515].
10. Acknowledgments
Thanks to Adam Roach and Richard Barnes for providing comments and
feedback on the document. Francis Dupoint performed the Gen-ART
review.
11. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-holmberg-dispatch-received-realm-11
o Editorial change based on IESG review.
Changes from draft-holmberg-dispatch-received-realm-10
o Changes based on IESG review.
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o Changes based on SecDIR review.
o Changes based on IANA Service Operator review.
Changes from draft-holmberg-dispatch-received-realm-09
o Reference to RFC 2104 removed.
Changes from draft-holmberg-dispatch-received-realm-08
o Editorial fixed based on Gen-ART review.
o Editorial fixes based on comments from IANA Service Operator
review.
o - Quotes removed from sip_date value.
Changes from draft-holmberg-dispatch-received-realm-07
o Editorial changes.
Changes from draft-holmberg-dispatch-received-realm-06
o Changes based on AD review by Ben Campbell:
o - operator-id added to JSON Payload
Changes from draft-holmberg-dispatch-received-realm-05
o Editorial fixes.
Changes from draft-holmberg-dispatch-received-realm-04
o JSON serialization procedure added.
Changes from draft-holmberg-dispatch-received-realm-03
o ABNF correction.
Changes from draft-holmberg-dispatch-received-realm-02
o JWT replaced with JWS.
o Appendix F of RFC 7515 applied.
Changes from draft-holmberg-dispatch-received-realm-01
o Define received-realm parameter value as a JSON Web Token (JWT).
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Changes from draft-holmberg-dispatch-received-realm-00
o New version due to expiration of previous version.
Changes from draft-holmberg-received-realm-04
o Changed IETF WG from sipcore do dispatch.
o HMAC value added to the parameter.
Changes from draft-holmberg-received-realm-03
o New version due to expiration.
Changes from draft-holmberg-received-realm-02
o New version due to expiration.
Changes from draft-holmberg-received-realm-01
o New version due to expiration.
Changes from draft-holmberg-received-realm-00
o New version due to expiration.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
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[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <http://www.rfc-editor.org/info/rfc7638>.
12.2. Informative References
[RFC3968] Camarillo, G., "The Internet Assigned Number Authority
(IANA) Header Field Parameter Registry for the Session
Initiation Protocol (SIP)", BCP 98, RFC 3968,
DOI 10.17487/RFC3968, December 2004,
<http://www.rfc-editor.org/info/rfc3968>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>.
[TS.3GPP.23.228]
3GPP, "IP Multimedia Subsystem (IMS); Stage 2", 3GPP
TS 23.228 14.1.0, September 2016.
Authors' Addresses
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Yi Jiang
China Mobile
No.32 Xuanwumen West Street
Beijing Xicheng District 100053
P.R. China
Email: jiangyi@chinamobile.com
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