draft-ietf-stir-rfc4474bis-06.txt   draft-ietf-stir-rfc4474bis-07.txt 
Network Working Group J. Peterson Network Working Group J. Peterson
Internet-Draft NeuStar Internet-Draft NeuStar
Intended status: Standards Track C. Jennings Intended status: Standards Track C. Jennings
Expires: April 21, 2016 Cisco Expires: August 6, 2016 Cisco
E. Rescorla E. Rescorla
RTFM, Inc. RTFM, Inc.
C. Wendt C. Wendt
Comcast Comcast
October 19, 2015 February 3, 2016
Authenticated Identity Management in the Session Initiation Protocol Authenticated Identity Management in the Session Initiation Protocol
(SIP) (SIP)
draft-ietf-stir-rfc4474bis-06.txt draft-ietf-stir-rfc4474bis-07.txt
Abstract Abstract
The baseline security mechanisms in the Session Initiation Protocol The baseline security mechanisms in the Session Initiation Protocol
(SIP) are inadequate for cryptographically assuring the identity of (SIP) are inadequate for cryptographically assuring the identity of
the end users that originate SIP requests, especially in an the end users that originate SIP requests, especially in an
interdomain context. This document defines a mechanism for securely interdomain context. This document defines a mechanism for securely
identifying originators of SIP requests. It does so by defining a identifying originators of SIP requests. It does so by defining a
SIP header field for conveying a signature used for validating the SIP header field for conveying a signature used for validating the
identity, and for conveying a reference to the credentials of the identity, and for conveying a reference to the credentials of the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2016. This Internet-Draft will expire on August 6, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of Operations . . . . . . . . . . . . . . . . . . . 6 3. Overview of Operations . . . . . . . . . . . . . . . . . . . 6
4. Signature Generation and Validation . . . . . . . . . . . . . 7 4. Signature Generation and Validation . . . . . . . . . . . . . 7
4.1. Authentication Service Behavior . . . . . . . . . . . . . 7 4.1. Authentication Service Behavior . . . . . . . . . . . . . 7
4.2. Verifier Behavior . . . . . . . . . . . . . . . . . . . . 9 4.2. Verifier Behavior . . . . . . . . . . . . . . . . . . . . 9
5. Credentials . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Credentials . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Credential Use by the Authentication Service . . . . . . 11 5.1. Credential Use by the Authentication Service . . . . . . 11
5.2. Credential Use by the Verification Service . . . . . . . 12 5.2. Credential Use by the Verification Service . . . . . . . 12
5.3. Handling 'info' parameter URIs . . . . . . . . . . . . . 13 5.3. Handling 'info' parameter URIs . . . . . . . . . . . . . 13
5.4. Credential System Requirements . . . . . . . . . . . . . 13 5.4. Credential System Requirements . . . . . . . . . . . . . 13
6. Identity Types . . . . . . . . . . . . . . . . . . . . . . . 14 6. Identity Types . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Telephone Numbers . . . . . . . . . . . . . . . . . . . . 14 6.1. Telephone Numbers . . . . . . . . . . . . . . . . . . . . 15
6.1.1. Canonicalization Procedures . . . . . . . . . . . . . 15 6.1.1. Canonicalization Procedures . . . . . . . . . . . . . 15
6.2. Domain Names . . . . . . . . . . . . . . . . . . . . . . 17 6.2. Domain Names . . . . . . . . . . . . . . . . . . . . . . 17
7. Header Syntax . . . . . . . . . . . . . . . . . . . . . . . . 18 7. Header Syntax . . . . . . . . . . . . . . . . . . . . . . . . 18
8. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 21 8. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 21
9. Gatewaying to JWT for non-SIP Transit . . . . . . . . . . . . 22 9. Gatewaying to PASSporT for non-SIP Transit . . . . . . . . . 22
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . . 24 11. Security Considerations . . . . . . . . . . . . . . . . . . . 24
11.1. Protected Request Fields . . . . . . . . . . . . . . . . 24 11.1. Protected Request Fields . . . . . . . . . . . . . . . . 24
11.1.1. Protection of the To Header and Retargeting . . . . 25 11.1.1. Protection of the To Header and Retargeting . . . . 26
11.2. Unprotected Request Fields . . . . . . . . . . . . . . . 26 11.2. Unprotected Request Fields . . . . . . . . . . . . . . . 26
11.3. Malicious Removal of Identity Headers . . . . . . . . . 27 11.3. Malicious Removal of Identity Headers . . . . . . . . . 27
11.4. Securing the Connection to the Authentication Service . 27 11.4. Securing the Connection to the Authentication Service . 28
11.5. Authorization and Transitional Strategies . . . . . . . 28 11.5. Authorization and Transitional Strategies . . . . . . . 29
11.6. Display-Names and Identity . . . . . . . . . . . . . . . 29 11.6. Display-Names and Identity . . . . . . . . . . . . . . . 30
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
12.1. Identity-Info Parameters . . . . . . . . . . . . . . . . 30 12.1. Identity-Info Parameters . . . . . . . . . . . . . . . . 30
12.2. Identity-Info Algorithm Parameter Values . . . . . . . . 30 12.2. Identity-Info Algorithm Parameter Values . . . . . . . . 30
12.3. spec parameter Names . . . . . . . . . . . . . . . . . . 30
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
14. Changes from RFC4474 . . . . . . . . . . . . . . . . . . . . 31 14. Changes from RFC4474 . . . . . . . . . . . . . . . . . . . . 31
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
15.1. Normative References . . . . . . . . . . . . . . . . . . 31 15.1. Normative References . . . . . . . . . . . . . . . . . . 31
15.2. Informative References . . . . . . . . . . . . . . . . . 32 15.2. Informative References . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
This document provides enhancements to the existing mechanisms for This document provides enhancements to the existing mechanisms for
authenticated identity management in the Session Initiation Protocol authenticated identity management in the Session Initiation Protocol
(SIP, [RFC3261]). An identity, for the purposes of this document, is (SIP, [RFC3261]). An identity, for the purposes of this document, is
defined as either a SIP URI, commonly a canonical address-of-record defined as either a SIP URI, commonly a canonical address-of-record
(AoR) employed to reach a user (such as (AoR) employed to reach a user (such as
'sip:alice@atlanta.example.com'), or a telephone number, which can be 'sip:alice@atlanta.example.com'), or a telephone number, which can be
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Internet. Telephone numbers do not share the domain-scope property Internet. Telephone numbers do not share the domain-scope property
described above, as they are dialed without any domain component. described above, as they are dialed without any domain component.
This document thus assumes the existence of a separate means of This document thus assumes the existence of a separate means of
establishing authority over telephone numbers, for cases where the establishing authority over telephone numbers, for cases where the
telephone number is the identity of the user. As with SIP URIs, the telephone number is the identity of the user. As with SIP URIs, the
necessary credentials to prove authority for a name might reside necessary credentials to prove authority for a name might reside
either in the endpoint or at some intermediary. either in the endpoint or at some intermediary.
This document specifies a means of sharing a cryptographic assurance This document specifies a means of sharing a cryptographic assurance
of end-user SIP identity in an interdomain or intradomain context. of end-user SIP identity in an interdomain or intradomain context.
It relies on the authentication service constructing JSON [RFC7159] It relies on the authentication service constructing tokens based on
objects composed of certain header field values taken from the SIP the [ietf-stir-passport] format, a JSON [RFC7159] object comprising
request. The authentication service then computes a signature over values copied from certain header field values in the SIP request.
those JSON object in a manner following JWT [RFC7519]. That The authentication service then computes a signature over those JSON
signature is then placed in a SIP Identity header. In order to object in a manner following PASSporT. That signature is then placed
assist in the validation of the Identity header, this specification in a SIP Identity header. In order to assist in the validation of
also describes some metadata fields associated with the header that the Identity header, this specification also describes some metadata
can be used by the recipient of a request to recover the credentials fields associated with the header that can be used by the recipient
of the signer. Note that the scope of this document is limited to of a request to recover the credentials of the signer. Note that the
providing this identity assurance for SIP requests; solving this scope of this document is limited to providing this identity
problem for SIP responses is outside the scope of this work (see assurance for SIP requests; solving this problem for SIP responses is
[RFC4916]). Future specifications may detail how the JSON object outside the scope of this work (see [RFC4916]). Future work might
constructed and signed by this mechanism might be used with other specify ways that a SIP implementation could gateway PASSporT objects
protocols, or further gateway operations upon this object. to other protocols.
This specification allows either a user agent or a proxy server to This specification allows either a user agent or a proxy server to
provide the authentication service function and/or the verification provide the authentication service function and/or the verification
service function. To maximize end-to-end security, it is obviously service function. To maximize end-to-end security, it is obviously
preferable for end-users to acquire their own credentials; if they preferable for end-users to acquire their own credentials; if they
do, their user agents can act as authentication services. However, do, their user agents can act as authentication services. However,
for some deployments, end-user credentials may be neither practical for some deployments, end-user credentials may be neither practical
nor affordable, given the potentially large number of SIP user agents nor affordable, given the potentially large number of SIP user agents
(phones, PCs, laptops, PDAs, gaming devices) that may be employed by (phones, PCs, laptops, PDAs, gaming devices) that may be employed by
a single user. In such environments, synchronizing keying material a single user. In such environments, synchronizing keying material
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Alice generates an INVITE and places her identity, in this case her Alice generates an INVITE and places her identity, in this case her
address-of-record, in the From header field of the request. She then address-of-record, in the From header field of the request. She then
sends an INVITE over TLS to an authentication service proxy for the sends an INVITE over TLS to an authentication service proxy for the
example.com domain. example.com domain.
The authentication service authenticates Alice (possibly by sending a The authentication service authenticates Alice (possibly by sending a
Digest authentication challenge) and validates that she is authorized Digest authentication challenge) and validates that she is authorized
to assert the identity that she populated in the From header field. to assert the identity that she populated in the From header field.
This value is Alice's AoR, but in other cases it could be some This value is Alice's AoR, but in other cases it could be some
different value that the proxy server has authority over, such as a different value that the proxy server has authority over, such as a
telephone number. The proxy then constructs an object composed of telephone number. The authentication service then constructs a JSON
some particular headers and fields, including part of the From header PASSporT object that mirrors particular SIP headers and fields,
field of the message, and generates a hash of the object. This hash including part of the From header field of the message, and generates
is then signed with the appropriate credential for the identity a hash of the object. This hash is then signed with the appropriate
(example.com, in the sip:alice@example.com case) and the signature is credential for the identity (example.com, in the
inserted into the Identity header field value of the request. sip:alice@example.com case) and the signature is inserted by the
proxy server into the Identity header field value of the request.
The proxy, as the holder of the private key for the example.com The proxy, as the holder of the private key for the example.com
domain, is asserting that the originator of this request has been domain, is asserting that the originator of this request has been
authenticated and that she is authorized to claim the identity that authenticated and that she is authorized to claim the identity that
appears in the From header field. The proxy inserts an "info" appears in the From header field. The proxy inserts an "info"
parameter into the Identity header that tells Bob how to acquire parameter into the Identity header that tells Bob how to acquire
keying material necessary to validate its credentials (a public key), keying material necessary to validate its credentials (a public key),
in case he doesn't already have it. in case he doesn't already have it.
When Bob's domain receives the request, it verifies the signature When Bob's domain receives the request, it verifies the signature
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agent server (UAS). As the request has been validated, it is agent server (UAS). As the request has been validated, it is
rendered to Bob. If the validation was unsuccessful, some other rendered to Bob. If the validation was unsuccessful, some other
treatment would be applied by the receiving domain. treatment would be applied by the receiving domain.
4. Signature Generation and Validation 4. Signature Generation and Validation
4.1. Authentication Service Behavior 4.1. Authentication Service Behavior
This document specifies a role for SIP entities called an This document specifies a role for SIP entities called an
authentication service. The authentication service role can be authentication service. The authentication service role can be
instantiated either by an intermediary such as a proxy server or by a instantiated, for example, by an intermediary such as a proxy server
user agent. Any entity that instantiates the authentication service or by a user agent. Any entity that instantiates the authentication
role MUST possess the private key of one or more credentials that can service role MUST possess the private key of one or more credentials
be used to sign for a domain or a telephone number (see Section 5.1). that can be used to sign for a domain or a telephone number (see
Intermediaries that instantiate this role MUST be capable of Section 5.1). Intermediaries that instantiate this role MUST be
authenticating one or more SIP users who can register for that capable of authenticating one or more SIP users who can register for
identity. Commonly, this role will be instantiated by a proxy that identity. Commonly, this role will be instantiated by a proxy
server, since these entities are more likely to have a static server, since these entities are more likely to have a static
hostname, hold corresponding credentials, and have access to SIP hostname, hold corresponding credentials, and have access to SIP
registrar capabilities that allow them to authenticate users. It is registrar capabilities that allow them to authenticate users. It is
also possible that the authentication service role might be also possible that the authentication service role might be
instantiated by an entity that acts as a redirect server, but that is instantiated by an entity that acts as a redirect server, but that is
left as a topic for future work. left as a topic for future work.
An authentication service adds the Identity header to SIP requests. An authentication service adds the Identity header to SIP requests.
The procedures below define the steps that must be taken when each an The procedures below define the steps that must be taken when each an
header is added. More than one may appear in a single request, and header is added. More than one may appear in a single request, and
an authentication service may add an Identity header to a request an authentication service may add an Identity header to a request
that already contains one or more Identity headers. If the Identity that already contains one or more Identity headers. If the Identity
header added follows extended signing procedures beyond the baseline header added follows extended signing procedures beyond the baseline
given in Section 7, then it differentiates the header with a "spec" given in Section 7, then it differentiates the header with a "type"
parameter per the fourth step below. parameter per the fourth step below.
Entities instantiating the authentication service role perform the Entities instantiating the authentication service role perform the
following steps, in order, to generate an Identity header for a SIP following steps, in order, to generate an Identity header for a SIP
request: request:
Step 1: Step 1:
First, the authentication service must determine whether it is First, the authentication service must determine whether it is
authoritative for the identity of the sender of the request. In authoritative for the identity of the sender of the request. In
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it to the domain(s) for which it is responsible (following the it to the domain(s) for which it is responsible (following the
procedures in RFC 3261 [RFC3261], Section 16.4). If the identity procedures in RFC 3261 [RFC3261], Section 16.4). If the identity
field uses the TEL URI scheme [RFC3966], or the identity field is a field uses the TEL URI scheme [RFC3966], or the identity field is a
SIP or SIPS URI with a telephone number in the user portion, the SIP or SIPS URI with a telephone number in the user portion, the
authentication service determines whether or not it is responsible authentication service determines whether or not it is responsible
for this telephone number; see Section 6.1 for more information. An for this telephone number; see Section 6.1 for more information. An
authentication service proceeding with a signature over a telephone authentication service proceeding with a signature over a telephone
number MUST then follow the canonicalization procedures described in number MUST then follow the canonicalization procedures described in
Section 6.1.1. If the authentication service is not authoritative Section 6.1.1. If the authentication service is not authoritative
for the identity in question, it SHOULD process and forward the for the identity in question, it SHOULD process and forward the
request normally, but it MUST NOT follow the steps below to add an request normally unless the local policy is to block such requests.
Identity header. The authentication service MUST NOT follow the steps below to add an
Identity header corresponding to an identity for which the
authentication service is not authoritative.
Step 2: Step 2:
The authentication service MUST then determine whether or not the The authentication service MUST then determine whether or not the
sender of the request is authorized to claim the identity given in sender of the request is authorized to claim the identity given in
the identity field. In order to do so, the authentication service the identity field. In order to do so, the authentication service
MUST authenticate the sender of the message. Some possible ways in MUST authenticate the sender of the message. Some possible ways in
which this authentication might be performed include: which this authentication might be performed include:
If the authentication service is instantiated by a SIP If the authentication service is instantiated by a SIP
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the authentication scheme used for registration in its domain the authentication scheme used for registration in its domain
(e.g., Digest authentication). (e.g., Digest authentication).
If the authentication service is instantiated by a SIP user agent, If the authentication service is instantiated by a SIP user agent,
a user agent may authenticate its own user through any system- a user agent may authenticate its own user through any system-
specific means, perhaps simply by virtue of having physical access specific means, perhaps simply by virtue of having physical access
to the user agent. to the user agent.
Authorization of the use of a particular username or telephone number Authorization of the use of a particular username or telephone number
in the user part of the From header field is a matter of local policy in the user part of the From header field is a matter of local policy
for the authentication service, see Section 5.1 for more information. for the authentication service; see Section 5.1 for more information.
Note that this check is performed only on the addr-spec in the Note that this check is performed only on the addr-spec in the
identity field (e.g., the URI of the sender, like identity field (e.g., the URI of the sender, like
'sip:alice@atlanta.example.com'); it does not convert the display- 'sip:alice@atlanta.example.com'); it does not convert the display-
name portion of the From header field (e.g., 'Alice Atlanta'). For name portion of the From header field (e.g., 'Alice Atlanta'). For
more information, see Section 11.6. more information, see Section 11.6.
Step 3: Step 3:
An authentication service MUST add a Date header field to SIP An authentication service MUST add a Date header field to SIP
requests if one is not already present. The authentication service requests that do not have one. The authentication service MUST
MUST ensure that any preexisting Date header in the request is ensure that any preexisting Date header in the request is accurate.
accurate. Local policy can dictate precisely how accurate the Date Local policy can dictate precisely how accurate the Date must be; a
must be; a RECOMMENDED maximum discrepancy of sixty seconds will RECOMMENDED maximum discrepancy of sixty seconds will ensure that the
ensure that the request is unlikely to upset any verifiers. If the request is unlikely to upset any verifiers. If the Date header
Date header contains a time different by more than one minute from contains a time different by more than one minute from the current
the current time noted by the authentication service, the time noted by the authentication service, the authentication service
authentication service SHOULD reject the request. This behavior is SHOULD reject the request. This behavior is not mandatory because a
not mandatory because a user agent client (UAC) could only exploit user agent client (UAC) could only exploit the Date header in order
the Date header in order to cause a request to fail verification; the to cause a request to fail verification; the Identity header is not
Identity header is not intended to provide a source of non- intended to provide a source of non-repudiation or a perfect record
repudiation or a perfect record of when messages are processed. of when messages are processed. Finally, the authentication service
Finally, the authentication service MUST verify that the Date header MUST verify that both the Date header and the current time fall
falls within the validity period of its credential. within the validity period of its credential.
See Section 11 for information on how the Date header field assists See Section 11 for information on how the Date header field assists
verifiers. verifiers.
Step 4: Step 4:
Subsequently, the authentication service MUST form the identity Subsequently, the authentication service MUST form a PASSporT object
signature and add an Identity header to the request containing this and add a corresponding an Identity header to the request containing
signature. For baseline Identity headers (without a "spec" this signature. For baseline PASSporT objects headers (without an
parameter), this follows the procedures in Section 7; if the Identity header "type" parameter), this follows the procedures in
authentication service is using an alternative "spec", it MUST add an Section 7; if the authentication service is using an alternative
appropriate "spec" parameter and follow the procedures associated "type", it MUST add an appropriate "type" parameter and follow the
with it (see Section 8). After the Identity header has been added to procedures associated with it (see Section 8). After the Identity
the request, the authentication service MUST also add a "info" header has been added to the request, the authentication service MUST
parameter to the Identity header. The "info" parameter contains a also add a "info" parameter to the Identity header. The "info"
URI from which the authentication service's credential can be parameter contains a URI from which the authentication service's
acquired; see Section 5.3 for more on credential acquisition. credential can be acquired; see Section 5.3 for more on credential
acquisition.
Finally, the authentication service MUST forward the message Finally, the authentication service MUST forward the message
normally. normally.
4.2. Verifier Behavior 4.2. Verifier Behavior
This document specifies a logical role for SIP entities called a This document specifies a logical role for SIP entities called a
verification service, or verifier. When a verifier receives a SIP verification service, or verifier. When a verifier receives a SIP
message containing one or more Identity headers, it inspects the message containing one or more Identity headers, it inspects the
signature to verify the identity of the sender of the message. The signature to verify the identity of the sender of the message. The
results of a verification are provided as input to an authorization results of a verification are provided as input to an authorization
process that is outside the scope of this document. process that is outside the scope of this document.
A SIP request may contain zero, one, or more Identity headers. A A SIP request may contain zero, one, or more Identity headers. A
verification service performs the procedures below on each Identity verification service performs the procedures below on each Identity
header that appears in a request. If the verifier does not support header that appears in a request. If the verifier does not support
an Identity header present in a request due to the presence of an an Identity header present in a request due to the presence of an
unsupported "spec" parameter, or if no Identity header is present, unsupported "type" parameter, or if no Identity header is present,
and the presence of an Identity header is required by local policy and the presence of an Identity header is required by local policy
(for example, based on a per-sending-domain policy, or a per-sending- (for example, based on a per-sending-domain policy, or a per-sending-
user policy), then a 428 'Use Identity Header' response MUST be sent user policy), then a 428 'Use Identity Header' response MUST be sent
in the backwards direction. in the backwards direction.
In order to verify the identity of the sender of a message, an entity In order to verify the identity of the sender of a message, an entity
acting as a verifier MUST perform the following steps, in the order acting as a verifier MUST perform the following steps, in the order
here specified. here specified.
Step 1: Step 1:
The verifier MUST inspect any optional "spec" parameter appearing the The verifier MUST inspect any optional "type" parameter appearing the
Identity request. If no "spec" parameter is present, then the Identity request. If no "type" parameter is present, then the
verifier proceeds normally below. If a "spec" parameter value is verifier proceeds normally below. If a "type" parameter value is
present, and the verifier does not support it, it MUST ignore the present, and the verifier does not support it, it MUST ignore the
Identity header. If a supported "spec" parameter value is present, Identity header. If a supported "type" parameter value is present,
the verifier follows the procedures below, including the variations the verifier follows the procedures below, including the variations
described in Step 5. described in Step 5.
Step 2: Step 2:
In order to determine whether the signature for the identity field In order to determine whether the signature for the identity field
should be over the entire identity field URI or just a canonicalized should be over the entire identity field URI or just a canonicalized
telephone number, the verification service MUST follow the telephone number, the verification service MUST follow the
canonicalization process described in Section 6.1.1. That section canonicalization process described in Section 6.1.1. That section
also describes the procedures the verification service MUST follow to also describes the procedures the verification service MUST follow to
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domains, the verifier MUST follow the process described in domains, the verifier MUST follow the process described in
Section 6.2 to determine if the signer is authoritative for the Section 6.2 to determine if the signer is authoritative for the
identity field. identity field.
Step 3: Step 3:
The verifier must first ensure that it possesses the proper keying The verifier must first ensure that it possesses the proper keying
material to validate the signature in the Identity header field, material to validate the signature in the Identity header field,
which usually involves dereferencing a URI in the "info" parameter of which usually involves dereferencing a URI in the "info" parameter of
the Identity header. See Section 5.2 for more information on these the Identity header. See Section 5.2 for more information on these
procedures. procedures. If the verifier does not suport the credential described
in the "info" parameter, it MUST return a 437 "Unsupported
Certificate" response.
Step 4: Step 4:
The verifier MUST furthermore ensure that the value of the Date The verifier MUST furthermore ensure that the value of the Date
header meets local policy for freshness (usually, within sixty header meets local policy for freshness (usually, within sixty
seconds) and that it falls within the validity period of the seconds) and that it falls within the validity period of the
credential used to sign the Identity header. For more on the attacks credential used to sign the Identity header. For more on the attacks
this prevents, see Section 11.1. this prevents, see Section 11.1.
Step 5: Step 5:
The verifier MUST validate the signature in the Identity header The verifier MUST validate the signature in the Identity header field
field. For baseline Identity headers (with no "spec" parameter) the over the PASSporT object. For baseline PASSporT objects (with no
verifier MUST follow the procedures for generating the signature over Identity header "type" parameter) the verifier MUST follow the
hashed JSON objects described in Section 7. If a "spec" parameter is procedures for generating the signature over a PASSporT object
present, the verifier follows the procedures for that "spec" (see described in Section 7. If a "type" parameter is present, the
Section 8). If a verifier determines that the signature on the verifier follows the procedures for that "type" (see Section 8). If
message does not correspond to the reconstructed digest-string, then a verifier determines that the signature on the message does not
a 438 'Invalid Identity Header' response MUST be returned. correspond to the reconstructed signed-identity-digest, then a 438
'Invalid Identity Header' response MUST be returned.
The handling of the message after the verification process depends on The handling of the message after the verification process depends on
how the implementation service is implemented, and on local policy. how the implementation service is implemented and on local policy.
This specification does not propose any authorization policy for user This specification does not propose any authorization policy for user
agents or proxy servers to follow based on the presence of a valid agents or proxy servers to follow based on the presence of a valid
Identity header, the presence of an invalid Identity header, or the Identity header, the presence of an invalid Identity header, or the
absence of an Identity header, but it is anticipated that local absence of an Identity header, but it is anticipated that local
policies could involve making different forwarding decisions in policies could involve making different forwarding decisions in
intermediary implementations, or changing how the user is alerted, or intermediary implementations, or changing how the user is alerted, or
how identity is rendered, in user agent implementations. how identity is rendered, in user agent implementations.
5. Credentials 5. Credentials
skipping to change at page 12, line 44 skipping to change at page 12, line 51
cannot be dereferenced, then a 436 'Bad Identity-Info' response MUST cannot be dereferenced, then a 436 'Bad Identity-Info' response MUST
be returned. be returned.
This specification does not propose any particular policy for a This specification does not propose any particular policy for a
verification service to determine whether or not the holder of a verification service to determine whether or not the holder of a
credential is the appropriate party to sign for a given SIP identity. credential is the appropriate party to sign for a given SIP identity.
Guidance on this is deferred to the credential mechanism Guidance on this is deferred to the credential mechanism
specifications, which must meet the requirements in Section 5.4. specifications, which must meet the requirements in Section 5.4.
Verification service implementations supporting this specification Verification service implementations supporting this specification
SHOULD have some means of retaining credentials (in accordance with may wish to have some means of retaining credentials (in accordance
normal practices for credential lifetimes and revocation) in order to with normal practices for credential lifetimes and revocation) in
prevent themselves from needlessly downloading the same credential order to prevent themselves from needlessly downloading the same
every time a request from the same identity is received. Credentials credential every time a request from the same identity is received.
cached in this manner may be indexed in accordance with local policy: Credentials cached in this manner may be indexed in accordance with
for example, by their scope, or the URI given in the "info" parameter local policy: for example, by their scope, or the URI given in the
value. Further consideration of how to cache credentials is deferred "info" parameter value. Further consideration of how to cache
to the credential mechanism specifications. credentials is deferred to the credential mechanism specifications.
5.3. Handling 'info' parameter URIs 5.3. Handling 'info' parameter URIs
An "info" parameter MUST contain a URI which dereferences to a An "info" parameter MUST contain a URI which dereferences to a
resource that contains the public key components of the credential resource that contains the public key components of the credential
used by the authentication service to sign a request. It is used by the authentication service to sign a request. It is
essential that a URI in the "info parameter" be dereferencable by any essential that a URI in the "info parameter" be dereferencable by any
entity that could plausibly receive the request. For common cases, entity that could plausibly receive the request. For common cases,
this means that the URI must be dereferencable by any entity on the this means that the URI must be dereferencable by any entity on the
public Internet. In constrained deployment environments, a service public Internet. In constrained deployment environments, a service
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range. Either would be eligible to sign a SIP request for the number range. Either would be eligible to sign a SIP request for the number
in question. Verification services however need a means to in question. Verification services however need a means to
differentiate which one performed the signature. The "info" differentiate which one performed the signature. The "info"
parameter performs that function. parameter performs that function.
If the optional "canon" parameter is present, it contains the bae64 If the optional "canon" parameter is present, it contains the bae64
encoded result of JSON object construction process performed by the encoded result of JSON object construction process performed by the
authentication service (see Section 6.1.1), including the authentication service (see Section 6.1.1), including the
canonicalization processes applied to the identity in the identity canonicalization processes applied to the identity in the identity
fields of the sender and intended recipient. The "canon" is provided fields of the sender and intended recipient. The "canon" is provided
purely informationally as an optimization for the verification purely as an optimization for the verification service. The
service. The verification service MAY compute its own verification service MAY compute its own canonicalization of the
canonicalization of the numbers and compare them to the values in the numbers and compare them to the values in the "canon" parameter
"canon" parameter before performing any cryptographic functions in before performing any cryptographic functions in order to ascertain
order to ascertain whether or not the two ends agree on the canonical whether or not the two ends agree on the canonical number form.
number form.
5.4. Credential System Requirements 5.4. Credential System Requirements
This document makes no recommendation for the use of any specific This document makes no recommendation for the use of any specific
credential system. Today, there are two primary credential systems credential system. Today, there are two primary credential systems
in place for proving ownership of domain names: certificates (e.g., in place for proving ownership of domain names: certificates (e.g.,
X.509 v3, see [RFC5280]) and the domain name system itself (e.g., X.509 v3, see [RFC5280]) and the domain name system itself (e.g.,
DANE, see [RFC6698]). It is envisioned that either could be used in DANE, see [RFC6698]). It is envisioned that either could be used in
the SIP identity context: an "info" parameter could for example give the SIP identity context: an "info" parameter could for example give
an HTTP URL of the form 'application/pkix-cert' pointing to a an HTTP URL of the form 'application/pkix-cert' pointing to a
skipping to change at page 14, line 24 skipping to change at page 14, line 30
which URIs schemes the credential will use in the "info" which URIs schemes the credential will use in the "info"
parameter, and any special procedures required to dereference the parameter, and any special procedures required to dereference the
URIs URIs
how the verifier can learn the scope of the credential how the verifier can learn the scope of the credential
any special procedures required to extract keying material from any special procedures required to extract keying material from
the resources designated by the URI the resources designated by the URI
any algorithms that would appear in the Identity-Info "alg" any algorithms that would appear in the Identity-Info "alg"
parameter other than 'RS256.' Note that per the IANA parameter other than 'RS256.' Note that the policy for adding
Considerations of RFC 4474, new algorithms can only be specified algorithms to this registry requires Standards Action
by Standards Action
SIP entities cannot reliably predict where SIP requests will SIP entities cannot reliably predict where SIP requests will
terminate. When choosing a credential scheme for deployments of this terminate. When choosing a credential scheme for deployments of this
specification, it is therefore essential that the trust anchor(s) for specification, it is therefore essential that the trust anchor(s) for
credentials be widely trusted, or that deployments restrict the use credentials be widely trusted, or that deployments restrict the use
of this mechanism to environments where the reliance on particular of this mechanism to environments where the reliance on particular
trust anchors is assured by business arrangements or similar trust anchors is assured by business arrangements or similar
constraints. constraints.
Note that credential systems must address key lifecycle management Note that credential systems must address key lifecycle management
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service to ascertain in this case whether the URI contains a service to ascertain in this case whether the URI contains a
telephone number or not. telephone number or not.
6.1.1. Canonicalization Procedures 6.1.1. Canonicalization Procedures
In order to determine whether or not the user portion of a SIP URI is In order to determine whether or not the user portion of a SIP URI is
a telephone number, authentication services and verification services a telephone number, authentication services and verification services
must perform the following canonicalization procedure on any SIP URI must perform the following canonicalization procedure on any SIP URI
they inspect which contains a wholly numeric user part. Note that they inspect which contains a wholly numeric user part. Note that
the same procedures are followed for creating the canonical form of the same procedures are followed for creating the canonical form of
URIs found in both the From and To header field values. URIs found in both the From and To header field values; this section
also describes procedures for extracting the URI containing the
telephone number from the P-Asserted-Identity header field value for
environments where that is applicable.
In some networks, the P-Asserted-Identity header field value is used
in lieu of the From header field to convey the telephone number of
the sender of a request; while it is not envisioned that most of
those networks would or should make use of the Identity mechanism
described in this specification, where they do, local policy might
therefore dictate that the canonical string derive from the P-
Asserted-Identity header field rather than the From. In any case
where local policy canonicalizes the number into a form different
from how it appears in the From header field, the use of the "canon"
parameter by authentication services is RECOMMENDED, but because
"canon" itself could then divulge information about users or
networks, implementers should be mindful of the guidelines in
Section 10.
First, implementations must assess if the user-portion of the URI First, implementations must assess if the user-portion of the URI
constitutes a telephone number. In some environments, numbers constitutes a telephone number. In some environments, numbers
will be explicitly labeled by the use of TEL URIs or the will be explicitly labeled by the use of TEL URIs or the
'user=phone' parameter, or implicitly by the presence of the '+' 'user=phone' parameter, or implicitly by the presence of the '+'
indicator at the start of the user-portion. Absent these indicator at the start of the user-portion. Absent these
indications, if there are numbers present in the user-portion, indications, if there are numbers present in the user-portion,
implementations may also detect that the user-portion of the URI implementations may also detect that the user-portion of the URI
contains a telephone number by determining whether or not those contains a telephone number by determining whether or not those
numbers would be dialable or routable in the local environment -- numbers would be dialable or routable in the local environment --
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separators. separators.
Next, an implementation must assess if the number string is a Next, an implementation must assess if the number string is a
valid, globally-routable number with a leading country code. If valid, globally-routable number with a leading country code. If
not, implementations SHOULD convert the number into E.164 format, not, implementations SHOULD convert the number into E.164 format,
adding a country code if necessary; this may involve transforming adding a country code if necessary; this may involve transforming
the number from a dial string (see [RFC3966]), removing any the number from a dial string (see [RFC3966]), removing any
national or international dialing prefixes or performing similar national or international dialing prefixes or performing similar
procedures. It is only in the case that an implementation cannot procedures. It is only in the case that an implementation cannot
determine how to convert the number to a globally-routable format determine how to convert the number to a globally-routable format
that this step may be skipped. that this step may be skipped. This will be the case, for
example, for nationally-specific service numbers (e.g. 911, 112);
however, the routing procedures associated with those numbers will
likely make sure that the verification service understands the
context of their use.
In some cases, further transformations MAY be made in accordance Oher transformations during canonicalization MAY be made in
with specific policies used within the local domain. For example, accordance with specific policies used within a local domain. For
one domain may only use local number formatting and need to example, one domain may only use local number formatting and need
convert all To/From user portions to E.164 by prepending country- to convert all To/From user portions to E.164 by prepending
code and region code digits; another domain might prefix usernames country-code and region code digits; another domain might prefix
with trunk-routing codes and need to remove the prefix. Also, in usernames with trunk-routing codes and need to remove the prefix.
some networks, the P-Asserted-Identity header field value is used This specification cannot anticipate all of the potential
in lieu of the From header field to convey the telephone number of transformations that might be useful.
the sender of a request; while it is not envisioned that most of
those networks would or should make use of the Identity mechanism
described in this specification, where they do, local policy might
therefore dictate that the canonical string derive from the P-
Asserted-Identity header field rather than the From. In any case
where local policy canonicalizes the number into a form different
from how it appears in the From header field, the use of the
"canon" parameter by authentication services is RECOMMENDED, but
because "canon" itself could then divulge information about users
or networks, implementers should be mindful of the guidelines in
Section 10.
The resulting canonical number string will be used as input to the The resulting canonical number string will be used as input to the
hash calculation during signing and verifying processes. hash calculation during signing and verifying processes.
The ABNF of this number string is: The ABNF of this number string is:
tn-spec = [ "#" / "*" ] 1*DIGIT tn-spec = [ "#" / "*" ] 1*DIGIT
If the result of this procedure forms a complete telephone number, If the result of this procedure forms a complete telephone number,
that number is used for the purpose of creating and signing the that number is used for the purpose of creating and signing the
digest-string by both the authentication service and verification signed-identity-string by both the authentication service and
service. Practically, entities that perform the authentication verification service. Practically, entities that perform the
service role will sometimes alter the telephone numbers that appear authentication service role will sometimes alter the telephone
in the To and From header field values, converting them to this numbers that appear in the To and From header field values,
format (though note this is not a function that [RFC3261] permits converting them to this format (though note this is not a function
proxy servers to perform). The result of the canonicalization that [RFC3261] permits proxy servers to perform). The result of the
process of the From header field value may also be recorded through canonicalization process of the From header field value may also be
the use of the "canon" parameter of the Identity(see Section 7). If recorded through the use of the "canon" parameter of the Identity(see
the result of the canonicalization of the From header field value Section 7). If the result of the canonicalization of the From header
does not form a complete telephone number, the authentication service field value does not form a complete telephone number, the
and verification service should treat the entire URI as a SIP URI, authentication service and verification service should treat the
and apply a domain signature per the procedures in Section 6.2. entire URI as a SIP URI, and apply a domain signature per the
procedures in Section 6.2.
6.2. Domain Names 6.2. Domain Names
When a verifier processes a request containing an Identity-Info When a verifier processes a request containing an Identity-Info
header with a domain signature, it must compare the domain portion of header with a domain signature, it must compare the domain portion of
the URI in the From header field of the request with the domain name the URI in the From header field of the request with the domain name
that is the subject of the credential acquired from the "info" that is the subject of the credential acquired from the "info"
parameter. While it might seem that this should be a straightforward parameter. While it might seem that this should be a straightforward
process, it is complicated by two deployment realities. In the first process, it is complicated by two deployment realities. In the first
place, credentials have varying ways of describing their subjects, place, credentials have varying ways of describing their subjects,
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identity and the signing credential by following the procedures identity and the signing credential by following the procedures
defined in RFC 2818 [RFC2818], Section 3.1. While RFC 2818 [RFC2818] defined in RFC 2818 [RFC2818], Section 3.1. While RFC 2818 [RFC2818]
deals with the use of HTTP in TLS and is specific to certificates, deals with the use of HTTP in TLS and is specific to certificates,
the procedures described are applicable to verifying identity if one the procedures described are applicable to verifying identity if one
substitutes the "hostname of the server" in HTTP for the domain substitutes the "hostname of the server" in HTTP for the domain
portion of the user's identity in the From header field of a SIP portion of the user's identity in the From header field of a SIP
request with an Identity header. request with an Identity header.
7. Header Syntax 7. Header Syntax
Baseline RFC4474 defined the Identity and Identity-Info headers. The Identity and Identity-Info headers that were previously defined
This document deprecates the Identity-Info header, collapsing its in RFC4474 are deprecated. This document collapses the grammar of
grammar into the Identity header. Note that unlike baseline RFC4474, the Identity-Info into the Identity header via the "info" parameter.
the Identity header is now allowed to appear more than one time in a Note that unlike the prior specification in RFC4474, the Identity
SIP request. The revised grammar for the Identity header is header is now allowed to appear more than one time in a SIP request.
(following the ABNF [RFC4234] in RFC 3261 [RFC3261]): The revised grammar for the Identity header is (following the ABNF
[RFC4234] in RFC 3261 [RFC3261]):
Identity = "Identity" HCOLON signed-identity-digest SEMI ident-info *( SEMI ident-info-params ) Identity = "Identity" HCOLON signed-identity-digest SEMI ident-info *( SEMI ident-info-params )
signed-identity-digest = LDQUOT *base64-char RDQUOT signed-identity-digest = LDQUOT *base64-char RDQUOT
ident-info = LAQUOT absoluteURI RAQUOT ident-info = "info" EQUAL ident-info-uri
ident-info-params = ident-info-alg / ident-spec / canonical-str ident-info-uri = LAQUOT absoluteURI RAQUOT
ident-info-params = ident-info-alg / ident-type / canonical-str / ident-info-extension
ident-info-alg = "alg" EQUAL token ident-info-alg = "alg" EQUAL token
ident-spec = "spec" EQUAL token ident-type = "type" EQUAL token
canonical-str = "canon" EQUAL *base64-char canonical-str = "canon" EQUAL *base64-char
ident-info-extension = generic-param ident-info-extension = generic-param
base64-char = ALPHA / DIGIT / "/" / "+" base64-char = ALPHA / DIGIT / "/" / "+"
In addition to the parameters of Identity-Info in RFC4474, this In addition to "info" parameter and the "alg" parameter defined in
specification includes the optional "canon" and "spec" parameters. RFC44744, this specification includes the optional "canon" and "type"
Note that in RFC4474, the signed-identity-digest was given as quoted parameters. Note that in RFC4474, the signed-identity-digest (see
32LHEX, whereas here it is given as a quoted sequence of base64-char. ABNF above) was given as quoted 32LHEX, whereas here it is given as a
quoted sequence of base64-char.
The 'absoluteURI' portion of ident-info MUST contain a URI; see The 'absoluteURI' portion of ident-info-uri MUST contain a URI; see
Section 5.3 for more on choosing how to advertise credentials through Section 5.3 for more on choosing how to advertise credentials through
this parameter. this parameter.
The signed-identity-digest is a signed hash of a pair of JSON objects The signed-identity-digest is a signed hash of a [ietf-stir-passport]
generated from certain components of a SIP request. This first object, which is a pair of JSON objects generated from certain
object contains header information, and the second contains claims, components of a SIP request. This first object contains header
following the conventions of JWT [RFC7519]. Once these two JSON information, and the second contains claims, following the
objects have been generated, they will be stripped of all unquoted conventions of JWT [RFC7519]. Once these two JSON objects have been
whitespace and linefeeds, and each will be separately base64 encoded, generated, they will be encoded per the procedures of [ietf-stir-
hashed with a SHA-256 hash and then concatenated, header then claims, passport], then hashed with a SHA-256 hash and then concatenated,
into a string separated by a single "." per the conventions of header then claims, into a string separated by a single "." per the
baseline JWT. conventions of baseline PASSporT.
To create the header JSON object used in the construction of the To create the PASSporT object used in the construction of the signed-
signed-identity-digest of the Identity header, the following elements identity-digest of the Identity header, the following elements of a
of a SIP message MUST be placed in a comma-separated JSON object, in SIP message MUST be placed in a first comma-separated JSON object, in
order: order:
First, the JSON key "typ" followed by a colon and then the quoted First, the JSON key "typ" followed by a colon and then the quoted
string "JWT". string "PASSporT".
Second, the JSON key "alg" followed by a colon and then the quoted Second, the JSON key "alg" followed by a colon and then the quoted
value of the optional "alg" parameter in the Identity header. value of the optional "alg" parameter in the Identity header.
Note if the "alg" parameter is absent it is assumed to the value Note if the "alg" parameter is absent, the default value is
"RS256". "RS256".
Third, the JSON key "x5u" followed by a colon and then the quoted Third, the JSON key "x5u" followed by a colon and then the quoted
value of the URI in the "info" parameter. value of the URI in the "info" parameter.
Fourth, optionally the JSON key "spec" followed by a colon and Fourth, optionally the JSON key "type" followed by a colon and
then the quoted value of the "spec" parameter of the Identity then the quoted value of the "type" parameter of the Identity
header. If the "spec" parameter is absent from the header, the header. If the "type" parameter is absent from the header, the
"spec" key will not appear in the JSON heaer object. "type" key will not appear in the JSON heaer object.
For example: For example:
{ "typ":"JWT", { "typ":"PASSporT",
"alg":"RS256" "alg":"RS256"
"x5u":"https://www.example.com/cert.pkx" } "x5u":"https://www.example.com/cert.pkx" }
To create the claims JSON object used in the construction of the To create the PASSporT claims JSON object used in the construction of
signed-identity-digest, the following elements of a SIP message MUST the signed-identity-digest, the following elements of a SIP message
be placed in a comma-separated JSON object, in order: MUST be placed in a comma-separated JSON object, in order:
First, the JSON key "orig" followed by a colon and then the quoted First, the JSON key "orig" followed by a colon and then the quoted
identity. If the user part of the AoR in the From header field of identity. If the user part of the AoR in the From header field of
the request contains a telephone number, then the canonicalization the request contains a telephone number, then the canonicalization
of that number goes into the first slot (see Section 6.1.1). of that number goes into the first slot (see Section 6.1.1).
Otherwise, the first slot contains the AoR of the UA sending the Otherwise, the first slot contains the AoR of the UA sending the
message as taken from addr-spec of the From header field. message as taken from addr-spec of the From header field.
Second, the JSON key "term" followed by a colon and the quoted Second, the JSON key "term" followed by a colon and the quoted
target. If the user part of the AoR in the To header field of the target. If the user part of the AoR in the To header field of the
request contains a telephone number, then the canonicalization of request contains a telephone number, then the canonicalization of
that number goes into the second slot (again, see Section 6.1.1). that number goes into the second slot (again, see Section 6.1.1).
Otherwise, the second slot contains the addr-spec component of the Otherwise, the second slot contains the addr-spec component of the
To header field, which is the AoR to which the request is being To header field, which is the AoR to which the request is being
sent. sent.
Third, the JSON key "iat" followed by a colon and then a quoted Third, the JSON key "iat" followed by a colon and then a quoted
encoding of the value of the SIP Date header field as a JSON encoding of the value of the SIP Date header field as a JSON
NumericDate (as UNIX time, per [RFC7519] Section 2)/. NumericDate (as UNIX time, per [RFC7519] Section 2).
Fourth, if the request contains an SDP message body, and if that Fourth, if the request contains an SDP message body, and if that
SDP contains one or more "a=fingerprint" attributes, then the JSON SDP contains one or more "a=fingerprint" attributes, then the JSON
key "mky" followed by a colon and then the quoted value(s) of the key "mky" followed by a colon and then the quoted value(s) of the
fingerprint attributes (if they differ). Each attribute value fingerprint attributes (if they differ). Each attribute value
consists of all characters following the colon after consists of all characters following the colon after
"a=fingerprint" including the algorithm description and "a=fingerprint" including the algorithm description and
hexadecimal key representation, any whitespace, carriage returns, hexadecimal key representation, any whitespace, carriage returns,
and "/" line break indicators. If multiple non-identical and "/" line break indicators. If multiple non-identical
"a=fingerprint" attributes appear in an SDP body, then all non- "a=fingerprint" attributes appear in an SDP body, then all non-
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then no JSON "mky" key is added to the object. then no JSON "mky" key is added to the object.
For example: For example:
{ "orig":"12155551212", { "orig":"12155551212",
"term":"12155551213", "term":"12155551213",
"iat": "1443208345", "iat": "1443208345",
For more information on the security properties of these headers, and For more information on the security properties of these headers, and
why their inclusion mitigates replay attacks, see Section 11 and why their inclusion mitigates replay attacks, see Section 11 and
[RFC3893]. The precise formulation of this digest-string is, [RFC3893].
therefore (following the ABNF[RFC4234] in RFC 3261 [RFC3261]):
After these two JSON objects, the header and the claims, have been After these two JSON objects, the header and the claims, have been
constructed, they must be hashed and signed. The hashing and signing constructed as a PASSporT object, they must be hashed and signed;
algorithm is specified by the 'alg' parameter of the Identity header. this then becomes the signed-identity-string. The hashing and
This document defines only one value for the 'alg' parameter: signing algorithm is specified by the 'alg' parameter of the Identity
'RS256', as defined in [RFC7519], which connotes a SHA-256 hash header. This document defines only one value for the 'alg'
followed by a RSASSA-PKCS1-v1_5 signature. Any further values MUST parameter: 'RS256', as defined in [RFC7519], which connotes a SHA-256
be defined in a Standards Track RFC, see Section 12.2 for more hash followed by a RSASSA-PKCS1-v1_5 signature. All implementations
information. All implementations of this specification MUST support of this specification MUST support 'RS256'. Any further 'alg' values
'RS256'. The result of the hash and signing of the two concatenated MUST be defined in a Standards Track RFC, see Section 12.2 for more
JSON objects is placed in the Identity header field. information. The result of the hash and signing of the two
concatenated JSON objects is placed in the Identity header field.
For example: For example:
Identity: "sv5CTo05KqpSmtHt3dcEiO/1CWTSZtnG3iV+1nmurLXV/HmtyNS7Ltrg9dlxkWzo Identity: "sv5CTo05KqpSmtHt3dcEiO/1CWTSZtnG3iV+1nmurLXV/HmtyNS7Ltrg9dlxkWzo
eU7d7OV8HweTTDobV3itTmgPwCFjaEmMyEI3d7SyN21yNDo2ER/Ovgtw0Lu5csIp eU7d7OV8HweTTDobV3itTmgPwCFjaEmMyEI3d7SyN21yNDo2ER/Ovgtw0Lu5csIp
pPqOg1uXndzHbG7mR6Rl9BnUhHufVRbp51Mn3w0gfUs="; \ pPqOg1uXndzHbG7mR6Rl9BnUhHufVRbp51Mn3w0gfUs="; \
info=<https://biloxi.example.org/biloxi.cer>;alg=RS256 info=<https://biloxi.example.org/biloxi.cer>;alg=RS256
In a departure from JWT practice, the base64 encoded version of the In a departure from JWT practice, the base64 encoded version of the
JSON objects is not included in the Identity header: only the JSON objects is not included in the Identity header: only the
signature component of the JWT is. Optionally, as an debugging signature component of the PASSporT is. Optionally, as an debugging
measure or optimization, the base64 encoded concatenation of the JSON measure or optimization, the base64 encoded concatenation of the JSON
header and claims may be included as the value of a "canon" parameter header and claims may be included as the value of a "canon" parameter
of the Identity header. Note that this may be lengthy string. of the Identity header. Note that this may be lengthy string.
8. Extensibility 8. Extensibility
As future requirements may warrant increasing the scope of the As future requirements may warrant increasing the scope of the
Identity mechanism, this specification defines an optional "spec" Identity mechanism, this specification defines an optional "type"
parameter of the Identity header. The "spec" parameter value MUST parameter of the Identity header. The "type" parameter value MUST
consist of a token containing an extension specification, which consist of a token containing an extension specification, which
denotes an alternative set of signed claims. denotes an alternative set of signed claims per the type
extensibility mechanism specified in [ietf-stir-passport]
Future specifications that define extensions to the Identity An authentication service cannot assume that verifiers will
mechanism MUST explicitly designate what claims they include, the understand any given extension. Verifiers that do support an
order in which they will appear, and any further information extension may then trigger appropriate application-level behavior in
necessary to implement the extension at the authentication service the presence of an extension; authors of extensions should provide
and the verification service. All extensions MUST incorporate the appropriate extension-specific guidance to application developers on
baseline JWT elements specified in Section 7; claims may only be this point.
appended to the claims object specified in there, they can never be
subtracted re-ordered. Specifying new claims follows the baseline
JWT procedures ([RFC7519] Section 10.1). Note that per the verifier
behavior in Section 4.2, understanding a "spec" extension is always
optional for compliance with this specification (though future
specifications or profiles for deployment environments may make other
"spec" values mandatory). An authentication service cannot assume
that verifiers will understand any given extension. Verifiers that
do support an extension may then trigger appropriate application-
level behavior in the presence of an extension; authors of extensions
should provide appropriate extension-specific guidance to application
developers on this point.
If any claim in an extension contains a JSON value that does not If any claim in an extension contains a JSON value that does not
correspond to any field of the SIP request, but then the optional correspond to any field of the SIP request, but then the optional
"canon" parameter MUST be used for the Identity header containing "canon" parameter MUST be used for the Identity header containing
that extension. that extension.
The IANA procedure for registering new "spec" parameters is given in 9. Gatewaying to PASSporT for non-SIP Transit
Section 12.3; no values are defined in this document. If no "spec"
value appears in an Identity header, then the signature covers the
baseline claims specified in Section 7.
Purely as an example, were a "calling name" extension to be
registered, it might choose the spec name "cna". Implementations
supporting "cna" could, for example, define a new JWT field called
"cna" with the semantics that it contains a value authorized by the
signer a display-name component for the From or P-Asserted-Identity
header field value.
9. Gatewaying to JWT for non-SIP Transit
As defined in this specification, the signature in the Identity As defined in this specification, the signature in the Identity
header is equivalent to the signature that would appear in a JWT header is equivalent to the signature that would appear in a PASSporT
token. This is so that a valid JWT can be generated based on a SIP token. This is so that a valid PASSporT can be generated based on a
request containing an Identity header. This JWT could then be SIP request containing an Identity header. This PASSporT could then
transported in alternate protocols, stored in a repository and later be transported in alternate protocols, stored in a repository and
accessed, or similarly used outside the context of establishing an later accessed, or similarly used outside the context of establishing
end-to-end SIP session. an end-to-end SIP session.
Because the base64 encoding the JSON objects containing headers and Because the base64 encoding the JSON objects containing headers and
claims can be quite, and because the information it contains is claims can be quite long, and because the information it contains is
necessarily redundant with information in the header field values of necessarily redundant with information in the header field values of
the SIP request itself, SIP does not require implementations to carry the SIP request itself, SIP does not require implementations to carry
the base64 encodings of those objects. The optional "canon" the base64 encodings of those objects. The optional "canon"
parameter of the Identity-Info, if present, contains the encoded parameter of the Identity-Info, if present, contains the encoded
objects used to generate the hash and signature (see Section 7), but objects used to generate the hash and signature (see Section 7), but
if the "canon" parameter is not present, the contents of the objects if the "canon" parameter is not present, the contents of the objects
can be regenerated by constructing the object anew from the SIP can be regenerated by constructing the object anew from the SIP
header fields. header fields received.
Alternative transports for this JWT and their requirements are left Alternative transports for this PASSporT and their requirements are
to future specifications. left to future specifications.
10. Privacy Considerations 10. Privacy Considerations
The purpose of this mechanism is to provide a strong identification The purpose of this mechanism is to provide a strong identification
of the originator of a SIP request, specifically a cryptographic of the originator of a SIP request, specifically a cryptographic
assurance that the URI given in the From header field value can assurance that a cryptographically-assured authority asserts the
legitimately be claimed by the originator. This URI may contain a orginator can claim the URI given in the From header field. This URI
variety of personally identifying information, including the name of may contain a variety of personally identifying information,
a human being, their place of work or service provider, and possibly including the name of a human being, their place of work or service
further details. The intrinsic privacy risks associated with that provider, and possibly further details. The intrinsic privacy risks
URI are, however, no different from those of baseline SIP. Per the associated with that URI are, however, no different from those of
guidance in [RFC6973], implementors should make users aware of the baseline SIP. Per the guidance in [RFC6973], implementors should
privacy trade-off of providing secure identity. make users aware of the privacy trade-off of providing secure
identity.
The identity mechanism presented in this document is compatible with The identity mechanism presented in this document is compatible with
the standard SIP practices for privacy described in [RFC3323]. A SIP the standard SIP practices for privacy described in [RFC3323]. A SIP
proxy server can act both as a privacy service and as an proxy server can act both as a privacy service and as an
authentication service. Since a user agent can provide any From authentication service. Since a user agent can provide any From
header field value that the authentication service is willing to header field value that the authentication service is willing to
authorize, there is no reason why private SIP URIs that contain authorize, there is no reason why private SIP URIs that contain
legitimate domains (e.g., sip:anonymous@example.com) cannot be signed legitimate domains (e.g., sip:anonymous@example.com) cannot be signed
by an authentication service. The construction of the Identity by an authentication service. The construction of the Identity
header is the same for private URIs as it is for any other sort of header is the same for private URIs as it is for any other sort of
URIs. URIs.
Note, however, that even when using anonymous SIP URIs, an Note, however, that even when using anonymous SIP URIs, an
authentication service must possess a certificate corresponding to authentication service must possess a certificate corresponding to
the host portion of the addr-spec of the From header field of the the host portion of the addr-spec of the From header field of the
request; accordingly, using domains like 'anonymous.invalid' will not request; accordingly, using domains like 'anonymous.invalid' will not
be possible for privacy services that also act as authentication be possible for privacy services that also act as authentication
services. The assurance offered by the usage of anonymous URIs with services. The assurance offered by the usage of anonymous URIs with
a valid domain portion is "this is a known user in my domain that I a valid domain portion is "this is a known user in my domain that I
have authenticated, but I am keeping its identity private". The use have authenticated, but I am keeping its identity private".
of the domain 'anonymous.invalid' entails that no corresponding
authority for the domain can exist, and as a consequence, It is worth noting two features of this more anonymous form of
authentication service functions for that domain are meaningless. identity. One can eliminate any identifying information in a domain
through the use of the domain 'anonymous.invalid," but we must then
acknowledge that it is difficult for a domain to be both anonymous
and authenticated. The use of the "anonymous.invalid" domain entails
that no corresponding authority for the domain can exist, and as a
consequence, authentication service functions for that domain are
meaningless. The second feature is more germane to the threats this
document mitigates [RFC7375]. None of the relevant attacks, all of
which rely on the attacker taking on the identity of a victim or
hiding their identity using someone else's identity, are enabled by
an anonymous identity. As such, the inability to assert an authority
over an anonymous domain is irrelevant to our threat model.
[RFC3325] defines the "id" priv-value token, which is specific to the [RFC3325] defines the "id" priv-value token, which is specific to the
P-Asserted-Identity header. The sort of assertion provided by the P- P-Asserted-Identity header. The sort of assertion provided by the P-
Asserted-Identity header is very different from the Identity header Asserted-Identity header is very different from the Identity header
presented in this document. It contains additional information about presented in this document. It contains additional information about
the sender of a message that may go beyond what appears in the From the sender of a message that may go beyond what appears in the From
header field; P-Asserted-Identity holds a definitive identity for the header field; P-Asserted-Identity holds a definitive identity for the
sender that is somehow known to a closed network of intermediaries sender that is somehow known to a closed network of intermediaries.
that presumably the network will use this identity for billing or Presumably, that network will use this identity for billing or
security purposes. The danger of this network-specific information security purposes. The danger of this network-specific information
leaking outside of the closed network motivated the "id" priv-value leaking outside of the closed network motivated the "id" priv-value
token. The "id" priv-value token has no implications for the token. The "id" priv-value token has no implications for the
Identity header, and privacy services MUST NOT remove the Identity Identity header, and privacy services MUST NOT remove the Identity
header when a priv-value of "id" appears in a Privacy header. header when a priv-value of "id" appears in a Privacy header.
The optional "canon" parameter of the Identity header specified in The optional "canon" parameter of the Identity header specified in
this document provides the complete JSON objects used to generate the this document provides the complete JSON objects used to generate the
digest-string of the Identity header, including the canonicalized signed-identity-digest of the Identity header, including the
form of the telephone number of the originator of a call. In some canonicalized form of the telephone number of the originator of a
contexts, local policy may require a canonicalization which differs call, if the signature is over a telephone number. In some contexts,
local policy may require a canonicalization which differs
substantially from the original From header field. Depending on substantially from the original From header field. Depending on
those policies, potentially the "canon" parameter might divulge those policies, potentially the "canon" parameter might divulge
information about the originating network or user that might not information about the originating network or user that might not
appear elsewhere in the SIP request. Were it to be used to reflect appear elsewhere in the SIP request. Were it to be used to reflect
the contents of the P-Asserted-Identity header field, for example, the contents of the P-Asserted-Identity header field, for example,
then "canon" would need to be removed when the P-Asserted-Identity then "canon" would need to be removed when the P-Asserted-Identity
header is removed to avoid any such leakage outside of a trust header is removed to avoid any such leakage outside of a trust
domain. Since, in those contexts, the canonical form of the sender's domain. Since, in those contexts, the canonical form of the sender's
identity could not be reassembled by a verifier, and thus the identity could not be reassembled by a verifier, and thus the
Identity signature validation process would fail, using P-Asserted- Identity signature validation process would fail, using P-Asserted-
Identity with the Identity "canon" parameter in this fashion is NOT Identity with the Identity "canon" parameter in this fashion is NOT
RECOMMENDED outside of environments where SIP requests will never RECOMMENDED outside of environments where SIP requests will never
leave the trust domain. leave the trust domain. As a side note, history shows that closed
networks never stay closed and one should design their implementation
assuming connectivity to the broader Internet.
Finally, note that unlike [RFC3325], the mechanism described in this Finally, note that unlike [RFC3325], the mechanism described in this
specification adds no information to SIP requests that has privacy specification adds no information to SIP requests that has privacy
implications. implications.
11. Security Considerations 11. Security Considerations
This document describes a mechanism that provides a signature over This document describes a mechanism that provides a signature over
the Date header field of SIP requests, parts of the To and From the Date header field of SIP requests, parts of the To and From
header fields, the request method, and when present any media keying header fields, the request method, and when present any media keying
material in the message body. In general, the considerations related material in the message body. In general, the considerations related
to the security of these headers are the same as those given in to the security of these headers are the same as those given in
[RFC3261] for including headers in tunneled 'message/sip' MIME bodies [RFC3261] for including headers in tunneled 'message/sip' MIME bodies
(see Section 23 in particular). The following section details the (see Section 23 of RFC3261 in particular). The following section
individual security properties obtained by including each of these details the individual security properties obtained by including each
header fields within the signature; collectively, this set of header of these header fields within the signature; collectively, this set
fields provides the necessary properties to prevent impersonation. of header fields provides the necessary properties to prevent
It addresses the solution-specific attacks again in-band solutions impersonation. It addresses the solution-specific attacks against
enumerated in [RFC7375] Section 4.1. in-band solutions enumerated in [RFC7375] Section 4.1.
11.1. Protected Request Fields 11.1. Protected Request Fields
The From header field value (in ordinary operations) indicates the The From header field value (in ordinary operations) indicates the
identity of the sender of the message, and the SIP address-of-record identity of the sender of the message. The SIP address-of-record
URI, or an embedded telephone number, in the From header field is the URI, or an embedded telephone number, in the From header field is the
identity of a SIP user, for the purposes of this document. Note that identity of a SIP user, for the purposes of this document. Note that
in some deployments the identity of the sender may reside in P- in some deployments the identity of the sender may reside in P-
Asserted-Id instead. The sender's identity is the key piece of Asserted-Id instead. The sender's identity is the key piece of
information that this mechanism secures; the remainder of the signed information that this mechanism secures; the remainder of the signed
parts of a SIP request are present to provide reference integrity and parts of a SIP request are present to provide reference integrity and
to prevent certain types of cut-and-paste attacks. to prevent certain types of cut-and-paste attacks.
The Date header field value protects against cut-and-paste attacks, The Date header field value protects against cut-and-paste attacks,
as described in [RFC3261], Section 23.4.2. Implementations of this as described in [RFC3261], Section 23.4.2. Implementations of this
specification MUST NOT deem valid a request with an outdated Date specification MUST NOT deem valid a request with an outdated Date
header field (the RECOMMENDED interval is that the Date header must header field (the RECOMMENDED interval is that the Date header must
indicate a time within 60 seconds of the receipt of a message). Note indicate a time within 60 seconds of the receipt of a message). Note
that per baseline [RFC3261] behavior, servers keep state of recently that per baseline [RFC3261] behavior, servers keep state of recently
received requests, and thus if an Identity header is replayed by an received requests, and thus if an Identity header is replayed by an
attacker within the Date interval, verifiers can detect that it is attacker within the Date interval, verifiers can detect that it is
spoofed; because a message with an identical Date from the same spoofed because a message with an identical Date from the same source
source had recently been received. had recently been received.
The To header field value provides the identity of the SIP user that The To header field value provides the identity of the SIP user that
this request originally targeted. Providing the To header field in this request originally targeted. Providing the To header field in
the Identity signature serves two purposes: first, it prevents cut- the Identity signature serves two purposes. First, it prevents cut-
and-paste attacks in which an Identity header from legitimate request and-paste attacks in which an Identity header from legitimate request
for one user is cut-and-pasted into a request for a different user; for one user is cut-and-pasted into a request for a different user.
second, it preserves the starting URI scheme of the request, which Second, it preserves the starting URI scheme of the request, which
helps prevent downgrade attacks against the use of SIPS. The To helps prevent downgrade attacks against the use of SIPS. The To
offers additional protection against cut-and-paste attacks beyond the offers additional protection against cut-and-paste attacks beyond the
Date header field: for example, without a signature over the To, an Date header field. For example, without a signature over the To, an
attacker who receives a call from a target could immediately forward attacker who receives a call from a target could immediately forward
the INVITE to the target's voicemail service within the Date the INVITE to the target's voicemail service within the Date
interval, and the voicemail service would have no way knowing that interval, and the voicemail service would have no way knowing that
the Identity header it received had been originally signed for a call the Identity header it received had been originally signed for a call
intended for a different number. However, note the caveats below in intended for a different number. However, note the caveats below in
Section 11.1.1. Section 11.1.1.
When signing a request that contains a fingerprint of keying material When signing a request that contains a fingerprint of keying material
in SDP for DTLS-SRTP [RFC5763], this mechanism always provides a in SDP for DTLS-SRTP [RFC5763], this mechanism always provides a
signature over that fingerprint. This signature prevents certain signature over that fingerprint. This signature prevents certain
classes of impersonation attacks in which an attacker forwards or classes of impersonation attacks in which an attacker forwards or
cut-and-pastes a legitimate request: although the target of the cut-and-pastes a legitimate request. Although the target of the
attack may accept the request, the attacker will be unable to attack may accept the request, the attacker will be unable to
exchange media with the target as they will not possess a key exchange media with the target as they will not possess a key
corresponding to the fingerprint. For example there are some baiting corresponding to the fingerprint. For example, there are some
attacks, launched with the REFER method or through social baiting attacks, launched with the REFER method or through social
engineering, where the attacker receives a request from the target engineering, where the attacker receives a request from the target
and reoriginates it to a third party: these might not be prevented by and reoriginates it to a third party. These might not be prevented
only a signature over the From, To and Date, but could be prevented by only a signature over the From, To and Date, but could be
by securing a fingerprint for DTLS-SRTP. While this is a different prevented by securing a fingerprint for DTLS-SRTP. While this is a
form of impersonation than is commonly used for robocalling, different form of impersonation than is commonly used for
ultimately there is little purpose in establishing the identity of robocalling, ultimately there is little purpose in establishing the
the user that originated a SIP request if this assurance is not identity of the user that originated a SIP request if this assurance
coupled with a comparable assurance over the contents of the is not coupled with a comparable assurance over the contents of the
subsequent media communication. This signature also, per [RFC7258], subsequent media communication. This signature also, per [RFC7258],
reduces the potential for passive monitoring attacks against the SIP reduces the potential for passive monitoring attacks against the SIP
media. In environments where DTLS-SRTP is unsupported, however, no media. In environments where DTLS-SRTP is unsupported, however, no
field is signed and no protections are provided. field is signed and no protections are provided.
11.1.1. Protection of the To Header and Retargeting 11.1.1. Protection of the To Header and Retargeting
The mechanism in this document provides a signature over the identity The mechanism in this document provides a signature over the identity
information in the To header field value of requests. This provides information in the To header field value of requests. This provides
a means for verifiers to detect replay attacks where a signed request a means for verifiers to detect replay attacks where a signed request
skipping to change at page 26, line 13 skipping to change at page 26, line 26
attacker to another, unrelated target. Armed with the original value attacker to another, unrelated target. Armed with the original value
of the To header field, the recipient of a request may compare it to of the To header field, the recipient of a request may compare it to
their own identity in order to determine whether or not the identity their own identity in order to determine whether or not the identity
information in this call might have been replayed. However, any information in this call might have been replayed. However, any
request may be legitimately retargeted as well, and as a result request may be legitimately retargeted as well, and as a result
legitimate requests may reach a SIP endpoint whose user is not legitimate requests may reach a SIP endpoint whose user is not
identified by the URI designated in the To header field value. It is identified by the URI designated in the To header field value. It is
therefore difficult for any verifier to decide whether or not some therefore difficult for any verifier to decide whether or not some
prior retargeting was "legitimate." Retargeting can also cause prior retargeting was "legitimate." Retargeting can also cause
confusion when identity information is provided for requests sent in confusion when identity information is provided for requests sent in
the backwards in a dialog, as the dialog identifiers may not match the backwards direction in a dialog, as the dialog identifiers may
credentials held by the ultimate target of the dialog. For further not match credentials held by the ultimate target of the dialog. For
information on the problems of response identity see further information on the problems of response identity see
[I-D.peterson-sipping-retarget]. [I-D.peterson-sipping-retarget].
Any means for authentication services or verifiers to anticipate Any means for authentication services or verifiers to anticipate
retargeting is outside the scope of this document, and likely to have retargeting is outside the scope of this document, and likely to have
equal applicability to response identity as it does to requests in equal applicability to response identity as it does to requests in
the backwards direction within a dialog. Consequently, no special the backwards direction within a dialog. Consequently, no special
guidance is given for implementers here regarding the 'connected guidance is given for implementers here regarding the 'connected
party' problem (see [RFC4916]); authentication service behavior is party' problem (see [RFC4916]); authentication service behavior is
unchanged if retargeting has occurred for a dialog-forming request. unchanged if retargeting has occurred for a dialog-forming request.
Ultimately, the authentication service provides an Identity header Ultimately, the authentication service provides an Identity header
skipping to change at page 29, line 44 skipping to change at page 30, line 15
headers are always good. headers are always good.
11.6. Display-Names and Identity 11.6. Display-Names and Identity
As a matter of interface design, SIP user agents might render the As a matter of interface design, SIP user agents might render the
display-name portion of the From header field of a caller as the display-name portion of the From header field of a caller as the
identity of the caller; there is a significant precedent in email identity of the caller; there is a significant precedent in email
user interfaces for this practice. Securing the display-name user interfaces for this practice. Securing the display-name
component of the From header field value is outside the scope of this component of the From header field value is outside the scope of this
document, but may be the subject of future work, such as through the document, but may be the subject of future work, such as through the
"spec" name mechanism. "type" name mechanism.
In the absence of signing the display-name, authentication services In the absence of signing the display-name, authentication services
might check and validate it, and compare it to a list of acceptable might check and validate it, and compare it to a list of acceptable
display-names that may be used by the sender; if the display-name display-names that may be used by the sender; if the display-name
does not meet policy constraints, the authentication service could does not meet policy constraints, the authentication service could
return a 403 response code. In this case, the reason phrase should return a 403 response code. In this case, the reason phrase should
indicate the nature of the problem; for example, "Inappropriate indicate the nature of the problem; for example, "Inappropriate
Display Name". However, the display-name is not always present, and Display Name". However, the display-name is not always present, and
in many environments the requisite operational procedures for in many environments the requisite operational procedures for
display-name validation may not exist, so no normative guidance is display-name validation may not exist, so no normative guidance is
skipping to change at page 30, line 43 skipping to change at page 31, line 16
is hereby deprecated, and should be treated as such. It is not is hereby deprecated, and should be treated as such. It is not
believed that any implementations are making use of this value. believed that any implementations are making use of this value.
Future specifications may consider elliptical curves for smaller key Future specifications may consider elliptical curves for smaller key
sizes. sizes.
Note that the Identity-Info header is also deprecated by this Note that the Identity-Info header is also deprecated by this
specification, and thus the "alg" parameter is now a value of the specification, and thus the "alg" parameter is now a value of the
Identity header, not Identity-Info. Identity header, not Identity-Info.
12.3. spec parameter Names
This specification requests that the IANA create a new registry for
spec parameter names. The registry will consist solely of a list of
names mapped to any specification where the procedures are defined
(or "N/A" if no specification is available).
The syntax of "spec" names is given in Section 8. Registering a new
"spec" name is on a First Come First Serve basis.
This specification does not provide any initial values for "spec"
names.
13. Acknowledgments 13. Acknowledgments
The authors would like to thank Stephen Kent, Brian Rosen, Alex The authors would like to thank Stephen Kent, Brian Rosen, Alex
Bobotek, Paul Kyzviat, Jonathan Lennox, Richard Shockey, Martin Bobotek, Paul Kyzviat, Jonathan Lennox, Richard Shockey, Martin
Dolly, Andrew Allen, Hadriel Kaplan, Sanjay Mishra, Anton Baskov, Dolly, Andrew Allen, Hadriel Kaplan, Sanjay Mishra, Anton Baskov,
Pierce Gorman, David Schwartz, Philippe Fouquart, Michael Hamer, Pierce Gorman, David Schwartz, Philippe Fouquart, Michael Hamer,
Henning Schulzrinne, and Richard Barnes for their comments. Henning Schulzrinne, and Richard Barnes for their comments.
14. Changes from RFC4474 14. Changes from RFC4474
skipping to change at page 31, line 30 skipping to change at page 31, line 38
Generalized the credential mechanism; credential enrollment, Generalized the credential mechanism; credential enrollment,
acquisition and trust is now outside the scope of this document acquisition and trust is now outside the scope of this document
Reduced the scope of the Identity signature to remove CSeq, Call- Reduced the scope of the Identity signature to remove CSeq, Call-
ID, Contact, and the message body ID, Contact, and the message body
Removed the Identity-Info header and relocated its components into Removed the Identity-Info header and relocated its components into
parameters of the Identity header parameters of the Identity header
Added any DTLS-SRTP fingerprint in SDP as a mandatory element of Added any DTLS-SRTP fingerprint in SDP as a mandatory element of
the digest-string the PASSporT
Deprecated 'rsa-sha1' in favor of new baseline signing algorithm Deprecated 'rsa-sha1' in favor of new baseline signing algorithm
Changed the identity-digest-string format for compatibility with Changed the signed-identity-digest format for compatibility with
JWT PASSporT
15. References 15. References
15.1. Normative References 15.1. Normative References
[I-D.wendt-verified-token]
Wendt, C., "Verified Token", draft-wendt-verified-token-00
(work in progress), October 2015.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>. <http://www.rfc-editor.org/info/rfc2818>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>. <http://www.rfc-editor.org/info/rfc3261>.
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