rfc9410.original   rfc9410.txt 
STIR Working Group C. Wendt Internet Engineering Task Force (IETF) C. Wendt
Internet-Draft Somos Inc. Request for Comments: 9410 Somos Inc.
Intended status: Standards Track 25 February 2023 Category: Standards Track July 2023
Expires: 29 August 2023 ISSN: 2070-1721
Identity Header Errors Handling for STIR Handling of Identity Header Errors for Secure Telephone Identity
draft-ietf-stir-identity-header-errors-handling-08 Revisited (STIR)
Abstract Abstract
This document extends STIR and the Authenticated Identity Management This document extends the current error-handling procedures for
in the Session Initiation Protocol (SIP) error handling procedures to mapping of verification failure reasons to 4xx codes for Secure
include the mapping of verification failure reasons to STIR defined Telephone Identity Revisited (STIR) and the Authenticated Identity
4xx codes so the failure reason of an Identity header field can be Management in the Session Initiation Protocol (SIP). It extends the
conveyed to the upstream authentication service when local policy ability to use the Reason header field as an option for conveying an
dictates that the call should continue in the presence of a error associated with an Identity header field to the upstream
verification failure. This document also defines procedures that authentication service when local policy dictates that the call
enable a failure reason to be mapped to a specific Identity header should continue in the presence of a verification failure. This
field for scenarios that use multiple Identity header fields where document also defines procedures that enable a failure reason to be
some may have errors and others may not and the handling of those mapped to a specific Identity header field for scenarios that use
situations is defined. multiple Identity header fields, where some may have errors and
others may not. The handling of those situations is also defined.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 29 August 2023. Information about the current status of this document, any errata,
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https://www.rfc-editor.org/info/rfc9410.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2023 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology
3. Reason header field protocol "STIR" . . . . . . . . . . . . . 3 3. Reason Header Field Protocol "STIR"
4. Use of provisional response to signal errors without 4. Use of Provisional Response to Signal Errors without
terminating the call . . . . . . . . . . . . . . . . . . 3 Terminating the Call
5. Handling of a verification error when there are multiple 5. Handling of a Verification Error When There Are Multiple
Identity header fields . . . . . . . . . . . . . . . . . 4 Identity Header Fields
6. Handling multiple verification errors . . . . . . . . . . . . 5 6. Handling Multiple Verification Errors
7. Removal of the Reason header field by Authentication 7. Removal of the Reason Header Field by Authentication Service
Service . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 9. Security Considerations
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 10. References
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References
10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Informative References
10.2. Informative References . . . . . . . . . . . . . . . . . 7 Acknowledgements
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 7 Author's Address
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
The STIR framework as described in [RFC7340] is an authentication The STIR framework as described in [RFC7340] is an authentication
framework for asserting a telephone number or URI based identity framework for asserting a telephone number or URI-based identity
using a digital signature and certificate based framework as using a digital signature and certificate-based framework, as
described in [RFC8225] and [RFC8226] respectively. [RFC8224] described [RFC8225] and [RFC8226], respectively. [RFC8224] describes
describes the use of the STIR framework in the SIP protocol [RFC3261] the use of the STIR framework in the SIP protocol [RFC3261]. It
and defines both the authentication service that creates a PASSporT, defines both a) the authentication service that creates a PASSporT
defined in [RFC8225], and delivers it in an Identity header field and [RFC8225] and delivers it in an Identity header field, and b) the
the verification service that correspondingly verifies the PASSporT verification service that correspondingly verifies the PASSporT and
and embedded originating identity. embedded originating identity.
This document is concerned with errors in validating PASSporTs and This document is concerned with errors in validating PASSporTs and
Identity header fields and how they are communicated in special cases Identity header fields and how they are communicated in special
and defines a solution to help address the potential issue of cases. This document also defines a solution to help address the
multiple Identity header fields and the plurality of potential potential issue of multiple Identity header fields and the plurality
verification errors. Additionally, it addresses the issue of the of potential verification errors. Additionally, it addresses the
current 4xx error response and that when there is a verification issue of the current 4xx error response, i.e., the call is terminated
error, the call is terminated. In some deployments, it may be the when a verification error is present. In some deployments, it may be
case that the policy for handling errors dictates that calls should the case that the policy for handling errors dictates that calls
continue even if there is a verification error. In many cases of, should continue even if there is a verification error. For example,
for example, inadvertent or operational errors that do not represent in many cases of inadvertent or operational errors that do not
any identity falsification type of attempt, the policy of continuing represent any type of identity falsification attempt, the preferred
the call even though the identity is not verified, may be the policy may be to continue the call despite the unverified identity.
preferred policy. In these cases, the authentication service should In these cases, the authentication service should still be notified
still be notified of the error so that corrective action can be taken of the error so that corrective action can be taken to fix any
to fix any issues. This specification will discuss the use of the issues. This specification will discuss the use of the Reason header
Reason header field in subsequent provisional (1xx) responses in field in subsequent provisional (1xx) responses in order to deliver
order to deliver the error back to the authentication service or the error back to the authentication service or other SIP path
other SIP path network equipment responsible for error handling. network equipment responsible for error handling.
For the handling of multiple Identity header fields and the potential To handle multiple Identity header fields where some in a call may be
situation that some of the Identity header fields in a call may pass verified while others may not (i.e., they have errors), this document
verification but others may have errors, this document defines the defines a method by which an identifier is added to the header so
method of adding an identifier so that the authentication service can that the authentication service can uniquely identify which Identity
uniquely identify which Identity header field is being referred to in header field is being referred to in the case of an error.
the case of an error.
2. Terminology 2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Reason header field protocol "STIR" 3. Reason Header Field Protocol "STIR"
This document defines a new Reason header field [RFC3326] protocol This document defines a new Reason header field [RFC3326] protocol,
"STIR" for STIR applications using SIP as defined in [RFC8224]. The "STIR", for STIR applications using SIP as defined in [RFC8224]. The
use of "STIR" as a reason header field protocol with the [RFC8224] use of "STIR" as a Reason header field protocol with the error
defined error cause codes allows the use of multiple Reason header defined in [RFC8224] causes codes to allow the use of multiple Reason
fields defined in [RFC3326] and updated in header fields as detailed in [RFC3326] and updated in [RFC9366]. Any
[I-D.ietf-sipcore-multiple-reasons]. Any provisional SIP Response provisional SIP response message or final response message, with the
message or final response message, with the exception of a 100 exception of a 100 (Trying), MAY contain one or more Reason header
(Trying), MAY contain one or more Reason header fields with a STIR fields with a STIR-related cause code defined in [RFC8224] or future
related cause code defined in [RFC8224] or future specifications. specifications. The use of multiple Reason header fields is
The use of multiple Reason header field is discussed in more detail discussed in more detail later in the document.
later in the document.
4. Use of provisional response to signal errors without terminating the 4. Use of Provisional Response to Signal Errors without Terminating the
call Call
In cases where local policy dictates that a call should continue In cases where local policy dictates that a call should continue
regardless of any verification errors that may have occured, regardless of any verification errors that may have occurred,
including 4XX errors described in [RFC8224] Section 6.2.2, then the including 4xx errors described in Section 6.2.2 of [RFC8224], the
verification service MUST NOT send the 4XX as a response, but rather verification service MUST NOT send the 4xx as a response. Rather, it
include the error response code and reason phrase in a Reason header should include the error response code and reason phrase in a Reason
field, defined in [RFC3326], in the next provisional or final header field in the next provisional or final response it sends to
responses sent to the authentication service. the authentication service.
Example Reason header field: Example Reason header field:
Reason: STIR ;cause=436 ;text="Bad Identity Info" Reason: STIR ;cause=436 ;text="Bad Identity Info"
5. Handling of a verification error when there are multiple Identity 5. Handling of a Verification Error When There Are Multiple Identity
header fields Header Fields
In cases where a SIP message includes multiple Identity header fields In cases where a SIP message includes multiple Identity header fields
and one of those Identity header fields has an error, the and one of those Identity header fields has an error, the
verification service MUST include the error response code and reason verification service MUST include the error response code and reason
phrase associated with the error in a Reason header field, defined in phrase associated with the error in a Reason header field, defined in
[RFC3326], in the next provisional or final responses sent to the [RFC3326], in the next provisional or final responses sent to the
authentication service. The reason cause in the Reason header field authentication service. The reason cause in the Reason header field
MUST represent the error that occurred when verifying the contents of MUST represent the error that occurred when verifying the contents of
the Identity header field. For a SIP INVITE containing multiple the Identity header field. For a SIP INVITE containing multiple
Identity header fields, the "ppi" parameter for the Reason header Identity header fields, the "ppi" parameter for the Reason header
field is RECOMMENDED. As defined in [RFC8224], the STIR error codes field is RECOMMENDED. As defined in [RFC8224], the STIR error codes
used in responses are based on an error associated with a specific used in responses are based on an error associated with a specific
identity header field representing a single error occurring with the Identity header field representing a single error occurring with the
verification and processing of that identity header field. The verification and processing of that Identity header field. The
association of a "ppi" parameter with a Reason header field using association of a "ppi" parameter with a Reason header field [RFC3326]
"STIR" protocol MUST only identify a single cause code in the context using the protocol value of "STIR" defined in this document MUST only
of a call dialog defined in [RFC8224] or in future documents defining identify a single cause code [RFC3326] in the context of a call
STIR related errors. The associated PASSporT object can be included dialog [RFC3261] corresponding only to the STIR-related error codes
either in full form or in compact form, where only the signature of defined in [RFC8224] or future documents defining STIR-related error
the PASSporT is included with two periods as a prefix as defined in codes. The associated PASSporT object can be included either in full
[RFC8225] Section 7 to identify the reported Identity header field form or in compact form, where only the signature of the PASSporT is
with an error. Compact form is the recommended form as full form may included with two periods as a prefix, as defined in Section 7 of
[RFC8225], to identify the reported Identity header field with an
error. Compact form is the recommended form, as full form may
include information that could have privacy or security implications include information that could have privacy or security implications
in some call scenarios as discussed in Section 9. in some call scenarios; this is discussed in Section 9.
Example Reason header field with full form PASSporT: Example Reason header field with a full form PASSporT:
Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \ Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \
"eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1I \ "eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1I \
joiaHR0cHM6Ly9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9.eyJ \ joiaHR0cHM6Ly9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9.eyJ \
kZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdC \ kZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdC \
I6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0.r \ I6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0.r \
q3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYs \ q3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYs \
ojNCpTzO3QfPOlckGaS6hEck7w" ojNCpTzO3QfPOlckGaS6hEck7w"
Example Reason header field with compact form PASSporT: Example Reason header field with a compact form PASSporT:
Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \ Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \
"..rq3pjT1akEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYs \ "..rq3pjT1akEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYs \
ojNCpTzO3QfPOlckGaS6hEck7w" ojNCpTzO3QfPOlckGaS6hEck7w"
6. Handling multiple verification errors 6. Handling Multiple Verification Errors
If there are multiple Identity header field verification errors being If there are multiple Identity header field verification errors being
reported the verification service MUST include a corresponding number reported, the verification service MUST include a corresponding
of Reason header fields per error. These Reason header fields should number of Reason header fields per error. These Reason header fields
include a "ppi" parameters including the full or compact form of the should include a "ppi" parameter, including the full or compact form
PASSporT with cause and text parameters identifying each error. As of the PASSporT with cause and text parameters identifying each
mentioned previously, the potential use of multiple Reason header error. As mentioned previously, the potential use of multiple Reason
fields defined in [RFC3326] is updated in header fields defined in [RFC3326] is updated in [RFC9366], allowing
[I-D.ietf-sipcore-multiple-reasons] allowing multiple Reason header multiple Reason header fields with the same protocol value. For this
fields with the same protocol value. For this specification, "STIR" specification, "STIR" should be used for any STIR error defined in
should be used for any STIR error defined in [RFC8224] or future [RFC8224] or future specifications.
specifications.
Example Reason header fields for two identity info errors: Example Reason header fields for two identity info errors:
Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \ Reason: STIR ;cause=436 ;text="Bad Identity Info" ;ppi= \
"..rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFY \ "..rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFY \
pFYsojNCpTzO3QfPOlckGaS6hEck7w" pFYsojNCpTzO3QfPOlckGaS6hEck7w"
Reason: STIR ;cause=438 ;text="Invalid Identity Header" ;ppi= \ Reason: STIR ;cause=438 ;text="Invalid Identity Header" ;ppi= \
"..rJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYsq3pjT1hoRwakEGjHCnWSwUnsh \ "..rJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYsq3pjT1hoRwakEGjHCnWSwUnsh \
d0-zckGaS6hEck7wojNCpTzO3QfPOl" d0-zckGaS6hEck7wojNCpTzO3QfPOl"
7. Removal of the Reason header field by Authentication Service 7. Removal of the Reason Header Field by Authentication Service
When an Authentication Service [RFC8224] receives the Reason header When an authentication service [RFC8224] receives the Reason header
field with a PASSporT it generated as part of an Identity header field with a PASSporT it generated as part of an Identity header
field and the authentication of a call, it should first follow local field and the authentication of a call, it should first follow local
policy to recognize and acknowledge the error (e.g. perform policy to recognize and acknowledge the error (e.g., perform
operational actions like logging or alarming), but then MUST remove operational actions like logging or alarming). Then, it MUST remove
the identified Reason header field to avoid the PASSporT information the identified Reason header field to avoid the PASSporT information
from going upstream to a UAC or UAS that may not be authorized to see from going upstream to a User Agent Client (UAC) or User Agent Server
claim information contained in the PASSporT for privacy or other (UAS) that may not be authorized to see claim information contained
reasons. in the PASSporT for privacy or other reasons.
8. IANA Considerations 8. IANA Considerations
This document requests the definition of a new protocol value (and IANA has registered the following new protocol value (and associated
associated protocol cause) to be registered by the IANA into the protocol cause) in the "Reason Protocols" registry under
"Reason Protocols" sub-registry under <http://www.iana.org/assignments/sip-parameters>:
http://www.iana.org/assignments/sip-parameters as follows:
Protocol Value Protocol Cause Reference +================+=================+===========+
-------------- --------------- ----------- | Protocol Value | Protocol Cause | Reference |
STIR STIR Error code RFC 8224 +================+=================+===========+
This document also requests the definition of a new header field | STIR | STIR error code | [RFC8224] |
parameter name to be registered by IANA into the Header Field +----------------+-----------------+-----------+
Parameters and Parameter Values sub-registry under
https://www.iana.org/assignments/sip-parameters as follows:
Header Field Parameter Name Predefined Values Reference Table 1
------------ -------------- ----------------- ---------
Reason ppi No RFC THIS IANA has also registered a new header field parameter name in the
"Header Field Parameters and Parameter Values" registry under
<https://www.iana.org/assignments/sip-parameters>:
+==============+================+===================+===========+
| Header Field | Parameter Name | Predefined Values | Reference |
+==============+================+===================+===========+
| Reason | ppi | No | RFC 9410 |
+--------------+----------------+-------------------+-----------+
Table 2
9. Security Considerations 9. Security Considerations
This specification discusses the use of a PASSporT as an identifier This specification discusses the use of a PASSporT as an identifier
for cases where there are multiple identity header field errors for cases where there are multiple identity header field errors
occuring as part of the Reason header field response. For some call occurring as part of the Reason header field response. For some call
scenarios (e.g. diversion based call flows) the signer of the scenarios (e.g., diversion-based call flows), the signer of the
PASSporT(s) may not be the first hop initiator of the call. In those PASSporT(s) may not be the first-hop initiator of the call. In those
cases, there may be some security or privacy concerns associated with cases, there may be some security or privacy concerns associated with
PASSporT information that is passed upstream beyond the PASSporT information that is passed upstream beyond the
authentication service that originally signed the PASSporT(s) in the authentication service that originally signed the PASSporT(s) in the
resulting error Reason header field. This specification states the resulting error Reason header field. This specification states that
authentication service MUST remove the Reason header field with the the authentication service MUST remove the Reason header field with
PASSporT to protect the security (e.g. use of potentially still fresh the PASSporT to protect the security (e.g., use of a potentially
PASSporT for replay attacks) and privacy of any potential information still-fresh PASSporT for replay attacks) and privacy of any potential
that could be passed beyond the authentication service response back information that could be passed beyond the authentication service
in the direction of the call initiator. While this specification response back in the direction of the call initiator. While this
allows for both full and compact form of the PASSporT to be used as specification allows for both the full and compact form of the
the error identifier, use of the compact form is RECOMMENDED to avoid PASSporT to be used as the error identifier, use of the compact form
the potential exposure of call information contained in the full form is RECOMMENDED to avoid the potential exposure of call information
of the PASSporT. contained in the full form of the PASSporT.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-sipcore-multiple-reasons]
Sparks, R., "Multiple SIP Reason Header Field Values",
Work in Progress, Internet-Draft, draft-ietf-sipcore-
multiple-reasons-01, 23 August 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-sipcore-
multiple-reasons-01>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[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,
<https://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
skipping to change at page 7, line 35 skipping to change at line 312
[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion [RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018, Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>. <https://www.rfc-editor.org/info/rfc8225>.
[RFC8226] Peterson, J. and S. Turner, "Secure Telephone Identity [RFC8226] Peterson, J. and S. Turner, "Secure Telephone Identity
Credentials: Certificates", RFC 8226, Credentials: Certificates", RFC 8226,
DOI 10.17487/RFC8226, February 2018, DOI 10.17487/RFC8226, February 2018,
<https://www.rfc-editor.org/info/rfc8226>. <https://www.rfc-editor.org/info/rfc8226>.
[RFC9366] Sparks, R., "Multiple SIP Reason Header Field Values",
RFC 9366, DOI 10.17487/RFC9366, March 2023,
<https://www.rfc-editor.org/info/rfc9366>.
10.2. Informative References 10.2. Informative References
[RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure [RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
Telephone Identity Problem Statement and Requirements", Telephone Identity Problem Statement and Requirements",
RFC 7340, DOI 10.17487/RFC7340, September 2014, RFC 7340, DOI 10.17487/RFC7340, September 2014,
<https://www.rfc-editor.org/info/rfc7340>. <https://www.rfc-editor.org/info/rfc7340>.
Appendix A. Acknowledgements Acknowledgements
The author would like to thank David Hancock for help to identify The author would like to thank David Hancock for help identifying
these error scenarios and additionally Jon Peterson, Roman Shpount, these error scenarios, as well as Jon Peterson, Roman Shpount, Robert
Robert Sparks, Christer Holmberg and others in the STIR working group Sparks, Christer Holmberg, and others in the STIR Working Group for
for their helpful feedback and discussion. their helpful feedback and discussion.
Author's Address Author's Address
Chris Wendt Chris Wendt
Somos Inc. Somos Inc.
Email: chris-ietf@chriswendt.net Email: chris-ietf@chriswendt.net
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