Internet DRAFT - draft-korhonen-dime-e2e-security
draft-korhonen-dime-e2e-security
DIME J. Korhonen
Internet-Draft Broadcom Ltd.
Intended status: Standards Track H. Tschofenig
Expires: September 1, 2016 ARM Ltd.
February 29, 2016
Diameter AVP Level Security: Keyed Message Digests, Digital Signatures,
and Encryption
draft-korhonen-dime-e2e-security-03.txt
Abstract
This document defines an extension for end to end authentication,
integrity and confidentiality protection of Diameter Attribute Value
Pairs. The solutions focuses on protecting Diameter Attribute Value
Pairs and leaves the key distribution solution to a separate
specification. The integrity protection can be introduced in a
backward compatible manner to existing application. The
confidentiality protection requires an explicit support from an
application, thus is applicable only for newly defined applications.
Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 1, 2016.
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Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Solution description . . . . . . . . . . . . . . . . . . . . 4
2.1. Integrity protection of AVPs . . . . . . . . . . . . . . 4
2.2. Confidentiality protection of AVPs . . . . . . . . . . . 7
2.3. Definition of the 'End Point' . . . . . . . . . . . . . . 8
3. AVP Encoding . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Signed-Data AVP . . . . . . . . . . . . . . . . . . . . . 8
3.2. JWS-Header AVP . . . . . . . . . . . . . . . . . . . . . 8
3.3. Header-Parameters AVP . . . . . . . . . . . . . . . . . . 8
3.4. JWS-AVP-Payload AVP . . . . . . . . . . . . . . . . . . . 9
3.5. JWS-Signature AVP . . . . . . . . . . . . . . . . . . . . 9
3.6. Encrypted-Data AVP . . . . . . . . . . . . . . . . . . . 9
3.7. JWE-Header AVP . . . . . . . . . . . . . . . . . . . . . 9
3.8. JWE-Enc-Key AVP . . . . . . . . . . . . . . . . . . . . . 10
3.9. JWE-Init-Vec AVP . . . . . . . . . . . . . . . . . . . . 10
3.10. JWE-AVP-Ciphertext AVP . . . . . . . . . . . . . . . . . 10
4. Result-Code AVP Values . . . . . . . . . . . . . . . . . . . 10
4.1. Transient Failures . . . . . . . . . . . . . . . . . . . 10
4.2. Permanent Failures . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informational References . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
The Diameter base protocol [RFC6733] leverages IPsec and TLS for
mutual authentication between neighboring Diameter nodes and for
channel security offering data origin authentication, integrity and
confidentiality protection. The Diameter base protocol, however,
also defines Diameter agents, namely Relay Agents, Proxy Agents,
Redirect Agents, and Translation Agents.
Relay Agents are Diameter agents that accept requests and route
messages to other Diameter nodes based on information found in the
messages. Since Relays do not perform any application level
processing, they provide relaying services for all Diameter
applications.
Similarly to Relays, Proxy Agents route Diameter messages using the
Diameter routing table. However, they differ since they modify
messages to implement policy enforcement.
Redirect Agents do not relay messages, and only return an answer with
the information necessary for Diameter agents to communicate
directly, they do not modify messages. Redirect Agents do not have
negative impacts on end-to-end security and are therefore not
considered in this document.
A Translation Agent is a device that provides translation between two
protocols. To offer end-to-end security across different protocol
requires the ability to convey and process the AVPs defined in this
document by both end points. Since such support is very likely not
available this document does not cover this functionality.
The Diameter extension defined in this document specifies how AVP
authentication, integrity and confidentiality protection can be
offered using either symmetric or asymmetric cryptography. As a
solution mechanism is derived form Javascript Object Signing and
Encryption (JOSE). JOSE offers a simple encoding with small set of
features ideal for the purpose of Diameter. This document further
defines a binary efficient coding of JOSE objects.
This document focuses on protecting Diameter AVP and leaves the key
distribution solution to a separate specification, which most likely
is going to be a specific key exchange application. To offer the
functionality two grouped AVPs are defined: Signed-Data and
Encrypted-Data. The respective JOSE objects are transported within
these two AVPs.
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2. Solution description
2.1. Integrity protection of AVPs
JWS represents digitally signed or HMACed content using JSON data
structures. The representation in [I-D.ietf-jose-json-web-signature]
consists of three parts: the JWS Header, the JWS Payload, and the JWS
Signature. The three parts are represented as the concatenation of
the encoded strings in that order, with the three strings being
separated by period ('.') characters. For the JWS Payload one would
define a new JSON object that contains an array of AVP code number
and a hash of AVP pairs. The JWS Signature then covers the all APVs
to be signed or HMACed. Both JWS Payload and signature MUST use the
same hash algorithm of the cryptographic algorithm indicated in the
JWS Header.
Although the solution relies on the JSON, the encoding into Diameter
AVPs differ from the text based encoding of the JSON objects.
Specifically, none of of the JWS Header, JWS Payload or JWS Signature
are not BASE64 encoded but are processed in their plaintext or binary
representation formats. For example, the JWS Header is encoded in
its plaintext format into the Header-Parameters AVP:
{ "typ":"JWT",
"alg":"HS256",
"kid":"abc123"
}
The JWS Payload and the JWS Signature hashes and AVP Code values are
encoded in their binary format as octets, not in textual or BASE64
encoded formats. Sections 3.4 and 3.5 describe the encodings of the
needed AVPs.
To package a set of AVPs for signing, each AVP octet representation
to be protected are first individually hashed and encoded into the
"JSON object" with its four octets AVP code number. The entire AVP
MUST be input to the hash calculation, from the first byte of the AVP
code to the last byte of the AVP data, including all other fields,
length, reserved/flags, and optional vendor IDs, and padding. The
AVP MUST be input to the hash calculation in network byte order.
The JWS Signature is calculated over the entire JWS Payloads and then
the all three JWS parts are placed in the Signed-Data AVP. There can
be multiple Signed-Data AVPs in a Diameter message. The AVP code in
the JWS Payload is to indicate which AVP this hash possibly refers
to. If there are multiple instances of the same AVP in the Diameter
message, there is no other way than make the verification against all
of those. It is possible that the message sender only hashed one AVP
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of the same type and, therefore, the receiver MUST verify the hash
against all occurrences of the AVP of the same code number. Such
flexibility is added there to allow reordering of the AVPs and
addition or deletion of new AVPs by intermediating agents.
If a receiver detects errors with the processing of the Signed-Data
AVP it MAY return one of the errors defined in Section 4. If a
receiver does not find any AVP the Signed-Data AVP has a signature
for, it MAY also return one of the errors defined in Section 4.
When AVPs are to be both encrypted and signed, the Encrypted-Data AVP
MUST be created first. This means that signing is "outside"
encryption.
Here is an example: Imagine the following AVPs from the QoS-Resources
AVP in the QoS-Install Request (defined in RFC 5866 [RFC5866] message
shall be signed. The resulting example message has the following
structure:
<QoS-Install-Request> ::= < Diameter Header: 327, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Request-Type }
[ Signed-Data ]
* [ QoS-Resources ]
...
Example Diameter Message with Signed-Data AVP
The Signed-Data AVP in this example may contain a JWS Header that
indicates the use of the HMAC SHA-256 algorithm with the key id
'abc123'. The protected AVPs are Session-Id, Origin-Host and Origin-
Realm. The calculated HMAC SHA-256 values are for example purposes
only (i.e., are not real):
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JWS Header encoded as such in JWS-Header AVP:
{"typ":"JWT",
"alg":"HS256",
"kid":"abc123"
}
0x00000xxx // JWS-Header code 'xxx'
0x00000034 // Flags=0, Length=52
'{"typ":"JWT","alg":"HS256","kid":"abc123"}' // 41
0x00,0x00,0x00 // 3 octets padding
JWS Payload encoded into three JWS-AVP-Payload AVPs:
0x00000zzz // JWS-AVP-Payload code 'zzz' <--+
0x0000001c // Flags=0, Length=28 |
0x00000107 // 263, Session-Id, 4 octets s
0x9d0e0495 // hash of Session-Id, 128 bits i
0xba8c0312 g
0xb6274c52 n
0x7d51a048 a
t
0x00000zzz // JWS-AVP-Payload code 'zzz' u
0x0000001c // Flags=0, Length=28 r
0x00000108 // 264, Origin-Host, 4 octets e
0x39ca88ff // hash of Origin-Host, 128 bits |
0xaa5a6ff9 c
0x029ed95b o
0xa534e028 v
e
0x00000zzz // JWS-AVP-Payload code 'zzz' r
0x0000001c // Flags=0, Length=28 a
0x00000128 // 296, Origin-Realm, 4 octets g
0x202730ac // hash of Origin-Realm, 128 bits e
0xa6e3a180 |
0x2f44a633 |
0xf250f6fe <--+
JWS Signature encoded into the JWS-Signature AVP:
0x00000yyy // JWS-Signature code 'yyy'
0x00000018 // Flags=0, Length=24
0xaabbccdd,0xddeeff00,0x11223344,0x55667788
Example JWS Header, Payload and Signature
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2.2. Confidentiality protection of AVPs
The Encrypted-Data AVP (AVP Code TBD) is of type OctetString and
contains the JSON Web Encryption (JWE)
[I-D.ietf-jose-json-web-encryption] data structure and consists of
four parts: the JWE Header, the JWE Encrypted Key, the JWE
Initialization Vector and the JWE Ciphertext. The four parts are
represented as the concatenation of the encoded strings in that
order, with the three strings being separated by period ('.')
characters. JWE does not add a content integrity check if not
provided by the underlying encryption algorithm.
Although the solution relies on the JSON, the encoding into Diameter
AVPs differ from the text based encoding of the JSON objects.
Specifically, none of of the the JWE Header, the JWE Encrypted Key,
the JWE Initialization Vector and the JWE Ciphertext are not BASE64
encoded but are processed in their plaintext or binary representation
formats. The concept follows what was already described in
Section 2.1.
A single AVP or an entire list of AVPs MUST be input to the
encryption process, from the first byte of the AVP code to the last
byte of the AVP data, including all other fields, length, reserved/
flags, and optional vendor IDs, and padding. The AVP MUST be input
to the encryption process in network byte order, and the encryptor is
free to order AVPs whatever way it chooses. When AVPs are to be both
encrypted and authenticated, the Encrypted-Data AVP MUST be created
first.
Note that the usage of the Encrypted-Data AVP requires explicit
support by the Diameter application since a receiving Diameter node
must first decrypt the content of the Encrypted-Data AVP in order to
evaluate the AVPs carried in the message. In case that a Diameter
node is unable to understand the Encrypted-Data AVP and ignores the
AVP then two possible outcomes are possible: First, if the encrypted
AVPs are optional then their content is not considered by the
receiving Diameter server without any indication to the sender that
they have not been processes. Worse, in the second case when the
encrypted AVPs are mandatory to be processed then the receiving
Diameter node will return an error that may not inform the sender
about the failure to decrypt the Encrypted-Data AVP. Consequently,
the usage of the Encrypted-Data AVP may require changes to the ABNF
definition of a Diameter application.
If a receiver detects that the contents of the Encrypted-Data AVP is
invalid, it SHOULD return the new Result-Code AVP value defined in
Section 4.
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2.3. Definition of the 'End Point'
Although this specification claims to introduce the end-to-end
security into Diameter, the definition who actually is the 'end
point' is not obvious. The 'end point' does not need to be the
original Diameter request or answer originator but the Diameter node
that inserts the Signed-Data or the Encrypted-Data AVPs into the
Diameter message. The node can be the request or answer originator
or a proxy agent. Use of proxy agents doing the 'end-to-end'
security on behalf of other nodes mimics the deployments where site-
to-site VPNs are used.
3. AVP Encoding
3.1. Signed-Data AVP
The Signed-Data AVP (AVP Code TBD1) is of type Grouped and utilizes
the JSON Web signature (JWS) mechanism defined in
[I-D.ietf-jose-json-web-signature]. The JWS payload is then encoded
into the Signed-Data AVP:
Signed-Data ::= < AVP Header: TBD1 >
{ JWS-Header }
* { JWS-AVP-Payload }
{ JWS-Signature }
* [ AVP ]
3.2. JWS-Header AVP
The JWS-Header AVP (AVP Code TBD2) is of type UTF8String and contains
the JSON Web Signature Header. The contents of the AVP follow the
rules for the header found in [I-D.ietf-jose-json-web-signature],
which implies the required IANA registries are also defined by JSON
documents.
JWS-Header ::= < AVP Header: TBD2 >
{ Header-Parameters }
* [ AVP ]
The "alg" is the only REQUIRED Header Parameter for the signature
purposes. The "typ" and "kid" Header Parameters are also
RECOMMENDED.
3.3. Header-Parameters AVP
The Header-Parameters AVP (AVP Code TBD3) is of type UTF8String and
contains the JSON Header Parameter Name and its value as described in
[I-D.ietf-jose-json-web-signature]. The encoding (textual) also
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follows [I-D.ietf-jose-json-web-signature]. Differing from the JSON
specifications the parameter names and values are not BASE64 encoded
but in their original UTF-8 representation format.
3.4. JWS-AVP-Payload AVP
The JWS-AVP-Payload AVP (AVP Code TBD4) is of type OctetString and
contains both an AVP Code and a hash of the entire AVP identified by
the AVP Code. The first four octets contain the AVP Code in a
network byte order followed by the hash octets. The length of the
hash octets depends on the used hash algorithm.
3.5. JWS-Signature AVP
The JWS-Signature AVP (AVP Code TBD5) is of type OctetString and
contains the signature calculated over the array of complete JWS-AVP-
Payload AVPs (including AVP header fields etc) in the order they
appear in the Signed-Data AVP. The length of the signature octets
depends on the used signature algorithm.
3.6. Encrypted-Data AVP
The Encrypted-Data AVP (AVP Code TBD6) is of type Grouped and
utilizes the JSON Web Encryption (JWE) mechanism defined in
[I-D.ietf-jose-json-web-encryption]. The JWE payload is then encoded
into the Encrypted-Data AVP:
Encrypted-Data ::= < AVP Header: TBD1 >
{ JWE-Header }
{ JWE-Enc-Key }
[ JWE-Init-Vec ]
{ JWE-AVP-Ciphertext }
* [ AVP ]
3.7. JWE-Header AVP
The JWE-Header AVP (AVP Code TBD7) is of type UTF8String and contains
the JSON Web Encryption Header. The contents of the AVP follow the
rules for the header found in [I-D.ietf-jose-json-web-encryption],
which implies the required IANA registries are also defined by JSON
documents.
JWE-Header ::= < AVP Header: TBD7 >
{ Header-Parameters }
* [ AVP ]
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The "alg" and "enc" are the REQUIRED Header Parameter for the
encryption purposes. The "typ" and "kid" Header Parameters are also
RECOMMENDED.
3.8. JWE-Enc-Key AVP
The JWE-Enc-Key AVP (AVP Code TBD8) is of type OctetString and
contains the JWE Encrypted Key in its binary format.
3.9. JWE-Init-Vec AVP
The JWE-Init-Vec AVP (AVP Code TBD9) is of type OctetString and
contains the JWE Initialization Vector in its binary format.
3.10. JWE-AVP-Ciphertext AVP
The JWE-AVP-Ciphertext AVP (AVP Code TBD10) is of type OctetString
and contains the encrypted AVPs. The encrypted AVPs are first
concatenated into one large plaintext octet blob and then encrypted
as a whole. The length of the ciphertext depends on the used
algorithm and encrypted AVPs. The plaintext to be encrypted is never
BASE64 encoded but MAY be compressed if a "zip" parameter was
included in the JWE Header.
4. Result-Code AVP Values
This section defines new Diameter result code values for usage with
Diameter applications.
4.1. Transient Failures
Errors that fall within the transient failures category are used to
inform a peer that the request could not be satisfied at the time it
was received, but MAY be able to satisfy the request in the future.
DIAMETER_KEY_UNKNOWN (TBD11)
This error code is returned when a Signed-Data or an Encrypted-
Data AVP is received that was generated using a key that cannot be
found in the key store. This error may, for example, be caused if
one of the endpoints of an end-to-end security association lost a
previously agreed upon key, perhaps as a result of a reboot. To
recover a new end-to-end key establishment procedure may need to
be invoked.
DIAMETER_HEADER_NAME_ERROR (TBD12)
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This error code is returned when a Header Parameter Name is not
understood in the JWS-Header AVP or in the JWE-Header AVP.
4.2. Permanent Failures
Errors that fall within the permanent failures category are used to
inform the peer that the request failed, and should not be attempted
again.
DIAMETER_DECRYPTION_ERROR (TBD13)
This error code is returned when an Encrypted-Data AVP is received
and the decryption fails for an unknown reason.
DIAMETER_SIGNATURE_ERROR (TBD14)
This error code is returned when a Signed-Data AVP is received and
the verification fails for an unknown reason.
5. IANA Considerations
IANA is requested to allocate AVP codes for the following AVPs:
+------------------------------------------------------------------+
| AVP Section |
|AVP Name Code Defined Data Type |
+------------------------------------------------------------------+
|Signed-Data TBD1 3.1 Grouped |
|JWS-Header TBD2 3.x Grouped |
|JWS-AVP-Paylaod TBD3 3.x OctetString |
|JSW-Signature TBD4 3.x OctetString |
|Header-Parameters TBD5 3.x UTF8String |
|Encrypted-Data TBD6 3.x Grouped |
|JWE-Header TBD7 3.x Grouped |
|JWE-Enc-Key TBD8 3.x OctetString |
|JWE-Init-Vec TBD9 3.x OctetString |
|JWE-AVP-Ciphertext TBD10 3.x OctetString |
+------------------------------------------------------------------+
This specification additionally defines a few Result-Code AVP values,
see Section 4.
6. Security Considerations
The purpose of this document is to offer end-to-end security
mechanisms for calculating keyed message digest, for signing, and for
encryption of Diameter AVPs.
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An intermediate Diameter agent that for a reason or other reorders
the AVPs within the Signed-Data AVP may cause the signature
verification fail even if no AVP was actually tampered.
7. Acknowledgements
We would like to thank the authors of [I-D.ietf-aaa-diameter-e2e-sec]
for their work on CMS end-to-end security for Diameter. Their
document inspired us.
8. References
8.1. Normative References
[I-D.ietf-jose-json-web-encryption]
Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
draft-ietf-jose-json-web-encryption-40 (work in progress),
January 2015.
[I-D.ietf-jose-json-web-signature]
Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", draft-ietf-jose-json-web-signature-41
(work in progress), January 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733,
DOI 10.17487/RFC6733, October 2012,
<http://www.rfc-editor.org/info/rfc6733>.
8.2. Informational References
[I-D.ietf-aaa-diameter-e2e-sec]
Calhoun, P., "Diameter End-2-End Security Extension",
2001.
[RFC5866] Sun, D., Ed., McCann, P., Tschofenig, H., Tsou, T., Doria,
A., and G. Zorn, Ed., "Diameter Quality-of-Service
Application", RFC 5866, DOI 10.17487/RFC5866, May 2010,
<http://www.rfc-editor.org/info/rfc5866>.
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Authors' Addresses
Jouni Korhonen
Broadcom Ltd.
3151 Zanker Road
CA 95134
US
Email: jouni.nospam@gmail.com
Hannes Tschofenig
ARM Ltd.
Email: Hannes.Tschofenig@gmx.de
URI: http://www.tschofenig.priv.at
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