Internet DRAFT - draft-ietf-ippm-encrypted-pdmv2
draft-ietf-ippm-encrypted-pdmv2
Internet Engineering Task Force N. Elkins
Internet-Draft Inside Products, Inc.
Intended status: Standards Track M. Ackermann
Expires: 27 September 2023 BCBS Michigan
A. Deshpande
NITK Surathkal/Google
T. Pecorella
University of Florence
A. Rashid
Politecnico di Bari
26 March 2023
IPv6 Performance and Diagnostic Metrics Version 2 (PDMv2) Destination
Option
draft-ietf-ippm-encrypted-pdmv2-03
Abstract
RFC8250 describes an optional Destination Option (DO) header embedded
in each packet to provide sequence numbers and timing information as
a basis for measurements. As this data is sent in clear-text, this
may create an opportunity for malicious actors to get information for
subsequent attacks. This document defines PDMv2 which has a
lightweight handshake (registration procedure) and encryption to
secure this data. Additional performance metrics which may be of use
are also defined.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://ameyand.github.io/PDMv2/draft-elkins-ippm-encrypted-
pdmv2.html. Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-ippm-encrypted-pdmv2/.
Discussion of this document takes place on the IP Performance
Measurement Working Group mailing list (mailto:ippm@ietf.org), which
is archived at https://mailarchive.ietf.org/arch/browse/ippm/.
Subscribe at https://www.ietf.org/mailman/listinfo/ippm/.
Source for this draft and an issue tracker can be found at
https://github.com/ameyand/PDMv2.
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Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Current Performance and Diagnostic Metrics (PDM) . . . . 3
1.2. PDMv2 Introduction . . . . . . . . . . . . . . . . . . . 4
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Registration Phase . . . . . . . . . . . . . . . . . . . 5
4.1.1. Rationale of Primary and Secondary Roles . . . . . . 5
4.1.2. Diagram of Registration Flow . . . . . . . . . . . . 5
4.2. Primary Client - Primary Server Negotiation Phase . . . . 6
4.3. Primary Server / Client - Secondary Server / Client
Registration Phase . . . . . . . . . . . . . . . . . . . 6
4.4. Secondary Client - Secondary Server communication . . . . 6
5. Security Goals . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Security Goals for Confidentiality . . . . . . . . . . . 8
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5.2. Security Goals for Integrity . . . . . . . . . . . . . . 8
5.3. Security Goals for Authentication . . . . . . . . . . . . 8
5.4. Cryptographic Algorithm . . . . . . . . . . . . . . . . . 8
6. PDMv2 Destination Options . . . . . . . . . . . . . . . . . . 9
6.1. Destinations Option Header . . . . . . . . . . . . . . . 9
6.2. Metrics information in PDMv2 . . . . . . . . . . . . . . 9
6.3. PDMv2 Layout . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Rationale for Primary Server / Primary Client . . . 18
A.1. One Client / One Server . . . . . . . . . . . . . . . . . 18
A.2. Multiple Clients / One Server . . . . . . . . . . . . . . 18
A.3. Multiple Clients / Multiple Servers . . . . . . . . . . . 19
A.4. Primary Client / Primary Server . . . . . . . . . . . . . 19
Appendix B. Sample Implementation of Registration . . . . . . . 19
B.1. Overall summary . . . . . . . . . . . . . . . . . . . . . 20
B.2. High level flow . . . . . . . . . . . . . . . . . . . . . 20
B.3. Commands used . . . . . . . . . . . . . . . . . . . . . . 20
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 21
Appendix D. Open Issues . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
1.1. Current Performance and Diagnostic Metrics (PDM)
The current PDM is an IPv6 Destination Options header which provides
information based on the metrics like Round-trip delay and Server
delay. This information helps to measure the Quality of Service
(QoS) and to assist in diagnostics. However, there are potential
risks involved transmitting PDM data during a diagnostics session.
PDM metrics can help an attacker understand about the type of machine
and its processing capabilities. Inferring from the PDM data, the
attack can launch a timing attack. For example, if a cryptographic
protocol is used, a timing attack may be launched against the keying
material to obtain the secret.
Along with this, PDM does not provide integrity. It is possible for
a Man-In-The-Middle (MITM) node to modify PDM headers leading to
incorrect conclusions. For example, during the debugging process
using PDM header, it can mislead the person showing there are no
unusual server delays.
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1.2. PDMv2 Introduction
PDMv2 adds confidentiality, integrity and authentication to PDM.
PDMv2 consists of three kinds of flows:
* Primary to Primary
* Primary to Secondary
* Secondary to Secondary
These terms are defined in Section 3. Sample topologies may be found
in Appendix 1.
This document describes the Secondary to Secondary protocol and
security requirements. The Primary to Primary and Primary to
Secondary protocol will be described in a subsequent document.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Terminology
* Primary Client (PC): An authoritative node that creates
cryptographic keys for multiple Secondary clients.
* Primary Server (PS): An authoritative node that creates
cryptographic keys for multiple Secondary servers.
* Secondary Client (SC): An endpoint node which initiates a session
with a listening port and sends PDM data. Connects to the Primary
Client to get cryptographic key material.
* Secondary Server (SS): An endpoint node which has a listening port
and sends PDM data. Connects to the Primary Server to get
cryptographic key material.
Note: a client may act as a server (have listening ports).
* Symmetric Key (K): A uniformly random bitstring as an input to the
encryption algorithm, known only to Secondary Clients and
Secondary Servers, to establish a secure communication.
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* Public and Private Keys: A pair of keys that is used in asymmetric
cryptography. If one is used for encryption, the other is used
for decryption. Private Keys are kept hidden by the source of the
key pair generator, but Public Key is known to everyone. pkX
(Public Key) and skX (Private Key). Where X can be, any client or
any server.
* Pre-shared Key (PSK): A symmetric key. Uniformly random
bitstring, shared between any client or any server or a key shared
between an entity that forms client-server relationship. This
could happen through an out-of band mechanism: e.g., a physical
meeting or use of another protocol.
* Session Key: A temporary key which acts as a symmetric key for the
whole session.
4. Protocol Flow
The protocol will proceed in 3 steps.
Step 1: Negotiation between Primary Server and Primary Client.
Step 2: Registration between Primary Server / Client and Secondary
Server / Client
Step 3: PDM data flow between Secondary Client and Secondary Server
After-the-fact (or real-time) data analysis of PDM flow may occur by
network diagnosticians or network devices. The definition of how
this is done is out of scope for this document.
4.1. Registration Phase
4.1.1. Rationale of Primary and Secondary Roles
Enterprises have many servers and many clients. These clients and
servers may be in multiple locations. It may be less overhead to
have a secure location (ex. Shared database) for servers and clients
to share keys. Otherwise, each client needs to keep track of the
keys for each server.
Please view Appendix 1 for some sample topologies and further
explanation.
4.1.2. Diagram of Registration Flow
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+-----------+ +-----------+
|Primary |<====================>|Primary |
|Client (PC)| |Server (PS)|
+-----+-----+ +-----+-----+
|| ||
|| ||
+-------------------------+ +-------------------------+
| Secondary Clients(SC's) | | Secondary Servers (SS's)|
| | | |
| +----+ +----+ +----+ | | +----+ +----+ +----+ |
| |SC1 | |SC2 |.. |SC N| |<=======>| |SS 1| |SS 2|.. |SS N| |
| +----+ +----+ +----+ | | +----+ +----+ +----+ |
| | | |
+-------------------------+ +-------------------------+
4.2. Primary Client - Primary Server Negotiation Phase
The two entities exchange a set of data to ensure the respective
identities.
They use HPKE KEM to negotiate a "SharedSecret".
4.3. Primary Server / Client - Secondary Server / Client Registration
Phase
The "SharedSecret" is shared securely:
* By the Primary Client to all the Secondary Clients under its
control. The protocol to define this will be defined in a
subsequent document.
* By the Primary Server to all the Secondary Servers under its
control. The protocol to define this will be defined in a
subsequent document.
4.4. Secondary Client - Secondary Server communication
Each Client and Server derive a "SessionTemporaryKey" by using HPKE
KDF, using the following inputs:
* The "SharedSecret".
* The 5-tuple (SrcIP, SrcPort, DstIP, DstPort, Protocol) of the
communication.
* A Key Rotation Index (Kri).
The Kri SHOULD be initialized to zero.
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The server and client initialize (separately) a pseudo-random non-
repeating sequence between 1 and 2^15-1. How to generate this
sequence is beyond the scope of this document, and does not affect
the rest of the specification. When the sequence is used fully, or
earlier if appropriate, the sender signals the other party that a key
change is necessary. This is achieved by flipping the "F bit" and
resetting the PRSEQ. The receiver increments the Kri of the sender,
and derives another SessionTemporaryKey to be used for decryption.
It shall be stressed that the two SessionTemporaryKeys used in the
communication are never the same, as the 5-tuple is reversed for the
Server and Client. Moreover, the time evolution of the respective
Kri can be different. As a consequence, each entity must maintain a
table with (at least) the following informations:
* Flow 5-tuple, Own Kri, Other Kri
An implementation might optimize this further by caching the
OwnSessionTemporaryKey (used in Encryption) and
OtherSessionTemporaryKey (used in Decryption).
5. Security Goals
As discussed in the introduction, PDM data can represent a serious
data leakage in presence of a malicious actor.
In particular, the sequence numbers included in the PDM header allows
correlating the traffic flows, and the timing data can highlight the
operational limits of a server to a malicious actor. Moreover,
forging PDM headers can lead to unnecessary, unwanted, or dangerous
operational choices, e.g., to restore an apparently degraded Quality
of Service (QoS).
Due to this, it is important that the confidentiality and integrity
of the PDM headers is maintained. PDM headers can be encrypted and
authenticated using the methods discussed in Section 5.4, thus
ensuring confidentiality and integrity. However, if PDM is used in a
scenario where the integrity and confidentiality is already ensured
by other means, they can be transmitted without encryption or
authentication. This includes, but is not limited to, the following
cases:
a) PDM is used over an already encrypted medium (For example VPN
tunnels).
b) PDM is used in a link-local scenario.
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c) PDM is used in a corporate network where there are security
measures strong enough to consider the presence of a malicious
actor a negligible risk.
5.1. Security Goals for Confidentiality
PDM data must be kept confidential between the intended parties,
which includes (but is not limited to) the two entities exchanging
PDM data, and any legitimate party with the proper rights to access
such data.
5.2. Security Goals for Integrity
PDM data must not be forged or modified by a malicious entity. In
other terms, a malicious entity must not be able to generate a valid
PDM header impersonating an endpoint, and must not be able to modify
a valid PDM header.
5.3. Security Goals for Authentication
An unauthorized party must not be able to send PDM data and must not
be able to authorize another entity to do so. The protocol to define
this will be defined in a subsequent document. Alternatively, if
authentication is done via any of the following, this requirement may
be seen to be met.
a) PDM is used over an already authenticated medium (For example,
TLS session).
b) PDM is used in a link-local scenario.
c) PDM is used in a corporate network where security measures are
strong enough to consider the presence of a malicious actor a
negligible risk.
5.4. Cryptographic Algorithm
Symmetric key cryptography has performance benefits over asymmetric
cryptography; asymmetric cryptography is better for key management.
Encryption schemes that unite both have been specified in [RFC1421],
and have been participating practically since the early days of
public-key cryptography. The basic mechanism is to encrypt the
symmetric key with the public key by joining both yields. Hybrid
public-key encryption schemes (HPKE) [RFC9180] used a different
approach that generates the symmetric key and its encapsulation with
the public key of the receiver.
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Our choice is to use the HPKE framework that incorporates key
encapsulation mechanism (KEM), key derivation function (KDF) and
authenticated encryption with associated data (AEAD). These multiple
schemes are more robust and significantly efficient than the
traditional schemes and thus lead to our choice of this framework.
6. PDMv2 Destination Options
6.1. Destinations Option Header
The IPv6 Destination Options extension header [RFC8200] is used to
carry optional information that needs to be examined only by a
packet's destination node(s). The Destination Options header is
identified by a Next Header value of 60 in the immediately preceding
header and is defined in RFC 8200 [RFC8200]. The IPv6 PDMv2
destination option is implemented as an IPv6 Option carried in the
Destination Options header.
6.2. Metrics information in PDMv2
The IPv6 PDMv2 destination option contains the following base fields:
SCALEDTLR: Scale for Delta Time Last Received
SCALEDTLS: Scale for Delta Time Last Sent
GLOBALPTR: Global Pointer
PSNTP: Packet Sequence Number This Packet
PSNLR: Packet Sequence Number Last Received
DELTATLR: Delta Time Last Received
DELTATLS: Delta Time Last Sent
PDMv2 adds a new metric to the existing PDM [RFC8250] called the
Global Pointer. The existing PDM fields are identified with respect
to the identifying information called a "5-tuple".
The 5-tuple consists of:
SADDR: IP address of the sender
SPORT: Port for the sender
DADDR: IP address of the destination
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DPORT: Port for the destination
PROTC: Upper-layer protocol (TCP, UDP, ICMP, etc.)
Unlike PDM fields, Global Pointer (GLOBALPTR) field in PDMv2 is
defined for the SADDR type. Following are the SADDR address types
considered:
a) Link-Local
b) Global Unicast
The Global Pointer is treated as a common entity over all the
5-tuples with the same SADDR type. It is initialised to the value 1
and increments for every packet sent. Global Pointer provides a
measure of the amount of IPv6 traffic sent by the PDMv2 node.
When the SADDR type is Link-Local, the PDMv2 node sends Global
Pointer defined for Link-Local addresses, and when the SADDR type is
Global Unicast, it sends the one defined for Global Unicast
addresses.
6.3. PDMv2 Layout
PDMv2 has two different header formats corresponding to whether the
metric contents are encrypted or unencrypted. The difference between
the two types of headers is determined from the Options Length value.
Following is the representation of the unencrypted PDMv2 header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Vrsn | Reserved Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Random Number |f| ScaleDTLR | ScaleDTLS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global Pointer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN This Packet | PSN Last Received |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delta Time Last Received | Delta Time Last Sent |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Following is the representation of the encrypted PDMv2 header:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Vrsn | Reserved Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Random Number |f| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ :
| Encrypted PDM Data :
: (30 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type
0x0F
8-bit unsigned integer. The Option Type is adopted from RFC 8250
[RFC8250].
Option Length
0x12: Unencrypted PDM
0x22: Encrypted PDM
8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. The options
length is used for differentiating PDM [RFC8250], unencrypted
PDMv2 and encrypted PDMv2.
Version Number
0x2
4-bit unsigned number.
Reserved Bits
12-bits.
Reserved bits for future use. They are initialised to 0 for
PDMv2.
Random Number
15-bit unsigned number.
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This is a random number with as much entropy as desired by the
implementation. The level of entropy should be clearly specified
to the user.
Flag Bit
1-bit field.
The flag bit indicates that the sender has used a new
_SessionTemporaryKey_ and the receiver should increment the Kri of
the sender and derive the same new _SessionTemporaryKey_.
Scale Delta Time Last Received (SCALEDTLR)
8-bit unsigned number.
This is the scaling value for the Delta Time Last Sent (DELTATLS)
field.
Scale Delta Time Last Sent (SCALEDTLS)
8-bit unsigned number.
This is the scaling value for the Delta Time Last Sent (DELTATLS)
field.
Global Pointer
32-bit unsigned number.
Global Pointer is initialized to 1 for the different source
address types and incremented monotonically for each packet with
the corresponding source address type.
This field stores the Global Pointer type corresponding to the
SADDR type of the packet.
Packet Sequence Number This Packet (PSNTP)
16-bit unsigned number.
This field is initialized at a random number and is incremented
monotonically for each packet of the 5-tuple.
Packet Sequence Number Last Received (PSNLR)
16-bit unsigned number.
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This field is the PSNTP of the last received packet on the
5-tuple.
Delta Time Last Received (DELTATLR)
16-bit unsigned integer.
The value is set according to the scale in SCALEDTLR.
Delta Time Last Received = (send time packet n - receive time
packet (n - 1))
Delta Time Last Sent (DELTATLS)
16-bit unsigned integer.
The value is set according to the scale in SCALEDTLS.
Delta Time Last Sent = (receive time packet n - send time packet
(n - 1))
7. Security Considerations
PDMv2 DOH can be used by an attacker to gather information about a
victim (passive attack) or to force the victim to modify its
operational parameters to comply with forged data (active attacks).
In order to mitigate these, it is important that the PDMv2 DOH is
subject to:
1) Confidentiality and
2) Integrity
with respect to an attacker.
In the following we will refer to two different "groups", that can or
cannot belong to the same operational and management domain:
1) Servers - implementing services.
2) Clients-devices willing to interact with the services offered by
Servers.
We will assume, for the sake of generalization, that the Servers are
managed by an Organization (OrgA) implementing management procedures
over them, and the Clients by a different Organization (OrgB).
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An attacker could be in the following positions:
1) External to OrgA or OrgB.
2) Inside OrgA (i.e., a Server), either because it is a legitimate-
but-curious device, or as a consequence of an attack to a device.
3) Inside OrgB (i.e., a Client), either because it is a legitimate-
but-curious device, or as a consequence of an attack to a device
Furthermore, since PDMv2 DOH encryption could consume resources
(albeit limited), it is possible to foresee a call of DoS by resource
exhaustion. Hence, it is relevant to consider a form of access
control to verify that the Server and Client belong to OrgA and OrgB
respectively. This could be a _delegated trust_.
In other terms, a Client could just want to verify that the Server
belongs to OrgA, without actually verifying the identity of the
Server.
The Authentication and Authorization of Clients and Servers is thus
delegated to the respective Organizations. In other terms, we do not
expect, or want, that a Client and a Server should be forced to
verify the respective identities (Authentication) or the permissions
to use PDMv2 (Authorization).
The simple knowledge of the secrets required by the flow is
considered sufficient to enable PDMv2. On the opposite, an
unsuccessful decryption MUST result in dropping the PDMv2 DOH without
further processing or, if configured to do so, might lead to
throttling, filtering, and/or logging the activity of the other
entity (Client or Server).
The present document specifies a methodology to enable this delegated
trust, along with the Confidentiality and Integrity requirements, in
the PDMv2 DOH.
We assume that PS and PC have verified the respective identities and
the authorization to enable PDMv2 DOH on a set of devices under their
responsibility: Secondary Servers (SS) and Secondary Clients (SC).
PS-PC
* Perform a HPKE KEM and obtain a PairMasterSecret (PMS).
* The PMS is stored securely in both PS and PC, and is NOT to be
leaked.
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* The PMS is valid only for the PC-PS pair.
In other terms, if a PS would want to establish a pair with two PCs,
it will have two different PMSs. PMS might be re-negotiated after a
given amount of time [renegotiation TBD]
* PS and PC exchange respectively the list of the SS and SC enabled
to use PDMv2. The list can be:
- A range of IP addresses, e.g.: 2001:db8:food:beef:cafe::0/80
- A list of IP addresses, e.g., [2001:db8:food::1/128,
2001:db8:food::1/128]
Note:
1) How to represent the list in a compact way is out of scope of
the present document,
2) The list could be dynamically updated.
3) Inside OrgB (i.e., a Client), either because it is a
legitimate-but-curious device, or as a consequence of an
attack to a device
* PS sends to the PC the Security Mode of Operation (SecMoP) to be
used, see below.
PS-SS and PC-SC
* Each Secondary Sever (or Client) MUST authenticate itself with the
Primary Server (or Client). This is out of scope of the present
specification.
* Each SS receives a PairServerSecret (PSS), derived using HPKE KDF,
and valid for the specific SS and the list of SCs defined above.
* Each SC receives a PairClientSecret (PCS), derived using HPKE KDF,
and valid for the specific SC and the list of SSs defined above.
Since there are multiple use-cases, we define 4 modes of operations:
* *No Protection*: The Secrets are discarded (or not even created),
and the flows do not use PDMv2. The scheme above is used only to
disseminate the list of Secondary Clients and Secondary Servers.
By sharing lists, this mode act as ACL (Access Control List) or
authorization of the secondaries.
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* *TrustedServers*: The Secondary Servers are trusted, and they do
know a secret derived by the PMS.
* *AsymmetricPoll*: One Secondary (Server or Client) must acquire a
secret from the respective Primary.
* *Identity Based Cryptography (IBC)*: IBC (RFC5091) is used to
generate a shared secret between the SS and the SC.
The *TrustedServers* MoP has the benefit of requiring no additional
steps to send and receive PDMv2 DOH, because each flow is protected
by a SessionKey that can be derived autonomously by both the SC and
the SS, without any interaction with the PS and PC, or any
negotiation between the SS and the SC.
The possible vulnerabilities of the *TrustedServers* MoP are the
following:
* Any SS can inspect the flows directed to a different SS in the
same group.
* An attack to a SS might result in compromising the security of all
the flows between all the clients and the Secondary Servers
belonging to the same group.
A possible mitigation is to split the Secondary Servers in different
sub-groups. This is a scenario similar to the one of a PC
negotiating PDMv2 access with different PSs.
The *AsymmetricPoll* MoP has the benefit of isolating each SS and
each SC. Only the SS and SC involved in a communication can decrypt
their flows.
The *IBC* MoP has the same security properties of the
*AsymmetricPoll* MoP, and the advantage of not requiring any
interaction between the Primary and the Secondary. The disadvantage
is the requirement of performing a "pairing" session negotiation
between the Secondaries.
It must be considered that, while secure, this MoP could be used to
perform a resource exhaustion attack on the PairDeviceKey
establishment. Hence, a device MUST NOT reply to an IP address that
is not in the Secondary[client, server] list, and MUST NOT reply with
negative acknowledgments (e.g., in case of an incorrect decoding).
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8. Privacy Considerations
PDMv2 greatly improves the privacy aspects of PDM by providing
encryption.
9. IANA Considerations
Option Type to be assigned by IANA [RFC2780].
10. Contributors
The authors wish to thank NITK Surathkal for their support and
assistance in coding and review. In particular Dr. Mohit Tahiliani
and Abhishek Kumar (now with Google). Thanks also to Priyanka Sinha
for her comments. Thanks to the India Internet Engineering Society
(iiesoc.in), in particular Dhruv Dhody, for providing the funding for
servers needed for protocol development.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For
Values In the Internet Protocol and Related Headers",
BCP 37, RFC 2780, DOI 10.17487/RFC2780, March 2000,
<https://www.rfc-editor.org/rfc/rfc2780>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/rfc/rfc8200>.
[RFC8250] Elkins, N., Hamilton, R., and M. Ackermann, "IPv6
Performance and Diagnostic Metrics (PDM) Destination
Option", RFC 8250, DOI 10.17487/RFC8250, September 2017,
<https://www.rfc-editor.org/rfc/rfc8250>.
11.2. Informative References
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[RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic
Mail: Part I: Message Encryption and Authentication
Procedures", RFC 1421, DOI 10.17487/RFC1421, February
1993, <https://www.rfc-editor.org/rfc/rfc1421>.
[RFC9180] Barnes, R., Bhargavan, K., Lipp, B., and C. Wood, "Hybrid
Public Key Encryption", RFC 9180, DOI 10.17487/RFC9180,
February 2022, <https://www.rfc-editor.org/rfc/rfc9180>.
Appendix A. Rationale for Primary Server / Primary Client
A.1. One Client / One Server
Let's start with one client and one server.
+------------+ Derived Shared Secret +------------+
| Client | -----------------> | Server |
+------+-----+ +------+-----+
| |
V V
Client Secret Server Secret
The Client and Server create public / private keys and derive a
shared secret. Let's not consider Authentication or Certificates at
this point.
What is stored at the Client and Server to be able to encrypt and
decrypt packets? The shared secret or private key.
Since we only have one Server and one Client, then we don't need to
have any kind of identifier for which private key to use for which
Server or Client because there is only one of each.
Of course, this is a ludicrous scenario since no real organization of
interest has only one server and one client.
A.2. Multiple Clients / One Server
So, let's try with multiple clients and one Primary server
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+------------+
| Client 1 | --------+
+------------+ |
+------------+ +--->
| Client 2 | ----------> +------------+
+------+-----+ : | Server |
: : +------+-----+
: +---->
+------------+ |
| Client n | -------+
+------+-----+
The Clients and Server create public / private keys and derive a
shared secret. Each Client has a unique private key.
What is stored at the Client and Server to be able to encrypt and
decrypt packets?
Clients each store a private key. Server stores: Client Identifier
and Private Key.
Since we only have one Server and multiple Clients, then the Clients
don't need to have any kind of identifier for which private key to
use for which Server but the Server needs to know which private key
to use for which Client. So, the Server has to store an identifier
as well as the Key.
But, this also is a ludicrous scenario since no real organization of
interest has only one server.
A.3. Multiple Clients / Multiple Servers
When we have multiple clients and multiple servers, then each not
only does the Server need to know which key to use for which Client,
but the Client needs to know which private key to use for which
Server.
A.4. Primary Client / Primary Server
Based on this rationale, we have chosen a Primary Server / Primary
Client topology.
Appendix B. Sample Implementation of Registration
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B.1. Overall summary
In the Registration phase, the objective is to generate a shared
secret that will be used in encryption and decryption during the Data
Transfer phase. We have adopted a Primary-Secondary architecture to
represent the clients and servers (see Section 4.1.1). The primary
server and primary client perform Key Encapsulation Mechanism (KEM)
[RFC9180] to generate a primary shared secret. The primary server
shares this secret with secondary servers, whereas the primary client
performs Key Derivation Function (KDF) [RFC9180] to share client-
specific secrets to corresponding secondary clients. During the Data
Transfer phase, the secondary servers generate the client-specific
secrets on the arrival of the first packet from the secondary client.
B.2. High level flow
The following steps describe the protocol flow:
1. Primary client initiates a request to the primary server. The
request contains a list of available ciphersuites for KEM, KDF,
and AEAD.
2. Primary server responds to the primary client with one of the
available ciphersuites and shares its public key.
3. Primary client generates a secret and its encapsulation. The
primary client sends the encapsulation and a salt to the primary
server. The salt is required during KDF in the Data Transfer
phase.
4. Primary Server generates the secret with the help of the
encapsulation and responds with a status message.
5. Primary server shares this key with secondary servers over TLS.
6. Primary client generates the client-specific secrets with the
help of KDF by using the info parameter as the Client IP address.
The primary client shares these keys with the corresponding
secondary clients over TLS.
B.3. Commands used
Two commands are used between the primary client and the primary
server to denote the setup and KEM phases. Along with this, we have
a "req / resp" to indicate whether it's a request or response.
Between primary and secondary entities, we have one command to denote
the sharing of the secret keys.
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Appendix C. Change Log
Note to RFC Editor: if this document does not obsolete an existing
RFC, please remove this appendix before publication as an RFC.
Appendix D. Open Issues
Note to RFC Editor: please remove this appendix before publication as
an RFC.
Authors' Addresses
Nalini Elkins
Inside Products, Inc.
Email: nalini.elkins@insidethestack.com
Michael Ackermann
BCBS Michigan
Email: mackermann@bcbsm.com
Ameya Deshpande
NITK Surathkal/Google
Email: ameyanrd@gmail.com
Tommaso Pecorella
University of Florence
Email: tommaso.pecorella@unifi.it
Adnan Rashid
Politecnico di Bari
Email: adnan.rashid@poliba.it
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