draft-ietf-perc-dtls-tunnel-09.txt   draft-ietf-perc-dtls-tunnel-10.txt 
Network Working Group P. Jones Network Working Group P. Jones
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Informational P. Ellenbogen Intended status: Informational P. Ellenbogen
Expires: 15 December 2021 Princeton University Expires: 28 March 2022 Princeton University
N. Ohlmeier N. Ohlmeier
8x8, Inc. 8x8, Inc.
13 June 2021 24 September 2021
DTLS Tunnel between a Media Distributor and Key Distributor to DTLS Tunnel between a Media Distributor and Key Distributor to
Facilitate Key Exchange Facilitate Key Exchange
draft-ietf-perc-dtls-tunnel-09 draft-ietf-perc-dtls-tunnel-10
Abstract Abstract
This document defines a DTLS tunneling protocol for use in multimedia This document defines a protocol for tunneling DTLS traffic in
conferences that enables a Media Distributor to facilitate key multimedia conferences that enables a Media Distributor to facilitate
exchange between an endpoint in a conference and the Key Distributor. key exchange between an endpoint in a conference and the Key
The protocol is designed to ensure that the keying material used for Distributor. The protocol is designed to ensure that the keying
hop-by-hop encryption and authentication is accessible to the Media material used for hop-by-hop encryption and authentication is
Distributor, while the keying material used for end-to-end encryption accessible to the Media Distributor, while the keying material used
and authentication is inaccessible to the Media Distributor. for end-to-end encryption and authentication is inaccessible to the
Media Distributor.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 15 December 2021. This Internet-Draft will expire on 28 March 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used In This Document . . . . . . . . . . . . . . 3 2. Conventions Used In This Document . . . . . . . . . . . . . . 3
skipping to change at page 2, line 36 skipping to change at page 2, line 39
6.3. UnsupportedVersion Message . . . . . . . . . . . . . . . 12 6.3. UnsupportedVersion Message . . . . . . . . . . . . . . . 12
6.4. MediaKeys Message . . . . . . . . . . . . . . . . . . . . 12 6.4. MediaKeys Message . . . . . . . . . . . . . . . . . . . . 12
6.5. TunneledDtls Message . . . . . . . . . . . . . . . . . . 13 6.5. TunneledDtls Message . . . . . . . . . . . . . . . . . . 13
6.6. EndpointDisconnect Message . . . . . . . . . . . . . . . 13 6.6. EndpointDisconnect Message . . . . . . . . . . . . . . . 13
7. Example Binary Encoding . . . . . . . . . . . . . . . . . . . 13 7. Example Binary Encoding . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
11. Normative References . . . . . . . . . . . . . . . . . . . . 16 11. Normative References . . . . . . . . . . . . . . . . . . . . 16
12. Informative References . . . . . . . . . . . . . . . . . . . 17 12. Informative References . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
An objective of Privacy-Enhanced RTP Conferencing (PERC) [RFC8871] is An objective of Privacy-Enhanced RTP Conferencing (PERC) [RFC8871] is
to ensure that endpoints in a multimedia conference have access to to ensure that endpoints in a multimedia conference have access to
the end-to-end (E2E) and hop-by-hop (HBH) keying material used to the end-to-end (E2E) and hop-by-hop (HBH) keying material used to
encrypt and authenticate Real-time Transport Protocol (RTP) [RFC3550] encrypt and authenticate Real-time Transport Protocol (RTP) [RFC3550]
packets, while the Media Distributor has access only to the HBH packets, while the Media Distributor has access only to the HBH
keying material for encryption and authentication. keying material for encryption and authentication.
[RFC EDITOR: References to RFC 6347 can be changed to the RFC for
DTLS 1.3 if available.]
This specification defines a tunneling protocol that enables the This specification defines a tunneling protocol that enables the
Media Distributor to tunnel DTLS [RFC6347] messages between an Media Distributor to tunnel DTLS [RFC6347] messages between an
endpoint and the Key Distributor, thus allowing an endpoint to use endpoint and a Key Distributor, thus allowing an endpoint to use
DTLS-SRTP [RFC5764] for establishing encryption and authentication DTLS-SRTP [RFC5764] for establishing encryption and authentication
keys with the Key Distributor. keys with the Key Distributor.
The tunnel established between the Media Distributor and Key The tunnel established between the Media Distributor and Key
Distributor is a TLS [RFC5246] connection that is established before Distributor is a TLS [RFC8446] connection that is established before
any messages are forwarded by the Media Distributor on behalf of the any messages are forwarded by the Media Distributor on behalf of
endpoint. DTLS packets received from the endpoint are encapsulated endpoints. DTLS packets received from an endpoint are encapsulated
by the Media Distributor inside this tunnel as data to be sent to the by the Media Distributor inside this tunnel as data to be sent to the
Key Distributor. Likewise, when the Media Distributor receives data Key Distributor. Likewise, when the Media Distributor receives data
from the Key Distributor over the tunnel, it extracts the DTLS from the Key Distributor over the tunnel, it extracts the DTLS
message inside and forwards the DTLS message to the endpoint. In message inside and forwards the DTLS message to the endpoint. In
this way, the DTLS association for the DTLS-SRTP procedures is this way, the DTLS association for the DTLS-SRTP procedures is
established between the endpoint and the Key Distributor, with the established between an endpoint and the Key Distributor, with the
Media Distributor simply forwarding packets between the two entities Media Distributor forwarding DTLS messages between the two entities
and having no visibility into the confidential information exchanged. via the established tunnel to the Key Distributor and having no
visibility into the confidential information exchanged.
Following the existing DTLS-SRTP procedures, the endpoint and Key Following the existing DTLS-SRTP procedures, the endpoint and Key
Distributor will arrive at a selected cipher and keying material, Distributor will arrive at a selected cipher and keying material,
which are used for HBH encryption and authentication by both the which are used for HBH encryption and authentication by both the
endpoint and the Media Distributor. However, since the Media endpoint and the Media Distributor. However, since the Media
Distributor would not have direct access to this information, the Key Distributor would not have direct access to this information, the Key
Distributor explicitly shares the HBH key information with the Media Distributor explicitly shares the HBH key information with the Media
Distributor via the tunneling protocol defined in this document. Distributor via the tunneling protocol defined in this document.
Additionally, the endpoint and Key Distributor will agree on a cipher Additionally, the endpoint and Key Distributor will agree on a cipher
for E2E encryption and authentication. The Key Distributor will for E2E encryption and authentication. The Key Distributor will
transmit keying material to the endpoint for E2E operations, but will transmit keying material to the endpoint for E2E operations, but will
not share that information with the Media Distributor. not share that information with the Media Distributor.
By establishing this TLS tunnel between the Media Distributor and Key By establishing this TLS tunnel between the Media Distributor and Key
Distributor and implementing the protocol defined in this document, Distributor and implementing the protocol defined in this document,
it is possible for the Media Distributor to facilitate the it is possible for the Media Distributor to facilitate the
establishment of a secure DTLS association between an endpoint and establishment of a secure DTLS association between an endpoint and
the Key Distributor in order for the endpoint to receive E2E and HBH the Key Distributor in order for the endpoint to generate E2E and HBH
keying material. At the same time, the Key Distributor can securely keying material. At the same time, the Key Distributor can securely
provide the HBH keying material to the Media Distributor. provide the HBH keying material to the Media Distributor.
2. Conventions Used In This Document 2. Conventions Used In This Document
The key words "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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
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SRTP protection profiles supported by the Media Distributor will be SRTP protection profiles supported by the Media Distributor will be
sent in a "SupportedProfiles" message when the TLS tunnel is sent in a "SupportedProfiles" message when the TLS tunnel is
initially established. The Key Distributor will use that information initially established. The Key Distributor will use that information
to select a common profile supported by both the endpoint and the to select a common profile supported by both the endpoint and the
Media Distributor to ensure that HBH operations can be successfully Media Distributor to ensure that HBH operations can be successfully
performed. performed.
As DTLS messages are received from the endpoint by the Media As DTLS messages are received from the endpoint by the Media
Distributor, they are forwarded to the Key Distributor encapsulated Distributor, they are forwarded to the Key Distributor encapsulated
inside a "TunneledDtls" message. Likewise, as "TunneledDtls" inside a "TunneledDtls" message. Likewise, as "TunneledDtls"
messages are received by the Media Distributor from the Mey messages are received by the Media Distributor from the Key
Distributor, the encapsulated DTLS packet is forwarded to the Distributor, the encapsulated DTLS packet is forwarded to the
endpoint. endpoint.
The Key Distributor will provide the SRTP [RFC3711] keying material The Key Distributor will provide the SRTP [RFC3711] keying material
to the Media Distributor for HBH operations via the "MediaKeys" to the Media Distributor for HBH operations via the "MediaKeys"
message. The Media Distributor will extract this keying material message. The Media Distributor will extract this keying material
from the "MediaKeys" message when received and use it for HBH from the "MediaKeys" message when received and use it for HBH
encryption and authentication. encryption and authentication.
5. Tunneling Procedures 5. Tunneling Procedures
The following sub-sections explain in detail the expected behavior of The following sub-sections explain in detail the expected behavior of
the endpoint, the Media Distributor, and the Key Distributor. the endpoint, the Media Distributor, and the Key Distributor.
It is important to note that the tunneling protocol described in this It is important to note that the tunneling protocol described in this
document is not an extension to TLS [RFC5246] or DTLS [RFC6347]. document is not an extension to TLS [RFC8446] or DTLS [RFC6347].
Rather, it is a protocol that transports DTLS messages generated by Rather, it is a protocol that transports DTLS messages generated by
an endpoint or Key Distributor as data inside of the TLS connection an endpoint or Key Distributor as data inside of the TLS connection
established between the Media Distributor and Key Distributor. established between the Media Distributor and Key Distributor.
5.1. Endpoint Procedures 5.1. Endpoint Procedures
The endpoint follows the procedures outlined for DTLS-SRTP [RFC5764] The endpoint follows the procedures outlined for DTLS-SRTP [RFC5764]
in order to establish the cipher and keys used for encryption and in order to establish the cipher and keys used for encryption and
authentication, with the endpoint acting as the client and the Key authentication, with the endpoint acting as the client and the Key
Distributor acting as the server. The endpoint does not need to be Distributor acting as the server. The endpoint does not need to be
aware of the fact that DTLS messages it transmits toward the Media aware of the fact that DTLS messages it transmits toward the Media
Distributor are being tunneled to the Key Distributor. Distributor are being tunneled to the Key Distributor.
The endpoint MUST include a unique identifier in the "tls-id" SDP The endpoint MUST include a unique identifier in the "tls-id" SDP
[RFC4566] attribute sent by the endpoint in both offer and answer [RFC4566] attribute in all offer and answer messages [RFC3264] that
[RFC3264] messages as per [RFC8842]. Further, the endpoint MUST it generates as per [RFC8842]. Further, the endpoint MUST include
include this same unique identifier in the "external_session_id" this same unique identifier in the "external_session_id" extension
extension [RFC8844] in the "ClientHello" message when establishing a [RFC8844] in the "ClientHello" message when establishing a DTLS
DTLS association. association.
When receiving a "external_session_id" value from the Key When receiving a "external_session_id" value from the Key
Distributor, the client MUST check to ensure that value matches the Distributor, the client MUST check to ensure that value matches the
"tls-id" value received in SDP. If the values do not match, the "tls-id" value received in SDP. If the values do not match, the
endpoint MUST consider any received keying material to be invalid and endpoint MUST consider any received keying material to be invalid and
terminate the DTLS association. terminate the DTLS association.
5.2. Tunnel Establishment Procedures 5.2. Tunnel Establishment Procedures
Either the Media Distributor or Key Distributor initiates the Either the Media Distributor or Key Distributor initiates the
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When the Media Distributor relays a DTLS message from an endpoint, When the Media Distributor relays a DTLS message from an endpoint,
the Media Distributor will include an association identifier that is the Media Distributor will include an association identifier that is
unique per endpoint-originated DTLS association. The association unique per endpoint-originated DTLS association. The association
identifier remains constant for the life of the DTLS association. identifier remains constant for the life of the DTLS association.
The Key Distributor identifies each distinct endpoint-originated DTLS The Key Distributor identifies each distinct endpoint-originated DTLS
association by the association identifier. association by the association identifier.
When processing an incoming endpoint association, the Key Distributor When processing an incoming endpoint association, the Key Distributor
MUST extract the "external_session_id" value transmitted in the MUST extract the "external_session_id" value transmitted in the
"ClientHello" message and match that against "tls-id" value the "ClientHello" message and match that against the "tls-id" value the
endpoint transmitted via SDP. If the values in SDP and the endpoint transmitted via SDP. If the values in SDP and the
"ClientHello" do not match, the DTLS association MUST be rejected. "ClientHello" do not match, the DTLS association MUST be rejected.
The process through which the "tls-id" in SDP is conveyed to the Key The process through which the "tls-id" in SDP is conveyed to the Key
Distributor is outside the scope of this document. Distributor is outside the scope of this document.
The Key Distributor MUST match the certificate fingerprint and The Key Distributor MUST match the certificate fingerprint [RFC4572]
"external_session_id" received from endpoint's "ClientHello" message and "external_session_id" received from endpoint's "ClientHello"
with the values received from the SDP transmitted by the endpoint. message with the values received from the SDP transmitted by the
It is through this process that the Key Distributor can be sure to endpoint [RFC8122]. It is through this process that the Key
deliver the correct conference key to the endpoint. Distributor can be sure to deliver the correct conference key to the
endpoint.
When sending the "ServerHello" message, the Key Distributor MUST When sending the "ServerHello" message, the Key Distributor MUST
insert its own unique identifier in the "external_session_id" insert its own unique identifier in the "external_session_id"
extension. This value MUST also be conveyed back to the client via extension. This value MUST also be conveyed back to the client via
SDP as a "tls-id" attribute. SDP as a "tls-id" attribute.
The Key Distributor MUST encapsulate any DTLS message it sends to an The Key Distributor MUST encapsulate any DTLS message it sends to an
endpoint inside a "TunneledDtls" message (see Section 6). The Key endpoint inside a "TunneledDtls" message (see Section 6). The Key
Distributor is not required to transmit all messages a given DTLS Distributor is not required to transmit all messages for a given DTLS
association through the same tunnel if more than one tunnel has been association through the same tunnel if more than one tunnel has been
established between it and a Media Distributor. established between it and the Media Distributor.
The Key Distributor MUST use the same association identifier in The Key Distributor MUST use the same association identifier in
messages sent to an endpoint as was received in messages from that messages sent to an endpoint as was received in messages from that
endpoint. This ensures the Media Distributor can forward the endpoint. This ensures the Media Distributor can forward the
messages to the correct endpoint. messages to the correct endpoint.
The Key Distributor extracts tunneled DTLS messages from an endpoint The Key Distributor extracts tunneled DTLS messages from an endpoint
and acts on those messages as if that endpoint had established the and acts on those messages as if that endpoint had established the
DTLS association directly with the Key Distributor. The Key DTLS association directly with the Key Distributor. The Key
Distributor is acting as the DTLS server and the endpoint is acting Distributor is acting as the DTLS server and the endpoint is acting
as the DTLS client. The handling of the messages and certificates is as the DTLS client. The handling of the messages and certificates is
exactly the same as normal DTLS-SRTP procedures between endpoints. exactly the same as normal DTLS-SRTP procedures between endpoints.
The Key Distributor MUST send a "MediaKeys" message to the Media The Key Distributor MUST send a "MediaKeys" message to the Media
Distributor as soon as the HBH encryption key is computed and before Distributor as soon as a HBH encryption key is computed. The
it sends a DTLS "Finished" message to the endpoint. The "MediaKeys" "MediaKeys" message includes the selected cipher (i.e. protection
message includes the selected cipher (i.e. protection profile), MKI profile), MKI [RFC3711] value (if any), SRTP master keys, and SRTP
[RFC3711] value (if any), SRTP master keys, and SRTP master salt master salt values. The Key Distributor MUST use the same
values. The Key Distributor MUST use the same association identifier association identifier in the "MediaKeys" message as is used in the
in the "MediaKeys" message as is used in the "TunneledDtls" messages "TunneledDtls" messages for the given endpoint.
for the given endpoint.
The Key Distributor uses the certificate fingerprint of the endpoint The Key Distributor uses the certificate fingerprint of the endpoint
along with the unique identifier received in the along with the unique identifier received in the
"external_session_id" extension to determine which conference a given "external_session_id" extension to determine which conference a given
DTLS association is associated. DTLS association is associated.
The Key Distributor MUST select a cipher that is supported by both The Key Distributor MUST select a cipher that is supported itself,
the endpoint and the Media Distributor to ensure proper HBH the endpoint, and the Media Distributor to ensure proper HBH
operations. operations.
When the DTLS association between the endpoint and the Key When the DTLS association between the endpoint and the Key
Distributor is terminated, regardless of which entity initiated the Distributor is terminated, regardless of which entity initiated the
termination, the Key Distributor MUST send an "EndpointDisconnect" termination, the Key Distributor MUST send an "EndpointDisconnect"
message with the association identifier assigned to the endpoint to message with the association identifier assigned to the endpoint to
the Media Distributor. the Media Distributor.
5.5. Versioning Considerations 5.5. Versioning Considerations
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If that version is not supported by the Key Distributor, the Key If that version is not supported by the Key Distributor, the Key
Distributor MUST transmit an "UnsupportedVersion" message containing Distributor MUST transmit an "UnsupportedVersion" message containing
the highest version number supported, and close the TLS connection. the highest version number supported, and close the TLS connection.
The Media Distributor MUST take note of the version received in an The Media Distributor MUST take note of the version received in an
"UnsupportedVersion" message and use that version when attempting to "UnsupportedVersion" message and use that version when attempting to
re-establish a failed tunnel connection. Note that it is not re-establish a failed tunnel connection. Note that it is not
necessary for the Media Distributor to understand the newer version necessary for the Media Distributor to understand the newer version
of the protocol to understand that the first message received is of the protocol to understand that the first message received is
"UnsupportedVersion". The Media Distributor can determine from the "UnsupportedVersion". The Media Distributor can determine from the
first two octets received what the version number is and that the first four octets received what the version number is and that the
message is "UnsupportedVersion". The rest of the data received, if message is "UnsupportedVersion". The rest of the data received, if
any, would be discarded and the connection closed (if not already any, would be discarded and the connection closed (if not already
closed). closed).
6. Tunneling Protocol 6. Tunneling Protocol
Tunneled messages are transported via the TLS tunnel as application Tunneled messages are transported via the TLS tunnel as application
data between the Media Distributor and the Key Distributor. Tunnel data between the Media Distributor and the Key Distributor. Tunnel
messages are specified using the format described in [RFC5246] messages are specified using the format described in [RFC8446]
section 4. As in [RFC5246], all values are stored in network byte section 3. As in [RFC8446], all values are stored in network byte
(big endian) order; the uint32 represented by the hex bytes 01 02 03 (big endian) order; the uint32 represented by the hex bytes 01 02 03
04 is equivalent to the decimal value 16909060. 04 is equivalent to the decimal value 16909060.
This protocol defines several different messages, each of which This protocol defines several different messages, each of which
contains the following information: contains the following information:
* Message type identifier * Message type identifier
* Message body length * Message body length
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"TunnelMessage" structure. "TunnelMessage" structure.
6.2. SupportedProfiles Message 6.2. SupportedProfiles Message
The "SupportedProfiles" message is defined as: The "SupportedProfiles" message is defined as:
uint8 SRTPProtectionProfile[2]; /* from RFC5764 */ uint8 SRTPProtectionProfile[2]; /* from RFC5764 */
struct { struct {
uint8 version; uint8 version;
SRTPProtectionProfile protection_profiles<0..2^16-1>; SRTPProtectionProfile protection_profiles<2..2^16-1>;
} SupportedProfiles; } SupportedProfiles;
This message contains this single element: This message contains this single element:
* "version": indicates the version of the protocol to use (0x00). * "version": This document specifies version 0x00.
* "protection_profiles": The list of two-octet SRTP protection * "protection_profiles": The list of two-octet SRTP protection
profile values as per [RFC5764] supported by the Media profile values as per [RFC5764] supported by the Media
Distributor. Distributor.
6.3. UnsupportedVersion Message 6.3. UnsupportedVersion Message
The "UnsupportedVersion" message is defined as follows: The "UnsupportedVersion" message is defined as follows:
struct { struct {
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} EndpointDisconnect; } EndpointDisconnect;
The fields are described as follows: The fields are described as follows:
* "association_id": An value that identifies a distinct DTLS * "association_id": An value that identifies a distinct DTLS
association between an endpoint and the Key Distributor. association between an endpoint and the Key Distributor.
7. Example Binary Encoding 7. Example Binary Encoding
The "TunnelMessage" is encoded in binary following the procedures The "TunnelMessage" is encoded in binary following the procedures
specified in [RFC5246]. This section provides an example of what the specified in [RFC8446]. This section provides an example of what the
bits on the wire would look like for the "SupportedProfiles" message bits on the wire would look like for the "SupportedProfiles" message
that advertises support for both that advertises support for both
"DOUBLE_AEAD_AES_128_GCM_AEAD_AES_128_GCM" and "DOUBLE_AEAD_AES_128_GCM_AEAD_AES_128_GCM" and
"DOUBLE_AEAD_AES_256_GCM_AEAD_AES_256_GCM" [RFC8723]. "DOUBLE_AEAD_AES_256_GCM_AEAD_AES_256_GCM" [RFC8723].
TunnelMessage: TunnelMessage:
message_type: 0x01 message_type: 0x01
length: 0x0007 length: 0x0007
SupportedProfiles: SupportedProfiles:
version: 0x00 version: 0x00
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The value 0x00 is reserved and all values in the range 0x06 to 0xFF The value 0x00 is reserved and all values in the range 0x06 to 0xFF
are available for allocation. The procedures for updating this table are available for allocation. The procedures for updating this table
are those defined as "IETF Review" in section 4.8 of [RFC8126]. are those defined as "IETF Review" in section 4.8 of [RFC8126].
The name for this registry is "Datagram Transport Layer Security The name for this registry is "Datagram Transport Layer Security
(DTLS) Tunnel Protocol Message Types for Privacy Enhanced (DTLS) Tunnel Protocol Message Types for Privacy Enhanced
Conferencing". Conferencing".
9. Security Considerations 9. Security Considerations
Since the procedures in this document relies on TLS [RFC5246] for Since the procedures in this document relies on TLS [RFC8446] for
transport security, the security considerations for TLS should be transport security, the security considerations for TLS should be
reviewed when implementing the protocol defined in this document. reviewed when implementing the protocol defined in this document.
While the tunneling protocol defined in this document does not use While the tunneling protocol defined in this document does not use
DTLS-SRTP [[RFC5764] directly, it does convey and negotiate some of DTLS-SRTP [[RFC5764] directly, it does convey and negotiate some of
the same information (e.g., protection profile data). As such, a the same information (e.g., protection profile data). As such, a
review of the security considerations found in that document may be review of the security considerations found in that document may be
useful. useful.
This document describes a means of securely exchanging keying This document describes a means of securely exchanging keying
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the protocol defined in this document, the Media Distributor has no the protocol defined in this document, the Media Distributor has no
means of gaining access to that information and therefore cannot means of gaining access to that information and therefore cannot
affect the E2E media processing function in the endpoint except to affect the E2E media processing function in the endpoint except to
present it with invalid or replayed data. That said, any entity present it with invalid or replayed data. That said, any entity
along the path that interferes with the DTLS exchange between the along the path that interferes with the DTLS exchange between the
endpoint and the Key Distributor, including a malicious Media endpoint and the Key Distributor, including a malicious Media
Distributor that is not properly authorized, could prevent an Distributor that is not properly authorized, could prevent an
endpoint from properly communicating with the Key Distributor and, endpoint from properly communicating with the Key Distributor and,
therefore, prevent successful conference participation. therefore, prevent successful conference participation.
The Key Distributor should be aware of the possibility that a
malicious Media Distributor might transmit an "EndpointDisconnect"
message to the Key Distributor when the endpoint is, in fact, still
connected.
While the Security Considerations section of [RFC8871] describes
various attacks one needs to consider with respect to the Key
Distributor and denial-of-service, use of this protocol introduces
another possible attack vector. Consider the case where a malicious
endpoint sends unsolicited DTLS-SRTP messages to a Media Distributor.
The Media Distributor will normally forward those messages to the Key
Distributor and, if found invalid, such messages only serve to
consume resources on both the Media Distributor and Key Distributor.
10. Acknowledgments 10. Acknowledgments
The author would like to thank David Benham and Cullen Jennings for The author would like to thank David Benham and Cullen Jennings for
reviewing this document and providing constructive comments. reviewing this document and providing constructive comments.
11. Normative References 11. Normative References
[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,
skipping to change at page 16, line 36 skipping to change at page 17, line 5
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122, Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005, DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>. <https://www.rfc-editor.org/info/rfc4122>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>. July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
(TLS) Protocol Version 1.2", RFC 5246, Transport Layer Security (TLS) Protocol in the Session
DOI 10.17487/RFC5246, August 2008, Description Protocol (SDP)", RFC 4572,
<https://www.rfc-editor.org/info/rfc5246>. DOI 10.17487/RFC4572, July 2006,
<https://www.rfc-editor.org/info/rfc4572>.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764, Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC5764, May 2010, DOI 10.17487/RFC5764, May 2010,
<https://www.rfc-editor.org/info/rfc5764>. <https://www.rfc-editor.org/info/rfc5764>.
[RFC8122] Lennox, J. and C. Holmberg, "Connection-Oriented Media
Transport over the Transport Layer Security (TLS) Protocol
in the Session Description Protocol (SDP)", RFC 8122,
DOI 10.17487/RFC8122, March 2017,
<https://www.rfc-editor.org/info/rfc8122>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8842] Holmberg, C. and R. Shpount, "Session Description Protocol [RFC8842] Holmberg, C. and R. Shpount, "Session Description Protocol
(SDP) Offer/Answer Considerations for Datagram Transport (SDP) Offer/Answer Considerations for Datagram Transport
Layer Security (DTLS) and Transport Layer Security (TLS)", Layer Security (DTLS) and Transport Layer Security (TLS)",
RFC 8842, DOI 10.17487/RFC8842, January 2021, RFC 8842, DOI 10.17487/RFC8842, January 2021,
<https://www.rfc-editor.org/info/rfc8842>. <https://www.rfc-editor.org/info/rfc8842>.
[RFC8844] Thomson, M. and E. Rescorla, "Unknown Key-Share Attacks on [RFC8844] Thomson, M. and E. Rescorla, "Unknown Key-Share Attacks on
Uses of TLS with the Session Description Protocol (SDP)", Uses of TLS with the Session Description Protocol (SDP)",
RFC 8844, DOI 10.17487/RFC8844, January 2021, RFC 8844, DOI 10.17487/RFC8844, January 2021,
<https://www.rfc-editor.org/info/rfc8844>. <https://www.rfc-editor.org/info/rfc8844>.
[RFC8871] Jones, P., Benham, D., and C. Groves, "A Solution
Framework for Private Media in Privacy-Enhanced RTP
Conferencing (PERC)", RFC 8871, DOI 10.17487/RFC8871,
January 2021, <https://www.rfc-editor.org/info/rfc8871>.
12. Informative References 12. Informative References
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004, RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/info/rfc3711>. <https://www.rfc-editor.org/info/rfc3711>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC8723] Jennings, C., Jones, P., Barnes, R., and A.B. Roach, [RFC8723] Jennings, C., Jones, P., Barnes, R., and A.B. Roach,
"Double Encryption Procedures for the Secure Real-Time "Double Encryption Procedures for the Secure Real-Time
Transport Protocol (SRTP)", RFC 8723, Transport Protocol (SRTP)", RFC 8723,
DOI 10.17487/RFC8723, April 2020, DOI 10.17487/RFC8723, April 2020,
<https://www.rfc-editor.org/info/rfc8723>. <https://www.rfc-editor.org/info/rfc8723>.
[RFC8871] Jones, P., Benham, D., and C. Groves, "A Solution
Framework for Private Media in Privacy-Enhanced RTP
Conferencing (PERC)", RFC 8871, DOI 10.17487/RFC8871,
January 2021, <https://www.rfc-editor.org/info/rfc8871>.
Authors' Addresses Authors' Addresses
Paul E. Jones Paul E. Jones
Cisco Systems, Inc. Cisco Systems, Inc.
7025 Kit Creek Rd. 7025 Kit Creek Rd.
Research Triangle Park, North Carolina 27709 Research Triangle Park, North Carolina 27709
United States of America United States of America
Phone: +1 919 476 2048 Phone: +1 919 476 2048
Email: paulej@packetizer.com Email: paulej@packetizer.com
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