LURK Extension version 1 for (D)TLS 1.2 and (D)TLS 1.1 Authentication
draft-mglt-lurk-tls12-00
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| Author | Daniel Migault | ||
| Last updated | 2018-02-09 | ||
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draft-mglt-lurk-tls12-00
LURK WG D. Migault, Ed.
Internet-Draft Ericsson
Intended status: Standards Track February 9, 2018
Expires: August 13, 2018
LURK Extension version 1 for (D)TLS 1.2 and (D)TLS 1.1 Authentication
draft-mglt-lurk-tls12-00
Abstract
This document describes the LURK Extension 'tls12' which enables
interactions between a LURK Client and a LURK Server in a context of
authentication with (D)TLS 1.1 and (D)TLS 1.2.
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
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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 August 13, 2018.
Copyright Notice
Copyright (c) 2018 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
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology and Acronyms . . . . . . . . . . . . . . . . . . 4
4. LURK Header . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. rsa_master . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Request Payload . . . . . . . . . . . . . . . . . . . . . 6
5.1.1. PFS-PRFA . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Response Payload . . . . . . . . . . . . . . . . . . . . 7
5.3. LURK Client Behavior . . . . . . . . . . . . . . . . . . 8
5.4. LURK Server Behavior . . . . . . . . . . . . . . . . . . 8
6. rsa_extended_master . . . . . . . . . . . . . . . . . . . . . 9
6.1. Request Payload . . . . . . . . . . . . . . . . . . . . . 9
6.2. Response Payload . . . . . . . . . . . . . . . . . . . . 10
6.3. LURK Client Behavior . . . . . . . . . . . . . . . . . . 10
6.4. LURK Server Behavior . . . . . . . . . . . . . . . . . . 10
7. ecdhe . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Request Payload . . . . . . . . . . . . . . . . . . . . . 10
7.2. Response Payload . . . . . . . . . . . . . . . . . . . . 12
7.3. LURK Client Behavior . . . . . . . . . . . . . . . . . . 12
7.4. LURK Server Behavior . . . . . . . . . . . . . . . . . . 12
8. capabilities . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Request Payload . . . . . . . . . . . . . . . . . . . . . 13
8.2. Response Payload . . . . . . . . . . . . . . . . . . . . 13
8.3. LURK Client Behavior . . . . . . . . . . . . . . . . . . 15
8.4. LURK Server Behavior . . . . . . . . . . . . . . . . . . 15
9. ping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Request Payload . . . . . . . . . . . . . . . . . . . . . 15
9.2. Response Payload . . . . . . . . . . . . . . . . . . . . 15
9.3. LURK Client Behavior . . . . . . . . . . . . . . . . . . 15
9.4. LURK Server Behavior . . . . . . . . . . . . . . . . . . 16
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10.1. RSA . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.2. ECDHE . . . . . . . . . . . . . . . . . . . . . . . . . 17
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
13.1. Normative References . . . . . . . . . . . . . . . . . . 20
13.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Example of LURK Exchanges . . . . . . . . . . . . . 21
A.1. LURK/TLS RSA Master Secret . . . . . . . . . . . . . . . 22
A.2. LURK/TLS RSA Extended Master Secret . . . . . . . . . . . 23
A.3. LURK/TLS ECDHE Signature . . . . . . . . . . . . . . . . 25
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Requirements notation
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 [RFC2119].
2. Introduction
This document describes the LURK Extension for TLS 1.1 and TLS 1.2 so
the LURK Server can implement a Cryptographic Service in a TLS 1.1
[RFC4346], , DTLS 1.1 [RFC4347], a TLS 1.2 [RFC5246] and DTLS 1.2
[RFC6347] context.
More specifically, the LURK Server will be in charge of performing
the cryptographic operations associated to the private key of the TLS
Server, while other aspects of the termination of the TLS session is
handled by other services in the same administrative domain or in a
different administrative domain. Most Cryptographic Operations are
related to the TLS authentication and the current document limits the
Cryptographic Operations to the following authentication methods: RSA
and ECDHE_RSA defined in [RFC5246], [RFC6347] as well as ECDHE_ECDSA
defined in [RFC4492].
A more detailed description of some use cases foreseen in a TLS
context can be found in [I-D.mglt-lurk-tls-use-cases].
HTTPS delegation has been the main concern of the Content Delivery
Networks Interconnection (cdni) Working Group and several mechanisms
have been designed to delegate the load from an upstream entity to a
downstream entity. Entities can be of different nature and may
designated differently according to the context. Typically
designations includes Content Owner, CDN Provider, Domain Name Owner
for example. [I-D.fieau-cdni-https-delegation] provides a details
comparison of the various mechanisms applies to the CDN
Interconnection, and the remaining of this section positions these
mechanisms at a very high level view.
STAR [I-D.ietf-acme-star], [I-D.sheffer-acme-star-request] describes
a methods where the domain name owner or the content owner
orchestrates the refreshing process between a CA and the CDN
(terminating the TLS session). The CDN refreshes regularly and
automatically its certificates using [I-D.ietf-acme-acme], which
allows the use of short term certificates.
Delegated credentials [I-D.rescorla-tls-subcerts] consists having a
certificate that enables the servers to generates some "delegated
credentials".
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STAR and "delegated credentials" both require some changes performed
by the CA - new certificate type for the delegated credentials and
new interfaces for the delegated and delegating entity for STAR. In
both case the TLS Client authenticates the delegated entity. While
STAR does not require changes on the TLS Client, the "delegated
credential" solution does. In both cases, the delegation is
controlled by limiting in time (7 days), which is also the limit of
use of a stolen key or a rogue server. Such delegation provides a
high scalability of the architecture and prevents additional delays
when a TLS session is established.
The LURK Architecture [I-D.mglt-lurk-lurk] and the LURK Extension
'tls12' do not proceed to the delegation of the HTTPS delegation by
delegating the entire TLS termination. Instead, the TLS termination
is split into sub services, for example one associated to the
networking part and one associated to the cryptographic operation.
While micro services associated to the networking part are delegated,
the micro service associated to the cryptographic operation may not
be delegated. As a result, LURK Architecture is focused on the
protection of the Cryptographic Material and prevents leakage of the
Cryptographic Material for example by avoiding node exposed to the
Internet to host the Cryptographic Material. In addition, LURK
provides means to instantaneously suspend the delegation with a
suspicious node. On the other hand the LURK Extension 'tls12'
introduces some latency, and is not as scalable as STAR or delegated
credential solutions.
The LURK Extension 'tls12' is seen as a complementary to the STAR and
"delegated credentials". The LURK Extension 'tls12' is a back end
solution that does not require any modifications from TLS Client or
the CA. It is also aimed at protecting the Cryptographic Material.
LURK may also be deployed within an administrative domain in order to
to provide a more controled deployment of TLS Servers.
3. Terminology and Acronyms
This document re-uses the terminology defined in
[I-D.mglt-lurk-lurk].
4. LURK Header
LURK / TLS 1.2 is a LURK Extension that introduces a new designation
"tls12". This document assumes that Extension is defined with
designation set to "tls12" and version set to 1. The LURK Extension
extends the LURKHeader structure defined in [I-D.mglt-lurk-lurk] as
follows:
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enum {
tls12 (1), (255)
} Designation;
enum {
capabilities (0), ping (1), rsa_master (2),
rsa_extended_master (3), ecdhe (4), (255)
}TLS12Type;
enum {
// generic values reserved or aligned with the
// LURK Protocol
request (0), success (1), undefined_error (2),
invalid_payload_format (3),
// code points for rsa authentication
invalid_key_id_type (4), invalid_key_id (5),
invalid_tls_version (6), invalid_tls_random (7), invalid_prf (8),
invalid_encrypted_premaster (9)
//code points for ecdhe authentication
invalid_ec_type (10), invalid_ec_basistype (11),
invalid_ec_curve (12), invalid_ec_point_format (13),
invalid_poo_prf (138), invalid_poo (139), (255)
}TLS12Status
struct {
Designation designation = "tls12";
int8 version = 1;
} Extension;
struct {
Extension extension;
select( Extension ){
case ("tls12", 1):
TLS12Type;
} type;
select( Extension ){
case ("tls12", 1):
TLS12Status;
} status;
uint64 id;
unint32 length;
} LURKHeader;
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5. rsa_master
A exchange of type "rsa_master" enables the LURK Client to delegate
the RSA Key Exchange and authentication as defined in [RFC5246]. The
LURK Server returns the master secret.
5.1. Request Payload
A rsa_master request payload has the following structure:
enum {
sha256_32 (0), (255)
}KeyPairIdType;
struct {
KeyPairIdType type;
opaque data; // length defined by the type
} KeyPairID;
enum{
sha256_null (0), sha256_sha256 (1) (255)
} PRFAlgorithm
struct {
KeyPairID key_id;
Random client_random; // see RFC5246 section 7.4.1.2
Random server_random;
ProtocolVersion tls_version; // see RFC5246 section 6.2.1
PRFAlgorithm prf; // see RFC5246 section 6.1
} TLS12Base;
struct {
TLS12Base base;
EncryptedPreMasterSecret pre_master;
// see RFC5246 section 7.4.7.1
// Length depends on the key.
} TLS12RSAMasterRequestPayload;
key_id The identifier of the RSA key. This document defines
sha256_32 format which takes the 32 first bits of the hash of the
public key using sha256.
prf the set of pseudo random functions used. This document
considers two distinct Pseudo Random Function Algorithm (PRFA):
The Master Secret PRFA (MS-PRFA) used to generate the master
secret as defined in [RFC5246] Section 6.1 and the Perfect Forward
Secrecy PRFA (PFS-PRFA) used to implement PFS. This
representation used in this document is MS-PRFA_PFS-PRFA.
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client_random The random value associated to the TLS Client as
defined in [RFC5246] Section 7.4.1.2.
server_random The random value associated to the TLS Server as
defined in [RFC5246] Section 7.4.1.2.
tls_version The TLS version set by the TLS Client as defined in
[RFC5246] Section 6.2.1.
EncryptedPreMasterSecret The encrypted master secret as defined in
[RFC5246] Section 7.4.7.1.
5.1.1. PFS-PRFA
This document defines a mechanism based on a one way functions to
prevent an attacker to send a request to the LURK Server to replay an
observed TLS handshake. More explicitly, this document assumes that
the ServerHello.random of the TLS exchange is derived from the
server_random of the LURK exchange as defined below:
### with PFS-PRFA != "null"
gmt_unix_time = server_random[0..3];
ServerHello.random = PFS-PRFA( server_random + "tls12 pfs" );
ServerHello.random[0..3] = gmt_unix_time;
### with PFS-PRFA == "null"
ServerHello.random = server_random ;
The server_random MUST follow the structure of [RFC5246] section
7.4.1.2 which carry the gmt_unix_time in the first four bytes.
The operation MUST be performed by the LURK Server as well as the TLS
Server, upon receiving the master secret or the signature of the
ecdhe_params from the LURK Client. When PFS-PRFA is different from
"null", then the server_random cannot be derived from the observed
ServerHello.random, which prevents the handshake to be replayed.
Importantly a LURK Server implementing PFS MUST NOT enable the "null"
PFS-PRFA.
5.2. Response Payload
The "rsa_master" response payload contains the master secret and has
the following structure:
struct {
opaque master[0..47];
} TLS12RSAMasterResponsePayload;
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5.3. LURK Client Behavior
A rsa_master request is sent so the LURK Server can derive the master
secret used by the TLS session. Upon receipt of the master_secret
the Edge Server can generate the session keys and finish the TLS key
exchange protocol.
5.4. LURK Server Behavior
Upon receipt of a rsa_master request, the LURK Server proceeds
according to the following steps:
(1) Checking TLS12Base:
(a) The LURK Server checks the RSA key pair is available
(key_id). If the format of the key pair identifier is not
understood, an "invalid_key_id_type" error is returned. If
the designated key pair is not available an
"invalid_key_id" error is returned.
(b) The LURK Server checks the length of the encrypted
premaster secret and so the length of the payload. In case
of length mismatch and "invalid_payload_format" error is
returned. Note that the length can be derived from the
public key, so the error only reveals public information.
(c) If the TLS version is not supported or is different from
TLS 1.1 or TLS 1.2 an "invalid_tls_version" error is
returned.
(d) The LURK Server MAY check the format of the random, and
more specifically checks the gmt_unix_time associated to
the random is acceptable. Otherwise it SHOULD return an
"invalid_tls_random" error. The value of the time window
is implementation dependent and SHOULD be a parameters and
SHOULD be configurable.
(2) The LURK Server checks the prf. If it does not support the PRF,
an "invalid_prf" error is returned.
(3) The LURK Server computes the necessary ServerHello.random from
the server_random when applicable as described in Section 5.1.1.
(4) The LURK Server decrypts the encrypted premaster secret as
described in [RFC5246] section 7.4.7.1. When a PKCS1.5 format
error is detected, or a mismatch between the TLS versions
provided as input and the one indicated in the encrypted
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premaster secret, the Key Server returns a randomly generated
master secret.
(5) If the pre master is appropriately decrypted, then the master
secret is computed as described in [RFC5246] section 8.1 using
the MS-PRFA, the client_random, and the server_random provided
by the LURK Client.
(6) The LURK Server returns a master secret in a
TLS12RSAMasterResponsePayload.
(7) Error are expected to provide the LURK Client an indication of
the cause that resulted in the error. When an error occurs the
LURK Server MAY ignore the request, or provide more generic
error codes such as "undefined_error" or "invalid_format".
6. rsa_extended_master
A exchange of type "rsa_extended_master" enables the LURK Client to
delegate the RSA Key Exchange and authentication. The LURK Server
returns the extended master secret as defined in [RFC7627].
6.1. Request Payload
The "rsa_extended_master" payload request has the following
structure:
struct{
KeyPairID key_id
ProtocolVersion tls_version // see RFC5246 section 6.2.1
PRFAlgorithm prf // see RFC5246 section 6.1
EncryptedPreMasterSecret pre_master
// see RFC5246 section 7.4.7.1
opaque session_hash<2...2^16-2>
}TLS12ExtendedMasterRSARequestPayload;
key_id, tls_version, prf, pre_master are defined in Section 5.1.
session_hash The hash of the TLS handshake session as described in
[RFC7627] section 3.
Note that as the server_random is not provided by the LURK Client,
PFS mechanisms does not apply here, and only the PFS-PRFA "null" can
be used.
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6.2. Response Payload
rsa_extended_master response payload has a similar structure as the
rsa_master response payload Section 5.2.
6.3. LURK Client Behavior
A rsa_extended_master request is sent so the LURK Server can derive
the master secret used by the TLS session. Upon receipt of the
master_secret the Edge Server can generate the session keys and
finish the TLS key exchange protocol.
6.4. LURK Server Behavior
The LURK Server proceeds as described in Section 5.4 except that the
generation of the extended master is processed as described in
[RFC7627].
7. ecdhe
A exchange of type "ecdhe" enables the LURK Client to delegate the
ECDHE_RSA [RFC5246] or the ECDHE_ECDSA [RFC4492] authentication.
7.1. Request Payload
The "ecdhe" request payload has the following structure:
enum { null(0), sha256_128(1), sha256_256(2),
(255) }POOPRF
struct {
POOPRF poo_prf;
select( poo_prf) {
case ( "null" ):
case ( "sha256_128" or "sha256_256" ):
ECPoint rG; //RFC4492 section 5.4
ECPoint tG;
}
} TLS12POOParams;
struct {
TLS12Base base;
ServerECDHParams ecdhe_params; // RFC4492 section 5.4
POOParams poo_params;
} TLS12ECDHERequestPayload;
base is defined in Section 5.1.
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ecdhe_params contains the ECDHE public key - also noted bG - and
associated domain parameters as defined in [RFC4492] section 5.4.
In the notation bG for the ECDHE public, b is a random secret
generated by the LURK Client and G the base point of the curve.
The base is explicitly specified in the ECParameters structure for
curves of type "explicit_prime" or "explicit_char2". For curves
of type "named_curves" G is part of the definition of the curve.
poo_params defines the necessary parameters to provide a proof of
ownership of the ECDHE private key. This option is intended to
prevent the LURK Server to sign bytes that do not correspond to a
ECDHE public key.
poo_prf pseudo random function used to generate the necessary
randoms to proof ownership of the private key. This document
defines sha256_128 and sha256_256 which apply the sha256 hash
function and respectively return the 128 or 256 first bits of
the resulting hash.
rG, tG are necessary points to generate the proof of ownership. r
is a random number chosen by the LURK Client. G is the the
base point of the curve. t = cb + r, with c a number that is
not under the control of the LURK Client generated as the
output of poo_prf and b the random secret of the private key.
The proof of ownership consists in the LURK Client proving the
knowledge of the private random b, while not disclosing b.
c MUST NOT be under the control of the LURK Client. To achieve that
goal, c is generated as described below:
c = poo_prf ( base + ecdhe_params + "tls12 poo")
The LURK Client computes t = cb + r and sends rG, tG, in poo_params
and bG in the ecdhe_params
The LURK Server computes c(bG) + rG and compares the output with tG.
The equality proves the ownership of b by the LURK Client.
Note r and c may be treated as "very short-term secrets" but MUST
remain non-predictable. It is RECOMMENDED to use a length equivalent
to the expected level of security, that is 128 bit length (resp. 256
bit length) for a 128 (resp 256) bit security level. Given b, we
RECOMMEND r and c to be at least half the size of b.
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7.2. Response Payload
The "ecdhe" response payload has the following structure:
struct {
Signature signed_params; // RFC4492 section 5.4
} TLS12ECDHEResponsePayload;
signed_params signature applied to the hash of the ecdhe_params as
well as client_random and server_random as described in [RFC4492]
section 5.4.
7.3. LURK Client Behavior
The LURK Client builds the base as described in Section 5.1. The
LURK Client computes c, t, rG and tG as described in Section 7.1.
Upon receiving the response payload, the LURK Client MAY check the
signature. If the signature does not match an error SHOULD be
reported.
7.4. LURK Server Behavior
Upon receiving an ecdhe request, the LURK Server proceeds as follows:
(1) The LURK Server performs some format check of the ecdhe_params
before signing them. If the ecdhe_params does not follow the
expected structure. With the notations from [RFC4492], if
curve_type (explicit_prime, explicit_char2 or named_curve) is
not supported, the LURK Server SHOULD be able to respond with an
"invalid_ec_type" error. With curve of type "explicit_char2",
if the basis (ec_basis_triomial or ec_basis_pentanomial) is not
supported, the LURK Server SHOULD be able to respond with an
"invalid_ec_basis_type" error. If the curve or namedcurve is
not supported the LURK Server SHOULD be able to respond with an
"invalid_ec_curve" error. For curves of type explicit_prime or
explicit_char2 when the expression of the point is not
supported, the LURK Server SHOULD be able to respond with an
"invalid_ec_point_format" error.
(2) The LURK Server processes the poo_params. If the poo_prf is not
supported, the LURK Extension returns a "invalid_poo_prf"
status. If poo_prf is supported and different from "null", the
LURK Server proceeds to the proof of ownership as described in
Section 7.1. If the proof is not properly verified, the LURK
Extension returns a "invalid_poo" status.
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(3) The LURK Server processes the base structure as described in
Section 5.4
(4) The LURK Server generates the siged_params.
Error are expected to provide the LURK Client an indication of the
cause that resulted in the error. When an error occurs the LURK
Server MAY ignore the request, or provide more generic error codes
such as "undefined_error" or "invalid_format".
8. capabilities
A exchange of type "capabilities" enables the LURK Client to be
informed of the supported operations performed by the LURK Server.
The supported parameters are provided on a per type basis.
8.1. Request Payload
A LURK "capabilities" request has no payload.
8.2. Response Payload
The "capabilities" response payload lists for each supported type,
the supported certificates, the supported signatures and hash
associated. The "capabilities" payload has the following structure:
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struct{
KeyPairIdType key_id_type_list<0..255>;
ProtocolVersion tls_version_list<0..255>;
PRFAlgorithm prf_list<0..255> // [RFC-TBD] rsa_master section
CertificateEntry certificate_list <0..2^26-2>;
// draft-ietf-tls-tls13 section 4.4.2
}TLS12BaseCapabilities
struct{
TLS12BaseCapabilities base_capabilities;
SignatureAndHashAlgorithm algo_list<2..2^16-2>;
// RFC5246 section 7.4.1.4.1
POOPRF poo_prf_list <0..255>;
NamedCurveList supported_curve_list
//draft-ietf-tls-rfc4492 section 5.1.1
ECPointFormatList ec_format_list
//draft-ietf-tls-rfc4492 section 5.1.2
}TLS12ECDHECapabilitites
struct {
TLS12Type type_list<0..255>;
TLS12BaseCapabilities rsa_capabilities;
TLS12BaseCapabilities extended_rsa_capabilities;
TLS12ECDHECapabilitites ecdhe_capabilities;
opaque state<32>;
}TLS12CapabilitiesResponsePayload;
key_id_type_list the supported key_id_type.
tls_version_list the supported tls_versions. The format is defined
in [RFC5246] section 6.2.1.
prf_list designates the list of prf ( see Section 5.1). As prf
indicates whether PFS is supported and that PFS is globally
supported for a given type only if all prf support PFS, the list
enables the LURK Client to check PFS is appropriately implemented
for a given type.
certificate_list designates the certificates associated to message
type. The format is defined in [I-D.ietf-tls-tls13] in section
4.4.2. This format enables the use of X509 as well as Raw Public
key, while the Certificate structure defined in [RFC5246] section
7.4.2 do not.
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algo_list designates supported signature algorithms as well as PRF
used for the different operations. The format is defined in
[RFC5246] section 7.4.1.4.1.
poo_prf_list the supported message type poo_prf ( see Section 7.1.
to be used with the proof of ownership.
type_list the supported message type of the LURK extension.
state characterizes the configuration associated to 'tls12' on the
LURK Server..
8.3. LURK Client Behavior
The LURK Client performs a capability request in order to determine
the possible operations.
The LURK Client is expected to keep the state value to be able to
detect a change in the LURK Server configuration when an error
occurs.
8.4. LURK Server Behavior
Upon receiving a capabilities request, the LURK Extension MUST return
the capabilities payload associated to a "success" status to the LURK
Server. These information are then forwarded by the LURK Server to
the LURK Client.
9. ping
A exchange of type "ping" enables the LURK Client to check the
reachability in a context of the defined LURK Extension.
9.1. Request Payload
A "ping" request has no payload.
9.2. Response Payload
A "ping" response has no payload.
9.3. LURK Client Behavior
The LURK Client sends a "ping" request to test the reachability of
the LURK Server. The reachability is performed for the tls12 LURK
Extension.
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9.4. LURK Server Behavior
Upon receiving a ping request, the LURK Extension MUST return the
ping response associated with a "success" status to the LURK Server.
These information are then forwarded by the LURK Server to the LURK
Client.
10. Security Considerations
The security considerations defined in [I-D.mglt-lurk-lurk] applies
to the LURK Extension "tls12" defined in this document.
The LURK Extension "tls12" is expected to have response smaller that
the request or at least not significantly larger, which makes "tls12"
relatively robust to amplification attacks.
The LURK Extension "tls12" performs cryptographic operations that may
lead to resource exhaustion, as such it is RECOMMENDED the LURK
Server authenticates the LURK Clients. In addition, this prevents
when UDP is used the LURK Server to be used as a reflector.
The rsa_master and ecdhe exchange provides a mechanism to provide
Perfect Forward Secrecy. It is RECOMMENDED to activate such
mechanism and disable any PFRAlgorithm suites that contains a PFS-PFR
set to null. Enabling a single PFS-PRF MAY compromise the PFS
property.
The rsa_extended_master does not provide PFS mechanism as a digest of
the TLS Key Exchange is provided which prevent the LURK Server to
perform an agreed operation on the HelloServer.random.
rsa_master and ecdhe request provides client_random. In order to
limit the replay of a random value it RECOMMENDED the Server control
the time at which the random has been generated. The time control
should also consider desynchronization between the TLS Client and the
LURK Server.
10.1. RSA
The rsa_master and rsa_extended_master exchange carry the master
secret. These pieces of information enable a passive attacker to
hijack the session and as such it is RECOMMENDED the LURK Server and
the LURK Client use an encrypted channel when the authentication RSA
is used.
The rsa_master and rsa_extended_master returns the master_secret
instead of the premaster. The additional hashing operation necessary
to generate the master secret is expected to improve the protection
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of the RSA private key against cryptographic analysis based on the
observation of a set of clear text and corresponding encrypted text.
Note that having the Key Server generating the server random on its
own without any input from the Edge Server would also achieve the PFS
in a similar way as standard TLS does. The pfs options achieves
similar properties while enabling a LURK Client to replay a request.
The standard TLS1.2 is robust against Bleichenbacher attack as it
provides no means to detect if the error comes from a TLS version
mismatch or from the premaster format. This properties remain with
LURK, and so LURK does not present vulnerabilities toward
Bleichenbacher attack, and cannot be used as a decryption oracle.
10.2. ECDHE
A passive attacker observing the ecdhe exchange may collect a
sufficient amount of clear text and corresponding signature to
perform a cryptographic analysis or to reuse the signature for other
purposes. As a result, it is RECOMMENDED to encrypt the ecdhe
exchange between the LURK Client and the LURK Server. Note that this
vulnerability is present in TLS 1.2 as a TLS Client can accumulate
these data as well. The difference with LURK is by listening the
LURK Server, the accumulation is achieved for all TLS Clients.
As previously mentioned, the LURK Server may be used as signing
oracle for the specific string:
SHA(ClientHello.random + ServerHello.random +
ServerKeyExchange.params);
More specifically, the ECDHE_RSA and ECDHE_DSA mechanisms does not
associate the signature to a TLS1.2 context. As a result, the
signature could be re-used in another context.
The attack may operate by collecting a large collection of clear text
and their corresponding signature. When the attacker want to provide
a signature, it checks in its database, a match occurs between the
two contents to be signed. The probability of a collision increases
with number of available hashes. The attack is related the pre-image
and collision resistance properties of the hash function.
The attacker may also given a clear text to be signed, generate a
collision such that a collision occurs which provides is related to
the second pre-image and collision resistance property of the hash
function.
The surface of attack is limited by:
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a. limiting the possibility of aggregating a collection of clear
text and their corresponding signatures. This could be achieved
by using multiple LURK Clients using an encrypted channel between
the LURK Client and the LURK Server.
b. increasing the checks and ensure that signature is performed in a
TLS 1.2 context. For that purpose it is RECOMMENDED the LURK
Server checks the consistency of its input parameters. This
includes the proof of ownership as well as the format of the
randoms and ecdhe_params for example.
c. limiting the usage of a Cryptographic material to a single usage,
in our case serving TLS 1.2.
11. IANA Considerations
The requested information is defined in [I-D.mglt-lurk-lurk].
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LURK Extension Designation: tls12
LURK Extension Reference: [RFD-TBD]
LURK Extension Description: RSA, ECDHE_RSA and ECDHE_ECDSA for (D)TLS
1.1 and (D)TLS 1.2.
LURK tls12 Extension Status
Value Description Reference
---------------------------------------------------
0 - 1 Reserved [RFC-TBD-LURK]
2 undefined_error [RFC-TBD]
3 invalid_payload_format [RFC-TBD]
4 invalid_key_id_type [RFC-TBD]
5 invalid_key_id [RFC-TBD]
6 invalid_tls_version [RFC-TBD]
7 invalid_tls_random [RFC-TBD]
8 invalid_prf [RFC-TBD]
9 invalid_encrypted_premaster [RFC-TBD]
10 invalid_ec_type [RFC-TBD]
11 invalid_ec_basis_type [RFC-TBD]
12 invalid_ec_curve [RFC-TBD]
13 invalid_ec_point_format [RFC-TBD]
14 invalid_poo_prf [RFC-TBD]
15 invalid_poo [RFC-TBD]
16 - 255 UNASSIGNED
LURK tls12 Extension Type
Value Description Reference
----------------------------------------------
0 capabilities [RFC-TBD]
1 ping [RFC-TBD]
2 rsa_master [RFC-TBD]
3 rsa_extended_master [RFC-TBD]
4 ecdhe [RFC-TBD]
16 - 255 UNASSIGNED
12. Acknowledgments
We would like to thank for their very useful feed backs: Yaron
Sheffer, Yoav Nir, Stephen Farrell, Eric Burger, Thomas Fossati, Eric
Rescorla Mat Naslung, Rich Salz. Many ideas in this document are
from [I-D.erb-lurk-rsalg].
We would also like to thank those that have supported LURK or raised
interesting discussions. This includes among others Robert Skog,
Hans Spaak, Salvatore Loreto, John Mattsson, Alexei Tumarkin, Yaron
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Sheffer, Richard Brunner, Stephane Dault, Dan Kahn Gillmor, Joe
Hildebrand, Kelsey Cairns.
13. References
13.1. 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/info/rfc2119>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension",
RFC 7627, DOI 10.17487/RFC7627, September 2015,
<https://www.rfc-editor.org/info/rfc7627>.
13.2. Informative References
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346,
DOI 10.17487/RFC4346, April 2006,
<https://www.rfc-editor.org/info/rfc4346>.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, DOI 10.17487/RFC4347, April 2006,
<https://www.rfc-editor.org/info/rfc4347>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006,
<https://www.rfc-editor.org/info/rfc4492>.
[I-D.mglt-lurk-tls-use-cases]
Migault, D., Ma, K., Salz, R., Mishra, S., and O. Dios,
"LURK TLS/DTLS Use Cases", draft-mglt-lurk-tls-use-
cases-02 (work in progress), June 2016.
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[I-D.erb-lurk-rsalg]
Erb, S. and R. Salz, "A PFS-preserving protocol for LURK",
draft-erb-lurk-rsalg-01 (work in progress), May 2016.
[I-D.rescorla-tls-subcerts]
Barnes, R., Iyengar, S., Sullivan, N., and E. Rescorla,
"Delegated Credentials for TLS", draft-rescorla-tls-
subcerts-02 (work in progress), October 2017.
[I-D.ietf-acme-star]
Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T.
Fossati, "Support for Short-Term, Automatically-Renewed
(STAR) Certificates in Automated Certificate Management
Environment (ACME)", draft-ietf-acme-star-02 (work in
progress), November 2017.
[I-D.ietf-acme-acme]
Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment
(ACME)", draft-ietf-acme-acme-09 (work in progress),
December 2017.
[I-D.sheffer-acme-star-request]
Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T.
Fossati, "Generating Certificate Requests for Short-Term,
Automatically-Renewed (STAR) Certificates", draft-sheffer-
acme-star-request-01 (work in progress), June 2017.
[I-D.fieau-cdni-https-delegation]
Fieau, F., Emile, S., and S. Mishra, "HTTPS delegation in
CDNI", draft-fieau-cdni-https-delegation-02 (work in
progress), July 2017.
[I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-23 (work in progress),
January 2018.
[I-D.mglt-lurk-lurk]
Migault, D., "LURK Protocol version 1", draft-mglt-lurk-
lurk-00 (work in progress), March 2017.
Appendix A. Example of LURK Exchanges
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A.1. LURK/TLS RSA Master Secret
TLS Client Edge Server Key Server
ClientHello
server_version
client_random
cipher_suite
TLS_RSA_*, ...
-------->
ServerHello
tls_version
server_random
Cipher_suite=TLS_RSA
Certificate
RSA Public Key
ServerHelloDone
<--------
ClientKeyExchange
EncryptedPremasterSecret
[ChangeCipherSpec]
Finished
-------->
TLS12 Request Header
TLS12MasterRSARequestPayload
key_id
client_random
edge_server_random
tls_version
master_prf
EncryptedPremasterSecret
-------->
1. Computing Master Secret
master_secret = master_prf(\
pre_master_secret + \
"master secret" +\
client_random +\
edge_server_random)[0..47];
TLS12 Response Header
TLS12MasterResponsePayload
master
<--------
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[ChangeCipherSpec]
Finished
<--------
Application Data <-------> Application Data
A.2. LURK/TLS RSA Extended Master Secret
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TLS Client Edge Server Key Server
ClientHello
tls_version
cipher_suite
TLS_RSA_*, ...
Extension 0x0017
-------->
ServerHello
edge_server_version
cipher_suite=TLS_RSA
Extension 0x0017
Certificate
RSA Public Key
ServerHelloDone
<--------
ClientKeyExchange
EncryptedPremasterSecret
[ChangeCipherSpec]
Finished
-------->
TLS12 Request Header
TLS12ExtendedMasterRSAInputPayload
key_id
tls_version
master_prf
session_hash
EncryptedPreMasterSecret
-------->
1. Computing Master Secret
master_secret = master_prf(
pre_master_secret +\
"extended master secret" +\
session_hash)[0..47]
TLS12 Response Header
TLS12MasterPayload
master
<--------
[ChangeCipherSpec]
Finished
<--------
Application Data <-------> Application Data
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A.3. LURK/TLS ECDHE Signature
TLS Client Edge Server Key Server
ClientHello
tls_version
client_random
cipher_suite
TLS_ECDHE_ECDSA_*, TLS_ECDHE_RSA_*, ...
Extension Supported EC, Supported Point Format
-------->
TLS12 Request Header
TLS12ECDHEInputPayload
key_id
client_random
edge_server_random
tls_version
ecdhe_params
-------->
1. Generating the signature
signature = ECDSA(client_random +\
edge_server_random + ecdhe_params)
TLS12 Response Header
TLS12DigitallySignedPayloads
signature
<--------
ServerHello
edge_server_version
edge_server_random
Cipher_suite=TLS_ECDHE_ECDSA
Extension Supported EC,
Supported Point Format
Certificate
ECDSA Public Key
ServerKeyExchange
ecdhe_params
signature
ServerHelloDone
<--------
ClientKeyExchange
[ChangeCipherSpec]
Finished
-------->
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[ChangeCipherSpec]
Finished
<--------
Application Data <-------> Application Data
Author's Address
Daniel Migault (editor)
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
Phone: +1 514-452-2160
Email: daniel.migault@ericsson.com
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