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|
Internet Engineering Task Force D. Farinacci
Internet-Draft lispers.net
Intended status: Experimental B. Weis
Expires: April 17, 2017 cisco Systems
October 14, 2016
LISP Data-Plane Confidentiality
draft-ietf-lisp-crypto-10
Abstract
This document describes a mechanism for encrypting LISP encapsulated
traffic. The design describes how key exchange is achieved using
existing LISP control-plane mechanisms as well as how to secure the
LISP data-plane from third-party surveillance attacks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 17, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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.
Farinacci & Weis Expires April 17, 2017 [Page 1]
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Diffie-Hellman Key Exchange . . . . . . . . . . . . . . . . . 4
6. Encoding and Transmitting Key Material . . . . . . . . . . . 5
7. Shared Keys used for the Data-Plane . . . . . . . . . . . . . 8
8. Data-Plane Operation . . . . . . . . . . . . . . . . . . . . 10
9. Procedures for Encryption and Decryption . . . . . . . . . . 11
10. Dynamic Rekeying . . . . . . . . . . . . . . . . . . . . . . 12
11. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 13
12. Security Considerations . . . . . . . . . . . . . . . . . . . 13
12.1. SAAG Support . . . . . . . . . . . . . . . . . . . . . . 13
12.2. LISP-Crypto Security Threats . . . . . . . . . . . . . . 14
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
14.1. Normative References . . . . . . . . . . . . . . . . . . 15
14.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 17
Appendix B. Document Change Log . . . . . . . . . . . . . . . . 17
B.1. Changes to draft-ietf-lisp-crypto-10.txt . . . . . . . . 17
B.2. Changes to draft-ietf-lisp-crypto-09.txt . . . . . . . . 18
B.3. Changes to draft-ietf-lisp-crypto-08.txt . . . . . . . . 18
B.4. Changes to draft-ietf-lisp-crypto-07.txt . . . . . . . . 18
B.5. Changes to draft-ietf-lisp-crypto-06.txt . . . . . . . . 18
B.6. Changes to draft-ietf-lisp-crypto-05.txt . . . . . . . . 18
B.7. Changes to draft-ietf-lisp-crypto-04.txt . . . . . . . . 18
B.8. Changes to draft-ietf-lisp-crypto-03.txt . . . . . . . . 18
B.9. Changes to draft-ietf-lisp-crypto-02.txt . . . . . . . . 19
B.10. Changes to draft-ietf-lisp-crypto-01.txt . . . . . . . . 19
B.11. Changes to draft-ietf-lisp-crypto-00.txt . . . . . . . . 19
B.12. Changes to draft-farinacci-lisp-crypto-01.txt . . . . . . 20
B.13. Changes to draft-farinacci-lisp-crypto-00.txt . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
This document describes a mechanism for encrypting LISP encapsulated
traffic. The design describes how key exchange is achieved using
existing LISP control-plane mechanisms as well as how to secure the
LISP data-plane from third-party surveillance attacks.
The Locator/ID Separation Protocol [RFC6830] defines a set of
functions for routers to exchange information used to map from non-
routable Endpoint Identifiers (EIDs) to routable Routing Locators
(RLOCs). LISP Ingress Tunnel Routers (ITRs) and Proxy Ingress Tunnel
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Routers (PITRs) encapsulate packets to Egress Tunnel Routers (ETRs)
and Reencapsulating Tunnel Routers (RTRs). Packets that arrive at
the ITR or PITR may not be encrypted, which means no protection or
privacy of the data is added. When the source host encrypts the data
stream, encapsulated packets do not need to be encrypted by LISP.
However, when plaintext packets are sent by hosts, this design can
encrypt the user payload to maintain privacy on the path between the
encapsulator (the ITR or PITR) to a decapsulator (ETR or RTR). The
encrypted payload is unidirectional. However, return traffic uses
the same procedures but with different key values by the same xTRs or
potentially different xTRs when the paths between LISP sites are
asymmetric.
This document has the following requirements (as well as the general
requirements from [RFC6973]) for the solution space:
o Do not require a separate Public Key Infrastructure (PKI) that is
out of scope of the LISP control-plane architecture.
o The budget for key exchange MUST be one round-trip time. That is,
only a two packet exchange can occur.
o Use symmetric keying so faster cryptography can be performed in
the LISP data plane.
o Avoid a third-party trust anchor if possible.
o Provide for rekeying when secret keys are compromised.
o Support Authenticated Encryption with packet integrity checks.
o Support multiple cipher suites so new crypto algorithms can be
easily introduced.
Satisfying the above requirements provides the following benefits:
o Avoiding a PKI reduces the operational cost of managing a secure
network. Key management is distributed and independent from any
other infrastructure.
o Packet transport is optimized due to less packet headers. Packet
loss is reduced by a more efficient key exchange.
o Authentication and privacy are provided with a single mechanism
thereby providing less per packet overhead and therefore more
resource efficiency.
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2. 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].
3. Definition of Terms
AEAD: Authenticated Encryption with Additional Data [RFC5116].
ICV: Integrity Check Value.
LCAF: LISP Canonical Address Format ([LCAF]).
xTR: A general reference to ITRs, ETRs, RTRs, and PxTRs.
4. Overview
The approach proposed in this document is to NOT rely on the LISP
mapping system (or any other key infrastructure system) to store
security keys. This will provide for a simpler and more secure
mechanism. Secret shared keys will be negotiated between the ITR and
the ETR in Map-Request and Map-Reply messages. Therefore, when an
ITR needs to obtain the RLOC of an ETR, it will get security material
to compute a shared secret with the ETR.
The ITR can compute 3 shared-secrets per ETR the ITR is encapsulating
to. When the ITR encrypts a packet before encapsulation, it will
identify the key it used for the crypto calculation so the ETR knows
which key to use for decrypting the packet after decapsulation. By
using key-ids in the LISP header, we can also get fast rekeying
functionality.
The key management described in this documemnt is unidirectional from
the ITR (the encapsulator) to the ETR (the decapsultor).
5. Diffie-Hellman Key Exchange
LISP will use a Diffie-Hellman [RFC2631] key exchange sequence and
computation for computing a shared secret. The Diffie-Hellman
parameters will be passed via Cipher Suite code-points in Map-Request
and Map-Reply messages.
Here is a brief description how Diff-Hellman works:
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+----------------------------+---------+----------------------------+
| ITR | | ETR |
+------+--------+------------+---------+------------+---------------+
|Secret| Public | Calculates | Sends | Calculates | Public |Secret|
+------|--------|------------|---------|------------|--------|------+
| i | p,g | | p,g --> | | | e |
+------|--------|------------|---------|------------|--------|------+
| i | p,g,I |g^i mod p=I | I --> | | p,g,I | e |
+------|--------|------------|---------|------------|--------|------+
| i | p,g,I | | <-- E |g^e mod p=E | p,g | e |
+------|--------|------------|---------|------------|--------|------+
| i,s |p,g,I,E |E^i mod p=s | |I^e mod p=s |p,g,I,E | e,s |
+------|--------|------------|---------|------------|--------|------+
Public-key exchange for computing a shared private key [DH]
Diffie-Hellman parameters 'p' and 'g' must be the same values used by
the ITR and ETR. The ITR computes public-key 'I' and transmits 'I'
in a Map-Request packet. When the ETR receives the Map-Request, it
uses parameters 'p' and 'g' to compute the ETR's public key 'E'. The
ETR transmits 'E' in a Map-Reply message. At this point, the ETR has
enough information to compute 's', the shared secret, by using 'I' as
the base and the ETR's private key 'e' as the exponent. When the ITR
receives the Map-Reply, it uses the ETR's public-key 'E' with the
ITR's private key 'i' to compute the same 's' shared secret the ETR
computed. The value 'p' is used as a modulus to create the width of
the shared secret 's' (see Section 6).
6. Encoding and Transmitting Key Material
The Diffie-Hellman key material is transmitted in Map-Request and
Map-Reply messages. Diffie-Hellman parameters are encoded in the
LISP Security Type LCAF [LCAF].
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFI = 16387 | Rsvd1 | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 11 | Rsvd2 | 6 + n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Count | Rsvd3 | Cipher Suite | Rsvd4 |R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Length | Public Key Material ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... Public Key Material |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFI = x | Locator Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Cipher Suite field contains DH Key Exchange and Cipher/Hash Functions
The 'Key Count' field encodes the number of {'Key-Length', 'Key-
Material'} fields included in the encoded LCAF. The maximum number
of keys that can be encoded are 3, each identified by key-id 1,
followed by key-id 2, and finally key-id 3.
The 'R' bit is not used for this use-case of the Security Type LCAF
but is reserved for [LISP-DDT] security. Therefore, the R bit SHOULD
be transmitted as 0 and MUST be ignored on receipt.
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Cipher Suite 0:
Reserved
Cipher Suite 1:
Diffie-Hellman Group: 2048-bit MODP [RFC3526]
Encryption: AES with 128-bit keys in CBC mode [AES-CBC]
Integrity: Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256
IV length: 16 bytes
KDF: HMAC-SHA-256
Cipher Suite 2:
Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
Encryption: AES with 128-bit keys in CBC mode [AES-CBC]
Integrity: Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256
IV length: 16 bytes
KDF: HMAC-SHA-256
Cipher Suite 3:
Diffie-Hellman Group: 2048-bit MODP [RFC3526]
Encryption: AES with 128-bit keys in GCM mode [RFC5116]
Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM
IV length: 12 bytes
KDF: HMAC-SHA-256
Cipher Suite 4:
Diffie-Hellman Group: 3072-bit MODP [RFC3526]
Encryption: AES with 128-bit keys in GCM mode [RFC5116]
Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM
IV length: 12 bytes
KDF: HMAC-SHA-256
Cipher Suite 5:
Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
Encryption: AES with 128-bit keys in GCM mode [RFC5116]
Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM
IV length: 12 bytes
KDF: HMAC-SHA-256
Cipher Suite 6:
Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
Encryption: Chacha20-Poly1305 [CHACHA-POLY] [RFC7539]
Integrity: Integrated with [CHACHA-POLY] AEAD_CHACHA20_POLY1305
IV length: 8 bytes
KDF: HMAC-SHA-256
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The "Public Key Material" field contains the public key generated by
one of the Cipher Suites defined above. The length of the key in
octets is encoded in the "Key Length" field.
When an ITR, PITR, or RTR sends a Map-Request, they will encode their
own RLOC in the Security Type LCAF format within the ITR-RLOCs field.
When a ETR or RTR sends a Map-Reply, they will encode their RLOCs in
Security Type LCAF format within the RLOC-record field of each EID-
record supplied.
If an ITR, PITR, or RTR sends a Map-Request with the Security Type
LCAF included and the ETR or RTR does not want to have encapsulated
traffic encrypted, they will return a Map-Reply with no RLOC records
encoded with the Security Type LCAF. This signals to the ITR, PITR
or RTR not to encrypt traffic (it cannot encrypt traffic anyways
since no ETR public-key was returned).
Likewise, if an ITR or PITR wish to include multiple key-ids in the
Map-Request but the ETR or RTR wish to use some but not all of the
key-ids, they return a Map-Reply only for those key-ids they wish to
use.
7. Shared Keys used for the Data-Plane
When an ITR or PITR receives a Map-Reply accepting the Cipher Suite
sent in the Map-Request, it is ready to create data plane keys. The
same process is followed by the ETR or RTR returning the Map-Reply.
The first step is to create a shared secret, using the peer's shared
Diffie-Hellman Public Key Material combined with device's own private
keying material as described in Section 5. The Diffie-Hellman
parameters used is defined in the cipher suite sent in the Map-
Request and copied into the Map-Reply.
The resulting shared secret is used to compute an AEAD-key for the
algorithms specified in the cipher suite. A Key Derivation Function
(KDF) in counter mode as specified by [NIST-SP800-108] is used to
generate the data-plane keys. The amount of keying material that is
derived depends on the algorithms in the cipher suite.
The inputs to the KDF are as follows:
o KDF function. This is HMAC-SHA-256 in this document but generally
specified in each Cipher Suite definition.
o A key for the KDF function. This is the computed Diffie-Hellman
shared secret.
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o Context that binds the use of the data-plane keys to this session.
The context is made up of the following fields, which are
concatenated and provided as the data to be acted upon by the KDF
function.
Context:
o A counter, represented as a two-octet value in network byte order.
o The null-terminated string "lisp-crypto".
o The ITR's nonce from the Map-Request the cipher suite was included
in.
o The number of bits of keying material required (L), represented as
a two-octet value in network byte order.
The counter value in the context is first set to 1. When the amount
of keying material exceeds the number of bits returned by the KDF
function, then the KDF function is called again with the same inputs
except that the counter increments for each call. When enough keying
material is returned, it is concatenated and used to create keys.
For example, AES with 128-bit keys requires 16 octets (128 bits) of
keying material, and HMAC-SHA1-96 requires another 16 octets (128
bits) of keying material in order to maintain a consistent 128-bits
of security. Since 32 octets (256 bits) of keying material are
required, and the KDF function HMAC-SHA-256 outputs 256 bits, only
one call is required. The inputs are as follows:
key-material = HMAC-SHA-256(dh-shared-secret, context)
where: context = 0x0001 || "lisp-crypto" || <itr-nonce> || 0x0100
In contrast, a cipher suite specifying AES with 256-bit keys requires
32 octets (256 bits) of keying material, and HMAC-SHA256-128 requires
another 32 octets (256 bits) of keying material in order to maintain
a consistent 256-bits of security. Since 64 octets (512 bits) of
keying material are required, and the KDF function HMAC-SHA-256
outputs 256 bits, two calls are required.
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key-material-1 = HMAC-SHA-256(dh-shared-secret, context)
where: context = 0x0001 || "lisp-crypto" || <itr-nonce> || 0x0200
key-material-2 = HMAC-SHA-256(dh-shared-secret, context)
where: context = 0x0002 || "lisp-crypto" || <itr-nonce> || 0x0200
key-material = key-material-1 || key-material-2
If the key-material is longer than the required number of bits (L),
then only the most significant L bits are used.
From the derived key-material, the most significant 256 bits are used
for the AEAD-key by AEAD ciphers. The 256-bit AEAD-key is divided
into a 128-bit encryption key and a 128-bit integrity check key
internal to the cipher used by the ITR.
8. Data-Plane Operation
The LISP encapsulation header [RFC6830] requires changes to encode
the key-id for the key being used for encryption.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L / |N|L|E|V|I|R|K|K| Nonce/Map-Version |\ \
I +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A
S \ | Instance ID/Locator-Status-Bits | |D
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |/
| Initialization Vector (IV) | I
E +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ C
n / | | V
c | | |
r | Packet Payload with EID Header ... | |
y | | |
p \ | |/
t +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
K-bits indicate when packet is encrypted and which key used
When the KK bits are 00, the encapsulated packet is not encrypted.
When the value of the KK bits are 1, 2, or 3, it encodes the key-id
of the secret keys computed during the Diffie-Hellman Map-Request/
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Map-Reply exchange. When the KK bits are not 0, the payload is
prepended with an Initialization Vector (IV). The length of the IV
field is based on the cipher suite used. Since all cipher suites
defined in this document do Authenticated Encryption (AEAD), an ICV
field does not need to be present in the packet since it is included
in the ciphertext. The Additional Data (AD) used for the ICV is
shown above and includes the LISP header, the IV field and the packet
payload.
When an ITR or PITR receives a packet to be encapsulated, the device
will first decide what key to use, encode the key-id into the LISP
header, and use that key to encrypt all packet data that follows the
LISP header. Therefore, the outer header, UDP header, and LISP
header travel as plaintext.
There is an open working group item to discuss if the data
encapsulation header needs change for encryption or any new
applications. This document proposes changes to the existing header
so experimentation can continue without making large changes to the
data-plane at this time. This document allocates 2 bits of the
previously unused 3 flag bits (note the R-bit above is still a
reserved flag bit as documented in [RFC6830]) for the KK bits.
9. Procedures for Encryption and Decryption
When an ITR, PITR, or RTR encapsulate a packet and have already
computed an AEAD-key (detailed in section Section 7) that is
associated with a destination RLOC, the following encryption and
encapsulation procedures are performed:
1. The encapsulator creates an IV and prepends the IV value to the
packet being encapsulated. For GCM and Chacha cipher suites, the
IV is incremented for every packet (beginning with a value of 1
in the first packet) and sent to the destination RLOC. For CBC
cipher suites, the IV is a new random number for every packet
sent to the destination RLOC. For the Chacha cipher suite, the
IV is an 8-byte random value that is appended to a 4-byte counter
that is incremented for every packet (beginning with a value of 1
in the first packet).
2. Next encrypt with cipher function AES or Chacha20 using the AEAD-
key over the packet payload following the AEAD specification
referenced in the cipher suite definition. This does not include
the IV. The IV must be transmitted as plaintext so the decrypter
can use it as input to the decryption cipher. The payload should
be padded to an integral number of bytes a block cipher may
require. The result of the AEAD operation may contain an ICV,
the size of which is defined by the referenced AEAD
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specification. Note that the AD (i.e. the LISP header exactly as
will be prepended in the next step and the IV) must be given to
the AEAD encryption function as the "associated data" argument.
3. Prepend the LISP header. The key-id field of the LISP header is
set to the key-id value that corresponds to key-pair used for the
encryption cipher.
4. Lastly, prepend the UDP header and outer IP header onto the
encrypted packet and send packet to destination RLOC.
When an ETR, PETR, or RTR receive an encapsulated packet, the
following decapsulation and decryption procedures are performed:
1. The outer IP header, UDP header, LISP header, and IV field are
stripped from the start of the packet. The LISP header and IV
are retained and given to the AEAD decryption operation as the
"associated data" argument.
2. The packet is decrypted using the AEAD-key and the IV from the
packet. The AEAD-key is obtained from a local-cache associated
with the key-id value from the LISP header. The result of the
decryption function is a plaintext packet payload if the cipher
returned a verified ICV. Otherwise, the packet is invalid and is
discarded. If the AEAD specification included an ICV, the AEAD
decryption function will locate the ICV in the ciphertext and
compare it to a version of the ICV that the AEAD decryption
function computes. If the computed ICV is different than the ICV
located in the ciphertext, then it will be considered tampered.
3. If the packet was not tampered with, the decrypted packet is
forwarded to the destination EID.
10. Dynamic Rekeying
Since multiple keys can be encoded in both control and data messages,
an ITR can encapsulate and encrypt with a specific key while it is
negotiating other keys with the same ETR. As soon as an ETR or RTR
returns a Map-Reply, it should be prepared to decapsulate and decrypt
using the new keys computed with the new Diffie-Hellman parameters
received in the Map-Request and returned in the Map-Reply.
RLOC-probing can be used to change keys or cipher suites by the ITR
at any time. And when an initial Map-Request is sent to populate the
ITR's map-cache, the Map-Request flows across the mapping system
where a single ETR from the Map-Reply RLOC-set will respond. If the
ITR decides to use the other RLOCs in the RLOC-set, it MUST send a
Map-Request directly to negotiate security parameters with the ETR.
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This process may be used to test reachability from an ITR to an ETR
initially when a map-cache entry is added for the first time, so an
ITR can get both reachability status and keys negotiated with one
Map-Request/Map-Reply exchange.
A rekeying event is defined to be when an ITR or PITR changes the
cipher suite or public-key in the Map-Request. The ETR or RTR
compares the cipher suite and public-key it last received from the
ITR for the key-id, and if any value has changed, it computes a new
public-key and cipher suite requested by the ITR from the Map-Request
and returns it in the Map-Reply. Now a new shared secret is computed
and can be used for the key-id for encryption by the ITR and
decryption by the ETR. When the ITR or PITR starts this process of
negotiating a new key, it must not use the corresponding key-id in
encapsulated packets until it receives a Map-Reply from the ETR with
the same cipher suite value it expects (the values it sent in a Map-
Request).
Note when RLOC-probing continues to maintain RLOC reachability and
rekeying is not desirable, the ITR or RTR can either not include the
Security Type LCAF in the Map-Request or supply the same key material
as it received from the last Map-Reply from the ETR or RTR. This
approach signals to the ETR or RTR that no rekeying event is
requested.
11. Future Work
For performance considerations, newer Elliptic-Curve Diffie-Hellman
(ECDH) groups can be used as specified in [RFC4492] and [RFC6090] to
reduce CPU cycles required to compute shared secret keys.
For better security considerations as well as to be able to build
faster software implementations, newer approaches to ciphers and
authentication methods will be researched and tested. Some examples
are Chacha20 and Poly1305 [CHACHA-POLY] [RFC7539].
12. Security Considerations
12.1. SAAG Support
The LISP working group received security advice and guidance from the
Security Area Advisory Group (SAAG). The SAAG has been involved
early in the design process and their input and reviews have been
included in this document.
Comments from the SAAG included:
1. Do not use asymmetric ciphers in the data-plane.
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2. Consider adding ECDH early in the design.
3. Add cipher suites because ciphers are created more frequently
than protocols that use them.
4. Consider the newer AEAD technology so authentication comes with
doing encryption.
12.2. LISP-Crypto Security Threats
Since ITRs and ETRs participate in key exchange over a public non-
secure network, a man-in-the-middle (MITM) could circumvent the key
exchange and compromise data-plane confidentiality. This can happen
when the MITM is acting as a Map-Replier, provides its own public key
so the ITR and the MITM generate a shared secret key among each
other. If the MITM is in the data path between the ITR and ETR, it
can use the shared secret key to decrypt traffic from the ITR.
Since LISP can secure Map-Replies by the authentication process
specified in [LISP-SEC], the ITR can detect when a MITM has signed a
Map-Reply for an EID-prefix it is not authoritative for. When an ITR
determines the signature verification fails, it discards and does not
reuse the key exchange parameters, avoids using the ETR for
encapsulation, and issues a severe log message to the network
administrator. Optionally, the ITR can send RLOC-probes to the
compromised RLOC to determine if can reach the authoritative ETR.
And when the ITR validates the signature of a Map-Reply, it can begin
encrypting and encapsulating packets to the RLOC of ETR.
13. IANA Considerations
This document describes a mechanism for encrypting LISP encapsulated
packets based on Diffie-Hellman key exchange procedures. During the
exchange the devices have to agree on a Cipher Suite used (i.e. the
cipher and hash functions used to encrypt/decrypt and to sign/verify
packets). The 8-bit Cipher Suite field is reserved for such purpose
in the security material section of the Map-Request and Map-Reply
messages.
This document requests IANA to create and maintain a new registry (as
outlined in [RFC5226]) entitled "LISP Crypto Cipher Suite". Initial
values for the registry are provided below. Future assignments are
to be made on a First Come First Served Basis.
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+-----+--------------------------------------------+------------+
|Value| Suite | Definition |
+-----+--------------------------------------------+------------+
| 0 | Reserved | Section 6 |
+-----+--------------------------------------------+------------+
| 1 | LISP_2048MODP_AES128_CBC_SHA256 | Section 6 |
+-----+--------------------------------------------+------------+
| 2 | LISP_EC25519_AES128_CBC_SHA256 | Section 6 |
+-----+--------------------------------------------+------------+
| 3 | LISP_2048MODP_AES128_GCM | Section 6 |
+-----+--------------------------------------------+------------+
| 4 | LISP_3072MODP_AES128_GCM M-3072 | Section 6 |
+-----+--------------------------------------------+------------+
| 5 | LISP_256_EC25519_AES128_GCM | Section 6 |
+-----+--------------------------------------------+------------+
| 6 | LISP_256_EC25519_CHACHA20_POLY1305 | Section 6 |
+-----+--------------------------------------------+------------+
LISP Crypto Cipher Suites
14. References
14.1. Normative References
[LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
Address Format", draft-ietf-lisp-lcaf-13.txt (work in
progress).
[NIST-SP800-108]
"National Institute of Standards and Technology,
"Recommendation for Key Derivation Using Pseudorandom
Functions NIST SP800-108"", NIST SP 800-108, October 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, DOI 10.17487/RFC2631, June 1999,
<http://www.rfc-editor.org/info/rfc2631>.
[RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
Diffie-Hellman groups for Internet Key Exchange (IKE)",
RFC 3526, DOI 10.17487/RFC3526, May 2003,
<http://www.rfc-editor.org/info/rfc3526>.
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[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,
<http://www.rfc-editor.org/info/rfc4492>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090,
DOI 10.17487/RFC6090, February 2011,
<http://www.rfc-editor.org/info/rfc6090>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<http://www.rfc-editor.org/info/rfc6830>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<http://www.rfc-editor.org/info/rfc6973>.
[RFC7539] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015,
<http://www.rfc-editor.org/info/rfc7539>.
14.2. Informative References
[AES-CBC] McGrew, D., Foley, J., and K. Paterson, "Authenticated
Encryption with AES-CBC and HMAC-SHA", draft-mcgrew-aead-
aes-cbc-hmac-sha2-05.txt (work in progress).
[CHACHA-POLY]
Langley, A., "ChaCha20 and Poly1305 based Cipher Suites
for TLS", draft-agl-tls-chacha20poly1305-04 (work in
progress).
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[CURVE25519]
Bernstein, D., "Curve25519: new Diffie-Hellman speed
records", Publication
http://www.iacr.org/cryptodb/archive/2006/
PKC/3351/3351.pdf.
[DH] "Diffie-Hellman key exchange", Wikipedia
http://en.wikipedia.org/wiki/Diffie-Hellman_key_exchange.
[LISP-DDT]
Fuller, V., Lewis, D., Ermaagan, V., and A. Jain, "LISP
Delegated Database Tree", draft-fuller-lisp-ddt-04 (work
in progress).
[LISP-SEC]
Maino, F., Ermagan, V., Cabellos, A., and D. Saucez,
"LISP-Secuirty (LISP-SEC)", draft-ietf-lisp-sec-10 (work
in progress).
Appendix A. Acknowledgments
The authors would like to thank Dan Harkins, Joel Halpern, Fabio
Maino, Ed Lopez, Roger Jorgensen, and Watson Ladd for their interest,
suggestions, and discussions about LISP data-plane security. An
individual thank you to LISP WG chair Luigi Iannone for shepherding
this document as well as contributing to the IANA Considerations
section.
The authors would like to give a special thank you to Ilari Liusvaara
for his extensive commentary and discussion. He has contributed his
security expertise to make lisp-crypto as secure as the state of the
art in cryptography.
In addition, the support and suggestions from the SAAG working group
were helpful and appreciative.
Appendix B. Document Change Log
[RFC Editor: Please delete this section on publication as RFC.]
B.1. Changes to draft-ietf-lisp-crypto-10.txt
o Posted October 2016 after October 13th telechat.
o Addressed comments from Kathleen Moriarty, Stephen Farrel, and
Pete Resnick.
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B.2. Changes to draft-ietf-lisp-crypto-09.txt
o Posted October 2016.
o Addressed comments from OPs Directorate reviewer Susan Hares.
B.3. Changes to draft-ietf-lisp-crypto-08.txt
o Posted September 2016.
o Addressed comments from Security Directorate reviewer Chris
Lonvick.
B.4. Changes to draft-ietf-lisp-crypto-07.txt
o Posted September 2016.
o Addressed comments from Routing Directorate reviewer Danny
McPherson.
B.5. Changes to draft-ietf-lisp-crypto-06.txt
o Posted June 2016.
o Fixed IDnits errors.
B.6. Changes to draft-ietf-lisp-crypto-05.txt
o Posted June 2016.
o Update document which reflects comments Luigi provided as document
shepherd.
B.7. Changes to draft-ietf-lisp-crypto-04.txt
o Posted May 2016.
o Update document timer from expiration.
B.8. Changes to draft-ietf-lisp-crypto-03.txt
o Posted December 2015.
o Changed cipher suite allocations. We now have 2 AES-CBC cipher
suites for compatibility, 3 AES-GCM cipher suites that are faster
ciphers that include AE and a Chacha20-Poly1305 cipher suite which
is the fastest but not totally proven/accepted..
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o Remove 1024-bit DH keys for key exchange.
o Make clear that AES and chacha20 ciphers use AEAD so part of
encrytion/decryption does authentication.
o Make it more clear that separate key pairs are used in each
direction between xTRs.
o Indicate that the IV length is different per cipher suite.
o Use a counter based IV for every packet for AEAD ciphers.
Previously text said to use a random number. But CBC ciphers, use
a random number.
o Indicate that key material is sent in network byte order (big
endian).
o Remove A-bit from Security Type LCAF. No need to do
authentication only with the introduction of AEAD ciphers. These
ciphers can do authentication. So you get ciphertext for free.
o Remove language that refers to "encryption-key" and "integrity-
key". Used term "AEAD-key" that is used by the AEAD cipher suites
that do encryption and authenticaiton internal to the cipher.
B.9. Changes to draft-ietf-lisp-crypto-02.txt
o Posted September 2015.
o Add cipher suite for Elliptic Curve 25519 DH exchange.
o Add cipher suite for Chacha20/Poly1305 ciphers.
B.10. Changes to draft-ietf-lisp-crypto-01.txt
o Posted May 2015.
o Create cipher suites and encode them in the Security LCAF.
o Add IV to beginning of packet header and ICV to end of packet.
o AEAD procedures are now part of encrpytion process.
B.11. Changes to draft-ietf-lisp-crypto-00.txt
o Posted January 2015.
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o Changing draft-farinacci-lisp-crypto-01 to draft-ietf-lisp-crypto-
00. This draft has become a working group document
o Add text to indicate the working group may work on a new data
encapsulation header format for data-plane encryption.
B.12. Changes to draft-farinacci-lisp-crypto-01.txt
o Posted July 2014.
o Add Group-ID to the encoding format of Key Material in a Security
Type LCAF and modify the IANA Considerations so this draft can use
key exchange parameters from the IANA registry.
o Indicate that the R-bit in the Security Type LCAF is not used by
lisp-crypto.
o Add text to indicate that ETRs/RTRs can negotiate less number of
keys from which the ITR/PITR sent in a Map-Request.
o Add text explaining how LISP-SEC solves the problem when a man-in-
the-middle becomes part of the Map-Request/Map-Reply key exchange
process.
o Add text indicating that when RLOC-probing is used for RLOC
reachability purposes and rekeying is not desired, that the same
key exchange parameters should be used so a reallocation of a
pubic key does not happen at the ETR.
o Add text to indicate that ECDH can be used to reduce CPU
requirements for computing shared secret-keys.
B.13. Changes to draft-farinacci-lisp-crypto-00.txt
o Initial draft posted February 2014.
Authors' Addresses
Dino Farinacci
lispers.net
San Jose, California 95120
USA
Phone: 408-718-2001
Email: farinacci@gmail.com
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Brian Weis
cisco Systems
170 West Tasman Drive
San Jose, California 95124-1706
USA
Phone: 408-526-4796
Email: bew@cisco.com
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