HIP Working Group G. Camarillo
Internet-Draft J. Melen
Intended status: Experimental Ericsson
Expires: January 13, 2011 July 12, 2010
HIP (Host Identity Protocol) Immediate Carriage and Conveyance of Upper-
layer Protocol Signaling (HICCUPS)
draft-ietf-hip-hiccups-05
Abstract
This document defines a new HIP (Host Identity Protocol) packet type
called DATA. HIP DATA packets are used to reliably convey
authenticated arbitrary protocol messages over various overlay
networks.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background on HIP . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Message formats . . . . . . . . . . . . . . . . . . . . . 4
3.1.1. HIP fixed header . . . . . . . . . . . . . . . . . . . 4
3.1.2. HIP parameter format . . . . . . . . . . . . . . . . . 5
3.2. HIP Base Exchange, Updates, and State Removal . . . . . . 5
4. Definition of the HIP DATA Packet . . . . . . . . . . . . . . 6
4.1. Definition of the SEQ_DATA Parameter . . . . . . . . . . . 7
4.2. Definition of the ACK_DATA Parameter . . . . . . . . . . . 8
4.3. Definition of the PAYLOAD_MIC Parameter . . . . . . . . . 9
4.4. Definition of the TRANSACTION_ID Parameter . . . . . . . . 10
5. Generation and Reception of HIP DATA Packets . . . . . . . . . 10
5.1. Handling of SEQ_DATA and ACK_DATA . . . . . . . . . . . . 10
5.2. Generation of a HIP DATA packet . . . . . . . . . . . . . 11
5.3. Reception of a HIP DATA packet . . . . . . . . . . . . . . 12
5.3.1. Handling of SEQ_DATA in a Received HIP DATA packet . . 13
5.3.2. Handling of ACK_DATA in a Received HIP DATA packet . . 13
6. Use of the HIP DATA Packet . . . . . . . . . . . . . . . . . . 14
7. Security considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2. Informative references . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
Two hosts can use HIP [RFC5201] to establish a Security Association
(SA) between them in order to exchange arbitrary protocol messages
over that security association. The establishment of such a security
association involves a four-way handshake referred to as the HIP base
exchange. When handling communications between the hosts, HIP
supports mobility, multihoming, security, and NAT traversal. Some
applications require these features for their communications but
cannot accept the overhead involved in establishing a security
association (i.e., the HIP base exchange) before those communications
can start.
In this document, we define the HIP DATA packet, which can be used to
convey (in a authenticated and reliable way) protocol messages to a
remote host without running the HIP base exchange between them. The
HIP DATA packet has following semantics: unordered, duplicate free,
reliable, and authenticated message-based delivery service. We also
discuss the trade offs involved in using this packet (i.e., less
overhead but also less DoS protection) and the situations where it is
appropriate to use this packet. The HIP_DATA packet is not intended
to be a replacement for the Encapsulating Security Payload (ESP)
transport instead it SHOULD NOT be used to exchange more than a few
packets between the peers. If a continuous communication is required
or communication that requires confidentiality protection then hosts
MUST run the HIP base exchange to set up ESP security association.
Additionally APIs to higher-level protocols that might use this
service are outside of the scope of this document.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
In addition this document uses the terms defined in [RFC5201].
Message Integrity Code (MIC) is a collision-resistant hash sum
calculated over the message which is being integrity protected.
The MIC does not use secret keys and thus it needs additional
means to ensure that it has not been tampered with during
transmission. Essentially MIC is same as Message Authentication
Code (MAC) with the distinction that MIC does not use secret key.
MIC is also often referred as Integrity Check Value (ICV),
fingerprint, or unkeyed MAC.
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3. Background on HIP
The HIP protocol specification [RFC5201] defines a number of messages
and parameters. The parameters are encoded as TLVs, as shown in
Section 3.1.2. Furthermore, the HIP header carries a Next Header
field, allowing other arbitrary packets to be carried within HIP
packets.
3.1. Message formats
3.1.1. HIP fixed header
The HIP packet format consists of a fixed header followed by a
variable number of parameters. The parameter format is described in
Section 3.1.2.
The fixed header is defined in Section 5.1 of [RFC5201] and copied
below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Header Length |0| Packet Type | VER. | RES.|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | Controls |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Host Identity Tag (HIT) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver's Host Identity Tag (HIT) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ HIP Parameters /
/ /
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The HIP header is logically an IPv6 extension header. The HIP
protocol specification [RFC5201] defines handling only for Next
Header value decimal 59, IPPROTO_NONE [PROTOCOL-NUMBERS], the IPv6
'no next header' value. This document describes processing for Next
Header values other than decimal 59 which indicates that there are
either more extensions header and/or data following the HIP header.
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3.1.2. HIP parameter format
The HIP parameter format is defined in Section 5.2.1 of [RFC5201],
and copied below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |C| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ Contents /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type code for the parameter. 16 bits long, C-bit
being part of the Type code.
C Critical. One if this parameter is critical, and
MUST be recognized by the recipient, zero otherwise.
The C bit is considered to be a part of the Type
field. Consequently, critical parameters are always
odd and non-critical ones have an even value.
Length Length of the Contents, in octets.
Contents Parameter specific, defined by Type.
Padding Padding, 0-7 octets, added if needed.
3.2. HIP Base Exchange, Updates, and State Removal
The HIP base exchange is a four-message authentication and key
exchange protocol that creates shared, mutually authenticated keying
material at the communicating parties. These keying materials,
together with associated public keys and IP addresses, form a HIP
Security Association (SA). The details of the protocol are defined
in the HIP base exchange specification [RFC5201].
In addition to creating the HIP SA, the base exchange messages may
carry additional parameters that are used to create additional state.
For example, the HIP ESP specification [RFC5202] defines how HIP can
be used to create end-to-end, host-to-host IPsec ESP Security
Associations, used to carry data packets. However, it is important
to understand that the HIP base exchange is by no means bound to
IPsec; using IPsec ESP to carry data traffic forms just a baseline
and ensures interoperability between initial HIP implementations.
Once there is a HIP SA between two HIP-enabled hosts, they can
exchange further HIP control messages. Typically, UPDATE messages
are used. For example, the HIP mobility and multihoming
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specification [RFC5206] defines how to use UPDATE messages to change
the set of IP addresses associated with a HIP SA.
In addition to the base exchange and updates, the HIP base protocol
specification also defines how one can remove a HIP SA once it is no
longer needed.
4. Definition of the HIP DATA Packet
The HIP DATA packet can be used to convey protocol messages to a
remote host without running the HIP base exchange between them. HIP
DATA packets are transmitted reliably, as discussed in Section 5.
The payload of a HIP DATA packet is placed after the HIP header and
protected by a PAYLOAD_MIC parameter, which is defined in
Section 4.3. The following is the definition of the HIP DATA packet
(see definition of notation in [RFC5201] section 2.2):
Header:
Packet Type = [ TBD by IANA: 32 ]
SRC HIT = Sender's HIT
DST HIT = Receiver's HIT
IP ( HIP ( [HOST_ID, ] SEQ_DATA, PAYLOAD_MIC, [ PAYLOAD_MIC, ..., ]
HIP_SIGNATURE) PAYLOAD )
IP ( HIP ( [HOST_ID, ] SEQ_DATA, ACK_DATA, PAYLOAD_MIC,
[ PAYLOAD_MIC, ..., ] HIP_SIGNATURE) PAYLOAD )
IP ( HIP ( [HOST_ID, ] ACK_DATA, HIP_SIGNATURE))
The SEQ_DATA and ACK_DATA parameters are defined in Section 4.1 and
Section 4.2 respectively. They are used to provide a reliable
delivery of HIP DATA packets, as discussed in Section 5.
The HOST_ID parameter is defined in Section 5.2.8 of [RFC5201]. This
parameter is the sender's Host Identifier that is used to compute the
HIP DATA packet's signature and to verify it against the received
signature. The HOST_ID parameter is optional as it MAY have been
delivered using out-of-band mechanism to the receiver. If host
doesn't have reliable information that the corresponding node has its
HOST_ID it MUST always include it in to the packet. If the receiver
is unable to verify the SIGNATURE then the packet MUST be dropped and
appropriate NOTIFY packet SHOULD be sent to the sender indicating
AUTHENTICATION_FAILED as described in [RFC5201] section 5.2.16.
The PAYLOAD_MIC parameter is defined in Section 4.3. This parameter
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contains the MIC of the payload carried by the HIP DATA packet. The
PAYLOAD_MIC contains the collision-resistant hash of the payload
following after the HIP DATA. The PAYLOAD_MIC is included in the
signed part of the HIP DATA packet giving integrity protection also
for the payload carried after HIP DATA packet.
The HIP_SIGNATURE parameter is defined in Section 5.2.11. of
[RFC5201]. It contains a signature over the contents of the HIP DATA
packet. The calculation and verification of the signature is defined
Section 6.4.2. of [RFC5201]
Section 5.3 of [RFC5201] states the following:
In the future, an OPTIONAL upper-layer payload MAY follow the HIP
header. The Next Header field in the header indicates if there is
additional data following the HIP header.
We have chosen to place the payload after the HIP extension header
and only to place an MIC of the payload in to the HIP extension
header in a PAYLOAD_MIC parameter because that way the data integrity
is protected by a public key signature with the help of MIC. The
payload that is protected by the PAYLOAD_MIC parameter has been
linked to the appropriate upper-layer protocol by storing the upper-
layer protocol number, 8 octets of payload data, and by calculating a
hash sum (MIC) over the data. The HIP DATA packet MAY contain one or
more PAYLOAD_MIC parameters each bound to different next header type.
The hash algorithm used to generate MIC is same as the algorithm used
to generate the Host Identity Tag [RFC5201].
Upper-layer protocol messages, such as overlay network control
traffic, sent in HIP DATA messages may need to be matched to
different transactions. For this purpose, a DATA message MAY also
contain a TRANSACTION_ID parameter. The identifier value is a
variable length bit string in network-byte-order that is unique for
each transaction. A response to a request uses the same identifier
value allowing the receiver to match requests to responses.
4.1. Definition of the SEQ_DATA Parameter
The following is the definition of the SEQ_DATA parameter:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA:
4481 = (2^12 + 2^8 + 2^7 + 1) ]
Length 4
Sequence number 32-bit unsigned integer in network byte order which
MUST NOT reused before it has been acknowledged by
the receiver.
This parameter has critical bit set and if it is not supported by the
receiver packet MUST be dropped and appropriate NOTIFY packet SHOULD
be sent to the sender indicating UNSUPPORTED_CRITICAL_PARAMETER_TYPE
as described in [RFC5201] section 5.2.16.
4.2. Definition of the ACK_DATA Parameter
The following is the definition of the ACK_DATA parameter:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Acked Sequence number /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA:
4545 = (2^12 + 2^8 + 2^7 + 2^6 + 1) ]
Length variable (multiple of 4)
Acked Sequence number A sequence of 32-bit unsigned integers in
network byte order corresponding to the
sequence numbers being acknowledged
This parameter has critical bit set and if it is not supported by the
receiver packet MUST be dropped and appropriate NOTIFY packet SHOULD
be sent to the sender indicating UNSUPPORTED_CRITICAL_PARAMETER_TYPE
as described in [RFC5201] section 5.2.16.
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4.3. Definition of the PAYLOAD_MIC Parameter
The following is the definition of the PAYLOAD_MIC parameter:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next header | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ MIC Value /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA:
4577 = (2^12 + 2^8 + 2^7 + 2^6 + 2^5 + 1) ]
Length length in octets, excluding Type, Length, and
Padding.
Next Header Identifies the data that is protected by this MIC.
The values for this field are defined by IANA
"Protocol Numbers" [PROTOCOL-NUMBERS]
Payload Data 8 last octets of the payload data over which the
MIC is calculated. This field is used to
uniquely bind PAYLOAD_MIC parameter to next header,
in case there are multiple copies of same type.
MIC Value MIC computed over the data to which the Next
Header and Payload Data points. The size of
the MIC is the natural size of the computation
output depending on the function used.
This parameter has critical bit set and if it is not supported by the
receiver packet MUST be dropped and appropriate NOTIFY packet SHOULD
be sent to the sender indicating UNSUPPORTED_CRITICAL_PARAMETER_TYPE
as described in [RFC5201] section 5.2.16.
There is a theoretical possibility that when generating multiple
PAYLOAD_MIC parameters that will be carried in a single packet would
have identical Next Header and Payload Data fields thus it is
required that PAYLOAD_MIC parameters MUST follow the natural order of
extensions headers in the packet making it possible to bind
PAYLOD_MICs to correct payload data. In case the receiving host is
still unable to identify the payloads, it MUST drop the packet and
SHOULD send a NOTIFY packet to the sender indicating INVALID_SYNTAX
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as described in [RFC5201] section 5.2.16.
4.4. Definition of the TRANSACTION_ID Parameter
The following is the definition of the TRANSACTION_ID parameter:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA;
4580 = (2^12 + 2^8 + 2^7 + 2^6 + 2^5 + 2^2 ) ]
Length Length of the Identifier in octets
Identifier The identifier value
Padding 0-7 octets of padding if needed
Figure 1: Format of the TRANSACTION_ID parameter
5. Generation and Reception of HIP DATA Packets
HIP DATA packets are transmitted reliably. Reliable delivery is
achieved through the use of retransmissions and of the SEQ_DATA and
ACK_DATA parameters.
5.1. Handling of SEQ_DATA and ACK_DATA
A HIP DATA packet MUST contain at least one of a SEQ_DATA or an
ACK_DATA parameter; if both parameters are missing, then packet MUST
be dropped as invalid.
A HIP DATA packet containing SEQ_DATA parameter MUST contain one or
more PAYLOAD_MIC parameter or otherwise packet MUST be dropped. The
presence of a SEQ_DATA parameter indicates that the receiver MUST ACK
the HIP DATA packet. A HIP DATA packet that does not contain a
SEQ_DATA parameter is simply an ACK of a previous HIP DATA packet and
MUST NOT be ACKed.
A HIP DATA packet containing ACK_DATA parameter echoes the SEQ_DATA
sequence numbers of the HIP DATA packet packets being acknowledged.
ACK_DATA parameter MUST acknowledge at least one SEQ_DATA sequence
number and MAY acknowledge multiple SEQ_DATA sequence numbers by
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adding all of them to the ACK_DATA parameter
A HIP DATA packet MAY contain both a SEQ_DATA and an ACK_DATA
parameter. In this case, the ACK is being piggybacked on an outgoing
HIP DATA packet. In general, HIP DATA packets carrying SEQ_DATA
SHOULD be ACKed upon completion of the processing of the HIP DATA
packet. A host MAY choose to hold the HIP DATA packet carrying ACK
for a short period of time to allow for the possibility of
piggybacking the ACK parameter, in a manner similar to TCP delayed
acknowledgments.
5.2. Generation of a HIP DATA packet
When a host has upper-layer protocol data to send, it either runs the
HIP base exchange and sends the data over a SA, or sends the data
directly using a HIP DATA packet. Section 6 discusses when it is
appropriate to use each method. This section discusses the case when
the host chooses to use a HIP DATA packet to send the upper-layer
protocol data.
1. The host creates a HIP DATA packet that contains a SEQ_DATA
parameter. The host is free to choose any value for the SEQ_DATA
sequence number in the first HIP DATA packet it sends to a
destination. After that first packet, the host MUST choose the
value of the SEQ_DATA sequence number in subsequent HIP DATA
packets to the same destination so that no SEQ_DATA sequence
number is reused before the receiver has closed the processing
window for the previous packet using the same SEQ_DATA sequence
number. Practically, giving the values of the retransmission
timers used with HIP DATA packets, this means that hosts must
wait the maximum likely lifetime of the packet before reusing a
given SEQ_DATA sequence number towards a given destination.
However, it is not required for node to know the maximum packet
lifetime. Rather, it is assumed that the requirement can be met
by maintaining the value as a simple, 32-bit, "wrap-around"
counter, incremented each time a packet is sent. It is an
implementation choice whether to maintain a single counter for
the node or multiple counters (one for each source HIT,
destination HIT combination).
2. The host creates PAYLOAD_MIC parameter. MIC is a hash calculated
over the whole PAYLOAD which the Next Header field of PAYLOAD_MIC
parameter indicates. If there is multiple next header types
which the host wants to protect it SHOULD create separate
PAYLOAD_MIC parameter for each of these. The receiver MUST
validate all these MICs as described in Section 5.3.1. For
calculating MIC the host MUST use the same hash algorithm as the
one that has been used for generating the host's HIT as defined
in Section 3.2. of [RFC5201].
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3. The host creates HIP_SIGNATURE parameter. The signature is
calculated over the whole HIP envelope, excluding any parameters
after the HIP_SIGNATURE, as defined in Section 5.2.11. of
[RFC5201]. The receiver MUST validate this signature. It MAY
use either the HI in the packet or the HI acquired by some other
means.
4. The hosts sends the created HIP DATA packet and starts a DATA
timer. The default value for the timer is 3 seconds. If
multiple HIP DATA packets are outstanding, multiple timers are in
effect.
5. If the DATA timer expires, the HIP DATA packet is resent. The
HIP DATA packet can be resent DATA_RETRY_MAX times. The DATA
timer MUST be exponentially backed off for subsequent
retransmissions. If no acknowledgment is received from the peer
after DATA_RETRY_MAX times, the delivery of the HIP DATA packet
is considered unsuccessful and the application is notified about
the error. The DATA timer is canceled upon receiving an ACK from
the peer that acknowledges receipt of the HIP DATA packet. The
default value for DATA_RETRY_MAX SHOULD be 5 retries, but it MAY
be changed through local policy.
5.3. Reception of a HIP DATA packet
A host receiving a HIP DATA packet makes a decision whether to
process the packet or not. If the host, following its local policy,
suspects that this packet could be part of a DoS attack. The host
MAY respond with an R1 packet to the HIP DATA packet, if the packet
contained SEQ_DATA and PAYLOAD_MIC parameter, in order to indicate
that HIP base exchange MUST be completed before accepting payload
packets from the originator of the HIP DATA packet. If the host
chooses to respond to the HIP DATA with an R1 packet, it creates a
new R1 or selects a precomputed R1 according to the format described
in [RFC5201] Section 5.3.2. The host SHOULD drop the received data
packet if it responded with a R1 packet to the HIP_DATA packet. The
sender of HIP_DATA packet is responsible for retransmission of the
upper-layer protocol data after successful completion of the HIP Base
Exchange.
If the host, following its local policy, decides to process the
incoming HIP DATA packet, it processes it according to the following
rules:
1. If the HIP DATA packet contains a SEQ_DATA parameter and no
ACK_DATA parameter, the HIP DATA packet is processed and replied
to as described in Section 5.3.1.
2. If the HIP DATA packet contains an ACK_DATA parameter and no
SEQ_DATA parameter, the HIP DATA packet is processed as described
in Section 5.3.2.
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3. If the HIP DATA packet contains both a SEQ_DATA parameter and an
ACK_DATA parameter, the HIP DATA packet is processed first as
described in Section 5.3.2 and then the rest of the HIP DATA
packet is processed and replied to as described in Section 5.3.1.
5.3.1. Handling of SEQ_DATA in a Received HIP DATA packet
The following steps define the conceptual processing rules for
handling a SEQ_DATA parameter in a received HIP DATA packet.
The system MUST verify the SIGNATURE in the HIP DATA packet. If the
verification fail, the packet SHOULD be dropped and an error message
logged.
If the value in the received SEQ_DATA and MIC value received
PAYLOAD_MIC corresponds to a HIP DATA packet that has recently been
processed, the packet is treated as a retransmission. It is
recommended that a host cache HIP DATA packets with ACKs to avoid the
cost of generating a new ACK packet to respond to a retransmitted HIP
DATA packet. The host MUST acknowledge, again, such (apparent) HIP
DATA packet retransmissions but SHOULD also consider rate-limiting
such retransmission responses to guard against replay attacks.
The system MUST verify the PAYLOAD_MIC by calculating MIC over the
PAYLOAD which the Next Header field indicates. For calculating the
MIC the host will use the same hash algorithm that has been used to
generate the sender's HIT as defined in Section 3.2. of [RFC5201].
If the packet carried multiple PAYLOAD_MIC parameters each of them
are verified as described above. If one or more of the verification
fails, the packet SHOULD be dropped and an error message logged.
If a new SEQ parameter is being processed, the parameters in the HIP
DATA packet are then processed.
A HIP DATA packet with an ACK_DATA parameter is prepared and sent to
the peer. This ACK_DATA parameter may be included in a separate HIP
DATA packet or piggybacked in a HIP DATA packet with a SEQ_DATA
parameter. The ACK_DATA parameter MAY acknowledge more than one of
the peer's HIP DATA packets.
5.3.2. Handling of ACK_DATA in a Received HIP DATA packet
The following steps define the conceptual processing rules for
handling an ACK_DATA parameter in a received HIP DATA packet.
The system MUST verify the SIGNATURE in the HIP DATA packet. If the
verification fails, the packet SHOULD be dropped and an error message
logged.
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The sequence numbers reported in the ACK_DATA must match with an
previously sent HIP DATA packet containing SEQ_DATA that has not
already been acknowledged. If no match is found or if the ACK_DATA
does not acknowledge a new HIP DATA packets, the packet MUST either
be dropped if no SEQ_DATA parameter is present, or the processing
steps in Section 5.3.1 are followed.
The corresponding DATA timer is stopped so that the now acknowledged
HIP DATA packet is no longer retransmitted. If multiple HIP DATA
packets are newly acknowledged, multiple timers are stopped.
6. Use of the HIP DATA Packet
HIP currently requires that the four-message base exchange is
executed at the first encounter of hosts that have not communicated
before. This may add additional RTTs (Round Trip Time) to protocols
based on a single message exchange. However, the four-message
exchange is essential to preserve the DoS protection nature of the
base exchange. The use of the HIP DATA packet defined in this
document reduces the initial overhead in the communications between
two hosts. However, the HIP DATA packet itself does not provide any
protection against DoS attacks. Therefore, the HIP DATA packet MUST
only be used in environment whose policies provide protection against
DoS attacks. For example, a HIP-based overlay may have policies in
place to control which nodes can join the overlay. However,
authorization who is allowed to join the overlay is beyond the scope
of this specification. Any particular node in the overlay may want
to accept HIP DATA packets from other nodes in the overlay given that
those other nodes were authorized to join the overlay. However, the
same node will not accept HIP DATA packets from random nodes that are
not part of the overlay. Additionally, the HIP DATA packet itself
does not provide confidentiality for its payload. Therefore, the HIP
DATA packet MUST NOT be used in environments that do not provide an
appropriate level of confidentiality (e.g., a HIP-based overlay MUST
NOT send HIP DATA packets unless the connections between overlay
nodes are encrypted).
The type of data to be sent is also relevant to whether the use of a
HIP DATA packet is appropriate. HIP itself does not support
fragmentation but relies on underlying IP-layer fragmentation. This
may lead to reliability problems in the case where a message cannot
be easily split over multiple HIP messages. Therefore, applications
in environments where fragmentation could be an issue SHOULD NOT
generate too large HIP DATA packets that may lead to fragmentation.
The implementation SHOULD check the MTU of the link before sending
the packet and if the packet size is larger than MTU it SHOULD signal
to the upper-layer protocol if the packet results in to a ICMP error
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message. Note that there are environments where fragmentation is not
an issue. For example, in some HIP-based overlays, nodes can
exchange HIP DATA packets on top of TCP connections that provide
transport-level fragmentation and, thus, avoid IP-level
fragmentation.
HIP currently requires that all messages excluding I1s but including
HIP DATA packets are digitally signed. This adds to the packet size
and the processing capacity needed to send packets. However, in
applications where security is not paramount, it is possible to use
very short keys, thereby reducing resource consumption.
7. Security considerations
HIP is designed to provide secure authentication of hosts. HIP also
attempts to limit the exposure of the host to various denial-of-
service and man-in-the-middle (MitM) attacks. However, HIP DATA
packet, which can be sent without running the HIP base exchange
between hosts has a trade off that it does not provide the denial-of-
service protection or confidentiality protection that HIP generally
provides. Thus, the host should consider always situations where it
is appropriate to send or receive HIP DATA packet. If the
communication consists more than few round-trips of data or the data
is highly sensitive in nature the host SHOULD run the base exchange
with the peer host.
HIP DATA packet is designed to protect hosts from second preimage
attacks allowing receiving host to be able to detect, if the message
was tampered during the transport. This property is also know as
weak-collision-resistance. If a host tries to generate a second
preimage it would need to generate such second image where 8 last
octets are matching with original message.
When handling the PAYLOAD_MIC parameter in the receiving host, using
the 8-last octets to identify the upper layer protocol doesn't give
any guarantee that the MIC would be correct thus an attacker could
send packets where the next header and last 8-octets matches to the
values carried by PAYLOAD_MIC parameter and thus it is always
mandatory to verify the MIC value by calculating the hash over the
payload.
8. IANA considerations
This document updates the IANA Registry for HIP Packet types by
introducing new packet type for the new HIP_DATA (Section 4) packet.
This document updates the IANA Registry for HIP Parameter Types by
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introducing new parameter values for the SEQ_DATA (Section 4.1),
ACK_DATA (Section 4.2), PAYLOAD_MIC (Section 4.3), and TRANSACTION_ID
(Section 4.4) parameters.
9. Acknowledgments
Pekka Nikander was one of the original authors of the draft. Also,
in the usual IETF fashion, a large number of people have contributed
to the actual text or ideas. The list of these people include Miika
Komu, Tobias Heer, Ari Keranen, Samu Varjonen, Thomas Henderson, and
Jukka Ylitalo. Our apologies to anyone whose name is missing.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008.
[PROTOCOL-NUMBERS]
IANA, "Protocol Numbers",
<http://www.iana.org/assignments/protocol-numbers>.
10.2. Informative references
[RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the
Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 5202, April 2008.
[RFC5206] Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "End-
Host Mobility and Multihoming with the Host Identity
Protocol", RFC 5206, April 2008.
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Authors' Addresses
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: Gonzalo.Camarillo@ericsson.com
Jan Melen
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: Jan.Melen@ericsson.com
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