TCPM Working Group R. Bonica
Internet-Draft Juniper Networks
Expires: August 5, 2006 B. Weis
S. Viswanathan
Cisco Systems
A. Lange
Alcatel
O. Wheeler
BT
February 2006
Authentication for TCP-based Routing and Management Protocols
draft-bonica-tcp-auth-04
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This memo describes a TCP extension that enhances security for BGP,
LDP and other TCP-based protocols. It is intended for applications
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where secure administrative access to both the end-points of the TCP
connection is normally available. TCP peers can use this extension
to authenticate messages passed between one another.
The strategy described herein improves upon current practice, which
is described in RFC 2385. Using this new strategy, TCP peers can
update authentication keys during the lifetime of a TCP connection.
TCP peers can also use stronger authentication algorithms to
authenticate routing messages.
Table of Contents
1. Conventions Used In This Document . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Key Chain Definition . . . . . . . . . . . . . . . . . . . . . 6
6. Active Key Selection . . . . . . . . . . . . . . . . . . . . . 7
7. MAC Calculation . . . . . . . . . . . . . . . . . . . . . . . 8
8. Key Eligibility . . . . . . . . . . . . . . . . . . . . . . . 9
9. TCP Enhanced Authentication Option . . . . . . . . . . . . . . 10
10. Authentication Algorithms . . . . . . . . . . . . . . . . . . 11
11. Future Enhancements . . . . . . . . . . . . . . . . . . . . . 12
12. Implications . . . . . . . . . . . . . . . . . . . . . . . . . 12
12.1. Clock Synchronization . . . . . . . . . . . . . . . . . . 12
12.2. Connectionless Resets . . . . . . . . . . . . . . . . . . 12
12.3. Performance . . . . . . . . . . . . . . . . . . . . . . . 12
12.4. TCP Header Size . . . . . . . . . . . . . . . . . . . . . 13
12.5. Backwards Compatibility . . . . . . . . . . . . . . . . . 13
12.6. ICMP-based attacks . . . . . . . . . . . . . . . . . . . 13
12.7. Relationship With TLS . . . . . . . . . . . . . . . . . . 14
13. Operational Considerations . . . . . . . . . . . . . . . . . . 14
14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
16. Security Considerations . . . . . . . . . . . . . . . . . . . 15
17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
18.1. Normative References . . . . . . . . . . . . . . . . . . 16
18.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 19
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1. Conventions Used In This Document
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 [1].
2. Terminology
The following terms are used in this document:
key-chain - A data structure used by TCP. The key-chain is a list
of keys.
key - A member of the key-chain. Each key contains an identifier,
information that can be used to authenticate a TCP segment,
information that determines when the key can be used to
authenticate an outbound segment, and information that determines
when the key can be used to authenticate an inbound segment.
active key - A key that TCP uses to generate authentication
information for outbound segments. At any given time, zero or one
keys is active.
eligible key - A key that TCP can use to authenticate inbound
segments. At any given time, zero, one or more keys can be
eligible.
3. Introduction
RFC 2385 [7] proposes a mechanism that authenticates TCP [2] sessions
by including a message authentication code (MAC) in each TCP header.
Authentication coverage includes the following fields:
- the TCP pseudo-header
- the TCP header, excluding options, and assuming a checksum of
zero
- the TCP segment data (if any)
To spoof a connection using the scheme described above, an attacker
would not only have to guess TCP sequence numbers, but would also
have to obtain the key that was used to calculate the MAC. This key
never appears in the connection stream.
RFC 3562 [8] addresses key management considerations regarding the
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TCP MD5 Signature Option. Based upon the strength of the MD5 [9]
hashing algorithm, RFC 3562 recommends that keys be changed at least
every 90 days.
Unfortunately, the strategy described in RFC 2385 permits keys to be
changed during the lifetime of a TCP connection only so long as the
change is synchronized at both ends. This limitation has proven to
be a significant deterrent to the effective deployment of the TCP MD5
Signature Option. This memo addresses that limitation.
Also, the MD5 algorithm does not now provide a sufficient level of
security, and recently published attacks motivate its replacement.
In addition, the keyed hash MAC construction used by RFC 2385 has
serious cryptographic weaknesses. An attacker who can find a
collision in the underlying hash function can forge a MAC using a
simple chosen-message attack [10]. This memo makes use of MAC
algorithms that do not have these weaknesses. It also provides a
mechanism to add additional algorithms as the state-of-the-art in
cryptography progresses.
4. Proposal
This memo proposes a TCP Enhanced Authentication Option that is used
as follows:
Network operators associate a key-chain with each protected TCP
connection. Each key-chain includes a list of keys. Each key is
associated with a unique identifier and several other data items that
are described in Section 5 of this document.
Whenever TCP generates a segment, it searches the key-chain for an
active key. Section 6 of this document describes TCPs active key
selection criteria.
If TCP does not find an active key, it discards the outbound segment.
However, if TCP finds an active key, it executes the following
sequence:
- append the TCP Enhanced Authentication Option to the TCP header
- update the TCP Enhanced Authentication Option to include
information from the active key, including the key's unique
identifier
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- calculate a MAC using information from the active key. (See
Section 7 of this document for MAC calculation details.)
- update the TCP Enhanced Authentication Option to include
authentication information, including the MAC that was calculated
above
- calculate and update the TCP checksum
- forward the segment to a TCP peer.
The receiving TCP associates the inbound TCP segment with a local
key-chain based upon source IP address, destination IP address,
source port and destination port. It then searches the associated
key-chain for a key whose identifier matches that which was specified
by the incoming segment option. If TCP finds such a key and that key
satisfies the eligibility criteria described in Section 8 of this
document, TCP uses information from that key to calculate a MAC. If
no matching eligible key is found then TCP MUST declare an
authentication failure and discard the segment.
TCP will accept the segment if the calculated MAC matches the MAC
specified by the inbound segment. Otherwise, TCP MUST declare an
authentication failure and discard the segment.
TCP MUST also declare an authentication failure and discard a segment
if the segment is received from a connection that is associated with
a key-chain and the segment does not include the TCP Enhanced
Authentication Option.
To help protect against denial of service attacks it is RECOMMENDED
that the inbound TCP segment is validated against the normal TCP
criteria (e.g. that the segment sequence number is within the current
receive window) prior to the MAC being calculated. Inbound TCP
segments on connections requiring the Enhanced Authentication Option
MUST NOT cause the current TCP state variables for that connection to
be updated unless the MAC has been verified as correct.
An authentication failure MUST NOT produce any response back to the
sender. Routers SHOULD log authentication failures.
Unlike other TCP extensions (e.g., the Window Scale option [11]), the
absence of the option in the SYN,ACK segment must not cause the
sender to disable its sending of authentication data. This
negotiation is typically done to prevent some TCP implementations
from misbehaving upon receiving options in non-SYN segments. This is
not a problem for this option, since the SYN,ACK sent during
connection negotiation will not be signed and will thus be ignored.
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The connection will never be made, and non-SYN segments with options
will never be sent. More importantly, the sending of authentication
data must be under the complete control of the application, not at
the mercy of the remote host not understanding the option.
5. Key Chain Definition
This section describes information requirements for the key-chain.
It does not mandate any specific implementation.
A keychain is a set of up to 64 keys, where each key is {A[i], K[i],
V[i], S[i], T[i], S'[i], T'[i]}:
i Key identifier, integer (0...63)
A[i] Authentication algorithm to use with key[i].
K[i] Shared secret to use with key[i].
V[i] A vector that determines whether key[i] is to be used to
generate MACs for inbound segments, outbound segments, or both.
S[i] Start time from which key[i] can be used by sending TCPs.
T[i] End time after which key[i] cannot be used by sending TCPs.
S'[i] Start time from which key[i] can be used by receiving TCPs.
T'[i] End time after which key[i] cannot be used by receiving TCPs
For the purpose of this document, key[i] is defined as the key whose
identifer is equal to i.
A list of values for A[i] is provided in Section 10 of this document.
The format of K[i] depends upon A[i]. Also see Section 10 for
details.
A[i] and K[i] MUST be configured symmetrically on TCP peers. That
is, if key[i] is configured on two peer systems, A[i] and K[i] must
be configured identically on each system.
S[i], T[i], S'[i] and T'[i] are measured from a defined epoch that
must have a known relationship to UTC. For the purposes of
discussion, times are assumed to be measured in seconds since that
epoch, although this is not a requirement.
The range of values that can be specified for S[i], T[i], S'[i] and
T'[i] includes two special values. The first special value is called
NOW, and it represents the system time when the key is examined (as
opposed to when the key is configured). The second special value,
called INFINITY, represents a time beyond the end of the epoch.
S[i] and T[i] define a time-window during which a key can be used for
sending. S'[i] and T'[i] define a time-window during which a key can
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be used for receiving. In most configurations, the time-window
defined by S[i] and T[i] is narrower than the time-window defined by
S'[i] and T'[i] on the remote system. In some cases, defining a
narrower sending time-window determines the connection's tolerance to
clock-skew on either system.
Within a key-chain, time-windows for sending can overlap. Likewise,
within a key-chain, time-windows for receiving can overlap.
Typically, network operators will configure key-chains so that there
are no gaps between time-windows for either sending or receiving.
Implementations should issue a warning when network operators
configure key-chains with gaps between time-windows. A gap of
sufficient length can cause the TCP session to fail due to timeout.
In general, network operators should avoid reusing shared secrets.
The degree to which an operator can reuse keys is defined by local
security policy.
During the lifetime of a TCP connection, network operators may add
and delete keys from the keychain. However, the network operator
must ensure that an active key is always configured on both TCP
endpoints.
Implementations are free to implement key chains in any manner that
satisfies the above stated information requirements. For example,
implementations can translate the above stated information
requirements directly into a data structure. Alternatively, they can
implement one key-chain for sending and another for receiving. In
this case, the implementation may omit data items that do not apply
to either the sending or receiving key chain.
Likewise, implementations can implement S[i] and T[i] as a start-time
and an end-time. Alternatively, implementations can implement S[i]
and T[i] as a start-time and a duration, or they can infer the T[i]
from the S[i] of the next key.
6. Active Key Selection
The following paragraphs describe how the sending TCP selects the
active key from its key chain. Implementations SHOULD support this
key selection process; implementations MAY also support other active
key selection mechanisms as a configurable option.
First, TCP identifies all candidate keys that meet the following
requirements:
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- V[i] specifies that the key can be used for either sending or
sending and receiving
- the system time >= S[i]
- the system time < T[i]
Because the time-windows specified by S[i] and T[i] can overlap, it
is possible that multiple keys will satisfy the above stated
criteria. When this occurs, TCP chooses between the candidate keys
by applying following rules in the order that they are listed below:
- prefer the youngest key (i.e., the key whose value for S[i] is
greatest)
- When there is a tie based upon the above stated criterion,
select the key whose identifier is numerically smallest.
The selection process described above is guaranteed to return zero
or one active keys. If no active key is returned, TCP discards
the outbound TCP segment.
7. MAC Calculation
The sending TCP calculates a MAC by applying the authentication
algorithm from the active key to the following items in the order
that they are listed:
- the TCP pseudo-header
- the TCP header, assuming a checksum of zero. (See below for a
discussion of TCP Options within the the TCP header.)
- the TCP segment data (if any)
For IPv4, the pseudo-header is described in RFC 793 [2]. It includes
the 32-bit source IP address, the 32-bit destination IP address, the
zero-extended protocol number (to form 16 bits), and the 16-bit
segment length. Note that this includes use of IPv4 via IPv4-mapped
IPv6 addresses, in which case the source and destination IP addresses
are from the IPv4 portions of the IPv6 source and destination
addresses, respectively.
For IPv6, the pseudo-header is described in RFC 2460 [3]. It
includes the 128-bit source IPv6 address, the 128-bit destination
IPv6 address, the zero-extended next header value (to form 32 bits),
and the 32-bit segment length.
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The header and pseudo-header are in network byte order.
By default, for the purpose of MAC calculation, the TCP header
includes all TCP options, including the TCP Enhanced Authentication
Option with its Authentication Data Field (i.e., MAC) set to zero.
However, TCP implementations MAY omit TCP Options from the MAC
calculation. When implementation do so, they MUST set the T-bit in
the TCP Enhanced Authentication Option. See Section 9 of this
document for details.
The receiving TCP calculates the MAC in a manner identical to the
sending TCP. However, it must examine the T-bit from the incoming
TCP Enhanced Authentication Option to determine whether incoming TCP
Options should be included in the MAC calculation. See Section 9 for
details.
8. Key Eligibility
When TCP receives a segment that includes the TCP Enhanced
Authentication Option, it searches that connection's keychain for a
key whose identifier is identical to Key ID specified by the incoming
TCP Enhanced Authentication Option. TCP uses that key to
authenticate the incoming segment providing that the key is eligible
to be used.
Implementations SHOULD support the following process for determining
key eligibility; implementations MAY also support other eligible key
selection mechanisms as a configurable option.
A key is eligible if all of the following criteria are met:
- V[i] specifies that the key can be used for either receiving or
sending and receiving
- A[i] is equal to the algorithm specified by the TCP Enhanced
Authentication Option from the incoming segment
- the system time >= S'[i]
- the system time < T'[i]
If TCP does not find a key whose identifier is identical to the Key
ID specified by the incoming TCP Enhanced Authentication Option, it
MUST declare an authentication failure and discard the segment.
Likewise, TCP MUST declare an authentication failure if it finds the
key but the key is not eligible.
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9. TCP Enhanced Authentication Option
Figure 1 depicts the TCP Enhanced Authentication Option format.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Kind | Length |T|K| Alg ID |Res| Key ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Data |
| // |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Option Syntax
Kind: 8 bits
The Kind field identifies the TCP Enhanced Authentication Option.
This value will be assigned by IANA.
Length: 8 bits
The Length field specifies the length of the TCP Enhanced
Authentication Option, in octets. This count includes two octets
representing the Kind and Length fields.
The valid range for this field is from 4 to 40 octets, inclusive.
For all algorithms specified in this memo the value will be 16
octets.
T-Bit: 1 bit
The T-bit specifies whether TCP Options were omitted from the TCP
header for the purpose of MAC calculation. A value of 1 indicates
that TCP options were omitted. A value of 0 indicates that TCP
options were included. The default value is 0.
K-Bit: 1 bit
This bit is reserved for future enhancement. Its value MUST be equal
to zero. See Section 11 for details.
Alg ID: 6 bits
The Alg ID field identifies the MAC algorithm. See Section 10 for
permissible values.
Res: 2 bits
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These bits are reserved. They MUST be set to zero.
Key ID: 6 bits
The Key ID field identifies the key that was used to generate the
message digest.
Authentication Data: Variable length
The Authentication Data field contains data that is used to
authenticate the TCP segment. This data includes, but need not be
restricted to, a MAC. The length and format of the Authentication
Data Field can be derived from the Alg ID. See Section 10 for
details.
10. Authentication Algorithms
The following MAC Algorithms are suitable for use with this option.
- AES-128-CMAC-96. AES with a 128-bit key in the CMAC mode of
operation [4]. When this algorithm is used, implementations MUST
specify a value of 1 (in binary, 000001) in the TCP Enhanced
Authentication Option Alg ID field. Also, the Authentication Data
field must contain exactly 96 bits representing the MAC, truncated
to that length, with the high-order bit first. The
AES-128-CMAC-96 algorithm MUST be implemented for an
implementation to conform to this specification.
- HMAC-SHA-1-96. SHA-1 with a 160-bit key in the HMAC mode of
operation [5]. When this algorithm is used, implementations MUST
specify a value of 2 (in binary, 000010) in the TCP Enhanced
Authentication Option ALG ID field. Also, the Authentication Data
field must contain exactly 96 bits representing the MAC, truncated
to that length, with the high-order bit first. This algorithm MAY
be implemented for an implementation to conform to this
specification.
Implementations MUST present a management interface through which the
user can specify any member of the key space. For example, if the
key contains 128 bits, the command line interface might accept this
value as a string of exactly 32 hexadecimal digits, with each
hexadecimal digit representing 4 bits of the shared secret.
Implementations MAY employ authentication algorithms not listed
above.
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11. Future Enhancements
In the future, the TCP Enhanced Authentication Option will be
enhanced to support automated session key distribution. The K-bit is
reserved for the purpose of indicating that session key distribution
extensions are present. These extensions are beyond the scope of
this memo.
12. Implications
12.1. Clock Synchronization
Because the TCP Enhanced Authentication Option includes a key
identifier, the strategy described herein is immune from most
problems caused by poor clock synchronization. Clocks do not need to
be synchronized accurately between the sending and receiving systems.
The only requirements are that the key used to generate the MAC on
the sending system is also configured on the receiving system and
that the time ovelap between sender's active key and the receiver's
eligible key is great enough to compensate for clock skew.
Receipt of a segment whose authentication data was generated using a
key other than the one that is currently active on the receiving
system does not constitute an error. It may indicate only that
clocks are not synchronized between the sending and receiving
systems.
12.2. Connectionless Resets
A connectionless reset will be ignored by the receiver of the reset
if the originator of that reset does not know the key and therefore
cannot generate the proper authentication data for the segment. This
means, for example, that connection attempts by a TCP which is
generating authentication data to a port with no listener will time
out instead of being refused. Similarly, resets generated by a TCP
in response to segments sent on a stale connection will also be
ignored. Operationally this can be a problem since resets help some
protocols recover quickly from peer crashes.
12.3. Performance
The performance hit in calculating digests may inhibit the use of
this option. Performance will vary depending upon processor type,
authentication algorithm, packet size and number of MAC calculations
per second.
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12.4. TCP Header Size
As with other options that are added to every segment, the size of
the TCP Enhanced Authentication Option must be factored into the MSS
offered to the other side during connection negotiation.
Specifically, the size of the header to subtract from the MTU
(whether it is the MTU of the outgoing interface or IP's minimal MTU
of 576 octets) is now increased by the size of the TCP Enhanced
Authentication Option.
The total header size is also an issue. The TCP header specifies
where segment data starts with a 4-bit field which gives the total
size of the header (including options) in 32-byte words. This means
that the total size of the header plus options must be less than or
equal to 60 octets. This leaves 40 octets for options.
As a concrete example, assume that an implementation defaults to
sending window-scaling and timestamp information for connections it
initiates. The most loaded segment will be the initial SYN packet to
start the connection. With the TCP Enhanced Authentication Option
using AES-128-CMAC-96, the SYN packet will contain the following:
-- 4 octets MSS option
-- 4 octets window scale option (3 octets padded to 4 in many
implementations)
-- 12 bytes for timestamp
-- 16 octets for the TCP Enhanced Authentication Option
This sums to 36 octets, leaving only four octets for future
expansion.
12.5. Backwards Compatibility
On any particular TCP connection, use of the TCP Enhanced
Authentication Option precludes use of the TCP MD5 Signature Option.
However, use of the TCP Enhanced Authentication Option on one
connection does not preclude the use of the TCP MD5 Signature Option
on another connection by the same system.
12.6. ICMP-based attacks
In some cases, the strategy described herein could be used to defend
against ICMP-based attacks [12] against TCP. If ICMP implementations
were to include a sufficiently large portion of the original datagram
in the ICMP message, TCP could verify the MAC specified in the TCP
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Enhanced Authentication Option before processing the ICMP message.
Unfortunately, most ICMP implementations include only the IP header
plus first 64 bits of the IP payload in the ICMP message. TCP
Options never begin within that boundary.
12.7. Relationship With TLS
The Transport Layer Security protocol (TLS) [13] provides
confidentiality and message authentication to TCP connections.
However, TLS works above the TCP layer, and does not protect the TCP
connection itself. In contrast, the TCP Authentication Option
provides protection against attacks on the TCP layer, such as
connection reset attacks.
13. Operational Considerations
Network operators may experience an operational need to make a key
become both active and eligible immediately. In order to satisfy
this need, the network operator should execute the following
sequence:
Configure the key on both TCP peers with i equal to the lowest free
value. On both systems, set S[i] and T[i] to INFINITY. This will
cause the key to be perpetually inactive (for sending). Also set
S'[i] to NOW and T'[i] to INFINITY. This will cause the key to be
perpetually eligible (for receiving).
Once the above step has been completed, on both systems, set S[i] to
NOW. This will cause the key[i] to become active. Now it is safe to
remove or deactivate all other keys.
14. Contributors
The following individuals contributed to this document:
Chandrashekhar Appanna (achandra@cisco.com)
Andy Heffernan (ahh@juniper.net)
Kapil Jain (kapil@juniper.net)
David McGrew (mcgrew@cisco.com)
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Satish Mynam (mynam@cisco.com)
Anantha Ramaiah (ananth@cisco.com)
15. Acknowledgments
Thanks to Steve Bellovin, Ted Faber, Ross Callon, Joe Touch and Ran
Atkinson for their comments regarding this draft.
16. Security Considerations
This proposal describes a strong authentication method for
authenticating TCP segments. It defines the use of cryptographic MAC
algorithms, which are considered state-of-the-art. As such, their
expected lifetime of usefulness extends for several years. But
cryptographic algorithms have an effective lifetime, depending on
advancing processor speed and cryptographic research. This proposal
provides for the future addition of new MAC algorithms as they are
needed.
Management of RFC 2385 keys has been a significant operational
problem, both in terms of key synchronization and key selection.
Current guidance [8] warns against sharing RFC 2385 keys between
systems, and recommends changing keys according to a schedule. The
same general operational issues are relevant for the management of
MAC keys.
Because the TCP Authentication Option relies on manual configuration,
it is possible that misconfigurations will occur. We review the
scenarios and describe their impact on security.
When multiple devices are configured with the same key, it is
possible that one or more of the devices is configured to use the
wrong MAC algorithm. If the misconfigured device is using a MAC that
is significantly weaker than that used by the correctly configured
devices, where the weakness allows an attacker to recover the MAC
key, the misconfiguration reduces the security of the properly
configured devices. An attacker who can recover the key through
cryptanalysis of the weaker algorithm can use that information to
attack the stronger algorithm. For this reason, implementations
SHOULD verify the length of the keys entered into the system, and
reject keys that are too short. Implementations can detect this
misconfiguration when the MAC Algorithm ID field in the receiver's
key is compared with that in the packet. When this event is
detected, it SHOULD provide that information to an administrator,
e.g. through logging or a management interface. This attack is not
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applicable to AES-CMAC or HMAC, since neither of those MACs is
vulnerable to a key recovery attack.
When one or more devices are configured with a particular key, it is
possible that another device is configured with a slightly different
key, due to a typographical error. For example, the two keys might
differ only in a single hexadecimal digit. Message authentication
codes that are vulnerable whenever two related keys are used could be
vulnerable in this scenario. In order to protect against this
potential vulnerability, it is RECOMMENDED that no MACs with such
vulnerabilities be used. Neither AES-CMAC nor HMAC have such a
vulnerability.
17. IANA Considerations
The terms "Standards Action" and "Private Use" in this section
indicate the polices described for these terms in [6].
A new TCP Option Kind value must be defined in the IANA TCP
Parameters registry.
The option header contains an 8-bit ALG ID, for which IANA is to
create and maintain a registry entitled "MAC Algorithm IDs". This
document defines the following message authentication code types:
MAC Algorithm ID Value
---------------- -----
RESERVED 0
AES-128-CMAC-96 1
HMAC-SHA-1-96 2
Standards Action 3-47
Private Use 48-63
Note to RFC Editor: this section may be removed on publication as an
RFC.
18. References
18.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981.
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Internet-Draft TCP Enhanced Authentication Option February 2006
[3] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998.
[4] National Institute of Standards and Technology, "Recommendation
for Block Cipher Modes of Operation: The CMAC Mode for
Authentication", FIPS PUB 800-38B, May 2005, <http://
csrc.nist.gov/publications/nistpubs/800-38B/SP_800-38B.pdf>.
[5] National Institute of Standards and Technology, "The Keyed-Hash
Message Authentication Code (HMAC)", FIPS PUB 198, March 2002,
<http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf>.
[6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
18.2. Informative References
[7] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
[8] Leech, M., "Key Management Considerations for the TCP MD5
Signature Option", RFC 3562, July 2003.
[9] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[10] Bellare, M., Canetti, R., and H. Krawczyk, "Keying Hash
Functions for Message Authentication", Proceedings of
Crypto'96 , LNCS 1109, pp. 1-15., June 1996, <An extended
version of this paper is available at
http://www.research.ibm.com/security/bck2.ps>.
[11] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions for
High Performance", RFC 1323, May 1992.
[12] Gont, F., "ICMP attacks against TCP",
draft-gont-tcpm-icmp-attacks-05 (work in progress),
October 2005.
[13] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
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Authors' Addresses
Ronald P. Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
US
Email: rbonica@juniper.net
Brian Weis
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134-1706
US
Email: bew@cisco.com
Sriram Viswanathan
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Email: sriram_v@cisco.com
Andrew Lange
Alcatel
710 E. Middlefield Road
Mountain View, CA 94043
US
Email: andrew.lange@alcatel.com
Owen N. Wheeler
British Telecommunications plc
Adastral Park
Martlesham Heath
IPSWICH, Suffolk IP5 3RE
GB
Email: owen.wheeler@bt.com
Bonica, et al. Expires August 5, 2006 [Page 18]
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Bonica, et al. Expires August 5, 2006 [Page 19]
