draft-ietf-ospf-security-extension-manual-keying-05.txt   draft-ietf-ospf-security-extension-manual-keying-06.txt 
OSPF Working Group M. Bhatia OSPF Working Group M. Bhatia
Internet-Draft Alcatel-Lucent Internet-Draft Alcatel-Lucent
Intended status: Standards Track S. Hartman Intended status: Standards Track S. Hartman
Expires: November 28, 2013 Painless Security Expires: May 29, 2014 Painless Security
D. Zhang D. Zhang
Huawei Technologies co., LTD. Huawei Technologies co., LTD.
A. Lindem A. Lindem
Ericsson Ericsson
May 27, 2013 November 25, 2013
Security Extension for OSPFv2 when using Manual Key Management Security Extension for OSPFv2 when using Manual Key Management
draft-ietf-ospf-security-extension-manual-keying-05 draft-ietf-ospf-security-extension-manual-keying-06
Abstract Abstract
The current OSPFv2 cryptographic authentication mechanism as defined The current OSPFv2 cryptographic authentication mechanism as defined
in the OSPF standards is vulnerable to both inter-session and intra- in RFC 2328 and RFC 5709 is vulnerable to both inter-session and
session replay attacks when its uses manual keying. Additionally, intra-session replay attacks when using manual keying. Additionally,
the existing cryptographic authentication schemes do not cover the IP the existing cryptographic authentication schemes do not cover the IP
header. This omission can be exploited to carry out various types of header. This omission can be exploited to carry out various types of
attacks. attacks.
This draft proposes changes to the authentication sequence number This draft proposes changes to the authentication sequence number
mechanism that will protect OSPFv2 from both inter-session and intra- mechanism that will protect OSPFv2 from both inter-session and intra-
session replay attacks when its using manual keys for securing its session replay attacks when using manual keys for securing OSPFv2
protocol packets. Additionally, we also describe some changes in the protocol packets. Additionally, we also describe some changes in the
cryptographic hash computation so that we eliminate most attacks that cryptographic hash computation so that we eliminate most attacks that
result because OSPFv2 does not protect the IP header. result from OSPFv2 not protecting the IP header.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 28, 2013. This Internet-Draft will expire on May 29, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Section . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Section . . . . . . . . . . . . . . . . . . . 3
1.2. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 4 1.2. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 4
2. Replay Protection using Extended Sequence Numbers . . . . . . 4 2. Replay Protection using Extended Sequence Numbers . . . . . . 4
3. OSPF Packet Extensions . . . . . . . . . . . . . . . . . . . . 5 3. OSPF Packet Extensions . . . . . . . . . . . . . . . . . . . . 5
4. OSPF Packet Key Selection . . . . . . . . . . . . . . . . . . 6 4. OSPF Packet Key Selection . . . . . . . . . . . . . . . . . . 6
4.1. Key Selection for Unicast OSPF Packet Transmission . . . . 7 4.1. Key Selection for Unicast OSPF Packet Transmission . . . . 7
4.2. Key Selection for Multicast OSPF Packet Transmission . . . 7 4.2. Key Selection for Multicast OSPF Packet Transmission . . . 8
4.3. Key Selection for OSPF Packet Reception . . . . . . . . . 8 4.3. Key Selection for OSPF Packet Reception . . . . . . . . . 8
5. Securing the IP header . . . . . . . . . . . . . . . . . . . . 8 5. Securing the IP header . . . . . . . . . . . . . . . . . . . . 9
6. Mitigating Cross-Protocol Attacks . . . . . . . . . . . . . . 9 6. Mitigating Cross-Protocol Attacks . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11 9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The OSPFv2 cryptographic authentication mechanism as described in The OSPFv2 cryptographic authentication mechanism as described in
[RFC2328] uses per-packet sequence numbers to provide protection [RFC2328] uses per-packet sequence numbers to provide protection
against replay attacks. The sequence numbers increase monotonically against replay attacks. The sequence numbers increase monotonically
so that the attempts to replay the stale packets can be thwarted. so that attempts to replay the stale packets can be thwarted. The
The sequence number values are maintained as a part of adjacency sequence number values are maintained as a part of adjacency states.
states. Therefore, if an adjacency is broken down, the associated Therefore, if an adjacency is taken down, the associated sequence
sequence numbers get reinitialized and the neighbors start all over numbers get reinitialized and the neighbors start all over again.
again. Additionally, the cryptographic authentication mechanism does Additionally, the cryptographic authentication mechanism does not
not specify how to deal with the rollover of a sequence number when specify how to deal with the rollover of a sequence number when its
its value would wrap. These omissions can be taken advantage of by value wraps. These omissions can be taken advantage of by attackers
attackers to implement various replay attacks ([RFC6039]). In order to implement various replay attacks ([RFC6039]). In order to address
to address these issues, we propose extensions to the authentication these issues, we propose extensions to the authentication sequence
sequence number mechanism. Compared with the cryptographic number mechanism.
authentication mechanism proposed in [RFC5709], the solution proposed
does not impose any more security presumption.
The cryptographic authentication as described in [RFC2328] and later The cryptographic authentication as described in [RFC2328] and later
updated in [RFC5709] does not include the IP header. This also can updated in [RFC5709] does not include the IP header. This also can
be exploited to launch several attacks as the source address in the be exploited to launch several attacks as the source address in the
IP header is no longer protected. The OSPF specification, for IP header is no longer protected. The OSPF specification, for
broadcast and NBMA (Non-Broadcast Multi-Access Networks), requires broadcast and NBMA (Non-Broadcast Multi-Access Networks), requires
the implementations to look at the source address in the IP header to implementations to look at the source address in the IP header to
determine the neighbor from witch the packet was received. Changing determine the neighbor from which the packet was received. Changing
the IP source address of a packet which can confuse the receiver and the IP source address of a packet that confuses the receiver and can
can be exploited to produce a number of denial of service attacks be exploited to produce a number of denial of service attacks
[RFC6039]. If the packet is interpreted as coming from a different [RFC6039]. If the packet is interpreted as coming from a different
neighbor, the sequence number received from the neighbor may be neighbor, the sequence number received from the neighbor may be
updated. This may disrupt communication with the legitimate updated. This may disrupt communication with the legitimate
neighbor. Hello packets may be reflected to cause a neighbor to neighbor. Hello packets may be reflected to cause a neighbor to
appear to have one-way communication. Old Database descriptions may appear to have one-way communication. Additionally, Database
be reflected in cases where the per-packet sequence numbers are Description packets may be reflected in cases where the per-packet
sufficiently divergent in order to disrupt an adjacency [RFC6863]. sequence numbers are sufficiently divergent in order to disrupt an
This is referred to as the IP layer issue in [RFC6862]. adjacency [RFC6863]. This is referred to as the IP layer issue in
[RFC6862].
[RFC2328] states that implementations MUST offer keyed MD5 [RFC2328] states that implementations MUST offer keyed MD5
authentication. It is likely that this will be deprecated in favor authentication. It is likely that this will be deprecated in favor
of the stronger algorithms described in [RFC5709] in future of the stronger algorithms described in [RFC5709] and required in
deployments [RFC6094]. [RFC6094].
This draft proposes a few simple changes to the cryptographic This draft proposes a few simple changes to the cryptographic
authentication mechanism, as currently described in [RFC5709], to authentication mechanism, as currently described in [RFC5709], to
prevent such IP layer attacks. prevent such IP layer attacks.
1.1. Requirements Section 1.1. Requirements Section
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119]. document are to be interpreted as described in RFC2119 [RFC2119].
skipping to change at page 4, line 30 skipping to change at page 4, line 25
2. Replay Protection using Extended Sequence Numbers 2. Replay Protection using Extended Sequence Numbers
In order to provide replay protection against both inter-session and In order to provide replay protection against both inter-session and
intra-session replay attacks, the OSPFv2 sequence number is expanded intra-session replay attacks, the OSPFv2 sequence number is expanded
to 64-bits with the least significant 32-bit value containing a to 64-bits with the least significant 32-bit value containing a
strictly increasing sequence number and the most significant 32-bit strictly increasing sequence number and the most significant 32-bit
value containing the boot count. OSPFv2 implementations are required value containing the boot count. OSPFv2 implementations are required
to retain the boot count in non-volatile storage for the deployment to retain the boot count in non-volatile storage for the deployment
life the OSPF router. The requirement to preserve the boot count is life the OSPF router. The requirement to preserve the boot count is
also placed on SNMP agents by the SNMPv3 security architecture (refer also placed on SNMP agents by the SNMPv3 security architecture (refer
to snmpEngineBoots in [RFC4222]. to snmpEngineBoots in [RFC4222]).
Since there is no room in the OSPFv2 packet for a 64-bit sequence Since there is no room in the OSPFv2 packet for a 64-bit sequence
number, it will occupy the 8 octets following the OSPFv2 packet and number, it will occupy the 8 octets following the OSPFv2 packet and
MUST be included when calculating the OSPFv2 packet digest. These MUST be included when calculating the OSPFv2 packet digest. These
additional 8 bytes are not included in the OSPFv2 packet header additional 8 bytes are not included in the OSPFv2 packet header
length but are included in the OSPFv2 header Authentication Data length but are included in the OSPFv2 header Authentication Data
length and the IPv4 packet header length. length and the IPv4 packet header length.
The lower order 32-bit sequence number MUST be incremented for every The lower order 32-bit sequence number MUST be incremented for every
OSPF packet sent by the OSPF router. Upon reception, the sequence OSPF packet sent by the OSPF router. Upon reception, the sequence
number MUST be greater than the sequence number in the last OSPF number MUST be greater than the sequence number in the last OSPF
packet of that type accepted from the sending OSPF neighbor. packet of that type accepted from the sending OSPF neighbor.
Otherwise, the OSPF packet is considered a replayed packet and Otherwise, the OSPF packet is considered a replayed packet and
dropped. OSPF packets of different types may arrive out of order if dropped. OSPF packets of different types may arrive out of order if
they are priorized as recommended in [RFC3414]. they are prioritized as recommended in [RFC3414].
OSPF routers implementing this specification MUST use available OSPF routers implementing this specification MUST use available
mechanisms to preserve the sequence number's strictly increasing mechanisms to preserve the sequence number's strictly increasing
property for the deployed life of the OSPFv3 router (including cold property for the deployed life of the OSPFv3 router (including cold
restarts). This is achieved by maintaining a boot count in non- restarts). This is achieved by maintaining a boot count in non-
volatile storage and incrementing it each time the OSPF router loses volatile storage and incrementing it each time the OSPF router loses
its prior sequence number state. The SNMPv3 snmpEngineBoots variable its prior sequence number state. The SNMPv3 snmpEngineBoots variable
[RFC4222] MAY be used for this purpose. However, maintaining a [RFC4222] MAY be used for this purpose. However, maintaining a
separate boot count solely for OSPF sequence numbers has the separate boot count solely for OSPF sequence numbers has the
advantage of decoupling SNMP reinitialization and OSPF advantage of decoupling SNMP reinitialization and OSPF
skipping to change at page 6, line 35 skipping to change at page 6, line 35
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Boot Count) | | Sequence Number (Boot Count) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Strictly Increasing Packet Counter) | | Sequence Number (Strictly Increasing Packet Counter) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
~ Authentication Data ~ ~ Authentication Data ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 - Extended Sequence Number Packet Extensions Figure 1 - Extended Sequence Number Packet Extensions
4. OSPF Packet Key Selection 4. OSPF Packet Key Selection
This section describes how the proposed security solution selects This section describes how the proposed security solution selects
long-lived keys from key tables. [I-D.ietf-karp-crypto-key-table]. long-lived keys from key tables. [I-D.ietf-karp-crypto-key-table].
Generally, a key used for OSPFv2 packet authentication should satisfy Generally, a key used for OSPFv2 packet authentication should satisfy
the following requirements: the following requirements:
o For packet transmission, the key validity interval as defined by o For packet transmission, the key validity interval as defined by
SendLifeTimeStart and SendLifeTimeEnd must include the current SendLifetimeStart and SendLifetimeEnd must include the current
time. time.
o For packet reception, the key validity interval as defined by o For packet reception, the key validity interval as defined by
AcceptLifeTimeStart and AcceptLifeTimeEnd must include the current AcceptLifetimeStart and AcceptLifetimeEnd must include the current
time. time.
o The key can be used for the desired security algorithm. o The key must be valid for the desired security algorithm.
In the remainder of this section, additional requirements for keys In the remainder of this section, additional requirements for keys
are enumerated for different scenarios. are enumerated for different scenarios.
4.1. Key Selection for Unicast OSPF Packet Transmission 4.1. Key Selection for Unicast OSPF Packet Transmission
Assume that a router R1 tries to send a unicast OSPF packet from its Assume that a router R1 tries to send a unicast OSPF packet from its
interface I1 to the interface R2 of a remote router R2 using security interface I1 to the interface R2 of a remote router R2 using security
protocol P via interface I at time T. First, consider the protocol P via interface I at time T. First, consider the
circumstances where R1 and R2 are not connected with a virtual link. circumstances where R1 and R2 are not connected with a virtual link.
R1 then needs to select a long long-lived symmetric key from its key R1 then needs to select a long long-lived symmetric key from its key
table. Because the key should be shared by the by both R1 and R2 to table. Because the key should be shared by the by both R1 and R2 to
protect the communication between I1 and I2, the key should satisfy protect the communication between I1 and I2, the key should satisfy
the following requirements: the following requirements:
o The Peers field is unused. OSPF authentiction is interface based. o The Peers field is unused. OSPF authentication is interface
based.
o The Interfaces field includes the local IP address of the o The Interfaces field includes the local IP address of the
interface for nummbered interfaces or the MIB-II [RFC1213], interface for numbered interfaces or the MIB-II [RFC1213], ifIndex
ifIndex for unnumbered interfaces. for unnumbered interfaces.
o The Direction field is either "out" or "both". o The Direction field is either "out" or "both".
o If multiple keys match the Interface, the key with the most recent
SendLifetimeStart time will be selected. This will facilitate
graceful key rollover.
o The Key ID field in the OSPFv2 header (refer to figure 1) will be
set to the selected key's LocalKeyName.
When R1 and R2 are connected to a virtual link, the interfaces field When R1 and R2 are connected to a virtual link, the interfaces field
must identify the virtual endpoint rather than the virtual link. must identify the virtual endpoint rather than the virtual link.
Since there may be virtual links to the same router, the transit area Since there may be virtual links to the same router, the transit area
ID must be part of the identifier. Hence, the key should satisfy the ID must be part of the identifier. Hence, the key should satisfy the
following requirements: following requirements:
o The Peers field is unused. OSPF authentiction is interface based. o The Peers field is unused. OSPF authentication is interface
based.
o The Interfaces field includes both the virtual endpoint's OSPF o The Interfaces field includes both the virtual endpoint's OSPF
router ID and the the transit area ID for the virtual link. router ID and the transit area ID for the virtual link.
o The Direction field is either "out" or "both". o The Direction field is either "out" or "both".
o If multiple keys match the Interface, the key with the most recent
SendLifetimeStart time will be selected. This will facilitate
graceful key rollover.
o The Key ID field in the OSPFv2 header (refer to figure 1) will be
set to the selected key's LocalKeyName.
4.2. Key Selection for Multicast OSPF Packet Transmission 4.2. Key Selection for Multicast OSPF Packet Transmission
If a router R1 sends an OSPF packet from its interface I1 to a If a router R1 sends an OSPF packet from its interface I1 to a
multicast address (e.g., AllSPFRouters, AllDRouters), it needs to multicast address (e.g., AllSPFRouters, AllDRouters), it needs to
select a key according to the following requirements: select a key according to the following requirements:
o The Peers field is unused. OSPF authentication is interface o The Peers field is unused. OSPF authentication is interface
based. based.
o The Interfaces field includes the local IP address of the o The Interfaces field includes the local IP address of the
interface for nummbered interfaces or the MIB-II [RFC1213], interface for numbered interfaces or the MIB-II [RFC1213], ifIndex
ifIndex for unnumbered interfaces. for unnumbered interfaces.
o The Direction field is either "out" or "both". o The Direction field is either "out" or "both".
o If multiple keys match the Interface, the key with the most recent
SendLifetimeStart time will be selected. This will facilitate
graceful key rollover.
o The Key ID field in the OSPFv2 header (refer to figure 1) will be
set to the selected key's LocalKeyName.
4.3. Key Selection for OSPF Packet Reception 4.3. Key Selection for OSPF Packet Reception
When Cryptographic Authentication is used, the ID of the When Cryptographic Authentication is used, the ID of the
authentication key is included in the authentication field of the authentication key is included in the authentication field of the
OSPF packet header. Using this key ID, it is relatively easy for a OSPF packet header. Using this key ID, it is relatively easy for a
receiver to locate the key. The simple requirements are: receiver to locate the key. The simple requirements are:
o The interface on which the key was received is associated with the o The interface on which the key was received is associated with the
key's interface. key's interface.
o The PeerKeyName field includes the key ID obtained from the o The Key ID obtained from the OSPFv2 packet header corresponds to
authentication field. Since OSPF keys are symmetric, the the neighbor's PeerKeyName. Since OSPFv2 keys are symmetric, the
LocalKeyName and PeerKeyName for OSPF keys will be identical. LocalKeyName and PeerKeyName for OSPFv2 keys will be identical.
Hence, the Key ID will be used to select the correct local key.
o The Direction field is either "in" or "both". o The Direction field is either "in" or "both".
5. Securing the IP header 5. Securing the IP header
This document updates the definition of Apad which is currently a This document updates the definition of Apad which is currently a
constant defined in [RFC5709] to the source address from the IP constant defined in [RFC5709] to the source address from the IP
header of the OSPFv2 protocol packet. The overall cryptographic header of the OSPFv2 protocol packet. The overall cryptographic
authentication process defined in [RFC5709] remains unchanged. To authentication process defined in [RFC5709] remains unchanged. To
reduce the potential for confusion, this section minimizes the reduce the potential for confusion, this section minimizes the
skipping to change at page 9, line 10 skipping to change at page 9, line 38
change of IP source address in a replayed packet can be detected. change of IP source address in a replayed packet can be detected.
At the receiving end, implementations MUST initialize Apad as the At the receiving end, implementations MUST initialize Apad as the
source address from IP Header of the incoming OSPFv2 packet, repeated source address from IP Header of the incoming OSPFv2 packet, repeated
L/4 times, instead of the constant that's currently defined in L/4 times, instead of the constant that's currently defined in
[RFC5709]. Besides changing the value of Apad, this document does [RFC5709]. Besides changing the value of Apad, this document does
not introduce any other changes to the authentication mechanism not introduce any other changes to the authentication mechanism
described in [RFC5709]. This would prevent all attacks where a rogue described in [RFC5709]. This would prevent all attacks where a rogue
OSPF router changes the IP source address of an OSPFv2 packet and OSPF router changes the IP source address of an OSPFv2 packet and
replays it on the same multi-access interface or another interface replays it on the same multi-access interface or another interface
since the IP source address is now protected and such changes would since the IP source address is now protected and modification would
cause the authentication check to fail and the replayed packet to be result in the OSPFv2 packet being dropped due to an authentication
rejected. failure.
6. Mitigating Cross-Protocol Attacks 6. Mitigating Cross-Protocol Attacks
In order to prevent cross protocol replay attacks for protocols In order to prevent cross protocol replay attacks for protocols
sharing common keys, the two octet OSPFv2 Cryptographic Protocol ID sharing common keys, the two octet OSPFv2 Cryptographic Protocol ID
is appended to the authentication key prior to use. Refer to IANA is appended to the authentication key prior to use. Refer to IANA
Considerations (Section 8). Considerations (Section 8).
[RFC5709], Section 3.3 describes the mechanism to prepare the key [RFC5709], Section 3.3 describes the mechanism to prepare the key
used in the hash computation. This document updates the sub section used in the hash computation. This document updates the sub section
skipping to change at page 9, line 47 skipping to change at page 10, line 27
Protocol-Specific Authentication Key (Ks) is less than L octets long, Protocol-Specific Authentication Key (Ks) is less than L octets long,
then Ko is set to the Protocol-Specific Authentication Key (Ks) with then Ko is set to the Protocol-Specific Authentication Key (Ks) with
zeros appended to the end of the Protocol-Specific Authentication Key zeros appended to the end of the Protocol-Specific Authentication Key
(Ks) such that Ko is L octets long. (Ks) such that Ko is L octets long.
Once the cryptographic key (Ko) used with the hash algorithm is Once the cryptographic key (Ko) used with the hash algorithm is
derived the rest of the authentication mechanism described in derived the rest of the authentication mechanism described in
[RFC5709] remains unchanged other than one detail that was [RFC5709] remains unchanged other than one detail that was
unspecified. When XORing Ko and Ipad of Opad, Ko MUST be padded with unspecified. When XORing Ko and Ipad of Opad, Ko MUST be padded with
zeros to the length of Ipad or Opad. It is expected that RFC 5709 zeros to the length of Ipad or Opad. It is expected that RFC 5709
[RFC5709] implementation perform this padding implicitly. [RFC5709] implementations perform this padding implicitly.
7. Security Considerations 7. Security Considerations
This document attempts to fix the manual key management procedure This document rectifies the manual key management procedure that
that currently exists within OSPFv2, as part of the Phase 1 of the currently exists within OSPFv2, as part of the Phase 1 of the KARP
KARP Working Group. Therefore, only the OSPFv2 manual key management Working Group. Therefore, only the OSPFv2 manual key management
mechanism is considered. Any solution that takes advantage of the mechanism is considered. Any solution that takes advantage of the
automatic key management mechanism is beyond the scope of this automatic key management mechanism is beyond the scope of this
document. document.
The proposed sequence number extension offers most of the benefits of The proposed sequence number extension offers most of the benefits of
of more complicated mechanisms involving challenges. There are, more complicated mechanisms involving challenges. There are,
however, a couple drawbacks to this approach. First, it requires the however, a couple drawbacks to this approach. First, it requires the
OSPF implementation to be able to save its boot count in non-volatile OSPF implementation to be able to save its boot count in non-volatile
storage. If the non-volatile storage is ever repaired or upgraded storage. If the non-volatile storage is ever repaired or upgraded
such that the contents are lost or the OSPFv2 router is replaced with such that the contents are lost or the OSPFv2 router is replaced, the
a model, the keys MUST be changed to prevent replay attacks. keys MUST be changed to prevent replay attacks.
Second, if a router is taken out of service completely (either Second, if a router is taken out of service completely (either
intentionally or due to a persistent failure), the potential exists intentionally or due to a persistent failure), the potential exists
for reestablishment of an OSPFv2 adjacency by replaying the entire for reestablishment of an OSPFv2 adjacency by replaying the entire
OSPFv2 session establishment. This scenario is however, extremely OSPFv2 session establishment. This scenario is however, extremely
unlikely, since it would imply an identical OSPFv2 adjacency unlikely, since it would imply an identical OSPFv2 adjacency
formation packet exchange. The replay of OSPFv2 hello packets alone formation packet exchange. Without adjacency formation, the replay
for an OSPFv2 router that has been taken out of service should not of OSPFv2 hello packets alone for an OSPFv2 router that has been
result in any serious attack as the only consequence is superfluous taken out of service should not result in any serious attack as the
processing. Of course, this attack could also be thwarted by only consequence is superfluous processing. Of course, this attack
changing the relevant manual keys. could also be thwarted by changing the relevant manual keys.
This document also provides a solution to prevent certain denial of This document also provides a solution to prevent certain denial of
service attacks that can be launched by changing the source address service attacks that can be launched by changing the source address
in the IP header of the OSPFv2 protocol packet. in the IP header of an OSPFv2 protocol packet.
8. IANA Considerations 8. IANA Considerations
This document requests a new code point from the "OSPF Shortest Path This document requests a new code point from the "OSPF Shortest Path
First (OSPF) Authentication Codes" registry: First (OSPF) Authentication Codes" registry:
o 3 - Cryptographic Authentication with Extended Sequence Numbers. o 3 - Cryptographic Authentication with Extended Sequence Numbers.
This document also requests a new code point from the "Authentication This document also requests a new code point from the "Authentication
Cryptographic Protocol ID" registry defined under "Keying and Cryptographic Protocol ID" registry defined under "Keying and
skipping to change at page 13, line 7 skipping to change at page 13, line 32
Beijing, Beijing,
China China
Phone: Phone:
Fax: Fax:
Email: zhangdacheng@huawei.com Email: zhangdacheng@huawei.com
URI: URI:
Acee Lindem Acee Lindem
Ericsson Ericsson
102 Carric Bend Court 301 Midenhall Way
Cary, NC 27519 Cary, NC 27513
USA USA
Phone: Phone:
Email: acee.lindem@ericsson.com Email: acee.lindem@ericsson.com
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