draft-ietf-ospf-ospfv3-auth-07.txt   draft-ietf-ospf-ospfv3-auth-08.txt 
Network Working Group M. Gupta Network Working Group M. Gupta
Internet Draft Nokia Internet Draft Tropos Networks
Document: draft-ietf-ospf-ospfv3-auth-07.txt N. Melam Document: draft-ietf-ospf-ospfv3-auth-08.txt N. Melam
Expires: August 2005 Nokia Expires: Aug 2006 Juniper Networks
February 2005 February 2006
Authentication/Confidentiality for OSPFv3 Authentication/Confidentiality for OSPFv3
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of RFC 3668. aware will be disclosed, in accordance with Section 6 of BCP 79.
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Abstract Abstract
This document describes means/mechanisms to provide This document describes means/mechanisms to provide
authentication/confidentiality to OSPFv3 using an IPv6 AH/ESP authentication/confidentiality to OSPFv3 using an IPv6 AH/ESP
Extension Header. Extension Header.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society. (2004) Copyright (C) The Internet Society (2006).
Conventions used in this document Conventions used in this document
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 RFC-2119 [N7]. document are to be interpreted as described in RFC-2119 [N7].
Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction...................................................2
2. Transport Mode vs Tunnel Mode..................................2 2. Transport Mode vs Tunnel Mode..................................3
3. Authentication.................................................3 3. Authentication.................................................3
4. Confidentiality................................................3 4. Confidentiality................................................3
5. Distinguishing OSPFv3 from OSPFv2..............................4 5. Distinguishing OSPFv3 from OSPFv2..............................4
6. IPsec Requirements.............................................4 6. IPsec Requirements.............................................4
7. Key Management.................................................5 7. Key Management.................................................5
8. SA Granularity and Selectors...................................7 8. SA Granularity and Selectors...................................7
9. Virtual Links..................................................7 9. Virtual Links..................................................7
10. Rekeying......................................................8 10. Rekeying......................................................9
10.1 Rekeying Procedure........................................8 10.1 Rekeying Procedure........................................9
10.2 KeyRolloverInterval.......................................9 10.2 KeyRolloverInterval.......................................9
10.3 Rekeying Interval.........................................9 10.3 Rekeying Interval........................................10
11. IPsec rules..................................................10 11. IPsec Protection Barrier and SPD.............................10
12. Entropy of manual keys.......................................11 12. Entropy of manual keys.......................................11
13. Replay Protection............................................11 13. Replay Protection............................................12
Security Considerations..........................................11 Security Considerations..........................................12
Normative References.............................................12 IANA Considerations..............................................13
Normative References.............................................13
Informative References...........................................13 Informative References...........................................13
Acknowledgments..................................................13 Acknowledgments..................................................14
Authors' Addresses...............................................14 Authors' Addresses...............................................14
1. Introduction 1. Introduction
OSPF (Open Shortest Path First) Version 2 [N1] defines fields AuType OSPF (Open Shortest Path First) Version 2 [N1] defines the fields
and Authentication in its protocol header in order to provide AuType and Authentication in its protocol header to provide security.
security. In OSPF for IPv6 (OSPFv3) [N2], both of the authentication In OSPF for IPv6 (OSPFv3) [N2], both of the authentication fields
fields were removed from OSPF headers. OSPFv3 relies on the IPv6 were removed from OSPF headers. OSPFv3 relies on the IPv6
Authentication Header (AH) and IPv6 Encapsulating Security Payload Authentication Header (AH) and IPv6 Encapsulating Security Payload
(ESP) to provide integrity, authentication and/or confidentiality. (ESP) to provide integrity, authentication and/or confidentiality.
This document describes how IPv6 AH/ESP extension headers can be used This document describes how IPv6 AH/ESP extension headers can be used
to provide authentication/confidentiality to OSPFv3. to provide authentication/confidentiality to OSPFv3.
It is assumed that the reader is familiar with OSPFv3 [N2], AH [N5], It is assumed that the reader is familiar with OSPFv3 [N2], AH [N5],
ESP [N4], the concept of security associations, tunnel and transport ESP [N4], the concept of security associations, tunnel and transport
mode of IPsec and the key management options available for AH and ESP mode of IPsec and the key management options available for AH and ESP
(manual keying [N3] and Internet Key Exchange (IKE)[I1]). (manual keying [N3] and Internet Key Exchange (IKE)[I1]).
2. Transport Mode vs Tunnel Mode 2. Transport Mode vs Tunnel Mode
Transport mode Security Association (SA) is generally used between The transport mode Security Association (SA) is generally used
two hosts or routers/gateways when they are acting as hosts. SA must between two hosts or routers/gateways when they are acting as hosts.
be a tunnel mode SA if either end of the security association is a The SA must be a tunnel mode SA if either end of the security
router/gateway. Two hosts MAY establish a tunnel mode SA between association is a router/gateway. Two hosts MAY establish a tunnel
themselves. OSPFv3 packets are exchanged between the routers but as mode SA between themselves. OSPFv3 packets are exchanged between
the packets are destined to the routers, the routers act like hosts routers. However, since the packets are locally delivered, the
in this case. All implementations confirming to this specification routers assume the role of hosts in the context of tunnel mode SA.
MUST support Transport mode SA to provide required IPsec security to All implementations confirming to this specification MUST support
OSPFv3 packets. They MAY also support Tunnel mode SA to provide Transport mode SA to provide required IPsec security to OSPFv3
required IPsec security to OSPFv3 packets. packets. They MAY also support Tunnel mode SA to provide required
IPsec security to OSPFv3 packets.
3. Authentication 3. Authentication
Implementations conforming to this specification MUST support Implementations conforming to this specification MUST support
Authentication for OSPFv3. Authentication for OSPFv3.
In order to provide authentication to OSPFv3, ESP MUST be supported In order to provide authentication to OSPFv3, implementations MUST
and AH MAY be supported by the implementation. support ESP and MAY support AH.
If ESP in transport mode is used, it will provide authentication to If ESP in transport mode is used, it will only provide authentication
only OSPFv3 protocol headers but not to the IPv6 header, extension to OSPFv3 protocol packet excluding the IPv6 header, extension
headers and options. headers and options.
If AH in transport mode is used, it will provide authentication to If AH in transport mode is used, it will provide authentication to
OSPFv3 protocol headers, selected portions of IPv6 header, selected OSPFv3 protocol packet, selected portions of IPv6 header, selected
portions of extension headers and selected options. portions of extension headers and selected options.
When OSPFv3 authentication is enabled, When OSPFv3 authentication is enabled,
O OSPFv3 packets that are not protected with AH or ESP MUST be O OSPFv3 packets that are not protected with AH or ESP MUST be
silently discarded. silently discarded.
O OSPFv3 packets that fail the authentication checks MUST be O OSPFv3 packets that fail the authentication checks MUST be
silently discarded. silently discarded.
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silently discarded. silently discarded.
4. Confidentiality 4. Confidentiality
Implementations conforming to this specification SHOULD support Implementations conforming to this specification SHOULD support
confidentiality for OSPFv3. confidentiality for OSPFv3.
If confidentiality is provided, ESP MUST be used. If confidentiality is provided, ESP MUST be used.
When OSPFv3 confidentiality is enabled, When OSPFv3 confidentiality is enabled,
O OSPFv3 packets that are not protected with ESP MUST be silently O OSPFv3 packets that are not protected with ESP MUST be silently
discarded. discarded.
O OSPFv3 packets that fail the confidentiality checks MUST be O OSPFv3 packets that fail the confidentiality checks MUST be
silently discarded. silently discarded.
5. Distinguishing OSPFv3 from OSPFv2 5. Distinguishing OSPFv3 from OSPFv2
The IP/IPv6 Protocol Type for OSPFv2 and OSPFv3 is same (89) and The IP/IPv6 Protocol Type for OSPFv2 and OSPFv3 is the same (89) and
OSPF distinguishes them based on the OSPF header version number. OSPF distinguishes them based on the OSPF header version number.
However current IPsec standards do not allow using arbitrary protocol However, current IPsec standards do not allow using arbitrary
specific header fields as the selectors. Therefore, in order to protocol specific header fields as the selectors. Therefore, the
distinguish OSPFv3 packets from the OSPFv2 packets, OSPF version OSPF version field in the OSPF header cannot be used in order to
field in the OSPF header cannot be used. As OSPFv2 is only for IPv4 distinguish OSPFv3 packets from OSPFv2 packets. As OSPFv2 is only
and OSPFv3 is only for IPv6, version field in IP header can be used for IPv4 and OSPFv3 is only for IPv6, version field in IP header can
to distinguish OSPFv3 packets from OSPFv2 packets. be used to distinguish OSPFv3 packets from OSPFv2 packets.
6. IPsec Requirements 6. IPsec Requirements
In order to implement this specification, the following IPsec In order to implement this specification, the following IPsec
capabilities are required. capabilities are required.
Transport Mode Transport Mode
IPsec in transport mode MUST be supported. [N3] IPsec in transport mode MUST be supported. [N3]
Traffic Selectors Multiple SPDs
The implementation MUST be able to use interface index, source The implementation MUST support multiple SPDs with a SPD selection
address, destination address, protocol and direction for choosing function that provides an ability to choose a specific SPD based
the right security action. on interface. [N3]
Selectors
The implementation MUST be able to use source address, destination
address, protocol and direction as selectors in the SPD.
Interface ID tagging
The implementation MUST be able to tag the inbound packets with
the ID of the interface (physical or virtual) via which it
arrived. [N3]
Manual key support Manual key support
Manually configured keys MUST be able to secure the specified Manually configured keys MUST be able to secure the specified
traffic. [N3] traffic. [N3]
Encryption and Authentication Algorithms Encryption and Authentication Algorithms
The implementation MUST NOT allow the user to choose stream The implementation MUST NOT allow the user to choose stream
ciphers as the encryption algorithm for securing OSPFv3 packets ciphers as the encryption algorithm for securing OSPFv3 packets
as the stream ciphers are not suitable for manual keys. since the stream ciphers are not suitable for manual keys.
Except when in conflict with the above statement, Keywords Except when in conflict with the above statement, the Keywords
"MUST", "MUST NOT", "REQUIRED", "SHOULD" and "SHOULD NOT" that "MUST", "MUST NOT", "REQUIRED", "SHOULD" and "SHOULD NOT" that
appear in the [N6] document for algorithms to be supported are to appear in the [N6] document for algorithms to be supported are to
be interpreted as described in [N7] for OSPFv3 support too. be interpreted as described in [N7] for OSPFv3 support as well.
Dynamic IPsec rule configuration Dynamic IPsec rule configuration
Routing module SHOULD be able to configure, modify and delete The routing module SHOULD be able to configure, modify and delete
IPsec rules on the fly. This is needed mainly for securing IPsec rules on the fly. This is needed mainly for securing
virtual links. virtual links.
Encapsulation of ESP packet Encapsulation of ESP packet
IP encapsulation of ESP packets MUST be supported. For IP encapsulation of ESP packets MUST be supported. For
simplicity, UDP encapsulation of ESP packets SHOULD NOT be used. simplicity, UDP encapsulation of ESP packets SHOULD NOT be used.
Different SAs for different DSCPs Different SAs for different DSCPs
As per [N3], IPsec implementation MUST support the establishment As per [N3], the IPsec implementation MUST support the
and maintenance of multiple SAs between given sender and receiver, establishment and maintenance of multiple SAs with the same
with the same selectors. This allows the implementation to put selectors between a given sender and receiver. This allows the
traffic of different classes, but with same selector values, on implementation to associate different classes of traffic with same
different SAs to support QoS appropriately. selector values in support of QoS.
7. Key Management 7. Key Management
OSPFv3 exchanges both multicast and unicast packets. While running OSPFv3 exchanges both multicast and unicast packets. While running
OSPFv3 over a broadcast interface, the authentication/confidentiality OSPFv3 over a broadcast interface, the authentication/confidentiality
required is "one to many". Since IKE is based on the Diffie-Hellman required is "one to many". Since IKE is based on the Diffie-Hellman
key agreement protocol and works only for two communicating parties, key agreement protocol and works only for two communicating parties,
it is not possible to use IKE for providing the required "one to it is not possible to use IKE for providing the required "one to
many" authentication/confidentiality. This specification mandates many" authentication/confidentiality. This specification mandates
the usage of Manual Keying to work with the current IPsec the usage of Manual Keying to work with the current IPsec
implementations. Future specifications can explore the usage of implementations. Future specifications can explore the usage of
protocols like KINK/GSAKMP as and when they are widely available. In protocols like KINK/GSAKMP when they are widely available. In manual
manual keying SAs are statically installed on the routers and these keying, SAs are statically installed on the routers and these static
static SAs are used to authenticate/encrypt the packets. SAs are used to authenticate/encrypt packets.
The following discussion explains that it is not scalable and The following discussion explains that it is not scalable and is
practically infeasible to use different security associations for practically infeasible to use different security associations for
inbound and outbound traffic in order to provide the required "one to inbound and outbound traffic to provide the required "one to many"
many" security. Therefore, the implementations MUST use manually security. Therefore, the implementations MUST use manually
configured keys with same SA for inbound and outbound traffic (as configured keys with the same SA parameters (SPI, keys etc.,) for
shown in Figure 3). both inbound and outbound SA (as shown in Figure 3).
A | A |
SAa ------------>| SAa ------------>|
SAb <------------| SAb <------------|
| |
B | B |
SAb ------------>| SAb ------------>|
SAa <------------| Figure: 1 SAa <------------| Figure: 1
| |
C | C |
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B | B |
SAb ------------>| SAb ------------>|
SAa <------------| Figure: 1 SAa <------------| Figure: 1
| |
C | C |
SAa/SAb ------------>| SAa/SAb ------------>|
SAa/SAb <------------| SAa/SAb <------------|
| |
Broadcast Broadcast
Network Network
If we consider communication between A and B in Figure 1, everything If we consider communication between A and B in Figure 1, everything
seems to be fine. A uses security association SAa for outbound seems to be fine. A uses security association SAa for outbound
packets and B uses the same for inbound packets and vice versa. Now packets and B uses the same for inbound packets and vice versa. Now
if we include C in the group and C sends a packet out using SAa then if we include C in the group and C sends a packet using SAa then only
only A will be able to understand it or if C sends the packets out A will be able to understand it. Similarly, if C sends a packet
using SAb then only B will be able to understand it. Since the using SAb then only B will be able to understand it. Since the
packets are multicast packets and they are going to be processed by packets are multicast and they are going to be processed by both A
both A and B, there is no SA for C to use so that A and B both can and B, there is no SA for C to use so that both A and B can
understand it. understand them.
A | A |
SAa ------------>| SAa ------------>|
SAb <------------| SAb <------------|
SAc <------------| SAc <------------|
| |
B | B |
SAb ------------>| SAb ------------>|
SAa <------------| Figure: 2 SAa <------------| Figure: 2
SAc <------------| SAc <------------|
| |
C | C |
SAc ------------>| SAc ------------>|
SAa <------------| SAa <------------|
SAb <------------| SAb <------------|
| |
Broadcast Broadcast
Network Network
The problem can be solved by configuring SAs for all the nodes on
The problem can be solved by configuring SAs for all the nodes on all every other node as shown in Figure 2. So A, B and C will use SAa,
the nodes as shown in Figure 2. So A, B and C will use SAa, SAb and SAb and SAc respectively for outbound traffic. Each node will lookup
SAc respectively for outbound traffic. Each node will lookup the SA the SA to be used based on the source (A will use SAb and SAc for
to be used based on the source (A will use SAb and SAc for packets packets received from B and C respectively). This solution is not
received from B and C respectively). This solution is not scalable scalable and practically infeasible because a large number of SAs
and practically infeasible because every node will need to be will need to be configured on each node. Also, the addition of a
configured with a large number of SAs and addition of a node in the node in the broadcast network will require the addition of another SA
network will cause addition of another SA on all the nodes. on every other node.
A | A |
SAs ------------>| SAo ------------>|
SAs <------------| SAi <------------|
| |
B | B |
SAs ------------>| SAo ------------>|
SAs <------------| Figure: 3 SAi <------------| Figure: 3
| |
C | C |
SAs ------------>| SAo ------------>|
SAs <------------| SAi <------------|
| |
Broadcast Broadcast
Network Network
The problem can also be solved by using the same SA for inbound and The problem can be solved by using the same SA parameters (SPI, Keys
outbound traffic as shown in Figure 3. etc.,) for both inbound (SAi) and outbound (SAo) SAs as shown in
Figure 3.
8. SA Granularity and Selectors 8. SA Granularity and Selectors
The user SHOULD be given a choice to share the same SA among multiple The user SHOULD be given the choice of sharing the same SA among
interfaces or using unique SA per interface. multiple interfaces or using a unique SA per interface.
OSPFv3 supports running multiple instances over one interface using OSPFv3 supports running multiple instances over one interface using
the "Instance Id" field contained in the OSPFv3 header. As IPsec the "Instance Id" field contained in the OSPFv3 header. As IPsec
does not support arbitrary fields in protocol header to be used as does not support arbitrary fields in protocol header to be used as
the selectors, it is not possible to use different SAs for different the selectors, it is not possible to use different SAs for different
instances of OSPFv3 running over the same interface. Therefore, all OSPFv3 instances running over the same interface. Therefore, all
the instances of OSPFv3 running over the same interface will have to OSPFv3 instances running over the same interface will have to use the
use the same SA. In OSPFv3 RFC terminology, SAs are per-link and not same SA. In OSPFv3 RFC terminology, SAs are per-link and not per-
per-interface. interface.
9. Virtual Links 9. Virtual Links
A different SA than the SA of the underlying interface MUST be
provided for virtual links. Packets sent on virtual links use
unicast non-link local IPv6 addresses as the IPv6 source address
while packets sent on other interfaces use multicast and unicast link
local addresses. This difference in the IPv6 source address
differentiates the packets sent on virtual links from other OSPFv3
interface types.
Different SA than the SA of underlying interface MUST be provided for As the virtual link end point IPv6 addresses are not known, it is not
virtual links. Packets sent out on virtual links use unicast non- possible to install SPD/SAD entries at the time of configuration.
link local IPv6 addresses as the IPv6 source address and all the The virtual link end point IPv6 addresses are learned during the
other packets use multicast and unicast link local addresses. This routing table computation process. The packet exchange over the
difference in the IPv6 source address is used in order to virtual links starts only after the discovery of the end point IPv6
differentiate the packets sent on interfaces and virtual links. addresses. In order to protect these exchanges, the routing module
must install the corresponding SPD/SAD entries before starting these
As the end point IP addresses of the virtual links are not known at exchanges. Note that manual SA parameters are preconfigured but not
the time of configuration, the secure channel for these packets needs installed in the SAD until the end point addresses are learned.
to be set up dynamically. The end point IP addresses of virtual
links are learned during the routing table build up process. The
packet exchange over the virtual links starts only after the
discovery of end point IP addresses. In order to provide security to
these exchanges, the routing module should setup a secure IPsec
channel dynamically once it acquires the required information.
According to the OSPFv3 RFC [N2], the virtual neighbor's IP address According to the OSPFv3 RFC [N2], the virtual neighbor's IP address
is set to the first prefix with the "LA-bit" set from the list of is set to the first prefix with the "LA-bit" set from the list of
prefixes in intra-area-prefix-LSAs originated by the virtual prefixes in intra-area-prefix-LSAs originated by the virtual
neighbor. But when it comes to choosing the source address for the neighbor. But when it comes to choosing the source address for the
packets that are sent over the virtual link, the RFC simply suggests packets that are sent over the virtual link, the RFC simply suggests
using one of the router's own site-local or global IPv6 addresses. using one of the router's own global IPv6 addresses. In order to
In order to install the required security rules for virtual links, install the required security rules for virtual links, the source
the source address also needs to be predictable. So the routers that address also needs to be predictable. Hence, routers that implement
implement this specification MUST change the way the source and this specification MUST change the way the source and destination
destination addresses are chosen for the packets exchanged over addresses are chosen for packets exchanged over virtual links when
virtual links when the security is enabled on that virtual link. IPsec is enabled.
The first IPv6 address with the "LA-bit" set in the list of prefixes The first IPv6 address with the "LA-bit" set in the list of prefixes
advertised in intra-area-prefix-LSAs in the transit area MUST be used advertised in intra-area-prefix-LSAs in the transit area MUST be used
as the source address for packets exchanged over the virtual link. as the source address for packets exchanged over the virtual link.
When multiple intra-area-prefix-LSAs are originated they are When multiple intra-area-prefix-LSAs are originated they are
considered as being concatenated and are ordered by ascending Link considered as being concatenated and are ordered by ascending Link
State ID. State ID.
The first IPv6 address with the "LA-bit" set in the list of prefixes The first IPv6 address with the "LA-bit" set in the list of prefixes
received in intra-area-prefix-LSAs from the virtual neighbor in the received in intra-area-prefix-LSAs from the virtual neighbor in the
transit area MUST be used as the destination address for packets transit area MUST be used as the destination address for packets
exchanged over the virtual link. When multiple intra-area-prefix- exchanged over the virtual link. When multiple intra-area-prefix-
LSAs are received they are considered as being concatenated and are LSAs are received they are considered as being concatenated and are
ordered by ascending Link State ID. ordered by ascending Link State ID.
This makes both the source and destination addresses of the packets This makes both the source and destination addresses of packets
exchanged over the virtual link, predictable on both the routers for exchanged over the virtual link predictable when IPsec is enabled.
security purposes.
10. Rekeying 10. Rekeying
To maintain the security of a link, the authentication and encryption To maintain the security of a link, the authentication and encryption
key values SHOULD be changed from time to time. key values SHOULD be changed from periodically.
10.1 Rekeying Procedure 10.1 Rekeying Procedure
The following three-step procedure SHOULD be provided to rekey the The following three-step procedure SHOULD be provided to rekey the
routers on a link without dropping OSPFv3 protocol packets or routers on a link without dropping OSPFv3 protocol packets or
disrupting the adjacency. disrupting the adjacency.
(1) For every router on the link, create an additional inbound SA for (1) For every router on the link, create an additional inbound SA for
the interface being rekeyed using a new SPI and the new key. the interface being rekeyed using a new SPI and the new key.
(2) For every router on the link, replace the original outbound SA (2) For every router on the link, replace the original outbound SA
with one using the new SPI and key values. The SA replacement with one using the new SPI and key values. The SA replacement
operation should be atomic with respect to sending OSPFv3 packets operation should be atomic with respect to sending OSPFv3 packets
on the link so that no OSPFv3 packets are sent without on the link so that no OSPFv3 packets are sent without
authentication/encryption. authentication/encryption.
(3) For every router on the link, remove the original inbound SA. (3) For every router on the link, remove the original inbound SA.
Note that all the routers on the link must complete step 1 before any Note that all routers on the link must complete step 1 before any
begin step 2. Likewise, all the routers on the link must complete begin step 2. Likewise, all the routers on the link must complete
step 2 before any begin step 3. step 2 before any begin step 3.
One way to control the progression from one step to the next is for One way to control the progression from one step to the next is for
each router to have a configurable time constant KeyRolloverInterval. each router to have a configurable time constant KeyRolloverInterval.
After the router begins step 1 on a given link, it waits for this After the router begins step 1 on a given link, it waits for this
interval and then moves to step 2. Likewise, after moving to step 2, interval and then moves to step 2. Likewise, after moving to step 2,
it waits for this interval and then moves to step 3. it waits for this interval and then moves to step 3.
In order to achieve smooth key transition, all the routers on a link In order to achieve smooth key transition, all routers on a link
should use the same value for KeyRolloverInterval, and should should use the same value for KeyRolloverInterval and should initiate
initiate the key rollover process within this time period. the key rollover process within this time period.
At the end of this procedure, all the routers will have a single At the end of this procedure, all the routers on the link will have a
inbound and outbound SA for OSPFv3 on the link with the new SPI and single inbound and outbound SA for OSPFv3 with the new SPI and key
key values. values.
10.2 KeyRolloverInterval 10.2 KeyRolloverInterval
The configured value of KeyRolloverInterval should be long enough to The configured value of KeyRolloverInterval should be long enough to
allow the administrator to change keys on all the involved routers. allow the administrator to change keys on all the OSPFv3 routers. As
As this value can vary significantly depending upon the this value can vary significantly depending upon the implementation
implementation and the deployment, it is left to the administrator to and the deployment, it is left to the administrator to choose the
choose the appropriate value. appropriate value.
10.3 Rekeying Interval 10.3 Rekeying Interval
This section analyzes the security provided by the manual keying and This section analyzes the security provided by manual keying and
recommends that the encryption and authentication keys SHOULD be recommends that the encryption and authentication keys SHOULD be
changed at least every 90 days. changed at least every 90 days.
The weakest security provided by the security mechanisms discussed in The weakest security provided by the security mechanisms discussed in
this specification is when NULL encryption (for ESP) or no encryption this specification is when NULL encryption (for ESP) or no encryption
(for AH) is used with the HMAC-MD5 authentication. Any other (for AH) is used with the HMAC-MD5 authentication. Any other
algorithm combinations will at least be as hard to break as the one algorithm combinations will at least be as hard to break as the ones
mentioned above as shown by the following examples: mentioned above. This is shown by the following reasonable
assumptions:
O NULL Encryption and HMAC-SHA-1 Authentication will be more secure O NULL Encryption and HMAC-SHA-1 Authentication will be more secure
as HMAC-SHA-1 is considered to be more secure than HMAC-MD5 as HMAC-SHA-1 is considered to be more secure than HMAC-MD5.
O NON-NULL Encryption and NULL Authentication is not applicable as O NON-NULL Encryption and NULL Authentication is not applicable as
this specification mandates the authentication when OSPFv3 security this specification mandates authentication when OSPFv3 security is
is enabled enabled.
O DES Encryption and HMAC-MD5 Authentication will be more secure O DES Encryption and HMAC-MD5 Authentication will be more secure
because of the additional security provided by DES because of the additional security provided by DES.
O Other encryption algorithms like 3DES, AES will be more secure than
DES O Other encryption algorithms like 3DES and AES will be more secure
than DES.
RFC 3562 [I4] analyzes the rekeying requirements for the TCP MD5 RFC 3562 [I4] analyzes the rekeying requirements for the TCP MD5
signature option. The analysis provided in this RFC is also signature option. The analysis provided in this RFC is also
applicable to OSPFv3 security specification as the analysis is applicable to this specification as the analysis is independent of
independent of data patterns. data patterns.
11. IPsec rules
The following set of transport mode rules can be installed in a
typical IPsec implementation to provide the
authentication/confidentiality to OSPFv3 packets.
Outbound Rules for interface running OSPFv3 security: 11. IPsec Protection Barrier and SPD
No. source destination protocol action The IPsec protection barrier MUST BE around the OSPF protocol.
1 fe80::/10 any OSPF apply Therefore, all the inbound and outbound OSPF traffic goes through
IPsec processing.
Outbound Rules for virtual links running OSPFv3 security: The SPD selection function MUST return a SPD with the following rule
for all the interfaces that have OSPFv3
authentication/confidentiality disabled.
No. source destination protocol action No. source destination protocol action
2 src/128 dst/128 OSPF apply 1 any any OSPF bypass
Inbound Rules for interface running OSPFv3 security: The SPD selection function MUST return a SPD with the following rules
for all the interfaces that have OSPFv3
authentication/confidentiality enabled.
No. source destination protocol action No. source destination protocol action
3 fe80::/10 any ESP/OSPF or AH/OSPF apply 2 fe80::/10 any OSPF protect
4 fe80::/10 any OSPF drop 3 fe80::/10 any ESP/OSPF or AH/OSPF protect
4 src/128 dst/128 OSPF protect
Inbound Rules for virtual links running OSPFv3 security: 5 src/128 dst/128 ESP/OSPF or AH/OSPF protect
No. source destination protocol action For rules 2 and 4, action "protect" means encrypting/calculating ICV
5 src/128 dst/128 ESP/OSPF or AH/OSPF apply and adding an ESP or AH header. For rules 3 and 5, action "protect"
6 src/128 dst/128 OSPF drop means decrypting/authenticating the packets and stripping the ESP or
AH header.
For outbound rules, action "apply" means encrypting/calculating ICV Rule 1 will bypass the OSPFv3 packets without any IPsec processing on
and adding ESP or AH header. For inbound rules, action "apply" means the interfaces that have OSPFv3 authentication/confidentiality
decrypting/authenticating the packets and stripping ESP or AH header. disabled.
Rules 4 and 6 are to drop the insecure OSPFv3 packets without ESP/AH Rules 2 and 4 will drop the inbound OSPFv3 packets that have not been
headers. secured with ESP/AH headers.
ESP/OSPF or AH/OSPF in rules 3 and 5 mean that it is an OSPF packet ESP/OSPF or AH/OSPF in rules 3 and 5 mean that it is an OSPF packet
secured with ESP or AH. secured with ESP or AH.
Rules 1, 3 and 4 are meant to secure the unicast and multicast OSPF Rules 2 and 3 are meant to secure the unicast and multicast OSPF
packets that are not being exchanged over the virtual links. These packets that are not being exchanged over the virtual links.
rules MUST be installed only in the security policy database (SPD) of
the interface running OSPFv3 security.
Rules 2, 5 and 6 are meant to secure the packets being exchanged over Rules 4 and 5 are meant to secure the packets being exchanged over
virtual links. These rules are dynamically installed after learning virtual links. These rules are installed after learning the virtual
the end point IP addresses of a virtual link. These rules MUST be link end point IPv6 addresses. These rules MUST be installed in the
installed on at least the interfaces that are connected to the SPD for the interfaces that are connected to the transit area for the
transit area for the virtual link. These rules MAY alternatively be virtual link. These rules MAY alternatively be installed on all the
installed on all the interfaces. If these rules are not installed on interfaces. If these rules are not installed on all the interfaces,
all the interfaces, clear text or malicious OSPFv3 packets with same clear text or malicious OSPFv3 packets with the same source and
source and destination addresses as virtual link end point addresses destination addresses as the virtual link end point IPv6 addresses
will be delivered to OSPFv3. Though OSPFv3 drops these packets will be delivered to OSPFv3. Though OSPFv3 drops these packets
because they were not received on the right interface, OSPFv3 because they were not received on the right interface, OSPFv3
receives some clear text or malicious packets even when the security receives some clear text or malicious packets even when the security
is on. Installing these rules on all the interfaces insures that is enabled. Installing these rules on all the interfaces insures
OSPFv3 does not receive these clear text or malicious packets when that OSPFv3 does not receive these clear text or malicious packets
security is turned on. On the other hand installing these rules on when security is turned enabled. On the other hand, installing these
all the interfaces increases the processing overhead on the rules on all the interfaces increases the processing overhead on the
interfaces where there is no IPsec processing otherwise. The interfaces where there is no other IPsec processing. The decision of
decision of installing these rules on all the interfaces or on just installing these rules on all the interfaces or on just the
the interfaces that are connected to the transit area is a private interfaces that are connected to the transit area is a private
decision and doesn't affect the interoperability in any way. So this decision and doesn't affect the interoperability in any way. Hence
decision is left to the implementers. it is an implementation choice.
12. Entropy of manual keys 12. Entropy of manual keys
The implementations MUST allow the administrator to configure the The implementations MUST allow the administrator to configure the
cryptographic and authentication keys in hexadecimal format instead cryptographic and authentication keys in hexadecimal format rather
of restricting it a subset of ASCII characters (letters, numbers than restricting it to a subset of ASCII characters (letters, numbers
etc). Otherwise the entropy of the keys reduces significantly as etc). A restricted character set will reduce key entropy
discussed in [I2]. significantly as discussed in [I2].
13. Replay Protection 13. Replay Protection
As it is not possible as per the current standards to provide Since it is not possible using the current standards to provide
complete replay protection while using manual keying, the proposed complete replay protection while using manual keying, the proposed
solution will not provide protection against replay attacks. solution will not provide protection against replay attacks.
Detailed analysis of various vulnerabilities of the routing protocols Detailed analysis of various vulnerabilities of the routing protocols
and OSPF in particular is discussed in [I3] and [I2], but it can be and OSPF in particular is discussed in [I3] and [I2]. The conclusion
summarized that "Replay of OSPF packets can cause adjacencies to be is that "Replay of OSPF packets can cause adjacencies to be
disrupted, which can lead to DoS attack on the network. It can also disrupted, which can lead to a DoS attack on the network. It can also
cause database exchange process to occur continuously thus causing cause database exchange process to occur continuously thus causing
CPU overload as well as micro loops in the network". CPU overload as well as micro loops in the network".
Security Considerations Security Considerations
This memo discusses the use of IPsec AH and ESP headers in order to This memo discusses the use of IPsec AH and ESP headers in order to
provide security to OSPFv3 for IPv6. Hence security permeates provide security to OSPFv3 for IPv6. Hence security permeates
throughout this document. throughout this document.
OSPF Security Vulnerabilities Analysis [I2] identifies OSPF OSPF Security Vulnerabilities Analysis [I2] identifies OSPF
vulnerabilities in two scenarios - One with no authentication or vulnerabilities in two scenarios - One with no authentication or
simple password authentication and the other with cryptographic simple password authentication and the other with cryptographic
authentication. The solution described in this specification authentication. The solution described in this specification
provides security against all the vulnerabilities identified for provides protection against all the vulnerabilities identified for
scenario with cryptographic authentication with the following scenarios with cryptographic authentication with the following
exceptions: exceptions:
Limitations of manual key: Limitations of manual key:
This specification mandates the usage of manual keys. The following This specification mandates the usage of manual keys. The following
are the known limitations of the usage of manual keys. are the known limitations of the usage of manual keys.
O As the sequence numbers can not be negotiated, replay protection O As the sequence numbers can not be negotiated, replay protection
can not be provided. This leaves OSPF insecure against all the can not be provided. This leaves OSPF insecure against all the
attacks that can be performed by replaying OSPF packets. attacks that can be performed by replaying OSPF packets.
O Manual keys are usually long lived (changing them very often is O Manual keys are usually long lived (changing them often is
a tedious task). This gives an attacker enough time to discover a tedious task). This gives an attacker enough time to discover
the keys. the keys.
O As the administrator is manually configuring the keys, there is O As the administrator is manually configuring the keys, there is
a chance that the configured keys are weak (there are known weak a chance that the configured keys are weak (there are known weak
keys for DES/3DES at least). keys for DES/3DES at least).
Impersonating Attacks: Impersonating Attacks:
The usage of the same key on all the routers on the same link for
securing OSPF leaves it insecure against impersonating attacks if one
of the routers is compromised, malfunctioning or misconfigured.
Detailed analysis of various vulnerabilities of the routing protocols The usage of the same key on all the OSPF routers connected to a link
is discussed in [I3]. leaves them all insecure against impersonating attacks if any one of
the OSPF routers is compromised, malfunctioning or misconfigured.
Detailed analysis of various vulnerabilities of routing protocols is
discussed in [I3].
IANA Considerations
This document has no IANA considerations.
This section should be removed by the RFC Editor to final
publication.
Normative References Normative References
N1. Moy, J., "OSPF version 2", RFC 2328, April 1998. N1. Moy, J., "OSPF version 2", RFC 2328, April 1998.
N2. Coltun, R., Ferguson, D. and J. Moy, "OSPF for IPv6", RFC 2740, N2. Coltun, R., Ferguson, D. and J. Moy, "OSPF for IPv6", RFC 2740,
December 1999. December 1999.
N3. Kent, S. and K. Seo, "Security Architecture for the Internet N3. Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC XXXX, date [Note to RFC-Editor: Replace XXXX with Protocol", RFC 4301, December 2005.
the number of the RFC 2401 replacement].
N4. Kent, S., "IP Encapsulating Security Payload (ESP)", RFC XXXY, N4. Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
date [Note to RFC-Editor: Replace XXXY with the number of the RFC December 2005.
2406 replacement].
N5. Kent, S., "IP Authentication Header (AH)", RFC XXXZ, date [Note to N5. Kent, S., "IP Authentication Header (AH)", RFC 4302, December
RFC-Editor: Replace XXXZ with the number of the RFC 2402 2005.
replacement].
N6. Eastlake, D., "Cryptographic Algorithm Implementation Requirements N6. Eastlake, D., "Cryptographic Algorithm Implementation Requirements
For ESP And AH", RFC XXYY, date [Note to RFC-Editor: Replace XXYY For ESP And AH", RFC 4305, December 2005.
with the number of the RFC that the draft draft-ietf-ipsec-esp-ah-
algorithms-02.txt gets].
N7. Bradner, S., "Key words for use in RFCs to Indicate Requirement N7. Bradner, S., "Key words for use in RFCs to Indicate Requirement
Level", BCP 14, RFC 2119, March 1997. Level", BCP 14, RFC 2119, March 1997.
N8. Frankel, S., Glenn, R. and S. Kelly, "The AES-CBC Cipher Algorithm N8. Frankel, S., Glenn, R. and S. Kelly, "The AES-CBC Cipher Algorithm
and Its Use with IPsec", RFC 3602, September 2003. and Its Use with IPsec", RFC 3602, September 2003.
N9. Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within ESP and N9. Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within ESP and
AH", RFC 2404, November 1998. AH", RFC 2404, November 1998.
Informative References Informative References
I1. Kaufman, C., "The Internet Key Exchange (IKEv2) Protocol", RFC I1. Kaufman, C., "The Internet Key Exchange (IKEv2) Protocol", RFC
XXZZ, date [Note to RFC-Editor: Replace XXZZ with the number of the 4306, December 2005.
RFC 2409 replacement].
I2. Jones, E. and O. Moigne, "OSPF Security Vulnerabilities Analysis", I2. Jones, E. and O. Moigne, "OSPF Security Vulnerabilities Analysis",
draft-ietf-rpsec-ospf-vuln-01.txt, work in progress. draft-ietf-rpsec-ospf-vuln-01.txt, work in progress.
I3. Barbir, A., Murphy, S. and Y. Yang, "Generic Threats to Routing I3. Barbir, A., Murphy, S. and Y. Yang, "Generic Threats to Routing
Protocols", draft-ietf-rpsec-routing-threats-07.txt, work in Protocols", draft-ietf-rpsec-routing-threats-07.txt, work in
progress. progress.
I4. Leech, M., "Key Management Considerations for the TCP MD5 I4. Leech, M., "Key Management Considerations for the TCP MD5
Signature Option", RFC 3562, July 2003. Signature Option", RFC 3562, July 2003.
Acknowledgments Acknowledgments
Authors would like to extend sincere thanks to Marc Solsona, Janne Authors would like to extend sincere thanks to Marc Solsona, Janne
Peltonen, John Cruz, Dhaval Shah, Abhay Roy, Paul Wells and Vishwas Peltonen, John Cruz, Dhaval Shah, Abhay Roy, Paul Wells, Vishwas
Manral for providing useful information and critiques in order to Manral and Sam Hartman for providing useful information and critiques
write this memo. in order to write this memo. Authors would like to extend special
thanks to Acee Lindem for lots of editorial changes.
We would also like to thank IPsec and OSPF WG people to provide We would also like to thank IPsec and OSPF WG people to provide
valuable review comments. valuable review comments.
Authors' Addresses Authors' Addresses
Mukesh Gupta Mukesh Gupta
Nokia Tropos Networks
313 Fairchild Drive 555 Del Rey Ave
Mountain View, CA 94043 Sunnyvale, CA 94085
Phone: 650-625-2264 Phone: 408-331-6889
Email: Mukesh.Gupta@nokia.com Email: mukesh.gupta@tropos.com
Nagavenkata Suresh Melam Nagavenkata Suresh Melam
Nokia Juniper Networks
313 Fairchild Drive 1194 N. Mathilda Ave
Mountain View, CA 94043 Sunnyvale, CA 94089
Phone: 650-625-2949 Phone: 408-505-4392
Email: Nagavenkata.Melam@nokia.com Email: nmelam@juniper.net
Full copyright statement Full copyright statement
Copyright (C) The Internet Society (2004). This document is subject This document is subject to the rights, licenses and restrictions
to the rights, licenses and restrictions contained in BCP 78 and contained in BCP 78, and except as set forth therein, the authors
except as set forth therein, the authors retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
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