Download PPT Version

Overview of the Mobile IPv6
Bootstrapping Problem
James Kempf
DoCoMo Labs USA
Thursday March 10, 2005
Outline
• What needs to be dynamically configured?
– Mobile IP WG calls dynamic configuration
“bootstrapping”
• What are the security problems and
measures?
• How is EAP being proposed as a solution?
• Analysis of EAP Solution
• Summary
What Needs to be
Dynamically Configured?
Bootstrapping in the Mobile IPv6
Standard
• Bootstrapping based on RFC 3775:
– Topology-dependent dynamic home agent discovery
– Authorized, dynamically autoconfigured home
address with above
– Preconfigured IKE preshared key to avoid host
certificate provisioning
 Pre-provisioned information required on Mobile
Node (best case):
 Home subnet prefix
 Home Agent/Mobile Node preshared key indexed by
NAI on Home Agent for IKEv1 Phase 1
What’s Missing?
• Topology-free dynamic Home Agent Address
discovery
• Authorized, dynamically configured home
address with above
• Credentials for IKE authorization of mobility
service are AAA-like user/password credentials
– Avoids host certificate provisioning and preconfigured
preshared key
 Pre-provisioned information required on the
Mobile Node:
 Topology-free host identifier (e.g. NAI)
 Some credentials for authorizing mobility service
through EAPoIKEv2
What Needs to Be Configured?
• Home Agent address?
– Yes, required
• Home Address?
– Possibly, but that can be configured via IKEv2 too
• IPsec SA?
– No, that should be set up using IKE
• Security credentials for IKE session?
– Depends on the deployment scenario
– Could be configured out of band or as part of the
bootstrapping process
– When EAP is used, security credentials for IKE (e.g.
preshared key) are bootstrapped too
What are the Security Problems
and Measures?
Home Agent/Mobile Node SA
Establishment
• Server to host data origin and integrity/replay
protection
– To protect a legitimate Mobile Node against rogue
Home Agents
• Host to server data origin and integrity/replay
protection, and host mobility service
authorization
– To protect Home Agent from theft or disruption of
mobility service by an attacker
• Stateless Home Agent initial transaction
– To avoid DoS state depletion attacks
• This is covered by IKEv2
Home Address Discovery
• Server to host data origin and integrity/replay
protection
– To protect a legitimate Mobile Node against rogue
Home Agents handing out bogus addresses
• Host to server data origin and integrity/replay
protection
– To protect Home Agents against unauthorized Mobile
Nodes obtaining home addresses
• This is covered by IKEv2 too
IKE Security Credentials
• Bidirectional data origin and
integrity/replay protection
– To avoid someone spoofing the credential
• Bidirectional confidentiality protection
– To avoid someone stealing the credential
• This can’t be provided by IKE because it is
used to secure IKE
NonThreats
• “Unauthorized” discovery of the Home Agent address
– Even if the address is only sent to authorized users, there is no
guarantee that an authorized user will not misuse it
•
Bogus Home Agent discovery
– If the Mobile Node is given a bogus Home Agent address, it will
not authenticate during IKEv2 transaction
• Eavesdropping to find the Home Agent address while
discovered
– Home Agent address must be the destination address on
Binding Update and so is always public
• Attacks on the Mobile Node’s home address
– The home address is typically published in the DNS anyway and
therefore is public
How is EAP being Proposed
as a Solution?
ref: draft-giaretta-mip6-authorization-eap-02.txt
EAP Configuration Protocol
Flow
NAS sends
credentials
to local
AAA
Local AAA
relays
decision to
NAS
Internet
Access!
Home AAA
replies with
authentication
and authorization
decision and
Master Key
Home Agent Address,
Credentials for Mobility
ServiceAuthorization,
and optional Home Address
Included!
Home Network
AAA-L
Border Router
Access Network
Master Key
pushed to
AP
Internet
AAA-H
AR
AP/NAS
NAS
authorizes
Internet
access
Mobile
Node now
has Home
Agent
Address
and
preshared
key (but not
IPsec SAs)!.
Terminal
sends
credentials
to NAS
Mobile Node
Authorization Decision!
Local AAA
sends
credentials
to home
AAA
IKEv2/MIP6 Protocol Flow
EAPoIKEv2
(Home
Address
returned in
IKE
CONFIG if
required)
EAPoAAA
Home Agent
AAA-H
Home Network
Border Router
Access Network
Mobile
Node now
has IPsec
SAs and
Home
Address.
Internet
AR
AP/NAS
ESP +
BU/BAck
for Binding
Update
Mobile Node
See draft-ietf-mipv6-ikev2-ipsec-00.txt for IKEv2/MIP6 interaction
Authorization Decision!
Analysis of EAP Solution
Problems Solved by EAP*
• Secure configuration of Home Agent address and home
address via EAP method
– Data origin and integrity/replay protection server to host
– Also confidentiality and host to server authentication
• Secure configuration of IKE credentials (e.g. preshared
key)
– Bidirectional confidentiality and data origin, integrity/replay
protection
– Mobility service authentication and authorization credentials are
the same as for network access
• Optimization of signaling to reduce protocol needed for
Home Agent discovery and confine it to a time when
configuration is being done anyway
– Secondary effect
*Assumes a secure, extensible EAP method!
Problems Not Solved by EAP
• Bootstrapping Home Agent address when the
Home Network Service Provider and Mobility
Service Provider are not the same
– EAP bootstrapping depends on AAA-H to provide a
Home Agent address
• Bootstrapping mobility service authorization
when the Access Service Authorizer and Mobility
Service Authorizer are not the same
– EAP bootstrapping uses network access credentials
for mobility service authorization and Home Agent
address discovery
• Bootstrapping when EAP is not used for network
access authentication and authorization
Problems Created by EAP for
Configuration
• Management of Home Agent address, IKE
session credentials, and potentially home
address information in AAA-H
– See draft-giaretta-mip6-aaa-ha-goals-00.txt for
discussion of requirements/issues
• Opens a “hole” in original design goal tightly
confining EAP for configuration to network
access keys only
– Now, IP address information is configured also
– What else will drive through that hole?
Summary
Summary
• MIP6 bootstrapping requires configuration of Home
Agent address from nontopological identity
– Home address can be configured by IKEv2
– Optional configuration of credentials for IKE session if not
preconfigured
• EAP provides a mechanism for configuring all of the
above
– Only method that can securely provision IKE session credentials
• Other methods provide mechanisms for configuring
some of the above or in cases where EAP can’t be used
The Question on Debate: Does EAP configuration provide
enough benefit to expand the current deliberately narrow
scope of applicability?
Questions/Comments?