Overview of the Mobile IPv6 Bootstrapping Problem James Kempf DoCoMo Labs USA Thursday March 10,...
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Transcript of Overview of the Mobile IPv6 Bootstrapping Problem James Kempf DoCoMo Labs USA Thursday March 10,...
Overview of the Mobile IPv6 Bootstrapping Problem
James Kempf
DoCoMo Labs USAThursday 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 prefixHome 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
Border Router
AR
AP/NAS
Access Network
Mobile Node
Internet
AAA-H
AAA-L
Terminal sends
credentials to NAS
NAS sends credentials
to local AAA
Master Key pushed to
AP
Local AAA relays
decision to NAS
NAS authorizes
Internet access
Internet Access!
Authorization Decision!
Home Network
Home Agent Address,Credentials for Mobility ServiceAuthorization,
and optional Home AddressIncluded!
Home AAA replies with
authentication and authorization
decision and Master Key
Local AAA sends
credentials to home
AAA
Mobile Node now has Home
Agent Address
and preshared
key (but not IPsec SAs)!.
Home Network
IKEv2/MIP6 Protocol Flow
Border Router
AR
AP/NAS
Access Network
Mobile Node
Internet
Home Agent
AAA-H
Mobile Node now has IPsec SAs and
Home Address.
EAPoIKEv2(Home
Address returned in
IKE CONFIG if required)
Authorization Decision!ESP +
BU/BAck for Binding
Update
See draft-ietf-mipv6-ikev2-ipsec-00.txt for IKEv2/MIP6 interaction
EAPoAAA
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?