Link-local security

1
Link-local security

• J.W. Atwood, S. Islam, S. Maziar
• PIM Working Group
• 2008/11/18
• bill_at_cse.concordia.ca

2
draft-ietf-pim-sm-linklocal-05

• Minor changes
• Introduction sets up the environment
• Notes possibility of GSAKMP for automated key
  management
• Some housekeeping
• New Stuff
• Section on Rekeying (copied from 4552)

3
Recent activity

• Attempts to get help on the environment problem
• Distributed key servers
• Router identification
• Realization that this draft is (almost)
  independent of those issues

4
Setting the Environment

• Router identification
• Controlling keys
• Controlling adjacency
• Usefulness of distributed keyservers

5
Router Identity

• A mechanism exists to give each router an
  identity
• Unique within an administrative region
• PKI, HIP, etc.
• See Router Identification Problem Statement at
  IETF-71

6
Controlling keys and adjacency

• GC/KS exists
• Assign DEKs and SAIs
• GC can answer the question, is this router a
  legitimate neighbor for me?
• A distributed key server model may be
  appropriate
• See Distributed Keyservers at IETF-71

7
Examples

• Two end cases provide the examples
• One key, one SA for the entire administrative
  region
• One key, one SA for each speaking router

8
A walk through the draft

• RFC 4601 is based on the new AH, and mandates
  authentication using AH
• We draw heavily from RFC 4552
• Specify mandatory authentication and optional
  confidentiality
• Keying
• Require manual keying
• Provide means of support for automatic keying

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Transport vs. Tunnel mode

• Two routers are acting as hosts
• MUST support transport mode
• MAY support tunnel mode

10
Authentication Confidentiality

• MUST support authentication
• MUST support ESP
• MAY support AH
• SHOULD support confidentiality
• MUST use ESP

11
IPsec requirements

• Transport mode
• Multiple SPDs
• Selectors
• Interface ID tagging
• Manual key support
• No stream ciphers
• IP encapsulation

12
Key management

• MUST support manual keying
• Do not preclude the use of IKE or GSAKMP to
  establish keys

13
Manual Key Management

• Manual configuration at boot-up
• SAD entries
• SPD entries

14
Automated Key Management

• Cannot use IKE
• Could use GDOI
• Could use GSAKMP

15
Communication Patterns

• Each speaker represents a small group
• All are sending on the same destination address
• New rules in IPsec allow using sender address and
  interface ID tag to differentiate

16
Key Server Models

• Go to regional KS for keys
• Go to local KS (the speaking router) for keys
• (allows continuing when path to regional KS is
  broken)

17
Neighbor Relationships

• Managed by regional GC
• Out of scope for this document

18
Number of Sas

• Optional one SA for each neighbor plus one for
  outgoing
• Mandatory one SA for all neighbors and one for
  outgoing

19
Rekeying

• Procedure for doing it
• Configurable KeyRolloverInterval
• Rekeying Interval
• Manual 90 days
• Automatic Will be specified by the key server
  document

20
IPsec Protection Barrier and GSPD

• Manual Keying
• SAD entries
• SPD entries

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..2

• Automatic Keying
• SAD entries (created by the automatic procedure)
• GSPD entries
• Configured send only
• Triggered by the automatic procedure
• PAD entries
• Filled by adjacency management
• Out of scope for document

22
Security Association Lookup

• Multicast lookup uses
• Sender address (not unique because of link-local
  addresses)
• Interface ID tag
• SPI

23
Activating Anti-replay

• Only recommended for automatic keying
• Keep sequence number per SA
• Keep SA per sender

24
SAD per interface

• 4601 suggests it may be desirable
• 4301 deprecates SAD per interface
• Replaced with interface ID tags for lookup

25
Extended Sequence Number

• Suggested for use with manual keying

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Security Considerations

• Limitations of manual keys
• Impersonation in single-key group
• Pointers to
• 4593 (Generic Threats to Routing Protocols)
• 5294 (Specific threats to PIM-SM)
• 4601 (PIM-SM)

27
Plans

• Tidy up a few housekeeping issues
• Listen carefully for feedback during and after
  this meeting
• Ask for WGLC, based on the next version of the
  draft

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Questions?