TCP Authentication Option: Keying Protocol Issues

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TCP Authentication OptionKeying Protocol Issues

• Joe Touch, USC/ISI

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Auth Design Team

• Input
• Multiple candidate TCP MD5 update IDs
• Bellovins requirements document
• Output
• Current TCPM ID
• Defines a TCP SA database (TSAD)
• Factors key mgt out as external
• Update to Bellovins doc
• Summary inside current TCPM ID

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Key Mgt Requirements

• Minimis variants/features
• Can be simpler than IKEv2
• Provides per-connection keys
• Socket pair keys are NOT reused (default)
• Can derive from host or hostservice keys
• Used for all intra-connection changes
• Adding new keys, deleting old ones
• Changing per-key parameters (alg, len, option
  coverage, etc.)

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TSAD Entries

• Socket pair (src dst IP, src dst port)
• Inbound
• TCP option exclusion list
• ltkey tuplegt
• Outbound
• TCP option exclusion list
• ltkey tuplegt

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Key tuple

• KeyID (optional)
• MAC algorithm
• MAC name
• MAC length
• Padding (if used)
• Key
• Value
• Length

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TSAD API

• Call
• Socket pair (connection ID)
• Source port can be 0x00 (wildcard, return all
  entries)
• Direction
• Bytes sent/received
• Used for traffic-based key rollover
• KeyID
• Return
• TCP option exclusion list
• ltkey tuplegt

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Key Management Iface

• Add/delete entry
• Entire socket pair entry
• Add/delete key tuple
• Never modify
• Anything else?
• Also need to specify 2 required MACs for TCP-AO
• Anything NOT used
• Nothing from a TCP packet (seq no, timestamp) or
  connection (ISN, etc.)

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Key mgt protocol reqts

• Negotiate TSAD entries
• Socket pair, direction, key tuples
• MAY also negotiate TCP MD5 entries (subset of
  TCP-AO entry values)
• Coordinate key tuples
• Explicit exchange
• Derivation via a group key and generation alg