Session Initiation Protocol Security Mechanisms

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Session Initiation Protocol Security Mechanisms

• Prantap Bedi

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Session Initiation Protocol

• IETF RFC protocol standard for signaling
• Set up and tear down VoIP connections
• Versatile, Scalable, Extensible, Simple
• sipusera_at_somehost.en

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SIP Architecture

• Four major components
• User Agents
• Registrar Servers
• Proxy Servers
• Redirect Servers

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SIP Architecture
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Current Internet Security Requirements

• How are they exploited?
• Authentication
• Authorization
• Confidentiality
• Integrity
• Non-repudiation
• Availability
• Possible Attacks

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SIPs Internal Security Mechanisms

• HTTP 1.1 Digest
• SIPS
• S/MIME

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HTTP 1.1 Digest
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SIPS

• SIP Secure
• Similar to HTTPS
• A difference between SIP and SIPS is in the
  address field sipsbob_at_zhwin.ch
• Uses MIME bodies and TLS to ensure integrity and
  confidentiality

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S/MIME

• End-to-end protocol inherited from SMTP
• Message bodies are signed using the private key
  of the sender and encrypted with the public key
  of the receiver
• Public keys must be installed and obtained for
  the encryption from the certificate authority
  (CA)?

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SIPs External Security Mechanisms

• IPSec
• SSL/TLS

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IPSec

• Network layer security mechanism
• Provides a secure medium
• 4 security features
• Encryption
• Integrity validation
• Authentication
• Anti-replay

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SSL/TLS

• Transport layer security mechanism
• Hop-by-hop mechanism
• 3-way handshaking mechanism

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SSL/TLS 3 way handshaking

• The client sends out the ClientHello message with
  a list of cipher suites, compression methods, and
  the highest protocol version it supports.
• The server responses back with a ServerHello
  which contains its choices of cipher suite,
  compression methods, and protocol version.
• After the different connection parameters are
  known, the client and server exchange
  certificates and identity information. This is
  the authentication part of the TLS and if the
  server decides to request a certificate from the
  client, then this is known as mutual
  authentication.
• The client and server then negotiate a common
  secret key called the master secret which is
  usually derived from the Diffie-Hellman
  algorithm.

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Conclusion

• SIP is an easy to use and simple protocol for
  VoIP
• Limit internal security mechanisms
• Increase external security mechanisms
• Provide for a much easier implementation without
  too much concern for context

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Thank You!QA