MITMPROXY_SETUP.md

MITM Proxy Setup (Working Solution)

This is the actually working solution for proxying Antigravity's API calls.

Why This Instead of Node.js?

The Node.js proxy cannot inspect HTTPS content without implementing full MITM with certificate generation.

mitmproxy is the industry-standard tool that handles all of this automatically.

Installation (5 minutes)

1. Install mitmproxy

brew install mitmproxy

2. Install Python dependencies (for the addon)

# Install python-dotenv for reading .env file
pip3 install python-dotenv

3. Verify Installation

mitmproxy --version

Should output something like: Mitmproxy: 10.x.x

Setup (10 minutes)

1. Install SSL Certificate

This is the critical step that allows mitmproxy to intercept HTTPS traffic.

# Start mitmproxy once to generate certificate
mitmproxy

Press q to quit.

The certificate is now at: ~/.mitmproxy/mitmproxy-ca-cert.pem

2. Add Certificate to macOS Keychain

# Open certificate in Keychain Access
open ~/.mitmproxy/mitmproxy-ca-cert.pem

In Keychain Access:

1. Find "mitmproxy" certificate
2. Double-click it
3. Expand "Trust" section
4. Set "When using this certificate" to "Always Trust"
5. Close (you'll be prompted for password)

Visual Guide:

• Certificate should show "This certificate is marked as trusted for all users"
• Green checkmark next to "mitmproxy"

Usage

Start the Proxy

cd ~/dev/personal/antigravity-proxy

# Use the Python addon
mitmproxy -s mitmproxy-addon.py --listen-port 8080

You should see:

🚀 Antigravity Proxy - MITM Interceptor
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
🔑 Using API Key: AIzaSyABC123***
🎯 Target: generativelanguage.googleapis.com
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Proxy server listening at http://*:8080

Launch Antigravity

In a new terminal:

cd ~/dev/personal/antigravity-proxy

# Use the shell script
./scripts/launch-antigravity.sh

Or manually:

HTTP_PROXY=http://localhost:8080 \
HTTPS_PROXY=http://localhost:8080 \
/Applications/Antigravity.app/Contents/MacOS/Antigravity

Verify It's Working

When you use Antigravity's AI features, you should see in the mitmproxy terminal:

📥 INCOMING REQUEST #1
   Method: POST
   URL: https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:generateContent
   🔄 Replaced key in header
      Old: AIzaSyABC123***
      New: AIzaSyDEF456***

✅ RESPONSE
   Status: 200

📊 Stats: 1 requests, 1 keys replaced
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Configuration

The addon reads from your .env file:

# Make sure you have this set
GEMINI_API_KEY=your_actual_api_key_here

Troubleshooting

Certificate Not Trusted

Symptom: Antigravity shows SSL errors

Solution:

1. Open Keychain Access
2. Search for "mitmproxy"
3. Double-click certificate
4. Set Trust to "Always Trust"
5. Restart Antigravity

No Requests Appearing

Symptom: mitmproxy shows no traffic

Solutions:

1. Verify proxy settings:

   # In the terminal where you launched Antigravity
   echo $HTTP_PROXY
   echo $HTTPS_PROXY

   Should both output: http://localhost:8080

2. Check if mitmproxy is running:

   lsof -ti:8080

   Should return a process ID

3. Test with curl:

   HTTP_PROXY=http://localhost:8080 \
   HTTPS_PROXY=http://localhost:8080 \
   curl https://generativelanguage.googleapis.com/v1beta/models

   Should appear in mitmproxy logs

mitmproxy Command Not Found

Solution:

brew install mitmproxy

python-dotenv Not Found

Solution:

pip3 install python-dotenv

Advanced Usage

Interactive Mode

mitmproxy has an interactive TUI:

mitmproxy -s mitmproxy-addon.py

Press:

• q - Quit
• ? - Help
• Arrow keys - Navigate requests
• Enter - View request/response details

Web Interface

mitm has a web interface:

mitmweb -s mitmproxy-addon.py --listen-port 8080

Then open: http://localhost:8081

Headless Mode

For background operation:

mitmdump -s mitmproxy-addon.py --listen-port 8080

Save Traffic

Record all traffic to a file:

mitmdump -s mitmproxy-addon.py --listen-port 8080 -w traffic.mitm

Replay later:

mitmproxy -r traffic.mitm

Comparison: Node.js vs mitmproxy

Feature	Node.js Proxy	mitmproxy
HTTPS Inspection	❌ Doesn't work	✅ Works perfectly
Certificate Setup	❌ Complex	✅ Automatic
API Key Replacement	❌ Can't access content	✅ Full access
Logging	✅ Good	✅ Excellent
Setup Time	5 minutes	10 minutes
Actually Works	❌ No	✅ Yes

Automation

Create App Launcher

Add to ~/.zshrc or ~/.bashrc:

# Antigravity with proxy
antigravity-proxy() {
    # Start mitmproxy in background
    mitmdump -s ~/dev/personal/antigravity-proxy/mitmproxy-addon.py --listen-port 8080 > /dev/null 2>&1 &
    MITM_PID=$!
    
    # Wait for proxy to start
    sleep 2
    
    # Launch Antigravity
    HTTP_PROXY=http://localhost:8080 \
    HTTPS_PROXY=http://localhost:8080 \
    /Applications/Antigravity.app/Contents/MacOS/Antigravity
    
    # Kill mitmproxy when Antigravity exits
    kill $MITM_PID 2>/dev/null
}

Then just run:

antigravity-proxy

Background Service (pm2)

Run mitmproxy as a service:

# Install pm2
npm install -g pm2

# Create start script
cat > ~/dev/personal/antigravity-proxy/start-mitm.sh << 'EOF'
#!/bin/bash
cd ~/dev/personal/antigravity-proxy
mitmdump -s mitmproxy-addon.py --listen-port 8080
EOF

chmod +x ~/dev/personal/antigravity-proxy/start-mitm.sh

# Start with pm2
pm2 start ~/dev/personal/antigravity-proxy/start-mitm.sh --name antigravity-proxy

# Make it start on boot
pm2 save
pm2 startup

Then always launch Antigravity with proxy settings:

alias antigravity='HTTP_PROXY=http://localhost:8080 HTTPS_PROXY=http://localhost:8080 /Applications/Antigravity.app/Contents/MacOS/Antigravity'

Security Notes

• ⚠️ The mitmproxy certificate allows intercepting ALL HTTPS traffic
• Only use on your development machine
• Don't export the private key (~/.mitmproxy/mitmproxy-ca.pem)
• Revoke trust when done with development

Summary

This is the working solution. The Node.js proxy was a good learning exercise but doesn't actually work for HTTPS content inspection.

mitmproxy:

• ✅ Industry standard for API interception
• ✅ Handles certificate generation automatically
• ✅ Can inspect and modify HTTPS traffic
• ✅ Well-documented and maintained
• ✅ Actually works with Antigravity

Total setup time: ~15 minutes