MITM Proxy Server

This is a Man-in-the-Middle (MITM) proxy server written in Go, similar to the functionality of Charles proxy tool.

Features

1. Transparent MITM Proxy: Completely transparent HTTP/HTTPS proxy that doesn't interfere with any traffic
2. Hardcoded Certificates: P12 certificate and CA certificate directly embedded in the program, no external files needed
3. HTTPS Decryption: Attempts to decrypt HTTPS traffic for inspection, falls back to transparent mode if decryption fails
4. Dual Traffic Dump: Save both encrypted and decrypted data to different files for analysis
5. Complete Data Output: Console displays complete request/response data without truncation
6. Domain Filtering: Print specific traffic to stdout based on the list of domains of interest in TOML configuration file
7. System Proxy: Automatically set Windows system proxy, restore when program ends
8. CA Certificate Installation: Automatically import hardcoded CA certificate to Windows trusted root certificate authorities
9. Redirect Transparency: All HTTP redirects (301/302/etc.) are passed through exactly as-is without modification
10. Built-in Testing: Use -test flag to verify proxy functionality and connectivity

Prerequisites

1. Go 1.21+: Ensure Go language environment is installed
2. OpenSSL: For processing P12 certificate files (optional, will use basic configuration if not available)
3. Administrator Privileges: Setting system proxy and installing certificates requires administrator privileges

Installation and Usage

1. Clone or Download Project

git clone <repository-url>
cd mitm

2. Install Dependencies

go mod tidy

3. Prepare Certificate Files

Ensure you have the following files:

• cert.p12: P12 certificate file containing CA and private key
• CA.crt: CA certificate file

4. Configuration File

Edit the config.toml file:

# Domains of interest configuration
domains_of_interest = [
    "example.com",
    "httpbin.org", 
    "api.github.com",
    "www.google.com"
]

[proxy]
port = 8080
cert_file = "cert.p12"
cert_password = "your_password_here"  # Change to your certificate password
ca_cert_file = "CA.crt"

[dump]
output_dir = "traffic_dumps"

5. Run Program

Important: Need to run as administrator:

# Open PowerShell or Command Prompt as administrator
go run .

Or compile and run:

go build -o mitm.exe
# Run as administrator
./mitm.exe

Usage Instructions

1. Start Program: The program will automatically:

   • Install CA certificate to system trusted root certificate store
   • Set system proxy to 127.0.0.1:8080
   • Start proxy server

2. Traffic Interception:

   • All HTTP/HTTPS traffic will be intercepted transparently
   • No modification of requests, responses, or redirects
   • Each request will be saved to traffic_dumps directory
   • Traffic from domains of interest will be printed to console
   • HTTPS traffic is decrypted when possible, falls back to encrypted passthrough

3. Testing Connectivity:

   # Test proxy functionality
   go run . -test
   

4. Stop Program:

   • Press Ctrl+C to stop program
   • Program will automatically restore original system proxy settings

File Structure

mitm/
├── main.go           # Main program file
├── cert_utils.go     # Certificate processing tools
├── config.toml       # Configuration file
├── go.mod           # Go module file
├── cert.p12         # P12 certificate file (you need to provide)
├── CA.crt           # CA certificate file (you need to provide)
└── traffic_dumps/   # Traffic dump directory (auto-created)

Output File Format

HTTP Traffic Files

Filename format: YYYYMMDD_HHMMSS_domain.txt

Content includes:

• Request information (method, URL, headers, body)
• Response information (status code, headers, body)

HTTPS Traffic Files

Filename format: YYYYMMDD_HHMMSS_domain_direction.bin

Contains encrypted binary data.

Important Notes

1. Administrator Privileges: Program needs administrator privileges to modify system proxy settings and install certificates
2. Certificate Security: Please ensure the security of P12 certificate files, do not hardcode passwords in production environments
3. Network Security: This tool is only for legal network debugging and testing purposes
4. System Compatibility: Currently only supports Windows systems

Troubleshooting

1. Certificate Loading Failed:

   • Check P12 file path and password
   • Ensure OpenSSL is installed (optional)

2. Proxy Setting Failed:

   • Ensure running with administrator privileges
   • Check if port 8080 is occupied

3. CA Certificate Installation Failed:

   • Ensure CA.crt file exists and format is correct
   • Check administrator privileges

Development and Customization

You can modify the following parts as needed:

• Add more domains of interest in config.toml
• Modify proxy port
• Customize traffic dump format
• Add more traffic analysis features

License

Please see the LICENSE file for license information.