stegasoo/frontends/web/app.py

#!/usr/bin/env python3
"""
Stegasoo Web Frontend

Flask-based web UI for steganography operations.
Supports both text messages and file embedding.
"""

import io
import sys
import time
import secrets
import mimetypes
from pathlib import Path
from datetime import datetime

from flask import (
    Flask, render_template, request, send_file,
    jsonify, flash, redirect, url_for
)

# Add parent to path for development
sys.path.insert(0, str(Path(__file__).parent.parent.parent / 'src'))

import stegasoo
from stegasoo import (
    encode, decode, generate_credentials,
    export_rsa_key_pem, load_rsa_key,
    validate_pin, validate_message, validate_image,
    validate_rsa_key, validate_security_factors,
    validate_file_payload,
    get_today_day, generate_filename,
    DAY_NAMES, __version__,
    StegasooError, DecryptionError, CapacityError,
    has_argon2,
    FilePayload,
    MAX_FILE_PAYLOAD_SIZE,
)
from stegasoo.constants import (
    MAX_MESSAGE_SIZE, MIN_PIN_LENGTH, MAX_PIN_LENGTH,
    VALID_RSA_SIZES, MAX_FILE_SIZE,
)


# ============================================================================
# FLASK APP CONFIGURATION
# ============================================================================

app = Flask(__name__)
app.secret_key = secrets.token_hex(32)
app.config['MAX_CONTENT_LENGTH'] = MAX_FILE_SIZE  # 10MB max upload

# Temporary file storage for sharing (file_id -> {data, timestamp, filename})
TEMP_FILES: dict[str, dict] = {}
TEMP_FILE_EXPIRY = 300  # 5 minutes


def cleanup_temp_files():
    """Remove expired temporary files."""
    now = time.time()
    expired = [fid for fid, info in TEMP_FILES.items() if now - info['timestamp'] > TEMP_FILE_EXPIRY]
    for fid in expired:
        TEMP_FILES.pop(fid, None)


def allowed_image(filename: str) -> bool:
    """Check if file has allowed image extension."""
    if not filename or '.' not in filename:
        return False
    ext = filename.rsplit('.', 1)[1].lower()
    return ext in {'png', 'jpg', 'jpeg', 'bmp', 'gif'}


def format_size(size_bytes: int) -> str:
    """Format file size for display."""
    if size_bytes < 1024:
        return f"{size_bytes} B"
    elif size_bytes < 1024 * 1024:
        return f"{size_bytes / 1024:.1f} KB"
    else:
        return f"{size_bytes / (1024 * 1024):.1f} MB"


# ============================================================================
# ROUTES
# ============================================================================

@app.route('/')
def index():
    return render_template('index.html')


@app.route('/generate', methods=['GET', 'POST'])
def generate():
    if request.method == 'POST':
        words_per_phrase = int(request.form.get('words_per_phrase', 3))
        use_pin = request.form.get('use_pin') == 'on'
        use_rsa = request.form.get('use_rsa') == 'on'
        
        if not use_pin and not use_rsa:
            flash('You must select at least one security factor (PIN or RSA Key)', 'error')
            return render_template('generate.html', generated=False, has_ml=False)
        
        pin_length = int(request.form.get('pin_length', 6))
        rsa_bits = int(request.form.get('rsa_bits', 2048))
        
        # Clamp values
        words_per_phrase = max(3, min(12, words_per_phrase))
        pin_length = max(MIN_PIN_LENGTH, min(MAX_PIN_LENGTH, pin_length))
        if rsa_bits not in VALID_RSA_SIZES:
            rsa_bits = 2048
        
        try:
            creds = generate_credentials(
                use_pin=use_pin,
                use_rsa=use_rsa,
                pin_length=pin_length,
                rsa_bits=rsa_bits,
                words_per_phrase=words_per_phrase
            )
            
            return render_template('generate.html',
                phrases=creds.phrases,
                pin=creds.pin,
                days=DAY_NAMES,
                generated=True,
                words_per_phrase=words_per_phrase,
                pin_length=pin_length if use_pin else None,
                use_pin=use_pin,
                use_rsa=use_rsa,
                rsa_bits=rsa_bits,
                rsa_key_pem=creds.rsa_key_pem,
                phrase_entropy=creds.phrase_entropy,
                pin_entropy=creds.pin_entropy,
                rsa_entropy=creds.rsa_entropy,
                total_entropy=creds.total_entropy,
                has_ml=False
            )
        except Exception as e:
            flash(f'Error generating credentials: {e}', 'error')
            return render_template('generate.html', generated=False, has_ml=False)
    
    return render_template('generate.html', generated=False, has_ml=False)


@app.route('/generate/download-key', methods=['POST'])
def download_key():
    """Download RSA key as password-protected PEM file."""
    key_pem = request.form.get('key_pem', '')
    password = request.form.get('key_password', '')
    
    if not key_pem:
        flash('No key to download', 'error')
        return redirect(url_for('generate'))
    
    if not password or len(password) < 8:
        flash('Password must be at least 8 characters', 'error')
        return redirect(url_for('generate'))
    
    try:
        private_key = load_rsa_key(key_pem.encode())
        encrypted_pem = export_rsa_key_pem(private_key, password=password)
        
        key_id = secrets.token_hex(4)
        filename = f'stegasoo_key_{private_key.key_size}_{key_id}.pem'
        
        return send_file(
            io.BytesIO(encrypted_pem),
            mimetype='application/x-pem-file',
            as_attachment=True,
            download_name=filename
        )
    except Exception as e:
        flash(f'Error creating key file: {e}', 'error')
        return redirect(url_for('generate'))


@app.route('/encode', methods=['GET', 'POST'])
def encode_page():
    day_of_week = get_today_day()
    max_payload_kb = MAX_FILE_PAYLOAD_SIZE // 1024
    
    if request.method == 'POST':
        try:
            # Get files
            ref_photo = request.files.get('reference_photo')
            carrier = request.files.get('carrier')
            rsa_key_file = request.files.get('rsa_key')
            payload_file = request.files.get('payload_file')
            
            if not ref_photo or not carrier:
                flash('Both reference photo and carrier image are required', 'error')
                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            if not allowed_image(ref_photo.filename) or not allowed_image(carrier.filename):
                flash('Invalid file type. Use PNG, JPG, or BMP', 'error')
                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Get form data
            message = request.form.get('message', '')
            day_phrase = request.form.get('day_phrase', '')
            pin = request.form.get('pin', '').strip()
            rsa_password = request.form.get('rsa_password', '')
            payload_type = request.form.get('payload_type', 'text')
            
            # Determine payload
            if payload_type == 'file' and payload_file and payload_file.filename:
                # File payload
                file_data = payload_file.read()
                
                result = validate_file_payload(file_data, payload_file.filename)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
                
                mime_type, _ = mimetypes.guess_type(payload_file.filename)
                payload = FilePayload(
                    data=file_data,
                    filename=payload_file.filename,
                    mime_type=mime_type
                )
            else:
                # Text message
                result = validate_message(message)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
                payload = message
            
            if not day_phrase:
                flash('Day phrase is required', 'error')
                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Read files
            ref_data = ref_photo.read()
            carrier_data = carrier.read()
            rsa_key_data = rsa_key_file.read() if rsa_key_file and rsa_key_file.filename else None
            
            # Validate security factors
            result = validate_security_factors(pin, rsa_key_data)
            if not result.is_valid:
                flash(result.error_message, 'error')
                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Validate PIN if provided
            if pin:
                result = validate_pin(pin)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Validate RSA key if provided
            if rsa_key_data:
                result = validate_rsa_key(rsa_key_data, rsa_password if rsa_password else None)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Validate carrier image
            result = validate_image(carrier_data, "Carrier image")
            if not result.is_valid:
                flash(result.error_message, 'error')
                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
            
            # Get date
            client_date = request.form.get('client_date', '').strip()
            if client_date and len(client_date) == 10 and client_date[4] == '-' and client_date[7] == '-':
                date_str = client_date
            else:
                date_str = datetime.now().strftime('%Y-%m-%d')
            
            # Encode
            encode_result = encode(
                message=payload,
                reference_photo=ref_data,
                carrier_image=carrier_data,
                day_phrase=day_phrase,
                pin=pin,
                rsa_key_data=rsa_key_data,
                rsa_password=rsa_password if rsa_password else None,
                date_str=date_str
            )
            
            # Store temporarily
            file_id = secrets.token_urlsafe(16)
            cleanup_temp_files()
            TEMP_FILES[file_id] = {
                'data': encode_result.stego_image,
                'filename': encode_result.filename,
                'timestamp': time.time()
            }
            
            return redirect(url_for('encode_result', file_id=file_id))
            
        except CapacityError as e:
            flash(str(e), 'error')
            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
        except StegasooError as e:
            flash(str(e), 'error')
            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
        except Exception as e:
            flash(f'Error: {e}', 'error')
            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
    
    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)


@app.route('/encode/result/<file_id>')
def encode_result(file_id):
    if file_id not in TEMP_FILES:
        flash('File expired or not found. Please encode again.', 'error')
        return redirect(url_for('encode_page'))
    
    file_info = TEMP_FILES[file_id]
    return render_template('encode_result.html',
        file_id=file_id,
        filename=file_info['filename']
    )


@app.route('/encode/download/<file_id>')
def encode_download(file_id):
    if file_id not in TEMP_FILES:
        flash('File expired or not found.', 'error')
        return redirect(url_for('encode_page'))
    
    file_info = TEMP_FILES[file_id]
    return send_file(
        io.BytesIO(file_info['data']),
        mimetype='image/png',
        as_attachment=True,
        download_name=file_info['filename']
    )


@app.route('/encode/file/<file_id>')
def encode_file_route(file_id):
    """Serve file for Web Share API."""
    if file_id not in TEMP_FILES:
        return "Not found", 404
    
    file_info = TEMP_FILES[file_id]
    return send_file(
        io.BytesIO(file_info['data']),
        mimetype='image/png',
        as_attachment=False,
        download_name=file_info['filename']
    )


@app.route('/encode/cleanup/<file_id>', methods=['POST'])
def encode_cleanup(file_id):
    """Manually cleanup a file after sharing."""
    TEMP_FILES.pop(file_id, None)
    return jsonify({'status': 'ok'})


@app.route('/decode', methods=['GET', 'POST'])
def decode_page():
    if request.method == 'POST':
        try:
            # Get files
            ref_photo = request.files.get('reference_photo')
            stego_image = request.files.get('stego_image')
            rsa_key_file = request.files.get('rsa_key')
            
            if not ref_photo or not stego_image:
                flash('Both reference photo and stego image are required', 'error')
                return render_template('decode.html')
            
            # Get form data
            day_phrase = request.form.get('day_phrase', '')
            pin = request.form.get('pin', '').strip()
            rsa_password = request.form.get('rsa_password', '')
            
            if not day_phrase:
                flash('Day phrase is required', 'error')
                return render_template('decode.html')
            
            # Read files
            ref_data = ref_photo.read()
            stego_data = stego_image.read()
            rsa_key_data = rsa_key_file.read() if rsa_key_file and rsa_key_file.filename else None
            
            # Validate security factors
            result = validate_security_factors(pin, rsa_key_data)
            if not result.is_valid:
                flash(result.error_message, 'error')
                return render_template('decode.html')
            
            # Validate PIN if provided
            if pin:
                result = validate_pin(pin)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('decode.html')
            
            # Validate RSA key if provided
            if rsa_key_data:
                result = validate_rsa_key(rsa_key_data, rsa_password if rsa_password else None)
                if not result.is_valid:
                    flash(result.error_message, 'error')
                    return render_template('decode.html')
            
            # Decode
            decode_result = decode(
                stego_image=stego_data,
                reference_photo=ref_data,
                day_phrase=day_phrase,
                pin=pin,
                rsa_key_data=rsa_key_data,
                rsa_password=rsa_password if rsa_password else None
            )
            
            if decode_result.is_file:
                # File content - store temporarily for download
                file_id = secrets.token_urlsafe(16)
                cleanup_temp_files()
                
                filename = decode_result.filename or 'decoded_file'
                TEMP_FILES[file_id] = {
                    'data': decode_result.file_data,
                    'filename': filename,
                    'mime_type': decode_result.mime_type,
                    'timestamp': time.time()
                }
                
                return render_template('decode.html',
                    decoded_file=True,
                    file_id=file_id,
                    filename=filename,
                    file_size=format_size(len(decode_result.file_data)),
                    mime_type=decode_result.mime_type
                )
            else:
                # Text content
                return render_template('decode.html', decoded_message=decode_result.message)
            
        except DecryptionError:
            flash('Decryption failed. Check your phrase, PIN, RSA key, and reference photo.', 'error')
            return render_template('decode.html')
        except StegasooError as e:
            flash(str(e), 'error')
            return render_template('decode.html')
        except Exception as e:
            flash(f'Error: {e}', 'error')
            return render_template('decode.html')
    
    return render_template('decode.html')


@app.route('/decode/download/<file_id>')
def decode_download(file_id):
    """Download decoded file."""
    if file_id not in TEMP_FILES:
        flash('File expired or not found.', 'error')
        return redirect(url_for('decode_page'))
    
    file_info = TEMP_FILES[file_id]
    mime_type = file_info.get('mime_type', 'application/octet-stream')
    
    return send_file(
        io.BytesIO(file_info['data']),
        mimetype=mime_type,
        as_attachment=True,
        download_name=file_info['filename']
    )


@app.route('/about')
def about():
    return render_template('about.html', 
        has_argon2=has_argon2(),
        max_payload_kb=MAX_FILE_PAYLOAD_SIZE // 1024
    )


# ============================================================================
# MAIN
# ============================================================================

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000, debug=False)