55 lines
2 KiB
Python
55 lines
2 KiB
Python
#!/usr/bin/env python3
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import re
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import os
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from flask import Flask, abort, request, Response
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import filecrypt
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app = Flask(__name__)
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app.config.from_envvar('SECURE_DOWNLOAD_SETTINGS')
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BASE64_RE = re.compile('^[A-Za-z0-9+-_]+=*$')
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@app.route('/<file_id>/<token>/<filename>')
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def download(file_id, token, filename):
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if not BASE64_RE.match(file_id) or len(file_id) != filecrypt.FILE_ID_LENGTH:
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abort(400, 'Invalid file ID format')
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if not BASE64_RE.match(token) or len(token) != filecrypt.TOKEN_LENGTH:
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abort(400, 'Invalid token format')
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path = f'{app.config["SERVE_PATH"]}/{file_id}.enc'
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if not os.path.isfile(path):
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abort(403) # forbidden
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size = filecrypt.payload_size(path)
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range_header = re.match('^bytes=([0-9]+)-([0-9]*)$', request.headers.get('Range', ''))
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if not range_header:
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try:
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generator = filecrypt.decrypt_generator(path, filename, token)
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except ValueError: # MAC check failed
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abort(403) # forbidden
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response = Response(generator, mimetype='application/octet-stream')
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response.headers['Content-Length'] = size
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else:
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range_start, range_end = range_header.groups()
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range_start = int(range_start)
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range_end = int(range_end) if range_end else size-1
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if range_start < 0 or range_end >= size or range_start >= range_end:
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abort(416) # range not satisfiable
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try:
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generator = filecrypt.decrypt_generator(path, filename, token, seek=range_start, end=range_end)
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except ValueError: # MAC check failed
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abort(403) # forbidden
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response = Response(generator, status=206, mimetype='application/octet-stream')
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response.headers['Content-Range'] = f'bytes {range_start}-{range_end}/{size}'
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response.headers['Content-Length'] = range_end - range_start + 1
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print(f'{request.remote_addr}: {file_id} OK')
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response.headers['Accept-Ranges'] = 'bytes'
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response.headers['Content-Disposition'] = f'attachment {filename}'
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return response
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