44 lines
1.3 KiB
Python
44 lines
1.3 KiB
Python
"""CSRF protection (session-scoped token, no external dependency)."""
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import hmac
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import logging
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import secrets
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from flask import abort, request, session
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logger = logging.getLogger(__name__)
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def get_csrf_token():
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"""Return the per-session CSRF token, generating one on first use."""
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token = session.get("_csrf_token")
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if not token:
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token = secrets.token_hex(32)
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session["_csrf_token"] = token
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return token
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def validate_csrf():
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"""Abort 403 if the CSRF token doesn't match the session token.
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Token may arrive in the form field "csrf_token" (POST), the JSON body
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field "csrf_token" (fetch JSON POST), or as the query parameter
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csrf_token (GET SSE endpoints).
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"""
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expected = session.get("_csrf_token")
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provided = request.form.get("csrf_token", "") or request.args.get("csrf_token", "")
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if not provided and request.is_json:
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body = request.get_json(silent=True) or {}
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provided = body.get("csrf_token", "")
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if not expected or not provided or not hmac.compare_digest(expected, provided):
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logger.warning(
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"CSRF validation failed for %s from %s",
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request.path,
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request.remote_addr,
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)
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abort(403)
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def init_app(app):
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"""Expose csrf_token() to Jinja templates as a global."""
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app.jinja_env.globals["csrf_token"] = get_csrf_token |