icalendar-anonymizer

Strip personal data from iCalendar files while preserving technical properties for bug reproduction.

Calendar bugs are hard to reproduce without actual calendar data, but people can't share their calendars publicly due to privacy concerns. This tool uses hash-based anonymization to remove sensitive information (names, emails, locations, descriptions) while keeping all date/time, recurrence, and timezone data intact.

Installation

# Library only
pip install icalendar-anonymizer

# With CLI tool
pip install icalendar-anonymizer[cli]

# With web service
pip install icalendar-anonymizer[web]

# Everything
pip install icalendar-anonymizer[all]

Docker:

docker-compose up -d

From source:

git clone https://github.com/mergecal/icalendar-anonymizer.git
cd icalendar-anonymizer
pip install -e ".[dev]"

Usage

Python API

from icalendar import Calendar
from icalendar_anonymizer import anonymize

# Load calendar
with open('calendar.ics', 'rb') as f:
    cal = Calendar.from_ical(f.read())

# Anonymize
anonymized_cal = anonymize(cal)

# Save
with open('anonymized.ics', 'wb') as f:
    f.write(anonymized_cal.to_ical())

Command Line

# Basic usage
icalendar-anonymize input.ics -o output.ics

# Shorter alias
ican input.ics -o output.ics

# Unix-style piping
cat calendar.ics | icalendar-anonymize > anonymized.ics

# Stdout by default
icalendar-anonymize calendar.ics

Options:

• -i, --input FILE - Input file (default: stdin)
• -o, --output FILE - Output file (default: stdout)
• -v, --verbose - Show processing details
• --version - Print version

Web Service

# POST with ICS content
curl -X POST https://anonymizer.example.com/anonymize \
     -H "Content-Type: application/json" \
     -d '{"ics": "BEGIN:VCALENDAR..."}'

# Upload ICS file
curl -X POST https://anonymizer.example.com/upload \
     -F "[email protected]"

# Fetch and anonymize URL
curl "https://anonymizer.example.com/fetch?url=https://example.com/cal.ics"

FastAPI provides interactive docs at /docs for testing.

Self-hosting:

docker-compose up -d

Runs on port 8000 by default. Includes SSRF protection (blocks localhost and private IPs), 10-second timeout, and 10MB max file size.

How It Works

Hash-based anonymization - Same input always produces the same output, preserving patterns for bug analysis.

Structure preservation - A 10-word summary stays 10 words. Emails still look like emails.

What gets anonymized:

• SUMMARY, DESCRIPTION, LOCATION
• ATTENDEE, ORGANIZER (including CN fields)
• COMMENT, CONTACT
• Unknown/X- properties (safe by default)

What stays intact:

• DTSTART, DTEND, DUE, DURATION, DTSTAMP
• RRULE, RDATE, EXDATE
• VTIMEZONE, TZID, TZOFFSETFROM, TZOFFSETTO
• UID (hashed but unique)
• SEQUENCE, STATUS, TRANSP, CLASS, PRIORITY
• CATEGORIES

Contributing

See CONTRIBUTING.md for development workflow, commit format, and testing requirements.

License

AGPL-3.0-or-later. See LICENSE.