breakpilot-pwa/backend/middleware/pii_redactor.py

"""
PII Redactor

Redacts Personally Identifiable Information (PII) from logs and responses.
Essential for DSGVO/GDPR compliance in BreakPilot.

Redacted data types:
- Email addresses
- IP addresses
- German phone numbers
- Names (when identified)
- Student IDs
- Credit card numbers
- IBAN numbers

Usage:
    from middleware import PIIRedactor, redact_pii

    # Use in logging
    logger.info(redact_pii(f"User {email} logged in from {ip}"))

    # Configure redactor
    redactor = PIIRedactor(patterns=["email", "ip", "phone"])
    safe_message = redactor.redact(sensitive_message)
"""

import re
from dataclasses import dataclass, field
from typing import Dict, List, Optional, Pattern, Set


@dataclass
class PIIPattern:
    """Definition of a PII pattern."""
    name: str
    pattern: Pattern
    replacement: str


# Pre-compiled regex patterns for common PII
PII_PATTERNS: Dict[str, PIIPattern] = {
    "email": PIIPattern(
        name="email",
        pattern=re.compile(
            r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b',
            re.IGNORECASE
        ),
        replacement="[EMAIL_REDACTED]",
    ),
    "ip_v4": PIIPattern(
        name="ip_v4",
        pattern=re.compile(
            r'\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b'
        ),
        replacement="[IP_REDACTED]",
    ),
    "ip_v6": PIIPattern(
        name="ip_v6",
        pattern=re.compile(
            r'\b(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}\b'
        ),
        replacement="[IP_REDACTED]",
    ),
    "phone_de": PIIPattern(
        name="phone_de",
        pattern=re.compile(
            r'(?<!\w)(?:\+49|0049|0)[\s.-]?(?:\d{2,4})[\s.-]?(?:\d{3,4})[\s.-]?(?:\d{3,4})(?!\d)'
        ),
        replacement="[PHONE_REDACTED]",
    ),
    "phone_intl": PIIPattern(
        name="phone_intl",
        pattern=re.compile(
            r'(?<!\w)\+?(?:\d[\s.-]?){10,15}(?!\d)'
        ),
        replacement="[PHONE_REDACTED]",
    ),
    "credit_card": PIIPattern(
        name="credit_card",
        pattern=re.compile(
            r'\b(?:\d{4}[\s.-]?){3}\d{4}\b'
        ),
        replacement="[CC_REDACTED]",
    ),
    "iban": PIIPattern(
        name="iban",
        pattern=re.compile(
            r'\b[A-Z]{2}\d{2}[\s]?(?:\d{4}[\s]?){3,5}\d{1,4}\b',
            re.IGNORECASE
        ),
        replacement="[IBAN_REDACTED]",
    ),
    "student_id": PIIPattern(
        name="student_id",
        pattern=re.compile(
            r'\b(?:student|schueler|schüler)[-_]?(?:id|nr)?[:\s]?\d{4,10}\b',
            re.IGNORECASE
        ),
        replacement="[STUDENT_ID_REDACTED]",
    ),
    "uuid": PIIPattern(
        name="uuid",
        pattern=re.compile(
            r'\b[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\b',
            re.IGNORECASE
        ),
        replacement="[UUID_REDACTED]",
    ),
    # German names are harder to detect, but we can catch common patterns
    "name_prefix": PIIPattern(
        name="name_prefix",
        pattern=re.compile(
            r'\b(?:Herr|Frau|Hr\.|Fr\.)\s+[A-ZÄÖÜ][a-zäöüß]+(?:\s+[A-ZÄÖÜ][a-zäöüß]+)?\b'
        ),
        replacement="[NAME_REDACTED]",
    ),
}

# Default patterns to enable
DEFAULT_PATTERNS = ["email", "ip_v4", "ip_v6", "phone_de"]


class PIIRedactor:
    """
    Redacts PII from strings.

    Attributes:
        patterns: List of pattern names to use (e.g., ["email", "ip_v4"])
        custom_patterns: Additional custom patterns
    """

    def __init__(
        self,
        patterns: Optional[List[str]] = None,
        custom_patterns: Optional[List[PIIPattern]] = None,
        preserve_format: bool = False,
    ):
        """
        Initialize the PII redactor.

        Args:
            patterns: List of pattern names to enable (default: email, ip_v4, ip_v6, phone_de)
            custom_patterns: Additional custom PIIPattern objects
            preserve_format: If True, preserve the length of redacted content
        """
        self.patterns = patterns or DEFAULT_PATTERNS
        self.custom_patterns = custom_patterns or []
        self.preserve_format = preserve_format

        # Build active patterns list
        self._active_patterns: List[PIIPattern] = []
        for pattern_name in self.patterns:
            if pattern_name in PII_PATTERNS:
                self._active_patterns.append(PII_PATTERNS[pattern_name])

        # Add custom patterns
        self._active_patterns.extend(self.custom_patterns)

    def redact(self, text: str) -> str:
        """
        Redact PII from the given text.

        Args:
            text: The text to redact PII from

        Returns:
            Text with PII replaced by redaction markers
        """
        if not text:
            return text

        result = text
        for pattern in self._active_patterns:
            if self.preserve_format:
                # Replace with same-length placeholder
                def replace_preserve(match):
                    length = len(match.group())
                    return "*" * length
                result = pattern.pattern.sub(replace_preserve, result)
            else:
                result = pattern.pattern.sub(pattern.replacement, result)

        return result

    def contains_pii(self, text: str) -> bool:
        """
        Check if text contains any PII.

        Args:
            text: The text to check

        Returns:
            True if PII is detected
        """
        if not text:
            return False

        for pattern in self._active_patterns:
            if pattern.pattern.search(text):
                return True
        return False

    def find_pii(self, text: str) -> List[Dict[str, str]]:
        """
        Find all PII in text with their types.

        Args:
            text: The text to search

        Returns:
            List of dicts with 'type' and 'match' keys
        """
        if not text:
            return []

        findings = []
        for pattern in self._active_patterns:
            for match in pattern.pattern.finditer(text):
                findings.append({
                    "type": pattern.name,
                    "match": match.group(),
                    "start": match.start(),
                    "end": match.end(),
                })

        return findings


# Module-level default redactor instance
_default_redactor: Optional[PIIRedactor] = None


def get_default_redactor() -> PIIRedactor:
    """Get or create the default redactor instance."""
    global _default_redactor
    if _default_redactor is None:
        _default_redactor = PIIRedactor()
    return _default_redactor


def redact_pii(text: str) -> str:
    """
    Convenience function to redact PII using the default redactor.

    Args:
        text: Text to redact

    Returns:
        Redacted text

    Example:
        logger.info(redact_pii(f"User {email} logged in"))
    """
    return get_default_redactor().redact(text)


class PIIRedactingLogFilter:
    """
    Logging filter that automatically redacts PII from log messages.

    Usage:
        import logging

        handler = logging.StreamHandler()
        handler.addFilter(PIIRedactingLogFilter())
        logger = logging.getLogger()
        logger.addHandler(handler)
    """

    def __init__(self, redactor: Optional[PIIRedactor] = None):
        self.redactor = redactor or get_default_redactor()

    def filter(self, record):
        # Redact the message
        if record.msg:
            record.msg = self.redactor.redact(str(record.msg))

        # Redact args if present
        if record.args:
            if isinstance(record.args, dict):
                record.args = {
                    k: self.redactor.redact(str(v)) if isinstance(v, str) else v
                    for k, v in record.args.items()
                }
            elif isinstance(record.args, tuple):
                record.args = tuple(
                    self.redactor.redact(str(v)) if isinstance(v, str) else v
                    for v in record.args
                )

        return True


def create_safe_dict(data: dict, redactor: Optional[PIIRedactor] = None) -> dict:
    """
    Create a copy of a dictionary with PII redacted.

    Args:
        data: Dictionary to redact
        redactor: Optional custom redactor

    Returns:
        New dictionary with redacted values
    """
    r = redactor or get_default_redactor()

    def redact_value(value):
        if isinstance(value, str):
            return r.redact(value)
        elif isinstance(value, dict):
            return create_safe_dict(value, r)
        elif isinstance(value, list):
            return [redact_value(v) for v in value]
        return value

    return {k: redact_value(v) for k, v in data.items()}