Class: Otto::Privacy::UserAgentPrivacy

Inherits:
Object
  • Object
show all
Defined in:
lib/otto/privacy/user_agent_privacy.rb

Overview

Note:

Idempotent: re-anonymizing already-anonymized output is a no-op, so a UA reduced at the edge and one reduced again downstream agree.

User-Agent anonymization utilities.

Reduces a User-Agent string to a lower-entropy form by stripping build identifiers and version numbers and truncating, so it can be logged or stored for analytics without a high-entropy fingerprint while preserving browser/OS family information. This is the User-Agent analogue of IPPrivacy for IP addresses, exposed as a public surface so downstream consumers can reduce a UA outside of the full RedactedFingerprint / middleware flow without re-implementing (and drifting from) these regexes.

Examples:

UserAgentPrivacy.anonymize(
  'Mozilla/5.0 (Windows NT 10.0) Chrome/119.0.0.0 Safari/537.36'
)
# => 'Mozilla/*.* (Windows NT *.*) Chrome/*.*.*.* Safari/*.*'

Constant Summary collapse

DEFAULT_MAX_LENGTH =

Default cap on the returned string, guarding against a DoS via a huge User-Agent header. Matches the length RedactedFingerprint has always applied.

500

Class Method Summary collapse

Class Method Details

.anonymize(ua, max_length: DEFAULT_MAX_LENGTH) ⇒ String?

Anonymize a User-Agent string.

Removes build identifiers (e.g. +Build/MRA58N+) and version numbers (+...+, +..+, +.*+; dot- or underscore-separated), then truncates to +max_length+. Browser/OS family text is preserved – the point is a partial, not a full redaction.

Build identifiers are stripped BEFORE versions: if versions went first, a token like +Build/MPJ24.139-64+ would become +Build/MPJ.-64+ and the build regex (which matches only +[\w.-]+) would no longer catch it.

Parameters:

  • ua (String, nil) —

    the raw User-Agent string.

  • max_length (Integer) (defaults to: DEFAULT_MAX_LENGTH) —

    maximum length of the returned string.

Returns:

  • (String, nil) —

    the anonymized UA, or nil for nil/empty input.



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# File 'lib/otto/privacy/user_agent_privacy.rb', line 45

def self.anonymize(ua, max_length: DEFAULT_MAX_LENGTH)
  return nil if ua.nil? || ua.empty?

  # Remove build identifiers (e.g., Build/MRA58N, Build/MPJ24.139-64).
  # Must run BEFORE version stripping (see method note).
  anonymized = ua.gsub(%r{Build/[\w.-]+}, 'Build/*')

  # Remove version patterns (*.*.*.*, *.*.*, *.*), longest first.
  # Support both dot and underscore separators (e.g. 10.15.7 and 10_15_7).
  anonymized = anonymized
               .gsub(/\d+[._]\d+[._]\d+[._]\d+/, '*.*.*.*')
               .gsub(/\d+[._]\d+[._]\d+/, '*.*.*')
               .gsub(/\d+[._]\d+/, '*.*')

  # Truncate if too long (prevent DoS via huge UA strings).
  anonymized.length > max_length ? anonymized[0...max_length] : anonymized
end