Class: SingleUseRedactedString

Inherits:
RedactedString show all
Defined in:
lib/familia/features/transient_fields/single_use_redacted_string.rb

Overview

SingleUseRedactedString

A high-security variant of RedactedString that automatically clears its value after a single use via the expose method. Unlike RedactedString, this provides automatic cleanup and enforces single-use semantics.

⚠️ IMPORTANT: Inherits all security limitations from RedactedString regarding Ruby’s memory management and copy-on-write semantics.

⚠️ INPUT SECURITY: Like RedactedString, the constructor calls .dup on input, creating a copy, but the original input remains in memory. The caller is responsible for securely clearing the original.

Key Differences from RedactedString: - Automatically clears after expose() (no manual clear! needed) - Blocks direct value() access (prevents accidental multi-use) - Raises SecurityError on second expose() attempt

Use this for extremely sensitive values that should only be accessed once, such as: - One-time passwords (OTPs) - Temporary authentication tokens - Encryption keys that should be immediately discarded

Example: otp_input = params[:otp] # Original value in memory otp = SingleUseRedactedString.new(otp_input) params[:otp] = nil # Clear reference (not guaranteed) otp.expose do |code| verify_otp(code) # Use directly without copying end # Value is automatically cleared after block otp.cleared? #=> true

Instance Method Summary collapse

Methods inherited from RedactedString

#==, #clear!, #cleared?, finalizer_proc, #hash, #initialize, #inspect, #to_s

Constructor Details

This class inherits a constructor from RedactedString

Instance Method Details

#expose ⇒ Object

Override expose to automatically clear after use

This ensures the value can only be accessed once via expose, providing maximum security for single-use secrets.



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# File 'lib/familia/features/transient_fields/single_use_redacted_string.rb', line 45

def expose
  raise ArgumentError, 'Block required' unless block_given?
  raise SecurityError, 'Value already cleared' if cleared?

  yield @value
ensure
  clear! # Automatically clear after single use
end

#value ⇒ Object

Override value accessor to prevent direct access

For single-use secrets, we don’t want to allow direct value access to maintain the single-use guarantee.

Raises:

  • (SecurityError) 


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# File 'lib/familia/features/transient_fields/single_use_redacted_string.rb', line 59

def value
  raise SecurityError, 'Direct value access not allowed for single-use secrets. Use #expose with a block.'
end