Class: ConcealedString

Inherits:
Object
  • Object
show all
Defined in:
lib/familia/features/encrypted_fields/concealed_string.rb

Overview

ConcealedString

A secure wrapper for encrypted field values that prevents accidental plaintext leakage through serialization, logging, or debugging.

Unlike RedactedString (which wraps plaintext), ConcealedString wraps encrypted data and provides controlled decryption through the .reveal API.

Security Model:

  • Contains encrypted JSON data, never plaintext
  • Requires explicit .reveal { } for decryption and plaintext access
  • ALL serialization methods return '[CONCEALED]' to prevent leakage
  • Maintains encryption context for proper AAD handling
  • Thread-safe and supports concurrent access

Key Security Features:

  1. Universal Serialization Safety - ALL to_* methods protected
  2. Debugging Safety - inspect, logging, console output shows [CONCEALED]
  3. Exception Safety - never leaks plaintext in error messages
  4. Future-proof - any new serialization method automatically safe
  5. Memory Clearing - best-effort encrypted data clearing

Critical Design Principles:

  • Secure by default - no auto-decryption anywhere
  • Explicit decryption - .reveal required for plaintext access
  • Comprehensive protection - covers ALL serialization paths
  • Auditable access - easy to grep for .reveal usage

Example Usage: user = User.new user.secret_data = "sensitive info" # Encrypts and wraps user.secret_data # Returns ConcealedString user.secret_data.reveal { |plain| ... } # Explicit decryption user.to_h # Safe - contains [CONCEALED] user.to_json # Safe - contains [CONCEALED]

Constant Summary collapse

REDACTED = 
'[CONCEALED]'.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(encrypted_data, record, field_type) ⇒ ConcealedString

Create a concealed string wrapper

Parameters:

  • encrypted_data (String) —

    The encrypted JSON data

  • record (Familia::Horreum) —

    The record instance for context

  • field_type (EncryptedFieldType) —

    The field type for decryption



50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 50

def initialize(encrypted_data, record, field_type)
  @encrypted_data = encrypted_data.freeze
  @record = record
  @field_type = field_type
  @cleared = false

  # Parse and validate the encrypted data structure
  if @encrypted_data
    begin
      @encrypted_data_obj = Familia::Encryption::EncryptedData.from_json(@encrypted_data)
      # Validate that the encrypted data is decryptable (algorithm supported, etc.)
      @encrypted_data_obj.validate_decryptable!
    rescue Familia::EncryptionError => e
      raise Familia::EncryptionError, e.message
    rescue StandardError => e
      raise Familia::EncryptionError, "Invalid encrypted data: #{e.message}"
    end
  end

  ObjectSpace.define_finalizer(self, self.class.finalizer_proc(@encrypted_data))
end

Class Method Details

.finalizer_proc(encrypted_data) ⇒ Object

Finalizer to attempt memory cleanup



294
295
296
297
298
299
300
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 294

def self.finalizer_proc(encrypted_data)
  proc do
    # Best effort cleanup - Ruby doesn't guarantee memory security
    # Only clear if not frozen to avoid FrozenError
    encrypted_data.clear if encrypted_data.respond_to?(:clear) && !encrypted_data.frozen?
  end
end

Instance Method Details

#+(_other) ⇒ Object

String concatenation operations return concealed result



214
215
216
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 214

def +(_other)
  '[CONCEALED]'
end

#==(other) ⇒ Object Also known as: eql?

Returns true when it's literally the same object, otherwise false. This prevents timing attacks where an attacker could potentially infer information about the secret value through comparison timing



159
160
161
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 159

def ==(other)
  object_id.equal?(other.object_id) # same object
end

#as_json ⇒ Object

Prevent exposure in Rails serialization (as_json -> to_json)



289
290
291
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 289

def as_json(*)
  '[CONCEALED]'
end

#belongs_to_context?(expected_record, expected_field_name) ⇒ Boolean

Validate that this ConcealedString belongs to the given record context

This prevents cross-context attacks where encrypted data is moved between different records or field contexts. While moving ConcealedString objects manually is not a normal use case, this provides defense in depth.

Parameters:

  • expected_record (Familia::Horreum) —

    The record that should own this data

  • expected_field_name (Symbol) —

    The field name that should own this data

Returns:

  • (Boolean) —

    true if contexts match, false otherwise



109
110
111
112
113
114
115
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 109

def belongs_to_context?(expected_record, expected_field_name)
  return false if @record.nil? || @field_type.nil?

  @record.instance_of?(expected_record.class) &&
    @record.identifier == expected_record.identifier &&
    @field_type.instance_variable_get(:@name) == expected_field_name
end

#blank? ⇒ Boolean

Returns:

  • (Boolean) 


209
210
211
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 209

def blank?
  false # Never blank if encrypted data exists
end

#clear! ⇒ Object

Clear the encrypted data from memory

Safe to call multiple times. This provides best-effort memory clearing within Ruby's limitations.



134
135
136
137
138
139
140
141
142
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 134

def clear!
  return if @cleared

  @encrypted_data = nil
  @record = nil
  @field_type = nil
  @cleared = true
  freeze
end

#cleared? ⇒ Boolean

Check if the encrypted data has been cleared

Returns:

  • (Boolean) —

    true if cleared, false otherwise



148
149
150
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 148

def cleared?
  @cleared
end

#coerce(other) ⇒ Object

Handle coercion for concatenation like "string" + concealed



223
224
225
226
227
228
229
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 223

def coerce(other)
  if other.is_a?(String)
    ['[CONCEALED]', '[CONCEALED]']
  else
    [other, '[CONCEALED]']
  end
end

#concat(_other) ⇒ Object 



218
219
220
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 218

def concat(_other)
  '[CONCEALED]'
end

#context_description ⇒ String

Human-readable description of the record/field context this value was encrypted for. Used to make context-isolation errors actionable by showing the expected context alongside the accessing one.

Returns:

  • (String) —

    "Class:field:identifier", or a marker if context was cleared



123
124
125
126
127
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 123

def context_description
  return '(context cleared)' if @record.nil? || @field_type.nil?

  "#{@record.class.name}:#{@field_type.name}:#{@record.identifier}"
end

#deconstruct ⇒ Object

Pattern matching safety (Ruby 3.0+)



275
276
277
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 275

def deconstruct
  ['[CONCEALED]']
end

#deconstruct_keys ⇒ Object 



279
280
281
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 279

def deconstruct_keys(*)
  { concealed: true }
end

#downcase ⇒ Object 



193
194
195
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 193

def downcase
  '[CONCEALED]'
end

#each {|'[CONCEALED]'| ... } ⇒ Object

Yields:

  • ('[CONCEALED]') 


250
251
252
253
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 250

def each
  yield '[CONCEALED]' if block_given?
  self
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


152
153
154
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 152

def empty?
  @encrypted_data.to_s.empty?
end

#encrypted_value ⇒ String?

Access the encrypted data for database storage

This method is used internally by the field type system for persisting the encrypted data to the database.

Returns:

  • (String, nil) —

    The encrypted JSON data



171
172
173
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 171

def encrypted_value
  @encrypted_data
end

#gsub ⇒ Object 



236
237
238
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 236

def gsub(*)
  '[CONCEALED]'
end

#hash ⇒ Object

Consistent hash to prevent timing attacks



270
271
272
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 270

def hash
  ConcealedString.hash
end

#include?(_substring) ⇒ Boolean

Returns:

  • (Boolean) 


240
241
242
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 240

def include?(_substring)
  false # Never reveal substring presence
end

#inspect ⇒ Object

Safe representation for debugging and console output



256
257
258
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 256

def inspect
  '[CONCEALED]'
end

#length ⇒ Object 



197
198
199
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 197

def length
  11 # Fixed concealed length to match '[CONCEALED]' length
end

#map {|'[CONCEALED]'| ... } ⇒ Object

Enumerable methods for safety

Yields:

  • ('[CONCEALED]') 


245
246
247
248
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 245

def map
  yield '[CONCEALED]' if block_given?
  ['[CONCEALED]']
end

#present? ⇒ Boolean

Returns:

  • (Boolean) 


205
206
207
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 205

def present?
  true # Always return true since encrypted data exists
end

#reveal {|String| ... } ⇒ Object

Primary API: reveal the decrypted plaintext in a controlled block

This is the ONLY way to access plaintext from encrypted fields. The plaintext is decrypted fresh each time using the current record state and AAD context.

Security Warning: Avoid operations inside the block that create uncontrolled copies of the plaintext (dup, interpolation, etc.)

Example: user.api_token.reveal do |token| HTTP.post('/api', headers: { 'X-Token' => token }) end

Yields:

  • (String) —

    The decrypted plaintext value

Returns:

  • (Object) —

    The return value of the block

Raises:

  • (ArgumentError) 


89
90
91
92
93
94
95
96
97
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 89

def reveal
  raise ArgumentError, 'Block required for reveal' unless block_given?
  raise SecurityError, 'Encrypted data already cleared' if cleared?
  raise SecurityError, 'No encrypted data to reveal' if @encrypted_data.nil?

  # Decrypt using current record context and AAD
  plaintext = @field_type.decrypt_value(@record, @encrypted_data)
  yield plaintext
end

#size ⇒ Object 



201
202
203
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 201

def size
  length
end

#strip ⇒ Object

String pattern matching methods



232
233
234
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 232

def strip
  '[CONCEALED]'
end

#to_a ⇒ Object 



265
266
267
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 265

def to_a
  ['[CONCEALED]']
end

#to_h ⇒ Object

Hash/Array serialization safety



261
262
263
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 261

def to_h
  '[CONCEALED]'
end

#to_json ⇒ Object

Prevent exposure in JSON serialization - fail closed for security

Raises:



284
285
286
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 284

def to_json(*)
  raise Familia::SerializerError, 'ConcealedString cannot be serialized to JSON'
end

#to_s ⇒ Object

Prevent accidental exposure through string conversion and serialization

Ruby has two string conversion methods with different purposes:

  • to_s: explicit conversion (obj.to_s, string interpolation "#{obj}")
  • to_str: implicit coercion (File.read(obj), "prefix" + obj)

We implement to_s for safe logging/debugging but deliberately omit to_str to prevent encrypted data from being used where strings are expected.



184
185
186
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 184

def to_s
  '[CONCEALED]'
end

#upcase ⇒ Object

String methods that should return safe concealed values



189
190
191
 
# File 'lib/familia/features/encrypted_fields/concealed_string.rb', line 189

def upcase
  '[CONCEALED]'
end