Class: Omnizip::Formats::SevenZip::EncryptedHeader

Inherits:
Object
  • Object
show all
Includes:
Constants
Defined in:
lib/omnizip/formats/seven_zip/encrypted_header.rb

Overview

Encrypted header model for .7z archives Stores metadata for header encryption

Constant Summary

Constants included from Constants

Constants::MAJOR_VERSION, Constants::MAX_NUM_BONDS, Constants::MAX_NUM_CODERS, Constants::MAX_NUM_PACK_STREAMS, Constants::MINOR_VERSION, Constants::SIGNATURE, Constants::SIGNATURE_SIZE, Constants::START_HEADER_SIZE

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(encrypted_data: nil, salt: nil, iv: nil, original_size: 0, crc: nil) ⇒ EncryptedHeader

Initialize encrypted header

Parameters:

  • encrypted_data (String) (defaults to: nil) —

    Encrypted header bytes

  • salt (String) (defaults to: nil) —

    PBKDF2 salt

  • iv (String) (defaults to: nil) —

    AES initialization vector

  • original_size (Integer) (defaults to: 0) —

    Size before encryption

  • crc (Integer, nil) (defaults to: nil) —

    CRC32 of encrypted data (optional)



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 20

def initialize(encrypted_data: nil, salt: nil, iv: nil,
               original_size: 0, crc: nil)
  @encrypted_data = encrypted_data
  @salt = salt
  @iv = iv
  @original_size = original_size
  @crc = crc
end

Instance Attribute Details

#crc ⇒ Object

Returns the value of attribute crc.



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 11

def crc
  @crc
end

#encrypted_data ⇒ Object

Returns the value of attribute encrypted_data.



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 11

def encrypted_data
  @encrypted_data
end

#iv ⇒ Object

Returns the value of attribute iv.



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 11

def iv
  @iv
end

#original_size ⇒ Object

Returns the value of attribute original_size.



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 11

def original_size
  @original_size
end

#salt ⇒ Object

Returns the value of attribute salt.



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 11

def salt
  @salt
end

Class Method Details

.from_binary(data) ⇒ EncryptedHeader

Parse encrypted header from binary data

Parameters:

  • data (String) —

    Binary data

Returns:

Raises:

  • (RuntimeError) —

    if data is invalid



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 71

def self.from_binary(data)
  raise "Invalid encrypted header: too short" if data.bytesize < 54

  pos = 0

  # Check marker
  marker = data.getbyte(pos)
  pos += 1
  unless marker == PropertyId::ENCODED_HEADER
    raise "Invalid encrypted header marker: expected #{PropertyId::ENCODED_HEADER}, got #{marker}"
  end

  # Read encrypted data size
  encrypted_size = data[pos, 8].unpack1("Q<")
  pos += 8

  # Read salt
  salt = data[pos, 16]
  pos += 16

  # Read IV
  iv = data[pos, 16]
  pos += 16

  # Read original size
  original_size = data[pos, 8].unpack1("Q<")
  pos += 8

  # Read CRC
  crc = data[pos, 4].unpack1("V")
  pos += 4

  # Read encrypted data
  encrypted_data = data[pos, encrypted_size]

  new(
    encrypted_data: encrypted_data,
    salt: salt,
    iv: iv,
    original_size: original_size,
    crc: crc.zero? ? nil : crc,
  )
end

Instance Method Details

#to_binary ⇒ String

Serialize encrypted header to binary format

Format:

- 1 byte: PropertyId::ENCODED_HEADER marker
- 8 bytes: Encrypted data size (little-endian)
- 16 bytes: Salt
- 16 bytes: IV
- 8 bytes: Original size (little-endian)
- 4 bytes: CRC32 (optional, 0 if not set)
- N bytes: Encrypted data

Returns:

  • (String) —

    Binary representation



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 41

def to_binary
  data = String.new(encoding: "BINARY")

  # Marker for encoded header
  data << [PropertyId::ENCODED_HEADER].pack("C")

  # Encrypted data size
  data << [@encrypted_data.bytesize].pack("Q<")

  # Encryption parameters
  data << @salt
  data << @iv

  # Original size
  data << [@original_size].pack("Q<")

  # CRC (0 if not set)
  data << [crc || 0].pack("V")

  # Encrypted data
  data << @encrypted_data

  data
end

#valid? ⇒ Boolean

Check if header is valid

Returns:

  • (Boolean) —

    true if has all required fields



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 118

def valid?
  !@encrypted_data.nil? &&
    !@salt.nil? &&
    !@iv.nil? &&
    @original_size.positive? &&
    @encrypted_data.bytesize.positive?
end

#verify_crc ⇒ Boolean

Verify CRC if set

Returns:

  • (Boolean) —

    true if CRC matches or not set



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# File 'lib/omnizip/formats/seven_zip/encrypted_header.rb', line 129

def verify_crc
  return true if @crc.nil?

  calc_crc = Omnizip::Checksums::Crc32.new
  calc_crc.update(@encrypted_data)
  calc_crc.value == @crc
end