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|
# frozen_string_literal: true
require 'openssl'
module Zip
module AESEncryption # :nodoc:
VERIFIER_LENGTH = 2
BLOCK_SIZE = 16
AUTHENTICATION_CODE_LENGTH = 10
VERSION_AE_1 = 0x01
VERSION_AE_2 = 0x02
VERSIONS = [
VERSION_AE_1,
VERSION_AE_2
].freeze
STRENGTH_128_BIT = 0x01
STRENGTH_192_BIT = 0x02
STRENGTH_256_BIT = 0x03
STRENGTHS = [
STRENGTH_128_BIT,
STRENGTH_192_BIT,
STRENGTH_256_BIT
].freeze
BITS = {
STRENGTH_128_BIT => 128,
STRENGTH_192_BIT => 192,
STRENGTH_256_BIT => 256
}.freeze
KEY_LENGTHS = {
STRENGTH_128_BIT => 16,
STRENGTH_192_BIT => 24,
STRENGTH_256_BIT => 32
}.freeze
SALT_LENGTHS = {
STRENGTH_128_BIT => 8,
STRENGTH_192_BIT => 12,
STRENGTH_256_BIT => 16
}.freeze
def initialize(password, strength)
@password = password
@strength = strength
@bits = BITS[@strength]
@key_length = KEY_LENGTHS[@strength]
@salt_length = SALT_LENGTHS[@strength]
end
def header_bytesize
@salt_length + VERIFIER_LENGTH
end
def gp_flags
0x0001
end
end
class AESDecrypter < Decrypter # :nodoc:
include AESEncryption
def decrypt(encrypted_data)
@hmac.update(encrypted_data)
idx = 0
decrypted_data = +''
amount_to_read = encrypted_data.size
while amount_to_read.positive?
@cipher.iv = [@counter + 1].pack('Vx12')
begin_index = BLOCK_SIZE * idx
end_index = begin_index + [BLOCK_SIZE, amount_to_read].min
decrypted_data << @cipher.update(encrypted_data[begin_index...end_index])
amount_to_read -= BLOCK_SIZE
@counter += 1
idx += 1
end
# JRuby requires finalization of the cipher. This is a bug, as noted in
# jruby/jruby-openssl#182 and jruby/jruby-openssl#183.
decrypted_data << @cipher.final if defined?(JRUBY_VERSION)
decrypted_data
end
def reset!(header)
raise Error, "Unsupported encryption AES-#{@bits}" unless STRENGTHS.include? @strength
salt = header[0...@salt_length]
pwd_verify = header[-VERIFIER_LENGTH..]
key_material = OpenSSL::KDF.pbkdf2_hmac(
@password,
salt: salt,
iterations: 1000,
length: (2 * @key_length) + VERIFIER_LENGTH,
hash: 'sha1'
)
enc_key = key_material[0...@key_length]
enc_hmac_key = key_material[@key_length...(2 * @key_length)]
enc_pwd_verify = key_material[-VERIFIER_LENGTH..]
raise Error, 'Bad password' if enc_pwd_verify != pwd_verify
@counter = 0
@cipher = OpenSSL::Cipher::AES.new(@bits, :CTR)
@cipher.decrypt
@cipher.key = enc_key
@hmac = OpenSSL::HMAC.new(enc_hmac_key, OpenSSL::Digest.new('SHA1'))
end
def check_integrity!(io)
auth_code = io.read(AUTHENTICATION_CODE_LENGTH)
raise Error, 'Integrity fault' if @hmac.digest[0...AUTHENTICATION_CODE_LENGTH] != auth_code
end
end
end
|
