Untangle encryption and decompression

lib/zip.rb

@@ -21,6 +21,7 @@ require 'zip/null_compressor'
 require 'zip/null_input_stream'
 require 'zip/pass_thru_compressor'
 require 'zip/pass_thru_decompressor'
+require 'zip/crypto/decrypted_io'
 require 'zip/crypto/encryption'
 require 'zip/crypto/null_encryption'
 require 'zip/crypto/traditional_encryption'

lib/zip/crypto/decrypted_io.rb

@@ -0,0 +1,39 @@
+module Zip
+  class DecryptedIo #:nodoc:all
+    CHUNK_SIZE = 32_768
+
+    def initialize(io, decrypter)
+      @io = io
+      @decrypter = decrypter
+    end
+
+    def read(length = nil, outbuf = '')
+      return ((length.nil? || length.zero?) ? "" : nil) if eof
+
+      while length.nil? || (buffer.bytesize < length)
+        break if input_finished?
+        buffer << produce_input
+      end
+
+      outbuf.replace(buffer.slice!(0...(length || output_buffer.bytesize)))
+    end
+
+    private
+
+    def eof
+      buffer.empty? && input_finished?
+    end
+
+    def buffer
+      @buffer ||= ''.dup
+    end
+
+    def input_finished?
+      @io.eof
+    end
+
+    def produce_input
+      @decrypter.decrypt(@io.read(CHUNK_SIZE))
+    end
+  end
+end

lib/zip/file.rb

@@ -49,7 +49,7 @@ module Zip
     MAX_SEGMENT_SIZE     = 3_221_225_472
     MIN_SEGMENT_SIZE     = 65_536
     DATA_BUFFER_SIZE     = 8192
-    IO_METHODS           = [:tell, :seek, :read, :close]
+    IO_METHODS           = [:tell, :seek, :read, :eof, :close]
 
     DEFAULT_OPTIONS = {
       restore_ownership:   false,

lib/zip/inflater.rb

@@ -1,11 +1,10 @@
 module Zip
   class Inflater < Decompressor #:nodoc:all
-    def initialize(input_stream, decrypter = NullDecrypter.new)
+    def initialize(input_stream)
       super(input_stream)
       @zlib_inflater           = ::Zlib::Inflate.new(-Zlib::MAX_WBITS)
       @output_buffer           = ''.dup
       @has_returned_empty_string = false
-      @decrypter = decrypter
     end
 
     def sysread(number_of_bytes = nil, buf = '')
@@ -30,7 +29,7 @@ module Zip
     def internal_produce_input(buf = '')
       retried = 0
       begin
-        @zlib_inflater.inflate(@decrypter.decrypt(@input_stream.read(Decompressor::CHUNK_SIZE, buf)))
+        @zlib_inflater.inflate(@input_stream.read(Decompressor::CHUNK_SIZE, buf))
       rescue Zlib::BufError
         raise if retried >= 5 # how many times should we retry?
         retried += 1

lib/zip/input_stream.rb

@@ -147,7 +147,8 @@ module Zip
       elsif @current_entry.compression_method == ::Zip::Entry::DEFLATED
         header = @archive_io.read(@decrypter.header_bytesize)
         @decrypter.reset!(header)
-        ::Zip::Inflater.new(@archive_io, @decrypter)
+        decrypted_io = ::Zip::DecryptedIo.new(@archive_io, @decrypter)
+        ::Zip::Inflater.new(decrypted_io)
       else
         raise ::Zip::CompressionMethodError,
               "Unsupported compression method #{@current_entry.compression_method}"