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# Copyright 2011-2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
module AWS
class S3
# @api private
class CipherIO
def initialize cipher, stream, stream_size = nil
@stream = stream
@stream_size = stream_size
@orig_cipher = cipher.clone
reset_cipher
# add a #rewind method if the original stream can be rewound
if @stream.respond_to?(:rewind)
Core::MetaUtils.extend_method(self, :rewind) do
reset_cipher
@stream.rewind
end
end
# add a #size method if the stream size is known
if stream_size
Core::MetaUtils.extend_method(self, :size) do
EncryptionUtils.get_encrypted_size(@stream_size)
end
end
end
# @return [String] Returns the requested number of bytes. If no byte
# amount is given, it will return the entire body of encrypted data
def read bytes = nil, output_buffer = nil
data = if bytes
(@eof) ? nil : read_chunk(bytes)
else
(@eof) ? "" : read_all
end
output_buffer ? output_buffer.replace(data || '') : data
end
# @return [Boolean] Returns `true` when the entire stream has been read.
def eof?
@eof
end
private
attr_reader :cipher
# Sets the CipherIO in a reset state without having to know anything
# about the cipher
def reset_cipher
@cipher = @orig_cipher.clone
@eof = false
@final = nil
end
# @return [String] Returns an encrytped chunk
def read_chunk bytes
unless @final
# If given a number of bytes, read it out and work out encryption
# issues
chunk = @stream.read(bytes)
# If there is nothing, finish the encryption
if chunk and chunk.length > 0
handle_finish(bytes, cipher.update(chunk))
else
@eof = true
cipher.final
end
# Read as much as possible if not given a byte size
else
@eof = true
@final
end
end
# @return [String] Returns the entire encrypted data
def read_all
@eof = true
body = @stream.read()
data = (body and body.length > 0) ? cipher.update(body) : ""
data << cipher.final
end
# Figures out how much of the final block goes into the current chunk
# and adds it.
# @return [String] Returns the encrypted chunk with possible padding.
def handle_finish(bytes, chunk)
free_space = bytes - chunk.size
if free_space > 0
@final = cipher.final
chunk << @final[0..free_space-1]
@final = @final[free_space..@final.size-1]
@eof = true unless @final and @final.size > 0
end
chunk
end
end
end
end
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