discourse/lib/compression/strategy.rb

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# frozen_string_literal: true
module Compression
class Strategy
ExtractFailed = Class.new(StandardError)
DestinationFileExistsError = Class.new(StandardError)
def can_handle?(file_name)
file_name.include?(extension)
end
def decompress(dest_path, compressed_file_path, max_size)
sanitized_compressed_file_path = sanitize_path(compressed_file_path)
sanitized_dest_path = sanitize_path(dest_path)
get_compressed_file_stream(sanitized_compressed_file_path) do |compressed_file|
available_size = calculate_available_size(max_size)
entries_of(compressed_file).each do |entry|
entry_path = build_entry_path(sanitized_dest_path, entry, sanitized_compressed_file_path)
next if !is_safe_path_for_extraction?(entry_path, sanitized_dest_path)
FileUtils.mkdir_p(File.dirname(entry_path))
if is_file?(entry)
remaining_size = extract_file(entry, entry_path, available_size)
available_size = remaining_size
else
extract_folder(entry, entry_path)
end
end
decompression_results_path(sanitized_dest_path, sanitized_compressed_file_path)
end
end
private
def sanitize_path(filename)
Pathname.new(filename).realpath.to_s
end
# https://guides.rubyonrails.org/security.html#file-uploads
def sanitize_filename(filename)
filename.strip.tap do |name|
# NOTE: File.basename doesn't work right with Windows paths on Unix
# get only the filename, not the whole path
name.sub! %r{\A.*(\\|/)}, ""
# Finally, replace all non alphanumeric, underscore
# or periods with underscore
name.gsub! /[^\w\.\-]/, "_"
end
end
def calculate_available_size(max_size)
1024**2 * (max_size / 1.049) # Mb to Mib
end
def entries_of(compressed_file)
compressed_file
end
def is_file?(entry)
entry.file?
end
def chunk_size
@chunk_size ||= 1024**2 * 2 # 2MiB
end
def extract_file(entry, entry_path, available_size)
remaining_size = available_size
if ::File.exist?(entry_path)
raise DestinationFileExistsError, "Destination '#{entry_path}' already exists"
end
::File.open(entry_path, "wb") do |os|
while (buf = entry.read(chunk_size))
remaining_size -= buf.size
raise ExtractFailed if remaining_size.negative?
os << buf
end
end
remaining_size
end
def is_safe_path_for_extraction?(path, dest_directory)
File.expand_path(path).start_with?(dest_directory)
end
end
end