lib/rubygems/package/tar_writer.rb
# frozen_string_literal: true
# rubocop:disable Style/AsciiComments
# Copyright (C) 2004 Mauricio Julio Fernández Pradier
# See LICENSE.txt for additional licensing information.
# rubocop:enable Style/AsciiComments
##
# Allows writing of tar files
class Gem::Package::TarWriter
class FileOverflow < StandardError; end
##
# IO wrapper that allows writing a limited amount of data
class BoundedStream
##
# Maximum number of bytes that can be written
attr_reader :limit
##
# Number of bytes written
attr_reader :written
##
# Wraps +io+ and allows up to +limit+ bytes to be written
def initialize(io, limit)
@io = io
@limit = limit
@written = 0
end
##
# Writes +data+ onto the IO, raising a FileOverflow exception if the
# number of bytes will be more than #limit
def write(data)
if data.bytesize + @written > @limit
raise FileOverflow, "You tried to feed more data than fits in the file."
end
@io.write data
@written += data.bytesize
data.bytesize
end
end
##
# IO wrapper that provides only #write
class RestrictedStream
##
# Creates a new RestrictedStream wrapping +io+
def initialize(io)
@io = io
end
##
# Writes +data+ onto the IO
def write(data)
@io.write data
end
end
##
# Creates a new TarWriter, yielding it if a block is given
def self.new(io)
writer = super
return writer unless block_given?
begin
yield writer
ensure
writer.close
end
nil
end
##
# Creates a new TarWriter that will write to +io+
def initialize(io)
@io = io
@closed = false
end
##
# Adds file +name+ with permissions +mode+, and yields an IO for writing the
# file to
def add_file(name, mode) # :yields: io
check_closed
name, prefix = split_name name
init_pos = @io.pos
@io.write Gem::Package::TarHeader::EMPTY_HEADER # placeholder for the header
yield RestrictedStream.new(@io) if block_given?
size = @io.pos - init_pos - 512
remainder = (512 - (size % 512)) % 512
@io.write "\0" * remainder
final_pos = @io.pos
@io.pos = init_pos
header = Gem::Package::TarHeader.new name: name, mode: mode,
size: size, prefix: prefix,
mtime: Gem.source_date_epoch
@io.write header
@io.pos = final_pos
self
end
##
# Adds +name+ with permissions +mode+ to the tar, yielding +io+ for writing
# the file. The +digest_algorithm+ is written to a read-only +name+.sum
# file following the given file contents containing the digest name and
# hexdigest separated by a tab.
#
# The created digest object is returned.
def add_file_digest(name, mode, digest_algorithms) # :yields: io
digests = digest_algorithms.map do |digest_algorithm|
digest = digest_algorithm.new
digest_name =
if digest.respond_to? :name
digest.name
else
digest_algorithm.class.name[/::([^:]+)\z/, 1]
end
[digest_name, digest]
end
digests = Hash[*digests.flatten]
add_file name, mode do |io|
Gem::Package::DigestIO.wrap io, digests do |digest_io|
yield digest_io
end
end
digests
end
##
# Adds +name+ with permissions +mode+ to the tar, yielding +io+ for writing
# the file. The +signer+ is used to add a digest file using its
# digest_algorithm per add_file_digest and a cryptographic signature in
# +name+.sig. If the signer has no key only the checksum file is added.
#
# Returns the digest.
def add_file_signed(name, mode, signer)
digest_algorithms = [
signer.digest_algorithm,
Gem::Security.create_digest("SHA512"),
].compact.uniq
digests = add_file_digest name, mode, digest_algorithms do |io|
yield io
end
signature_digest = digests.values.compact.find do |digest|
digest_name =
if digest.respond_to? :name
digest.name
else
digest.class.name[/::([^:]+)\z/, 1]
end
digest_name == signer.digest_name
end
raise "no #{signer.digest_name} in #{digests.values.compact}" unless signature_digest
if signer.key
signature = signer.sign signature_digest.digest
add_file_simple "#{name}.sig", 0o444, signature.length do |io|
io.write signature
end
end
digests
end
##
# Add file +name+ with permissions +mode+ +size+ bytes long. Yields an IO
# to write the file to.
def add_file_simple(name, mode, size) # :yields: io
check_closed
name, prefix = split_name name
header = Gem::Package::TarHeader.new(name: name, mode: mode,
size: size, prefix: prefix,
mtime: Gem.source_date_epoch).to_s
@io.write header
os = BoundedStream.new @io, size
yield os if block_given?
min_padding = size - os.written
@io.write("\0" * min_padding)
remainder = (512 - (size % 512)) % 512
@io.write("\0" * remainder)
self
end
##
# Adds symlink +name+ with permissions +mode+, linking to +target+.
def add_symlink(name, target, mode)
check_closed
name, prefix = split_name name
header = Gem::Package::TarHeader.new(name: name, mode: mode,
size: 0, typeflag: "2",
linkname: target,
prefix: prefix,
mtime: Gem.source_date_epoch).to_s
@io.write header
self
end
##
# Raises IOError if the TarWriter is closed
def check_closed
raise IOError, "closed #{self.class}" if closed?
end
##
# Closes the TarWriter
def close
check_closed
@io.write "\0" * 1024
flush
@closed = true
end
##
# Is the TarWriter closed?
def closed?
@closed
end
##
# Flushes the TarWriter's IO
def flush
check_closed
@io.flush if @io.respond_to? :flush
end
##
# Creates a new directory in the tar file +name+ with +mode+
def mkdir(name, mode)
check_closed
name, prefix = split_name(name)
header = Gem::Package::TarHeader.new name: name, mode: mode,
typeflag: "5", size: 0,
prefix: prefix,
mtime: Gem.source_date_epoch
@io.write header
self
end
##
# Splits +name+ into a name and prefix that can fit in the TarHeader
def split_name(name) # :nodoc:
if name.bytesize > 256
raise Gem::Package::TooLongFileName.new("File \"#{name}\" has a too long path (should be 256 or less)")
end
prefix = ""
if name.bytesize > 100
parts = name.split("/", -1) # parts are never empty here
name = parts.pop # initially empty for names with a trailing slash ("foo/.../bar/")
prefix = parts.join("/") # if empty, then it's impossible to split (parts is empty too)
while !parts.empty? && (prefix.bytesize > 155 || name.empty?)
name = parts.pop + "/" + name
prefix = parts.join("/")
end
if name.bytesize > 100 || prefix.empty?
raise Gem::Package::TooLongFileName.new("File \"#{prefix}/#{name}\" has a too long name (should be 100 or less)")
end
if prefix.bytesize > 155
raise Gem::Package::TooLongFileName.new("File \"#{prefix}/#{name}\" has a too long base path (should be 155 or less)")
end
end
[name, prefix]
end
end