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Enable adaptive download with variable block sizes

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The aim of this commit is to allow users of Meterpreter in high-latency
environments have better control over the behaviour of the download
function. This code contains two new options that manage the block size
of the downloads and the ability to set "adaptive" which means that the
block size will adjust on the fly of things continue to fail.
This commit is contained in:
OJ 2017-06-02 17:16:58 +10:00
parent abeececb46
commit cc0ff8f3db
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GPG Key ID: D5DC61FB93260597
2 changed files with 40 additions and 8 deletions
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42
lib/rex/post/meterpreter/extensions/stdapi/fs/file.rb
View File

@ -7,6 +7,7 @@ require 'rex/post/meterpreter/extensions/stdapi/stdapi'
require 'rex/post/meterpreter/extensions/stdapi/fs/io'
require 'rex/post/meterpreter/extensions/stdapi/fs/file_stat'
require 'fileutils'
require 'filesize'
module Rex
module Post
@ -25,6 +26,8 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
include Rex::Post::File
MIN_BLOCK_SIZE = 1024
class << self
attr_accessor :client
end
@ -312,7 +315,7 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
dest += timestamp
end
stat.call('downloading', src, dest) if (stat)
stat.call('Downloading', src, dest) if (stat)
result = download_file(dest, src, opts, &stat)
stat.call(result, src, dest) if (stat)
}
@ -325,8 +328,11 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
continue=false
tries=false
tries_no=0
stat ||= lambda { }
if opts
continue = true if opts["continue"]
adaptive = true if opts['adaptive']
tries = true if opts["tries"]
tries_no = opts["tries_no"]
end
@ -346,6 +352,8 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
dir = ::File.dirname(dest_file)
::FileUtils.mkdir_p(dir) if dir and not ::File.directory?(dir)
src_size = Filesize.new(src_stat.size).pretty
if continue
# continue downloading the file - skip downloaded part in the source
dst_fd = ::File.new(dest_file, "ab")
@ -353,10 +361,10 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
dst_fd.seek(0, ::IO::SEEK_END)
in_pos = dst_fd.pos
src_fd.seek(in_pos)
stat.call('continuing from ', in_pos, src_file) if (stat)
stat.call("Continuing from #{Filesize.new(in_pos).pretty} of #{src_size}", src_file, dest_file)
rescue
# if we can't seek, download again
stat.call('error continuing - downloading from scratch', src_file, dest_file) if (stat)
stat.call('Error continuing - downloading from scratch', src_file, dest_file)
dst_fd.close
dst_fd = ::File.new(dest_file, "wb")
end
@ -365,10 +373,12 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
end
# Keep transferring until EOF is reached...
block_size = opts['block_size'] || 1024 * 1024
begin
if tries
# resume when timeouts encountered
seek_back = false
adjust_block = false
tries_cnt = 0
begin # while
begin # exception
@ -376,30 +386,46 @@ class File < Rex::Post::Meterpreter::Extensions::Stdapi::Fs::IO
in_pos = dst_fd.pos
src_fd.seek(in_pos)
seek_back = false
stat.call('resuming at ', in_pos, src_file) if (stat)
stat.call("Resuming at #{Filesize.new(in_pos).pretty} of #{src_size}", src_file, dest_file)
else
# succesfully read and wrote - reset the counter
tries_cnt = 0
end
data = src_fd.read
adjust_block = true
data = src_fd.read(block_size)
adjust_block = false
rescue Rex::TimeoutError
# timeout encountered - either seek back and retry or quit
if (tries && (tries_no == 0 || tries_cnt < tries_no))
tries_cnt += 1
seek_back = true
stat.call('error downloading - retry #', tries_cnt, src_file) if (stat)
# try a smaller block size for the next round
if adaptive && adjust_block
block_size = [block_size >> 1, MIN_BLOCK_SIZE].max
adjust_block = false
msg = "Error downloading, block size set to #{block_size} - retry # #{tries_cnt}"
stat.call(msg, src_file, dest_file)
else
stat.call("Error downloading - retry # #{tries_cnt}", src_file, dest_file)
end
retry
else
stat.call('error downloading - giving up', src_file, dest_file) if (stat)
stat.call('Error downloading - giving up', src_file, dest_file)
raise
end
end
dst_fd.write(data) if (data != nil)
percent = dst_fd.pos.to_f / src_stat.size.to_f * 100.0
msg = "Downloaded #{Filesize.new(dst_fd.pos).pretty} of #{src_size} (#{percent.round(2)}%)"
stat.call(msg, src_file, dest_file)
end while (data != nil)
else
# do the simple copying quiting on the first error
while ((data = src_fd.read) != nil)
while ((data = src_fd.read(block_size)) != nil)
dst_fd.write(data)
percent = dst_fd.pos.to_f / src_stat.size.to_f * 100.0
msg = "Downloaded #{Filesize.new(dst_fd.pos).pretty} of #{src_size} (#{percent.round(2)}%)"
stat.call(msg, src_file, dest_file)
end
end
rescue EOFError

6
lib/rex/post/meterpreter/ui/console/command_dispatcher/stdapi/fs.rb
View File

@ -28,6 +28,8 @@ class Console::CommandDispatcher::Stdapi::Fs
@@download_opts = Rex::Parser::Arguments.new(
"-h" => [ false, "Help banner." ],
"-c" => [ false, "Resume getting a partially-downloaded file." ],
"-a" => [ false, "Enable adaptive download buffer size." ],
"-b" => [ true, "Set the initial block size for the download." ],
"-l" => [ true, "Set the limit of retries (0 unlimits)." ],
"-r" => [ false, "Download recursively." ],
"-t" => [ false, "Timestamp downloaded files." ])
@ -382,6 +384,10 @@ class Console::CommandDispatcher::Stdapi::Fs
@@download_opts.parse(args) { |opt, idx, val|
case opt
when "-a"
opts['adaptive'] = true
when "-b"
opts['block_size'] = val.to_i
when "-r"
recursive = true
opts['recursive'] = true