Module: PWNSandboxDriver

Defined in:
lib/pwn/plugins/sandbox/driver.rb

Overview

Standalone stdlib controller; target execution occurs only in the worker.

Class Method Summary collapse

Class Method Details

.authors ⇒ Object 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 14

public_class_method def self.authors
  'AUTHOR(S): 0day Inc. <[email protected]>'
end

.available?(name) ⇒ Boolean 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 25

def available?(name)
  ENV.fetch('PATH', '').split(File::PATH_SEPARATOR).any? { |dir| File.executable?(File.join(dir, name)) }
end

.bounded(command, seconds, input = '', memory = nil) ⇒ Object 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 29

def bounded(command, seconds, input = '', memory = nil)
  Tempfile.create('pwn-out') do |out|
    Tempfile.create('pwn-err') do |err|
      source, sink = IO.pipe
      begin
        source.binmode
        sink.binmode
        limits = { pgroup: true, in: source, out: out, err: err, rlimit_fsize: [8 * 1024 * 1024] * 2, rlimit_core: [0, 0] }
        limits[:rlimit_as] = [memory * 1024 * 1024] * 2 if memory
        pid = Process.spawn(*command, **limits)
        source.close
        writer = Thread.new do
          sink.write(input)
        rescue Errno::EPIPE, IOError
          nil
        ensure
          sink.close unless sink.closed?
        end
        deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + seconds
        expired = false
        status = nil
        loop do
          waited = Process.waitpid2(pid, Process::WNOHANG)
          if waited
            status = waited.last
            break
          end
          if Process.clock_gettime(Process::CLOCK_MONOTONIC) >= deadline
            expired = true
            Process.kill('KILL', -pid)
            status = Process.waitpid2(pid).last
            break
          end
          sleep 0.005
        end
        { exit: status.signaled? ? -status.termsig : status.exitstatus,
          stdout: File.binread(out.path, 65_536).to_s.dup.force_encoding('UTF-8').scrub,
          stderr: File.binread(err.path, 65_536).to_s.dup.force_encoding('UTF-8').scrub, timed_out: expired }
      ensure
        source.close unless source.closed?
        writer&.kill
        writer&.join(1)
        sink.close unless sink.closed?
        if pid
          begin
            Process.kill('KILL', -pid)
          rescue Errno::ESRCH
            nil
          end
          begin
            Process.waitpid(pid)
          rescue Errno::ECHILD
            nil
          end
        end
      end
    end
  end
end

.execute(request) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/pwn/plugins/sandbox/driver.rb', line 121

def execute(request)
  backend = request.fetch(:backend, 'docker')
  raise ArgumentError, "sandbox backend unavailable: #{backend}" unless %w[docker bwrap].include?(backend) && available?(backend)

  if backend == 'docker'
    probe = bounded(['docker', 'info', '--format', '{{.ServerVersion}}'], 10)
    raise ArgumentError, "docker backend unavailable: #{probe[:stderr]}" unless probe[:exit].zero?
  end
  seconds = Float(request.fetch(:timeout, 10))
  memory = Integer(request.fetch(:memory_mb, 256))
  raise ArgumentError, 'timeout or memory budget out of range' unless seconds.positive? && seconds <= 300 && memory.between?(32, 4096)

  argv = request.fetch(:argv, [])
  raise ArgumentError, 'argv must be an array of strings without NUL' unless argv.is_a?(Array) && argv.all? { |arg| arg.is_a?(String) && !arg.include?("\0") }

  binary = File.realpath(request.fetch(:binary))
  raise ArgumentError, 'binary must be a regular file' unless File.file?(binary)

  Dir.mktmpdir('pwn-sandbox-') do |artifacts|
    FileUtils.copy_file(binary, File.join(artifacts, 'target'))
    File.chmod(0o555, File.join(artifacts, 'target'))
    FileUtils.copy_file(__FILE__, File.join(artifacts, 'worker.rb'))
    payload = request.merge(timeout: seconds, memory_mb: memory, input: request.fetch(:stdin_base64) { Base64.strict_encode64(request.fetch(:stdin, '')) })
    container = "pwn-sandbox-#{SecureRandom.hex(16)}"
    if backend == 'docker'
      image = request.fetch(:image, 'pwn-sandbox:local')
      raise ArgumentError, 'invalid image' unless %r{\A[a-zA-Z0-9][a-zA-Z0-9_./:@-]*\z}.match?(image)

      File.chmod(0o755, artifacts)
      command = ['docker', 'run', '--rm', '--pull=never', '--name', container, '-i', '--network=none', '--read-only', '--cap-drop=ALL',
                 '--security-opt=no-new-privileges', '--pids-limit=64', '--memory', "#{memory}m", '--memory-swap', "#{memory}m",
                 '--cpus=1', '--user=65534:65534', '--tmpfs=/tmp:rw,nosuid,nodev,size=64m',
                 '--mount', "type=bind,src=#{artifacts},dst=/artifacts,readonly", '--entrypoint=/usr/bin/ruby', image, '/artifacts/worker.rb', '--inside']
    else
      command = ['bwrap', '--unshare-all', '--die-with-parent', '--new-session', '--cap-drop', 'ALL', '--clearenv', '--setenv', 'PATH', '/usr/bin:/bin', '--ro-bind', '/usr', '/usr']
      %w[/lib /lib64 /bin /sbin].each { |name| command.push('--ro-bind', name, name) if File.exist?(name) }
      command.push('--proc', '/proc', '--dev', '/dev', '--tmpfs', '/tmp', '--ro-bind', artifacts, '/artifacts', '--chdir', '/tmp', File.realpath('/usr/bin/ruby'), '/artifacts/worker.rb', '--inside')
    end
    begin
      result = bounded(command, (seconds * 3) + 10, JSON.generate(payload))
    ensure
      bounded(['docker', 'rm', '-f', container], 10) if backend == 'docker'
    end
    raise ArgumentError, "sandbox backend failed: #{result[:stderr]}" if !result[:exit].zero? || result[:timed_out]

    JSON.parse(result[:stdout], symbolize_names: true).merge(backend: backend, network: 'none', artifact_mount: 'ro', memory_mb: memory, timeout: seconds,
                                                             isolation_limitations: backend == 'bwrap' ? 'bwrap uses per-process RLIMIT_AS, not aggregate cgroup memory/pid limits' : nil)
  end
end

.fuzz(request) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/pwn/plugins/sandbox/driver.rb', line 187

def fuzz(request)
  minutes = Float(request.fetch(:minutes, 1))
  raise ArgumentError, 'minutes must be 0..60' unless minutes.positive? && minutes <= 60

  corpus = File.realpath(request.fetch(:corpus))
  seeds = Dir.children(corpus).sort.filter_map do |name|
    path = File.join(corpus, name)
    File.binread(path, 65_536).to_s if File.file?(path) && !File.symlink?(path)
  end.take(256)
  raise ArgumentError, 'empty corpus' if seeds.empty?

  rng = Random.new(request.fetch(:seed, 0))
  deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + (minutes * 60)
  crashes = []
  iterations = 0
  while Process.clock_gettime(Process::CLOCK_MONOTONIC) < deadline
    data = seeds.fetch(rng.rand(seeds.length)).dup
    data = +"\x00" if data.empty?
    index = rng.rand(data.bytesize)
    data.setbyte(index, data.getbyte(index) ^ (1 << rng.rand(8)))
    encoded = Base64.strict_encode64(data)
    remaining = deadline - Process.clock_gettime(Process::CLOCK_MONOTONIC)
    seconds = [Float(request.fetch(:timeout, 2)), (remaining / 3).clamp(0.01, Float::INFINITY)].min
    result = execute(request.merge(stdin_base64: encoded, timeout: seconds))
    return result unless result[:ok]

    iterations += 1
    crashes << result.merge(input_base64: encoded) if result[:signal]
    break if crashes.length >= 16
  end
  { ok: true, backend: request.fetch(:backend, 'docker'), iterations: iterations, crashes: crashes, seed: request.fetch(:seed, 0) }
end

.help ⇒ Object 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 18

public_class_method def self.help
  puts "Internal standalone Ruby sandbox controller/worker; use PWN::Plugins::Sandbox for the supported API.
    # Print the module author information.
    #{self}.authors"
end

.inside(request) ⇒ Object 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 89

def inside(request)
  command = ['/artifacts/target'] + request.fetch(:argv, [])
  data = Base64.strict_decode64(request.fetch(:input))
  seconds = request.fetch(:timeout)
  memory = request.fetch(:memory_mb)
  result = bounded(command, seconds, data, memory)
  sig = result[:exit].negative? ? Signal.signame(-result[:exit]) : nil
  result.merge!(ok: true, signal: sig && "SIG#{sig}", faulting_address: nil, backtrace: [], exploitability: 'unknown')
  if available?('strace')
    result[:strace] = bounded(['strace', '-f', '-qq', '-s', '128', '--'] + command, seconds, data, memory)[:stderr]
  else
    result[:strace_error] = 'strace unavailable in sandbox image'
  end
  if sig && available?('gdb')
    File.binwrite('/tmp/pwn-input', data)
    run = "run #{command.drop(1).shelljoin} < /tmp/pwn-input"
    replay = bounded(['gdb', '-q', '-nx', '-nh', '-batch', '-iex', 'set auto-load off', '-ex', run,
                      '-ex', 'p/x $pc', '-ex', 'bt', '-ex', 'exploitable', '--args', command.first], seconds, '', memory)
    text = replay[:stdout] + replay[:stderr]
    result[:gdb] = text
    result[:faulting_address] = text[/\$\d+ = (0x[0-9a-f]+)/, 1]
    result[:backtrace] = text.lines.map(&:chomp).grep(/\A#\d+\s/)
    result[:exploitability] = text[/Exploitability Classification:\s*(\S+)/, 1] || 'unknown: GDB exploitable plugin unavailable or failed'
  elsif sig
    result[:gdb_error] = 'gdb unavailable in sandbox image'
  end
  result
end

.main(request) ⇒ Object 



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# File 'lib/pwn/plugins/sandbox/driver.rb', line 220

def main(request)
  case request.fetch(:action, 'run')
  when 'fuzz'
    fuzz(request)
  when 'snapshot'
    snapshot(request)
  when 'rollback'
    path = File.realpath(request.fetch(:snapshot))
    root = File.realpath(File.join(Dir.home, '.pwn', 'sandbox_snapshots'))
    raise ArgumentError, 'unknown snapshot' unless File.dirname(path) == root

    target = File.join(path, 'target')
    expected = JSON.parse(File.read(File.join(path, 'manifest.json'))).fetch('sha256')
    raise ArgumentError, 'snapshot integrity failure' unless Digest::SHA256.file(target).hexdigest == expected

    execute(request.merge(binary: target))
  else
    execute(request)
  end
end

.snapshot(request) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/pwn/plugins/sandbox/driver.rb', line 171

def snapshot(request)
  root = File.join(Dir.home, '.pwn', 'sandbox_snapshots')
  FileUtils.mkdir_p(root, mode: 0o700)
  target = File.realpath(request.fetch(:binary))
  raise ArgumentError, 'binary must be a regular file' unless File.file?(target)

  data = File.binread(target)
  digest = Digest::SHA256.hexdigest(data)
  dest = File.join(root, SecureRandom.hex(16))
  Dir.mkdir(dest, 0o700)
  File.binwrite(File.join(dest, 'target'), data)
  File.chmod(0o500, File.join(dest, 'target'))
  File.write(File.join(dest, 'manifest.json'), JSON.generate(sha256: digest))
  { ok: true, snapshot: dest, sha256: digest, semantics: 'immutable input snapshot; rollback creates a fresh disposable environment, not a live process checkpoint' }
end