change regex to filesystem policy matcher, first step of DMOJ#871

.freebsd.test.py

@@ -31,13 +31,18 @@
 
 def main():
  judgeenv.env['runtime'] = {}
- judgeenv.env['extra_fs'] = {'PERL': ['/dev/dtrace/helper$'], 'RUBY2': ['/dev/dtrace/helper$']}
+ judgeenv.env['extra_fs'] = {
+ 'PERL': [{"exact_file": "/dev/dtrace/helper"}],
+ 'RUBY2': [{"exact_file": "/dev/dtrace/helper"}]
+ }
 
  logging.basicConfig(level=logging.INFO)
 
  print('Using extra allowed filesystems:')
  for lang, fs in judgeenv.env['extra_fs'].iteritems():
- print('%-6s: %s' % (lang, '|'.join(fs)))
+ for rules in fs:
+ for access_type, file in rules.iteritems():
+ print('%-6s: %s: %s' % (lang, access_type, file))
  print()
 
  print('Testing executors...')

dmoj/cptbox/isolate.py

@@ -1,6 +1,5 @@
 import logging
 import os
-import re
 import sys
 
 from dmoj.cptbox._cptbox import AT_FDCWD, bsd_get_proc_cwd, bsd_get_proc_fdno
@@ -9,6 +8,7 @@
 
 from dmoj.cptbox.syscalls import *
 from dmoj.utils.unicode import utf8text
+from dmoj.executors.filesystem_policies import FilesystemPolicy
 
 log = logging.getLogger('dmoj.security')
 open_write_flags = [os.O_WRONLY, os.O_RDWR, os.O_TRUNC, os.O_CREAT, os.O_EXCL]
@@ -184,12 +184,7 @@ def __init__(self, read_fs, write_fs=None, writable=(1, 2)):
  )
 
  def _compile_fs_jail(self, fs):
- if fs:
- fs_re = '|'.join(fs)
- else:
- fs_re = '(?!)' # Disallow accessing everything by default.
-
- return re.compile(fs_re)
+ return FilesystemPolicy(fs or [])
 
  def is_write_flags(self, open_flags):
  for flag in open_write_flags:
@@ -258,9 +253,7 @@ def _file_access_check(self, rel_file, debugger, is_open, flag_reg=1, dirfd=AT_F
 
  is_write = is_open and self.is_write_flags(getattr(debugger, 'uarg%d' % flag_reg))
  fs_jail = self.write_fs_jail if is_write else self.read_fs_jail
- if fs_jail.match(file) is None:
- return file, False
- return file, True
+ return file, fs_jail.check(file)
 
  def get_full_path(self, debugger, file, dirfd=AT_FDCWD):
  dirfd = (dirfd & 0x7FFFFFFF) - (dirfd & 0x80000000)

dmoj/executors/COFFEE.py

@@ -1,6 +1,7 @@
 import os
 
 from dmoj.executors.script_executor import ScriptExecutor
+from dmoj.executors.filesystem_policies import ExactFile
 
 
 class Executor(ScriptExecutor):
@@ -38,7 +39,7 @@ def get_cmdline(self, **kwargs):
  return [self.get_command(), self.runtime_dict['coffee'], self._code]
 
  def get_fs(self):
- return super().get_fs() + [self.runtime_dict['coffee'], self._code]
+ return super().get_fs() + [ExactFile(self.runtime_dict['coffee']), ExactFile(self._code)]
 
  @classmethod
  def get_versionable_commands(cls):

dmoj/executors/DART.py

@@ -16,7 +16,6 @@ class Executor(CompiledExecutor):
  address_grace = 128 * 1024
 
  syscalls = ['epoll_create', 'epoll_ctl', 'epoll_wait', 'timerfd_settime', 'memfd_create', 'ftruncate']
- fs = ['.*/vm-service$']
 
  def get_compile_args(self):
  return [self.get_command(), '--snapshot=%s' % self.get_compiled_file(), self._code]

dmoj/executors/FORTH.py

@@ -1,4 +1,5 @@
 from dmoj.executors.script_executor import ScriptExecutor
+from dmoj.executors.filesystem_policies import ExactFile
 
 
 class Executor(ScriptExecutor):
@@ -10,7 +11,7 @@ class Executor(ScriptExecutor):
 
 HELLO
 '''
- fs = [r'/\.gforth-history$']
+ fs = [ExactFile('/.gforth-history')]
 
  def get_cmdline(self, **kwargs):
  return [self.get_command(), self._code, '-e', 'bye']

dmoj/executors/PERL.py

@@ -1,11 +1,12 @@
 from dmoj.executors.script_executor import ScriptExecutor
+from dmoj.executors.filesystem_policies import RecursiveDir
 
 
 class Executor(ScriptExecutor):
  ext = 'pl'
  name = 'PERL'
  command = 'perl'
- fs = ['/etc/perl/.*?']
+ fs = [RecursiveDir('/etc/perl')]
  test_program = 'print<>'
  syscalls = ['umtx_op']
 

dmoj/executors/PHP.py

@@ -7,8 +7,6 @@ class Executor(ScriptExecutor):
  command = 'php'
  command_paths = ['php7', 'php5', 'php']
 
- fs = [r'.*/php[\w-]*\.ini$', r'.*/conf.d/.*\.ini$']
-
  test_program = '<?php while($f = fgets(STDIN)) echo $f;'
 
  def get_cmdline(self, **kwargs):

dmoj/executors/RKT.py

@@ -1,13 +1,11 @@
-import os
-
 from dmoj.executors.compiled_executor import CompiledExecutor
+from dmoj.executors.filesystem_policies import RecursiveDir, ExactFile
 
 
 class Executor(CompiledExecutor):
  ext = 'rkt'
  name = 'RKT'
- fs = [os.path.expanduser(r'~/\.racket/'), os.path.expanduser(r'~/\.local/share/racket/'),
- '/etc/racket/.*?', '/etc/passwd$']
+ fs = [RecursiveDir("/etc/racket"), ExactFile("/etc/passwd")]
 
  command = 'racket'
 

dmoj/executors/RUBY2.py

@@ -2,6 +2,7 @@
 import re
 
 from dmoj.executors.script_executor import ScriptExecutor
+from dmoj.executors.filesystem_policies import ExactFile
 
 
 class Executor(ScriptExecutor):
@@ -12,7 +13,7 @@ class Executor(ScriptExecutor):
  nproc = -1
  command_paths = ['ruby2.%d' % i for i in reversed(range(0, 8))] + ['ruby2%d' % i for i in reversed(range(0, 8))]
  syscalls = ['thr_set_name', 'eventfd2']
- fs = ['/proc/self/loginuid$']
+ fs = [ExactFile('/proc/self/loginuid')]
 
  def get_fs(self):
  fs = super().get_fs()

dmoj/executors/SWIFT.py

@@ -5,7 +5,6 @@ class Executor(CompiledExecutor):
  ext = 'swift'
  name = 'SWIFT'
  command = 'swiftc'
- fs = ['/lib']
  test_program = 'print(readLine()!)'
 
  def get_compile_args(self):

dmoj/executors/TUR.py

@@ -2,6 +2,7 @@
 
 from dmoj.executors.compiled_executor import CompiledExecutor
 from dmoj.judgeenv import env
+from dmoj.executors.filesystem_policies import ExactFile
 
 
 class Executor(CompiledExecutor):
@@ -15,7 +16,7 @@ class Executor(CompiledExecutor):
 '''
 
  def get_fs(self):
- return super().get_fs() + [self._code + 'bc']
+ return super().get_fs() + [ExactFile(self._code + 'bc')]
 
  def get_compile_args(self):
  tprologc = self.runtime_dict['tprologc']

dmoj/executors/filesystem_policies.py

@@ -0,0 +1,114 @@
+import os
+from typing import List, Union
+
+
+class ACCESS_MODE:
+ NONE = 0
+ EXACT = 1
+ RECURSIVE = 2
+
+
+class Dir:
+ def __init__(self):
+ self.access_mode = ACCESS_MODE.NONE
+ self.map = {}
+
+
+class File:
+ pass
+
+
+class ExactFile:
+ def __init__(self, path: str):
+ self.path = path
+
+
+class ExactDir:
+ access_mode = ACCESS_MODE.EXACT
+
+ def __init__(self, path: str):
+ self.path = path
+
+
+class RecursiveDir:
+ access_mode = ACCESS_MODE.RECURSIVE
+
+ def __init__(self, path: str):
+ self.path = path
+
+
+Rule = Union[ExactFile, ExactDir, RecursiveDir]
+
+
+class FilesystemPolicy:
+ def __init__(self, rules: List[Rule]):
+ self.root = Dir()
+ for rule in rules:
+ self._add_rule(rule)
+
+ def _add_rule(self, rule: Rule):
+ self._assert_rule_type(rule)
+ if rule.path == "/":
+ return self._finalize_root_rule(rule)
+
+ path = rule.path
+ assert os.path.isabs(path), "Rule must specify an absolute path to rule"
+ *directory_path, final_component = path.split("/")[1:]
+
+ node = self.root
+ for component in directory_path:
+ assert component != "", "Must not have empty components in rule to add"
+ new_node = node.map.setdefault(component, Dir())
+ assert isinstance(new_node, Dir), "Cannot descend into non-directory"
+ node = new_node
+
+ self._finalize_rule(node, final_component, rule)
+
+ def _assert_rule_type(self, rule: Rule):
+ if os.path.exists(rule.path):
+ is_dir = os.path.isdir(rule.path)
+ if isinstance(rule, ExactFile):
+ assert not is_dir, f"Can't apply file rule to directory {rule.path}"
+ else:
+ assert is_dir, f"Can't apply directory rule to non-directory {rule.path}"
+
+ def _finalize_root_rule(self, rule: Rule):
+ assert not isinstance(rule, ExactFile), "Root is not a file"
+ self._finalize_directory_rule(self.root, rule)
+
+ def _finalize_rule(self, node: Dir, final_component: str, rule: Rule):
+ assert final_component != "", "Must not have trailing slashes in rule path"
+ if isinstance(rule, ExactFile):
+ new_node = node.map.setdefault(final_component, File())
+ assert isinstance(new_node, File), "Can't add ExactFile: Dir rule exists"
+ else:
+ new_node = node.map.setdefault(final_component, Dir())
+ assert isinstance(new_node, Dir), "Can't add rule: File rule exists"
+ self._finalize_directory_rule(new_node, rule)
+
+ def _finalize_directory_rule(self, node: Dir, rule: Union[ExactDir, RecursiveDir]):
+ node.access_mode = max(node.access_mode, rule.access_mode) # Allow the more permissive rule
+
+ # `path` should be a canonical path. The output of `realpath` is appropriate
+ def check(self, path: str) -> bool:
+ if path == "/":
+ return self._check_final_node(self.root)
+
+ assert os.path.isabs(path), "Must pass an absolute path to check"
+
+ node = self.root
+ for component in path.split("/")[1:]:
+ assert component != "", "Must not have empty components in path to check"
+ if isinstance(node, File):
+ return False
+ elif node.access_mode == ACCESS_MODE.RECURSIVE:
+ return True
+ else:
+ node = node.map.get(component)
+ if node is None:
+ return False
+
+ return self._check_final_node(node)
+
+ def _check_final_node(self, node: Union[Dir, File]) -> bool:
+ return isinstance(node, File) or node.access_mode != ACCESS_MODE.NONE

dmoj/executors/java_executor.py

@@ -12,6 +12,7 @@
 from dmoj.executors.mixins import SingleDigitVersionMixin
 from dmoj.judgeenv import skip_self_test
 from dmoj.utils.unicode import utf8bytes, utf8text
+from dmoj.executors.filesystem_policies import ExactFile, ExactDir
 
 recomment = re.compile(r'/\*.*?\*/', re.DOTALL | re.U)
 restring = re.compile(r''''(?:\\.|[^'\\])'|"(?:\\.|[^"\\])*"''', re.DOTALL | re.U)
@@ -82,11 +83,11 @@ def get_executable(self):
  return self.get_vm()
 
  def get_fs(self):
- return super().get_fs() + [f'{re.escape(self._agent_file)}$'] + \
- [f'{re.escape(str(parent))}$' for parent in PurePath(self._agent_file).parents]
+ return super().get_fs() + [ExactFile(self._agent_file)] + \
+ [ExactDir(str(parent)) for parent in PurePath(self._agent_file).parents]
 
  def get_write_fs(self):
- return super().get_write_fs() + [os.path.join(self._dir, 'submission_jvm_crash.log')]
+ return super().get_write_fs() + [ExactFile(os.path.join(self._dir, 'submission_jvm_crash.log'))]
 
  def get_agent_flag(self):
  agent_flag = '-javaagent:%s=policy:%s' % (self._agent_file, self._policy_file)