diff options
| -rw-r--r-- | sandboxlib/__init__.py | 105 | ||||
| -rw-r--r-- | sandboxlib/chroot.py | 22 | ||||
| -rw-r--r-- | sandboxlib/linux_user_chroot.py | 11 |
3 files changed, 96 insertions, 42 deletions
diff --git a/sandboxlib/__init__.py b/sandboxlib/__init__.py index 3aeaf1c..d620777 100644 --- a/sandboxlib/__init__.py +++ b/sandboxlib/__init__.py @@ -23,6 +23,7 @@ docstrings that describe the different parameters. import logging +import os import platform import shutil import subprocess @@ -58,8 +59,20 @@ def maximum_possible_isolation(): raise NotImplementedError() -def run_sandbox(rootfs_path, command, cwd=None, extra_env=None, - network='undefined'): + +# Special value for 'stderr' and 'stdout' parameters to indicate 'capture +# and return the data'. +CAPTURE = subprocess.PIPE + +# Special value for 'stderr' parameter to indicate 'forward to stdout'. +STDOUT = subprocess.STDOUT + + +def run_sandbox(command, cwd=None, extra_env=None, + filesystem_root='/', filesystem_writable_paths='all', + mounts='undefined', extra_mounts=None, + network='undefined', + stderr=CAPTURE, stdout=CAPTURE): '''Run 'command' in a sandboxed environment. Parameters: @@ -89,29 +102,28 @@ def run_sandbox(rootfs_path, command, cwd=None, extra_env=None, no attempt is made to either prevent or provide networking inside the sandbox. Backends may support 'isolated' and/or other values as well. + - stdout: whether to capture stdout, or redirect stdout to a file handle. + If set to sandboxlib.CAPTURE, the function will return the stdout + data, if not, it will return None for that. If stdout=None, the + data will be discarded -- it will NOT inherit the parent process's + stdout, unlike with subprocess.Popen(). Set 'stdout=sys.stdout' if + you want that. + - stderr: same as stdout + + Returns: + a tuple of (exit code, stdout output, stderr output). ''' raise NotImplementedError() -def Popen(command, stderr=None, stdout=None, **sandbox_config): - '''Start a subprocess in a sandbox and return straight away. +def run_sandbox_with_redirection(command, **sandbox_config): + '''Start a subprocess in a sandbox, redirecting stderr and/or stdout. - This function aims to function like subprocess.Popen(), but with the - subprocess running inside a sandbox. It returns a subprocess.Popen - instance as soon as 'command' starts executing. + The sandbox_config arguments are the same as the run_command() function. - The 'stderr' and 'stdout' parameters accept None, a file-like object, a - file descriptor (integer), or subprocess.PIPE. The only difference from - the subprocess.Popen() function is that 'None' means 'ignore all output' - rather than 'inherit parent's stdout': if you want to forward output from - the subprocess to stdout, you must pass `stdout=sys.stdout`. - - The sandbox_config arguments are the same as the run_command() function. In - most cases you should use run_command() instead of this, but there are - certain cases where Popen() could be useful. The run_command() function - buffers all data from stdout and stderr of the subprocess in memory, which - is impractical if there is a huge amount of data. + This returns just the exit code, because if stdout or stderr are redirected + those values will be None in any case. ''' raise NotImplementedError() @@ -205,26 +217,51 @@ def validate_extra_mounts(extra_mounts): return new_extra_mounts -def _run_command(argv, cwd=None, env=None, preexec_fn=None): +def _run_command(argv, stdout, stderr, cwd=None, env=None): '''Wrapper around subprocess.Popen() with common settings. - This function blocks until the subprocesses has terminated. It then - returns a tuple of (exit code, stdout output, stderr output). + This function blocks until the subprocess has terminated. + + Unlike the subprocess.Popen() function, if stdout or stderr are None then + output is discarded. + + It then returns a tuple of (exit code, stdout output, stderr output). + If stdout was not equal to subprocess.PIPE, stdout will be None. Same for + stderr. ''' - process = subprocess.Popen( - argv, - # The default is to share file descriptors from the parent process - # to the subprocess, which is rarely good for sandboxing. - close_fds=True, - cwd=cwd, - env=env, - preexec_fn=preexec_fn, - stdout=subprocess.PIPE, - stderr=subprocess.PIPE - ) - process.wait() - return process.returncode, process.stdout.read(), process.stderr.read() + if stdout is None or stderr is None: + dev_null = open(os.devnull, 'w') + stdout = stdout or dev_null + stderr = stderr or dev_null + else: + dev_null = None + + try: + process = subprocess.Popen( + argv, + # The default is to share file descriptors from the parent process + # to the subprocess, which is rarely good for sandboxing. + close_fds=True, + cwd=cwd, + env=env, + stdout=stdout, + stderr=stderr, + ) + + # The 'out' variable will be None unless subprocess.PIPE was passed as + # 'stdout' to subprocess.Popen(). Same for 'err' and 'stderr'. If + # subprocess.PIPE wasn't passed for either it'd be safe to use .wait() + # instead of .communicate(), but if they were then we must use + # .communicate() to avoid blocking the subprocess if one of the pipes + # becomes full. It's safe to use .communicate() in all cases. + + out, err = process.communicate() + finally: + if dev_null is not None: + dev_null.close() + + return process.returncode, out, err # Executors diff --git a/sandboxlib/chroot.py b/sandboxlib/chroot.py index 530e667..97391de 100644 --- a/sandboxlib/chroot.py +++ b/sandboxlib/chroot.py @@ -87,7 +87,7 @@ def mount(source, path, mount_type, mount_options): # should do that instead. argv = [ 'mount', '-t', mount_type, '-o', mount_options, source, path] - exit, out, err = sandboxlib._run_command(argv) + exit, out, err = sandboxlib._run_command(argv, stdout=None, stderr=None) if exit != 0: raise RuntimeError( @@ -97,7 +97,7 @@ def mount(source, path, mount_type, mount_options): def unmount(path): argv = ['umount', path] - exit, out, err = sandboxlib._run_command(argv) + exit, out, err = sandboxlib._run_command(argv, stdout=None, stderr=None) if exit != 0: warnings.warn("%s failed: %s" % ( @@ -127,7 +127,8 @@ def mount_all(rootfs_path, mount_info_list): unmount(mountpoint) -def run_command_in_chroot(pipe, extra_mounts, chroot_path, command, cwd, env): +def run_command_in_chroot(pipe, stdout, stderr, extra_mounts, chroot_path, + command, cwd, env): # This function should be run in a multiprocessing.Process() subprocess, # because it calls os.chroot(). There's no 'unchroot()' function! After # chrooting, it calls sandboxlib._run_command(), which uses the @@ -157,7 +158,8 @@ def run_command_in_chroot(pipe, extra_mounts, chroot_path, command, cwd, env): raise RuntimeError( "Unable to set current working directory: %s" % e) - exit, out, err = sandboxlib._run_command(command, env=env) + exit, out, err = sandboxlib._run_command( + command, stdout, stderr, env=env) pipe.send([exit, out, err]) result = 0 except Exception as e: @@ -169,7 +171,8 @@ def run_command_in_chroot(pipe, extra_mounts, chroot_path, command, cwd, env): def run_sandbox(command, cwd=None, extra_env=None, filesystem_root='/', filesystem_writable_paths='all', mounts='undefined', extra_mounts=None, - network='undefined'): + network='undefined', + stdout=sandboxlib.CAPTURE, stderr=sandboxlib.CAPTURE): if type(command) == str: command = [command] @@ -186,7 +189,8 @@ def run_sandbox(command, cwd=None, extra_env=None, with mount_all(filesystem_root, extra_mounts): process = multiprocessing.Process( target=run_command_in_chroot, - args=(pipe_child, extra_mounts, filesystem_root, command, cwd, env)) + args=(pipe_child, stdout, stderr, extra_mounts, filesystem_root, + command, cwd, env)) process.start() process.join() @@ -198,3 +202,9 @@ def run_sandbox(command, cwd=None, extra_env=None, # will be within the _run_command_in_chroot() function somewhere. exception = pipe_parent.recv() raise exception + + +def run_sandbox_with_redirection(command, **sandbox_config): + exit, out, err = run_sandbox(command, **sandbox_config) + # out and err will be None + return exit diff --git a/sandboxlib/linux_user_chroot.py b/sandboxlib/linux_user_chroot.py index c0715c7..4244d99 100644 --- a/sandboxlib/linux_user_chroot.py +++ b/sandboxlib/linux_user_chroot.py @@ -262,7 +262,8 @@ def process_writable_paths(fs_root, writable_paths): def run_sandbox(command, cwd=None, extra_env=None, filesystem_root='/', filesystem_writable_paths='all', mounts='undefined', extra_mounts=None, - network='undefined'): + network='undefined', + stdout=sandboxlib.CAPTURE, stderr=sandboxlib.CAPTURE): if type(command) == str: command = [command] @@ -284,5 +285,11 @@ def run_sandbox(command, cwd=None, extra_env=None, env = sandboxlib.environment_vars(extra_env) argv = (unshare_command + linux_user_chroot_command + command) - exit, out, err = sandboxlib._run_command(argv, env=env) + exit, out, err = sandboxlib._run_command(argv, stdout, stderr, env=env) return exit, out, err + + +def run_sandbox_with_redirection(command, **sandbox_config): + exit, out, err = run_sandbox(command, **sandbox_config) + # out and err will be None + return exit |