pwnlib.tubes.process — Processes

class pwnlib.tubes.process.process(argv=None, shell=False, executable=None, cwd=None, env=None, stdin=-1, stdout=<pwnlib.tubes.process.PTY object>, stderr=-2, close_fds=True, preexec_fn=<function process.<lambda>>, raw=True, aslr=None, setuid=None, where='local', display=None, alarm=None, *args, **kwargs)

Bases: tube

Spawns a new process, and wraps it with a tube for communication.

Parameters

• argv (list) – List of arguments to pass to the spawned process.

• shell (bool) – Set to True to interpret argv as a string to pass to the shell for interpretation instead of as argv.

• executable (str) – Path to the binary to execute. If None, uses argv[0]. Cannot be used with shell.

• cwd (str) – Working directory. Uses the current working directory by default.

• env (dict) – Environment variables. By default, inherits from Python’s environment.

• stdin (int) – File object or file descriptor number to use for stdin. By default, a pipe is used. A pty can be used instead by setting this to PTY. This will cause programs to behave in an interactive manner (e.g.., python will show a >>> prompt). If the application reads from /dev/tty directly, use a pty.

• stdout (int) – File object or file descriptor number to use for stdout. By default, a pty is used so that any stdout buffering by libc routines is disabled. May also be PIPE to use a normal pipe.

• stderr (int) – File object or file descriptor number to use for stderr. By default, STDOUT is used. May also be PIPE to use a separate pipe, although the pwnlib.tubes.tube.tube wrapper will not be able to read this data.

• close_fds (bool) – Close all open file descriptors except stdin, stdout, stderr. By default, True is used.

• preexec_fn (callable) – Callable to invoke immediately before calling execve.

• raw (bool) – Set the created pty to raw mode (i.e. disable echo and control characters). True by default. If no pty is created, this has no effect.

• aslr (bool) –

  If set to False, disable ASLR via personality (setarch -R) and setrlimit (ulimit -s unlimited).

  This disables ASLR for the target process. However, the setarch changes are lost if a setuid binary is executed.

  The default value is inherited from context.aslr. See setuid below for additional options and information.

• setuid (bool) –

  Used to control setuid status of the target binary, and the corresponding actions taken.

  By default, this value is None, so no assumptions are made.

  If True, treat the target binary as setuid. This modifies the mechanisms used to disable ASLR on the process if aslr=False. This is useful for debugging locally, when the exploit is a setuid binary.

  If False, prevent setuid bits from taking effect on the target binary. This is only supported on Linux, with kernels v3.5 or greater.

• where (str) – Where the process is running, used for logging purposes.

• display (list) – List of arguments to display, instead of the main executable name.

• alarm (int) – Set a SIGALRM alarm timeout on the process.

Examples

>>> p = process('python')
>>> p.sendline(b"print('Hello world')")
>>> p.sendline(b"print('Wow, such data')")
>>> b'' == p.recv(timeout=0.01)
True
>>> p.shutdown('send')
>>> p.proc.stdin.closed
True
>>> p.connected('send')
False
>>> p.recvline()
b'Hello world\n'
>>> p.recvuntil(b',')
b'Wow,'
>>> p.recvregex(b'.*data')
b' such data'
>>> p.recv()
b'\n'
>>> p.recv() 
Traceback (most recent call last):
...
EOFError

>>> p = process('cat')
>>> d = open('/dev/urandom', 'rb').read(4096)
>>> p.recv(timeout=0.1)
b''
>>> p.write(d)
>>> p.recvrepeat(0.1) == d
True
>>> p.recv(timeout=0.1)
b''
>>> p.shutdown('send')
>>> p.wait_for_close()
>>> p.poll()
0

>>> p = process('cat /dev/zero | head -c8', shell=True, stderr=open('/dev/null', 'w+b'))
>>> p.recv()
b'\x00\x00\x00\x00\x00\x00\x00\x00'

>>> p = process(['python','-c','import os; print(os.read(2,1024).decode())'],
...             preexec_fn = lambda: os.dup2(0,2))
>>> p.sendline(b'hello')
>>> p.recvline()
b'hello\n'

>>> stack_smashing = ['python','-c','open("/dev/tty","wb").write(b"stack smashing detected")']
>>> process(stack_smashing).recvall()
b'stack smashing detected'

>>> process(stack_smashing, stdout=PIPE).recvall()
b''

>>> getpass = ['python','-c','import getpass; print(getpass.getpass("XXX"))']
>>> p = process(getpass, stdin=PTY)
>>> p.recv()
b'XXX'
>>> p.sendline(b'hunter2')
>>> p.recvall()
b'\nhunter2\n'

>>> process('echo hello 1>&2', shell=True).recvall()
b'hello\n'

>>> process('echo hello 1>&2', shell=True, stderr=PIPE).recvall()
b''

>>> a = process(['cat', '/proc/self/maps']).recvall()
>>> b = process(['cat', '/proc/self/maps'], aslr=False).recvall()
>>> with context.local(aslr=False):
...    c = process(['cat', '/proc/self/maps']).recvall()
>>> a == b
False
>>> b == c
True

>>> process(['sh','-c','ulimit -s'], aslr=0).recvline()
b'unlimited\n'

>>> io = process(['sh','-c','sleep 10; exit 7'], alarm=2)
>>> io.poll(block=True) == -signal.SIGALRM
True

>>> binary = ELF.from_assembly('nop', arch='mips')
>>> p = process(binary.path)
>>> binary_dir, binary_name = os.path.split(binary.path)
>>> p = process('./{}'.format(binary_name), cwd=binary_dir)
>>> p = process(binary.path, cwd=binary_dir)
>>> p = process('./{}'.format(binary_name), cwd=os.path.relpath(binary_dir))
>>> p = process(binary.path, cwd=os.path.relpath(binary_dir))

__getattr__(attr)

Permit pass-through access to the underlying process object for fields like pid and stdin.

__init__(argv=None, shell=False, executable=None, cwd=None, env=None, stdin=-1, stdout=<pwnlib.tubes.process.PTY object>, stderr=-2, close_fds=True, preexec_fn=<function process.<lambda>>, raw=True, aslr=None, setuid=None, where='local', display=None, alarm=None, *args, **kwargs)

__on_enoexec(exception)

We received an ‘exec format’ error (ENOEXEC)

This implies that the user tried to execute e.g. an ARM binary on a non-ARM system, and does not have binfmt helpers installed for QEMU.

__preexec_fn()

Routine executed in the child process before invoking execve().

Handles setting the controlling TTY as well as invoking the user- supplied preexec_fn.

__pty_make_controlling_tty(tty_fd)

This makes the pseudo-terminal the controlling tty. This should be more portable than the pty.fork() function. Specifically, this should work on Solaris.

_validate(cwd, executable, argv, env)

Perform extended validation on the executable path, argv, and envp.

Mostly to make Python happy, but also to prevent common pitfalls.

can_recv_raw(timeout) → bool

Should not be called directly. Returns True, if there is data available within the timeout, but ignores the buffer on the object.

close()

Closes the tube.

communicate(stdin=None) → str

Calls subprocess.Popen.communicate() method on the process.

connected_raw(direction)

connected(direction = ‘any’) -> bool

Should not be called directly. Returns True iff the tube is connected in the given direction.

fileno() → int

Returns the file number used for reading.

kill()

Kills the process.

leak(address, count=1)

Leaks memory within the process at the specified address.

Parameters

• address (int) – Address to leak memory at

• count (int) – Number of bytes to leak at that address.

Example

>>> e = ELF(which('bash-static'))
>>> p = process(e.path)

In order to make sure there’s not a race condition against the process getting set up…

>>> p.sendline(b'echo hello')
>>> p.recvuntil(b'hello')
b'hello'

Now we can leak some data!

>>> p.leak(e.address, 4)
b'\x7fELF'

libs() → dict

Return a dictionary mapping the path of each shared library loaded by the process to the address it is loaded at in the process’ address space.

poll(block=False) → int

Parameters

block (bool) – Wait for the process to exit

Poll the exit code of the process. Will return None, if the process has not yet finished and the exit code otherwise.

readmem(address, count=1)

Leaks memory within the process at the specified address.

Parameters

• address (int) – Address to leak memory at

• count (int) – Number of bytes to leak at that address.

Example

>>> e = ELF(which('bash-static'))
>>> p = process(e.path)

In order to make sure there’s not a race condition against the process getting set up…

>>> p.sendline(b'echo hello')
>>> p.recvuntil(b'hello')
b'hello'

Now we can leak some data!

>>> p.leak(e.address, 4)
b'\x7fELF'

recv_raw(numb) → str

Should not be called directly. Receives data without using the buffer on the object.

Unless there is a timeout or closed connection, this should always return data. In case of a timeout, it should return None, in case of a closed connection it should raise an exceptions.EOFError.

send_raw(data)

Should not be called directly. Sends data to the tube.

Should return exceptions.EOFError, if it is unable to send any more, because of a close tube.

settimeout_raw(timeout)

Should not be called directly. Sets the timeout for the tube.

shutdown_raw(direction)

Should not be called directly. Closes the tube for further reading or writing.

writemem(address, data)

Writes memory within the process at the specified address.

Parameters

• address (int) – Address to write memory

• data (bytes) – Data to write to the address

Example

Let’s write data to the beginning of the mapped memory of the ELF.

>>> context.clear(arch='i386')
>>> address = 0x100000
>>> data = cyclic(32)
>>> assembly = shellcraft.nop() * len(data)

Wait for one byte of input, then write the data to stdout

>>> assembly += shellcraft.write(1, address, 1)
>>> assembly += shellcraft.read(0, 'esp', 1)
>>> assembly += shellcraft.write(1, address, 32)
>>> assembly += shellcraft.exit()
>>> asm(assembly)[32:]
b'j\x01[\xb9\xff\xff\xef\xff\xf7\xd1\x89\xdaj\x04X\xcd\x801\xdb\x89\xe1j\x01Zj\x03X\xcd\x80j\x01[\xb9\xff\xff\xef\xff\xf7\xd1j Zj\x04X\xcd\x801\xdbj\x01X\xcd\x80'

Assemble the binary and test it

>>> elf = ELF.from_assembly(assembly, vma=address)
>>> io = elf.process()
>>> _ = io.recvuntil(b'\x90')
>>> _ = io.writemem(address, data)
>>> io.send(b'X')
>>> io.recvall()
b'aaaabaaacaaadaaaeaaafaaagaaahaaa'

_setuid

Whether setuid is permitted

_stop_noticed = 0

Have we seen the process stop? If so, this is a unix timestamp.

alarm

Alarm timeout of the process

argv

Arguments passed on argv

aslr

Whether ASLR should be left on

property corefile

Returns a corefile for the process.

If the process is alive, attempts to create a coredump with GDB.

If the process is dead, attempts to locate the coredump created by the kernel.

property cwd

Directory that the process is working in.

Example

>>> p = process('sh')
>>> p.sendline(b'cd /tmp; echo AAA')
>>> _ = p.recvuntil(b'AAA')
>>> p.cwd == '/tmp'
True
>>> p.sendline(b'cd /proc; echo BBB;')
>>> _ = p.recvuntil(b'BBB')
>>> p.cwd
'/proc'

property elf

Returns an ELF file for the executable that launched the process.

env

Environment passed on envp

executable

Full path to the executable

property libc

Returns an ELF for the libc for the current process. If possible, it is adjusted to the correct address automatically.

Example:

>>> p = process("/bin/cat")
>>> libc = p.libc
>>> libc 
ELF('/lib64/libc-...so')
>>> p.close()

proc = None

subprocess.Popen object that backs this process

property program

Alias for executable, for backward compatibility.

Example

>>> p = process('/bin/true')
>>> p.executable == '/bin/true'
True
>>> p.executable == p.program
True

pty

Which file descriptor is the controlling TTY

raw

Whether the controlling TTY is set to raw mode

property stderr

Shorthand for self.proc.stderr

See: process.proc

property stdin

Shorthand for self.proc.stdin

See: process.proc

property stdout

Shorthand for self.proc.stdout

See: process.proc