pwnypack.flow – Communication

The Flow module lets you connect to processes or network services using a unified API. It is primarily designed for synchronous communication flows.

It is based around the central Flow class which uses a Channel to connect to a process. The Flow class then uses the primitives exposed by the Channel to provide a high level API for reading/receiving and writing/sending data.

Examples

>>> from pwny import *
>>> f = Flow.connect_tcp('ced.pwned.systems', 80)
>>> f.writelines([
...     b'GET / HTTP/1.0',
...     b'Host: ced.pwned.systems',
...     b'',
... ])
>>> line = f.readline().strip()
>>> print(line == b'HTTP/1.0 200 OK')
True
>>> f.until(b'\r\n\r\n')
>>> f.read_eof(echo=True)
... lots of html ...

>>> from pwny import *
>>> f = Flow.execute('cat')
>>> f.writeline(b'hello')
>>> f.readline(echo=True)
class pwnypack.flow.ProcessChannel(executable, argument..., redirect_stderr=False)

Bases: object

This channel type allows controlling processes. It uses python’s subprocess.Popen class to execute a process and allows you to communicate with it.

Parameters:
  • executable (str) – The executable to start.
  • argument... (list of str) – The arguments to pass to the executable.
  • redirect_stderr (bool) – Whether to also capture the output of stderr.
close()

Wait for the subprocess to exit.

kill()

Terminate the subprocess.

read(n)

Read n bytes from the subprocess’ output channel.

Parameters:n (int) – The number of bytes to read.
Returns:n bytes of output.
Return type:bytes
Raises:EOFError – If the process exited.
write(data)

Write n bytes to the subprocess’ input channel.

Parameters:data (bytes) – The data to write.
Raises:EOFError – If the process exited.
class pwnypack.flow.SocketChannel(sock)

Bases: object

This channel type allows controlling sockets.

Parameters:socket (socket.socket) – The (already connected) socket to control.
close()

Close the socket gracefully.

kill()

Shut down the socket immediately.

read(n)

Receive n bytes from the socket.

Parameters:n (int) – The number of bytes to read.
Returns:n bytes read from the socket.
Return type:bytes
Raises:EOFError – If the socket was closed.
write(data)

Send n bytes to socket.

Parameters:data (bytes) – The data to send.
Raises:EOFError – If the socket was closed.
class pwnypack.flow.TCPSocketChannel(host, port)

Bases: pwnypack.flow.SocketChannel

Convenience subclass of SocketChannel that allows you to connect to a TCP hostname / port pair easily.

Parameters:
  • host (str) – The hostname or IP address to connect to.
  • port (int) – The port number to connect to.
class pwnypack.flow.Flow(channel, echo=False)

Bases: object

The core class of Flow. Takes a channel and exposes synchronous utility functions for communications.

Usually, you’ll use the convenience classmethods connect_tcp() or execute() instead of manually creating the constructor directly.

Parameters:
  • channel (Channel) – A channel.
  • echo (bool) – Whether or not to echo all input / output.
close()

Gracefully close the channel.

classmethod connect_tcp(host, port, echo=False)

Set up a TCPSocketChannel and create a Flow instance for it.

Parameters:
  • host (str) – The hostname or IP address to connect to.
  • port (int) – The port number to connect to.
  • echo (bool) – Whether to echo read/written data to stdout by default.
Returns:

Flow: A Flow instance initialised with the TCP socket channel.
Return type:

:class
classmethod execute(executable, *arguments, **kwargs)

execute(executable, argument..., redirect_stderr=False, echo=False):

Set up a ProcessChannel and create a Flow instance for it.

Parameters:
  • executable (str) – The executable to start.
  • argument... (list of str) – The arguments to pass to the executable.
  • redirect_stderr (bool) – Whether to also capture the output of stderr.
  • echo (bool) – Whether to echo read/written data to stdout by default.
Returns:

Flow: A Flow instance initialised with the process channel.
Return type:

:class
kill()

Terminate the channel immediately.

read(n, echo=None)

Read n bytes from the channel.

Parameters:
  • n (int) – The number of bytes to read from the channel.
  • echo (bool) – Whether to write the read data to stdout.
Returns:

n bytes of data.
Return type:

bytes
Raises:

EOFError – If the channel was closed.
read_eof(echo=None)

Read until the channel is closed.

Parameters:echo (bool) – Whether to write the read data to stdout.
Returns:The read data.
Return type:bytes
read_until(s, echo=None)

Read until a certain string is encountered..

Parameters:
  • s (bytes) – The string to wait for.
  • echo (bool) – Whether to write the read data to stdout.
Returns:

The data up to and including s.
Return type:

bytes
Raises:

EOFError – If the channel was closed.
readline(echo=None)

Read 1 line from channel.

Parameters:echo (bool) – Whether to write the read data to stdout.
Returns:The read line which includes new line character.
Return type:bytes
Raises:EOFError – If the channel was closed before a line was read.
readlines(n, echo=None)

Read n lines from channel.

Parameters:
  • n (int) – The number of lines to read.
  • echo (bool) – Whether to write the read data to stdout.
Returns:

n lines which include new line characters.
Return type:

list of bytes
Raises:

EOFError – If the channel was closed before n lines were read.
until(s, echo=None)

Read until a certain string is encountered..

Parameters:
  • s (bytes) – The string to wait for.
  • echo (bool) – Whether to write the read data to stdout.
Returns:

The data up to and including s.
Return type:

bytes
Raises:

EOFError – If the channel was closed.
write(data, echo=None)

Write data to channel.

Parameters:
  • data (bytes) – The data to write to the channel.
  • echo (bool) – Whether to echo the written data to stdout.
Raises:

EOFError – If the channel was closed before all data was sent.
writeline(line=b'', echo=None)

Write a byte sequences to the channel and terminate it with carriage return and line feed.

Parameters:
  • line (bytes) – The line to send.
  • echo (bool) – Whether to echo the written data to stdout.
Raises:

EOFError – If the channel was closed before all data was sent.
writelines(lines, echo=None)

Write a list of byte sequences to the channel and terminate them with carriage return and line feed.

Parameters:
  • lines (list of bytes) – The lines to send.
  • echo (bool) – Whether to echo the written data to stdout.
Raises:

EOFError – If the channel was closed before all data was sent.