Hi I have a problem that I cannot seem to find any solution for.
(Maybe i'm just horrible at phrasing searches correctly in english)
I'm trying to execute a binary from python using pwntools and reading its output completely before sending some input myself.
The output from my binary is as follows:
Testmessage1
Testmessage2
Enter input: <binary expects me to input stuff here>
Where I would like to read the first line, the second line and the output part of the third line (with ':' being the last character).
The third line of the output does not contain a newline at the end and expects the user to make an input directly. However, I'm not able to read the output contents that the third line starts with, no matter what I try.
My current way of trying to achieve this:
from pwn import *
io = process("./testbin")
print io.recvline()
print io.recvline()
print io.recvuntil(":", timeout=1) # this get's stuck if I dont use a timeout
...
# maybe sending data here
# io.send(....)
io.close()
Do I missunderstand something about stdin and stdout? Is "Enter input:" of the third line not part of the output that I should be able to receive before making an input?
Thanks in advance
I finally figured it out.
I got the hint I needed from
https://github.com/zachriggle/pwntools-glibc-buffering/blob/master/demo.py
It seems that Ubuntu is doing lots of buffering on its own.
When manually making sure that pwnTools uses a pseudoterminal for stdin and stdout it works!
import * from pwn
pty = process.PTY
p = process(stdin=pty, stdout=pty)
You can use the clean function which is more reliable and which can be used for remote connections: https://docs.pwntools.com/en/dev/tubes.html#pwnlib.tubes.tube.tube.clean
For example:
def start():
p = remote("0.0.0.0", 4000)
return p
io = start()
io.send(b"YYYY")
io.clean()
io.send(b"ZZZ")
Related
I'm trying to figure out how to use subprocess.
I want to sub-run a program, and get its output, within a main program using some data from the main program.
I know subprocessing is not the optimal solution but separating both programs is mendatory for this project.
So I tried a realy simple trial with 2 files :
the main one, named test_p1.py:
import subprocess
output = subprocess.check_output('test_p2.py',shell=True,text=True,input='4')
#I need shell=True for my project
print(output)
the second one, named test_p2 :
import sys
print(sys.stdin.read())
When I run this I expected to get my input back, but it is not working (nothing is printed).
I did a previous test where the second file is a simple print of a str, unrelated to sys.stdin and it worked fine.
So I guess the problem is either with the input or with sys.stdin.read()
Please help me :)
Edit:
I tried to convert test_p2.py to an executable as suggested but it did not work.
Edit 2 :
I also tried to use subprocess.run() instead of subprocess.checkoutput() in test_p1.py and to replace sys.stdin.read() by input() in test_p2.py.
This is test_p1.py
import subprocess
output = subprocess.run('test_p2.py',shell=True,check=True,input='please help\n',encoding="utf-8",text=True).stdout
print(output)
and this is test_p2.py
a=input()
print(a)
print('input worked')
but nothing is printed when I subprocess part 2 within part 1.
I don't understand How I can simply send info to a file I subprocess.
This question already has answers here:
How do I read from stdin?
(25 answers)
Closed 6 years ago.
I am doing small project in which I have to read the file from STDIN.
I am not sure what it means, what I asked the professor he told me,
there is not need to open the file and close like we generally do.
sFile = open ( "file.txt",'r')
I dont have to pass the file as a argument.
I am kind of confused what he wants.
The stdin takes input from different sources - depending on what input it gets.
Given a very simple bit of code for illustration (let's call it: script.py):
import sys
text = sys.stdin.read()
print text
You can either pipe your script with the input-file like so:
$ more file.txt | script.py
In this case, the output of the first part of the pipeline - which is the content of the file - is assigned to our variable(in this case text, which gets printed out eventually).
When left empty (i.e. without any additional input) like so:
$ python script.py
It let's you write the input similar to the input function and assigns the written input to the defined variable(Note that this input-"window" is open until you explicitly close it, which is usually done with Ctrl+D).
import sys, then sys.stdin will be the 'file' you want which you can use like any other file (e.g. sys.stdin.read()), and you don't have to close it. stdin means "standard input".
Might be helpful if you read through this post, which seems to be similar to yours.
'stdin' in this case would be the argument on the command line coming after the python script, so python script.py input_file. This input_file would be the file containing whatever data you are working on.
So, you're probably wondering how to read stdin. There are a couple of options. The one suggested in the thread linked above goes as follows:
import fileinput
for line in fileinput.input():
#read data from file
There are other ways, of course, but I think I'll leave you to it. Check the linked post for more information.
Depending on the context of your assignment, stdin may be automatically sent into the script, or you may have to do it manually as detailed above.
I'm new to Python and using Pycharm to work with code.
I'm writing a simple program, that read string and then convert it into int.
import sys
print ("Hello word")
data = sys.stdin.read()
tokens = data.split()
for i in range(len(tokens)):
tokens[i] = int(tokens[i])
print (tokens[1])
I ran program, entered three numbers, but that's all
Why, while running the program I can't see the results of print?
It's because the program is still reading from stdin. To read only one line from stdin, you have to use stdin.readline(). If you run a debug process with a breakpoint after the line sys.stdin.read(), you'll see that the program never reaches it. Running your program in Ideone, for example, where it lets you specify stdin before running your app, stdin.read() works fine. Usually it reads until EOF (end of file). So, either use sys.stdin.readline() (built-in input() does just that), or use file input if you want to read multiple lines. You can also refer to this post for more info if you really want to use sys.stdin.read().
You have effectively blocked the program with .read(); its a lot simpler to use input(), like this:
print('Hello World')
data = input()
tokens = map(int, data.split()) # this converts to int
print(tokens[1])
I have a script which executes some command using os.popen4. Problem is some time command being executed will require user input ("y" or "n"). I am reading stdout/stderr and printing it, but it seems question from command doesn't got printed and it hangs. To make it work, i had to write "n" to stdin blindly. Can some one please guide on how to handle it?
Code not working:
(f_p_stdin, f_p_stdout_stderr) = os.popen4(cmd_exec,"t")
cmd_out = f_p_stdout_stderr.readlines()
print cmd_out
f_p_stdin.write("n")
f_p_stdin.close()
f_p_stdout_stderr.close()
Working Code:
(f_p_stdin, f_p_stdout_stderr) = os.popen4(cmd_exec,"t")
cmd_out = f_p_stdout_stderr.readlines()
f_p_stdin.write("n")
f_p_stdin.close()
print cmd_out
f_p_stdout_stderr.close()
NOTE : I am aware that it is depreciated and subprocess module is used, but right now i don't know on how to use it. So i'll appreciate if some one will help me to handle it using os.popen4. I want to capture the question and handle the input from user and execute it.
readlines() : returns a list containing all the lines of data in the file. If reading from a process like in this case, there is a good chance it does not send a newline and/or flush the output. You should read characters from the input and process that to see if the question was posed.
It would help to know what cmd_exec looks like, so others can try and emulate what you tried.
Update:
I wrote a uncheckout command in Python:
#! /usr/bin/env python
# coding: utf-8
import sys
print 'Uncheckout of {} is irreversible'.format(sys.argv[1])
print 'Do you want to proceed? [y/N]',
sys.stdout.flush()
x = raw_input()
if x == 'y':
print sys.argv[1], "no longer checked out"
else:
print sys.argv[1], "still checked out"
I put the prompt string on purpose not as argument to raw_input, to be able to do the flush() explicitly.
Neither of your code snippets work with that (assuming cmd_exec to be ['./uncheckout', 'abc.txt'] or './uncheckout abc.txt', popen4() uses the shell in the latter case to start the program).
Only when I move the readlines() until after the write() and close() will the command continue.
That makes sense to me as the close() flushes the output. You are writing in text mode and that buffers normally until end-of-line, which is not in your .write('n').
To be able to check what the prompt is and test and react on that., the following works with the above uncheckout:
#! /usr/bin/env python
# coding: utf-8
import os
import sys
cmd_exec = ['./uncheckout', 'abc.txt']
(f_p_stdin, f_p_stdout_stderr) = os.popen4(cmd_exec,"t")
line = ''
while True:
x = f_p_stdout_stderr.read(1)
if not x:
break
sys.stdout.write(x)
sys.stdout.flush()
if x == '\n':
line = ''
else:
line += x
if line.endswith('[y/N]'):
f_p_stdin.write("n\n")
f_p_stdin.flush()
sys.stdout.write('\n')
Maybe you can work backwards from that to make something that works for you. Make sure to keep flushes at appropriate places.
I am using pexpect with python to create a program that allows a user to interact with a FORTRAN program through a website. From the FORTRAN program I am receive the error:
open: Permission denied apparent state: unit 4 named subsat.out.55 last format: list io lately writing sequential formatted external IO 55
when I attempt to:
p = pexpect.spawn(myFortranProgram,[],5)
p.logfile_read = sys.stdout
p.expect("(.*)")
p.sendline("55")
From what I understand, I am likely sending the 55 to the wrong input unit. How do I correctly send input to a FORTRAN program using pexpect in Python?
Thank You.
Edit: When p.sendline's parameter is empty (e.g. p.sendline()) or only contains spaces, the program proceeds as expected. In sending non-space values to a FORTRAN program, do I need to specify the input format somehow?
The pexpect module is something I'd not used before, but could be useful to me, so I tried this.
Edit:
I've not been able to duplicate the error you're reporting. Looking at this error leads me to believe that it has something to do with reading from a file, which may be a result of other issues. From what I've seen, this isn't what pexpect is designed to handle directly; however, you may be able to make it work with a pipe, like the example in my original answer, below.
I'm having no problem sending data to Fortran's I/O stream 5 (stdin). I created a Fortran program called regurgitate which issues a " Your entry? " prompt, then gets a line of input from the user on I/O stream 5, then prints it back out. The following code works with that program:
import pexpect
child = pexpect.spawn('./regurgitate')
child.setecho(False)
ndx = child.expect('.*Your entry?.*')
child.sendline('42')
child.expect([pexpect.EOF])
print child.before
child.close()
The output is simply:
42
Exactly what I expected. However, if my Fortran program says something different (such as "Your input?"), the pexpect just hangs or times out.
Original suggestion:
Maybe this pexpect.run() sample will help you. At least it seems to run my regurgitate program (a simple Fortran program that accepts an input and then prints it out):
import pexpect
out = pexpect.run('/bin/bash -c "/bin/cat forty-two | ./regurgitate"')
print out
The output was:
Your entry?
42
Where regurgitate prints out a "Your entry?" prompt and the forty-two file contains "42" (without quotes in both cases).