python3 pexpect strange behaviour - python-3.x

Question

I have a single threaded program that simply executes commands over ssh and simply looks for output over ssh. But after a while I start getting extrodinarily strange behaviour:
ssh_cmd = 'ssh %s#%s %s' % (user, addr, options)
ssh = pexpect.spawn(ssh_cmd, timeout=60)
lgsuc = ['(?i)(password)')]
for item in loginsuccess:
lgsuc.append(item)
retval = ssh.expect(lgsuc)
for cmd in cmdlist:
time.sleep(0.1)
#this is regex to match anything. Essentially clears the buffer so you don't get an invalid match from before
ssh.expect(['(?s).*'])
ssh.sendline(cmd)
foundind = ssh.expect([re.escape("root#")], 30) #very slow
#repr escape all the wierd stuff so madness doesn't happen with ctr chars
rettxt = repr(ssh.before.decode("us-ascii") + "root:#")
print("We Found:" + rettxt
And it will be fine for about 20 commands or so then madness occurs Assume the right echo is blablabla each time:
We found 'blablabla \r\n\r\n[edit]\r\nroot#'
We found 'blablabla \r\n\r\n[edit]\r\nroot#'
We found 'blablabla \r\n\r\n[edit]\r\nroot#'
... about 20 commands...
We found 'bl\r\nroot#' # here it just missed part of the string in the middle
We found 'alala\r\nroot#'
here is the remainder of the echo from the previous command!!! and the echo of the current command will show up some time later!! and it gets worse and worse. The thing that is strange is it is in the middle of the return byte array.
Now there are some wierd control codes coming back from this device so if I replace:
rettxt = repr(ssh.before.decode("us-ascii") + "root:#")
with
rettxt = repr(ssh.before.decode("us-ascii") + "root:#")
then
print("We Found:" + rettxt)
returns:
root#e Found lala
Anyway there is really strange stuff going on with pexpect and the buffers, and I can't figure out what it is so any help would be appreciated. I should mention I never get teh timeout, the dive always responds. Also the total number of "root:#"in the log file exceedes the total number of lines sent.
If I go through and remove all ctl codes, the output looks cleaner but the problem still persists, its as if pextect cant handle ctl coodes in its buffer correctly. Any help is appreciated
UPDATE Minimum verifiable example
Ok I have been able to recreate PART of the problem on an isolated ubuntu environment sshing into itself.
first I need to create 4 commands that can be run on a host target, so put the follwing for files in ~/ I did this in ubuntu
~/check.py
#!/usr/bin/python3
import time
import io
#abcd^H^H^H^H^MABC
#mybytes = b'\x61\x62\x63\x64\x08\x08\x08\x0D\x41\x42\x43'
#abcdACB
mybytes = b'\x61\x62\x63\x64\x41\x42\x43'
f = open('test.txt', 'wb')
#time.sleep(1)
f.write(mybytes)
print(mybytes.decode('ascii'))
f.close()
~/check2.py
#!/usr/bin/python3
import time
import io
#0123^H^H^H^H^MABC
mybytes = b'\x30\x31\x32\x33\x08\x0D\x0D\x08\x08\x08\x08\x0D\x41\x42\x43'
f = open('test2.txt', 'wb')
#time.sleep(0.1)
f.write(mybytes)
print(mybytes.decode('ascii'))
f.close()
~/check3.py
#!/usr/bin/python3
import time
import io
#789:^H^H^H^H^DABC
mybytes = b'\x37\x38\x39\x3A\x08\x08\x08\x08\x08\x08\x08\x0D\x0D\x41\x42\x43'
f = open('test3.txt', 'wb')
#time.sleep(0.1)
f.write(mybytes)
print(mybytes.decode('ascii'))
f.close()
And lastly check4.py Sorry it took a wierd combination for the problem to show back up
#!/usr/bin/python3
import time
import io
#abcd^H^H^H^HABC
mybytes = b'\x61\x62\x63\x64\x08\x08\x08\x0D\x41\x42\x43'
f = open('test.txt', 'wb')
time.sleep(4)
f.write(mybytes)
print(mybytes.decode('ascii'))
f.close()
Noticing that the last one has a bigger sleep, this is to encounter texpect timeout. Though on my actual testing this doesn't occue, I have commands that take over 6 minutes to return any text so this might be part of it. Ok and the final file to run everything. It might look ugly but I did a massive trim so I could post it here:
#! /usr/bin/python3
#import paramiko
import time
import sys
import xml.etree.ElementTree as ET
import xml
import os.path
import traceback
import re
import datetime
import pexpect
import os
import os.path
ssh = None
respFile = None
#Error Codes:
DEBUG = True
NO_ERROR=0
EXCEPTION_THROWS=1
RETURN_TEXT_NEVER_FOUND = 2
LOG_CONSOLE = 1
LOG_FILE = 2
LOG_BOTH = 3
def log(out, dummy=None):
print(str(log))
def connect(user, addr, passwd):
global ssh
fout = open('session.log', 'wb')
#options = '-q -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null -oPubkeyAuthentication=no'
options = ' -oUserKnownHostsFile=/dev/null '
#options = ''
#REPLACE WITH YOU LOCAL USER NAME
#user = 'user'
#REPLACE WITH YOUR LOCAL PASSWORD
#passwd = '123TesT321'
#addr = '127.0.0.1'
ssh_cmd = 'ssh %s#%s %s' % (user, addr, options)
public = None
private = None
retval = 0
try:
ssh = pexpect.spawn(ssh_cmd, timeout=60)
ssh.logfile = fout
#the most common prompts
loginsuccess = [re.escape("#"), re.escape("$")]
lgsuc = ['(?i)(password)', re.escape("connecting (yes/no)? ")]
for item in loginsuccess:
lgsuc.append(item)
retval = ssh.expect(lgsuc)
except pexpect.TIMEOUT as exc:
log("Server never connected to SSH tunnel")
return 0
print('where here ret val = ' + str(retval))
try:
if(retval > 1):
return 1
elif(retval == 1):
hostkey = ssh.before.decode("utf-8")
ssh.sendline("yes")
log("Warning! new host key was added to the database: " + hostkey.split("\n")[1])
lgsuc = ['password: ']
for item in loginsuccess:
lgsuc.append(item)
retval = ssh.expect(lgsuc)
if(retval > 0):
return 1
else:
if(public is not None):
log("Warning public key authentication failed trying password if available...")
else:
if public is not None:
log("Warning public key authentication failed trying password if available...")
if(passwd is None):
log("No password and certificate authentication failed...")
return 0
ssh.sendline(passwd)
login = ['password: ' ]
for item in loginsuccess:
login.append(item)
retval = ssh.expect(login)
except pexpect.TIMEOUT as exc:
log("Server Never responded with expected login prompt: "+lgstr)
return 0
#return 0
if retval > 0:
retval = 1
if retval == 0:
log("Failed to connect to IP:"+addr +" User:"+user+" Password:"+passwd)
return retval
def disconnect():
log("Disconnecting...")
global ssh
if ssh is not None:
ssh.close()
else:
log("Something wierd happened with the SSH client while closing the session. Shouldn't really matter", False)
def RunCommand(cmd, waitTXT, timeout = 5):
global ssh
Error = 0
if DEBUG:
print('Debugging: cmd: '+ cmd+'. timeout: '+str(timeout) +'. len of txt tags: '+ str(len(waitTXT)))
if(type(waitTXT) is str):
waitTXT = [re.excape(waitTXT)]
elif(not hasattr(waitTXT ,'__iter__')):
waitTXT = [re.escape(str(waitTXT))]
else:
cnter = 0
for TXT in waitTXT:
waitTXT[cnter] = re.escape(str(TXT))
cnter +=1
#start = time.time()
#print("type3: "+str(type(ssh)))
#time.sleep(1)
#this is regex to match anything. Essentially clears the buffer so you don't get an invalid match from before
ssh.expect(['(?s).*'])
ssh.sendline(cmd)
print("Debugging: sent: "+cmd)
#GoOn = True
rettxt = ""
try:
foundind = ssh.expect(waitTXT, timeout)
allbytes = ssh.before
newbytes = bytearray()
for onebyte in allbytes:
if onebyte > 31:
newbytes.append(onebyte)
allbytes = bytes(newbytes)
rettxt = repr(allbytes.decode("us-ascii") + waitTXT[foundind])
#rettxt = ssh.before + waitTXT[foundind]
if DEBUG:
print("Debugging: We found "+rettxt)
except pexpect.TIMEOUT as exc:
if DEBUG:
txtret = ""
for strtxt in waitTXT:
txtret += strtxt +", "
print("ERROR Debugging: we timed out waiting for text:"+txtret)
pass
return (rettxt, Error)
def CloseAndExit():
disconnect()
global respFile
if respFile is not None and '_io.TextIOWrapper' in str(type(respFile)):
if not respFile.closed:
respFile.close()
def main(argv):
try:
cmds = ['~/check.py', '~/check2.py', '~/check3.py', '~/check2.py', '~/check3.py','~/check.py', '~/check2.py', '~/check3.py', '~/check2.py', '~/check3.py', '~/check4.py', '~/check3.py','~/check.py', '~/check2.py',]
##CHANGE THESE TO MTACH YOUR SSH HOST
ret = connect('user', '127.0.0.1', 'abcd1234')
for cmd in cmds:
cmdtxt = str(cmd)
#rett = RunCommand(ssh, "ls", "root", 0, 5)
strlen = (170 - (len(cmdtxt)))/2
dashval = ''
starval = ''
tcnt = 0
while(tcnt < strlen):
dashval +='-'
starval +='*'
tcnt +=1
if DEBUG:
print(dashval+cmdtxt+dashval)
#checkval = ['ABC']
#REPLACE THE FOLLOWING LINE WITH YOUR TARGET PROMPT
checkval = ['user-virtual-machine:~$']
rett = RunCommand(cmdtxt, checkval, 2)
if DEBUG:
print(starval+cmdtxt+starval)
except Exception as e:
exc_type, exc_obj, exc_tb = sys.exc_info()
fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
print(exc_type, fname, exc_tb.tb_lineno)
print(traceback.format_exc())
CloseAndExit()
#disconnect()
#respFile.close()
main(sys.argv)
Make sure that all for checks and the main python script are executble in permission via sudo chmod 774 or similar. In the main function call set your username ipaddress and password to where your target is that has the check.py and make sure they are in your ~/ directory.
Once you run this you can look at the session.log and at least on mind there is some wierd stuff going on with the buffer:
~/check4.py^M
~/check3.py
~/check3.py^M
abcd^H^H^H^MABC^M
^[]0;user#user-virtual-machine: ~^Guser#user-virtual-machine:~$ ~/check.py
~/check3.py^M
789:^H^H^H^H^H^H^H^M^MABC^M
^[]0;user#user-virtual-machine: ~^Guser#user-virtual-machine:~$ ~/check.py~/check2.py
And unfortunately its not as corrupt as my actual prbolem but I have several hundred commands I an embedded custom linux kernal that I obviously can't recreate for everyone. But anyway any help is greatly appreciated. Hopefully these examples work you you, I am just on ubuntu 16.04 lts. Also make sure to replace 'user-virtual-machine:~$' with whatever your target login prompt looks like